Update missed package status file.

* Fix missing id on function_call_output in Foundry Hosting

The Foundry storage layer was rejecting responses with
"ID cannot be null or empty (Parameter 'id')" because
function_call_output items emitted by OutputConverter had no id on
the wire.

OutputItemFunctionToolCallOutput's public ctor only sets CallId and
Output; Id is read-only and only the SDK's internal ctor populates
it. OutputItemBuilder<T>.ApplyAutoStamps fills ResponseId and
AgentReference but not Id, so the itemId passed to
AddOutputItem<T>(itemId) was used only for event sequencing and the
serialized item went out with id=null.

Switch to stream.OutputItemFunctionCallOutput(callId, output), the
SDK convenience method that uses the internal ctor and stamps the
id. Add a regression test asserting the added/done events carry a
non-empty matching Id.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* ci: free disk space and relocate NuGet cache on ubuntu runners

The ubuntu-latest dotnet-build/test jobs were hitting No space left on device because the runner image only ships ~14 GB free on /. The full multi-TFM build plus the dotnet pack + console-app install-check exhausts that easily.

Add a reusable composite action .github/actions/free-runner-disk-space that runs on Linux runners only and:

* removes pre-installed toolchains we never use here (Android SDK, GHC/Haskell, CodeQL, PyPy, Ruby, Go, boost, vcpkg, etc.), prunes docker images, and disables swap (reclaims ~25-30 GB on /)

* relocates the NuGet package cache to /mnt/nuget via NUGET_PACKAGES env, since /mnt has ~75 GB free on hosted runners

Wire the action into the four ubuntu-touching jobs in dotnet-build-and-test.yml (dotnet-build, dotnet-test, dotnet-foundry-hosted-it, dotnet-test-functions). The action self-guards with runner.os == 'Linux' so the matrix legs that run on windows are unaffected.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: alliscode <25218250+alliscode@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/actions/free-runner-disk-space/action.yml

@@ -0,0 +1,64 @@
+name: Free runner disk space
+description: |
+  Reclaims disk space on GitHub-hosted Ubuntu runners by removing
+  pre-installed toolchains we do not use (Android SDK, GHC/Haskell,
+  CodeQL bundle), Docker images, and swap. Also relocates the
+  NuGet package cache to /mnt (which has ~75 GB free vs ~14 GB
+  on /). No-op on non-Linux runners.
+
+runs:
+  using: composite
+  steps:
+    - name: Free disk space (Linux only)
+      if: runner.os == 'Linux'
+      shell: bash
+      run: |
+        set -euo pipefail
+        echo "::group::Disk usage before cleanup"
+        df -h /
+        echo "::endgroup::"
+
+        # Remove pre-installed toolchains we never use on this repo's
+        # dotnet/python jobs. These reclaim ~25-30 GB on ubuntu-latest.
+        sudo rm -rf \
+          /usr/local/lib/android \
+          /usr/share/dotnet/sdk/NuGetFallbackFolder \
+          /opt/ghc \
+          /usr/local/.ghcup \
+          /opt/hostedtoolcache/CodeQL \
+          /opt/hostedtoolcache/PyPy \
+          /opt/hostedtoolcache/Ruby \
+          /opt/hostedtoolcache/go \
+          /usr/local/share/boost \
+          /usr/local/share/powershell \
+          /usr/local/share/chromium \
+          /usr/local/share/vcpkg \
+          /usr/local/lib/heroku \
+          "${AGENT_TOOLSDIRECTORY:-/opt/hostedtoolcache}/PyPy" \
+          "${AGENT_TOOLSDIRECTORY:-/opt/hostedtoolcache}/Ruby" \
+          "${AGENT_TOOLSDIRECTORY:-/opt/hostedtoolcache}/go" || true
+
+        # Drop docker images shipped on the runner; jobs that need
+        # docker pull what they need fresh.
+        if command -v docker >/dev/null 2>&1; then
+          sudo docker image prune --all --force >/dev/null 2>&1 || true
+        fi
+
+        # Disable swap to free its backing file.
+        sudo swapoff -a || true
+        sudo rm -f /mnt/swapfile /swapfile || true
+
+        echo "::group::Disk usage after cleanup"
+        df -h /
+        echo "::endgroup::"
+
+    - name: Relocate NuGet package cache to /mnt (Linux only)
+      if: runner.os == 'Linux'
+      shell: bash
+      run: |
+        set -euo pipefail
+        sudo mkdir -p /mnt/nuget
+        sudo chown -R "$USER":"$USER" /mnt/nuget
+        echo "NUGET_PACKAGES=/mnt/nuget" >> "$GITHUB_ENV"
+        echo "Relocated NuGet package cache to /mnt/nuget"
+        df -h /mnt || true

.github/scripts/pr_limit_moderation.js

@@ -0,0 +1,163 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+function getPullRequest(context) {
+  const pullRequest = context.payload.pull_request;
+  if (!pullRequest?.number || !pullRequest.user?.login) {
+    throw new Error('This script must be run from a pull_request_target event.');
+  }
+
+  return {
+    author: pullRequest.user.login,
+    labels: pullRequest.labels?.map((label) => label.name).filter(Boolean) ?? [],
+    number: pullRequest.number,
+  };
+}
+
+async function ensureLabel({ github, owner, repo, labelName }) {
+  try {
+    await github.rest.issues.getLabel({
+      owner,
+      repo,
+      name: labelName,
+    });
+  } catch (error) {
+    if (error.status !== 404) {
+      throw error;
+    }
+
+    try {
+      await github.rest.issues.createLabel({
+        owner,
+        repo,
+        name: labelName,
+        color: 'd93f0b',
+        description: 'Community author has exceeded the open pull request limit.',
+      });
+    } catch (createError) {
+      if (createError.status !== 422) {
+        throw createError;
+      }
+    }
+  }
+}
+
+function hasLabel(labels, labelName) {
+  if (!labelName) {
+    return false;
+  }
+
+  return labels.some((label) => label.toLowerCase() === labelName.toLowerCase());
+}
+
+function buildLimitMessage({ author, exemptLabelName, maxOpenPrs, openPrCount }) {
+  return [
+    `Thank you for your contribution, @${author}.`,
+    '',
+    `To keep the review queue manageable, we currently limit community contributors to ${maxOpenPrs} `
+      + `open pull requests at a time. This PR would put you at ${openPrCount} open pull requests, `
+      + 'so we are closing it automatically.',
+    '',
+    'Please focus on getting your existing PRs reviewed, merged, or closed before opening another one. '
+      + `If a maintainer asked you to open this PR, they can apply the \`${exemptLabelName}\` label and reopen it.`,
+  ].join('\n');
+}
+
+async function getOpenPrCount({ github, owner, repo, author, pullRequestNumber }) {
+  const query = `repo:${owner}/${repo} is:pr is:open author:${author}`;
+  const response = await github.rest.search.issuesAndPullRequests({
+    q: query,
+    per_page: 100,
+  });
+
+  const indexedPrNumbers = response.data.items.map((item) => item.number);
+  const currentPrIsIndexed = indexedPrNumbers.includes(pullRequestNumber);
+  if (currentPrIsIndexed || response.data.total_count >= 100) {
+    return response.data.total_count;
+  }
+
+  return response.data.total_count + 1;
+}
+
+async function enforcePrLimit({ github, context, core, exemptLabelName, maxOpenPrs, labelName }) {
+  const { owner, repo } = context.repo;
+  const { author, labels, number } = getPullRequest(context);
+
+  if (hasLabel(labels, exemptLabelName)) {
+    core.info(`PR #${number} has the ${exemptLabelName} label; skipping open PR limit enforcement.`);
+    return {
+      author,
+      closed: false,
+      exempt: true,
+      openPrCount: null,
+    };
+  }
+
+  const openPrCount = await getOpenPrCount({
+    github,
+    owner,
+    repo,
+    author,
+    pullRequestNumber: number,
+  });
+
+  if (openPrCount <= maxOpenPrs) {
+    core.info(
+      `${author} has ${openPrCount} open pull request(s), which is within the limit of ${maxOpenPrs}.`,
+    );
+    return {
+      author,
+      closed: false,
+      openPrCount,
+    };
+  }
+
+  await ensureLabel({
+    github,
+    owner,
+    repo,
+    labelName,
+  });
+
+  await github.rest.issues.addLabels({
+    owner,
+    repo,
+    issue_number: number,
+    labels: [labelName],
+  });
+
+  await github.rest.issues.createComment({
+    owner,
+    repo,
+    issue_number: number,
+    body: buildLimitMessage({
+      author,
+      exemptLabelName,
+      maxOpenPrs,
+      openPrCount,
+    }),
+  });
+
+  await github.rest.pulls.update({
+    owner,
+    repo,
+    pull_number: number,
+    state: 'closed',
+  });
+
+  core.info(
+    `${author} has ${openPrCount} open pull request(s), which exceeds the limit of ${maxOpenPrs}. `
+      + `Closed PR #${number}.`,
+  );
+
+  return {
+    author,
+    closed: true,
+    openPrCount,
+  };
+}
+
+module.exports = {
+  buildLimitMessage,
+  enforcePrLimit,
+  getOpenPrCount,
+};

.github/tests/test_pr_limit_moderation.js

@@ -0,0 +1,286 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+/**
+ * Tests for pr_limit_moderation.js.
+ *
+ * Run with: node --test .github/tests/test_pr_limit_moderation.js
+ */
+
+const { describe, it } = require('node:test');
+const assert = require('node:assert/strict');
+
+const { enforcePrLimit } = require('../scripts/pr_limit_moderation.js');
+
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+function createContext({ author = 'community-user', labels = [], number = 123 } = {}) {
+  return {
+    repo: {
+      owner: 'microsoft',
+      repo: 'agent-framework',
+    },
+    payload: {
+      pull_request: {
+        number,
+        labels: labels.map((name) => ({ name })),
+        user: {
+          login: author,
+        },
+      },
+    },
+  };
+}
+
+function createCore() {
+  const messages = [];
+  return {
+    messages,
+    info(message) {
+      messages.push(message);
+    },
+  };
+}
+
+function createGithub({ totalCount, itemNumbers, labelExists = true }) {
+  const calls = [];
+
+  return {
+    calls,
+    rest: {
+      search: {
+        async issuesAndPullRequests(params) {
+          calls.push({ api: 'search.issuesAndPullRequests', params });
+          return {
+            data: {
+              total_count: totalCount,
+              items: itemNumbers.map((number) => ({ number })),
+            },
+          };
+        },
+      },
+      issues: {
+        async getLabel(params) {
+          calls.push({ api: 'issues.getLabel', params });
+          if (!labelExists) {
+            const error = new Error('Not Found');
+            error.status = 404;
+            throw error;
+          }
+          return { data: { name: params.name } };
+        },
+        async createLabel(params) {
+          calls.push({ api: 'issues.createLabel', params });
+          return { data: { name: params.name } };
+        },
+        async addLabels(params) {
+          calls.push({ api: 'issues.addLabels', params });
+          return { data: [] };
+        },
+        async createComment(params) {
+          calls.push({ api: 'issues.createComment', params });
+          return { data: { id: 1 } };
+        },
+      },
+      pulls: {
+        async update(params) {
+          calls.push({ api: 'pulls.update', params });
+          return { data: { state: params.state } };
+        },
+      },
+    },
+  };
+}
+
+
+// ---------------------------------------------------------------------------
+// PR limit enforcement
+// ---------------------------------------------------------------------------
+
+describe('PR limit enforcement', () => {
+  it('does not close the PR when the author is at the open PR limit', async () => {
+    const github = createGithub({
+      totalCount: 10,
+      itemNumbers: [1, 2, 3, 4, 5, 6, 7, 8, 9, 123],
+    });
+
+    const result = await enforcePrLimit({
+      github,
+      context: createContext(),
+      core: createCore(),
+      exemptLabelName: 'pr-limit-exempt',
+      maxOpenPrs: 10,
+      labelName: 'too-many-prs',
+    });
+
+    assert.equal(result.closed, false);
+    assert.equal(result.openPrCount, 10);
+    assert.deepEqual(
+      github.calls.map((call) => call.api),
+      ['search.issuesAndPullRequests'],
+    );
+  });
+
+  it('counts the new PR when search has not indexed it yet', async () => {
+    const github = createGithub({
+      totalCount: 10,
+      itemNumbers: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
+    });
+
+    const result = await enforcePrLimit({
+      github,
+      context: createContext(),
+      core: createCore(),
+      exemptLabelName: 'pr-limit-exempt',
+      maxOpenPrs: 10,
+      labelName: 'too-many-prs',
+    });
+
+    assert.equal(result.closed, true);
+    assert.equal(result.openPrCount, 11);
+    assert.deepEqual(
+      github.calls.map((call) => call.api),
+      [
+        'search.issuesAndPullRequests',
+        'issues.getLabel',
+        'issues.addLabels',
+        'issues.createComment',
+        'pulls.update',
+      ],
+    );
+  });
+
+  it('creates the label when it does not already exist', async () => {
+    const github = createGithub({
+      totalCount: 11,
+      itemNumbers: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 123],
+      labelExists: false,
+    });
+
+    const result = await enforcePrLimit({
+      github,
+      context: createContext(),
+      core: createCore(),
+      exemptLabelName: 'pr-limit-exempt',
+      maxOpenPrs: 10,
+      labelName: 'too-many-prs',
+    });
+
+    assert.equal(result.closed, true);
+    assert.deepEqual(
+      github.calls.map((call) => call.api),
+      [
+        'search.issuesAndPullRequests',
+        'issues.getLabel',
+        'issues.createLabel',
+        'issues.addLabels',
+        'issues.createComment',
+        'pulls.update',
+      ],
+    );
+    assert.equal(
+      github.calls.find((call) => call.api === 'issues.createLabel').params.name,
+      'too-many-prs',
+    );
+  });
+
+  it('tolerates a 422 race when creating the label', async () => {
+    const github = createGithub({
+      totalCount: 11,
+      itemNumbers: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 123],
+      labelExists: false,
+    });
+    github.rest.issues.createLabel = async (params) => {
+      github.calls.push({ api: 'issues.createLabel', params });
+      const error = new Error('Validation Failed');
+      error.status = 422;
+      throw error;
+    };
+
+    const result = await enforcePrLimit({
+      github,
+      context: createContext(),
+      core: createCore(),
+      exemptLabelName: 'pr-limit-exempt',
+      maxOpenPrs: 10,
+      labelName: 'too-many-prs',
+    });
+
+    assert.equal(result.closed, true);
+    assert.deepEqual(
+      github.calls.map((call) => call.api),
+      [
+        'search.issuesAndPullRequests',
+        'issues.getLabel',
+        'issues.createLabel',
+        'issues.addLabels',
+        'issues.createComment',
+        'pulls.update',
+      ],
+    );
+  });
+
+  it('uses a diplomatic close message with the configured limit', async () => {
+    const github = createGithub({
+      totalCount: 11,
+      itemNumbers: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 123],
+    });
+
+    await enforcePrLimit({
+      github,
+      context: createContext({ author: 'octo-contributor' }),
+      core: createCore(),
+      exemptLabelName: 'pr-limit-exempt',
+      maxOpenPrs: 10,
+      labelName: 'too-many-prs',
+    });
+
+    const comment = github.calls.find((call) => call.api === 'issues.createComment').params.body;
+    assert.match(comment, /Thank you for your contribution/);
+    assert.match(comment, /limit community contributors to 10 open pull requests/);
+    assert.match(comment, /@octo-contributor/);
+    assert.match(comment, /`pr-limit-exempt` label and reopen/);
+  });
+
+  it('does not close an exempt PR when it is reopened', async () => {
+    const github = createGithub({
+      totalCount: 11,
+      itemNumbers: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 123],
+    });
+
+    const result = await enforcePrLimit({
+      github,
+      context: createContext({ labels: ['PR-LIMIT-EXEMPT'] }),
+      core: createCore(),
+      exemptLabelName: 'pr-limit-exempt',
+      maxOpenPrs: 10,
+      labelName: 'too-many-prs',
+    });
+
+    assert.equal(result.closed, false);
+    assert.equal(result.exempt, true);
+    assert.equal(result.openPrCount, null);
+    assert.deepEqual(github.calls, []);
+  });
+
+  it('does not over-count when the current PR is not on the first search page', async () => {
+    const github = createGithub({
+      totalCount: 101,
+      itemNumbers: Array.from({ length: 100 }, (_, index) => index + 1),
+    });
+
+    const result = await enforcePrLimit({
+      github,
+      context: createContext({ number: 123 }),
+      core: createCore(),
+      exemptLabelName: 'pr-limit-exempt',
+      maxOpenPrs: 10,
+      labelName: 'too-many-prs',
+    });
+
+    assert.equal(result.closed, true);
+    assert.equal(result.openPrCount, 101);
+  });
+});

.github/workflows/dotnet-build-and-test.yml

@@ -121,6 +121,9 @@ jobs:
               python
               declarative-agents
 
+      - name: Free runner disk space
+        uses: ./.github/actions/free-runner-disk-space
+
       - name: Setup dotnet
         uses: actions/setup-dotnet@c2fa09f4bde5ebb9d1777cf28262a3eb3db3ced7 # v5.2.0
         with:
@@ -191,6 +194,9 @@ jobs:
               python
               declarative-agents
 
+      - name: Free runner disk space
+        uses: ./.github/actions/free-runner-disk-space
+
       # Start Cosmos DB Emulator for all integration tests and only for unit tests when CosmosDB changes happened)
       - name: Start Azure Cosmos DB Emulator
         if: ${{ runner.os == 'Windows' && (needs.paths-filter.outputs.cosmosDbChanges == 'true' || (github.event_name != 'pull_request' && matrix.integration-tests)) }}
@@ -365,6 +371,9 @@ jobs:
             dotnet
             python
 
+      - name: Free runner disk space
+        uses: ./.github/actions/free-runner-disk-space
+
       - name: Setup dotnet
         uses: actions/setup-dotnet@c2fa09f4bde5ebb9d1777cf28262a3eb3db3ced7 # v5.2.0
         with:
@@ -452,6 +461,9 @@ jobs:
             python
             declarative-agents
 
+      - name: Free runner disk space
+        uses: ./.github/actions/free-runner-disk-space
+
       - name: Setup dotnet
         uses: actions/setup-dotnet@c2fa09f4bde5ebb9d1777cf28262a3eb3db3ced7 # v5.2.0
         with:

.github/workflows/limit-community-prs.yml

@@ -0,0 +1,83 @@
+name: Limit community pull requests
+
+on:
+  pull_request_target:
+    types: [opened, reopened]
+
+permissions:
+  contents: read
+  issues: write
+  pull-requests: write
+
+concurrency:
+  group: pr-limit-${{ github.repository }}-${{ github.event.pull_request.user.login }}
+  cancel-in-progress: false
+
+env:
+  MAX_OPEN_PULL_REQUESTS: '10'
+  PR_LIMIT_EXEMPT_LABEL: pr-limit-exempt
+  TOO_MANY_PRS_LABEL: too-many-prs
+
+jobs:
+  team_check:
+    runs-on: ubuntu-latest
+    outputs:
+      is_team_member: ${{ steps.check.outputs.is_team_member }}
+    steps:
+      - name: Checkout scripts
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        with:
+          sparse-checkout: .github/scripts
+          fetch-depth: 1
+          persist-credentials: false
+
+      - name: Check PR author team membership
+        id: check
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8
+        env:
+          TEAM_NAME: ${{ secrets.DEVELOPER_TEAM }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+        with:
+          github-token: ${{ secrets.GH_ACTIONS_PR_WRITE }}
+          script: |
+            const checkTeamMembership = require('./.github/scripts/check_team_membership.js');
+            const { author, isTeamMember } = await checkTeamMembership({
+              github,
+              context,
+              core,
+              teamSlug: process.env.TEAM_NAME,
+              issueNumber: process.env.PR_NUMBER,
+            });
+            core.setOutput('is_team_member', isTeamMember ? 'true' : 'false');
+            if (isTeamMember) {
+              core.info(`Author ${author} is a team member; skipping open PR limit.`);
+            } else {
+              core.info(`Author ${author} is not a team member; checking open PR limit.`);
+            }
+
+  limit_open_prs:
+    runs-on: ubuntu-latest
+    needs: team_check
+    if: ${{ needs.team_check.outputs.is_team_member == 'false' }}
+    steps:
+      - name: Checkout scripts
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        with:
+          sparse-checkout: .github/scripts
+          fetch-depth: 1
+          persist-credentials: false
+
+      - name: Enforce open PR limit
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8
+        with:
+          github-token: ${{ secrets.GH_ACTIONS_PR_WRITE }}
+          script: |
+            const { enforcePrLimit } = require('./.github/scripts/pr_limit_moderation.js');
+            await enforcePrLimit({
+              github,
+              context,
+              core,
+              exemptLabelName: process.env.PR_LIMIT_EXEMPT_LABEL,
+              maxOpenPrs: Number.parseInt(process.env.MAX_OPEN_PULL_REQUESTS, 10),
+              labelName: process.env.TOO_MANY_PRS_LABEL,
+            });

.github/workflows/markdown-link-check.yml

@@ -23,6 +23,14 @@ jobs:
         with:
           persist-credentials: false
 
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Install Chrome for Puppeteer
+        run: npx puppeteer browsers install chrome
+
       # Checks the status of hyperlinks in all files
       - name: Run linkspector
         uses: umbrelladocs/action-linkspector@963b6264d7de32c904942a70b488d3407453049e # v1

dotnet/Directory.Packages.props

@@ -22,14 +22,14 @@
     <PackageVersion Include="Aspire.Microsoft.Azure.Cosmos" Version="$(AspireAppHostSdkVersion)" />
     <PackageVersion Include="CommunityToolkit.Aspire.OllamaSharp" Version="13.0.0" />
     <!-- Azure.* -->
-    <PackageVersion Include="Azure.AI.AgentServer.Core" Version="1.0.0-beta.23" />
-    <PackageVersion Include="Azure.AI.AgentServer.Invocations" Version="1.0.0-beta.3" />
-    <PackageVersion Include="Azure.AI.AgentServer.Responses" Version="1.0.0-beta.4" />
+    <PackageVersion Include="Azure.AI.AgentServer.Core" Version="1.0.0-beta.25" />
+    <PackageVersion Include="Azure.AI.AgentServer.Invocations" Version="1.0.0-beta.4" />
+    <PackageVersion Include="Azure.AI.AgentServer.Responses" Version="1.0.0-beta.5" />
     <PackageVersion Include="Azure.Search.Documents" Version="12.0.0" />
     <PackageVersion Include="Azure.AI.Projects" Version="2.1.0-beta.2" />
     <PackageVersion Include="Azure.AI.Agents.Persistent" Version="1.2.0-beta.10" />
     <PackageVersion Include="Azure.AI.OpenAI" Version="2.9.0-beta.1" />
-    <PackageVersion Include="Azure.Core" Version="1.55.0" />
+    <PackageVersion Include="Azure.Core" Version="1.56.0" />
     <PackageVersion Include="Azure.Identity" Version="1.21.0" />
     <PackageVersion Include="DotNetEnv" Version="3.1.1" />
     <PackageVersion Include="Azure.Monitor.OpenTelemetry.Exporter" Version="1.5.0" />
@@ -44,7 +44,7 @@
     <PackageVersion Include="Microsoft.Bcl.AsyncInterfaces" Version="10.0.6" />
     <PackageVersion Include="Microsoft.Bcl.HashCode" Version="6.0.0" />
     <PackageVersion Include="Microsoft.Bcl.Memory" Version="10.0.5" />
-    <PackageVersion Include="System.ClientModel" Version="1.11.0" />
+    <PackageVersion Include="System.ClientModel" Version="1.12.0" />
     <PackageVersion Include="System.CodeDom" Version="10.0.0" />
     <PackageVersion Include="System.Collections.Immutable" Version="10.0.1" />
     <PackageVersion Include="System.CommandLine" Version="2.0.0-rc.2.25502.107" />

dotnet/samples/04-hosting/FoundryHostedAgents/responses/Using-Samples/SessionFilesClient/SessionFilesClient.csproj

@@ -13,8 +13,10 @@
 
   <ItemGroup>
     <PackageReference Include="Azure.AI.Projects" />
+    <PackageReference Include="Azure.Core" />
     <PackageReference Include="Azure.Identity" />
     <PackageReference Include="DotNetEnv" />
+    <PackageReference Include="System.ClientModel" />
   </ItemGroup>
 
   <ItemGroup>

dotnet/samples/04-hosting/FoundryHostedAgents/responses/Using-Samples/SimpleAgent/SimpleAgent.csproj

@@ -13,8 +13,10 @@
 
   <ItemGroup>
     <PackageReference Include="Azure.AI.Projects" />
+    <PackageReference Include="Azure.Core" />
     <PackageReference Include="Azure.Identity" />
     <PackageReference Include="DotNetEnv" />
+    <PackageReference Include="System.ClientModel" />
   </ItemGroup>
 
   <ItemGroup>

dotnet/src/Microsoft.Agents.AI.Abstractions/AgentResponse.cs

@@ -297,7 +297,7 @@ public class AgentResponse
                 AgentId = this.AgentId,
                 ResponseId = this.ResponseId,
                 MessageId = message.MessageId,
-                CreatedAt = this.CreatedAt,
+                CreatedAt = message.CreatedAt ?? this.CreatedAt,
             };
         }
 

dotnet/src/Microsoft.Agents.AI.Foundry.Hosting/OutputConverter.cs

@@ -281,14 +281,19 @@ internal static class OutputConverter
 
                         var outputText = EncodeFunctionResultAsJsonStringPayload(functionResult.Result);
 
-                        var itemId = GenerateItemId("fc");
-                        var outputItem = new OutputItemFunctionToolCallOutput(
+                        // Use the SDK's convenience method so the OutputItemFunctionToolCallOutput
+                        // is constructed with a populated Id. The public OutputItemFunctionToolCallOutput
+                        // ctor only sets CallId/Output (Id is read-only), and AddOutputItem<T>+EmitAdded
+                        // does not auto-stamp Id — only ResponseId/AgentReference. Without this, the
+                        // serialized item arrives at the Foundry storage layer with id=null and is
+                        // rejected with "ID cannot be null or empty (Parameter 'id')".
+                        foreach (var evt in stream.OutputItemFunctionCallOutput(
                             functionResult.CallId,
-                            BinaryData.FromString(outputText));
+                            BinaryData.FromString(outputText)))
+                        {
+                            yield return evt;
+                        }
 
-                        var outputBuilder = stream.AddOutputItem<OutputItemFunctionToolCallOutput>(itemId);
-                        yield return outputBuilder.EmitAdded(outputItem);
-                        yield return outputBuilder.EmitDone(outputItem);
                         break;
                     }
 

dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/InvokeMcpToolExecutor.cs

@@ -75,18 +75,14 @@ internal sealed class InvokeMcpToolExecutor(
 
         if (requireApproval)
         {
-            // Create tool call content for approval request
+            // Create tool call content for approval request.
+            // Transport headers (e.g. Authorization) are intentionally excluded from the
+            // approval event: they must not cross into the externally-surfaced approval request.
             McpServerToolCallContent toolCall = new(this.Id, toolName, serverLabel ?? serverUrl)
             {
                 Arguments = arguments
             };
 
-            if (headers != null)
-            {
-                toolCall.AdditionalProperties ??= [];
-                toolCall.AdditionalProperties.Add(headers);
-            }
-
             ToolApprovalRequestContent approvalRequest = new(this.Id, toolCall);
 
             ChatMessage requestMessage = new(ChatRole.Assistant, [approvalRequest]);

dotnet/src/Microsoft.Agents.AI.Workflows/AgentResponseEvent.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System.Collections.Generic;
 using Microsoft.Shared.Diagnostics;
 
 namespace Microsoft.Agents.AI.Workflows;
@@ -19,6 +20,28 @@ public sealed class AgentResponseEvent : WorkflowOutputEvent
         this.Response = Throw.IfNull(response);
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AgentResponseEvent"/> class with the given output tag.
+    /// </summary>
+    /// <param name="executorId">The identifier of the executor that generated this event.</param>
+    /// <param name="response">The agent response.</param>
+    /// <param name="tag">The output tag to associate with this event.</param>
+    public AgentResponseEvent(string executorId, AgentResponse response, OutputTag tag) : base(response, executorId, tag)
+    {
+        this.Response = Throw.IfNull(response);
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AgentResponseEvent"/> class with the given output tags.
+    /// </summary>
+    /// <param name="executorId">The identifier of the executor that generated this event.</param>
+    /// <param name="response">The agent response.</param>
+    /// <param name="tags">The output tags to associate with this event. May be <see langword="null"/> or empty.</param>
+    public AgentResponseEvent(string executorId, AgentResponse response, IEnumerable<OutputTag>? tags) : base(response, executorId, tags)
+    {
+        this.Response = Throw.IfNull(response);
+    }
+
     /// <summary>
     /// Gets the agent response.
     /// </summary>

dotnet/src/Microsoft.Agents.AI.Workflows/AgentResponseUpdateEvent.cs

@@ -20,6 +20,28 @@ public sealed class AgentResponseUpdateEvent : WorkflowOutputEvent
         this.Update = Throw.IfNull(update);
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AgentResponseUpdateEvent"/> class with the given output tag.
+    /// </summary>
+    /// <param name="executorId">The identifier of the executor that generated this event.</param>
+    /// <param name="update">The agent run response update.</param>
+    /// <param name="tag">The output tag to associate with this event.</param>
+    public AgentResponseUpdateEvent(string executorId, AgentResponseUpdate update, OutputTag tag) : base(update, executorId, tag)
+    {
+        this.Update = Throw.IfNull(update);
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AgentResponseUpdateEvent"/> class with the given output tags.
+    /// </summary>
+    /// <param name="executorId">The identifier of the executor that generated this event.</param>
+    /// <param name="update">The agent run response update.</param>
+    /// <param name="tags">The output tags to associate with this event. May be <see langword="null"/> or empty.</param>
+    public AgentResponseUpdateEvent(string executorId, AgentResponseUpdate update, IEnumerable<OutputTag>? tags) : base(update, executorId, tags)
+    {
+        this.Update = Throw.IfNull(update);
+    }
+
     /// <summary>
     /// Gets the agent run response update.
     /// </summary>

dotnet/src/Microsoft.Agents.AI.Workflows/AgentWorkflowBuilder.cs

@@ -2,10 +2,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
-using System.Linq;
-using System.Threading.Tasks;
-using Microsoft.Agents.AI.Workflows.Specialized;
 using Microsoft.Extensions.AI;
 using Microsoft.Shared.Diagnostics;
 
@@ -37,31 +33,10 @@ public static partial class AgentWorkflowBuilder
     {
         Throw.IfNullOrEmpty(agents);
 
-        // Create a builder that chains the agents together in sequence. The workflow simply begins
-        // with the first agent in the sequence.
-
-        AIAgentHostOptions options = new()
-        {
-            ReassignOtherAgentsAsUsers = true,
-            ForwardIncomingMessages = true,
-        };
-
-        List<ExecutorBinding> agentExecutors = agents.Select(agent => agent.BindAsExecutor(options)).ToList();
-
-        ExecutorBinding previous = agentExecutors[0];
-        WorkflowBuilder builder = new(previous);
-
-        foreach (ExecutorBinding next in agentExecutors.Skip(1))
-        {
-            builder.AddEdge(previous, next);
-            previous = next;
-        }
-
-        OutputMessagesExecutor end = new();
-        builder = builder.AddEdge(previous, end).WithOutputFrom(end);
+        SequentialWorkflowBuilder builder = new(agents);
         if (workflowName is not null)
         {
-            builder = builder.WithName(workflowName);
+            builder.WithName(workflowName);
         }
         return builder.Build();
     }
@@ -107,41 +82,14 @@ public static partial class AgentWorkflowBuilder
     {
         Throw.IfNull(agents);
 
-        // A workflow needs a starting executor, so we create one that forwards everything to each agent.
-        ChatForwardingExecutor start = new("Start");
-        WorkflowBuilder builder = new(start);
-
-        // For each agent, we create an executor to host it and an accumulator to batch up its output messages,
-        // so that the final accumulator receives a single list of messages from each agent. Otherwise, the
-        // accumulator would not be able to determine what came from what agent, as there's currently no
-        // provenance tracking exposed in the workflow context passed to a handler.
-
-        ExecutorBinding[] agentExecutors = (from agent in agents
-                                            select agent.BindAsExecutor(new AIAgentHostOptions() { ReassignOtherAgentsAsUsers = true })).ToArray();
-        ExecutorBinding[] accumulators = [.. from agent in agentExecutors select (ExecutorBinding)new AggregateTurnMessagesExecutor($"Batcher/{agent.Id}")];
-        builder.AddFanOutEdge(start, agentExecutors);
-
-        for (int i = 0; i < agentExecutors.Length; i++)
-        {
-            builder.AddEdge(agentExecutors[i], accumulators[i]);
-        }
-
-        // Create the accumulating executor that will gather the results from each agent, and connect
-        // each agent's accumulator to it. If no aggregation function was provided, we default to returning
-        // the last message from each agent
-        aggregator ??= static lists => (from list in lists where list.Count > 0 select list.Last()).ToList();
-
-        Func<string, string, ValueTask<ConcurrentEndExecutor>> endFactory =
-            (_, __) => new(new ConcurrentEndExecutor(agentExecutors.Length, aggregator));
-
-        ExecutorBinding end = endFactory.BindExecutor(ConcurrentEndExecutor.ExecutorId);
-
-        builder.AddFanInBarrierEdge(accumulators, end);
-
-        builder = builder.WithOutputFrom(end);
+        ConcurrentWorkflowBuilder builder = new(agents);
         if (workflowName is not null)
         {
-            builder = builder.WithName(workflowName);
+            builder.WithName(workflowName);
+        }
+        if (aggregator is not null)
+        {
+            builder.WithAggregator(aggregator);
         }
         return builder.Build();
     }
@@ -155,7 +103,6 @@ public static partial class AgentWorkflowBuilder
     /// The <see cref="AIAgent"/> must be capable of understanding those <see cref="AgentRunOptions"/> provided. If the agent
     /// ignores the tools or is otherwise unable to advertize them to the underlying provider, handoffs will not occur.
     /// </remarks>
-    [Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
     public static HandoffWorkflowBuilder CreateHandoffBuilderWith(AIAgent initialAgent)
     {
         Throw.IfNull(initialAgent);
@@ -179,4 +126,31 @@ public static partial class AgentWorkflowBuilder
         Throw.IfNull(managerFactory);
         return new GroupChatWorkflowBuilder(managerFactory);
     }
+
+    /// <summary>Creates a new <see cref="SequentialWorkflowBuilder"/> with the given pipeline of <paramref name="agents"/>.</summary>
+    /// <param name="agents">The sequence of agents to compose into a sequential workflow.</param>
+    /// <returns>The builder for creating a sequential workflow.</returns>
+    public static SequentialWorkflowBuilder CreateSequentialBuilderWith(params IEnumerable<AIAgent> agents)
+    {
+        Throw.IfNull(agents);
+        return new SequentialWorkflowBuilder(agents);
+    }
+
+    /// <summary>Creates a new <see cref="ConcurrentWorkflowBuilder"/> with the given participating <paramref name="agents"/>.</summary>
+    /// <param name="agents">The set of agents to compose into a concurrent workflow.</param>
+    /// <returns>The builder for creating a concurrent workflow.</returns>
+    public static ConcurrentWorkflowBuilder CreateConcurrentBuilderWith(params IEnumerable<AIAgent> agents)
+    {
+        Throw.IfNull(agents);
+        return new ConcurrentWorkflowBuilder(agents);
+    }
+
+    /// <summary>Creates a new <see cref="MagenticWorkflowBuilder"/> with the given <paramref name="managerAgent"/>.</summary>
+    /// <param name="managerAgent">The LLM-powered manager agent that coordinates the team.</param>
+    /// <returns>The builder for creating a Magentic workflow.</returns>
+    public static MagenticWorkflowBuilder CreateMagenticBuilderWith(AIAgent managerAgent)
+    {
+        Throw.IfNull(managerAgent);
+        return new MagenticWorkflowBuilder(managerAgent);
+    }
 }

dotnet/src/Microsoft.Agents.AI.Workflows/Checkpointing/WorkflowInfo.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text.Json.Serialization;
@@ -15,14 +16,14 @@ internal sealed class WorkflowInfo
         Dictionary<string, List<EdgeInfo>> edges,
         HashSet<RequestPortInfo> requestPorts,
         string startExecutorId,
-        HashSet<string>? outputExecutorIds)
+        Dictionary<string, HashSet<OutputTag>>? outputExecutorIds)
     {
         this.Executors = Throw.IfNull(executors);
         this.Edges = Throw.IfNull(edges);
         this.RequestPorts = Throw.IfNull(requestPorts);
 
         this.StartExecutorId = Throw.IfNullOrEmpty(startExecutorId);
-        this.OutputExecutorIds = outputExecutorIds ?? [];
+        this.OutputExecutorIds = outputExecutorIds ?? new Dictionary<string, HashSet<OutputTag>>(StringComparer.Ordinal);
     }
 
     public Dictionary<string, ExecutorInfo> Executors { get; }
@@ -32,7 +33,15 @@ internal sealed class WorkflowInfo
     public TypeId? InputType { get; }
     public string StartExecutorId { get; }
 
-    public HashSet<string> OutputExecutorIds { get; }
+    /// <summary>
+    /// Map of executor id to the set of <see cref="OutputTag"/>s under which the executor is registered.
+    /// An empty set means the executor is registered as a regular (untagged) output source.
+    /// JSON shape: <c>{ "executorId": ["intermediate"], ... }</c>. Legacy payloads using the
+    /// older <c>string[]</c> shape are read by <see cref="WorkflowInfoOutputExecutorsConverter"/> and
+    /// each id is treated as registered with an empty tag set.
+    /// </summary>
+    [JsonConverter(typeof(WorkflowInfoOutputExecutorsConverter))]
+    public Dictionary<string, HashSet<OutputTag>> OutputExecutorIds { get; }
 
     public bool IsMatch(Workflow workflow)
     {
@@ -80,9 +89,12 @@ internal sealed class WorkflowInfo
             return false;
         }
 
-        // Validate the outputs
+        // Validate the outputs (key set + tag set per id must match)
         if (workflow.OutputExecutors.Count != this.OutputExecutorIds.Count ||
-            this.OutputExecutorIds.Any(id => !workflow.OutputExecutors.Contains(id)))
+            this.OutputExecutorIds.Any(kvp =>
+                !workflow.OutputExecutors.TryGetValue(kvp.Key, out HashSet<OutputTag>? tags) ||
+                tags.Count != kvp.Value.Count ||
+                !tags.SetEquals(kvp.Value)))
         {
             return false;
         }

dotnet/src/Microsoft.Agents.AI.Workflows/Checkpointing/WorkflowInfoOutputExecutorsConverter.cs

@@ -0,0 +1,122 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Microsoft.Agents.AI.Workflows.Checkpointing;
+
+/// <summary>
+/// JSON converter for <see cref="WorkflowInfo.OutputExecutorIds"/> that supports both the new
+/// map shape (<c>{ "id": ["intermediate"] }</c>) and the legacy array shape
+/// (<c>["id1", "id2"]</c>). Legacy-shaped payloads are read as if every id had been registered
+/// as a regular (untagged) output source; output is always written in the new map shape.
+/// </summary>
+internal sealed class WorkflowInfoOutputExecutorsConverter : JsonConverter<Dictionary<string, HashSet<OutputTag>>>
+{
+    public override Dictionary<string, HashSet<OutputTag>> Read(
+        ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        Dictionary<string, HashSet<OutputTag>> result = new(StringComparer.Ordinal);
+
+        if (reader.TokenType == JsonTokenType.Null)
+        {
+            return result;
+        }
+
+        if (reader.TokenType == JsonTokenType.StartArray)
+        {
+            // Legacy shape: a flat array of executor ids. Treat each as a registered
+            // (untagged) output executor.
+            while (reader.Read())
+            {
+                if (reader.TokenType == JsonTokenType.EndArray)
+                {
+                    return result;
+                }
+
+                if (reader.TokenType != JsonTokenType.String)
+                {
+                    throw new JsonException($"Expected a string in legacy outputExecutorIds array, got {reader.TokenType}.");
+                }
+
+                string id = reader.GetString()!;
+                result[id] = [];
+            }
+
+            throw new JsonException("Unexpected end of legacy outputExecutorIds array.");
+        }
+
+        if (reader.TokenType != JsonTokenType.StartObject)
+        {
+            throw new JsonException($"Expected object or array for outputExecutorIds, got {reader.TokenType}.");
+        }
+
+        while (reader.Read())
+        {
+            if (reader.TokenType == JsonTokenType.EndObject)
+            {
+                return result;
+            }
+
+            if (reader.TokenType != JsonTokenType.PropertyName)
+            {
+                throw new JsonException($"Expected property name in outputExecutorIds object, got {reader.TokenType}.");
+            }
+
+            string id = reader.GetString()!;
+            reader.Read();
+
+            HashSet<OutputTag> tags = [];
+            if (reader.TokenType == JsonTokenType.StartArray)
+            {
+                while (reader.Read() && reader.TokenType != JsonTokenType.EndArray)
+                {
+                    if (reader.TokenType != JsonTokenType.String)
+                    {
+                        throw new JsonException($"Expected a string tag, got {reader.TokenType}.");
+                    }
+
+                    tags.Add(ReadTag(reader.GetString()!));
+                }
+            }
+            else
+            {
+                throw new JsonException($"Expected array of tags for outputExecutorIds[{id}], got {reader.TokenType}.");
+            }
+
+            result[id] = tags;
+        }
+
+        throw new JsonException("Unexpected end of outputExecutorIds object.");
+    }
+
+    private static OutputTag ReadTag(string value)
+    {
+        if (string.Equals(value, OutputTag.Intermediate.Value, StringComparison.Ordinal))
+        {
+            return OutputTag.Intermediate;
+        }
+        return new OutputTag(value);
+    }
+
+    public override void Write(
+        Utf8JsonWriter writer,
+        Dictionary<string, HashSet<OutputTag>> value,
+        JsonSerializerOptions options)
+    {
+        writer.WriteStartObject();
+        foreach (KeyValuePair<string, HashSet<OutputTag>> kvp in value)
+        {
+            writer.WritePropertyName(kvp.Key);
+            writer.WriteStartArray();
+            foreach (OutputTag tag in kvp.Value)
+            {
+                writer.WriteStringValue(tag.Value);
+            }
+            writer.WriteEndArray();
+        }
+        writer.WriteEndObject();
+    }
+}

dotnet/src/Microsoft.Agents.AI.Workflows/ConcurrentWorkflowBuilder.cs

@@ -0,0 +1,104 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.Agents.AI.Workflows.Specialized;
+using Microsoft.Extensions.AI;
+using Microsoft.Shared.Diagnostics;
+
+namespace Microsoft.Agents.AI.Workflows;
+
+/// <summary>
+/// Fluent builder for concurrent agent workflows: a fan-out start that broadcasts the
+/// incoming messages to every participating agent, a per-agent accumulator that batches
+/// each agent's outgoing messages, and a fan-in aggregator that reduces them into a
+/// single output list.
+/// </summary>
+/// <remarks>
+/// When no explicit output designations are made, the default is the Python-aligned
+/// shape: the terminal aggregator is the workflow output, and every participating agent
+/// (plus its per-agent accumulator) is designated as an intermediate output source.
+/// Calling <see cref="OrchestrationBuilderBase{TBuilder}.WithOutputFrom(IEnumerable{AIAgent})"/>
+/// or <see cref="OrchestrationBuilderBase{TBuilder}.WithIntermediateOutputFrom(IEnumerable{AIAgent})"/>
+/// at all suppresses these defaults.
+/// </remarks>
+public sealed class ConcurrentWorkflowBuilder : OrchestrationBuilderBase<ConcurrentWorkflowBuilder>
+{
+    private readonly List<AIAgent> _agents = [];
+    private Func<IList<List<ChatMessage>>, List<ChatMessage>>? _aggregator;
+
+    /// <summary>
+    /// Initializes a new <see cref="ConcurrentWorkflowBuilder"/> with the given participating
+    /// <paramref name="agents"/>.
+    /// </summary>
+    public ConcurrentWorkflowBuilder(params IEnumerable<AIAgent> agents)
+    {
+        Throw.IfNull(agents);
+        foreach (AIAgent agent in agents)
+        {
+            Throw.IfNull(agent, nameof(agents));
+            this._agents.Add(agent);
+        }
+    }
+
+    /// <summary>
+    /// Sets the aggregator function. If not called, defaults to returning the last message
+    /// from each agent that produced at least one message.
+    /// </summary>
+    public ConcurrentWorkflowBuilder WithAggregator(Func<IList<List<ChatMessage>>, List<ChatMessage>> aggregator)
+    {
+        this._aggregator = Throw.IfNull(aggregator);
+        return this;
+    }
+
+    /// <summary>Builds the configured concurrent workflow.</summary>
+    public Workflow Build()
+    {
+        if (this._agents.Count == 0)
+        {
+            throw new ArgumentException("At least one agent must be provided to the ConcurrentWorkflowBuilder.", "agents");
+        }
+
+        ChatForwardingExecutor start = new("Start");
+        WorkflowBuilder builder = new(start);
+
+        Dictionary<AIAgent, ExecutorBinding> agentMap = new(AIAgentIDEqualityComparer.Instance);
+        ExecutorBinding[] agentExecutors = new ExecutorBinding[this._agents.Count];
+        ExecutorBinding[] accumulators = new ExecutorBinding[this._agents.Count];
+        AIAgentHostOptions options = new() { ReassignOtherAgentsAsUsers = true };
+        for (int i = 0; i < this._agents.Count; i++)
+        {
+            AIAgent agent = this._agents[i];
+            ExecutorBinding binding = agent.BindAsExecutor(options);
+            agentExecutors[i] = binding;
+            agentMap[agent] = binding;
+            accumulators[i] = new AggregateTurnMessagesExecutor($"Batcher/{binding.Id}");
+        }
+
+        builder.AddFanOutEdge(start, agentExecutors);
+        for (int i = 0; i < agentExecutors.Length; i++)
+        {
+            builder.AddEdge(agentExecutors[i], accumulators[i]);
+        }
+
+        Func<IList<List<ChatMessage>>, List<ChatMessage>> aggregator =
+            this._aggregator ?? (static lists => (from list in lists where list.Count > 0 select list.Last()).ToList());
+
+        Func<string, string, ValueTask<ConcurrentEndExecutor>> endFactory =
+            (_, __) => new(new ConcurrentEndExecutor(agentExecutors.Length, aggregator));
+
+        ExecutorBinding end = endFactory.BindExecutor(ConcurrentEndExecutor.ExecutorId);
+        builder.AddFanInBarrierEdge(accumulators, end);
+
+        this.ApplyMetadata(builder);
+        this.ApplyOutputDesignations(builder, agentMap, "concurrent", () =>
+        {
+            builder.WithOutputFrom(end);
+            builder.WithIntermediateOutputFrom([.. agentExecutors, .. accumulators]);
+        });
+
+        return builder.Build();
+    }
+}

dotnet/src/Microsoft.Agents.AI.Workflows/Execution/OutputFilter.cs

@@ -1,11 +1,17 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+
 namespace Microsoft.Agents.AI.Workflows.Execution;
 
 internal sealed class OutputFilter(Workflow workflow)
 {
     public bool CanOutput(string sourceExecutorId, object output)
     {
-        return workflow.OutputExecutors.Contains(sourceExecutorId);
+        return workflow.OutputExecutors.ContainsKey(sourceExecutorId);
     }
+
+    public bool TryGetTags(string sourceExecutorId, [NotNullWhen(true)] out HashSet<OutputTag>? tags)
+        => workflow.OutputExecutors.TryGetValue(sourceExecutorId, out tags);
 }

dotnet/src/Microsoft.Agents.AI.Workflows/Futures.cs

@@ -0,0 +1,40 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Microsoft.Agents.AI.Workflows;
+
+/// <summary>
+/// Process-wide opt-in switches for in-development behavior changes that will become
+/// the default in a future major release. Each flag defaults to <see langword="false"/>
+/// and should be toggled once at application startup.
+/// </summary>
+public static class Futures
+{
+    /// <summary>
+    /// When <see langword="true"/>, <see cref="AgentResponse"/> and
+    /// <see cref="AgentResponseUpdate"/> payloads yielded by an executor participate
+    /// in the normal output-filter pipeline (i.e. they must be designated via
+    /// <see cref="WorkflowBuilder.WithOutputFrom(ExecutorBinding[])"/> or
+    /// <see cref="WorkflowBuilderExtensions.WithIntermediateOutputFrom(WorkflowBuilder, System.Collections.Generic.IEnumerable{ExecutorBinding})"/>
+    /// to surface), and the resulting <see cref="WorkflowOutputEvent"/>s carry
+    /// <see cref="WorkflowOutputEvent.Tags"/> reflecting that designation.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// When <see langword="false"/> (the current default), the runner emits
+    /// <see cref="AgentResponseEvent"/> and <see cref="AgentResponseUpdateEvent"/> unconditionally,
+    /// bypassing the output filter (historical behavior). Lifecycle: opt-in today, marked
+    /// <c>[Obsolete]</c> in v2.0.0 when the new behavior becomes default, and removed in v3.0.0.
+    /// </para>
+    /// <para>
+    /// <b>Interaction with <see cref="WorkflowHostingExtensions.AsAIAgent"/>.</b> When this flag
+    /// is <see langword="true"/>, <see cref="AgentResponseEvent"/> joins
+    /// <see cref="AgentResponseUpdateEvent"/> in being forwarded out of the agent surface
+    /// unconditionally — neither honors the host's <c>includeWorkflowOutputsInResponse</c>
+    /// switch. That switch only governs the generic <see cref="WorkflowOutputEvent"/> path for
+    /// non-AIAgent payloads. When this flag is <see langword="false"/>, the legacy asymmetry
+    /// is preserved: <see cref="AgentResponseUpdateEvent"/> is always forwarded but
+    /// <see cref="AgentResponseEvent"/> stays gated by <c>includeWorkflowOutputsInResponse</c>.
+    /// </para>
+    /// </remarks>
+    public static bool EnableAgentResponseOutputTaggingAndFiltering { get; set; }
+}

dotnet/src/Microsoft.Agents.AI.Workflows/GroupChatManager.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.AI;
@@ -13,6 +15,16 @@ namespace Microsoft.Agents.AI.Workflows;
 /// </summary>
 public abstract class GroupChatManager
 {
+    // The state key under which GroupChatManager persists its own (non-subclass) state on the
+    // raw IWorkflowContext supplied by the hosting GroupChatHost executor.
+    internal const string BaseStateKey = "GroupChatManager";
+
+    // Prefix automatically applied to every key a subclass writes through the wrapped context
+    // supplied to OnCheckpointingAsync / OnCheckpointRestoredAsync. Keeps subclass-defined
+    // state in its own namespace so it cannot collide with the host's state keys nor with
+    // BaseStateKey itself.
+    internal const string SubclassStateKeyPrefix = "GroupChatManager_";
+
     /// <summary>
     /// Initializes a new instance of the <see cref="GroupChatManager"/> class.
     /// </summary>
@@ -48,12 +60,22 @@ public abstract class GroupChatManager
         CancellationToken cancellationToken = default);
 
     /// <summary>
-    /// Filters the chat history before it's passed to the next agent.
+    /// Filters the messages broadcast to participants for the current turn.
     /// </summary>
-    /// <param name="history">The chat history to filter.</param>
+    /// <remarks>
+    /// Under the broadcast model, each participant maintains its own per-agent session (history)
+    /// through its <see cref="Specialized.AIAgentHostExecutor"/>. The host distributes new messages
+    /// (initial user input on the first turn, the most recent speaker's response on subsequent turns)
+    /// to every participant — except the speaker that produced them — so every participant's session
+    /// stays synchronized. This method lets the manager shape that broadcast payload (for example,
+    /// to omit certain messages or to inject orchestrator-visible annotations). The full canonical
+    /// conversation is still available to <see cref="SelectNextAgentAsync"/> and
+    /// <see cref="ShouldTerminateAsync"/>.
+    /// </remarks>
+    /// <param name="history">The new messages about to be broadcast to participants this turn.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests.
     /// The default is <see cref="CancellationToken.None"/>.</param>
-    /// <returns>The filtered chat history.</returns>
+    /// <returns>The filtered message list to broadcast.</returns>
     protected internal virtual ValueTask<IEnumerable<ChatMessage>> UpdateHistoryAsync(
         IReadOnlyList<ChatMessage> history,
         CancellationToken cancellationToken = default) =>
@@ -78,4 +100,125 @@ public abstract class GroupChatManager
     {
         this.IterationCount = 0;
     }
+
+    /// <summary>
+    /// Invoked when the hosting group chat workflow is checkpointing, giving subclasses a chance to
+    /// persist any additional state they maintain (e.g., a round-robin cursor or an LLM session).
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The default implementation is a no-op. Base-class state (currently
+    /// <see cref="IterationCount"/>) is persisted automatically by the hosting
+    /// <see cref="Specialized.GroupChatHost"/> before this method is invoked; subclasses do not
+    /// need to call <c>base.OnCheckpointingAsync</c>.
+    /// </para>
+    /// <para>
+    /// The supplied <paramref name="context"/> is a wrapper that transparently prefixes every
+    /// state key with <c>"GroupChatManager_"</c>, isolating subclass state from the host's own
+    /// state keys (and from the reserved base-state key). Implementations therefore may use any
+    /// human-readable key (e.g., <c>"next_index"</c>) without worrying about collisions.
+    /// </para>
+    /// </remarks>
+    /// <param name="context">A wrapped workflow context that scopes state keys to the
+    /// <see cref="GroupChatManager"/> subclass namespace.</param>
+    /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests.
+    /// The default is <see cref="CancellationToken.None"/>.</param>
+    protected virtual ValueTask OnCheckpointingAsync(IWorkflowContext context, CancellationToken cancellationToken = default)
+        => default;
+
+    /// <summary>
+    /// Invoked when the hosting group chat workflow is being restored from a checkpoint, giving
+    /// subclasses a chance to hydrate any additional state they persisted in
+    /// <see cref="OnCheckpointingAsync"/>.
+    /// </summary>
+    /// <remarks>
+    /// The default implementation is a no-op. Base-class state (currently
+    /// <see cref="IterationCount"/>) is restored automatically by the hosting
+    /// <see cref="Specialized.GroupChatHost"/> before this method is invoked; subclasses do not
+    /// need to call <c>base.OnCheckpointRestoredAsync</c>. The supplied <paramref name="context"/>
+    /// uses the same key-prefixing wrapper as <see cref="OnCheckpointingAsync"/>.
+    /// </remarks>
+    /// <param name="context">A wrapped workflow context that scopes state keys to the
+    /// <see cref="GroupChatManager"/> subclass namespace.</param>
+    /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests.
+    /// The default is <see cref="CancellationToken.None"/>.</param>
+    protected virtual ValueTask OnCheckpointRestoredAsync(IWorkflowContext context, CancellationToken cancellationToken = default)
+        => default;
+
+    // Root checkpoint entry point invoked by the hosting GroupChatHost. Persists the manager's
+    // own base state under the reserved BaseStateKey on the raw context, then delegates to the
+    // subclass-facing OnCheckpointingAsync hook with a wrapped context that prefixes every key
+    // with SubclassStateKeyPrefix.
+    internal async ValueTask CheckpointAsync(IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        await context.QueueStateUpdateAsync(BaseStateKey, new GroupChatManagerState(this.IterationCount), cancellationToken: cancellationToken).ConfigureAwait(false);
+        await this.OnCheckpointingAsync(new PrefixingWorkflowContext(context, SubclassStateKeyPrefix), cancellationToken).ConfigureAwait(false);
+    }
+
+    // Root restore entry point invoked by the hosting GroupChatHost. Symmetric to CheckpointAsync.
+    internal async ValueTask RestoreCheckpointAsync(IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        GroupChatManagerState? state = await context.ReadStateAsync<GroupChatManagerState>(BaseStateKey, cancellationToken: cancellationToken).ConfigureAwait(false);
+        this.IterationCount = state?.IterationCount ?? 0;
+        await this.OnCheckpointRestoredAsync(new PrefixingWorkflowContext(context, SubclassStateKeyPrefix), cancellationToken).ConfigureAwait(false);
+    }
+}
+
+internal sealed record GroupChatManagerState(int IterationCount);
+
+// IWorkflowContext decorator that prepends a fixed prefix to every state key passed through it.
+// All non-state members (events, message sending, output yielding, halt requests, trace context,
+// and runtime characteristics) delegate directly to the wrapped context.
+internal sealed class PrefixingWorkflowContext(IWorkflowContext inner, string prefix) : IWorkflowContext
+{
+    private readonly IWorkflowContext _inner = Throw.IfNull(inner);
+    private readonly string _prefix = Throw.IfNullOrEmpty(prefix);
+
+    public IReadOnlyDictionary<string, string>? TraceContext => this._inner.TraceContext;
+
+    public bool ConcurrentRunsEnabled => this._inner.ConcurrentRunsEnabled;
+
+    public ValueTask AddEventAsync(WorkflowEvent workflowEvent, CancellationToken cancellationToken = default)
+        => this._inner.AddEventAsync(workflowEvent, cancellationToken);
+
+    public ValueTask SendMessageAsync(object message, string? targetId, CancellationToken cancellationToken = default)
+        => this._inner.SendMessageAsync(message, targetId, cancellationToken);
+
+    public ValueTask YieldOutputAsync(object output, CancellationToken cancellationToken = default)
+        => this._inner.YieldOutputAsync(output, cancellationToken);
+
+    public ValueTask RequestHaltAsync() => this._inner.RequestHaltAsync();
+
+    public ValueTask<T?> ReadStateAsync<T>(string key, string? scopeName = null, CancellationToken cancellationToken = default)
+        => this._inner.ReadStateAsync<T>(this.Wrap(key), scopeName, cancellationToken);
+
+    public ValueTask<T> ReadOrInitStateAsync<T>(string key, Func<T> initialStateFactory, string? scopeName = null, CancellationToken cancellationToken = default)
+        => this._inner.ReadOrInitStateAsync(this.Wrap(key), initialStateFactory, scopeName, cancellationToken);
+
+    public async ValueTask<HashSet<string>> ReadStateKeysAsync(string? scopeName = null, CancellationToken cancellationToken = default)
+    {
+        HashSet<string> rawKeys = await this._inner.ReadStateKeysAsync(scopeName, cancellationToken).ConfigureAwait(false);
+        return [.. rawKeys.Where(k => k.StartsWith(this._prefix, StringComparison.Ordinal))
+                          .Select(k => k.Substring(this._prefix.Length))];
+    }
+
+    public ValueTask QueueStateUpdateAsync<T>(string key, T? value, string? scopeName = null, CancellationToken cancellationToken = default)
+        => this._inner.QueueStateUpdateAsync(this.Wrap(key), value, scopeName, cancellationToken);
+
+    public async ValueTask QueueClearScopeAsync(string? scopeName = null, CancellationToken cancellationToken = default)
+    {
+        // Clearing the entire underlying scope would also remove keys owned by the host and other
+        // subsystems sharing the executor's default scope. Restrict the clear to keys carrying
+        // this wrapper's prefix.
+        HashSet<string> rawKeys = await this._inner.ReadStateKeysAsync(scopeName, cancellationToken).ConfigureAwait(false);
+        foreach (string rawKey in rawKeys)
+        {
+            if (rawKey.StartsWith(this._prefix, StringComparison.Ordinal))
+            {
+                await this._inner.QueueStateUpdateAsync<object>(rawKey, null, scopeName, cancellationToken).ConfigureAwait(false);
+            }
+        }
+    }
+
+    private string Wrap(string key) => this._prefix + Throw.IfNullOrEmpty(key);
 }

dotnet/src/Microsoft.Agents.AI.Workflows/GroupChatWorkflowBuilder.cs

@@ -12,12 +12,10 @@ namespace Microsoft.Agents.AI.Workflows;
 /// <summary>
 /// Provides a builder for specifying group chat relationships between agents and building the resulting workflow.
 /// </summary>
-public sealed class GroupChatWorkflowBuilder
+public sealed class GroupChatWorkflowBuilder : OrchestrationBuilderBase<GroupChatWorkflowBuilder>
 {
     private readonly Func<IReadOnlyList<AIAgent>, GroupChatManager> _managerFactory;
     private readonly HashSet<AIAgent> _participants = new(AIAgentIDEqualityComparer.Instance);
-    private string _name = string.Empty;
-    private string _description = string.Empty;
 
     internal GroupChatWorkflowBuilder(Func<IReadOnlyList<AIAgent>, GroupChatManager> managerFactory) =>
         this._managerFactory = managerFactory;
@@ -44,28 +42,6 @@ public sealed class GroupChatWorkflowBuilder
         return this;
     }
 
-    /// <summary>
-    /// Sets the human-readable name for the workflow.
-    /// </summary>
-    /// <param name="name">The name of the workflow.</param>
-    /// <returns>This instance of the <see cref="GroupChatWorkflowBuilder"/>.</returns>
-    public GroupChatWorkflowBuilder WithName(string name)
-    {
-        this._name = name;
-        return this;
-    }
-
-    /// <summary>
-    /// Sets the description for the workflow.
-    /// </summary>
-    /// <param name="description">The description of what the workflow does.</param>
-    /// <returns>This instance of the <see cref="GroupChatWorkflowBuilder"/>.</returns>
-    public GroupChatWorkflowBuilder WithDescription(string description)
-    {
-        this._description = description;
-        return this;
-    }
-
     /// <summary>
     /// Builds a <see cref="Workflow"/> composed of agents that operate via group chat, with the next
     /// agent to process messages selected by the group chat manager.
@@ -75,10 +51,14 @@ public sealed class GroupChatWorkflowBuilder
     {
         AIAgent[] agents = this._participants.ToArray();
 
+        // GroupChatHost owns the canonical conversation and broadcasts messages directly to every
+        // participant. Participants therefore must not echo their incoming messages back to the host
+        // (which would cause duplicates), but must still reframe other agents' assistant messages as
+        // user messages so each agent's own session reads coherently.
         AIAgentHostOptions options = new()
         {
             ReassignOtherAgentsAsUsers = true,
-            ForwardIncomingMessages = true
+            ForwardIncomingMessages = false
         };
 
         Dictionary<AIAgent, ExecutorBinding> agentMap = agents.ToDictionary(a => a, a => a.BindAsExecutor(options));
@@ -89,15 +69,7 @@ public sealed class GroupChatWorkflowBuilder
         ExecutorBinding host = groupChatHostFactory.BindExecutor(nameof(GroupChatHost));
         WorkflowBuilder builder = new(host);
 
-        if (!string.IsNullOrEmpty(this._name))
-        {
-            builder = builder.WithName(this._name);
-        }
-
-        if (!string.IsNullOrEmpty(this._description))
-        {
-            builder = builder.WithDescription(this._description);
-        }
+        this.ApplyMetadata(builder);
 
         foreach (var participant in agentMap.Values)
         {
@@ -106,6 +78,15 @@ public sealed class GroupChatWorkflowBuilder
                 .AddEdge(participant, host);
         }
 
-        return builder.WithOutputFrom(host).Build();
+        this.ApplyOutputDesignations(builder, agentMap, "group chat", () =>
+        {
+            builder.WithOutputFrom(host);
+            if (agentMap.Count > 0)
+            {
+                builder.WithIntermediateOutputFrom([.. agentMap.Values]);
+            }
+        });
+
+        return builder.Build();
     }
 }

dotnet/src/Microsoft.Agents.AI.Workflows/HandoffWorkflowBuilder.cs

@@ -15,11 +15,6 @@ using ExecutorFactoryFunc = System.Func<Microsoft.Agents.AI.Workflows.ExecutorCo
 
 namespace Microsoft.Agents.AI.Workflows;
 
-internal static class DiagnosticConstants
-{
-    public const string ExperimentalFeatureDiagnostic = "MAAIW001";
-}
-
 /// <inheritdoc/>
 [ExcludeFromCodeCoverage] // This is obsolete, and 1:1 equivalent to HandoffWorkflowBuilder (no "s")
 [Obsolete("Prefer HandoffWorkflowBuilder (no 's') instead, which has the same API but the preferred name. This will be removed in a future release before GA.")]
@@ -30,7 +25,6 @@ public sealed class HandoffsWorkflowBuilder(AIAgent initialAgent) : HandoffWorkf
 }
 
 /// <inheritdoc/>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 public sealed class HandoffWorkflowBuilder(AIAgent initialAgent) : HandoffWorkflowBuilderCore<HandoffWorkflowBuilder>(initialAgent)
 {
 }
@@ -38,8 +32,8 @@ public sealed class HandoffWorkflowBuilder(AIAgent initialAgent) : HandoffWorkfl
 /// <summary>
 /// Provides a builder for specifying the handoff relationships between agents and building the resulting workflow.
 /// </summary>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
-public class HandoffWorkflowBuilderCore<TBuilder> where TBuilder : HandoffWorkflowBuilderCore<TBuilder>
+public class HandoffWorkflowBuilderCore<TBuilder> : OrchestrationBuilderBase<TBuilder>
+    where TBuilder : HandoffWorkflowBuilderCore<TBuilder>
 {
     /// <summary>
     /// The prefix for function calls that trigger handoffs to other agents; the full name is then `{FunctionPrefix}&lt;agent_id&gt;`,
@@ -55,8 +49,6 @@ public class HandoffWorkflowBuilderCore<TBuilder> where TBuilder : HandoffWorkfl
     private bool _emitAgentResponseUpdateEvents;
     private HandoffToolCallFilteringBehavior _toolCallFilteringBehavior = HandoffToolCallFilteringBehavior.HandoffOnly;
     private bool _returnToPrevious;
-    private string? _name;
-    private string? _description;
 
     // Autonomous mode configuration. When enabled, an agent's response that doesn't include a
     // handoff triggers another invocation of that same agent with the continuation prompt, up to
@@ -116,20 +108,6 @@ public class HandoffWorkflowBuilderCore<TBuilder> where TBuilder : HandoffWorkfl
         return (TBuilder)this;
     }
 
-    /// <inheritdoc cref="WorkflowBuilder.WithName(string)"/>
-    public TBuilder WithName(string name)
-    {
-        this._name = name;
-        return (TBuilder)this;
-    }
-
-    /// <inheritdoc cref="WorkflowBuilder.WithDescription(string)"/>
-    public TBuilder WithDescription(string description)
-    {
-        this._description = description;
-        return (TBuilder)this;
-    }
-
     /// <summary>
     /// Sets a value indicating whether agent streaming update events should be emitted during execution.
     /// If <see langword="null"/>, the value will be taken from the <see cref="TurnToken"/>
@@ -631,16 +609,31 @@ public class HandoffWorkflowBuilderCore<TBuilder> where TBuilder : HandoffWorkfl
             });
         }
 
-        if (!string.IsNullOrWhiteSpace(this._name))
+        // Ensure the end executor is bound regardless of whether it ends up as an output
+        // designation source — the user may take full control of output designations.
+        builder.BindExecutor(end);
+
+        // Build the AIAgent -> ExecutorBinding map the base helper expects.
+        Dictionary<AIAgent, ExecutorBinding> agentMap = new(AIAgentIDEqualityComparer.Instance);
+        foreach (AIAgent agent in this._allAgents)
         {
-            builder.WithName(this._name);
+            agentMap[agent] = executors[agent.Id];
         }
 
-        if (!string.IsNullOrWhiteSpace(this._description))
+        this.ApplyMetadata(builder);
+        this.ApplyOutputDesignations(builder, agentMap, "handoff", () =>
         {
-            builder.WithDescription(this._description);
-        }
+            // Defaults (matches Python's Handoff orchestration):
+            //   end                  -> terminal output
+            //   every handoff agent  -> intermediate output
+            builder.WithOutputFrom(end);
+            List<ExecutorBinding> agentBindings = [.. executors.Values];
+            if (agentBindings.Count > 0)
+            {
+                builder.WithIntermediateOutputFrom(agentBindings);
+            }
+        });
 
-        return builder.WithOutputFrom(end).Build();
+        return builder.Build();
     }
 }

dotnet/src/Microsoft.Agents.AI.Workflows/InProc/InProcessRunnerContext.cs

@@ -241,30 +241,47 @@ internal sealed class InProcessRunnerContext : IRunnerContext
         this.CheckEnded();
         Throw.IfNull(output);
 
-        // Special-case AgentResponse and AgentResponseUpdate to create their specific event types
-        // and bypass the output filter (for backwards compatibility - these events were previously
-        // emitted directly via AddEventAsync without filtering)
-        if (output is AgentResponseUpdate update)
+        bool isAgentResponseShaped = output is AgentResponse or AgentResponseUpdate;
+
+        if (isAgentResponseShaped && !Futures.EnableAgentResponseOutputTaggingAndFiltering)
         {
-            await this.AddEventAsync(new AgentResponseUpdateEvent(sourceId, update), cancellationToken).ConfigureAwait(false);
-            return;
-        }
-        else if (output is AgentResponse response)
-        {
-            await this.AddEventAsync(new AgentResponseEvent(sourceId, response), cancellationToken).ConfigureAwait(false);
+            // Legacy bypass: AgentResponse/AgentResponseUpdate skip the output filter and are
+            // emitted as their typed event subclasses with no tags. Preserved verbatim for
+            // back-compat; once Futures.EnableAgentResponseOutputTaggingAndFiltering becomes the
+            // default in v2.0.0, this branch goes away.
+            WorkflowEvent typedEvent = output switch
+            {
+                AgentResponseUpdate u => new AgentResponseUpdateEvent(sourceId, u),
+                AgentResponse r => new AgentResponseEvent(sourceId, r),
+                _ => throw new InvalidOperationException("Unexpected AIAgent-shaped payload type."),
+            };
+            await this.AddEventAsync(typedEvent, cancellationToken).ConfigureAwait(false);
             return;
         }
 
         Executor sourceExecutor = await this.EnsureExecutorAsync(sourceId, tracer: null, cancellationToken).ConfigureAwait(false);
-        if (!sourceExecutor.CanOutput(output.GetType()))
+        if (!isAgentResponseShaped && !sourceExecutor.CanOutput(output.GetType()))
         {
+            // AIAgent-shaped payloads bypass the per-executor declared-yield check (matching the
+            // legacy bypass branch above). The AIAgent host executor relays the agent's output
+            // without declaring AgentResponse(Update) in its Yields set, so a CanOutput probe
+            // here would always reject — but those payloads are always a valid output shape.
             throw new InvalidOperationException($"Cannot output object of type {output.GetType().Name}. Expecting one of [{string.Join(", ", sourceExecutor.OutputTypes)}].");
         }
 
-        if (this._outputFilter.CanOutput(sourceId, output))
+        if (!this._outputFilter.TryGetTags(sourceId, out HashSet<OutputTag>? tags))
         {
-            await this.AddEventAsync(new WorkflowOutputEvent(output, sourceId), cancellationToken).ConfigureAwait(false);
+            // Not designated as an output source — drop silently.
+            return;
         }
+
+        WorkflowOutputEvent evt = output switch
+        {
+            AgentResponseUpdate u => new AgentResponseUpdateEvent(sourceId, u, tags),
+            AgentResponse r => new AgentResponseEvent(sourceId, r, tags),
+            _ => new WorkflowOutputEvent(output, sourceId, tags),
+        };
+        await this.AddEventAsync(evt, cancellationToken).ConfigureAwait(false);
     }
 
     public IExternalRequestContext BindExternalRequestContext(string executorId)

dotnet/src/Microsoft.Agents.AI.Workflows/MagenticPlanReviewRequest.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Microsoft.Extensions.AI;
 
@@ -16,7 +15,6 @@ namespace Microsoft.Agents.AI.Workflows;
 /// contain the latest progress ledger that determined that no progress has been made or the workflow was in
 /// a loop.</param>
 /// <param name="IsStalled">Whether the workflow is currently stalled.</param>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 public record MagenticPlanReviewRequest(ChatMessage Plan, MagenticProgressLedger? CurrentProgress, bool IsStalled)
 {
     /// <summary>

dotnet/src/Microsoft.Agents.AI.Workflows/MagenticPlanReviewResponse.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using Microsoft.Extensions.AI;
 
 namespace Microsoft.Agents.AI.Workflows;
@@ -13,7 +12,6 @@ namespace Microsoft.Agents.AI.Workflows;
 /// <param name="Review">
 /// Review feedback for a generated plan. Empty if the plan is approved as-is and changes are requested.
 /// </param>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 public record MagenticPlanReviewResponse(List<ChatMessage> Review)
 {
     internal bool IsApproved => this.Review.Count == 0;

dotnet/src/Microsoft.Agents.AI.Workflows/MagenticProgressLedger.cs

@@ -14,7 +14,6 @@ namespace Microsoft.Agents.AI.Workflows;
 /// <summary>
 /// Maintains a ledger of progress made by the Magentic workflow.
 /// </summary>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 public class MagenticProgressLedger
 {
     internal static readonly BooleanProgressLedgerSlot IsRequestSatisfiedSlot = new("is_request_satisfied",
@@ -76,7 +75,7 @@ public class MagenticProgressLedger
             this.InstructionOrQuestion = instructionOrQuestion!;
         }
 
-        // TODO: To what extent do we want to enforce that the additional questions are also answered? 
+        // TODO: To what extent do we want to enforce that the additional questions are also answered?
 
         return requiredQuestionsAnswered;
     }

dotnet/src/Microsoft.Agents.AI.Workflows/MagenticWorkflowBuilder.cs

@@ -2,7 +2,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using System.Threading.Tasks;
 using Microsoft.Agents.AI.Workflows.Specialized.Magentic;
 
@@ -27,12 +26,9 @@ namespace Microsoft.Agents.AI.Workflows;
 ///   not supported on the ManagerAgent.
 /// </summary>
 /// <param name="managerAgent"></param>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
-public class MagenticWorkflowBuilder(AIAgent managerAgent)
+public class MagenticWorkflowBuilder(AIAgent managerAgent) : OrchestrationBuilderBase<MagenticWorkflowBuilder>
 {
     private readonly List<AIAgent> _team = new();
-    private string? _name;
-    private string? _description;
     private int _maxStalls = TaskLimits.DefaultMaxStallCount;
     private int? _maxRounds;
     private int? _maxResets;
@@ -45,20 +41,6 @@ public class MagenticWorkflowBuilder(AIAgent managerAgent)
         return this;
     }
 
-    /// <inheritdoc cref="WorkflowBuilder.WithName(string)"/>
-    public MagenticWorkflowBuilder WithName(string name)
-    {
-        this._name = name;
-        return this;
-    }
-
-    /// <inheritdoc cref="WorkflowBuilder.WithDescription(string)"/>
-    public MagenticWorkflowBuilder WithDescription(string description)
-    {
-        this._description = description;
-        return this;
-    }
-
     /// <summary>
     /// Set the maximum number of coordination rounds. <see langword="null"/> means unlimited.
     /// </summary>
@@ -115,28 +97,29 @@ public class MagenticWorkflowBuilder(AIAgent managerAgent)
             ForwardIncomingMessages = false
         };
 
+        Dictionary<AIAgent, ExecutorBinding> teamMap = new(AIAgentIDEqualityComparer.Instance);
         List<ExecutorBinding> teamBindings = [];
         foreach (AIAgent agent in team)
         {
             ExecutorBinding binding = agent.BindAsExecutor(options);
             teamBindings.Add(binding);
+            teamMap[agent] = binding;
 
             result.AddEdge(binding, orchestrator);
         }
 
-        result.AddFanOutEdge(orchestrator, teamBindings)
-              .WithOutputFrom(orchestrator);
+        result.AddFanOutEdge(orchestrator, teamBindings);
 
-        if (!string.IsNullOrWhiteSpace(this._name))
+        this.ApplyOutputDesignations(result, teamMap, "Magentic", () =>
         {
-            result.WithName(this._name);
-        }
-
-        if (!string.IsNullOrWhiteSpace(this._description))
-        {
-            result.WithDescription(this._description);
-        }
+            result.WithOutputFrom(orchestrator);
+            if (teamMap.Count > 0)
+            {
+                result.WithIntermediateOutputFrom([.. teamMap.Values]);
+            }
+        });
 
+        this.ApplyMetadata(result);
         return result;
     }
 

dotnet/src/Microsoft.Agents.AI.Workflows/OrchestrationBuilderBase.cs

@@ -0,0 +1,154 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using Microsoft.Shared.Diagnostics;
+
+namespace Microsoft.Agents.AI.Workflows;
+
+/// <summary>
+/// Common fluent surface shared by every orchestration-style workflow builder:
+/// human-readable name + description, and the
+/// <see cref="WithOutputFrom"/> / <see cref="WithIntermediateOutputFrom"/> output-designation
+/// pair with memoized defaults-suppression semantics.
+/// </summary>
+/// <typeparam name="TBuilder">The concrete builder type, for fluent self-return.</typeparam>
+public abstract class OrchestrationBuilderBase<TBuilder>
+    where TBuilder : OrchestrationBuilderBase<TBuilder>
+{
+    /// <summary>Optional workflow name; applied to the inner <see cref="WorkflowBuilder"/> at <c>Build()</c>.</summary>
+    protected string? Name { get; private set; }
+
+    /// <summary>Optional workflow description; applied to the inner <see cref="WorkflowBuilder"/> at <c>Build()</c>.</summary>
+    protected string? Description { get; private set; }
+
+    /// <summary>
+    /// Memoized output designations. <see langword="null"/> means the user has not made any
+    /// explicit designation, and the orchestration-specific defaults will be applied at
+    /// <c>Build()</c> time. A non-<see langword="null"/> (possibly empty) map means the user took
+    /// control and only these designations will be replayed onto the inner
+    /// <see cref="WorkflowBuilder"/>. An entry's value is the set of tags requested for the
+    /// agent — an empty set encodes a terminal-only designation.
+    /// </summary>
+    protected Dictionary<AIAgent, HashSet<OutputTag>>? OutputDesignations { get; private set; }
+
+    /// <summary>Sets the human-readable name for the workflow.</summary>
+    public TBuilder WithName(string name)
+    {
+        this.Name = name;
+        return (TBuilder)this;
+    }
+
+    /// <summary>Sets the description for the workflow.</summary>
+    public TBuilder WithDescription(string description)
+    {
+        this.Description = description;
+        return (TBuilder)this;
+    }
+
+    /// <summary>
+    /// Designates the given <paramref name="agents"/> as sources of terminal workflow output.
+    /// Calling any output-designation method (this or <see cref="WithIntermediateOutputFrom"/>)
+    /// suppresses the orchestration-specific defaults: only the user-specified designations
+    /// reach the inner <see cref="WorkflowBuilder"/>.
+    /// </summary>
+    public TBuilder WithOutputFrom(params IEnumerable<AIAgent> agents)
+    {
+        Throw.IfNull(agents);
+        this.OutputDesignations ??= new(AIAgentIDEqualityComparer.Instance);
+        foreach (AIAgent agent in agents)
+        {
+            Throw.IfNull(agent, nameof(agents));
+            if (!this.OutputDesignations.ContainsKey(agent))
+            {
+                this.OutputDesignations[agent] = [];
+            }
+        }
+        return (TBuilder)this;
+    }
+
+    /// <summary>
+    /// Designates the given <paramref name="agents"/> as sources of <b>intermediate</b> workflow
+    /// output. See <see cref="WithOutputFrom"/> for the defaults-suppression semantics.
+    /// </summary>
+    public TBuilder WithIntermediateOutputFrom(IEnumerable<AIAgent> agents)
+    {
+        Throw.IfNull(agents);
+        this.OutputDesignations ??= new(AIAgentIDEqualityComparer.Instance);
+        foreach (AIAgent agent in agents)
+        {
+            Throw.IfNull(agent, nameof(agents));
+            if (!this.OutputDesignations.TryGetValue(agent, out HashSet<OutputTag>? tags))
+            {
+                tags = [];
+                this.OutputDesignations[agent] = tags;
+            }
+            tags.Add(OutputTag.Intermediate);
+        }
+        return (TBuilder)this;
+    }
+
+    /// <summary>
+    /// Applies the optional <see cref="Name"/> and <see cref="Description"/> to <paramref name="builder"/>.
+    /// Subclasses should call this from their <c>Build()</c> implementation.
+    /// </summary>
+    protected void ApplyMetadata(WorkflowBuilder builder)
+    {
+        Throw.IfNull(builder);
+        if (!string.IsNullOrWhiteSpace(this.Name))
+        {
+            builder.WithName(this.Name!);
+        }
+        if (!string.IsNullOrWhiteSpace(this.Description))
+        {
+            builder.WithDescription(this.Description!);
+        }
+    }
+
+    /// <summary>
+    /// Applies the user's memoized output designations to <paramref name="builder"/>, or invokes
+    /// <paramref name="applyDefaults"/> if the user made no explicit designation.
+    /// </summary>
+    /// <param name="builder">The inner <see cref="WorkflowBuilder"/>.</param>
+    /// <param name="agentMap">Map from participating <see cref="AIAgent"/> to its bound executor.</param>
+    /// <param name="orchestrationKind">Used in the not-a-participant error message (e.g. "sequential", "group chat").</param>
+    /// <param name="applyDefaults">Action invoked when no explicit designation was made.</param>
+    protected void ApplyOutputDesignations(
+        WorkflowBuilder builder,
+        IReadOnlyDictionary<AIAgent, ExecutorBinding> agentMap,
+        string orchestrationKind,
+        Action applyDefaults)
+    {
+        Throw.IfNull(builder);
+        Throw.IfNull(agentMap);
+        Throw.IfNull(applyDefaults);
+
+        if (this.OutputDesignations is null)
+        {
+            applyDefaults();
+            return;
+        }
+
+        foreach (AIAgent agent in this.OutputDesignations.Keys)
+        {
+            if (!agentMap.TryGetValue(agent, out ExecutorBinding? binding))
+            {
+                throw new InvalidOperationException(
+                    $"Output designation references agent '{agent.Name ?? agent.Id}', which is not a participant in this {orchestrationKind} workflow.");
+            }
+
+            HashSet<OutputTag> tags = this.OutputDesignations[agent];
+            if (tags.Count == 0)
+            {
+                builder.WithOutputFrom(binding);
+            }
+            else
+            {
+                foreach (OutputTag tag in tags)
+                {
+                    builder.WithOutputFrom(binding, tag);
+                }
+            }
+        }
+    }
+}

dotnet/src/Microsoft.Agents.AI.Workflows/OutputTag.cs

@@ -0,0 +1,52 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Text.Json.Serialization;
+using Microsoft.Shared.Diagnostics;
+
+namespace Microsoft.Agents.AI.Workflows;
+
+/// <summary>
+/// Identifies the kind of output that a <see cref="WorkflowOutputEvent"/> represents.
+/// A thin <c>ChatRole</c>-style wrapper around a normalized string <see cref="Value"/>,
+/// with value equality and a closed set of well-known singletons (the constructor is
+/// <see langword="internal"/> for now).
+/// </summary>
+[JsonConverter(typeof(OutputTagJsonConverter))]
+public readonly struct OutputTag : IEquatable<OutputTag>
+{
+    /// <summary>
+    /// The string identifier of the tag. Compared with ordinal equality.
+    /// </summary>
+    public string? Value { get; }
+
+    internal OutputTag(string value)
+    {
+        this.Value = Throw.IfNullOrEmpty(value);
+    }
+
+    /// <summary>
+    /// The tag denoting an intermediate workflow output &#x2014; emitted by executors
+    /// registered via <see cref="WorkflowBuilderExtensions.WithIntermediateOutputFrom(WorkflowBuilder, System.Collections.Generic.IEnumerable{ExecutorBinding})"/>.
+    /// Terminal (non-intermediate) outputs carry no tag.
+    /// </summary>
+    public static OutputTag Intermediate { get; } = new("intermediate");
+
+    /// <inheritdoc />
+    public bool Equals(OutputTag other) => string.Equals(this.Value, other.Value, StringComparison.Ordinal);
+
+    /// <inheritdoc />
+    public override bool Equals(object? obj) => obj is OutputTag other && this.Equals(other);
+
+    /// <inheritdoc />
+    public override int GetHashCode() => this.Value is null ? 0 : StringComparer.Ordinal.GetHashCode(this.Value);
+
+    /// <summary>Determines whether two <see cref="OutputTag"/> values are equal.</summary>
+    public static bool operator ==(OutputTag left, OutputTag right) => left.Equals(right);
+
+    /// <summary>Determines whether two <see cref="OutputTag"/> values are not equal.</summary>
+    public static bool operator !=(OutputTag left, OutputTag right) => !left.Equals(right);
+
+    /// <inheritdoc />
+    public override string ToString() => this.Value ?? string.Empty;
+}

dotnet/src/Microsoft.Agents.AI.Workflows/OutputTagJsonConverter.cs

@@ -0,0 +1,43 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Microsoft.Agents.AI.Workflows;
+
+/// <summary>
+/// JSON converter for <see cref="OutputTag"/> that round-trips the underlying
+/// <see cref="OutputTag.Value"/> as a bare JSON string.
+/// </summary>
+internal sealed class OutputTagJsonConverter : JsonConverter<OutputTag>
+{
+    public override OutputTag Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        string? value = reader.GetString();
+        if (string.IsNullOrEmpty(value))
+        {
+            return default;
+        }
+
+        // Reuse the well-known singleton where possible so callers can do reference
+        // comparisons on the common case without paying the extra allocation cost.
+        if (string.Equals(value, OutputTag.Intermediate.Value, StringComparison.Ordinal))
+        {
+            return OutputTag.Intermediate;
+        }
+
+        return new OutputTag(value!);
+    }
+
+    public override void Write(Utf8JsonWriter writer, OutputTag value, JsonSerializerOptions options)
+    {
+        if (value.Value is null)
+        {
+            writer.WriteNullValue();
+            return;
+        }
+
+        writer.WriteStringValue(value.Value);
+    }
+}

dotnet/src/Microsoft.Agents.AI.Workflows/RoundRobinGroupChatManager.cs

@@ -69,4 +69,23 @@ public class RoundRobinGroupChatManager : GroupChatManager
         base.Reset();
         this._nextIndex = 0;
     }
+
+    /// <inheritdoc />
+    protected override ValueTask OnCheckpointingAsync(IWorkflowContext context, CancellationToken cancellationToken = default)
+        => context.QueueStateUpdateAsync(StateKey, new RoundRobinGroupChatManagerState(this._nextIndex), cancellationToken: cancellationToken);
+
+    /// <inheritdoc />
+    protected override async ValueTask OnCheckpointRestoredAsync(IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        RoundRobinGroupChatManagerState? state = await context.ReadStateAsync<RoundRobinGroupChatManagerState>(StateKey, cancellationToken: cancellationToken).ConfigureAwait(false);
+        this._nextIndex = state?.NextIndex ?? 0;
+        if (this._nextIndex < 0 || this._nextIndex >= this._agents.Count)
+        {
+            this._nextIndex = 0;
+        }
+    }
+
+    private const string StateKey = "next_index";
 }
+
+internal sealed record RoundRobinGroupChatManagerState(int NextIndex);

dotnet/src/Microsoft.Agents.AI.Workflows/SequentialWorkflowBuilder.cs

@@ -0,0 +1,84 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.Shared.Diagnostics;
+
+namespace Microsoft.Agents.AI.Workflows;
+
+/// <summary>
+/// Fluent builder for sequential agent workflows: a pipeline where the output of one
+/// agent is the input to the next, terminating in an aggregator that yields the
+/// accumulated <see cref="Extensions.AI.ChatMessage"/>s as the workflow output.
+/// </summary>
+/// <remarks>
+/// When no explicit output designations are made, the default is the Python-aligned
+/// shape: the terminal aggregator is the workflow output, and every participating agent
+/// is designated as an intermediate output source. Calling
+/// <see cref="OrchestrationBuilderBase{TBuilder}.WithOutputFrom(IEnumerable{AIAgent})"/>
+/// or <see cref="OrchestrationBuilderBase{TBuilder}.WithIntermediateOutputFrom(IEnumerable{AIAgent})"/>
+/// at all suppresses these defaults.
+/// </remarks>
+public sealed class SequentialWorkflowBuilder : OrchestrationBuilderBase<SequentialWorkflowBuilder>
+{
+    private readonly List<AIAgent> _agents = [];
+
+    /// <summary>
+    /// Initializes a new <see cref="SequentialWorkflowBuilder"/> with the given pipeline
+    /// of <paramref name="agents"/>.
+    /// </summary>
+    public SequentialWorkflowBuilder(params IEnumerable<AIAgent> agents)
+    {
+        Throw.IfNull(agents);
+        foreach (AIAgent agent in agents)
+        {
+            Throw.IfNull(agent, nameof(agents));
+            this._agents.Add(agent);
+        }
+    }
+
+    /// <summary>Builds the configured sequential workflow.</summary>
+    public Workflow Build()
+    {
+        if (this._agents.Count == 0)
+        {
+            throw new ArgumentException("At least one agent must be provided to the SequentialWorkflowBuilder.", "agents");
+        }
+
+        AIAgentHostOptions options = new()
+        {
+            ReassignOtherAgentsAsUsers = true,
+            ForwardIncomingMessages = true,
+        };
+
+        Dictionary<AIAgent, ExecutorBinding> agentMap = new(AIAgentIDEqualityComparer.Instance);
+        List<ExecutorBinding> agentExecutors = new(this._agents.Count);
+        foreach (AIAgent agent in this._agents)
+        {
+            ExecutorBinding binding = agent.BindAsExecutor(options);
+            agentExecutors.Add(binding);
+            agentMap[agent] = binding;
+        }
+
+        ExecutorBinding previous = agentExecutors[0];
+        WorkflowBuilder builder = new(previous);
+        foreach (ExecutorBinding next in agentExecutors.Skip(1))
+        {
+            builder.AddEdge(previous, next);
+            previous = next;
+        }
+
+        OutputMessagesExecutor end = new();
+        builder.AddEdge(previous, end).BindExecutor(end);
+
+        this.ApplyMetadata(builder);
+        this.ApplyOutputDesignations(builder, agentMap, "sequential", () =>
+        {
+            builder.WithOutputFrom(end);
+            builder.WithIntermediateOutputFrom(agentExecutors);
+        });
+
+        return builder.Build();
+    }
+}

dotnet/src/Microsoft.Agents.AI.Workflows/Specialized/GroupChatHost.cs

@@ -20,12 +20,25 @@ internal sealed class GroupChatHost(
         AutoSendTurnToken = false
     };
 
+    private const string HistoryStateKey = nameof(_history);
+    private const string CurrentSpeakerStateKey = nameof(_currentSpeakerExecutorId);
+
     private readonly AIAgent[] _agents = agents;
     private readonly Dictionary<AIAgent, ExecutorBinding> _agentMap = agentMap;
     private readonly Func<IReadOnlyList<AIAgent>, GroupChatManager> _managerFactory = managerFactory;
 
     private GroupChatManager? _manager;
 
+    // Canonical conversation accumulated across turns. Each participant maintains its own per-agent
+    // session/thread; the host keeps this only as the source of truth for the manager hooks
+    // (SelectNextAgentAsync / ShouldTerminateAsync) and for the workflow's final output.
+    private List<ChatMessage> _history = [];
+
+    // Executor id of the participant we most recently dispatched a TurnToken to – i.e., the current
+    // speaker whose response is about to arrive. Used to exclude that participant from the next
+    // broadcast (its own session already contains the message it produced).
+    private string? _currentSpeakerExecutorId;
+
     protected override ProtocolBuilder ConfigureProtocol(ProtocolBuilder protocolBuilder)
         => base.ConfigureProtocol(protocolBuilder).YieldsOutput<List<ChatMessage>>();
 
@@ -33,30 +46,105 @@ internal sealed class GroupChatHost(
     {
         this._manager ??= this._managerFactory(this._agents);
 
-        if (!await this._manager.ShouldTerminateAsync(messages, cancellationToken).ConfigureAwait(false))
+        // The delta arriving here is either the initial user input (turn 0) or the most recent speaker's
+        // response (subsequent turns) – participants no longer echo incoming messages back to the host.
+        if (messages.Count > 0)
         {
-            var filtered = await this._manager.UpdateHistoryAsync(messages, cancellationToken).ConfigureAwait(false);
-            messages = filtered is null || ReferenceEquals(filtered, messages) ? messages : [.. filtered];
+            this._history.AddRange(messages);
+        }
 
-            if (await this._manager.SelectNextAgentAsync(messages, cancellationToken).ConfigureAwait(false) is AIAgent nextAgent &&
-                this._agentMap.TryGetValue(nextAgent, out var executor))
+        if (await this._manager.ShouldTerminateAsync(this._history, cancellationToken).ConfigureAwait(false))
+        {
+            await this.CompleteAsync(context, cancellationToken).ConfigureAwait(false);
+            return;
+        }
+
+        if (messages.Count > 0)
+        {
+            IEnumerable<ChatMessage> filteredDelta = await this._manager.UpdateHistoryAsync(messages, cancellationToken).ConfigureAwait(false);
+            List<ChatMessage> broadcastMessages = filteredDelta is null
+                ? messages
+                : (ReferenceEquals(filteredDelta, messages) ? messages : [.. filteredDelta]);
+
+            if (broadcastMessages.Count > 0)
             {
-                this._manager.IterationCount++;
-                await context.SendMessageAsync(messages, executor.Id, cancellationToken).ConfigureAwait(false);
-                await context.SendMessageAsync(new TurnToken(emitEvents), executor.Id, cancellationToken).ConfigureAwait(false);
-                return;
+                await this.BroadcastAsync(broadcastMessages, context, cancellationToken).ConfigureAwait(false);
             }
         }
 
-        this._manager = null;
-        await context.YieldOutputAsync(messages, cancellationToken).ConfigureAwait(false);
+        if (await this._manager.SelectNextAgentAsync(this._history, cancellationToken).ConfigureAwait(false) is AIAgent nextAgent &&
+            this._agentMap.TryGetValue(nextAgent, out ExecutorBinding? executor))
+        {
+            this._manager.IterationCount++;
+            this._currentSpeakerExecutorId = executor.Id;
+            await context.SendMessageAsync(new TurnToken(emitEvents), executor.Id, cancellationToken).ConfigureAwait(false);
+            return;
+        }
+
+        await this.CompleteAsync(context, cancellationToken).ConfigureAwait(false);
     }
+
+    private ValueTask BroadcastAsync(List<ChatMessage> messages, IWorkflowContext context, CancellationToken cancellationToken)
+    {
+        List<Task>? sendTasks = null;
+        foreach (ExecutorBinding participant in this._agentMap.Values)
+        {
+            if (string.Equals(participant.Id, this._currentSpeakerExecutorId, StringComparison.Ordinal))
+            {
+                continue;
+            }
+
+            (sendTasks ??= []).Add(context.SendMessageAsync(messages, participant.Id, cancellationToken).AsTask());
+        }
+
+        return sendTasks is null ? default : new ValueTask(Task.WhenAll(sendTasks));
+    }
+
+    private async ValueTask CompleteAsync(IWorkflowContext context, CancellationToken cancellationToken)
+    {
+        List<ChatMessage> output = this._history;
+        this._history = [];
+        this._currentSpeakerExecutorId = null;
+        this._manager = null;
+
+        await context.YieldOutputAsync(output, cancellationToken).ConfigureAwait(false);
+    }
+
     protected override ValueTask ResetAsync()
     {
         this._manager = null;
+        this._history = [];
+        this._currentSpeakerExecutorId = null;
 
         return base.ResetAsync();
     }
 
     ValueTask IResettableExecutor.ResetAsync() => this.ResetAsync();
+
+    protected internal override async ValueTask OnCheckpointingAsync(IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        Task historyTask = context.QueueStateUpdateAsync(HistoryStateKey, this._history, cancellationToken: cancellationToken).AsTask();
+        Task currentSpeakerTask = context.QueueStateUpdateAsync(CurrentSpeakerStateKey, this._currentSpeakerExecutorId, cancellationToken: cancellationToken).AsTask();
+        Task baseTask = base.OnCheckpointingAsync(context, cancellationToken).AsTask();
+
+        // Eagerly materialize the manager so subclass state (e.g., the round-robin cursor) gets
+        // persisted on every checkpoint, even if no turn has been taken yet since the host was constructed.
+        this._manager ??= this._managerFactory(this._agents);
+        Task managerTask = this._manager.CheckpointAsync(context, cancellationToken).AsTask();
+
+        await Task.WhenAll(historyTask, currentSpeakerTask, baseTask, managerTask).ConfigureAwait(false);
+    }
+
+    protected internal override async ValueTask OnCheckpointRestoredAsync(IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        this._history = await context.ReadStateAsync<List<ChatMessage>>(HistoryStateKey, cancellationToken: cancellationToken).ConfigureAwait(false) ?? [];
+        this._currentSpeakerExecutorId = await context.ReadStateAsync<string?>(CurrentSpeakerStateKey, cancellationToken: cancellationToken).ConfigureAwait(false);
+
+        // Instantiate the manager eagerly so its restore hook can rehydrate IterationCount and any
+        // subclass-defined state (e.g., RoundRobinGroupChatManager._nextIndex).
+        this._manager = this._managerFactory(this._agents);
+        await this._manager.RestoreCheckpointAsync(context, cancellationToken).ConfigureAwait(false);
+
+        await base.OnCheckpointRestoredAsync(context, cancellationToken).ConfigureAwait(false);
+    }
 }

dotnet/src/Microsoft.Agents.AI.Workflows/Specialized/HandoffAgentExecutor.cs

@@ -81,7 +81,6 @@ internal sealed record StateRef<TState>(string Key, string? ScopeName)
 }
 
 /// <summary>Executor used to represent an agent in a handoffs workflow, responding to <see cref="HandoffState"/> events.</summary>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 internal sealed class HandoffAgentExecutor :
     StatefulExecutor<HandoffAgentHostState, HandoffState>
 {

dotnet/src/Microsoft.Agents.AI.Workflows/Specialized/HandoffMessagesFilter.cs

@@ -2,12 +2,10 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using Microsoft.Extensions.AI;
 
 namespace Microsoft.Agents.AI.Workflows.Specialized;
 
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 internal sealed class HandoffMessagesFilter
 {
     private readonly HandoffToolCallFilteringBehavior _filteringBehavior;
@@ -17,7 +15,6 @@ internal sealed class HandoffMessagesFilter
         this._filteringBehavior = filteringBehavior;
     }
 
-    [Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
     internal static bool IsHandoffFunctionName(string name)
     {
         return name.StartsWith(HandoffWorkflowBuilder.FunctionPrefix, StringComparison.Ordinal);

dotnet/src/Microsoft.Agents.AI.Workflows/Specialized/Magentic/MagenticOrchestrator.cs

@@ -2,7 +2,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Text.Json.Serialization;
 using System.Threading;
@@ -18,7 +17,6 @@ namespace Microsoft.Agents.AI.Workflows.Specialized.Magentic;
 [JsonDerivedType(typeof(MagenticPlanCreatedEvent))]
 [JsonDerivedType(typeof(MagenticReplannedEvent))]
 [JsonDerivedType(typeof(MagenticProgressLedgerUpdatedEvent))]
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 public abstract class MagenticOrchestratorEvent(object? data) : WorkflowEvent(data)
 {
 }
@@ -27,7 +25,6 @@ public abstract class MagenticOrchestratorEvent(object? data) : WorkflowEvent(da
 /// Represents the creation of the initial plan
 /// </summary>
 /// <param name="fullTaskLeger"></param>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 public sealed class MagenticPlanCreatedEvent(ChatMessage fullTaskLeger) : MagenticOrchestratorEvent(fullTaskLeger)
 {
     /// <summary>
@@ -40,7 +37,6 @@ public sealed class MagenticPlanCreatedEvent(ChatMessage fullTaskLeger) : Magent
 /// Represents the creation of a new plan in response to a stall.
 /// </summary>
 /// <param name="fullTaskLeger"></param>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 public sealed class MagenticReplannedEvent(ChatMessage fullTaskLeger) : MagenticOrchestratorEvent(fullTaskLeger)
 {
     /// <summary>
@@ -53,7 +49,6 @@ public sealed class MagenticReplannedEvent(ChatMessage fullTaskLeger) : Magentic
 /// Represents an update to the <see cref="MagenticProgressLedger"/> when running a coordination round.
 /// </summary>
 /// <param name="progressLedger"></param>
-[Experimental(DiagnosticConstants.ExperimentalFeatureDiagnostic)]
 public sealed class MagenticProgressLedgerUpdatedEvent(MagenticProgressLedger progressLedger) : MagenticOrchestratorEvent(progressLedger)
 {
     /// <summary>
@@ -138,7 +133,6 @@ internal class MagenticOrchestrator(AIAgent managerAgent, List<AIAgent> team, Ta
           to the conversation and enters the inner loop.
         - If revision requested, append the review comments to the chat history,
           trigger replanning via the manager, emit a REPLANNED event, then run the outer loop.
-         
          */
         if (this._taskContext == null || this._taskContext.TaskLedger == null)
         {
@@ -201,7 +195,12 @@ internal class MagenticOrchestrator(AIAgent managerAgent, List<AIAgent> team, Ta
         }
         else
         {
-            // Subsequent turns: agent returned control, go directly to coordination (progress ledger only, no replan)
+            // Subsequent turns: agent returned control, go directly to coordination (progress ledger only, no replan).
+            // Capture the participant's reply into the manager-visible chat history so the progress ledger can see it.
+            if (messages is { Count: > 0 })
+            {
+                this._taskContext.ChatHistory.AddRange(messages);
+            }
             await this.RunCoordinationRoundAsync(this._taskContext, context, cancellationToken).ConfigureAwait(false);
         }
     }

dotnet/src/Microsoft.Agents.AI.Workflows/Workflow.cs

@@ -24,7 +24,7 @@ public class Workflow
     internal Dictionary<string, ExecutorBinding> ExecutorBindings { get; init; } = [];
 
     internal Dictionary<string, HashSet<Edge>> Edges { get; init; } = [];
-    internal HashSet<string> OutputExecutors { get; init; } = [];
+    internal Dictionary<string, HashSet<OutputTag>> OutputExecutors { get; init; } = new(StringComparer.Ordinal);
 
     /// <summary>
     /// Gets the collection of edges grouped by their source node identifier.
@@ -221,7 +221,7 @@ public class Workflow
         startExecutor.AttachRequestContext(new NoOpExternalRequestContext());
 
         ProtocolDescriptor inputProtocol = startExecutor.DescribeProtocol();
-        IEnumerable<Task<Executor>> outputExecutorTasks = this.OutputExecutors.Select(executorId => this.ExecutorBindings[executorId].CreateInstanceAsync(string.Empty).AsTask());
+        IEnumerable<Task<Executor>> outputExecutorTasks = this.OutputExecutors.Keys.Select(executorId => this.ExecutorBindings[executorId].CreateInstanceAsync(string.Empty).AsTask());
 
         Executor[] outputExecutors = await Task.WhenAll(outputExecutorTasks).ConfigureAwait(false);
         IEnumerable<Type> yieldedTypes = outputExecutors.SelectMany(executor => executor.DescribeProtocol().Yields);

dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowBuilder.cs

@@ -33,7 +33,7 @@ public class WorkflowBuilder
     private readonly HashSet<string> _unboundExecutors = [];
     private readonly HashSet<EdgeConnection> _conditionlessConnections = [];
     private readonly Dictionary<string, RequestPort> _requestPorts = [];
-    private readonly HashSet<string> _outputExecutors = [];
+    private readonly Dictionary<string, HashSet<OutputTag>> _outputExecutors = new(StringComparer.Ordinal);
 
     private readonly string _startExecutorId;
     private string? _name;
@@ -97,22 +97,89 @@ public class WorkflowBuilder
     }
 
     /// <summary>
-    /// Register executors as an output source. Executors can use <see cref="IWorkflowContext.YieldOutputAsync"/> to yield output values.
-    /// By default, message handlers with a non-void return type will also be yielded, unless <see cref="ExecutorOptions.AutoYieldOutputHandlerResultObject"/>
-    /// is set to <see langword="false"/>.
+    /// Register executors as a source of terminal workflow outputs. Executors can use
+    /// <see cref="IWorkflowContext.YieldOutputAsync"/> to yield output values; yielded values from
+    /// registered executors are surfaced as <see cref="WorkflowOutputEvent"/> (or one of its
+    /// subclasses) with an empty <see cref="WorkflowOutputEvent.Tags"/> set.
+    /// By default, message handlers with a non-void return type will also be yielded, unless
+    /// <see cref="ExecutorOptions.AutoYieldOutputHandlerResultObject"/> is set to <see langword="false"/>.
     /// </summary>
-    /// <param name="executors"></param>
-    /// <returns></returns>
+    /// <remarks>
+    /// AIAgent payloads (<see cref="AgentResponse"/> / <see cref="AgentResponseUpdate"/>) only
+    /// participate in this designation when
+    /// <see cref="Futures.EnableAgentResponseOutputTaggingAndFiltering"/> is
+    /// <see langword="true"/>; otherwise they are emitted unconditionally and untagged.
+    /// </remarks>
+    /// <param name="executors">The executors to register as output sources.</param>
+    /// <returns>The current <see cref="WorkflowBuilder"/> instance, enabling fluent configuration.</returns>
     public WorkflowBuilder WithOutputFrom(params ExecutorBinding[] executors)
     {
         foreach (ExecutorBinding executor in executors)
         {
-            this._outputExecutors.Add(this.Track(executor).Id);
+            this.EnsureOutputExecutor(this.Track(executor).Id);
         }
 
         return this;
     }
 
+    /// <summary>
+    /// Register executors as a source of workflow outputs carrying the given <paramref name="tag"/>.
+    /// Tags accumulate across repeated calls; the registered id always exists with the union of all
+    /// tags applied across all calls (and an empty set if only the untagged
+    /// <see cref="WithOutputFrom(ExecutorBinding[])"/> overload was used).
+    /// </summary>
+    /// <remarks>
+    /// Forward-looking surface for when the <see cref="OutputTag"/> constructor opens to
+    /// user-defined tags. Today, prefer
+    /// <see cref="WorkflowBuilderExtensions.WithIntermediateOutputFrom(WorkflowBuilder, IEnumerable{ExecutorBinding})"/>
+    /// for the <see cref="OutputTag.Intermediate"/> case.
+    /// </remarks>
+    /// <param name="executors">The executors to register.</param>
+    /// <param name="tag">The tag to apply to events yielded by the listed executors.</param>
+    /// <returns>The current <see cref="WorkflowBuilder"/> instance, enabling fluent configuration.</returns>
+    public WorkflowBuilder WithOutputFrom(IEnumerable<ExecutorBinding> executors, OutputTag tag)
+    {
+        Throw.IfNull(executors);
+
+        foreach (ExecutorBinding executor in executors)
+        {
+            this.EnsureOutputExecutor(this.Track(executor).Id).Add(tag);
+        }
+
+        return this;
+    }
+
+    /// <summary>
+    /// Register a single executor as a source of workflow outputs carrying the given <paramref name="tag"/>.
+    /// Convenience overload for the single-executor case; equivalent to passing a one-element sequence
+    /// to <see cref="WithOutputFrom(IEnumerable{ExecutorBinding}, OutputTag)"/>.
+    /// </summary>
+    /// <param name="executor">The executor to register.</param>
+    /// <param name="tag">The tag to apply to events yielded by the executor.</param>
+    /// <returns>The current <see cref="WorkflowBuilder"/> instance, enabling fluent configuration.</returns>
+    public WorkflowBuilder WithOutputFrom(ExecutorBinding executor, OutputTag tag)
+    {
+        Throw.IfNull(executor);
+
+        this.EnsureOutputExecutor(this.Track(executor).Id).Add(tag);
+
+        return this;
+    }
+
+    /// <summary>
+    /// Ensures the executor id is present in <see cref="_outputExecutors"/>; if newly added,
+    /// initializes with an empty tag set. Returns the tag set for the id (mutable).
+    /// </summary>
+    private HashSet<OutputTag> EnsureOutputExecutor(string executorId)
+    {
+        if (!this._outputExecutors.TryGetValue(executorId, out HashSet<OutputTag>? tags))
+        {
+            tags = [];
+            this._outputExecutors[executorId] = tags;
+        }
+        return tags;
+    }
+
     /// <summary>
     /// Sets the human-readable name for the workflow.
     /// </summary>

dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowBuilderExtensions.cs

@@ -211,4 +211,28 @@ public static class WorkflowBuilderExtensions
 
         return switchBuilder.ReduceToFanOut(builder, source);
     }
+
+    /// <summary>
+    /// Register executors as a source of <b>intermediate</b> workflow outputs. The resulting
+    /// <see cref="WorkflowOutputEvent"/>s carry <see cref="OutputTag.Intermediate"/> in their
+    /// <see cref="WorkflowOutputEvent.Tags"/> set, and
+    /// <see cref="WorkflowOutputEventExtensions.IsIntermediate(WorkflowOutputEvent)"/> returns
+    /// <see langword="true"/>. Use this for progress updates, partial results, and other
+    /// non-terminal emissions that downstream consumers (DevUI, logging, Workflow-as-Agent
+    /// surfaces) should see distinctly from the workflow's final output.
+    /// </summary>
+    /// <remarks>
+    /// AIAgent payloads (<see cref="AgentResponse"/> / <see cref="AgentResponseUpdate"/>) only
+    /// participate in this designation when
+    /// <see cref="Futures.EnableAgentResponseOutputTaggingAndFiltering"/> is
+    /// <see langword="true"/>; otherwise they bypass the filter and are emitted untagged.
+    /// </remarks>
+    /// <param name="builder">The workflow builder to register executors on.</param>
+    /// <param name="executors">The executors to register as intermediate output sources.</param>
+    /// <returns>The <paramref name="builder"/>, enabling fluent configuration.</returns>
+    public static WorkflowBuilder WithIntermediateOutputFrom(this WorkflowBuilder builder, IEnumerable<ExecutorBinding> executors)
+    {
+        Throw.IfNull(builder);
+        return builder.WithOutputFrom(executors, OutputTag.Intermediate);
+    }
 }

dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowOutputEvent.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Text.Json.Serialization;
 
@@ -13,14 +14,39 @@ namespace Microsoft.Agents.AI.Workflows;
 [JsonDerivedType(typeof(AgentResponseUpdateEvent))]
 public class WorkflowOutputEvent : WorkflowEvent
 {
+    private readonly HashSet<OutputTag> _tags;
+
     /// <summary>
-    /// Initializes a new instance of the <see cref="WorkflowOutputEvent"/> class.
+    /// Initializes a new instance of the <see cref="WorkflowOutputEvent"/> class with no tags.
     /// </summary>
     /// <param name="data">The output data.</param>
     /// <param name="executorId">The identifier of the executor that yielded this output.</param>
-    public WorkflowOutputEvent(object data, string executorId) : base(data)
+    public WorkflowOutputEvent(object data, string executorId) : this(data, executorId, tags: null)
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="WorkflowOutputEvent"/> class carrying the
+    /// given output tag.
+    /// </summary>
+    /// <param name="data">The output data.</param>
+    /// <param name="executorId">The identifier of the executor that yielded this output.</param>
+    /// <param name="tag">The single output tag to associate with this event.</param>
+    public WorkflowOutputEvent(object data, string executorId, OutputTag tag) : this(data, executorId, tags: new[] { tag })
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="WorkflowOutputEvent"/> class carrying the
+    /// given output tags (deduplicated).
+    /// </summary>
+    /// <param name="data">The output data.</param>
+    /// <param name="executorId">The identifier of the executor that yielded this output.</param>
+    /// <param name="tags">The output tags to associate with this event. May be <see langword="null"/> or empty (the event is then untagged).</param>
+    public WorkflowOutputEvent(object data, string executorId, IEnumerable<OutputTag>? tags) : base(data)
     {
         this.ExecutorId = executorId;
+        this._tags = tags is null ? new HashSet<OutputTag>() : new HashSet<OutputTag>(tags);
     }
 
     /// <summary>
@@ -32,8 +58,21 @@ public class WorkflowOutputEvent : WorkflowEvent
     /// The unique identifier of the executor that yielded this output.
     /// </summary>
     [Obsolete("Use ExecutorId instead.")]
+    [JsonIgnore]
     public string SourceId => this.ExecutorId;
 
+    /// <summary>
+    /// The set of output tags associated with this event. Never <see langword="null"/>;
+    /// empty for terminal/regular outputs. The presence of <see cref="OutputTag.Intermediate"/>
+    /// marks this event as an intermediate output.
+    /// </summary>
+    public IEnumerable<OutputTag> Tags => this._tags;
+
+    /// <summary>
+    /// Returns <see langword="true"/> if this event carries the given tag.
+    /// </summary>
+    public bool HasTag(OutputTag tag) => this._tags.Contains(tag);
+
     /// <summary>
     /// Determines whether the underlying data is of the specified type or a derived type.
     /// </summary>

dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowOutputEventExtensions.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Microsoft.Shared.Diagnostics;
+
+namespace Microsoft.Agents.AI.Workflows;
+
+/// <summary>
+/// Extension helpers for inspecting <see cref="WorkflowOutputEvent"/> tag membership.
+/// </summary>
+public static class WorkflowOutputEventExtensions
+{
+    /// <summary>
+    /// Returns <see langword="true"/> if the event carries
+    /// <see cref="OutputTag.Intermediate"/> in its <see cref="WorkflowOutputEvent.Tags"/>.
+    /// </summary>
+    public static bool IsIntermediate(this WorkflowOutputEvent evt)
+    {
+        Throw.IfNull(evt);
+        return evt.HasTag(OutputTag.Intermediate);
+    }
+}

dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowSession.cs

@@ -520,11 +520,20 @@ internal sealed class WorkflowSession : AgentSession
                     goto default;
 
                 case AgentResponseEvent agentResponse:
-                    if (!this._includeWorkflowOutputsInResponse)
+                    // Under Futures.EnableAgentResponseOutputTaggingAndFiltering=true, mirror
+                    // AgentResponseUpdateEvent's behavior: always forward, regardless of the
+                    // _includeWorkflowOutputsInResponse host flag / "intermediate" tag. Under
+                    // the legacy default, keep today's behavior — gated by the include flag.
+                    if (!Futures.EnableAgentResponseOutputTaggingAndFiltering && !this._includeWorkflowOutputsInResponse)
                     {
                         goto default;
                     }
 
+                    // Either EnableAgentResponseOutputTaggingAndFiltering -- so yield the Response
+                    // regardless of whether it is tagged "intermediate" or whether the
+                    // _includeWorkflowOutputInResponse flag is set. Reason being: The user specifies
+                    // exclusion of an event by enabling filtering and then _not_ marking an Executor
+                    // as an output executor.
                     foreach (ChatMessage message in agentResponse.Response.Messages)
                     {
                         yield return this.CreateUpdate(this.LastResponseId, evt, message);
@@ -539,7 +548,11 @@ internal sealed class WorkflowSession : AgentSession
                         _ => null
                     };
 
-                    if (!this._includeWorkflowOutputsInResponse || updateMessages == null)
+                    // Same assymetry as with AgentResponseEvent, but there is no EnableFiltering flag
+                    // to consider. If this made it here (and since it is not an AgentResponse[Update]),
+                    // it means it is already been selected as an Output() from the user. Intermediate
+                    // is irrelevant here.
+                    if (updateMessages == null || !this._includeWorkflowOutputsInResponse)
                     {
                         goto default;
                     }

dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowsJsonUtilities.cs

@@ -80,9 +80,8 @@ internal static partial class WorkflowsJsonUtilities
     [JsonSerializable(typeof(ExecutorIdentity))]
     [JsonSerializable(typeof(RunnerStateData))]
 
-    // Workflow Representation Types
-    [JsonSerializable(typeof(WorkflowInfo))]
-    [JsonSerializable(typeof(EdgeConnection))]
+    // Workflow Output Types
+    [JsonSerializable(typeof(OutputTag))]
 
     // Workflow-as-Agent
     [JsonSerializable(typeof(WorkflowChatHistoryProvider.StoreState))]
@@ -101,6 +100,8 @@ internal static partial class WorkflowsJsonUtilities
     [JsonSerializable(typeof(MagenticPlanReviewRequest))]
     [JsonSerializable(typeof(MagenticPlanReviewResponse))]
     [JsonSerializable(typeof(MagenticTaskState))]
+    [JsonSerializable(typeof(GroupChatManagerState))]
+    [JsonSerializable(typeof(RoundRobinGroupChatManagerState))]
     [JsonSerializable(typeof(ResetChatSignal))]
 
     // Event Types

dotnet/tests/Microsoft.Agents.AI.Abstractions.UnitTests/AgentResponseTests.cs

@@ -222,6 +222,42 @@ public class AgentResponseTests
         Assert.Equal(100, usageContent.Details.TotalTokenCount);
     }
 
+    [Fact]
+    public void ToAgentResponseUpdatesPropagatesCreatedAt()
+    {
+        // Sets different CreatedAt values on the AgentResponse and the ChatMessage to verify that the ChatMessage.CreatedAt is the one that gets propagated to the AgentResponseUpdate
+        AgentResponse response = new(new ChatMessage(new ChatRole("customRole"), "Text") { MessageId = "someMessage", CreatedAt = new DateTimeOffset(2024, 11, 11, 9, 20, 0, TimeSpan.Zero) })
+        {
+            AgentId = "agentId",
+            ResponseId = "12345",
+            CreatedAt = new DateTimeOffset(2024, 11, 10, 9, 20, 0, TimeSpan.Zero),
+            AdditionalProperties = new() { ["key1"] = "value1", ["key2"] = 42 },
+            Usage = new UsageDetails
+            {
+                TotalTokenCount = 100
+            },
+        };
+
+        AgentResponseUpdate[] updates = response.ToAgentResponseUpdates();
+        Assert.NotNull(updates);
+        Assert.Equal(2, updates.Length);
+
+        AgentResponseUpdate update0 = updates[0];
+        Assert.Equal("agentId", update0.AgentId);
+        Assert.Equal("12345", update0.ResponseId);
+        Assert.Equal("someMessage", update0.MessageId);
+        Assert.Equal(new DateTimeOffset(2024, 11, 11, 9, 20, 0, TimeSpan.Zero), update0.CreatedAt);
+        Assert.Equal("customRole", update0.Role?.Value);
+        Assert.Equal("Text", update0.Text);
+
+        AgentResponseUpdate update1 = updates[1];
+        Assert.Equal("value1", update1.AdditionalProperties?["key1"]);
+        Assert.Equal(42, update1.AdditionalProperties?["key2"]);
+        Assert.IsType<UsageContent>(update1.Contents[0]);
+        UsageContent usageContent = (UsageContent)update1.Contents[0];
+        Assert.Equal(100, usageContent.Details.TotalTokenCount);
+    }
+
     [Fact]
     public void ParseAsStructuredOutputWithJSOSuccess()
     {

dotnet/tests/Microsoft.Agents.AI.DevUI.UnitTests/DevUIIntegrationTests.cs

@@ -172,7 +172,7 @@ public class DevUIIntegrationTests
         Assert.Contains(discoveryResponse.Entities, e => e.Name == "workflow-three" && e.Type == "workflow");
     }
 
-    [Fact]
+    [Fact(Skip = "Flaky in merge_group; see https://github.com/microsoft/agent-framework/issues/5845")]
     public async Task TestServerWithDevUI_ResolvesWorkflows_WithKeyedAndDefaultRegistrationAsync()
     {
         // Arrange

dotnet/tests/Microsoft.Agents.AI.Foundry.Hosting.UnitTests/OutputConverterTests.cs

@@ -704,6 +704,35 @@ public class OutputConverterTests
         Assert.Equal("[{\"id\":1}]", inner);
     }
 
+    // K-06e: Regression — the OutputItemFunctionToolCallOutput must have a populated Id
+    // and a matching wire id on the added/done events. The Foundry storage layer extracts
+    // a partition id from this field and throws "ID cannot be null or empty (Parameter 'id')"
+    // when it is missing.
+    [Fact]
+    public async Task ConvertUpdatesToEventsAsync_FunctionResult_OutputItemHasIdAsync()
+    {
+        var (stream, _) = CreateTestStream();
+        var update = new AgentResponseUpdate { Contents = [new FunctionResultContent("call_1", "sunny")] };
+
+        var events = new List<ResponseStreamEvent>();
+        await foreach (var evt in OutputConverter.ConvertUpdatesToEventsAsync(ToAsync(new[] { update }), stream))
+        {
+            events.Add(evt);
+        }
+
+        var added = Assert.Single(events.OfType<ResponseOutputItemAddedEvent>());
+        var done = Assert.Single(events.OfType<ResponseOutputItemDoneEvent>());
+
+        var addedOutput = Assert.IsType<OutputItemFunctionToolCallOutput>(added.Item);
+        var doneOutput = Assert.IsType<OutputItemFunctionToolCallOutput>(done.Item);
+
+        Assert.False(string.IsNullOrEmpty(addedOutput.Id));
+        Assert.False(string.IsNullOrEmpty(doneOutput.Id));
+        Assert.Equal(addedOutput.Id, doneOutput.Id);
+        Assert.Equal("call_1", addedOutput.CallId);
+        Assert.Equal("call_1", doneOutput.CallId);
+    }
+
     // L-01
     [Fact]
     public async Task ConvertUpdatesToEventsAsync_ExecutorInvokedEvent_EmitsWorkflowActionItemAsync()

dotnet/tests/Microsoft.Agents.AI.Foundry.UnitTests/Microsoft.Agents.AI.Foundry.UnitTests.csproj

@@ -8,6 +8,8 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Logging" />
     <PackageReference Include="Azure.AI.Projects" />
+    <PackageReference Include="Azure.Core" />
+    <PackageReference Include="System.ClientModel" />
   </ItemGroup>
 
   <ItemGroup>

dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.UnitTests/ObjectModel/InvokeMcpToolExecutorTest.cs

@@ -1,9 +1,11 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Agents.AI.Workflows.Declarative.Events;
+using Microsoft.Agents.AI.Workflows.Declarative.Interpreter;
 using Microsoft.Agents.AI.Workflows.Declarative.Kit;
 using Microsoft.Agents.AI.Workflows.Declarative.ObjectModel;
 using Microsoft.Agents.AI.Workflows.Declarative.PowerFx;
@@ -290,6 +292,151 @@ public sealed class InvokeMcpToolExecutorTest(ITestOutputHelper output) : Workfl
         await this.ExecuteTestAsync(model);
     }
 
+    [Fact]
+    public async Task InvokeMcpToolApprovalRequestExcludesTransportHeadersAsync()
+    {
+        // Arrange
+        this.State.InitializeSystem();
+        InvokeMcpTool model = this.CreateModel(
+            displayName: nameof(InvokeMcpToolApprovalRequestExcludesTransportHeadersAsync),
+            serverUrl: TestServerUrl,
+            serverLabel: TestServerLabel,
+            toolName: TestToolName,
+            requireApproval: true,
+            headerKey: "Authorization",
+            headerValue: "Bearer super-secret-token");
+        MockMcpToolProvider mockProvider = new();
+        MockAgentProvider mockAgentProvider = new();
+        InvokeMcpToolExecutor action = new(model, mockProvider.Object, mockAgentProvider.Object, this.State);
+
+        ExternalInputRequest? capturedRequest = null;
+
+        // Act
+        await this.ExecuteAsync(
+            [
+                action,
+                new DelegateActionExecutor<ExternalInputRequest>(
+                    InvokeMcpToolExecutor.Steps.ExternalInput(action.Id),
+                    this.State,
+                    CaptureRequestAsync)
+            ],
+            isDiscrete: false);
+
+        // Assert - the approval event must not carry any transport headers (e.g. Authorization).
+        Assert.NotNull(capturedRequest);
+        ToolApprovalRequestContent approvalRequest =
+            capturedRequest!.AgentResponse.Messages
+                .SelectMany(message => message.Contents)
+                .OfType<ToolApprovalRequestContent>()
+                .Single();
+
+        AdditionalPropertiesDictionary? additionalProperties = approvalRequest.ToolCall.AdditionalProperties;
+        Assert.True(additionalProperties is null || additionalProperties.Count == 0);
+
+        // Defense in depth: the credential value must not appear anywhere in the serialized approval content.
+        string serializedApproval = System.Text.Json.JsonSerializer.Serialize(capturedRequest.AgentResponse);
+        Assert.DoesNotContain("super-secret-token", serializedApproval);
+
+        ValueTask CaptureRequestAsync(IWorkflowContext context, ExternalInputRequest request, CancellationToken cancellationToken)
+        {
+            capturedRequest = request;
+            return default;
+        }
+    }
+
+    [Fact]
+    public async Task InvokeMcpToolInvocationForwardsHeadersToTransportAsync()
+    {
+        // Arrange
+        this.State.InitializeSystem();
+        const string HeaderKey = "Authorization";
+        const string HeaderValue = "Bearer super-secret-token";
+        InvokeMcpTool model = this.CreateModel(
+            displayName: nameof(InvokeMcpToolInvocationForwardsHeadersToTransportAsync),
+            serverUrl: TestServerUrl,
+            serverLabel: TestServerLabel,
+            toolName: TestToolName,
+            requireApproval: false,
+            headerKey: HeaderKey,
+            headerValue: HeaderValue);
+
+        IDictionary<string, string>? capturedHeaders = null;
+        Mock<IMcpToolHandler> mockProvider = new();
+        mockProvider
+            .Setup(provider => provider.InvokeToolAsync(
+                It.IsAny<string>(),
+                It.IsAny<string?>(),
+                It.IsAny<string>(),
+                It.IsAny<IDictionary<string, object?>?>(),
+                It.IsAny<IDictionary<string, string>?>(),
+                It.IsAny<string?>(),
+                It.IsAny<CancellationToken>()))
+            .Callback<string, string?, string, IDictionary<string, object?>?, IDictionary<string, string>?, string?, CancellationToken>(
+                (_, _, _, _, headers, _, _) => capturedHeaders = headers)
+            .ReturnsAsync(new McpServerToolResultContent("mock-call-id") { Outputs = [new TextContent("ok")] });
+        MockAgentProvider mockAgentProvider = new();
+        InvokeMcpToolExecutor action = new(model, mockProvider.Object, mockAgentProvider.Object, this.State);
+
+        // Act
+        await this.ExecuteAsync(action, isDiscrete: false);
+
+        // Assert - headers remain available to the actual transport invocation.
+        Assert.NotNull(capturedHeaders);
+        Assert.True(capturedHeaders!.TryGetValue(HeaderKey, out string? forwardedValue));
+        Assert.Equal(HeaderValue, forwardedValue);
+    }
+
+    [Fact]
+    public async Task InvokeMcpToolApprovedCaptureResponseForwardsHeadersToTransportAsync()
+    {
+        // Arrange - exercises the post-approval CaptureResponseAsync resume path to prove the
+        // fix did not regress header forwarding on the path that the vulnerability actually targets.
+        this.State.InitializeSystem();
+        const string HeaderKey = "Authorization";
+        const string HeaderValue = "Bearer super-secret-token";
+        InvokeMcpTool model = this.CreateModel(
+            displayName: nameof(InvokeMcpToolApprovedCaptureResponseForwardsHeadersToTransportAsync),
+            serverUrl: TestServerUrl,
+            serverLabel: TestServerLabel,
+            toolName: TestToolName,
+            requireApproval: true,
+            headerKey: HeaderKey,
+            headerValue: HeaderValue);
+
+        IDictionary<string, string>? capturedHeaders = null;
+        Mock<IMcpToolHandler> mockProvider = new();
+        mockProvider
+            .Setup(provider => provider.InvokeToolAsync(
+                It.IsAny<string>(),
+                It.IsAny<string?>(),
+                It.IsAny<string>(),
+                It.IsAny<IDictionary<string, object?>?>(),
+                It.IsAny<IDictionary<string, string>?>(),
+                It.IsAny<string?>(),
+                It.IsAny<CancellationToken>()))
+            .Callback<string, string?, string, IDictionary<string, object?>?, IDictionary<string, string>?, string?, CancellationToken>(
+                (_, _, _, _, headers, _, _) => capturedHeaders = headers)
+            .ReturnsAsync(new McpServerToolResultContent("mock-call-id") { Outputs = [new TextContent("ok")] });
+        MockAgentProvider mockAgentProvider = new();
+        InvokeMcpToolExecutor action = new(model, mockProvider.Object, mockAgentProvider.Object, this.State);
+
+        Mock<IWorkflowContext> mockContext = new(MockBehavior.Loose);
+
+        // Build an approved response matching this action's request id.
+        McpServerToolCallContent toolCall = new(action.Id, TestToolName, TestServerLabel);
+        ToolApprovalRequestContent approvalRequest = new(action.Id, toolCall);
+        ToolApprovalResponseContent approvalResponse = approvalRequest.CreateResponse(approved: true);
+        ExternalInputResponse response = new(new ChatMessage(ChatRole.User, [approvalResponse]));
+
+        // Act - call CaptureResponseAsync directly so the post-approval branch actually executes.
+        await action.CaptureResponseAsync(mockContext.Object, response, CancellationToken.None);
+
+        // Assert - headers reach the transport invocation on the approved path.
+        Assert.NotNull(capturedHeaders);
+        Assert.True(capturedHeaders!.TryGetValue(HeaderKey, out string? forwardedValue));
+        Assert.Equal(HeaderValue, forwardedValue);
+    }
+
     [Fact]
     public async Task InvokeMcpToolExecuteWithEmptyHeaderValueAsync()
     {

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/AgentWorkflowBuilderTests.cs

@@ -4,12 +4,9 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.CompilerServices;
-using System.Text;
-using System.Text.Json;
 using System.Text.RegularExpressions;
-using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.Agents.AI.Workflows.InProc;
+using FluentAssertions;
 using Microsoft.Extensions.AI;
 
 #pragma warning disable SYSLIB1045 // Use GeneratedRegex
@@ -17,325 +14,164 @@ using Microsoft.Extensions.AI;
 
 namespace Microsoft.Agents.AI.Workflows.UnitTests;
 
+/// <summary>
+/// Tests targeting the static <see cref="AgentWorkflowBuilder"/> helper surface —
+/// <see cref="AgentWorkflowBuilder.BuildSequential(IEnumerable{AIAgent})"/>,
+/// <see cref="AgentWorkflowBuilder.BuildConcurrent(IEnumerable{AIAgent}, Func{IList{List{ChatMessage}}, List{ChatMessage}})"/>,
+/// and the various <c>Create*BuilderWith</c> factories. Per-builder unit tests live in their own
+/// files (<see cref="SequentialWorkflowBuilderTests"/>, <see cref="ConcurrentWorkflowBuilderTests"/>, etc.).
+/// </summary>
 public class AgentWorkflowBuilderTests
 {
     [Fact]
-    public void BuildSequential_InvalidArguments_Throws()
+    public void Test_AgentWorkflowBuilder_BuildSequential_InvalidArguments_Throws()
     {
         Assert.Throws<ArgumentNullException>("agents", () => AgentWorkflowBuilder.BuildSequential(workflowName: null!, null!));
         Assert.Throws<ArgumentException>("agents", () => AgentWorkflowBuilder.BuildSequential());
     }
 
+    [Theory]
+    [InlineData(1)]
+    [InlineData(2)]
+    [InlineData(3)]
+    public async Task Test_AgentWorkflowBuilder_BuildSequential_DelegatesToBuilderAsync(int numAgents)
+    {
+        Workflow workflow = AgentWorkflowBuilder.BuildSequential(
+            from i in Enumerable.Range(1, numAgents)
+            select new OrchestrationTestHelpers.DoubleEchoAgent($"agent{i}"));
+
+        // Smoke: end-to-end run produces a non-empty result. Detailed pipeline-ordering
+        // assertions live in SequentialWorkflowBuilderTests.
+        (string updateText, List<ChatMessage>? result, _, _) =
+            await OrchestrationTestHelpers.RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, "abc")]);
+
+        Assert.NotNull(result);
+        Assert.Equal(numAgents + 1, result.Count);
+        Assert.NotEmpty(updateText);
+    }
+
     [Fact]
-    public void BuildConcurrent_InvalidArguments_Throws()
+    public void Test_AgentWorkflowBuilder_BuildSequential_WithWorkflowNameSetsNameOnWorkflow()
+    {
+        Workflow workflow = AgentWorkflowBuilder.BuildSequential(
+            "static-sequential",
+            new OrchestrationTestHelpers.DoubleEchoAgent("agent1"));
+
+        workflow.Name.Should().Be("static-sequential");
+    }
+
+    [Fact]
+    public void Test_AgentWorkflowBuilder_BuildConcurrent_InvalidArguments_Throws()
     {
         Assert.Throws<ArgumentNullException>("agents", () => AgentWorkflowBuilder.BuildConcurrent(null!));
     }
 
     [Fact]
-    public void BuildGroupChat_InvalidArguments_Throws()
-    {
-        Assert.Throws<ArgumentNullException>("managerFactory", () => AgentWorkflowBuilder.CreateGroupChatBuilderWith(null!));
-
-        var groupChat = AgentWorkflowBuilder.CreateGroupChatBuilderWith(_ => new RoundRobinGroupChatManager([new DoubleEchoAgent("a1")]));
-        Assert.NotNull(groupChat);
-        Assert.Throws<ArgumentNullException>("agents", () => groupChat.AddParticipants(null!));
-        Assert.Throws<ArgumentNullException>("agents", () => groupChat.AddParticipants([null!]));
-        Assert.Throws<ArgumentNullException>("agents", () => groupChat.AddParticipants(new DoubleEchoAgent("a1"), null!));
-
-        Assert.Throws<ArgumentNullException>("agents", () => new RoundRobinGroupChatManager(null!));
-    }
-
-    [Fact]
-    public void GroupChatManager_MaximumIterationCount_Invalid_Throws()
-    {
-        var manager = new RoundRobinGroupChatManager([new DoubleEchoAgent("a1")]);
-
-        const int DefaultMaxIterations = 40;
-        Assert.Equal(DefaultMaxIterations, manager.MaximumIterationCount);
-        Assert.Throws<ArgumentOutOfRangeException>("value", void () => manager.MaximumIterationCount = 0);
-        Assert.Throws<ArgumentOutOfRangeException>("value", void () => manager.MaximumIterationCount = -1);
-        Assert.Equal(DefaultMaxIterations, manager.MaximumIterationCount);
-
-        manager.MaximumIterationCount = 30;
-        Assert.Equal(30, manager.MaximumIterationCount);
-
-        manager.MaximumIterationCount = 1;
-        Assert.Equal(1, manager.MaximumIterationCount);
-
-        manager.MaximumIterationCount = int.MaxValue;
-        Assert.Equal(int.MaxValue, manager.MaximumIterationCount);
-    }
-
-    [Fact]
-    public void BuildGroupChat_WithNameAndDescription_SetsWorkflowNameAndDescription()
-    {
-        const string WorkflowName = "Test Group Chat";
-        const string WorkflowDescription = "A test group chat workflow";
-
-        var workflow = AgentWorkflowBuilder
-            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 2 })
-            .AddParticipants(new DoubleEchoAgent("agent1"), new DoubleEchoAgent("agent2"))
-            .WithName(WorkflowName)
-            .WithDescription(WorkflowDescription)
-            .Build();
-
-        Assert.Equal(WorkflowName, workflow.Name);
-        Assert.Equal(WorkflowDescription, workflow.Description);
-    }
-
-    [Fact]
-    public void BuildGroupChat_WithNameOnly_SetsWorkflowName()
-    {
-        const string WorkflowName = "Named Group Chat";
-
-        var workflow = AgentWorkflowBuilder
-            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 2 })
-            .AddParticipants(new DoubleEchoAgent("agent1"))
-            .WithName(WorkflowName)
-            .Build();
-
-        Assert.Equal(WorkflowName, workflow.Name);
-        Assert.Null(workflow.Description);
-    }
-
-    [Fact]
-    public void BuildGroupChat_WithoutNameOrDescription_DefaultsToNull()
-    {
-        var workflow = AgentWorkflowBuilder
-            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 2 })
-            .AddParticipants(new DoubleEchoAgent("agent1"))
-            .Build();
-
-        Assert.Null(workflow.Name);
-        Assert.Null(workflow.Description);
-    }
-
-    [Theory]
-    [InlineData(1)]
-    [InlineData(2)]
-    [InlineData(3)]
-    [InlineData(4)]
-    [InlineData(5)]
-    public async Task BuildSequential_AgentsRunInOrderAsync(int numAgents)
-    {
-        var workflow = AgentWorkflowBuilder.BuildSequential(
-            from i in Enumerable.Range(1, numAgents)
-            select new DoubleEchoAgent($"agent{i}"));
-
-        for (int iter = 0; iter < 3; iter++)
-        {
-            const string UserInput = "abc";
-            (string updateText, List<ChatMessage>? result, _, _) = await RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, UserInput)]);
-
-            Assert.NotNull(result);
-            Assert.Equal(numAgents + 1, result.Count);
-
-            Assert.Equal(ChatRole.User, result[0].Role);
-            Assert.Null(result[0].AuthorName);
-            Assert.Equal(UserInput, result[0].Text);
-
-            string[] texts = new string[numAgents + 1];
-            texts[0] = UserInput;
-            string expectedTotal = string.Empty;
-            for (int i = 1; i < numAgents + 1; i++)
-            {
-                string id = $"agent{((i - 1) % numAgents) + 1}";
-                texts[i] = $"{id}{Double(string.Concat(texts.Take(i)))}";
-                Assert.Equal(ChatRole.Assistant, result[i].Role);
-                Assert.Equal(id, result[i].AuthorName);
-                Assert.Equal(texts[i], result[i].Text);
-                expectedTotal += texts[i];
-            }
-
-            Assert.Equal(expectedTotal, updateText);
-            Assert.Equal(UserInput + expectedTotal, string.Concat(result));
-
-            static string Double(string s) => s + s;
-        }
-    }
-
-    private class DoubleEchoAgent(string name) : AIAgent
-    {
-        public override string Name => name;
-
-        protected override ValueTask<AgentSession> CreateSessionCoreAsync(CancellationToken cancellationToken = default)
-            => new(new DoubleEchoAgentSession());
-
-        protected override ValueTask<AgentSession> DeserializeSessionCoreAsync(JsonElement serializedState, JsonSerializerOptions? jsonSerializerOptions = null, CancellationToken cancellationToken = default)
-            => new(new DoubleEchoAgentSession());
-
-        protected override ValueTask<JsonElement> SerializeSessionCoreAsync(AgentSession session, JsonSerializerOptions? jsonSerializerOptions = null, CancellationToken cancellationToken = default)
-            => default;
-
-        protected override Task<AgentResponse> RunCoreAsync(
-            IEnumerable<ChatMessage> messages, AgentSession? session = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default) =>
-            throw new NotImplementedException();
-
-        protected override async IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingAsync(
-            IEnumerable<ChatMessage> messages, AgentSession? session = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
-        {
-            await Task.Yield();
-
-            var contents = messages.SelectMany(m => m.Contents).ToList();
-            string id = Guid.NewGuid().ToString("N");
-            yield return new AgentResponseUpdate(ChatRole.Assistant, this.Name) { AuthorName = this.Name, MessageId = id };
-            yield return new AgentResponseUpdate(ChatRole.Assistant, contents) { AuthorName = this.Name, MessageId = id };
-            yield return new AgentResponseUpdate(ChatRole.Assistant, contents) { AuthorName = this.Name, MessageId = id };
-        }
-    }
-
-    private sealed class DoubleEchoAgentSession() : AgentSession();
-
-    [Fact]
-    public async Task BuildConcurrent_AgentsRunInParallelAsync()
+    public async Task Test_AgentWorkflowBuilder_BuildConcurrent_DelegatesToBuilderAsync()
     {
         StrongBox<TaskCompletionSource<bool>> barrier = new();
         StrongBox<int> remaining = new();
 
-        var workflow = AgentWorkflowBuilder.BuildConcurrent(
+        Workflow workflow = AgentWorkflowBuilder.BuildConcurrent(
         [
-            new DoubleEchoAgentWithBarrier("agent1", barrier, remaining),
-            new DoubleEchoAgentWithBarrier("agent2", barrier, remaining),
+            new OrchestrationTestHelpers.DoubleEchoAgentWithBarrier("agent1", barrier, remaining),
+            new OrchestrationTestHelpers.DoubleEchoAgentWithBarrier("agent2", barrier, remaining),
         ]);
 
-        for (int iter = 0; iter < 3; iter++)
-        {
-            barrier.Value = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
-            remaining.Value = 2;
+        barrier.Value = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
+        remaining.Value = 2;
 
-            (string updateText, List<ChatMessage>? result, _, _) = await RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, "abc")]);
-            Assert.NotEmpty(updateText);
-            Assert.NotNull(result);
+        (string updateText, List<ChatMessage>? result, _, _) =
+            await OrchestrationTestHelpers.RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, "abc")]);
 
-            // TODO: https://github.com/microsoft/agent-framework/issues/784
-            // These asserts are flaky until we guarantee message delivery order.
-            Assert.Single(Regex.Matches(updateText, "agent1"));
-            Assert.Single(Regex.Matches(updateText, "agent2"));
-            Assert.Equal(4, Regex.Matches(updateText, "abc").Count);
-            Assert.Equal(2, result.Count);
-        }
+        Assert.NotEmpty(updateText);
+        Assert.NotNull(result);
+        Assert.Equal(2, result.Count);
+        Assert.Single(Regex.Matches(updateText, "agent1"));
+        Assert.Single(Regex.Matches(updateText, "agent2"));
     }
 
-    [Theory]
-    [InlineData(1)]
-    [InlineData(2)]
-    [InlineData(3)]
-    [InlineData(4)]
-    [InlineData(5)]
-    public async Task BuildGroupChat_AgentsRunInOrderAsync(int maxIterations)
+    [Fact]
+    public void Test_AgentWorkflowBuilder_BuildConcurrent_WithWorkflowNameSetsNameOnWorkflow()
     {
-        const int NumAgents = 3;
-        var workflow = AgentWorkflowBuilder.CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = maxIterations })
-            .AddParticipants(new DoubleEchoAgent("agent1"), new DoubleEchoAgent("agent2"))
-            .AddParticipants(new DoubleEchoAgent("agent3"))
-            .Build();
+        Workflow workflow = AgentWorkflowBuilder.BuildConcurrent(
+            "static-concurrent",
+            [new OrchestrationTestHelpers.DoubleEchoAgent("agent1")]);
 
-        for (int iter = 0; iter < 3; iter++)
-        {
-            const string UserInput = "abc";
-            (string updateText, List<ChatMessage>? result, _, _) = await RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, UserInput)]);
-
-            Assert.NotNull(result);
-            Assert.Equal(maxIterations + 1, result.Count);
-
-            Assert.Equal(ChatRole.User, result[0].Role);
-            Assert.Null(result[0].AuthorName);
-            Assert.Equal(UserInput, result[0].Text);
-
-            string[] texts = new string[maxIterations + 1];
-            texts[0] = UserInput;
-            string expectedTotal = string.Empty;
-            for (int i = 1; i < maxIterations + 1; i++)
-            {
-                string id = $"agent{((i - 1) % NumAgents) + 1}";
-                texts[i] = $"{id}{Double(string.Concat(texts.Take(i)))}";
-                Assert.Equal(ChatRole.Assistant, result[i].Role);
-                Assert.Equal(id, result[i].AuthorName);
-                Assert.Equal(texts[i], result[i].Text);
-                expectedTotal += texts[i];
-            }
-
-            Assert.Equal(expectedTotal, updateText);
-            Assert.Equal(UserInput + expectedTotal, string.Concat(result));
-
-            static string Double(string s) => s + s;
-        }
+        workflow.Name.Should().Be("static-concurrent");
     }
 
-    private sealed record WorkflowRunResult(string UpdateText, List<ChatMessage>? Result, CheckpointInfo? LastCheckpoint, List<RequestInfoEvent> PendingRequests);
-
-    private static async Task<WorkflowRunResult> RunWorkflowCheckpointedAsync(
-        Workflow workflow, List<ChatMessage> input, InProcessExecutionEnvironment environment, CheckpointInfo? fromCheckpoint = null)
+    [Fact]
+    public async Task Test_AgentWorkflowBuilder_BuildConcurrent_AggregatorIsHonoredAsync()
     {
-        await using StreamingRun run =
-            fromCheckpoint != null ? await environment.ResumeStreamingAsync(workflow, fromCheckpoint)
-                                   : await environment.OpenStreamingAsync(workflow);
+        // Replace the default ("last message from each agent") with a custom aggregator,
+        // and confirm the workflow yields its result.
+        List<ChatMessage> sentinel = [new(ChatRole.Assistant, "custom-aggregator-result")];
 
-        await run.TrySendMessageAsync(input);
-        await run.TrySendMessageAsync(new TurnToken(emitEvents: true));
+        Workflow workflow = AgentWorkflowBuilder.BuildConcurrent(
+            [new OrchestrationTestHelpers.DoubleEchoAgent("agent1")],
+            aggregator: _ => sentinel);
 
-        return await ProcessWorkflowRunAsync(run);
+        (_, List<ChatMessage>? result, _, _) =
+            await OrchestrationTestHelpers.RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, "abc")]);
+
+        result.Should().NotBeNull().And.ContainSingle();
+        result![0].Text.Should().Be("custom-aggregator-result");
     }
 
-    private static async Task<WorkflowRunResult> ProcessWorkflowRunAsync(StreamingRun run)
+    [Fact]
+    public void Test_AgentWorkflowBuilder_CreateSequentialBuilderWith_RejectsNull()
     {
-        StringBuilder sb = new();
-        WorkflowOutputEvent? output = null;
-        CheckpointInfo? lastCheckpoint = null;
-
-        List<RequestInfoEvent> pendingRequests = [];
-
-        await foreach (WorkflowEvent evt in run.WatchStreamAsync(blockOnPendingRequest: false).ConfigureAwait(false))
-        {
-            switch (evt)
-            {
-                case AgentResponseUpdateEvent responseUpdate:
-                    sb.Append(responseUpdate.Data);
-                    break;
-
-                case RequestInfoEvent requestInfo:
-                    pendingRequests.Add(requestInfo);
-                    break;
-
-                case WorkflowOutputEvent e:
-                    output = e;
-                    break;
-
-                case WorkflowErrorEvent errorEvent:
-                    Assert.Fail($"Workflow execution failed with error: {errorEvent.Exception}");
-                    break;
-
-                case SuperStepCompletedEvent stepCompleted:
-                    lastCheckpoint = stepCompleted.CompletionInfo?.Checkpoint;
-                    break;
-            }
-        }
-
-        return new(sb.ToString(), output?.As<List<ChatMessage>>(), lastCheckpoint, pendingRequests);
+        Assert.Throws<ArgumentNullException>("agents", () => AgentWorkflowBuilder.CreateSequentialBuilderWith(null!));
     }
 
-    private static Task<WorkflowRunResult> RunWorkflowAsync(
-        Workflow workflow, List<ChatMessage> input, ExecutionEnvironment executionEnvironment = ExecutionEnvironment.InProcess_Lockstep)
-        => RunWorkflowCheckpointedAsync(workflow, input, executionEnvironment.ToWorkflowExecutionEnvironment());
-
-    private sealed class DoubleEchoAgentWithBarrier(string name, StrongBox<TaskCompletionSource<bool>> barrier, StrongBox<int> remaining) : DoubleEchoAgent(name)
+    [Fact]
+    public void Test_AgentWorkflowBuilder_CreateSequentialBuilderWith_ReturnsConfigurableBuilder()
     {
-        protected override async IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingAsync(
-            IEnumerable<ChatMessage> messages, AgentSession? session = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
-        {
-            if (Interlocked.Decrement(ref remaining.Value) == 0)
-            {
-                barrier.Value!.SetResult(true);
-            }
+        OrchestrationTestHelpers.DoubleEchoAgent agent = new("agent1");
 
-            await barrier.Value!.Task.ConfigureAwait(false);
+        SequentialWorkflowBuilder builder = AgentWorkflowBuilder.CreateSequentialBuilderWith(agent);
+        Workflow workflow = builder.WithName("via-factory").Build();
 
-            await foreach (var update in base.RunCoreStreamingAsync(messages, session, options, cancellationToken))
-            {
-                await Task.Yield();
-                yield return update;
-            }
-        }
+        workflow.Name.Should().Be("via-factory");
+    }
+
+    [Fact]
+    public void Test_AgentWorkflowBuilder_CreateConcurrentBuilderWith_RejectsNull()
+    {
+        Assert.Throws<ArgumentNullException>("agents", () => AgentWorkflowBuilder.CreateConcurrentBuilderWith(null!));
+    }
+
+    [Fact]
+    public void Test_AgentWorkflowBuilder_CreateConcurrentBuilderWith_ReturnsConfigurableBuilder()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent agent = new("agent1");
+
+        ConcurrentWorkflowBuilder builder = AgentWorkflowBuilder.CreateConcurrentBuilderWith(agent);
+        Workflow workflow = builder.WithName("via-factory").Build();
+
+        workflow.Name.Should().Be("via-factory");
+    }
+
+    [Fact]
+    public void Test_AgentWorkflowBuilder_CreateHandoffBuilderWith_RejectsNull()
+    {
+#pragma warning disable MAAIW001
+        Assert.Throws<ArgumentNullException>("initialAgent", () => AgentWorkflowBuilder.CreateHandoffBuilderWith(null!));
+#pragma warning restore MAAIW001
+    }
+
+    [Fact]
+    public void Test_AgentWorkflowBuilder_CreateGroupChatBuilderWith_RejectsNull()
+    {
+        Assert.Throws<ArgumentNullException>("managerFactory", () => AgentWorkflowBuilder.CreateGroupChatBuilderWith(null!));
+    }
+
+    [Fact]
+    public void Test_AgentWorkflowBuilder_CreateMagenticBuilderWith_RejectsNull()
+    {
+#pragma warning disable MAAIW001
+        Assert.Throws<ArgumentNullException>("managerAgent", () => AgentWorkflowBuilder.CreateMagenticBuilderWith(null!));
+#pragma warning restore MAAIW001
     }
 }

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/BackwardsCompatibility/JsonCheckpointSerializationTests.cs

@@ -0,0 +1,121 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Collections.Generic;
+using System.Text.Json;
+using FluentAssertions;
+using Microsoft.Agents.AI.Workflows.Checkpointing;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests.BackwardsCompatibility;
+
+/// <summary>
+/// Tests pinning the JSON shape of checkpoint-adjacent types so older payloads keep
+/// deserializing correctly after the Outputs overhaul (see implementation-plan §5.7).
+/// </summary>
+public class JsonCheckpointSerializationTests
+{
+    private static readonly JsonSerializerOptions s_options = WorkflowsJsonUtilities.DefaultOptions;
+
+    private static WorkflowInfo BuildInfoWithOutputExecutors(Dictionary<string, HashSet<OutputTag>> outputs)
+        => new(
+            executors: new Dictionary<string, ExecutorInfo>(),
+            edges: new Dictionary<string, List<EdgeInfo>>(),
+            requestPorts: [],
+            startExecutorId: "start",
+            outputExecutorIds: outputs);
+
+    // ---------- WorkflowOutputEvent.Tags in-process round-trip (no JSON) ----------
+
+    [Fact]
+    public void Test_WorkflowOutputEvent_SingleTagCtorPopulatesTags()
+    {
+        WorkflowOutputEvent evt = new(data: "hello", executorId: "e1", tag: OutputTag.Intermediate);
+
+        evt.ExecutorId.Should().Be("e1");
+        evt.Tags.Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+        evt.HasTag(OutputTag.Intermediate).Should().BeTrue();
+        evt.IsIntermediate().Should().BeTrue();
+    }
+
+    [Fact]
+    public void Test_WorkflowOutputEvent_NoTagsCtorIsUntagged()
+    {
+        WorkflowOutputEvent evt = new(data: "hello", executorId: "e1");
+
+        evt.Tags.Should().BeEmpty();
+        evt.IsIntermediate().Should().BeFalse("an event with no tags is a terminal/regular output");
+    }
+
+    [Fact]
+    public void Test_WorkflowOutputEvent_MultiTagCtorPreservesAllTags()
+    {
+        OutputTag customTag = JsonSerializer.Deserialize<OutputTag>("\"custom\"", s_options);
+
+        WorkflowOutputEvent evt = new(data: "hello", executorId: "e1", tags: new[] { OutputTag.Intermediate, customTag });
+
+        evt.Tags.Should().HaveCount(2);
+        evt.HasTag(OutputTag.Intermediate).Should().BeTrue();
+        evt.HasTag(customTag).Should().BeTrue();
+        evt.IsIntermediate().Should().BeTrue();
+    }
+
+    // ---------- WorkflowInfo.OutputExecutorIds shape ----------
+    //
+    // Note: per the comment in WorkflowsJsonUtilities, WorkflowEvent / WorkflowOutputEvent
+    // is *not* currently a serialized checkpoint shape (events are not persisted into
+    // checkpoints today), so we do not pin a JSON round-trip for Tags on the event itself
+    // here. The tag JSON round-trip is exercised by OutputTagTests; the
+    // OutputExecutorIds map shape is the actually-load-bearing back-compat surface.
+
+    [Fact]
+    public void Test_JsonCheckpoint_WorkflowOutputExecutorsReadsLegacyArrayShape()
+    {
+        const string LegacyJson = """
+            {
+              "executors": {},
+              "edges": {},
+              "requestPorts": [],
+              "startExecutorId": "start",
+              "outputExecutorIds": ["a", "b"]
+            }
+            """;
+
+        WorkflowInfo? info = JsonSerializer.Deserialize<WorkflowInfo>(LegacyJson, s_options);
+
+        info.Should().NotBeNull();
+        info!.OutputExecutorIds.Should().HaveCount(2);
+        info.OutputExecutorIds["a"].Should().BeEmpty("legacy ids are untagged regular outputs");
+        info.OutputExecutorIds["b"].Should().BeEmpty();
+    }
+
+    [Fact]
+    public void Test_JsonCheckpoint_WorkflowOutputExecutorsWritesMapShape()
+    {
+        Dictionary<string, HashSet<OutputTag>> outputs = new()
+        {
+            ["a"] = [],
+            ["b"] = [OutputTag.Intermediate],
+        };
+
+        WorkflowInfo info = BuildInfoWithOutputExecutors(outputs);
+
+        string json = JsonSerializer.Serialize(info, s_options);
+
+        WorkflowInfo? back = JsonSerializer.Deserialize<WorkflowInfo>(json, s_options);
+
+        back.Should().NotBeNull();
+        back!.OutputExecutorIds.Should().HaveCount(2);
+        back.OutputExecutorIds["a"].Should().BeEmpty();
+        back.OutputExecutorIds["b"].Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+
+        // The map shape is detectable in the serialized JSON: the property value starts with `{`, not `[`.
+        int idx = json.IndexOf("\"outputExecutorIds\"", System.StringComparison.Ordinal);
+        idx.Should().BeGreaterThan(-1);
+        int colon = json.IndexOf(':', idx);
+        int firstNonSpace = colon + 1;
+        while (firstNonSpace < json.Length && char.IsWhiteSpace(json[firstNonSpace]))
+        {
+            firstNonSpace++;
+        }
+        json[firstNonSpace].Should().Be('{', "OutputExecutorIds is written in the new map shape");
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/ConcurrentWorkflowBuilderTests.cs

@@ -0,0 +1,164 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+using FluentAssertions;
+using Microsoft.Agents.AI.Workflows.UnitTests.Futures;
+using Microsoft.Extensions.AI;
+
+#pragma warning disable SYSLIB1045 // Use GeneratedRegex
+#pragma warning disable RCS1186 // Use Regex instance instead of static method
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+public class ConcurrentWorkflowBuilderTests
+{
+    [Fact]
+    public void Test_ConcurrentWorkflowBuilder_InvalidArguments_Throws()
+    {
+        Assert.Throws<ArgumentNullException>("agents", () => new ConcurrentWorkflowBuilder(null!));
+        Assert.Throws<ArgumentException>("agents", () => new ConcurrentWorkflowBuilder().Build());
+
+        Assert.Throws<ArgumentNullException>("agents", () => AgentWorkflowBuilder.BuildConcurrent(null!));
+        Assert.Throws<ArgumentNullException>("agents", () => AgentWorkflowBuilder.CreateConcurrentBuilderWith(null!));
+    }
+
+    [Fact]
+    public async Task Test_ConcurrentWorkflowBuilder_AgentsRunInParallelAsync()
+    {
+        StrongBox<TaskCompletionSource<bool>> barrier = new();
+        StrongBox<int> remaining = new();
+
+        var workflow = new ConcurrentWorkflowBuilder(
+            new OrchestrationTestHelpers.DoubleEchoAgentWithBarrier("agent1", barrier, remaining),
+            new OrchestrationTestHelpers.DoubleEchoAgentWithBarrier("agent2", barrier, remaining))
+            .Build();
+
+        for (int iter = 0; iter < 3; iter++)
+        {
+            barrier.Value = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
+            remaining.Value = 2;
+
+            (string updateText, List<ChatMessage>? result, _, _) =
+                await OrchestrationTestHelpers.RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, "abc")]);
+            Assert.NotEmpty(updateText);
+            Assert.NotNull(result);
+
+            // TODO: https://github.com/microsoft/agent-framework/issues/784
+            // These asserts are flaky until we guarantee message delivery order.
+            Assert.Single(Regex.Matches(updateText, "agent1"));
+            Assert.Single(Regex.Matches(updateText, "agent2"));
+            Assert.Equal(4, Regex.Matches(updateText, "abc").Count);
+            Assert.Equal(2, result.Count);
+        }
+    }
+
+    [Fact]
+    public void Test_ConcurrentWorkflowBuilder_DefaultDesignationsMatchSpec()
+    {
+        Workflow workflow = new ConcurrentWorkflowBuilder(
+            new OrchestrationTestHelpers.DoubleEchoAgent("agent1"),
+            new OrchestrationTestHelpers.DoubleEchoAgent("agent2"),
+            new OrchestrationTestHelpers.DoubleEchoAgent("agent3"))
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+        designations.Where(kvp => kvp.Value.Count == 0)
+            .Should().ContainSingle("ConcurrentEndExecutor is the sole terminal output by default");
+        designations.Where(kvp => kvp.Value.Contains(OutputTag.Intermediate))
+            .Should().HaveCount(6, "every agent (3) and per-agent accumulator (3) is designated intermediate by default");
+    }
+
+    [Fact]
+    public void Test_ConcurrentWorkflowBuilder_ExplicitDesignationsReplaceDefaults()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent a1 = new("agent1");
+        OrchestrationTestHelpers.DoubleEchoAgent a2 = new("agent2");
+        OrchestrationTestHelpers.DoubleEchoAgent a3 = new("agent3");
+
+        Workflow workflow = new ConcurrentWorkflowBuilder(a1, a2, a3)
+            .WithOutputFrom(a1)
+            .WithIntermediateOutputFrom([a2])
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+
+        designations.Should().HaveCount(2,
+            "only the two explicitly-designated agents land on the inner builder; the end + accumulator defaults are suppressed");
+        designations.Values.Where(tags => tags.Count == 0)
+            .Should().ContainSingle("agent1 is the only terminal designation");
+        designations.Values.Where(tags => tags.Contains(OutputTag.Intermediate))
+            .Should().ContainSingle("agent2 is the only intermediate designation");
+    }
+
+    [Fact]
+    public void Test_ConcurrentWorkflowBuilder_DesignationForNonParticipantThrows()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent participant = new("p1");
+        OrchestrationTestHelpers.DoubleEchoAgent stranger = new("stranger");
+
+        ConcurrentWorkflowBuilder builder = new ConcurrentWorkflowBuilder(participant)
+            .WithIntermediateOutputFrom([stranger]);
+
+        Action build = () => builder.Build();
+        build.Should().Throw<InvalidOperationException>().WithMessage("*stranger*");
+    }
+
+    [Fact]
+    public void Test_ConcurrentWorkflowBuilder_WithNamePropagatesToWorkflow()
+    {
+        Workflow workflow = new ConcurrentWorkflowBuilder(new OrchestrationTestHelpers.DoubleEchoAgent("agent1"))
+            .WithName("named-concurrent")
+            .Build();
+
+        workflow.Name.Should().Be("named-concurrent");
+    }
+
+    [Fact]
+    public void Test_ConcurrentWorkflowBuilder_WithDescriptionPropagatesToWorkflow()
+    {
+        Workflow workflow = new ConcurrentWorkflowBuilder(new OrchestrationTestHelpers.DoubleEchoAgent("agent1"))
+            .WithDescription("describes the concurrent fan-out/fan-in")
+            .Build();
+
+        workflow.Description.Should().Be("describes the concurrent fan-out/fan-in");
+    }
+
+    [Collection(FuturesSerialCollection.Name)]
+    public class AsAgentForwarding
+    {
+        [Fact]
+        public async Task Test_ConcurrentWorkflowBuilder_AsAgent_OnlyTerminalDesignationSurfacesAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+
+            OrchestrationTestHelpers.DoubleEchoAgent agent1 = new("agent1");
+            OrchestrationTestHelpers.DoubleEchoAgent agent2 = new("agent2");
+
+            // Designate only agent1 as a terminal output source — agent2 and the fan-in
+            // aggregator default-intermediate designations are suppressed.
+            Workflow workflow = new ConcurrentWorkflowBuilder(agent1, agent2)
+                .WithOutputFrom(agent1)
+                .Build();
+
+            List<AgentResponseUpdate> updates = await workflow
+                .AsAIAgent("WorkflowAgent")
+                .RunStreamingAsync(new ChatMessage(ChatRole.User, "abc"))
+                .ToListAsync();
+
+            HashSet<string> authoredBy = updates
+                .Select(u => u.AuthorName)
+                .Where(n => !string.IsNullOrEmpty(n))
+                .Select(n => n!)
+                .ToHashSet();
+
+            authoredBy.Should().Contain("agent1", "the designated agent must surface");
+            authoredBy.Should().NotContain("agent2",
+                "the undesignated agent must not surface when only one is designated under Futures-on");
+        }
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/Futures/Futures.AgentResponseOutputFilteringAndTaggingTests.cs

@@ -0,0 +1,289 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using FluentAssertions;
+using Microsoft.Extensions.AI;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests.Futures;
+
+/// <summary>
+/// Runner-level coverage for <see cref="Workflows.Futures.EnableAgentResponseOutputTaggingAndFiltering"/>.
+/// Exercises every combination of (flag on/off) × (designation kind) × (payload shape) to pin the
+/// runner's behavior in both the legacy bypass path and the unified filter-and-tag path.
+/// </summary>
+public static partial class FuturesTests
+{
+    [Collection(FuturesSerialCollection.Name)]
+    public class AgentResponseOutputFilteringAndTaggingTests
+    {
+        private const string SourceId = "yielder";
+
+        private static AgentResponse SampleResponse(string text = "hi")
+            => new(new ChatMessage(ChatRole.Assistant, text));
+
+        private static AgentResponseUpdate SampleUpdate(string text = "tick")
+            => new(ChatRole.Assistant, text);
+
+        private static async Task<List<WorkflowEvent>> RunAsync<T>(Workflow workflow, T input) where T : notnull
+        {
+            List<WorkflowEvent> events = [];
+            await using StreamingRun run = await InProcessExecution.RunStreamingAsync(workflow, input).ConfigureAwait(false);
+            await foreach (WorkflowEvent evt in run.WatchStreamAsync().ConfigureAwait(false))
+            {
+                events.Add(evt);
+            }
+            return events;
+        }
+
+        private static Workflow BuildAgentResponseWorkflow(Action<WorkflowBuilder, YieldAgentResponseExecutor>? designate = null)
+        {
+            YieldAgentResponseExecutor exec = new(SourceId);
+            WorkflowBuilder builder = new(exec);
+            designate?.Invoke(builder, exec);
+            return builder.Build();
+        }
+
+        private static Workflow BuildAgentResponseUpdateWorkflow(Action<WorkflowBuilder, YieldAgentResponseUpdateExecutor>? designate = null)
+        {
+            YieldAgentResponseUpdateExecutor exec = new(SourceId);
+            WorkflowBuilder builder = new(exec);
+            designate?.Invoke(builder, exec);
+            return builder.Build();
+        }
+
+        private static Workflow BuildPocoWorkflow(Action<WorkflowBuilder, YieldPocoExecutor>? designate = null)
+        {
+            YieldPocoExecutor exec = new(SourceId);
+            WorkflowBuilder builder = new(exec);
+            designate?.Invoke(builder, exec);
+            return builder.Build();
+        }
+
+        // F1
+        [Fact]
+        public async Task Test_Runner_LegacyAgentResponseBypass_RaisesUntaggedEventAsync()
+        {
+            using FuturesScope _ = new(enabled: false);
+            Workflow workflow = BuildAgentResponseWorkflow(designate: null);
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            AgentResponseEvent emitted = events.OfType<AgentResponseEvent>().Should().ContainSingle().Subject;
+            emitted.ExecutorId.Should().Be(SourceId);
+            emitted.Tags.Should().BeEmpty("legacy bypass attaches no tags");
+            emitted.IsIntermediate().Should().BeFalse();
+        }
+
+        // F2
+        [Fact]
+        public async Task Test_Runner_LegacyAgentResponseUpdateBypass_RaisesUntaggedEventAsync()
+        {
+            using FuturesScope _ = new(enabled: false);
+            Workflow workflow = BuildAgentResponseUpdateWorkflow(designate: null);
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            AgentResponseUpdateEvent emitted = events.OfType<AgentResponseUpdateEvent>().Should().ContainSingle().Subject;
+            emitted.Tags.Should().BeEmpty();
+        }
+
+        // F3
+        [Fact]
+        public async Task Test_Runner_LegacyBypassIgnoresDesignationAsync()
+        {
+            using FuturesScope _ = new(enabled: false);
+            Workflow workflow = BuildAgentResponseWorkflow(static (b, e) => b.WithIntermediateOutputFrom([e]));
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            AgentResponseEvent emitted = events.OfType<AgentResponseEvent>().Should().ContainSingle().Subject;
+            emitted.Tags.Should().BeEmpty("legacy bypass ignores the designation entirely");
+            emitted.IsIntermediate().Should().BeFalse("legacy bypass does not propagate tags");
+        }
+
+        // F4
+        [Fact]
+        public async Task Test_Runner_LegacyPocoIsFilteredAsync()
+        {
+            using FuturesScope _ = new(enabled: false);
+            Workflow workflow = BuildPocoWorkflow(designate: null);
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            events.OfType<WorkflowOutputEvent>().Should().BeEmpty("POCO outputs always go through the filter; undesignated source is dropped");
+        }
+
+        // F5
+        [Fact]
+        public async Task Test_Runner_UndesignatedAgentResponseIsFilteredWhenFuturesOnAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+            Workflow workflow = BuildAgentResponseWorkflow(designate: null);
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            events.OfType<WorkflowOutputEvent>().Should().BeEmpty(
+                "with the future on, AgentResponse must be designated to surface");
+        }
+
+        // F6
+        [Fact]
+        public async Task Test_Runner_DesignatedTerminalAgentResponseHasEmptyTagsAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+            Workflow workflow = BuildAgentResponseWorkflow(static (b, e) => b.WithOutputFrom(e));
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            AgentResponseEvent emitted = events.OfType<AgentResponseEvent>().Should().ContainSingle().Subject;
+            emitted.Tags.Should().BeEmpty("terminal designation carries no tag");
+            emitted.IsIntermediate().Should().BeFalse();
+        }
+
+        // F7
+        [Fact]
+        public async Task Test_Runner_DesignatedIntermediateAgentResponseHasIntermediateTagAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+            Workflow workflow = BuildAgentResponseWorkflow(static (b, e) => b.WithIntermediateOutputFrom([e]));
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            AgentResponseEvent emitted = events.OfType<AgentResponseEvent>().Should().ContainSingle().Subject;
+            emitted.Tags.Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+            emitted.IsIntermediate().Should().BeTrue();
+        }
+
+        // F8
+        [Fact]
+        public async Task Test_Runner_DesignatedIntermediateAgentResponseUpdateHasIntermediateTagAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+            Workflow workflow = BuildAgentResponseUpdateWorkflow(static (b, e) => b.WithIntermediateOutputFrom([e]));
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            AgentResponseUpdateEvent emitted = events.OfType<AgentResponseUpdateEvent>().Should().ContainSingle().Subject;
+            emitted.Tags.Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+            emitted.IsIntermediate().Should().BeTrue();
+        }
+
+        // F9
+        [Fact]
+        public async Task Test_Runner_TagsAccumulateOutputThenIntermediateAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+            Workflow workflow = BuildAgentResponseWorkflow(static (b, e) =>
+            {
+                b.WithOutputFrom(e);
+                b.WithIntermediateOutputFrom([e]);
+            });
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            AgentResponseEvent emitted = events.OfType<AgentResponseEvent>().Should().ContainSingle().Subject;
+            emitted.Tags.Should().BeEquivalentTo(new[] { OutputTag.Intermediate },
+                "terminal+intermediate union is {{ Intermediate }} (terminal contributes the entry but no tag)");
+            emitted.IsIntermediate().Should().BeTrue();
+        }
+
+        // F10
+        [Fact]
+        public async Task Test_Runner_TagsAccumulateIntermediateThenOutputAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+            Workflow workflow = BuildAgentResponseWorkflow(static (b, e) =>
+            {
+                b.WithIntermediateOutputFrom([e]);
+                b.WithOutputFrom(e);
+            });
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            AgentResponseEvent emitted = events.OfType<AgentResponseEvent>().Should().ContainSingle().Subject;
+            emitted.Tags.Should().BeEquivalentTo(new[] { OutputTag.Intermediate }, "designation order is irrelevant");
+            emitted.IsIntermediate().Should().BeTrue();
+        }
+
+        // F11
+        [Fact]
+        public async Task Test_Runner_DesignatedIntermediatePocoHasIntermediateTagAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+            Workflow workflow = BuildPocoWorkflow(static (b, e) => b.WithIntermediateOutputFrom([e]));
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            WorkflowOutputEvent emitted = events.OfType<WorkflowOutputEvent>().Should().ContainSingle().Subject;
+            emitted.Should().NotBeOfType<AgentResponseEvent>();
+            emitted.Tags.Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+            emitted.IsIntermediate().Should().BeTrue();
+        }
+
+        // F12
+        [Fact]
+        public async Task Test_Runner_DesignatedTerminalPocoHasEmptyTagsAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+            Workflow workflow = BuildPocoWorkflow(static (b, e) => b.WithOutputFrom(e));
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            WorkflowOutputEvent emitted = events.OfType<WorkflowOutputEvent>().Should().ContainSingle().Subject;
+            emitted.Tags.Should().BeEmpty();
+            emitted.IsIntermediate().Should().BeFalse();
+        }
+
+        // F13
+        [Fact]
+        public async Task Test_Runner_RepeatedTerminalDesignationDedupesAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+            Workflow workflow = BuildAgentResponseWorkflow(static (b, e) =>
+            {
+                b.WithOutputFrom(e);
+                b.WithOutputFrom(e);
+            });
+
+            List<WorkflowEvent> events = await RunAsync(workflow, "go");
+
+            AgentResponseEvent emitted = events.OfType<AgentResponseEvent>().Should().ContainSingle().Subject;
+            emitted.Tags.Should().BeEmpty("repeated terminal designation contributes no tag");
+        }
+
+        // ---- Executors -----------------------------------------------------------
+
+        internal sealed class YieldAgentResponseExecutor(string id) : Executor(id)
+        {
+            protected override ProtocolBuilder ConfigureProtocol(ProtocolBuilder protocolBuilder)
+                => protocolBuilder.ConfigureRoutes(rb => rb.AddHandler<string, AgentResponse>(this.HandleAsync));
+
+            private ValueTask<AgentResponse> HandleAsync(string input, IWorkflowContext context, CancellationToken cancellationToken)
+                => new(SampleResponse(input));
+        }
+
+        internal sealed class YieldAgentResponseUpdateExecutor(string id) : Executor(id)
+        {
+            protected override ProtocolBuilder ConfigureProtocol(ProtocolBuilder protocolBuilder)
+                => protocolBuilder.ConfigureRoutes(rb => rb.AddHandler<string, AgentResponseUpdate>(this.HandleAsync));
+
+            private ValueTask<AgentResponseUpdate> HandleAsync(string input, IWorkflowContext context, CancellationToken cancellationToken)
+                => new(SampleUpdate(input));
+        }
+
+        public sealed record Poco(string Value);
+
+        internal sealed class YieldPocoExecutor(string id) : Executor(id)
+        {
+            protected override ProtocolBuilder ConfigureProtocol(ProtocolBuilder protocolBuilder)
+                => protocolBuilder.ConfigureRoutes(rb => rb.AddHandler<string, Poco>(this.HandleAsync));
+
+            private ValueTask<Poco> HandleAsync(string input, IWorkflowContext context, CancellationToken cancellationToken)
+                => new(new Poco(input));
+        }
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/Futures/FuturesScope.cs

@@ -0,0 +1,27 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests.Futures;
+
+/// <summary>
+/// Sets <see cref="Workflows.Futures.EnableAgentResponseOutputTaggingAndFiltering"/> for
+/// the lifetime of the scope, restoring the prior value on dispose. Pair every use with
+/// <c>using</c> and run inside the <c>FuturesSerial</c> xUnit collection to avoid leaking
+/// state across parallel tests.
+/// </summary>
+internal sealed class FuturesScope : IDisposable
+{
+    private readonly bool _previous;
+
+    public FuturesScope(bool enabled)
+    {
+        this._previous = Workflows.Futures.EnableAgentResponseOutputTaggingAndFiltering;
+        Workflows.Futures.EnableAgentResponseOutputTaggingAndFiltering = enabled;
+    }
+
+    public void Dispose()
+    {
+        Workflows.Futures.EnableAgentResponseOutputTaggingAndFiltering = this._previous;
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/Futures/FuturesSerialCollection.cs

@@ -0,0 +1,19 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests.Futures;
+
+/// <summary>
+/// xUnit collection marker for tests that mutate the process-global
+/// <see cref="Workflows.Futures"/> switches. Membership in this collection serializes
+/// the tests against each other so that <see cref="FuturesScope"/> cannot leak state
+/// into a concurrently running test.
+/// </summary>
+[CollectionDefinition(Name, DisableParallelization = true)]
+[SuppressMessage("Naming", "CA1711:Identifiers should not have incorrect suffix",
+    Justification = "xUnit's [CollectionDefinition] pattern names the marker type after the collection's purpose; the 'Collection' suffix is idiomatic.")]
+public sealed class FuturesSerialCollection
+{
+    public const string Name = "FuturesSerial";
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/GroupChatOrchestrationTests.cs

@@ -0,0 +1,479 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Text.Json;
+using System.Threading;
+using System.Threading.Tasks;
+using FluentAssertions;
+using Microsoft.Agents.AI.Workflows.InProc;
+using Microsoft.Extensions.AI;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+/// <summary>
+/// Orchestration-level tests for <see cref="AgentWorkflowBuilder.CreateGroupChatBuilderWith"/> covering
+/// <see cref="FunctionCallContent"/> and <see cref="ToolApprovalRequestContent"/> behavior across
+/// real <see cref="ChatClientAgent"/> participants. These tests parallel the equivalents in
+/// <see cref="HandoffOrchestrationTests"/> to ensure that the broadcast-based group chat host
+/// (each participant maintains its own per-agent session via <see cref="Specialized.AIAgentHostExecutor"/>;
+/// only the speaker receives a <see cref="TurnToken"/>; messages are broadcast to every other
+/// participant) preserves the same HITL semantics as the handoff path.
+/// </summary>
+public class GroupChatOrchestrationTests
+{
+    /// <summary>
+    /// End-to-end tool-approval checkpoint/resume scenario through a <see cref="RoundRobinGroupChatManager"/>
+    /// with a single participant. Mirrors the maximal repro added in PR #5952 (Track A2 in
+    /// <c>docs/working/issue-5350-root-cause-validation-plan.md</c>): a <see cref="ChatClientAgent"/>
+    /// over a mock chat client emits a <see cref="FunctionCallContent"/> for an
+    /// <see cref="ApprovalRequiredAIFunction"/>, the runtime surfaces a
+    /// <see cref="ToolApprovalRequestContent"/> as an external <see cref="RequestInfoEvent"/>, the test
+    /// checkpoints while the request is pending, resumes from a fresh handle, asserts that the
+    /// resumed <c>TARC.ToolCall</c> is still a <see cref="FunctionCallContent"/>, sends an
+    /// approval response, and verifies that the wrapped <see cref="AIFunction"/> is invoked
+    /// exactly once and the workflow completes without errors.
+    /// </summary>
+    [Fact]
+    public async Task GroupChat_ToolApproval_JsonCheckpointResume_PreservesFunctionCallContentAndInvokesToolAsync()
+    {
+        ApprovalHarness harness = new();
+        Workflow workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 4 })
+            .AddParticipants(harness.Agent)
+            .Build();
+
+        await RunCheckpointedApprovalRoundTripAsync(
+            workflow,
+            harness,
+            CheckpointManager.CreateJson(new InMemoryJsonStore()),
+            scenarioName: "GroupChat (round-robin, single participant)");
+    }
+
+    /// <summary>
+    /// Round-robin group chat with two participants. The first participant exposes an
+    /// <see cref="ApprovalRequiredAIFunction"/> and emits a <see cref="FunctionCallContent"/> for it on
+    /// its first turn. The test denies the approval and asserts that the conversation continues:
+    /// the first agent runs once more (the FICC denial branch produces a final assistant message),
+    /// then the host broadcasts that message and selects the second agent, which produces its own
+    /// reply. This mirrors <c>Handoffs_TwoTransfers_SecondAgentUserApproval_ResponseServedByThirdAgentAsync</c>
+    /// but on the group-chat path.
+    /// </summary>
+    [Fact]
+    public async Task GroupChat_ToolApproval_DeniedResponse_ConversationContinuesAsync()
+    {
+        int approvalToolCallCount = 0;
+
+        const string ApprovalCallId = "approve_call_1";
+        const string ApprovalToolName = "DoSomethingPrivileged";
+
+        AIFunction approvalTool = new ApprovalRequiredAIFunction(AIFunctionFactory.Create(
+            () =>
+            {
+                Interlocked.Increment(ref approvalToolCallCount);
+                return "tool result";
+            },
+            name: ApprovalToolName,
+            description: "Performs a privileged action"));
+
+        int agent1CallCount = 0;
+        var agent1 = new ChatClientAgent(
+            new MockChatClient((messages, options) =>
+            {
+                int call = Interlocked.Increment(ref agent1CallCount);
+                return call switch
+                {
+                    1 => new ChatResponse(new ChatMessage(ChatRole.Assistant,
+                        [new FunctionCallContent(ApprovalCallId, ApprovalToolName)])),
+                    _ => new ChatResponse(new ChatMessage(ChatRole.Assistant, "agent1 final response")),
+                };
+            }),
+            instructions: "You are agent1.",
+            name: "agent1",
+            tools: [approvalTool]);
+
+        int agent2CallCount = 0;
+        var agent2 = new ChatClientAgent(
+            new MockChatClient((messages, options) =>
+            {
+                Interlocked.Increment(ref agent2CallCount);
+                return new ChatResponse(new ChatMessage(ChatRole.Assistant, "agent2 reply"));
+            }),
+            instructions: "You are agent2.",
+            name: "agent2");
+
+        Workflow workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 2 })
+            .AddParticipants(agent1, agent2)
+            .Build();
+
+        CheckpointManager checkpointManager = CheckpointManager.CreateInMemory();
+        InProcessExecutionEnvironment env = InProcessExecution.OffThread.WithCheckpointing(checkpointManager);
+
+        ExternalRequest? pendingRequest = null;
+        CheckpointInfo? lastCheckpoint = null;
+        List<WorkflowEvent> firstRunEvents = [];
+
+        await using (StreamingRun firstRun = await env.RunStreamingAsync(workflow, new List<ChatMessage> { new(ChatRole.User, "hello") }))
+        {
+            (await firstRun.TrySendMessageAsync(new TurnToken(emitEvents: false)))
+                .Should().BeTrue();
+
+            using CancellationTokenSource cts = new(TimeSpan.FromSeconds(30));
+            await foreach (WorkflowEvent evt in firstRun.WatchStreamAsync(blockOnPendingRequest: false, cts.Token))
+            {
+                firstRunEvents.Add(evt);
+                if (evt is RequestInfoEvent requestInfo)
+                {
+                    pendingRequest ??= requestInfo.Request;
+                }
+                if (evt is SuperStepCompletedEvent step && step.CompletionInfo?.Checkpoint is { } cp)
+                {
+                    lastCheckpoint = cp;
+                }
+            }
+        }
+
+        pendingRequest.Should().NotBeNull("agent1 should have surfaced an approval request for the privileged tool");
+        firstRunEvents.OfType<WorkflowErrorEvent>().Should().BeEmpty();
+        firstRunEvents.OfType<ExecutorFailedEvent>().Should().BeEmpty();
+        approvalToolCallCount.Should().Be(0, "the tool must not be invoked before approval is granted");
+
+        ToolApprovalRequestContent approvalRequest =
+            pendingRequest!.Data.As<ToolApprovalRequestContent>().Should().NotBeNull()
+                                                                 .And.Subject.As<ToolApprovalRequestContent>();
+        approvalRequest.ToolCall.Should().BeOfType<FunctionCallContent>();
+        ((FunctionCallContent)approvalRequest.ToolCall).Name.Should().Be(ApprovalToolName);
+
+        // Deny the request and continue the conversation.
+        ExternalResponse denial = pendingRequest.CreateResponse(approvalRequest.CreateResponse(approved: false, reason: "Denied"));
+
+        List<WorkflowEvent> secondRunEvents = [];
+        List<ChatMessage>? finalOutput = null;
+        await using (StreamingRun resumed = await env.ResumeStreamingAsync(workflow, lastCheckpoint!))
+        {
+            await resumed.SendResponseAsync(denial);
+
+            using CancellationTokenSource cts = new(TimeSpan.FromSeconds(30));
+            await foreach (WorkflowEvent evt in resumed.WatchStreamAsync(blockOnPendingRequest: false, cts.Token))
+            {
+                secondRunEvents.Add(evt);
+                if (evt is WorkflowOutputEvent outputEvt)
+                {
+                    finalOutput = outputEvt.As<List<ChatMessage>>();
+                }
+            }
+        }
+
+        secondRunEvents.OfType<WorkflowErrorEvent>().Should().BeEmpty(
+            "denying the approval should not surface any workflow errors");
+        secondRunEvents.OfType<ExecutorFailedEvent>().Should().BeEmpty(
+            "denying the approval should not raise executor failures (regression guard for the GroupChat duplicate-key bug pinned in PR #5952's A2 test before the broadcast refactor)");
+
+        approvalToolCallCount.Should().Be(0, "the tool must not be invoked after denial");
+        agent1CallCount.Should().BeGreaterThanOrEqualTo(2, "agent1 should be re-invoked by FICC after the denial to produce a final assistant message");
+        agent2CallCount.Should().Be(1, "agent2 should be the next round-robin speaker and produce its own reply");
+
+        finalOutput.Should().NotBeNull();
+        finalOutput!.Should().Contain(m => m.AuthorName == "agent1");
+        finalOutput.Should().Contain(m => m.AuthorName == "agent2" && m.Text == "agent2 reply");
+    }
+
+    /// <summary>
+    /// Round-robin group chat with two participants. The first participant declares a
+    /// non-invokable function via <c>AIFunctionFactory.CreateDeclaration</c>,
+    /// causing the function call to be surfaced as an external <see cref="FunctionCallContent"/>
+    /// (<see cref="RequestInfoEvent"/>). The test responds with a <see cref="FunctionResultContent"/>
+    /// and asserts that the conversation continues: the first agent's second invocation produces a
+    /// final assistant message, then the group chat advances to the second agent which produces
+    /// its own reply. This mirrors <c>Handoffs_TwoTransfers_SecondAgentToolCall_ResponseServedByThirdAgentAsync</c>
+    /// but on the group-chat path.
+    /// </summary>
+    [Fact]
+    public async Task GroupChat_FunctionCall_ExternallyResolved_ConversationContinuesAsync()
+    {
+        const string FunctionCallId = "fcc_call_1";
+        const string FunctionName = "FetchExternalData";
+
+        JsonElement schema = AIFunctionFactory.Create(() => true).JsonSchema;
+        AIFunctionDeclaration declaration = AIFunctionFactory.CreateDeclaration(FunctionName, "Fetches external data", schema);
+
+        int agent1CallCount = 0;
+        var agent1 = new ChatClientAgent(
+            new MockChatClient((messages, options) =>
+            {
+                int call = Interlocked.Increment(ref agent1CallCount);
+                return call switch
+                {
+                    1 => new ChatResponse(new ChatMessage(ChatRole.Assistant,
+                        [new FunctionCallContent(FunctionCallId, FunctionName)])),
+                    _ => new ChatResponse(new ChatMessage(ChatRole.Assistant, "agent1 final response")),
+                };
+            }),
+            instructions: "You are agent1.",
+            name: "agent1",
+            tools: [declaration]);
+
+        int agent2CallCount = 0;
+        var agent2 = new ChatClientAgent(
+            new MockChatClient((messages, options) =>
+            {
+                Interlocked.Increment(ref agent2CallCount);
+                return new ChatResponse(new ChatMessage(ChatRole.Assistant, "agent2 reply"));
+            }),
+            instructions: "You are agent2.",
+            name: "agent2");
+
+        Workflow workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 2 })
+            .AddParticipants(agent1, agent2)
+            .Build();
+
+        CheckpointManager checkpointManager = CheckpointManager.CreateInMemory();
+        InProcessExecutionEnvironment env = InProcessExecution.OffThread.WithCheckpointing(checkpointManager);
+
+        ExternalRequest? pendingRequest = null;
+        CheckpointInfo? lastCheckpoint = null;
+
+        await using (StreamingRun firstRun = await env.RunStreamingAsync(workflow, new List<ChatMessage> { new(ChatRole.User, "hello") }))
+        {
+            (await firstRun.TrySendMessageAsync(new TurnToken(emitEvents: false)))
+                .Should().BeTrue();
+
+            using CancellationTokenSource cts = new(TimeSpan.FromSeconds(30));
+            await foreach (WorkflowEvent evt in firstRun.WatchStreamAsync(blockOnPendingRequest: false, cts.Token))
+            {
+                if (evt is RequestInfoEvent requestInfo)
+                {
+                    pendingRequest ??= requestInfo.Request;
+                }
+                if (evt is SuperStepCompletedEvent step && step.CompletionInfo?.Checkpoint is { } cp)
+                {
+                    lastCheckpoint = cp;
+                }
+            }
+        }
+
+        pendingRequest.Should().NotBeNull("agent1 should have surfaced a FunctionCallContent for the declaration-only tool");
+
+        FunctionCallContent functionCall =
+            pendingRequest!.Data.As<FunctionCallContent>().Should().NotBeNull()
+                                                          .And.Subject.As<FunctionCallContent>();
+        functionCall.Name.Should().Be(FunctionName);
+        functionCall.CallId.Should().EndWith(FunctionCallId,
+            "the workflow rewrites the CallId with an executor-scoped prefix, but should preserve the original tail");
+
+        // Respond with a function result and let the conversation continue.
+        ExternalResponse response = pendingRequest.CreateResponse(new FunctionResultContent(functionCall.CallId, "external-data-payload"));
+
+        List<WorkflowEvent> resumeEvents = [];
+        List<ChatMessage>? finalOutput = null;
+        await using (StreamingRun resumed = await env.ResumeStreamingAsync(workflow, lastCheckpoint!))
+        {
+            await resumed.SendResponseAsync(response);
+
+            using CancellationTokenSource cts = new(TimeSpan.FromSeconds(30));
+            await foreach (WorkflowEvent evt in resumed.WatchStreamAsync(blockOnPendingRequest: false, cts.Token))
+            {
+                resumeEvents.Add(evt);
+                if (evt is WorkflowOutputEvent outputEvt)
+                {
+                    finalOutput = outputEvt.As<List<ChatMessage>>();
+                }
+            }
+        }
+
+        resumeEvents.OfType<WorkflowErrorEvent>().Should().BeEmpty();
+        resumeEvents.OfType<ExecutorFailedEvent>().Should().BeEmpty();
+
+        agent1CallCount.Should().BeGreaterThanOrEqualTo(2, "agent1 should be re-invoked once the externally-resolved function result is delivered");
+        agent2CallCount.Should().Be(1, "agent2 should be the next round-robin speaker after agent1 finishes");
+
+        finalOutput.Should().NotBeNull();
+        finalOutput!.Should().Contain(m => m.AuthorName == "agent1");
+        finalOutput.Should().Contain(m => m.AuthorName == "agent2" && m.Text == "agent2 reply");
+    }
+
+    /// <summary>
+    /// Shared end-to-end driver for the approval checkpoint/resume scenario; modelled on the
+    /// <c>RunReproAsync</c> helper from PR #5952. Runs the workflow until an approval request is
+    /// pending, captures the latest checkpoint, disposes the run, resumes from a fresh handle,
+    /// asserts the resumed payload still carries a <see cref="FunctionCallContent"/>, sends an
+    /// approval response, and asserts the wrapped tool is invoked exactly once and the workflow
+    /// finishes without errors.
+    /// </summary>
+    private static async Task RunCheckpointedApprovalRoundTripAsync(
+        Workflow workflow,
+        ApprovalHarness harness,
+        CheckpointManager checkpointManager,
+        string scenarioName)
+    {
+        InProcessExecutionEnvironment env = InProcessExecution.OffThread;
+        List<ChatMessage> inputMessages = [new(ChatRole.User, "What's the weather in Amsterdam?")];
+
+        ExternalRequest? firstRunRequest = null;
+        CheckpointInfo? checkpoint = null;
+
+        await using (StreamingRun firstRun = await env.WithCheckpointing(checkpointManager)
+                                                      .RunStreamingAsync(workflow, inputMessages))
+        {
+            (await firstRun.TrySendMessageAsync(new TurnToken(emitEvents: false)))
+                .Should().BeTrue($"[{scenarioName}] the workflow should accept a TurnToken");
+
+            using CancellationTokenSource cts = new(TimeSpan.FromSeconds(30));
+            await foreach (WorkflowEvent evt in firstRun.WatchStreamAsync(blockOnPendingRequest: false, cts.Token))
+            {
+                if (evt is RequestInfoEvent requestInfo)
+                {
+                    firstRunRequest ??= requestInfo.Request;
+                }
+                if (evt is SuperStepCompletedEvent step && step.CompletionInfo?.Checkpoint is { } cp)
+                {
+                    checkpoint = cp;
+                }
+            }
+        }
+
+        firstRunRequest.Should().NotBeNull(
+            $"[{scenarioName}] the ChatClientAgent + FICC pipeline should surface the approval request as a workflow RequestInfoEvent");
+        checkpoint.Should().NotBeNull(
+            $"[{scenarioName}] a checkpoint should have been produced while the approval request was pending");
+        harness.ChatCallCount.Should().Be(1, $"[{scenarioName}] the mock chat client should have been called exactly once before approval was requested");
+        harness.InvocationCount.Should().Be(0, $"[{scenarioName}] the underlying tool must NOT have been invoked before approval was granted");
+
+        ToolApprovalRequestContent? preCheckpoint = firstRunRequest!.Data.As<ToolApprovalRequestContent>();
+        preCheckpoint.Should().NotBeNull($"[{scenarioName}] the pending external request should carry a ToolApprovalRequestContent payload");
+        preCheckpoint!.ToolCall.Should().BeOfType<FunctionCallContent>(
+            $"[{scenarioName}] the pre-checkpoint pending request payload must already be a FunctionCallContent");
+
+        // Resume on a fresh handle and capture the re-emitted approval request.
+        ExternalRequest? resumedRequest = null;
+        List<WorkflowEvent> postResumeEvents = [];
+
+        await using (StreamingRun resumed = await env.WithCheckpointing(checkpointManager)
+                                                     .ResumeStreamingAsync(workflow, checkpoint!))
+        {
+            using CancellationTokenSource cts = new(TimeSpan.FromSeconds(30));
+            await foreach (WorkflowEvent evt in resumed.WatchStreamAsync(blockOnPendingRequest: false, cts.Token))
+            {
+                if (evt is RequestInfoEvent requestInfo)
+                {
+                    resumedRequest ??= requestInfo.Request;
+                }
+            }
+
+            resumedRequest.Should().NotBeNull($"[{scenarioName}] the resumed workflow should re-emit the pending approval RequestInfoEvent");
+
+            ToolApprovalRequestContent? postResume = resumedRequest!.Data.As<ToolApprovalRequestContent>();
+            postResume.Should().NotBeNull(
+                $"[{scenarioName}] ExternalRequest.Data.As<ToolApprovalRequestContent>() should materialize the payload after JSON-checkpoint resume");
+            postResume!.ToolCall.Should().NotBeNull($"[{scenarioName}] the resumed TARC must carry its ToolCall");
+            postResume.ToolCall.Should().BeOfType<FunctionCallContent>(
+                $"[{scenarioName}] after CheckpointManager.CreateJson round-trip via ResumeStreamingAsync, " +
+                "ToolApprovalRequestContent.ToolCall must still be a FunctionCallContent so that " +
+                "FunctionInvokingChatClient's pattern match (`tarc.ToolCall is FunctionCallContent`) continues to fire.");
+
+            ToolApprovalResponseContent approvalResponse = postResume.CreateResponse(approved: true);
+            await resumed.SendResponseAsync(resumedRequest.CreateResponse(approvalResponse));
+
+            using CancellationTokenSource cts2 = new(TimeSpan.FromSeconds(30));
+            await foreach (WorkflowEvent evt in resumed.WatchStreamAsync(blockOnPendingRequest: false, cts2.Token))
+            {
+                postResumeEvents.Add(evt);
+            }
+        }
+
+        harness.InvocationCount.Should().Be(1,
+            $"[{scenarioName}] approving the request should cause FunctionInvokingChatClient to invoke the wrapped AIFunction exactly once");
+        postResumeEvents.OfType<WorkflowErrorEvent>().Should().BeEmpty(
+            $"[{scenarioName}] no workflow errors should be raised when responding to the resumed approval request");
+        postResumeEvents.OfType<ExecutorFailedEvent>().Should().BeEmpty(
+            $"[{scenarioName}] no executor failures should be raised when responding to the resumed approval request " +
+            "(regression guard: pre-broadcast-refactor this test was the `Track A2` repro in PR #5952 which surfaced a " +
+            "duplicate-key ArgumentException out of FunctionInvokingChatClient.ExtractAndRemoveApprovalRequestsAndResponses).");
+    }
+
+    /// <summary>
+    /// Bundles a <see cref="ChatClientAgent"/> with a counting <see cref="ApprovalRequiredAIFunction"/>
+    /// tool and a <see cref="MockChatClient"/> that emits a function call on the first chat turn
+    /// and a final assistant text on subsequent turns (after FICC has processed the approval
+    /// and appended a <see cref="FunctionResultContent"/>).
+    /// </summary>
+    private sealed class ApprovalHarness
+    {
+        public const string ToolName = "GetWeather";
+        public const string ToolResultText = "Sunny, 22°C";
+        public const string ToolCallId = "call-1";
+        public const string FinalAssistantText = "The weather in Amsterdam is sunny and 22°C.";
+
+        private int _invocationCount;
+        private int _chatCallIndex;
+
+        public int InvocationCount => Volatile.Read(ref this._invocationCount);
+        public int ChatCallCount => Volatile.Read(ref this._chatCallIndex);
+
+        public ChatClientAgent Agent { get; }
+
+        public ApprovalHarness()
+        {
+            AIFunction underlyingTool = AIFunctionFactory.Create(
+                ([Description("City to look up")] string city) =>
+                {
+                    Interlocked.Increment(ref this._invocationCount);
+                    return ToolResultText;
+                },
+                name: ToolName,
+                description: "Gets the weather for the given city");
+
+            ApprovalRequiredAIFunction approvalTool = new(underlyingTool);
+
+            MockChatClient mockChatClient = new((messages, options) =>
+            {
+                int index = Interlocked.Increment(ref this._chatCallIndex) - 1;
+                return index switch
+                {
+                    0 => new ChatResponse(new ChatMessage(ChatRole.Assistant,
+                        [new FunctionCallContent(
+                            callId: ToolCallId,
+                            name: ToolName,
+                            arguments: new Dictionary<string, object?> { ["city"] = "Amsterdam" })])),
+                    _ => new ChatResponse(new ChatMessage(ChatRole.Assistant, FinalAssistantText)),
+                };
+            });
+
+            this.Agent = new ChatClientAgent(
+                mockChatClient,
+                instructions: "You are a weather agent.",
+                name: "WeatherAgent",
+                tools: [approvalTool]);
+        }
+    }
+
+    /// <summary>
+    /// Minimal <see cref="IChatClient"/> stub for orchestration tests; delegates each call to a
+    /// caller-supplied factory.
+    /// </summary>
+    private sealed class MockChatClient(Func<IEnumerable<ChatMessage>, ChatOptions?, ChatResponse> responseFactory) : IChatClient
+    {
+        public Task<ChatResponse> GetResponseAsync(IEnumerable<ChatMessage> messages, ChatOptions? options = null, CancellationToken cancellationToken = default)
+            => Task.FromResult(responseFactory(messages, options));
+
+        public async IAsyncEnumerable<ChatResponseUpdate> GetStreamingResponseAsync(
+            IEnumerable<ChatMessage> messages,
+            ChatOptions? options = null,
+            [EnumeratorCancellation] CancellationToken cancellationToken = default)
+        {
+            ChatResponse response = await this.GetResponseAsync(messages, options, cancellationToken).ConfigureAwait(false);
+            foreach (ChatResponseUpdate update in response.ToChatResponseUpdates())
+            {
+                yield return update;
+            }
+        }
+
+        public object? GetService(Type serviceType, object? serviceKey = null) => null;
+        public void Dispose() { }
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/GroupChatWorkflowBuilderTests.cs

@@ -0,0 +1,477 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Text.Json;
+using System.Threading;
+using System.Threading.Tasks;
+using FluentAssertions;
+using Microsoft.Agents.AI.Workflows.InProc;
+using Microsoft.Extensions.AI;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+public class GroupChatWorkflowBuilderTests
+{
+    [Fact]
+    public void BuildGroupChat_InvalidArguments_Throws()
+    {
+        Assert.Throws<ArgumentNullException>("managerFactory", () => AgentWorkflowBuilder.CreateGroupChatBuilderWith(null!));
+
+        var groupChat = AgentWorkflowBuilder.CreateGroupChatBuilderWith(_ => new RoundRobinGroupChatManager([new OrchestrationTestHelpers.DoubleEchoAgent("a1")]));
+        Assert.NotNull(groupChat);
+        Assert.Throws<ArgumentNullException>("agents", () => groupChat.AddParticipants(null!));
+        Assert.Throws<ArgumentNullException>("agents", () => groupChat.AddParticipants([null!]));
+        Assert.Throws<ArgumentNullException>("agents", () => groupChat.AddParticipants(new OrchestrationTestHelpers.DoubleEchoAgent("a1"), null!));
+
+        Assert.Throws<ArgumentNullException>("agents", () => new RoundRobinGroupChatManager(null!));
+    }
+
+    [Fact]
+    public void GroupChatManager_MaximumIterationCount_Invalid_Throws()
+    {
+        var manager = new RoundRobinGroupChatManager([new OrchestrationTestHelpers.DoubleEchoAgent("a1")]);
+
+        const int DefaultMaxIterations = 40;
+        Assert.Equal(DefaultMaxIterations, manager.MaximumIterationCount);
+        Assert.Throws<ArgumentOutOfRangeException>("value", void () => manager.MaximumIterationCount = 0);
+        Assert.Throws<ArgumentOutOfRangeException>("value", void () => manager.MaximumIterationCount = -1);
+        Assert.Equal(DefaultMaxIterations, manager.MaximumIterationCount);
+
+        manager.MaximumIterationCount = 30;
+        Assert.Equal(30, manager.MaximumIterationCount);
+
+        manager.MaximumIterationCount = 1;
+        Assert.Equal(1, manager.MaximumIterationCount);
+
+        manager.MaximumIterationCount = int.MaxValue;
+        Assert.Equal(int.MaxValue, manager.MaximumIterationCount);
+    }
+
+    [Fact]
+    public void BuildGroupChat_WithNameAndDescription_SetsWorkflowNameAndDescription()
+    {
+        const string WorkflowName = "Test Group Chat";
+        const string WorkflowDescription = "A test group chat workflow";
+
+        var workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 2 })
+            .AddParticipants(new OrchestrationTestHelpers.DoubleEchoAgent("agent1"), new OrchestrationTestHelpers.DoubleEchoAgent("agent2"))
+            .WithName(WorkflowName)
+            .WithDescription(WorkflowDescription)
+            .Build();
+
+        Assert.Equal(WorkflowName, workflow.Name);
+        Assert.Equal(WorkflowDescription, workflow.Description);
+    }
+
+    [Fact]
+    public void BuildGroupChat_WithNameOnly_SetsWorkflowName()
+    {
+        const string WorkflowName = "Named Group Chat";
+
+        var workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 2 })
+            .AddParticipants(new OrchestrationTestHelpers.DoubleEchoAgent("agent1"))
+            .WithName(WorkflowName)
+            .Build();
+
+        Assert.Equal(WorkflowName, workflow.Name);
+        Assert.Null(workflow.Description);
+    }
+
+    [Fact]
+    public void BuildGroupChat_WithoutNameOrDescription_DefaultsToNull()
+    {
+        var workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 2 })
+            .AddParticipants(new OrchestrationTestHelpers.DoubleEchoAgent("agent1"))
+            .Build();
+
+        Assert.Null(workflow.Name);
+        Assert.Null(workflow.Description);
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(2)]
+    [InlineData(3)]
+    [InlineData(4)]
+    [InlineData(5)]
+    public async Task BuildGroupChat_AgentsRunInOrderAsync(int maxIterations)
+    {
+        const int NumAgents = 3;
+        var workflow = AgentWorkflowBuilder.CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = maxIterations })
+            .AddParticipants(new OrchestrationTestHelpers.DoubleEchoAgent("agent1"), new OrchestrationTestHelpers.DoubleEchoAgent("agent2"))
+            .AddParticipants(new OrchestrationTestHelpers.DoubleEchoAgent("agent3"))
+            .Build();
+
+        for (int iter = 0; iter < 3; iter++)
+        {
+            const string UserInput = "abc";
+            (string updateText, List<ChatMessage>? result, _, _) = await OrchestrationTestHelpers.RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, UserInput)]);
+
+            Assert.NotNull(result);
+            Assert.Equal(maxIterations + 1, result.Count);
+
+            Assert.Equal(ChatRole.User, result[0].Role);
+            Assert.Null(result[0].AuthorName);
+            Assert.Equal(UserInput, result[0].Text);
+
+            // The group-chat host broadcasts each new message (initial user input + each speaker's
+            // response) to every participant except the speaker that produced it. The selected
+            // speaker therefore sees only what's been broadcast to it since its previous turn.
+            string[] agentIds = ["agent1", "agent2", "agent3"];
+            List<string>[] buffers = new List<string>[NumAgents];
+            for (int a = 0; a < NumAgents; a++)
+            {
+                buffers[a] = [UserInput];
+            }
+
+            string[] texts = new string[maxIterations + 1];
+            texts[0] = UserInput;
+            string expectedTotal = string.Empty;
+            for (int i = 1; i < maxIterations + 1; i++)
+            {
+                int speakerIdx = (i - 1) % NumAgents;
+                string id = agentIds[speakerIdx];
+                string concatReceived = string.Concat(buffers[speakerIdx]);
+                texts[i] = $"{id}{Double(concatReceived)}";
+                buffers[speakerIdx].Clear();
+                for (int a = 0; a < NumAgents; a++)
+                {
+                    if (a == speakerIdx)
+                    {
+                        continue;
+                    }
+
+                    buffers[a].Add(texts[i]);
+                }
+
+                Assert.Equal(ChatRole.Assistant, result[i].Role);
+                Assert.Equal(id, result[i].AuthorName);
+                Assert.Equal(texts[i], result[i].Text);
+                expectedTotal += texts[i];
+            }
+
+            Assert.Equal(expectedTotal, updateText);
+            Assert.Equal(UserInput + expectedTotal, string.Concat(result));
+
+            static string Double(string s) => s + s;
+        }
+    }
+
+    [Fact]
+    public void Test_GroupChatWorkflowBuilder_DefaultDesignationsMatchSpec()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent a1 = new("agent1");
+        OrchestrationTestHelpers.DoubleEchoAgent a2 = new("agent2");
+        OrchestrationTestHelpers.DoubleEchoAgent a3 = new("agent3");
+
+        Workflow workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 1 })
+            .AddParticipants(a1, a2, a3)
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+
+        designations.Where(kvp => kvp.Value.Count == 0)
+            .Should().ContainSingle("group-chat host is the sole terminal output executor by default");
+        designations.Where(kvp => kvp.Value.Contains(OutputTag.Intermediate))
+            .Should().HaveCount(3, "every participant is designated intermediate by default");
+    }
+
+    [Fact]
+    public void Test_GroupChatWorkflowBuilder_ExplicitDesignationsReplaceDefaults()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent a1 = new("agent1");
+        OrchestrationTestHelpers.DoubleEchoAgent a2 = new("agent2");
+        OrchestrationTestHelpers.DoubleEchoAgent a3 = new("agent3");
+
+        Workflow workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 1 })
+            .AddParticipants(a1, a2, a3)
+            .WithOutputFrom(a1)
+            .WithIntermediateOutputFrom([a2])
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+
+        designations.Should().HaveCount(2,
+            "only the two explicitly-designated agents land on the inner builder; the host default is suppressed");
+        designations.Values.Where(tags => tags.Count == 0)
+            .Should().ContainSingle("agent1 is the only terminal designation");
+        designations.Values.Where(tags => tags.Contains(OutputTag.Intermediate))
+            .Should().ContainSingle("agent2 is the only intermediate designation");
+    }
+
+    [Fact]
+    public void Test_GroupChatWorkflowBuilder_DesignationForNonParticipantThrows()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent participant = new("p1");
+        OrchestrationTestHelpers.DoubleEchoAgent stranger = new("stranger");
+
+        GroupChatWorkflowBuilder builder = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 1 })
+            .AddParticipants(participant)
+            .WithOutputFrom(stranger);
+
+        Action build = () => builder.Build();
+        build.Should().Throw<InvalidOperationException>().WithMessage("*stranger*");
+    }
+
+    private sealed class RecordingAgent(string name) : AIAgent
+    {
+        public List<List<string>> Invocations { get; } = [];
+
+        public override string Name => name;
+
+        protected override ValueTask<AgentSession> CreateSessionCoreAsync(CancellationToken cancellationToken = default)
+            => new(new RecordingAgentSession());
+
+        protected override ValueTask<AgentSession> DeserializeSessionCoreAsync(JsonElement serializedState, JsonSerializerOptions? jsonSerializerOptions = null, CancellationToken cancellationToken = default)
+            => new(new RecordingAgentSession());
+
+        protected override ValueTask<JsonElement> SerializeSessionCoreAsync(AgentSession session, JsonSerializerOptions? jsonSerializerOptions = null, CancellationToken cancellationToken = default)
+            => default;
+
+        protected override Task<AgentResponse> RunCoreAsync(
+            IEnumerable<ChatMessage> messages, AgentSession? session = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default) =>
+            throw new NotImplementedException();
+
+        protected override async IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingAsync(
+            IEnumerable<ChatMessage> messages, AgentSession? session = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+        {
+            await Task.Yield();
+
+            this.Invocations.Add(messages.Select(m => m.Text).ToList());
+
+            string id = Guid.NewGuid().ToString("N");
+            yield return new AgentResponseUpdate(ChatRole.Assistant, name) { AuthorName = name, MessageId = id };
+        }
+    }
+
+    private sealed class RecordingAgentSession() : AgentSession();
+
+    [Fact]
+    public async Task BuildGroupChat_BroadcastsDeltaAndTargetsTurnTokenToSpeakerOnlyAsync()
+    {
+        var agentA = new RecordingAgent("agentA");
+        var agentB = new RecordingAgent("agentB");
+        var agentC = new RecordingAgent("agentC");
+
+        var workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = 4 })
+            .AddParticipants(agentA, agentB, agentC)
+            .Build();
+
+        const string UserInput = "hello";
+        (_, List<ChatMessage>? result, _, _) = await OrchestrationTestHelpers.RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, UserInput)]);
+
+        Assert.NotNull(result);
+        Assert.Equal(5, result.Count); // initial user input + 4 agent turns
+        Assert.Collection(
+            result,
+            m => Assert.Equal(UserInput, m.Text),
+            m => Assert.Equal("agentA", m.Text),
+            m => Assert.Equal("agentB", m.Text),
+            m => Assert.Equal("agentC", m.Text),
+            m => Assert.Equal("agentA", m.Text));
+
+        // Each agent's TurnToken fires exactly when it is the selected speaker — invocation counts
+        // confirm only the chosen participant receives a TurnToken on each round.
+        Assert.Equal(2, agentA.Invocations.Count);
+        Assert.Single(agentB.Invocations);
+        Assert.Single(agentC.Invocations);
+
+        // Turn 1: agentA is the first speaker. Initial broadcast went to every participant, so
+        // agentA's only buffered message is the user input.
+        Assert.Equal([UserInput], agentA.Invocations[0]);
+
+        // Turn 2: agentB. It received the initial broadcast (user input) plus turn-1 broadcast of
+        // agentA's response (agentA itself is excluded as the last speaker).
+        Assert.Equal([UserInput, "agentA"], agentB.Invocations[0]);
+
+        // Turn 3: agentC. It also received every broadcast so far (it has never been excluded).
+        Assert.Equal([UserInput, "agentA", "agentB"], agentC.Invocations[0]);
+
+        // Turn 4: agentA again. It was excluded on turn 2's broadcast (its own response), but
+        // received turn-3 (agentB's response) and turn-4 (agentC's response) deltas.
+        Assert.Equal(["agentB", "agentC"], agentA.Invocations[1]);
+    }
+
+    [Fact]
+    public async Task BuildGroupChat_UpdateHistoryAsync_FiltersBroadcastPayloadAsync()
+    {
+        var agentA = new RecordingAgent("agentA");
+        var agentB = new RecordingAgent("agentB");
+
+        var workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new PrefixingGroupChatManager(agents, "[broadcast] ") { MaximumIterationCount = 2 })
+            .AddParticipants(agentA, agentB)
+            .Build();
+
+        const string UserInput = "hello";
+        await OrchestrationTestHelpers.RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, UserInput)]);
+
+        // Turn 1: agentA's buffer contains only the initial broadcast, which UpdateHistoryAsync
+        // prefixed.
+        Assert.Equal(["[broadcast] hello"], agentA.Invocations[0]);
+
+        // Turn 2: agentB received both the initial broadcast and agentA's response — both passed
+        // through UpdateHistoryAsync before being broadcast.
+        Assert.Equal(["[broadcast] hello", "[broadcast] agentA"], agentB.Invocations[0]);
+    }
+
+    [Fact]
+    public async Task BuildGroupChat_CheckpointResumeMidConversation_PreservesIterationCursorAndBroadcastExclusionAsync()
+    {
+        const string UserInput = "hello";
+        const int MaxIterations = 6;
+
+        // --- Baseline: run the full conversation under checkpointing and capture every checkpoint
+        //     plus the final transcript. The same workflow + agents are reused for the resume,
+        //     because the runner enforces workflow-shape compatibility on ResumeStreamingAsync. ---
+        BaselineRunResult baseline = await RunGroupChatBaselineAsync(UserInput, MaxIterations);
+
+        // We need at least one mid-conversation checkpoint to resume from. The baseline produces a
+        // checkpoint per superstep, which for MaxIterations=6 yields many; we pick a checkpoint
+        // captured roughly midway so the resumed run still has work to do.
+        Assert.True(baseline.Checkpoints.Count >= 5,
+            $"expected at least 5 checkpoints in the baseline, got {baseline.Checkpoints.Count}");
+
+        int midIndex = baseline.Checkpoints.Count / 2;
+        CheckpointInfo midCheckpoint = baseline.Checkpoints[midIndex];
+
+        // Snapshot per-agent invocation counts before the resume so we can isolate the invocations
+        // produced after the checkpoint is restored.
+        int aPreCount = baseline.AgentA.Invocations.Count;
+        int bPreCount = baseline.AgentB.Invocations.Count;
+        int cPreCount = baseline.AgentC.Invocations.Count;
+
+        // --- Resume the same workflow from the mid-conversation checkpoint. ---
+        List<ChatMessage>? resumedResult = null;
+        await using (StreamingRun resumed = await baseline.Environment
+                                                          .ResumeStreamingAsync(baseline.Workflow, midCheckpoint))
+        {
+            await foreach (WorkflowEvent evt in resumed.WatchStreamAsync(blockOnPendingRequest: false))
+            {
+                if (evt is WorkflowOutputEvent o)
+                {
+                    resumedResult = o.As<List<ChatMessage>>();
+                }
+                else if (evt is WorkflowErrorEvent err)
+                {
+                    Assert.Fail($"Resumed workflow failed: {err.Exception}");
+                }
+            }
+        }
+
+        // (1) Iteration-count continuity: the resumed run terminates with exactly the same number
+        //     of turns the baseline produced — proves IterationCount was rehydrated and the manager
+        //     honored MaximumIterationCount across the boundary.
+        Assert.NotNull(resumedResult);
+        Assert.Equal(baseline.Result.Count, resumedResult!.Count);
+
+        // (2) Next-speaker consistency: the full transcript (initial input + every speaker's turn,
+        //     in order) matches the baseline — proves the round-robin cursor was restored.
+        List<string?> baselineTranscript = [.. baseline.Result.Select(m => m.Text)];
+        List<string?> resumedTranscript = [.. resumedResult.Select(m => m.Text)];
+        Assert.Equal(baselineTranscript, resumedTranscript);
+
+        // (3) Broadcast exclusion holds across resume: a RecordingAgent's response text is just its
+        //     own Name. Examine only the invocations recorded after the resume. If the host failed
+        //     to exclude the current speaker from its post-resume broadcasts, an agent's next
+        //     invocation buffer would contain its own previously produced response. Asserting that
+        //     no post-resume invocation input contains the invoking agent's own name proves the
+        //     exclusion was preserved through checkpoint+restore.
+        AssertPostResumeBroadcastExclusion(baseline.AgentA, aPreCount);
+        AssertPostResumeBroadcastExclusion(baseline.AgentB, bPreCount);
+        AssertPostResumeBroadcastExclusion(baseline.AgentC, cPreCount);
+
+        // Sanity: at least one agent was actually invoked after the resume; otherwise the test
+        // would trivially pass even if the host stopped scheduling turns after restore.
+        int totalPost = baseline.AgentA.Invocations.Count - aPreCount
+                      + (baseline.AgentB.Invocations.Count - bPreCount)
+                      + (baseline.AgentC.Invocations.Count - cPreCount);
+        Assert.True(totalPost > 0, "at least one agent should be invoked after resuming from the mid-conversation checkpoint");
+
+        static void AssertPostResumeBroadcastExclusion(RecordingAgent agent, int preCount)
+        {
+            for (int i = preCount; i < agent.Invocations.Count; i++)
+            {
+                Assert.DoesNotContain(agent.Name, agent.Invocations[i]);
+            }
+        }
+    }
+
+    private sealed record BaselineRunResult(
+        Workflow Workflow,
+        InProcessExecutionEnvironment Environment,
+        RecordingAgent AgentA,
+        RecordingAgent AgentB,
+        RecordingAgent AgentC,
+        List<ChatMessage> Result,
+        List<CheckpointInfo> Checkpoints,
+        CheckpointManager CheckpointManager);
+
+    private static async Task<BaselineRunResult> RunGroupChatBaselineAsync(string userInput, int maxIterations)
+    {
+        var agentA = new RecordingAgent("agentA");
+        var agentB = new RecordingAgent("agentB");
+        var agentC = new RecordingAgent("agentC");
+
+        Workflow workflow = AgentWorkflowBuilder
+            .CreateGroupChatBuilderWith(agents => new RoundRobinGroupChatManager(agents) { MaximumIterationCount = maxIterations })
+            .AddParticipants(agentA, agentB, agentC)
+            .Build();
+
+        CheckpointManager checkpointMgr = CheckpointManager.CreateInMemory();
+        InProcessExecutionEnvironment env = ExecutionEnvironment.InProcess_Lockstep
+                                                                .ToWorkflowExecutionEnvironment()
+                                                                .WithCheckpointing(checkpointMgr);
+
+        List<CheckpointInfo> checkpoints = [];
+        List<ChatMessage>? finalResult = null;
+
+        await using (StreamingRun run = await env.OpenStreamingAsync(workflow))
+        {
+            await run.TrySendMessageAsync(new List<ChatMessage> { new(ChatRole.User, userInput) });
+            await run.TrySendMessageAsync(new TurnToken(emitEvents: true));
+
+            await foreach (WorkflowEvent evt in run.WatchStreamAsync(blockOnPendingRequest: false))
+            {
+                switch (evt)
+                {
+                    case SuperStepCompletedEvent step when step.CompletionInfo?.Checkpoint is { } cp:
+                        checkpoints.Add(cp);
+                        break;
+                    case WorkflowOutputEvent o:
+                        finalResult = o.As<List<ChatMessage>>();
+                        break;
+                    case WorkflowErrorEvent err:
+                        Assert.Fail($"Baseline workflow failed: {err.Exception}");
+                        break;
+                }
+            }
+        }
+
+        Assert.NotNull(finalResult);
+        return new BaselineRunResult(workflow, env, agentA, agentB, agentC, finalResult!, checkpoints, checkpointMgr);
+    }
+
+    private sealed class PrefixingGroupChatManager(IReadOnlyList<AIAgent> agents, string prefix) : RoundRobinGroupChatManager(agents)
+    {
+        protected internal override ValueTask<IEnumerable<ChatMessage>> UpdateHistoryAsync(
+            IReadOnlyList<ChatMessage> history,
+            CancellationToken cancellationToken = default)
+        {
+            IEnumerable<ChatMessage> prefixed =
+                history.Select(m => new ChatMessage(m.Role, $"{prefix}{m.Text}") { AuthorName = m.AuthorName });
+
+            return new(prefixed);
+        }
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/HandoffWorkflowBuilderTests.cs

@@ -0,0 +1,77 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using FluentAssertions;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+/// <summary>
+/// Tests focused on <see cref="HandoffWorkflowBuilder"/>'s output-designation surface —
+/// the Python-aligned defaults applied at <see cref="HandoffWorkflowBuilderCore{TBuilder}.Build"/>
+/// when the user has not made explicit designations, and the memoized
+/// <c>WithOutputFrom</c> / <c>WithIntermediateOutputFrom</c> replay otherwise.
+/// </summary>
+#pragma warning disable MAAIW001 // Experimental: HandoffWorkflowBuilder
+public class HandoffWorkflowBuilderTests
+{
+    [Fact]
+    public void Test_HandoffWorkflowBuilder_DefaultDesignationsMatchSpec()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent coordinator = new("coordinator");
+        OrchestrationTestHelpers.DoubleEchoAgent specialist = new("specialist");
+
+        Workflow workflow = AgentWorkflowBuilder
+            .CreateHandoffBuilderWith(coordinator)
+            .WithHandoff(coordinator, specialist)
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+
+        designations.Where(kvp => kvp.Value.Count == 0)
+            .Should().ContainSingle("the handoff end executor is the sole terminal output by default");
+        designations.Where(kvp => kvp.Value.Contains(OutputTag.Intermediate))
+            .Should().HaveCount(2, "both the coordinator and the specialist are designated intermediate by default");
+    }
+
+    [Fact]
+    public void Test_HandoffWorkflowBuilder_ExplicitDesignationsReplaceDefaults()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent coordinator = new("coordinator");
+        OrchestrationTestHelpers.DoubleEchoAgent specialist = new("specialist");
+
+        Workflow workflow = AgentWorkflowBuilder
+            .CreateHandoffBuilderWith(coordinator)
+            .WithHandoff(coordinator, specialist)
+            .WithOutputFrom(coordinator)
+            .WithIntermediateOutputFrom([specialist])
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+
+        designations.Should().HaveCount(2,
+            "only the user-specified designations land on the inner builder; the handoff-end default is suppressed");
+        designations.Values.Where(tags => tags.Count == 0)
+            .Should().ContainSingle("coordinator is the only terminal designation");
+        designations.Values.Where(tags => tags.Contains(OutputTag.Intermediate))
+            .Should().ContainSingle("specialist is the only intermediate designation");
+    }
+
+    [Fact]
+    public void Test_HandoffWorkflowBuilder_DesignationForNonParticipantThrows()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent coordinator = new("coordinator");
+        OrchestrationTestHelpers.DoubleEchoAgent specialist = new("specialist");
+        OrchestrationTestHelpers.DoubleEchoAgent stranger = new("stranger");
+
+        HandoffWorkflowBuilder builder = AgentWorkflowBuilder
+            .CreateHandoffBuilderWith(coordinator)
+            .WithHandoff(coordinator, specialist)
+            .WithIntermediateOutputFrom([stranger]);
+
+        Action build = () => builder.Build();
+        build.Should().Throw<InvalidOperationException>().WithMessage("*stranger*");
+    }
+}
+#pragma warning restore MAAIW001

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/InputWaiterTests.cs

@@ -122,50 +122,3 @@ public sealed class InputWaiterTests : IDisposable
         await waitTask;
     }
 }
-
-public class OutputFilterTests
-{
-    private static OutputFilter CreateFilterWithOutputFrom(string outputExecutorId)
-    {
-        NoOpExecutor start = new("start");
-        NoOpExecutor end = new("end");
-
-        Workflow workflow = new WorkflowBuilder("start")
-            .AddEdge(start, end)
-            .WithOutputFrom(outputExecutorId == "end" ? end : start)
-            .Build();
-
-        return new OutputFilter(workflow);
-    }
-
-    [Fact]
-    public void OutputFilter_CanOutput_ReturnsTrueForRegisteredExecutor()
-    {
-        OutputFilter filter = CreateFilterWithOutputFrom("end");
-
-        filter.CanOutput("end", "some output").Should().BeTrue("the executor was registered via WithOutputFrom");
-    }
-
-    [Fact]
-    public void OutputFilter_CanOutput_ReturnsFalseForUnregisteredExecutor()
-    {
-        OutputFilter filter = CreateFilterWithOutputFrom("end");
-
-        filter.CanOutput("start", "some output").Should().BeFalse("start was not registered as an output executor");
-    }
-
-    [Fact]
-    public void OutputFilter_CanOutput_ReturnsFalseForNonExistentExecutor()
-    {
-        OutputFilter filter = CreateFilterWithOutputFrom("end");
-
-        filter.CanOutput("nonexistent", "some output").Should().BeFalse("an executor not in the workflow should not be an output executor");
-    }
-
-    private sealed class NoOpExecutor(string id) : Executor(id)
-    {
-        protected override ProtocolBuilder ConfigureProtocol(ProtocolBuilder protocolBuilder)
-            => protocolBuilder.ConfigureRoutes(routeBuilder =>
-                                               routeBuilder.AddHandler<object>((msg, ctx) => ctx.SendMessageAsync(msg)));
-    }
-}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/JsonSerializationTests.cs

@@ -187,8 +187,12 @@ public class JsonSerializationTests
         actual.InputType.Should().Match(prototype.InputType.CreateValidator());
         actual.StartExecutorId.Should().Be(prototype.StartExecutorId);
 
-        actual.OutputExecutorIds.Should().HaveCount(prototype.OutputExecutorIds.Count)
-                            .And.AllSatisfy(id => prototype.OutputExecutorIds.Contains(id));
+        actual.OutputExecutorIds.Should().HaveCount(prototype.OutputExecutorIds.Count);
+        foreach (KeyValuePair<string, HashSet<OutputTag>> kvp in prototype.OutputExecutorIds)
+        {
+            actual.OutputExecutorIds.Should().ContainKey(kvp.Key);
+            actual.OutputExecutorIds[kvp.Key].Should().BeEquivalentTo(kvp.Value);
+        }
 
         void ValidateExecutorDictionary(Dictionary<string, ExecutorInfo> expected,
                                         Dictionary<string, List<EdgeInfo>> expectedEdges,
@@ -788,6 +792,34 @@ public class JsonSerializationTests
         result.IsTakingTurn.Should().Be(prototype.IsTakingTurn);
     }
 
+    [Fact]
+    public void Test_GroupChatManagerState_JsonRoundtrip()
+    {
+        // Arrange
+        GroupChatManagerState prototype = new(IterationCount: 7);
+
+        // Act
+        GroupChatManagerState result = RunJsonRoundtrip(prototype);
+
+        // Assert
+        result.Should().Be(prototype);
+        result.IterationCount.Should().Be(prototype.IterationCount);
+    }
+
+    [Fact]
+    public void Test_RoundRobinGroupChatManagerState_JsonRoundtrip()
+    {
+        // Arrange
+        RoundRobinGroupChatManagerState prototype = new(NextIndex: 3);
+
+        // Act
+        RoundRobinGroupChatManagerState result = RunJsonRoundtrip(prototype);
+
+        // Assert
+        result.Should().Be(prototype);
+        result.NextIndex.Should().Be(prototype.NextIndex);
+    }
+
     /// <summary>
     /// Verifies that the default behavior (without AllowOutOfOrderMetadataProperties) fails
     /// when $type metadata is not the first property, demonstrating the PostgreSQL jsonb issue.

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/MagenticOrchestrationTests.cs

@@ -361,6 +361,64 @@ public class MagenticOrchestrationTests
         runResult.Result![0].Text.Should().Contain("Multi-round task completed!");
     }
 
+    [Fact]
+    public async Task RunCoordinationRound_Forwards_Participant_Reply_To_ManagerAsync()
+    {
+        // Regression: MagenticOrchestrator.TakeTurnAsync used to drop the `messages`
+        // parameter on subsequent turns, so participant replies never reached the
+        // manager's ChatHistory. The manager then re-dispatched the same speaker
+        // every round until MaxRounds. Assert that round-2's progress-ledger call
+        // actually sees the worker's reply in its input.
+
+        const string TaskPrompt = "Echo back this exact magentic-regression-marker";
+
+        List<ChatMessage> factsResponse = CreatePlanResponse("Facts");
+        List<ChatMessage> planResponse = CreatePlanResponse("Plan");
+        List<ChatMessage> round1Ledger = CreateProgressLedgerResponse(
+            isRequestSatisfied: false,
+            isInLoop: false,
+            isProgressBeingMade: true,
+            nextSpeaker: "Worker",
+            instructionOrQuestion: TaskPrompt);
+        List<ChatMessage> round2Ledger = CreateProgressLedgerResponse(
+            isRequestSatisfied: true,
+            isInLoop: false,
+            isProgressBeingMade: true,
+            nextSpeaker: "Worker",
+            instructionOrQuestion: "Done");
+        List<ChatMessage> finalAnswer = CreateFinalAnswerResponse("All good");
+
+        RecordingReplayAgent manager = new(
+            [factsResponse, planResponse, round1Ledger, round2Ledger, finalAnswer],
+            name: "Manager");
+        TestEchoAgent worker = new(name: "Worker");
+
+        Workflow workflow = new MagenticWorkflowBuilder(manager)
+            .AddParticipants(worker)
+            .RequirePlanSignoff(false)
+            .Build();
+
+        WorkflowRunResult runResult = await RunMagenticWorkflowAsync(
+            workflow,
+            [new ChatMessage(ChatRole.User, TaskPrompt)]);
+
+        runResult.Result.Should().NotBeNull();
+        runResult.Result![0].Text.Should().Contain("All good");
+
+        // Calls in order: facts, plan, ledger1, ledger2, finalAnswer.
+        manager.RecordedInputs.Should().HaveCount(5);
+
+        manager.RecordedInputs[3].Should().Contain(
+            m => m.Role == ChatRole.Assistant
+              && m.AuthorName == "Worker"
+              && m.Text.Contains(TaskPrompt),
+            "round-2 progress ledger must see the worker's reply; without it the manager loops to MaxRounds");
+
+        manager.RecordedInputs[4].Should().Contain(
+            m => m.Role == ChatRole.Assistant && m.AuthorName == "Worker",
+            "final-answer synthesis must see what participants actually said");
+    }
+
     [Fact]
     public async Task PlanReview_Revised_Triggers_ReplanAsync()
     {

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/MagenticWorkflowBuilderTests.cs

@@ -0,0 +1,79 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using FluentAssertions;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+/// <summary>
+/// Tests focused on <see cref="MagenticWorkflowBuilder"/>'s output-designation surface —
+/// the Python-aligned defaults applied at <see cref="MagenticWorkflowBuilder.Build"/> when
+/// the user has not made explicit designations, and the memoized
+/// <c>WithOutputFrom</c> / <c>WithIntermediateOutputFrom</c> replay otherwise.
+/// </summary>
+#pragma warning disable MAAIW001 // Experimental: MagenticWorkflowBuilder
+public class MagenticWorkflowBuilderTests
+{
+    [Fact]
+    public void Test_MagenticWorkflowBuilder_DefaultDesignationsMatchSpec()
+    {
+        TestReplayAgent manager = new(name: "Manager");
+        TestEchoAgent member1 = new(name: "Worker1");
+        TestEchoAgent member2 = new(name: "Worker2");
+
+        Workflow workflow = new MagenticWorkflowBuilder(manager)
+            .AddParticipants(member1, member2)
+            .RequirePlanSignoff(false)
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+
+        designations.Where(kvp => kvp.Value.Count == 0)
+            .Should().ContainSingle("the Magentic orchestrator is the sole terminal output by default");
+        designations.Where(kvp => kvp.Value.Contains(OutputTag.Intermediate))
+            .Should().HaveCount(2, "every team member is designated intermediate by default");
+    }
+
+    [Fact]
+    public void Test_MagenticWorkflowBuilder_ExplicitDesignationsReplaceDefaults()
+    {
+        TestReplayAgent manager = new(name: "Manager");
+        TestEchoAgent member1 = new(name: "Worker1");
+        TestEchoAgent member2 = new(name: "Worker2");
+
+        Workflow workflow = new MagenticWorkflowBuilder(manager)
+            .AddParticipants(member1, member2)
+            .RequirePlanSignoff(false)
+            .WithOutputFrom(member1)
+            .WithIntermediateOutputFrom([member2])
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+
+        designations.Should().HaveCount(2,
+            "only the user-specified designations land on the inner builder; the orchestrator default is suppressed");
+        designations.Values.Where(tags => tags.Count == 0)
+            .Should().ContainSingle("member1 is the only terminal designation");
+        designations.Values.Where(tags => tags.Contains(OutputTag.Intermediate))
+            .Should().ContainSingle("member2 is the only intermediate designation");
+    }
+
+    [Fact]
+    public void Test_MagenticWorkflowBuilder_DesignationForNonParticipantThrows()
+    {
+        TestReplayAgent manager = new(name: "Manager");
+        TestEchoAgent member = new(name: "Worker");
+        TestEchoAgent stranger = new(name: "Stranger");
+
+        MagenticWorkflowBuilder builder = new MagenticWorkflowBuilder(manager)
+            .AddParticipants(member)
+            .RequirePlanSignoff(false)
+            .WithIntermediateOutputFrom([stranger]);
+
+        Action build = () => builder.Build();
+        build.Should().Throw<InvalidOperationException>().WithMessage("*Stranger*");
+    }
+}
+#pragma warning restore MAAIW001

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/OrchestrationTestHelpers.cs

@@ -0,0 +1,131 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Text;
+using System.Text.Json;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Agents.AI.Workflows.InProc;
+using Microsoft.Extensions.AI;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+/// <summary>
+/// Container for shared test helpers used by every orchestration-builder test class —
+/// the <c>DoubleEchoAgent</c> family and the <c>RunWorkflow*</c> methods. The actual
+/// test methods live in per-builder files (<c>SequentialWorkflowBuilderTests</c>,
+/// <c>ConcurrentWorkflowBuilderTests</c>, <c>GroupChatWorkflowBuilderTests</c>, etc.).
+/// </summary>
+public static class OrchestrationTestHelpers
+{
+    internal class DoubleEchoAgent(string name) : AIAgent
+    {
+        public override string Name => name;
+
+        protected override ValueTask<AgentSession> CreateSessionCoreAsync(CancellationToken cancellationToken = default)
+            => new(new DoubleEchoAgentSession());
+
+        protected override ValueTask<AgentSession> DeserializeSessionCoreAsync(JsonElement serializedState, JsonSerializerOptions? jsonSerializerOptions = null, CancellationToken cancellationToken = default)
+            => new(new DoubleEchoAgentSession());
+
+        protected override ValueTask<JsonElement> SerializeSessionCoreAsync(AgentSession session, JsonSerializerOptions? jsonSerializerOptions = null, CancellationToken cancellationToken = default)
+            => default;
+
+        protected override Task<AgentResponse> RunCoreAsync(
+            IEnumerable<ChatMessage> messages, AgentSession? session = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default) =>
+            throw new NotImplementedException();
+
+        protected override async IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingAsync(
+            IEnumerable<ChatMessage> messages, AgentSession? session = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+        {
+            await Task.Yield();
+
+            var contents = messages.SelectMany(m => m.Contents).ToList();
+            string id = Guid.NewGuid().ToString("N");
+            yield return new AgentResponseUpdate(ChatRole.Assistant, this.Name) { AuthorName = this.Name, MessageId = id };
+            yield return new AgentResponseUpdate(ChatRole.Assistant, contents) { AuthorName = this.Name, MessageId = id };
+            yield return new AgentResponseUpdate(ChatRole.Assistant, contents) { AuthorName = this.Name, MessageId = id };
+        }
+    }
+
+    internal sealed class DoubleEchoAgentSession() : AgentSession();
+
+    internal sealed class DoubleEchoAgentWithBarrier(string name, StrongBox<TaskCompletionSource<bool>> barrier, StrongBox<int> remaining) : DoubleEchoAgent(name)
+    {
+        protected override async IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingAsync(
+            IEnumerable<ChatMessage> messages, AgentSession? session = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+        {
+            if (Interlocked.Decrement(ref remaining.Value) == 0)
+            {
+                barrier.Value!.SetResult(true);
+            }
+
+            await barrier.Value!.Task.ConfigureAwait(false);
+
+            await foreach (var update in base.RunCoreStreamingAsync(messages, session, options, cancellationToken))
+            {
+                await Task.Yield();
+                yield return update;
+            }
+        }
+    }
+
+    internal sealed record WorkflowRunResult(string UpdateText, List<ChatMessage>? Result, CheckpointInfo? LastCheckpoint, List<RequestInfoEvent> PendingRequests);
+
+    internal static async Task<WorkflowRunResult> RunWorkflowCheckpointedAsync(
+        Workflow workflow, List<ChatMessage> input, InProcessExecutionEnvironment environment, CheckpointInfo? fromCheckpoint = null)
+    {
+        await using StreamingRun run =
+            fromCheckpoint != null ? await environment.ResumeStreamingAsync(workflow, fromCheckpoint)
+                                   : await environment.OpenStreamingAsync(workflow);
+
+        await run.TrySendMessageAsync(input);
+        await run.TrySendMessageAsync(new TurnToken(emitEvents: true));
+
+        return await ProcessWorkflowRunAsync(run);
+    }
+
+    internal static async Task<WorkflowRunResult> ProcessWorkflowRunAsync(StreamingRun run)
+    {
+        StringBuilder sb = new();
+        WorkflowOutputEvent? output = null;
+        CheckpointInfo? lastCheckpoint = null;
+
+        List<RequestInfoEvent> pendingRequests = [];
+
+        await foreach (WorkflowEvent evt in run.WatchStreamAsync(blockOnPendingRequest: false).ConfigureAwait(false))
+        {
+            switch (evt)
+            {
+                case AgentResponseUpdateEvent responseUpdate:
+                    sb.Append(responseUpdate.Data);
+                    break;
+
+                case RequestInfoEvent requestInfo:
+                    pendingRequests.Add(requestInfo);
+                    break;
+
+                case WorkflowOutputEvent e:
+                    output = e;
+                    break;
+
+                case WorkflowErrorEvent errorEvent:
+                    Assert.Fail($"Workflow execution failed with error: {errorEvent.Exception}");
+                    break;
+
+                case SuperStepCompletedEvent stepCompleted:
+                    lastCheckpoint = stepCompleted.CompletionInfo?.Checkpoint;
+                    break;
+            }
+        }
+
+        return new(sb.ToString(), output?.As<List<ChatMessage>>(), lastCheckpoint, pendingRequests);
+    }
+
+    internal static Task<WorkflowRunResult> RunWorkflowAsync(
+        Workflow workflow, List<ChatMessage> input, ExecutionEnvironment executionEnvironment = ExecutionEnvironment.InProcess_Lockstep)
+        => RunWorkflowCheckpointedAsync(workflow, input, executionEnvironment.ToWorkflowExecutionEnvironment());
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/OutputFilterTests.cs

@@ -0,0 +1,108 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Collections.Generic;
+using FluentAssertions;
+using Microsoft.Agents.AI.Workflows.Execution;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+public class OutputFilterTests
+{
+    private static OutputFilter CreateFilterWithOutputFrom(string outputExecutorId)
+    {
+        NoOpExecutor start = new("start");
+        NoOpExecutor end = new("end");
+
+        Workflow workflow = new WorkflowBuilder("start")
+            .AddEdge(start, end)
+            .WithOutputFrom(outputExecutorId == "end" ? end : start)
+            .Build();
+
+        return new OutputFilter(workflow);
+    }
+
+    [Fact]
+    public void OutputFilter_CanOutput_ReturnsTrueForRegisteredExecutor()
+    {
+        OutputFilter filter = CreateFilterWithOutputFrom("end");
+
+        filter.CanOutput("end", "some output").Should().BeTrue("the executor was registered via WithOutputFrom");
+    }
+
+    [Fact]
+    public void OutputFilter_CanOutput_ReturnsFalseForUnregisteredExecutor()
+    {
+        OutputFilter filter = CreateFilterWithOutputFrom("end");
+
+        filter.CanOutput("start", "some output").Should().BeFalse("start was not registered as an output executor");
+    }
+
+    [Fact]
+    public void OutputFilter_CanOutput_ReturnsFalseForNonExistentExecutor()
+    {
+        OutputFilter filter = CreateFilterWithOutputFrom("end");
+
+        filter.CanOutput("nonexistent", "some output").Should().BeFalse("an executor not in the workflow should not be an output executor");
+    }
+
+    [Fact]
+    public void Test_OutputFilter_ReturnsEmptyTagSetWhenRegisteredViaWithOutputFrom()
+    {
+        OutputFilter filter = CreateFilterWithOutputFrom("end");
+
+        filter.TryGetTags("end", out HashSet<OutputTag>? tags).Should().BeTrue();
+        tags.Should().NotBeNull().And.BeEmpty("terminal designation carries no tag");
+    }
+
+    [Fact]
+    public void Test_OutputFilter_ReturnsIntermediateTagWhenRegisteredViaWithIntermediateOutputFrom()
+    {
+        NoOpExecutor start = new("start");
+        NoOpExecutor end = new("end");
+
+        Workflow workflow = new WorkflowBuilder("start")
+            .AddEdge(start, end)
+            .WithIntermediateOutputFrom([end])
+            .Build();
+
+        OutputFilter filter = new(workflow);
+
+        filter.TryGetTags("end", out HashSet<OutputTag>? tags).Should().BeTrue();
+        tags.Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+    }
+
+    [Fact]
+    public void Test_OutputFilter_ReturnsIntermediateTagForAccumulatedDesignation()
+    {
+        NoOpExecutor start = new("start");
+        NoOpExecutor end = new("end");
+
+        Workflow workflow = new WorkflowBuilder("start")
+            .AddEdge(start, end)
+            .WithOutputFrom(end)
+            .WithIntermediateOutputFrom([end])
+            .Build();
+
+        OutputFilter filter = new(workflow);
+
+        filter.TryGetTags("end", out HashSet<OutputTag>? tags).Should().BeTrue();
+        tags.Should().BeEquivalentTo(new[] { OutputTag.Intermediate },
+            "terminal designation contributes no tag; the union is the intermediate set");
+    }
+
+    [Fact]
+    public void Test_OutputFilter_TryGetTagsReturnsFalseForUnregisteredExecutor()
+    {
+        OutputFilter filter = CreateFilterWithOutputFrom("end");
+
+        filter.TryGetTags("start", out HashSet<OutputTag>? tags).Should().BeFalse();
+        tags.Should().BeNull();
+    }
+
+    private sealed class NoOpExecutor(string id) : Executor(id)
+    {
+        protected override ProtocolBuilder ConfigureProtocol(ProtocolBuilder protocolBuilder)
+            => protocolBuilder.ConfigureRoutes(routeBuilder =>
+                                               routeBuilder.AddHandler<object>((msg, ctx) => ctx.SendMessageAsync(msg)));
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/OutputTagTests.cs

@@ -0,0 +1,77 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Collections.Generic;
+using System.Reflection;
+using System.Text.Json;
+using FluentAssertions;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+public class OutputTagTests
+{
+    [Fact]
+    public void Test_OutputTag_KnownValues()
+    {
+        OutputTag.Intermediate.Value.Should().Be("intermediate");
+    }
+
+    [Fact]
+    public void Test_OutputTag_EqualityIsOrdinalOnValue()
+    {
+        OutputTag.Intermediate.Should().Be(OutputTag.Intermediate);
+        (OutputTag.Intermediate == OutputTag.Intermediate).Should().BeTrue();
+
+        // Same Value via independent construction (via JSON round-trip below) is equal.
+        OutputTag rebuilt = JsonSerializer.Deserialize<OutputTag>("\"intermediate\"", WorkflowsJsonUtilities.DefaultOptions);
+        rebuilt.Should().Be(OutputTag.Intermediate);
+    }
+
+    [Fact]
+    public void Test_OutputTag_DefaultStructValueIsDistinct()
+    {
+        OutputTag def = default;
+        def.Value.Should().BeNull();
+        def.Should().NotBe(OutputTag.Intermediate);
+        def.GetHashCode().Should().Be(0);
+
+        HashSet<OutputTag> set = [OutputTag.Intermediate];
+        set.Contains(def).Should().BeFalse("default(OutputTag) must not collide with the well-known singleton in a HashSet");
+    }
+
+    [Fact]
+    public void Test_OutputTag_GetHashCodeMatchesEquals()
+    {
+        OutputTag a = OutputTag.Intermediate;
+        OutputTag b = JsonSerializer.Deserialize<OutputTag>("\"intermediate\"", WorkflowsJsonUtilities.DefaultOptions);
+
+        a.Equals(b).Should().BeTrue();
+        a.GetHashCode().Should().Be(b.GetHashCode());
+    }
+
+    [Fact]
+    public void Test_OutputTag_JsonConverter_RoundtripsValueAsString()
+    {
+        string intermediateJson = JsonSerializer.Serialize(OutputTag.Intermediate, WorkflowsJsonUtilities.DefaultOptions);
+        intermediateJson.Should().Be("\"intermediate\"");
+
+        OutputTag back = JsonSerializer.Deserialize<OutputTag>("\"intermediate\"", WorkflowsJsonUtilities.DefaultOptions);
+        back.Should().Be(OutputTag.Intermediate);
+
+        OutputTag fromUnknown = JsonSerializer.Deserialize<OutputTag>("\"custom\"", WorkflowsJsonUtilities.DefaultOptions);
+        fromUnknown.Value.Should().Be("custom");
+    }
+
+    [Fact]
+    public void Test_OutputTag_ConstructorIsInternal()
+    {
+        ConstructorInfo? ctor = typeof(OutputTag).GetConstructor(
+            BindingFlags.Instance | BindingFlags.NonPublic,
+            binder: null,
+            types: [typeof(string)],
+            modifiers: null);
+
+        ctor.Should().NotBeNull("OutputTag(string) must exist as an internal constructor");
+        ctor!.IsAssembly.Should().BeTrue("OutputTag(string) must be `internal` so external assemblies cannot synthesize tags");
+        ctor.IsPublic.Should().BeFalse();
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/RecordingReplayAgent.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using Microsoft.Extensions.AI;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+/// <summary>
+/// A <see cref="TestReplayAgent"/> that records the input messages it receives on each call.
+/// Used by tests that need to assert what context the agent was actually handed.
+/// </summary>
+internal sealed class RecordingReplayAgent(List<List<ChatMessage>> messages, string? id = null, string? name = null)
+    : TestReplayAgent(messages, id, name)
+{
+    public List<List<ChatMessage>> RecordedInputs { get; } = [];
+
+    protected override async IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingAsync(
+        IEnumerable<ChatMessage> messages,
+        AgentSession? session = null,
+        AgentRunOptions? options = null,
+        [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        this.RecordedInputs.Add(messages.ToList());
+        await foreach (AgentResponseUpdate update in base.RunCoreStreamingAsync(messages, session, options, cancellationToken))
+        {
+            yield return update;
+        }
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/RoundRobinGroupChatManagerTests.cs

@@ -136,4 +136,55 @@ public class RoundRobinGroupChatManagerTests
         FluentActions.Invoking(() => new RoundRobinGroupChatManager([]))
             .Should().Throw<System.ArgumentException>();
     }
+
+    [Fact]
+    public async Task RoundRobinGroupChat_CheckpointRoundTrip_PreservesIterationCountAndCursorAsync()
+    {
+        TestEchoAgent agent1 = new(id: "agent1");
+        TestEchoAgent agent2 = new(id: "agent2");
+        TestEchoAgent agent3 = new(id: "agent3");
+        List<AIAgent> agents = [agent1, agent2, agent3];
+        List<ChatMessage> history = [];
+
+        TestRunState sharedState = new();
+        TestWorkflowContext sourceContext = new("gcm-host", sharedState);
+        TestWorkflowContext sinkContext = new("gcm-host", sharedState);
+
+        RoundRobinGroupChatManager source = new(agents);
+        await source.SelectNextAgentAsync(history); // cursor -> agent2
+        source.IterationCount = 7;
+
+        await source.CheckpointAsync(sourceContext);
+
+        RoundRobinGroupChatManager restored = new(agents);
+        restored.IterationCount.Should().Be(0, "freshly constructed manager has no iteration count");
+
+        await restored.RestoreCheckpointAsync(sinkContext);
+
+        restored.IterationCount.Should().Be(7, "the base hook must rehydrate IterationCount");
+
+        AIAgent next = await restored.SelectNextAgentAsync(history);
+        next.Should().BeSameAs(agent2, "the round-robin cursor should resume where the source left off");
+    }
+
+    [Fact]
+    public async Task RoundRobinGroupChat_RestoreWithoutCheckpoint_DefaultsToZeroStateAsync()
+    {
+        TestEchoAgent agent1 = new(id: "agent1");
+        TestEchoAgent agent2 = new(id: "agent2");
+        List<AIAgent> agents = [agent1, agent2];
+        List<ChatMessage> history = [];
+
+        TestWorkflowContext emptyContext = new("gcm-host");
+
+        RoundRobinGroupChatManager manager = new(agents);
+        manager.IterationCount = 3;
+        await manager.SelectNextAgentAsync(history); // cursor advanced
+
+        await manager.RestoreCheckpointAsync(emptyContext);
+
+        manager.IterationCount.Should().Be(0, "restore from an empty checkpoint should clear IterationCount");
+        AIAgent next = await manager.SelectNextAgentAsync(history);
+        next.Should().BeSameAs(agent1, "restore from an empty checkpoint should reset the cursor to the first agent");
+    }
 }

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/SequentialWorkflowBuilderTests.cs

@@ -0,0 +1,183 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using FluentAssertions;
+using Microsoft.Agents.AI.Workflows.UnitTests.Futures;
+using Microsoft.Extensions.AI;
+
+namespace Microsoft.Agents.AI.Workflows.UnitTests;
+
+public class SequentialWorkflowBuilderTests
+{
+    [Fact]
+    public void Test_SequentialWorkflowBuilder_InvalidArguments_Throws()
+    {
+        Assert.Throws<ArgumentNullException>("agents", () => new SequentialWorkflowBuilder(null!));
+        Assert.Throws<ArgumentException>("agents", () => new SequentialWorkflowBuilder().Build());
+
+        Assert.Throws<ArgumentNullException>("agents", () => AgentWorkflowBuilder.BuildSequential(workflowName: null!, null!));
+        Assert.Throws<ArgumentException>("agents", () => AgentWorkflowBuilder.BuildSequential());
+        Assert.Throws<ArgumentNullException>("agents", () => AgentWorkflowBuilder.CreateSequentialBuilderWith(null!));
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(2)]
+    [InlineData(3)]
+    [InlineData(4)]
+    [InlineData(5)]
+    public async Task Test_SequentialWorkflowBuilder_AgentsRunInOrderAsync(int numAgents)
+    {
+        var workflow = new SequentialWorkflowBuilder(
+            from i in Enumerable.Range(1, numAgents)
+            select new OrchestrationTestHelpers.DoubleEchoAgent($"agent{i}"))
+            .Build();
+
+        for (int iter = 0; iter < 3; iter++)
+        {
+            const string UserInput = "abc";
+            (string updateText, List<ChatMessage>? result, _, _) =
+                await OrchestrationTestHelpers.RunWorkflowAsync(workflow, [new ChatMessage(ChatRole.User, UserInput)]);
+
+            Assert.NotNull(result);
+            Assert.Equal(numAgents + 1, result.Count);
+
+            Assert.Equal(ChatRole.User, result[0].Role);
+            Assert.Null(result[0].AuthorName);
+            Assert.Equal(UserInput, result[0].Text);
+
+            string[] texts = new string[numAgents + 1];
+            texts[0] = UserInput;
+            string expectedTotal = string.Empty;
+            for (int i = 1; i < numAgents + 1; i++)
+            {
+                string id = $"agent{((i - 1) % numAgents) + 1}";
+                texts[i] = $"{id}{Double(string.Concat(texts.Take(i)))}";
+                Assert.Equal(ChatRole.Assistant, result[i].Role);
+                Assert.Equal(id, result[i].AuthorName);
+                Assert.Equal(texts[i], result[i].Text);
+                expectedTotal += texts[i];
+            }
+
+            Assert.Equal(expectedTotal, updateText);
+            Assert.Equal(UserInput + expectedTotal, string.Concat(result));
+
+            static string Double(string s) => s + s;
+        }
+    }
+
+    [Fact]
+    public void Test_SequentialWorkflowBuilder_DefaultDesignationsMatchSpec()
+    {
+        Workflow workflow = new SequentialWorkflowBuilder(
+            new OrchestrationTestHelpers.DoubleEchoAgent("agent1"),
+            new OrchestrationTestHelpers.DoubleEchoAgent("agent2"),
+            new OrchestrationTestHelpers.DoubleEchoAgent("agent3"))
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+        designations.Where(kvp => kvp.Value.Count == 0)
+            .Should().ContainSingle("OutputMessagesExecutor is the sole terminal output by default");
+        designations.Where(kvp => kvp.Value.Contains(OutputTag.Intermediate))
+            .Should().HaveCount(3, "every pipeline agent is designated intermediate by default");
+    }
+
+    [Fact]
+    public void Test_SequentialWorkflowBuilder_ExplicitDesignationsReplaceDefaults()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent a1 = new("agent1");
+        OrchestrationTestHelpers.DoubleEchoAgent a2 = new("agent2");
+        OrchestrationTestHelpers.DoubleEchoAgent a3 = new("agent3");
+
+        Workflow workflow = new SequentialWorkflowBuilder(a1, a2, a3)
+            .WithOutputFrom(a1)
+            .WithIntermediateOutputFrom([a2])
+            .Build();
+
+        Dictionary<string, HashSet<OutputTag>> designations = workflow.OutputExecutors;
+
+        designations.Should().HaveCount(2,
+            "only the two explicitly-designated agents land on the inner builder; the end default is suppressed");
+        designations.Values.Where(tags => tags.Count == 0)
+            .Should().ContainSingle("agent1 is the only terminal designation");
+        designations.Values.Where(tags => tags.Contains(OutputTag.Intermediate))
+            .Should().ContainSingle("agent2 is the only intermediate designation");
+    }
+
+    [Fact]
+    public void Test_SequentialWorkflowBuilder_DesignationForNonParticipantThrows()
+    {
+        OrchestrationTestHelpers.DoubleEchoAgent participant = new("p1");
+        OrchestrationTestHelpers.DoubleEchoAgent stranger = new("stranger");
+
+        SequentialWorkflowBuilder builder = new SequentialWorkflowBuilder(participant)
+            .WithIntermediateOutputFrom([stranger]);
+
+        Action build = () => builder.Build();
+        build.Should().Throw<InvalidOperationException>().WithMessage("*stranger*");
+    }
+
+    [Fact]
+    public void Test_SequentialWorkflowBuilder_WithNamePropagatesToWorkflow()
+    {
+        Workflow workflow = new SequentialWorkflowBuilder(new OrchestrationTestHelpers.DoubleEchoAgent("agent1"))
+            .WithName("named-sequential")
+            .Build();
+
+        workflow.Name.Should().Be("named-sequential");
+    }
+
+    [Fact]
+    public void Test_SequentialWorkflowBuilder_WithDescriptionPropagatesToWorkflow()
+    {
+        Workflow workflow = new SequentialWorkflowBuilder(new OrchestrationTestHelpers.DoubleEchoAgent("agent1"))
+            .WithDescription("describes the sequential pipeline")
+            .Build();
+
+        workflow.Description.Should().Be("describes the sequential pipeline");
+    }
+
+    [Collection(FuturesSerialCollection.Name)]
+    public class AsAgentForwarding
+    {
+        [Fact]
+        public async Task Test_SequentialWorkflowBuilder_AsAgent_OnlyTerminalDesignationSurfacesAsync()
+        {
+            using FuturesScope _ = new(enabled: true);
+
+            OrchestrationTestHelpers.DoubleEchoAgent agent1 = new("agent1");
+            OrchestrationTestHelpers.DoubleEchoAgent agent2 = new("agent2");
+            OrchestrationTestHelpers.DoubleEchoAgent agent3 = new("agent3");
+
+            // Explicitly designate ONLY the last agent — defaults (which would tag every agent
+            // intermediate) are suppressed, so under Futures-on, agent1/agent2 produce no
+            // AgentResponse(Update)Events and nothing of theirs reaches the AsAgent stream.
+            Workflow workflow = new SequentialWorkflowBuilder(agent1, agent2, agent3)
+                .WithOutputFrom(agent3)
+                .Build();
+
+            List<AgentResponseUpdate> updates = await workflow
+                .AsAIAgent("WorkflowAgent")
+                .RunStreamingAsync(new ChatMessage(ChatRole.User, "abc"))
+                .ToListAsync();
+
+            // Filter by AuthorName — distinguishes which agent originated each update
+            // (text-content checks are unreliable because agent3 echoes earlier agents' markers
+            // as part of the cumulative pipeline payload).
+            HashSet<string> authoredBy = updates
+                .Select(u => u.AuthorName)
+                .Where(n => !string.IsNullOrEmpty(n))
+                .Select(n => n!)
+                .ToHashSet();
+
+            authoredBy.Should().Contain("agent3", "the terminal agent must surface");
+            authoredBy.Should().NotContain("agent1",
+                "the intermediate agent must not surface when only the terminal is designated");
+            authoredBy.Should().NotContain("agent2",
+                "the intermediate agent must not surface when only the terminal is designated");
+        }
+    }
+}

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/WorkflowBuilderTests.cs

@@ -6,7 +6,7 @@ using FluentAssertions;
 
 namespace Microsoft.Agents.AI.Workflows.UnitTests;
 
-public partial class WorkflowBuilderSmokeTests
+public partial class WorkflowBuilderTests
 {
     private sealed class NoOpExecutor(string id) : Executor(id)
     {
@@ -455,4 +455,112 @@ public partial class WorkflowBuilderSmokeTests
     /// </summary>
     private static Edge GetSingleEdge(Workflow workflow, string sourceId)
         => workflow.Edges[sourceId].Should().ContainSingle().Subject;
+
+    // --- Tag-aware WithOutputFrom / WithIntermediateOutputFrom tests ---
+
+    [Fact]
+    public void Test_WithOutputFrom_RegistersWithEmptyTagSet()
+    {
+        NoOpExecutor a = new("a");
+        NoOpExecutor b = new("b");
+        Workflow workflow = new WorkflowBuilder("a")
+            .AddEdge(a, b)
+            .WithOutputFrom(b)
+            .Build();
+
+        workflow.OutputExecutors.Should().ContainKey("b");
+        workflow.OutputExecutors["b"].Should().BeEmpty("regular outputs are untagged");
+    }
+
+    [Fact]
+    public void Test_WithIntermediateOutputFrom_AddsIntermediateTag()
+    {
+        NoOpExecutor a = new("a");
+        NoOpExecutor b = new("b");
+        Workflow workflow = new WorkflowBuilder("a")
+            .AddEdge(a, b)
+            .WithIntermediateOutputFrom([b])
+            .Build();
+
+        workflow.OutputExecutors["b"].Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+    }
+
+    [Fact]
+    public void Test_WithOutputFrom_MultipleExecutorsAllUntagged()
+    {
+        NoOpExecutor a = new("a");
+        NoOpExecutor b = new("b");
+        NoOpExecutor c = new("c");
+
+        Workflow workflow = new WorkflowBuilder("a")
+            .AddEdge(a, b).AddEdge(a, c)
+            .WithOutputFrom(b, c)
+            .Build();
+
+        workflow.OutputExecutors.Should().HaveCount(2);
+        workflow.OutputExecutors["b"].Should().BeEmpty();
+        workflow.OutputExecutors["c"].Should().BeEmpty();
+    }
+
+    [Fact]
+    public void Test_WithOutputFrom_ThenIntermediate_AccumulatesTags()
+    {
+        NoOpExecutor a = new("a");
+        NoOpExecutor b = new("b");
+        Workflow workflow = new WorkflowBuilder("a")
+            .AddEdge(a, b)
+            .WithOutputFrom(b)
+            .WithIntermediateOutputFrom([b])
+            .Build();
+
+        // WithOutputFrom doesn't add a tag; WithIntermediateOutputFrom adds Intermediate.
+        workflow.OutputExecutors["b"].Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+    }
+
+    [Fact]
+    public void Test_WithIntermediateOutputFrom_RepeatedDedupes()
+    {
+        NoOpExecutor a = new("a");
+        NoOpExecutor b = new("b");
+        Workflow workflow = new WorkflowBuilder("a")
+            .AddEdge(a, b)
+            .WithIntermediateOutputFrom([b])
+            .WithIntermediateOutputFrom([b])
+            .Build();
+
+        workflow.OutputExecutors["b"].Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+    }
+
+    [Fact]
+    public void Test_WithIntermediateOutputFrom_OnlyRegistersWithoutPriorWithOutputFrom()
+    {
+        // WithIntermediateOutputFrom on its own is sufficient to register the executor as an
+        // output source — the call ensures the id is in the dict with the Intermediate tag.
+        NoOpExecutor a = new("a");
+        NoOpExecutor b = new("b");
+        Workflow workflow = new WorkflowBuilder("a")
+            .AddEdge(a, b)
+            .WithIntermediateOutputFrom([b])
+            .Build();
+
+        workflow.OutputExecutors.Should().ContainKey("b");
+        workflow.OutputExecutors["b"].Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+    }
+
+    [Fact]
+    public void Test_WithOutputFrom_TracksExecutorBinding()
+    {
+        // A placeholder binding referenced via WithOutputFrom must end up bound by the time we Build.
+        NoOpExecutor a = new("a");
+        NoOpExecutor future = new("future");
+
+        Workflow workflow = new WorkflowBuilder("a")
+            .AddEdge(a, "future")
+            .WithIntermediateOutputFrom(["future"])
+            .BindExecutor(future)
+            .Build();
+
+        workflow.OutputExecutors.Should().ContainKey("future");
+        workflow.OutputExecutors["future"].Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+    }
 }

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/WorkflowHostSmokeTests.cs

@@ -824,4 +824,130 @@ public class WorkflowHostSmokeTests : AIAgentHostingExecutorTestsBase
         Workflow handoffWorkflow = new HandoffWorkflowBuilder(agent).Build();
         return this.Run_AsAgent_OutgoingMessagesInHistoryAsync(handoffWorkflow, runAsync);
     }
+
+    // ----- Phase 5: Workflow-as-Agent intermediate forwarding -----------------
+
+    [Collection(Futures.FuturesSerialCollection.Name)]
+    public class IntermediateForwarding
+    {
+        private const string InterText = "progress";
+        private const string FinalText = "final";
+
+        private static async Task<List<AgentResponseUpdate>> RunStreamingAsync(
+            Workflow workflow,
+            bool includeWorkflowOutputsInResponse = false)
+        {
+            return await workflow
+                .AsAIAgent("WorkflowAgent", includeWorkflowOutputsInResponse: includeWorkflowOutputsInResponse)
+                .RunStreamingAsync(new ChatMessage(ChatRole.User, "hi"))
+                .ToListAsync();
+        }
+
+        [Fact]
+        public async Task Test_WorkflowHostAgent_IntermediateAgentResponseForwardedInStreamingAsync()
+        {
+            using Futures.FuturesScope _ = new(enabled: true);
+            TestReplayAgent agent = new(TestReplayAgent.ToChatMessages(InterText));
+            ExecutorBinding binding = agent.BindAsExecutor(new AIAgentHostOptions { EmitAgentResponseEvents = true });
+            Workflow workflow = new WorkflowBuilder(binding)
+                .WithIntermediateOutputFrom([binding])
+                .Build();
+
+            // Under Futures-on, AgentResponseEvent mirrors AgentResponseUpdateEvent: always
+            // forwarded regardless of the include flag. The intermediate tag is observable on
+            // the surfaced event for consumers that care to distinguish.
+            List<AgentResponseUpdate> updates = await RunStreamingAsync(workflow, includeWorkflowOutputsInResponse: false);
+
+            updates.Any(u => u.RawRepresentation is AgentResponseEvent are && are.IsIntermediate() && u.Text == InterText)
+                .Should().BeTrue("AgentResponseEvent is forwarded under Futures-on regardless of the include flag");
+        }
+
+        [Fact]
+        public async Task Test_WorkflowHostAgent_TerminalAgentResponseForwardedUnconditionallyWhenFuturesOnAsync()
+        {
+            using Futures.FuturesScope _ = new(enabled: true);
+            TestReplayAgent agent = new(TestReplayAgent.ToChatMessages(FinalText));
+            ExecutorBinding binding = agent.BindAsExecutor(new AIAgentHostOptions { EmitAgentResponseEvents = true });
+            Workflow workflow = new WorkflowBuilder(binding)
+                .WithOutputFrom(binding)
+                .Build();
+
+            // Even a terminal-only designation surfaces without the include flag — the gating
+            // asymmetry between AgentResponse and AgentResponseUpdate is gone under Futures-on.
+            List<AgentResponseUpdate> updates = await RunStreamingAsync(workflow, includeWorkflowOutputsInResponse: false);
+
+            updates.Any(u => u.RawRepresentation is AgentResponseEvent && u.Text == FinalText)
+                .Should().BeTrue("terminal AgentResponseEvent is forwarded under Futures-on regardless of the include flag");
+        }
+
+        [Fact]
+        public async Task Test_WorkflowHostAgent_TerminalAgentResponseGatedWhenFuturesOffAsync()
+        {
+            using Futures.FuturesScope _ = new(enabled: false);
+
+            static Workflow Build()
+            {
+                TestReplayAgent agent = new(TestReplayAgent.ToChatMessages(FinalText));
+                ExecutorBinding binding = agent.BindAsExecutor(new AIAgentHostOptions { EmitAgentResponseEvents = true });
+                return new WorkflowBuilder(binding).WithOutputFrom(binding).Build();
+            }
+
+            // Legacy semantics: AgentResponseEvent stays behind the include flag when Futures
+            // is off. Two fresh workflows because in-process runs aren't reentrant.
+            List<AgentResponseUpdate> gated = await RunStreamingAsync(Build(), includeWorkflowOutputsInResponse: false);
+            gated.Any(u => u.RawRepresentation is AgentResponseEvent && u.Text == FinalText)
+                .Should().BeFalse("terminal AgentResponseEvent stays gated under Futures-off");
+
+            List<AgentResponseUpdate> included = await RunStreamingAsync(Build(), includeWorkflowOutputsInResponse: true);
+            included.Any(u => u.RawRepresentation is AgentResponseEvent && u.Text == FinalText)
+                .Should().BeTrue("opting in via includeWorkflowOutputsInResponse surfaces it");
+        }
+
+        [Fact]
+        public async Task Test_WorkflowHostAgent_UndesignatedExecutorEmitsNoAgentResponseEventWhenFuturesOnAsync()
+        {
+            using Futures.FuturesScope _ = new(enabled: true);
+            TestReplayAgent agent = new(TestReplayAgent.ToChatMessages(InterText));
+            ExecutorBinding binding = agent.BindAsExecutor(new AIAgentHostOptions { EmitAgentResponseEvents = true });
+            // No designation — under Futures-on, the AgentResponse is dropped by the filter.
+            Workflow workflow = new WorkflowBuilder(binding).Build();
+
+            List<AgentResponseUpdate> updates = await RunStreamingAsync(workflow, includeWorkflowOutputsInResponse: true);
+
+            updates.Any(u => u.RawRepresentation is AgentResponseEvent)
+                .Should().BeFalse("an undesignated AIAgent executor produces no AgentResponseEvent under Futures-on");
+        }
+
+        [Fact]
+        public async Task Test_WorkflowHostAgent_UndesignatedAgentResponseSurfacesWhenFuturesOffAsync()
+        {
+            using Futures.FuturesScope _ = new(enabled: false);
+            TestReplayAgent agent = new(TestReplayAgent.ToChatMessages(InterText));
+            ExecutorBinding binding = agent.BindAsExecutor(new AIAgentHostOptions { EmitAgentResponseEvents = true });
+            Workflow workflow = new WorkflowBuilder(binding).Build();
+
+            List<AgentResponseUpdate> updates = await RunStreamingAsync(workflow, includeWorkflowOutputsInResponse: true);
+
+            updates.Any(u => u.RawRepresentation is AgentResponseEvent && u.Text == InterText)
+                .Should().BeTrue("legacy bypass still emits AgentResponseEvent regardless of designation");
+        }
+
+        [Fact]
+        public async Task Test_WorkflowHostAgent_IntermediateTagAvailableViaRawRepresentationAsync()
+        {
+            using Futures.FuturesScope _ = new(enabled: true);
+            TestReplayAgent agent = new(TestReplayAgent.ToChatMessages(InterText));
+            ExecutorBinding binding = agent.BindAsExecutor(new AIAgentHostOptions { EmitAgentResponseEvents = true });
+            Workflow workflow = new WorkflowBuilder(binding)
+                .WithIntermediateOutputFrom([binding])
+                .Build();
+
+            List<AgentResponseUpdate> updates = await RunStreamingAsync(workflow);
+
+            AgentResponseUpdate progress = updates.First(u => u.RawRepresentation is AgentResponseEvent && u.Text == InterText);
+            AgentResponseEvent raw = (AgentResponseEvent)progress.RawRepresentation!;
+            raw.IsIntermediate().Should().BeTrue();
+            raw.Tags.Should().BeEquivalentTo(new[] { OutputTag.Intermediate });
+        }
+    }
 }

python/.env.example

@@ -44,6 +44,9 @@ GEMINI_MODEL=""
 # Ollama
 OLLAMA_ENDPOINT=""
 OLLAMA_MODEL=""
+# Mistral AI
+MISTRAL_API_KEY=""
+MISTRAL_EMBEDDING_MODEL=""
 # Observability (instrumentation is enabled by default; set "ENABLE_INSTRUMENTATION" to "false" to opt out)
 ENABLE_SENSITIVE_DATA=true
 OTEL_EXPORTER_OTLP_ENDPOINT="http://localhost:4317/"

python/PACKAGE_STATUS.md

@@ -27,7 +27,7 @@ Status is grouped into these buckets:
 | `agent-framework-claude` | `python/packages/claude` | `beta` |
 | `agent-framework-copilotstudio` | `python/packages/copilotstudio` | `beta` |
 | `agent-framework-core` | `python/packages/core` | `released` |
-| `agent-framework-declarative` | `python/packages/declarative` | `beta` |
+| `agent-framework-declarative` | `python/packages/declarative` | `rc` |
 | `agent-framework-devui` | `python/packages/devui` | `beta` |
 | `agent-framework-durabletask` | `python/packages/durabletask` | `beta` |
 | `agent-framework-foundry` | `python/packages/foundry` | `released` |
@@ -37,6 +37,7 @@ Status is grouped into these buckets:
 | `agent-framework-hyperlight` | `python/packages/hyperlight` | `beta` |
 | `agent-framework-lab` | `python/packages/lab` | `beta` |
 | `agent-framework-mem0` | `python/packages/mem0` | `beta` |
+| `agent-framework-mistral` | `python/packages/mistral` | `alpha` |
 | `agent-framework-monty` | `python/packages/monty` | `alpha` |
 | `agent-framework-ollama` | `python/packages/ollama` | `beta` |
 | `agent-framework-openai` | `python/packages/openai` | `released` |
@@ -57,6 +58,13 @@ listed below.
 
 ### Experimental features
 
+#### `DECLARATIVE_AGENTS`
+
+- `agent-framework-declarative`: declarative agent loading APIs from
+  `agent_framework_declarative`, including `AgentFactory`,
+  `DeclarativeLoaderError`, `ProviderLookupError`, and `ProviderTypeMapping`
+  from `agent_framework_declarative/_loader.py`
+
 #### `EVALS`
 
 - `agent-framework-core`: exported evaluation APIs from `agent_framework`, including

python/packages/a2a/agent_framework_a2a/_a2a_executor.py

@@ -2,6 +2,7 @@
 
 import base64
 import logging
+import uuid
 from asyncio import CancelledError
 from collections.abc import Mapping
 from functools import partial
@@ -181,9 +182,18 @@ class A2AExecutor(AgentExecutor):
         """Run the agent in streaming mode and publish updates to the task updater."""
         response_stream = self._agent.run(query, session=session, stream=True, **self._run_kwargs)
         streamed_artifact_ids: set[str] = set()
+        # Generate a stable artifact ID for the entire stream so all chunks share the same ID.
+        # This ensures clients can coalesce streaming tokens into a single artifact/message
+        # per the A2A spec (TaskArtifactUpdateEvent with append=True on same artifactId).
+        default_artifact_id = str(uuid.uuid4())
         await (
             response_stream.with_transform_hook(
-                partial(self.handle_events, updater=updater, streamed_artifact_ids=streamed_artifact_ids)
+                partial(
+                    self.handle_events,
+                    updater=updater,
+                    streamed_artifact_ids=streamed_artifact_ids,
+                    default_artifact_id=default_artifact_id,
+                )
             )
         ).get_final_response()
 
@@ -199,7 +209,11 @@ class A2AExecutor(AgentExecutor):
             await self.handle_events(message, updater)
 
     async def handle_events(
-        self, item: Message | AgentResponseUpdate, updater: TaskUpdater, streamed_artifact_ids: set[str] | None = None
+        self,
+        item: Message | AgentResponseUpdate,
+        updater: TaskUpdater,
+        streamed_artifact_ids: set[str] | None = None,
+        default_artifact_id: str | None = None,
     ) -> None:
         """Convert agent response items (Messages or Updates) to A2A protocol events.
 
@@ -213,7 +227,10 @@ class A2AExecutor(AgentExecutor):
             item: The agent response item (Message or AgentResponseUpdate) to process.
             updater: The task updater to publish events to.
             streamed_artifact_ids: A set of artifact IDs that have already been streamed.
-                Used to prevent duplicate updates for the same artifact.
+                Used to track which artifacts need append=True on subsequent chunks.
+            default_artifact_id: A stable artifact ID to use when the item does not provide one.
+                This ensures all streaming chunks for a single response share the same artifact ID,
+                allowing clients to coalesce them into a single message.
 
         Example:
             .. code-block:: python
@@ -224,6 +241,7 @@ class A2AExecutor(AgentExecutor):
                         item: Message | AgentResponseUpdate,
                         updater: TaskUpdater,
                         streamed_artifact_ids: set[str] | None = None,
+                        default_artifact_id: str | None = None,
                     ) -> None:
                         # Custom logic to transform item contents
                         if item.role == "assistant" and item.contents:
@@ -260,19 +278,20 @@ class A2AExecutor(AgentExecutor):
 
         if parts:
             if isinstance(item, AgentResponseUpdate):
+                # Resolve artifact ID: use item's message_id if available, otherwise fall back
+                # to the stable default_artifact_id so all streaming chunks share the same ID.
+                artifact_id = item.message_id or default_artifact_id
                 # For streaming updates, we send TaskArtifactUpdateEvent via add_artifact
                 await updater.add_artifact(
                     parts=parts,
-                    artifact_id=item.message_id,
+                    artifact_id=artifact_id,
                     metadata=metadata,
                     append=(
-                        True
-                        if streamed_artifact_ids is not None and item.message_id in (streamed_artifact_ids or set())
-                        else None
+                        True if streamed_artifact_ids is not None and artifact_id in streamed_artifact_ids else None
                     ),
                 )
-                if item.message_id and streamed_artifact_ids is not None:
-                    streamed_artifact_ids.add(item.message_id)
+                if artifact_id and streamed_artifact_ids is not None:
+                    streamed_artifact_ids.add(artifact_id)
             else:
                 # For final messages, we send TaskStatusUpdateEvent with 'working' state
                 await updater.update_status(

python/packages/a2a/agent_framework_a2a/_agent.py

@@ -176,6 +176,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
         http_client: httpx.AsyncClient | None = None,
         auth_interceptor: AuthInterceptor | None = None,
         timeout: float | httpx.Timeout | None = None,
+        supported_protocol_bindings: list[Literal["JSONRPC", "GRPC", "HTTP+JSON"] | str] | None = None,
         **kwargs: Any,
     ) -> None:
         """Initialize the A2AAgent.
@@ -193,6 +194,9 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
             timeout: Request timeout configuration. Can be a float (applied to all timeout components),
                 httpx.Timeout object (for full control), or None (uses 10.0s connect, 60.0s read,
                 10.0s write, 5.0s pool - optimized for A2A operations).
+            supported_protocol_bindings: List of protocol bindings to use for transport negotiation.
+                Known values: "JSONRPC", "GRPC", "HTTP+JSON". Defaults to ["JSONRPC"].
+                The A2A spec treats this as an open-form string, so custom bindings are also accepted.
             kwargs: any additional properties, passed to BaseAgent.
         """
         # Default name/description from agent_card when not explicitly provided
@@ -205,6 +209,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
         super().__init__(id=id, name=name, description=description, **kwargs)
         self._http_client: httpx.AsyncClient | None = http_client
         self._timeout_config = self._create_timeout_config(timeout)
+        bindings = supported_protocol_bindings if supported_protocol_bindings is not None else ["JSONRPC"]
         if client is not None:
             self.client = client
             self._non_streaming_client: Client | None = None
@@ -214,7 +219,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
             if url is None:
                 raise ValueError("Either agent_card or url must be provided")
             # Create minimal agent card from URL
-            agent_card = minimal_agent_card(url, ["JSONRPC"])
+            agent_card = minimal_agent_card(url, bindings)
 
         # Create or use provided httpx client
         if http_client is None:
@@ -229,13 +234,13 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
         streaming_config = ClientConfig(
             httpx_client=http_client,
             streaming=True,
-            supported_protocol_bindings=["JSONRPC"],
+            supported_protocol_bindings=bindings,
         )
         # Create non-streaming client (single request/response for stream=False)
         non_streaming_config = ClientConfig(
             httpx_client=http_client,
             streaming=False,
-            supported_protocol_bindings=["JSONRPC"],
+            supported_protocol_bindings=bindings,
         )
         streaming_factory = ClientFactory(streaming_config)
         non_streaming_factory = ClientFactory(non_streaming_config)
@@ -256,7 +261,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
                     "Provide a 'url' argument or ensure 'agent_card.supported_interfaces' "
                     "contains at least one interface with a URL."
                 ) from transport_error
-            fallback_card = minimal_agent_card(fallback_url, ["JSONRPC"])
+            fallback_card = minimal_agent_card(fallback_url, bindings)
             try:
                 self.client = streaming_factory.create(fallback_card, interceptors=interceptors)  # type: ignore
                 self._non_streaming_client = non_streaming_factory.create(
@@ -487,6 +492,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
                     contents=contents,
                     role="assistant" if msg.role == A2ARole.ROLE_AGENT else "user",
                     response_id=msg.message_id or str(uuid.uuid4()),
+                    message_id=msg.message_id,
                     additional_properties={"a2a_metadata": metadata} if metadata else None,
                     raw_representation=msg,
                 )
@@ -727,6 +733,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
                 contents=contents,
                 role="assistant" if message.role == A2ARole.ROLE_AGENT else "user",
                 response_id=update_event.task_id,
+                message_id=message.message_id,
                 additional_properties={"a2a_metadata": merged_metadata} if merged_metadata else None,
                 raw_representation=update_event,
             )

python/packages/a2a/tests/test_a2a_agent.py

@@ -420,6 +420,7 @@ async def test_run_streaming_with_message_response(a2a_agent: A2AAgent, mock_a2a
     assert content.text == "Streaming response from agent!"
 
     assert updates[0].response_id == "msg-stream-123"
+    assert updates[0].message_id == "msg-stream-123"
     assert mock_a2a_client.call_count == 1
 
 
@@ -703,7 +704,94 @@ def test_a2a_agent_initialization_with_timeout_parameter() -> None:
         assert isinstance(timeout_arg, httpx.Timeout)
 
 
-# region Continuation Token Tests
+def test_a2a_agent_initialization_with_supported_protocol_bindings() -> None:
+    """Test A2AAgent initialization with custom supported_protocol_bindings."""
+    with (
+        patch("agent_framework_a2a._agent.httpx.AsyncClient") as mock_async_client,
+        patch("agent_framework_a2a._agent.ClientConfig") as mock_config,
+        patch("agent_framework_a2a._agent.ClientFactory") as mock_factory,
+    ):
+        mock_async_client.return_value = MagicMock()
+        mock_client_instance = MagicMock()
+        mock_factory.return_value.create.return_value = mock_client_instance
+
+        A2AAgent(
+            name="Test Agent",
+            url="https://test-agent.example.com",
+            supported_protocol_bindings=["GRPC", "JSONRPC"],
+        )
+
+        # Verify ClientConfig was called with our custom bindings for both streaming and non-streaming
+        assert mock_config.call_count == 2
+        for call in mock_config.call_args_list:
+            assert call.kwargs["supported_protocol_bindings"] == ["GRPC", "JSONRPC"]
+
+
+def test_a2a_agent_initialization_defaults_to_jsonrpc() -> None:
+    """Test A2AAgent defaults to JSONRPC when supported_protocol_bindings is not provided."""
+    with (
+        patch("agent_framework_a2a._agent.httpx.AsyncClient") as mock_async_client,
+        patch("agent_framework_a2a._agent.ClientConfig") as mock_config,
+        patch("agent_framework_a2a._agent.ClientFactory") as mock_factory,
+    ):
+        mock_async_client.return_value = MagicMock()
+        mock_client_instance = MagicMock()
+        mock_factory.return_value.create.return_value = mock_client_instance
+
+        A2AAgent(name="Test Agent", url="https://test-agent.example.com")
+
+        # Verify ClientConfig was called with default JSONRPC bindings
+        assert mock_config.call_count == 2
+        for call in mock_config.call_args_list:
+            assert call.kwargs["supported_protocol_bindings"] == ["JSONRPC"]
+
+
+def test_a2a_agent_initialization_empty_list_preserved() -> None:
+    """Test that an explicit empty list is preserved and not replaced with defaults."""
+    with (
+        patch("agent_framework_a2a._agent.httpx.AsyncClient") as mock_async_client,
+        patch("agent_framework_a2a._agent.ClientConfig") as mock_config,
+        patch("agent_framework_a2a._agent.ClientFactory") as mock_factory,
+    ):
+        mock_async_client.return_value = MagicMock()
+        mock_client_instance = MagicMock()
+        mock_factory.return_value.create.return_value = mock_client_instance
+
+        A2AAgent(
+            name="Test Agent",
+            url="https://test-agent.example.com",
+            supported_protocol_bindings=[],
+        )
+
+        # Verify ClientConfig was called with the explicit empty list, not the default
+        assert mock_config.call_count == 2
+        for call in mock_config.call_args_list:
+            assert call.kwargs["supported_protocol_bindings"] == []
+
+
+def test_a2a_agent_fallback_uses_custom_bindings() -> None:
+    """Test that transport fallback path uses custom bindings."""
+    mock_agent_card = MagicMock()
+    mock_agent_card.supported_interfaces = [MagicMock(url="https://fallback.example.com")]
+
+    mock_factory = MagicMock()
+    # First create() call fails (primary streaming), then fallback calls succeed
+    primary_error = Exception("no compatible transports found")
+    mock_factory.create.side_effect = [primary_error, MagicMock(), MagicMock()]
+
+    with (
+        patch("agent_framework_a2a._agent.ClientFactory", return_value=mock_factory),
+        patch("agent_framework_a2a._agent.minimal_agent_card") as mock_minimal_card,
+        patch("agent_framework_a2a._agent.httpx.AsyncClient"),
+    ):
+        A2AAgent(
+            name="test-agent",
+            agent_card=mock_agent_card,
+            supported_protocol_bindings=["GRPC", "HTTP+JSON"],
+        )
+
+        # Verify minimal_agent_card was called with the custom bindings
+        mock_minimal_card.assert_called_once_with("https://fallback.example.com", ["GRPC", "HTTP+JSON"])
 
 
 async def test_working_task_emits_continuation_token(a2a_agent: A2AAgent, mock_a2a_client: MockA2AClient) -> None:
@@ -1335,7 +1423,7 @@ async def test_streaming_status_update_event_yields_content(
         status=TaskStatus(
             state=TaskState.TASK_STATE_COMPLETED,
             message=A2AMessage(
-                message_id=str(uuid4()),
+                message_id="msg-status-done",
                 role=A2ARole.ROLE_AGENT,
                 parts=[Part(text="Done")],
             ),
@@ -1350,6 +1438,7 @@ async def test_streaming_status_update_event_yields_content(
     assert len(updates) == 1
     assert updates[0].text == "Done"
     assert updates[0].role == "assistant"
+    assert updates[0].message_id == "msg-status-done"
     assert updates[0].raw_representation == update_event
 
 
@@ -1362,7 +1451,7 @@ async def test_streaming_input_required_emits_content(a2a_agent: A2AAgent, mock_
         status=TaskStatus(
             state=TaskState.TASK_STATE_INPUT_REQUIRED,
             message=A2AMessage(
-                message_id=str(uuid4()),
+                message_id="msg-input-req",
                 role=A2ARole.ROLE_AGENT,
                 parts=[Part(text="What is your name?")],
             ),
@@ -1376,6 +1465,7 @@ async def test_streaming_input_required_emits_content(a2a_agent: A2AAgent, mock_
 
     assert len(updates) == 1
     assert updates[0].text == "What is your name?"
+    assert updates[0].message_id == "msg-input-req"
 
 
 @mark.asyncio

python/packages/azurefunctions/tests/integration_tests/conftest.py

@@ -365,6 +365,14 @@ def _start_function_app(sample_path: Path, port: int) -> subprocess.Popen[Any]:
     # use the task hub name to separate orchestration state.
     env["TASKHUB_NAME"] = f"test{uuid.uuid4().hex[:8]}"
 
+    # The Azure Functions Python worker's dependency isolation mechanism crashes
+    # on Python 3.13 with a SIGSEGV in the protobuf C extension (google._upb).
+    # Disabling isolation lets the worker load dependencies from the app's own
+    # environment, which avoids the crash.
+    # See: https://github.com/Azure/azure-functions-python-worker/issues/1797
+    if sys.version_info >= (3, 13):
+        env.setdefault("PYTHON_ISOLATE_WORKER_DEPENDENCIES", "0")
+
     # On Windows, use CREATE_NEW_PROCESS_GROUP to allow proper termination
     # shell=True only on Windows to handle PATH resolution
     if sys.platform == "win32":
@@ -375,8 +383,15 @@ def _start_function_app(sample_path: Path, port: int) -> subprocess.Popen[Any]:
             shell=True,
             env=env,
         )
-    # On Unix, don't use shell=True to avoid shell wrapper issues
-    return subprocess.Popen(["func", "start", "--port", str(port)], cwd=str(sample_path), env=env)
+    # On Unix, use start_new_session=True to isolate the process group from the
+    # pytest-xdist worker.  Without this, signals (e.g. from test-timeout) can
+    # propagate to the func host and vice-versa, potentially killing the worker.
+    return subprocess.Popen(
+        ["func", "start", "--port", str(port)],
+        cwd=str(sample_path),
+        env=env,
+        start_new_session=True,
+    )
 
 
 def _wait_for_function_app_ready(func_process: subprocess.Popen[Any], port: int, max_wait: int = 60) -> None:
@@ -533,18 +548,33 @@ def function_app_for_test(request: pytest.FixtureRequest) -> Iterator[dict[str,
     _load_and_validate_env(sample_path)
 
     max_attempts = 3
+    # The overall budget MUST be shorter than the pytest-timeout value
+    # (--timeout=120 by default) so that the fixture finishes cleanly instead
+    # of being killed by os._exit() which crashes the xdist worker.
+    overall_budget = 100  # seconds – leaves headroom below the 120 s test timeout
     last_error: Exception | None = None
     func_process: subprocess.Popen[Any] | None = None
     base_url = ""
     port = 0
+    overall_start = time.monotonic()
+    attempts_made = 0
 
     for _ in range(max_attempts):
+        remaining = overall_budget - (time.monotonic() - overall_start)
+        if remaining < 10:
+            # Not enough time for another attempt; bail out.
+            break
+
+        attempts_made += 1
         port = _find_available_port()
         base_url = _build_base_url(port)
         func_process = _start_function_app(sample_path, port)
 
         try:
-            _wait_for_function_app_ready(func_process, port)
+            # Cap each attempt's wait to the remaining budget minus a small
+            # buffer for cleanup.
+            per_attempt_wait = min(60, int(remaining) - 5)
+            _wait_for_function_app_ready(func_process, port, max_wait=max(per_attempt_wait, 10))
             last_error = None
             break
         except FunctionAppStartupError as exc:
@@ -553,7 +583,8 @@ def function_app_for_test(request: pytest.FixtureRequest) -> Iterator[dict[str,
             func_process = None
 
     if func_process is None:
-        error_message = f"Function app failed to start after {max_attempts} attempt(s)."
+        elapsed = int(time.monotonic() - overall_start)
+        error_message = f"Function app failed to start after {attempts_made} attempt(s) ({elapsed}s elapsed)."
         if last_error is not None:
             error_message += f" Last error: {last_error}"
         pytest.fail(error_message)

python/packages/core/AGENTS.md

@@ -76,6 +76,14 @@ agent_framework/
 - **`SkillScriptRunner`** - Protocol for file-based script execution. Any callable matching `(skill, script, args) -> Any` satisfies it. Code-defined scripts do not use a runner.
 - **`SkillsProvider`** - Context provider (extends `ContextProvider`) that discovers file-based skills from `SKILL.md` files and/or accepts code-defined `Skill` instances. Follows progressive disclosure: advertise → load → read resources / run scripts.
 
+### File Access Harness (`_harness/_file_access.py`)
+
+- **`AgentFileStore`** - Abstract async store backing the file-access harness. Implementations expose `write_file`, `read_file`, `delete_file`, `list_files`, `file_exists`, `search_files`, and `create_directory` over forward-slash relative paths.
+- **`InMemoryAgentFileStore`** - Dict-backed store suitable for tests and lightweight scenarios.
+- **`FileSystemAgentFileStore`** - Disk-backed store rooted under a configurable directory. Enforces relative-path normalization, root containment, and rejects symlink/reparse-point segments to prevent escape.
+- **`FileSearchResult`** / **`FileSearchMatch`** - `SerializationMixin` DTOs returned by `search_files`, carrying the matching file name, a context snippet, and the matching lines with 1-based line numbers.
+- **`FileAccessProvider`** - `ContextProvider` that adds shared file-access tools (`file_access_save_file`, `file_access_read_file`, `file_access_delete_file`, `file_access_list_files`, `file_access_search_files`) plus default usage instructions to each invocation. Unlike `MemoryContextProvider`, the store is intentionally shared across sessions and agents.
+
 ### Workflows (`_workflows/`)
 
 - **`Workflow`** - Graph-based workflow definition

python/packages/core/agent_framework/__init__.py

@@ -90,6 +90,16 @@ from ._harness._background_agents import (
     BackgroundTaskInfo,
     BackgroundTaskStatus,
 )
+from ._harness._file_access import (
+    DEFAULT_FILE_ACCESS_INSTRUCTIONS,
+    DEFAULT_FILE_ACCESS_SOURCE_ID,
+    AgentFileStore,
+    FileAccessProvider,
+    FileSearchMatch,
+    FileSearchResult,
+    FileSystemAgentFileStore,
+    InMemoryAgentFileStore,
+)
 from ._harness._memory import (
     DEFAULT_MEMORY_SOURCE_ID,
     MemoryContextProvider,
@@ -309,6 +319,8 @@ __all__ = [
     "APP_INFO",
     "COMPACTION_STATE_KEY",
     "DEFAULT_BACKGROUND_AGENTS_SOURCE_ID",
+    "DEFAULT_FILE_ACCESS_INSTRUCTIONS",
+    "DEFAULT_FILE_ACCESS_SOURCE_ID",
     "DEFAULT_HARNESS_INSTRUCTIONS",
     "DEFAULT_MAX_ITERATIONS",
     "DEFAULT_MEMORY_SOURCE_ID",
@@ -334,6 +346,7 @@ __all__ = [
     "AgentExecutor",
     "AgentExecutorRequest",
     "AgentExecutorResponse",
+    "AgentFileStore",
     "AgentFrameworkException",
     "AgentMiddleware",
     "AgentMiddlewareLayer",
@@ -393,11 +406,15 @@ __all__ = [
     "ExperimentalFeature",
     "FanInEdgeGroup",
     "FanOutEdgeGroup",
+    "FileAccessProvider",
     "FileCheckpointStorage",
     "FileHistoryProvider",
+    "FileSearchMatch",
+    "FileSearchResult",
     "FileSkill",
     "FileSkillScript",
     "FileSkillsSource",
+    "FileSystemAgentFileStore",
     "FilteringSkillsSource",
     "FinalT",
     "FinishReason",
@@ -414,6 +431,7 @@ __all__ = [
     "GeneratedEmbeddings",
     "GraphConnectivityError",
     "HistoryProvider",
+    "InMemoryAgentFileStore",
     "InMemoryCheckpointStorage",
     "InMemoryHistoryProvider",
     "InMemorySkillsSource",

python/packages/core/agent_framework/_feature_stage.py

@@ -50,6 +50,7 @@ class ExperimentalFeature(str, Enum):
     on enum membership or attribute presence over time.
     """
 
+    DECLARATIVE_AGENTS = "DECLARATIVE_AGENTS"
     EVALS = "EVALS"
     FILE_HISTORY = "FILE_HISTORY"
     FIDES = "FIDES"

python/packages/core/agent_framework/_harness/_agent.py

@@ -14,12 +14,13 @@ import logging
 from collections.abc import Callable, Sequence
 from typing import TYPE_CHECKING, Any
 
-from .._agents import Agent
+from .._agents import Agent, SupportsAgentRun
 from .._clients import SupportsWebSearchTool
 from .._compaction import CompactionProvider, ContextWindowCompactionStrategy, ToolResultCompactionStrategy
 from .._feature_stage import ExperimentalFeature, experimental
 from .._sessions import ContextProvider, HistoryProvider, InMemoryHistoryProvider
 from .._skills import SkillsProvider
+from ._background_agents import BackgroundAgentsProvider
 from ._memory import MemoryContextProvider, MemoryStore
 from ._mode import AgentModeProvider
 from ._todo import TodoProvider
@@ -103,6 +104,8 @@ def _assemble_context_providers(
     memory_store: MemoryStore | None,
     skills_provider: SkillsProvider | None,
     skills_paths: Sequence[str] | None,
+    background_agents: Sequence[SupportsAgentRun] | None,
+    background_agents_instructions: str | None,
     extra_context_providers: Sequence[ContextProvider] | None,
 ) -> list[ContextProvider]:
     """Assemble the ordered list of context providers."""
@@ -130,6 +133,10 @@ def _assemble_context_providers(
     if skills_paths:
         providers.append(SkillsProvider.from_paths(*skills_paths))
 
+    # Background agents are opt-in: only added when agents are provided.
+    if background_agents:
+        providers.append(BackgroundAgentsProvider(background_agents, instructions=background_agents_instructions))
+
     # Append any user-supplied additional providers.
     if extra_context_providers:
         providers.extend(extra_context_providers)
@@ -165,6 +172,8 @@ def create_harness_agent(
     memory_store: MemoryStore | None = None,
     skills_provider: SkillsProvider | None = None,
     skills_paths: Sequence[str] | None = None,
+    background_agents: Sequence[SupportsAgentRun] | None = None,
+    background_agents_instructions: str | None = None,
     disable_web_search: bool = False,
     otel_provider_name: str | None = None,
     context_providers: Sequence[ContextProvider] | None = None,
@@ -182,6 +191,7 @@ def create_harness_agent(
     - **AgentModeProvider** — plan/execute mode tracking
     - **MemoryContextProvider** — file-based durable memory (when ``memory_store`` provided)
     - **SkillsProvider** — skill discovery and progressive loading
+    - **BackgroundAgentsProvider** — delegate work to background sub-agents
     - **OpenTelemetry** — observability via ``AgentTelemetryLayer``
 
     Each feature can be disabled or customized via keyword arguments.
@@ -253,6 +263,13 @@ def create_harness_agent(
         skills_paths: Paths for file-based skill discovery (looks for SKILL.md files).
             Can be combined with ``skills_provider``. When neither ``skills_provider``
             nor ``skills_paths`` is provided, no SkillsProvider is added.
+        background_agents: Collection of agents available for background task delegation.
+            When provided, a ``BackgroundAgentsProvider`` is automatically included,
+            enabling the agent to start, monitor, and retrieve results from background tasks.
+            Each agent must have a non-empty, unique name (case-insensitive).
+        background_agents_instructions: Optional instruction override for the
+            ``BackgroundAgentsProvider``. May include ``{background_agents}`` placeholder
+            which will be replaced with the agent listing.
         disable_web_search: When True, skip automatic web search tool inclusion.
             When False (default), the web search tool is automatically added if the
             client implements SupportsWebSearchTool. A warning is logged if the client
@@ -302,6 +319,8 @@ def create_harness_agent(
         memory_store=memory_store,
         skills_provider=skills_provider,
         skills_paths=skills_paths,
+        background_agents=background_agents,
+        background_agents_instructions=background_agents_instructions,
         extra_context_providers=context_providers,
     )
 

python/packages/core/agent_framework/_mcp.py

@@ -10,7 +10,7 @@ import logging
 import re
 import sys
 from abc import abstractmethod
-from collections.abc import Callable, Collection, Coroutine, Sequence
+from collections.abc import Callable, Collection, Coroutine, Mapping, Sequence
 from contextlib import AsyncExitStack, _AsyncGeneratorContextManager  # type: ignore
 from datetime import timedelta
 from functools import partial
@@ -142,6 +142,13 @@ def _inject_otel_into_mcp_meta(meta: dict[str, Any] | None = None) -> dict[str,
     return meta
 
 
+def _url_origin(url: Any) -> tuple[str, str, int | None]:
+    port = url.port
+    if port is None:
+        port = 443 if url.scheme == "https" else 80 if url.scheme == "http" else None
+    return (url.scheme, url.host or "", port)
+
+
 def streamable_http_client(*args: Any, **kwargs: Any) -> _AsyncGeneratorContextManager[Any, None]:
     """Lazily import the MCP streamable HTTP transport."""
     try:
@@ -255,6 +262,7 @@ class MCPTool:
         self._exit_stack = AsyncExitStack()
         self._lifecycle_lock = asyncio.Lock()
         self._lifecycle_request_lock = asyncio.Lock()
+        self._function_load_lock = asyncio.Lock()
         self._lifecycle_queue: asyncio.Queue[tuple[str, bool, bool, asyncio.Future[None]]] | None = None
         self._lifecycle_owner_task: asyncio.Task[None] | None = None
         self.session = session
@@ -655,6 +663,11 @@ class MCPTool:
                 raise
         except asyncio.CancelledError:
             logger.warning("Could not cleanly close MCP exit stack because the lifecycle owner task was cancelled.")
+        except Exception as e:
+            if type(e).__name__ == "ExceptionGroup":
+                logger.warning("Could not cleanly close MCP exit stack due to cleanup error group. Error: %s", e)
+            else:
+                raise
 
     async def _close_and_check_cancelled(self, ex: BaseException) -> bool:
         """Close the exit stack and return True if *ex* is a genuine task cancellation.
@@ -1018,6 +1031,10 @@ class MCPTool:
         Raises:
             ToolExecutionException: If the MCP server is not connected.
         """
+        async with self._function_load_lock:
+            await self._load_prompts_locked()
+
+    async def _load_prompts_locked(self) -> None:
         from anyio import ClosedResourceError
         from mcp import types
 
@@ -1100,6 +1117,10 @@ class MCPTool:
         Raises:
             ToolExecutionException: If the MCP server is not connected.
         """
+        async with self._function_load_lock:
+            await self._load_tools_locked()
+
+    async def _load_tools_locked(self) -> None:
         from anyio import ClosedResourceError
         from mcp import types
 
@@ -1109,7 +1130,7 @@ class MCPTool:
 
         # Track existing function names to prevent duplicates
         existing_names = {func.name for func in self._functions}
-        self._tool_call_meta_by_name.clear()
+        tool_call_meta_by_name: dict[str, dict[str, Any]] = {}
 
         params: types.PaginatedRequestParams | None = None
         while True:
@@ -1145,7 +1166,7 @@ class MCPTool:
 
             for tool in tool_list.tools:
                 if tool.meta is not None:
-                    self._tool_call_meta_by_name[tool.name] = dict(tool.meta)
+                    tool_call_meta_by_name[tool.name] = dict(tool.meta)
 
                 normalized_name = _normalize_mcp_name(tool.name)
                 local_name = _build_prefixed_mcp_name(normalized_name, self.tool_name_prefix)
@@ -1194,6 +1215,8 @@ class MCPTool:
                 break
             params = types.PaginatedRequestParams(cursor=tool_list.nextCursor)
 
+        self._tool_call_meta_by_name = tool_call_meta_by_name
+
     async def _close_on_owner(self) -> None:
         # Cancel any pending reload tasks before tearing down the session.
         tasks = list(self._pending_reload_tasks)
@@ -1276,7 +1299,11 @@ class MCPTool:
             tool_name: The name of the tool to call.
 
         Keyword Args:
-            kwargs: Arguments to pass to the tool.
+            _meta: Optional ``dict[str, Any]`` of MCP request metadata. This reserved key is passed as the
+                ``meta`` parameter of the underlying ``session.call_tool`` call rather than as a tool argument.
+                User-supplied keys override metadata from ``tools/list``; OpenTelemetry propagation fills in
+                non-conflicting keys.
+            kwargs: Remaining arguments to pass to the tool.
 
         Returns:
             A list of Content items representing the tool output.  The default
@@ -1294,6 +1321,19 @@ class MCPTool:
             raise ToolExecutionException(
                 "Tools are not loaded for this server, please set load_tools=True in the constructor."
             )
+
+        raw_user_meta: object | None = kwargs.get("_meta")
+        user_meta: dict[str, Any] | None = None
+        if raw_user_meta is not None and not isinstance(raw_user_meta, dict):
+            raise ToolExecutionException("MCP tool metadata provided via _meta must be a dict.")
+        if isinstance(raw_user_meta, dict):
+            raw_user_meta_dict = cast(Mapping[object, object], raw_user_meta)
+            user_meta = {}
+            for key, value in raw_user_meta_dict.items():
+                if not isinstance(key, str):
+                    raise ToolExecutionException("MCP tool metadata provided via _meta must use string keys.")
+                user_meta[key] = value
+
         # Filter out framework kwargs that cannot be serialized by the MCP SDK.
         # These are internal objects passed through the function invocation pipeline
         # that should not be forwarded to external MCP servers.
@@ -1313,12 +1353,16 @@ class MCPTool:
                 "conversation_id",
                 "options",
                 "response_format",
+                "_meta",
             }
         }
 
         # Some MCP proxies require their tools/list metadata to be echoed on tools/call.
         tool_meta = self._tool_call_meta_by_name.get(tool_name)
-        meta = _inject_otel_into_mcp_meta(dict(tool_meta) if tool_meta is not None else None)
+        request_meta = dict(tool_meta) if tool_meta is not None else None
+        if user_meta is not None:
+            request_meta = {**(request_meta or {}), **user_meta}
+        meta = _inject_otel_into_mcp_meta(request_meta)
 
         parser = self.parse_tool_results or self._parse_tool_result_from_mcp
         # Try the operation, reconnecting once if the connection is closed
@@ -1336,28 +1380,33 @@ class MCPTool:
                 return parser(result)
             except ToolExecutionException:
                 raise
-            except ClosedResourceError as cl_ex:
+            except (ClosedResourceError, McpError) as call_ex:
+                is_session_terminated = (
+                    isinstance(call_ex, McpError) and "session terminated" in call_ex.error.message.lower()
+                )
+                is_connection_lost = isinstance(call_ex, ClosedResourceError) or is_session_terminated
+                if not is_connection_lost:
+                    error_message = call_ex.error.message if isinstance(call_ex, McpError) else str(call_ex)
+                    raise ToolExecutionException(error_message, inner_exception=call_ex) from call_ex
+
                 if attempt == 0:
-                    # First attempt failed, try reconnecting
-                    logger.info("MCP connection closed unexpectedly. Reconnecting...")
+                    # First attempt failed, try reconnecting.
+                    logger.info("MCP connection closed or terminated unexpectedly. Reconnecting...")
                     try:
                         await self.connect(reset=True)
-                        continue  # Retry the operation
+                        continue
                     except Exception as reconn_ex:
                         raise ToolExecutionException(
                             "Failed to reconnect to MCP server.",
                             inner_exception=reconn_ex,
                         ) from reconn_ex
-                else:
-                    # Second attempt also failed, give up
-                    logger.error(f"MCP connection closed unexpectedly after reconnection: {cl_ex}")
-                    raise ToolExecutionException(
-                        f"Failed to call tool '{tool_name}' - connection lost.",
-                        inner_exception=cl_ex,
-                    ) from cl_ex
-            except McpError as mcp_exc:
-                error_message = mcp_exc.error.message
-                raise ToolExecutionException(error_message, inner_exception=mcp_exc) from mcp_exc
+
+                # Second attempt also failed, give up.
+                logger.error("MCP connection closed unexpectedly after reconnection: %s", call_ex)
+                raise ToolExecutionException(
+                    f"Failed to call tool '{tool_name}' - connection lost.",
+                    inner_exception=call_ex,
+                ) from call_ex
             except Exception as ex:
                 raise ToolExecutionException(f"Failed to call tool '{tool_name}'.", inner_exception=ex) from ex
         raise ToolExecutionException(f"Failed to call tool '{tool_name}' after retries.")
@@ -1718,10 +1767,11 @@ class MCPStreamableHTTPTool(MCPTool):
         Returns:
             An async context manager for the streamable HTTP client transport.
         """
-        from httpx import AsyncClient, Request, Timeout
+        from httpx import URL, AsyncClient, Request, Timeout
 
         http_client = self._httpx_client
         if self._header_provider is not None:
+            target_origin = _url_origin(URL(self.url))
             if http_client is None:
                 http_client = AsyncClient(
                     follow_redirects=True,
@@ -1732,6 +1782,8 @@ class MCPStreamableHTTPTool(MCPTool):
             if not hasattr(self, "_inject_headers_hook"):
 
                 async def _inject_headers(request: Request) -> None:  # noqa: RUF029
+                    if _url_origin(request.url) != target_origin:
+                        return
                     headers = _mcp_call_headers.get({})
                     for key, value in headers.items():
                         request.headers[key] = value

python/packages/core/agent_framework/_middleware.py

@@ -36,11 +36,10 @@ if TYPE_CHECKING:
     from pydantic import BaseModel
 
     from ._agents import SupportsAgentRun
-    from ._clients import SupportsChatGetResponse
     from ._compaction import CompactionStrategy, TokenizerProtocol
     from ._sessions import AgentSession
     from ._tools import FunctionTool, ToolTypes
-    from ._types import ChatOptions, ChatResponse, ChatResponseUpdate
+    from ._types import ChatOptions
 
     ResponseModelBoundT = TypeVar("ResponseModelBoundT", bound=BaseModel)
 

python/packages/core/agent_framework/_skills.py

@@ -2134,9 +2134,7 @@ class SkillsProvider(ContextProvider):
             ),
             FunctionTool(
                 name="read_skill_resource",
-                description=(
-                    "Reads a resource associated with a skill, such as references, assets, or dynamic data."
-                ),
+                description=("Reads a resource associated with a skill, such as references, assets, or dynamic data."),
                 func=_read_resource,
                 input_model={
                     "type": "object",
@@ -2173,8 +2171,7 @@ class SkillsProvider(ContextProvider):
                                     "type": "object",
                                     "additionalProperties": True,
                                     "description": (
-                                        "Named arguments as key-value pairs "
-                                        '(e.g. {"length": 24, "uppercase": true}).'
+                                        'Named arguments as key-value pairs (e.g. {"length": 24, "uppercase": true}).'
                                     ),
                                 },
                                 {

python/packages/core/agent_framework/_types.py

@@ -1973,11 +1973,97 @@ def _coalesce_text_content(contents: list[Content], type_str: Literal["text", "t
     contents.extend(coalesced_contents)
 
 
+def _content_items_text(items: Any) -> str | None:
+    """Return concatenated text when a content item list only contains text."""
+    if not isinstance(items, list):
+        return None
+    text_parts: list[str] = []
+    content_items = cast(list[object], items)
+    for item in content_items:
+        if not isinstance(item, Content) or item.type != "text":
+            return None
+        text_parts.append(item.text or "")
+    return "".join(text_parts)
+
+
+def _merge_content_item_lists(existing: Any, incoming: Any) -> Any:
+    """Merge streamed nested content lists, replacing deltas with a later full value when present."""
+    if incoming is None:
+        return existing
+    if existing is None:
+        return deepcopy(incoming)
+
+    existing_text = _content_items_text(existing)
+    incoming_text = _content_items_text(incoming)
+    if existing_text is not None and incoming_text is not None:
+        if incoming_text.startswith(existing_text):
+            return deepcopy(incoming)
+        if existing_text.startswith(incoming_text):
+            return existing
+
+        existing_items = cast(list[Content], existing)
+        merged = deepcopy(existing_items[0])
+        merged.text = existing_text + incoming_text
+        return [merged]
+
+    if isinstance(existing, list) and isinstance(incoming, list):
+        existing_list = cast(list[object], existing)
+        incoming_list = cast(list[object], incoming)
+        return [*existing_list, *deepcopy(incoming_list)]
+    return deepcopy(incoming)
+
+
+def _merge_code_interpreter_content(existing: Content, incoming: Content) -> None:
+    """Merge two code interpreter content items for the same logical call."""
+    existing.inputs = _merge_content_item_lists(existing.inputs, incoming.inputs)
+    existing.outputs = _merge_content_item_lists(existing.outputs, incoming.outputs)
+    existing.annotations = _combine_annotations(existing.annotations, incoming.annotations)
+    existing.additional_properties = {**existing.additional_properties, **incoming.additional_properties}
+    existing.raw_representation = _combine_raw_representations(existing.raw_representation, incoming.raw_representation)
+
+
+def _code_interpreter_key(content: Content) -> tuple[str, str] | None:
+    """Return the aggregation key for code interpreter call/result content."""
+    if content.type not in {"code_interpreter_tool_call", "code_interpreter_tool_result"}:
+        return None
+    call_id = content.call_id or content.additional_properties.get("item_id")
+    if not isinstance(call_id, str) or not call_id:
+        return None
+    return content.type, call_id
+
+
+def _coalesce_code_interpreter_content(contents: list[Content]) -> None:
+    """Coalesce streaming code interpreter chunks by call id."""
+    if not contents:
+        return
+
+    coalesced_contents: list[Content] = []
+    seen: dict[tuple[str, str], Content] = {}
+    for content in contents:
+        key = _code_interpreter_key(content)
+        if key is None:
+            coalesced_contents.append(content)
+            continue
+
+        existing = seen.get(key)
+        if existing is None:
+            copied = deepcopy(content)
+            seen[key] = copied
+            coalesced_contents.append(copied)
+            continue
+
+        _merge_code_interpreter_content(existing, content)
+
+    contents.clear()
+    contents.extend(coalesced_contents)
+
+
 def _finalize_response(response: ChatResponse | AgentResponse) -> None:
     """Finalizes the response by performing any necessary post-processing."""
     for msg in response.messages:
         _coalesce_text_content(msg.contents, "text")
         _coalesce_text_content(msg.contents, "text_reasoning")
+        _coalesce_code_interpreter_content(msg.contents)
 
 
 # region ContinuationToken

python/packages/core/agent_framework/observability.py

@@ -1332,6 +1332,22 @@ class ChatTelemetryLayer(Generic[OptionsCoT]):
         self.duration_histogram = _get_duration_histogram()
         self.otel_provider_name = otel_provider_name or getattr(self, "OTEL_PROVIDER_NAME", "unknown")
 
+    @staticmethod
+    def _backfill_request_model(span: trace.Span, attributes: dict[str, Any]) -> None:
+        """Backfill REQUEST_MODEL and the span name from RESPONSE_MODEL when unknown.
+
+        Chat-completion spans use REQUEST_MODEL as part of the span name. If the
+        request model was not known at span creation time (e.g. the client could
+        not resolve it before sending the request), update both the attribute and
+        the span name to the actual model returned in the response. Mutates
+        ``attributes`` in place.
+        """
+        response_model = attributes.get(OtelAttr.RESPONSE_MODEL)
+        if response_model and attributes.get(OtelAttr.REQUEST_MODEL, "unknown") == "unknown":
+            attributes[OtelAttr.REQUEST_MODEL] = response_model
+            operation = attributes.get(OtelAttr.OPERATION, "operation")
+            span.update_name(f"{operation} {response_model}")
+
     @overload
     def get_response(
         self,
@@ -1480,6 +1496,7 @@ class ChatTelemetryLayer(Generic[OptionsCoT]):
                     response: ChatResponse[Any] = await result_stream.get_final_response()
                     duration = duration_state.get("duration")
                     response_attributes = _get_response_attributes(attributes, response)
+                    self._backfill_request_model(span, response_attributes)
                     _capture_response(
                         span=span,
                         attributes=response_attributes,
@@ -1549,6 +1566,7 @@ class ChatTelemetryLayer(Generic[OptionsCoT]):
                     raise
                 duration = perf_counter() - start_time_stamp
                 response_attributes = _get_response_attributes(attributes, response)
+                self._backfill_request_model(span, response_attributes)
                 _capture_response(
                     span=span,
                     attributes=response_attributes,

python/packages/core/tests/core/test_harness_agent.py

@@ -394,3 +394,94 @@ def test_create_harness_agent_logs_warning_when_no_web_search(caplog: pytest.Log
             max_output_tokens=16_384,
         )
     assert any("SupportsWebSearchTool" in msg for msg in caplog.messages)
+
+
+# --- Background Agents Tests ---
+
+
+class _FakeBackgroundAgent:
+    """Minimal agent stub satisfying SupportsAgentRun for background agents tests."""
+
+    def __init__(self, name: str, description: str | None = None):
+        self.id = f"agent-{name}"
+        self.name = name
+        self.description = description
+
+    def create_session(self, *, session_id: str | None = None) -> AgentSession:
+        return AgentSession(session_id=session_id)
+
+    def get_session(self, service_session_id: str, *, session_id: str | None = None) -> AgentSession:
+        return AgentSession(service_session_id=service_session_id, session_id=session_id)
+
+    async def run(self, messages: Any = None, *, stream: bool = False, session: Any = None, **kwargs: Any) -> Any:
+        from agent_framework import AgentResponse
+
+        return AgentResponse(messages=[], response_id="fake-bg-response")
+
+
+def test_create_harness_agent_no_background_agents_by_default() -> None:
+    """No BackgroundAgentsProvider should be included when background_agents is not provided."""
+    from agent_framework._harness._background_agents import BackgroundAgentsProvider
+
+    agent = create_harness_agent(
+        client=_FakeChatClient(),  # type: ignore[arg-type]
+        max_context_window_tokens=128_000,
+        max_output_tokens=16_384,
+        disable_web_search=True,
+    )
+    providers = agent.context_providers or []
+    assert not any(isinstance(p, BackgroundAgentsProvider) for p in providers)
+
+
+def test_create_harness_agent_adds_background_agents_provider() -> None:
+    """BackgroundAgentsProvider should be included when background_agents are provided."""
+    from agent_framework._harness._background_agents import BackgroundAgentsProvider
+
+    bg_agent = _FakeBackgroundAgent("WebSearcher", "Searches the web")
+    agent = create_harness_agent(
+        client=_FakeChatClient(),  # type: ignore[arg-type]
+        max_context_window_tokens=128_000,
+        max_output_tokens=16_384,
+        disable_web_search=True,
+        background_agents=[bg_agent],
+    )
+    providers = agent.context_providers or []
+    bg_providers = [p for p in providers if isinstance(p, BackgroundAgentsProvider)]
+    assert len(bg_providers) == 1
+
+
+def test_create_harness_agent_background_agents_custom_instructions() -> None:
+    """Custom instructions should be passed to BackgroundAgentsProvider."""
+    from agent_framework._harness._background_agents import BackgroundAgentsProvider
+
+    custom_instructions = "## Custom\n\nUse agents wisely.\n\n{background_agents}"
+    bg_agent = _FakeBackgroundAgent("Helper", "A helper agent")
+    agent = create_harness_agent(
+        client=_FakeChatClient(),  # type: ignore[arg-type]
+        max_context_window_tokens=128_000,
+        max_output_tokens=16_384,
+        disable_web_search=True,
+        background_agents=[bg_agent],
+        background_agents_instructions=custom_instructions,
+    )
+    providers = agent.context_providers or []
+    bg_providers = [p for p in providers if isinstance(p, BackgroundAgentsProvider)]
+    assert len(bg_providers) == 1
+    # Verify the custom instructions were used (placeholder replaced with agent list).
+    assert "Custom" in bg_providers[0]._instructions
+    assert "Helper" in bg_providers[0]._instructions
+
+
+def test_create_harness_agent_empty_background_agents_list() -> None:
+    """An empty background_agents list should NOT add a BackgroundAgentsProvider."""
+    from agent_framework._harness._background_agents import BackgroundAgentsProvider
+
+    agent = create_harness_agent(
+        client=_FakeChatClient(),  # type: ignore[arg-type]
+        max_context_window_tokens=128_000,
+        max_output_tokens=16_384,
+        disable_web_search=True,
+        background_agents=[],
+    )
+    providers = agent.context_providers or []
+    assert not any(isinstance(p, BackgroundAgentsProvider) for p in providers)

python/packages/core/tests/core/test_harness_file_access.py

@@ -0,0 +1,713 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+from __future__ import annotations
+
+import json
+import re
+import time
+from pathlib import Path
+
+import pytest
+
+from agent_framework import (
+    Agent,
+    AgentFileStore,
+    AgentSession,
+    ExperimentalFeature,
+    FileAccessProvider,
+    FileSearchMatch,
+    FileSearchResult,
+    FileSystemAgentFileStore,
+    InMemoryAgentFileStore,
+    Message,
+    SupportsChatGetResponse,
+)
+from agent_framework._harness import _file_access as _file_access_module
+from agent_framework._harness._file_access import (
+    DEFAULT_FILE_ACCESS_INSTRUCTIONS,
+    DEFAULT_FILE_ACCESS_SOURCE_ID,
+    _matches_glob,
+    _normalize_relative_path,
+    _run_search_with_timeout,
+)
+
+
+def _tool_by_name(tools: list[object], name: str) -> object:
+    """Return the tool with the requested name from a prepared tool list."""
+    for tool in tools:
+        if getattr(tool, "name", None) == name:
+            return tool
+    raise AssertionError(f"Tool {name!r} was not found.")
+
+
+def test_normalize_relative_path_collapses_and_validates() -> None:
+    """The path normalizer should accept relative forward/backslash paths and reject unsafe ones."""
+    assert _normalize_relative_path("foo/bar.txt") == "foo/bar.txt"
+    assert _normalize_relative_path("foo\\bar.txt") == "foo/bar.txt"
+    assert _normalize_relative_path("foo//bar.txt") == "foo/bar.txt"
+    assert _normalize_relative_path("  foo/bar.txt  ") == "foo/bar.txt"
+    assert _normalize_relative_path("", is_directory=True) == ""
+    assert _normalize_relative_path("   ", is_directory=True) == ""
+    assert _normalize_relative_path("sub/", is_directory=True) == "sub"
+    assert _normalize_relative_path("sub\\", is_directory=True) == "sub"
+
+    with pytest.raises(ValueError, match="must not be empty"):
+        _normalize_relative_path("")
+    with pytest.raises(ValueError, match="must not be empty"):
+        _normalize_relative_path("   ")
+    with pytest.raises(ValueError, match="must not end with a path separator"):
+        _normalize_relative_path("foo/")
+    with pytest.raises(ValueError, match="must not end with a path separator"):
+        _normalize_relative_path("foo\\")
+    with pytest.raises(ValueError, match="'..' segments"):
+        _normalize_relative_path("foo/../bar.txt")
+    with pytest.raises(ValueError, match="'..' segments"):
+        _normalize_relative_path("./bar.txt")
+    with pytest.raises(ValueError, match="must be relative"):
+        _normalize_relative_path("C:/abs/path")
+    with pytest.raises(ValueError, match="must be relative"):
+        _normalize_relative_path("\\rooted")
+    with pytest.raises(ValueError, match="must be relative"):
+        _normalize_relative_path("/foo/bar.txt")
+
+
+def test_matches_glob_is_case_insensitive_and_optional() -> None:
+    """The glob matcher should be case-insensitive and treat missing patterns as match-all."""
+    assert _matches_glob("notes.MD", "*.md")
+    assert _matches_glob("research_one.txt", "research*")
+    assert not _matches_glob("plan.txt", "*.md")
+    assert _matches_glob("anything", None)
+    assert _matches_glob("anything", "")
+    assert _matches_glob("anything", "   ")
+
+
+def test_file_search_match_round_trips() -> None:
+    """File search match values should serialize and validate cleanly."""
+    raw_match = {"line_number": 3, "line": "error: boom"}
+
+    match = FileSearchMatch.from_dict(raw_match)
+    assert match == FileSearchMatch(line_number=3, line="error: boom")
+    assert match.to_dict() == raw_match
+    assert "FileSearchMatch(" in repr(match)
+
+    with pytest.raises(ValueError, match="positive integer"):
+        FileSearchMatch(line_number=0, line="oops")
+    with pytest.raises(ValueError, match="must be an integer"):
+        FileSearchMatch.from_dict({"line_number": "1", "line": "oops"})
+    with pytest.raises(ValueError, match="must be a string"):
+        FileSearchMatch.from_dict({"line_number": 1, "line": 42})
+
+
+def test_file_search_result_round_trips() -> None:
+    """File search result values should serialize the matching-line list correctly."""
+    raw_result = {
+        "file_name": "notes.md",
+        "snippet": "hello error world",
+        "matching_lines": [{"line_number": 2, "line": "error one"}],
+    }
+
+    result = FileSearchResult.from_dict(raw_result)
+    assert result.file_name == "notes.md"
+    assert result.snippet == "hello error world"
+    assert result.matching_lines == [FileSearchMatch(line_number=2, line="error one")]
+    assert result.to_dict() == raw_result
+    assert json.loads(result.to_json()) == raw_result
+
+    with pytest.raises(ValueError, match="matching_lines must be a list"):
+        FileSearchResult.from_dict({"file_name": "x", "snippet": "", "matching_lines": {}})
+
+    with pytest.raises(ValueError, match="elements must be mappings"):
+        FileSearchResult.from_dict({"file_name": "x", "snippet": "", "matching_lines": ["not-a-dict"]})
+
+
+async def test_in_memory_store_round_trips_files() -> None:
+    """The in-memory store should support write/read/exists/delete/list operations."""
+    store = InMemoryAgentFileStore()
+
+    await store.write_file("a.txt", "alpha")
+    await store.write_file("sub/b.txt", "beta")
+
+    assert await store.file_exists("a.txt")
+    assert not await store.file_exists("missing.txt")
+    assert await store.read_file("a.txt") == "alpha"
+    assert await store.read_file("missing.txt") is None
+
+    assert sorted(await store.list_files()) == ["a.txt"]  # subdirs are not direct children
+    assert sorted(await store.list_files("sub")) == ["b.txt"]
+
+    assert await store.delete_file("a.txt") is True
+    assert await store.delete_file("a.txt") is False
+    assert sorted(await store.list_files()) == []
+
+
+async def test_in_memory_store_search_returns_matches_with_snippets() -> None:
+    """The in-memory store should search file content case-insensitively and respect glob filters."""
+    store = InMemoryAgentFileStore()
+    await store.write_file("a.md", "line one\nThis line has ERROR inside\nline three\r")
+    await store.write_file("b.md", "no match here")
+    await store.write_file("notes.txt", "ERROR but wrong extension")
+
+    results = await store.search_files("", "error", "*.md")
+    assert [result.file_name for result in results] == ["a.md"]
+    matching_lines = results[0].matching_lines
+    assert matching_lines == [FileSearchMatch(line_number=2, line="This line has ERROR inside")]
+    assert "ERROR" in results[0].snippet
+
+    # No glob -> searches every file.
+    results_all = await store.search_files("", "error")
+    assert {result.file_name for result in results_all} == {"a.md", "notes.txt"}
+
+
+async def test_in_memory_store_search_rejects_invalid_and_oversize_regex() -> None:
+    """``search_files`` should surface clean errors for bad regex input."""
+    store = InMemoryAgentFileStore()
+    await store.write_file("a.md", "hello")
+
+    with pytest.raises(re.error):
+        await store.search_files("", "[unclosed")
+
+    with pytest.raises(ValueError, match="too long"):
+        await store.search_files("", "a" * 257)
+
+
+async def test_in_memory_store_normalizes_paths() -> None:
+    """Path normalization should reject traversal in the in-memory store too."""
+    store = InMemoryAgentFileStore()
+    for bad in ("../escape.txt", "/abs/path.txt", "."):
+        with pytest.raises(ValueError):
+            await store.write_file(bad, "boom")
+
+
+async def test_filesystem_store_round_trips_files(tmp_path: Path) -> None:
+    """The filesystem store should round-trip files on disk and create parents on write."""
+    store = FileSystemAgentFileStore(tmp_path)
+
+    await store.write_file("nested/a.txt", "alpha")
+    assert (tmp_path / "nested" / "a.txt").read_text(encoding="utf-8") == "alpha"
+
+    assert await store.read_file("nested/a.txt") == "alpha"
+    assert await store.read_file("missing.txt") is None
+    assert await store.file_exists("nested/a.txt")
+    assert not await store.file_exists("missing.txt")
+    assert sorted(await store.list_files("nested")) == ["a.txt"]
+    assert sorted(await store.list_files()) == []  # root only contains the directory
+
+    assert await store.delete_file("nested/a.txt") is True
+    assert await store.delete_file("nested/a.txt") is False
+
+
+async def test_filesystem_store_rejects_traversal_and_rooted_paths(tmp_path: Path) -> None:
+    """The filesystem store should refuse paths that escape the configured root."""
+    store = FileSystemAgentFileStore(tmp_path)
+
+    for bad in ("../escape.txt", "/etc/passwd", "C:/Windows/System32/notepad.exe", ".", ".."):
+        with pytest.raises(ValueError):
+            await store.write_file(bad, "boom")
+
+
+async def test_filesystem_store_rejects_symlinks_into_root(tmp_path: Path) -> None:
+    """The filesystem store should refuse to read through a symlink target."""
+    target = tmp_path / "outside.txt"
+    target.write_text("outside", encoding="utf-8")
+    root = tmp_path / "root"
+    root.mkdir()
+    link = root / "link.txt"
+    try:
+        link.symlink_to(target)
+    except (OSError, NotImplementedError) as exc:
+        pytest.skip(f"Symbolic links are not supported in this environment: {exc!r}")
+
+    store = FileSystemAgentFileStore(root)
+    with pytest.raises(ValueError, match="symbolic link"):
+        await store.read_file("link.txt")
+    with pytest.raises(ValueError, match="symbolic link"):
+        await store.write_file("link.txt", "stomp")
+
+    # List operations should silently skip the symlink entry rather than raise.
+    assert await store.list_files() == []
+
+
+async def test_filesystem_store_rejects_in_root_symlinks(tmp_path: Path) -> None:
+    """Symlinks whose target lives under the root must still be rejected.
+
+    ``Path.resolve`` collapses the symlink, so a naive resolved-path check
+    would silently follow it. The symlink probe must operate on the
+    unresolved candidate for this case to fail closed.
+    """
+    root = tmp_path / "root"
+    root.mkdir()
+    real = root / "real.txt"
+    real.write_text("payload", encoding="utf-8")
+    link = root / "alias.txt"
+    try:
+        link.symlink_to(real)
+    except (OSError, NotImplementedError) as exc:
+        pytest.skip(f"Symbolic links are not supported in this environment: {exc!r}")
+
+    store = FileSystemAgentFileStore(root)
+    with pytest.raises(ValueError, match="symbolic link"):
+        await store.read_file("alias.txt")
+    # The non-symlinked sibling must still be readable.
+    assert await store.read_file("real.txt") == "payload"
+
+
+async def test_filesystem_store_search_matches_lines_and_filters_globs(tmp_path: Path) -> None:
+    """The filesystem store should search files on disk and apply glob filters by file name."""
+    store = FileSystemAgentFileStore(tmp_path)
+    await store.write_file("a.md", "hello\nERROR happens\nbye\r")
+    await store.write_file("b.txt", "ERROR happens too")
+    await store.write_file("c.md", "nothing here")
+
+    results = await store.search_files("", "error", "*.md")
+    assert [result.file_name for result in results] == ["a.md"]
+    assert results[0].matching_lines == [FileSearchMatch(line_number=2, line="ERROR happens")]
+    assert "ERROR" in results[0].snippet
+
+    results_all = await store.search_files("", "error")
+    assert {result.file_name for result in results_all} == {"a.md", "b.txt"}
+
+
+async def test_filesystem_store_search_skips_non_utf8_files(tmp_path: Path) -> None:
+    """The filesystem store should silently skip non-UTF-8 files instead of aborting the search."""
+    store = FileSystemAgentFileStore(tmp_path)
+    await store.write_file("notes.md", "ERROR happens here")
+    (tmp_path / "blob.bin").write_bytes(b"\x80\x81\x82\x83")
+
+    results = await store.search_files("", "error")
+    assert [result.file_name for result in results] == ["notes.md"]
+
+
+async def test_filesystem_store_create_directory(tmp_path: Path) -> None:
+    """The filesystem store should create directories under the configured root."""
+    store = FileSystemAgentFileStore(tmp_path)
+    await store.create_directory("nested/inner")
+    assert (tmp_path / "nested" / "inner").is_dir()
+
+
+async def test_filesystem_store_list_files_accepts_blank_directory(tmp_path: Path) -> None:
+    """Whitespace-only directory inputs should resolve to the root, matching the in-memory store."""
+    store = FileSystemAgentFileStore(tmp_path)
+    await store.write_file("a.txt", "alpha")
+    assert sorted(await store.list_files("")) == ["a.txt"]
+    assert sorted(await store.list_files("   ")) == ["a.txt"]
+
+
+def test_filesystem_store_requires_non_empty_root() -> None:
+    """The filesystem store constructor should refuse blank root paths."""
+    with pytest.raises(ValueError, match="must not be empty"):
+        FileSystemAgentFileStore("")
+    with pytest.raises(ValueError, match="must not be empty"):
+        FileSystemAgentFileStore("   ")
+
+
+async def test_file_access_provider_registers_tools_and_instructions(
+    chat_client_base: SupportsChatGetResponse,
+) -> None:
+    """``FileAccessProvider.before_run`` should add the canonical instructions and five tools."""
+    session = AgentSession(session_id="session-1")
+    store = InMemoryAgentFileStore()
+    provider = FileAccessProvider(store=store)
+    agent = Agent(client=chat_client_base, context_providers=[provider])
+
+    _, options = await agent._prepare_session_and_messages(  # type: ignore[reportPrivateUsage]
+        session=session,
+        input_messages=[Message(role="user", contents=["work with files"])],
+    )
+
+    tools = options["tools"]
+    assert isinstance(tools, list)
+    expected_names = {
+        "file_access_save_file",
+        "file_access_read_file",
+        "file_access_delete_file",
+        "file_access_list_files",
+        "file_access_search_files",
+    }
+    assert {getattr(tool, "name", None) for tool in tools} >= expected_names
+
+    instructions = options.get("instructions")
+    if isinstance(instructions, str):
+        assert DEFAULT_FILE_ACCESS_INSTRUCTIONS in instructions
+    else:
+        assert any(DEFAULT_FILE_ACCESS_INSTRUCTIONS in chunk for chunk in (instructions or []))
+
+
+async def test_file_access_provider_delete_approval_defaults_to_always_require(
+    chat_client_base: SupportsChatGetResponse,
+) -> None:
+    """By default ``file_access_delete_file`` should require host approval."""
+    session = AgentSession(session_id="session-1")
+    provider = FileAccessProvider(store=InMemoryAgentFileStore())
+    agent = Agent(client=chat_client_base, context_providers=[provider])
+
+    _, options = await agent._prepare_session_and_messages(  # type: ignore[reportPrivateUsage]
+        session=session,
+        input_messages=[Message(role="user", contents=["work with files"])],
+    )
+
+    tools = options["tools"]
+    assert isinstance(tools, list)
+    delete_file = _tool_by_name(tools, "file_access_delete_file")
+    assert delete_file.approval_mode == "always_require"
+    # The non-destructive tools should remain autonomous.
+    for name in (
+        "file_access_save_file",
+        "file_access_read_file",
+        "file_access_list_files",
+        "file_access_search_files",
+    ):
+        assert _tool_by_name(tools, name).approval_mode == "never_require"
+
+
+async def test_file_access_provider_delete_approval_opt_out(
+    chat_client_base: SupportsChatGetResponse,
+) -> None:
+    """``require_delete_approval=False`` should drop delete to ``never_require``."""
+    session = AgentSession(session_id="session-1")
+    provider = FileAccessProvider(store=InMemoryAgentFileStore(), require_delete_approval=False)
+    agent = Agent(client=chat_client_base, context_providers=[provider])
+
+    _, options = await agent._prepare_session_and_messages(  # type: ignore[reportPrivateUsage]
+        session=session,
+        input_messages=[Message(role="user", contents=["work with files"])],
+    )
+
+    delete_file = _tool_by_name(options["tools"], "file_access_delete_file")  # type: ignore[arg-type]
+    assert delete_file.approval_mode == "never_require"
+
+
+async def test_file_access_provider_tools_round_trip_files(
+    chat_client_base: SupportsChatGetResponse,
+) -> None:
+    """The provider's tools should drive save/read/list/search/delete flows on an ``InMemoryAgentFileStore``."""
+    session = AgentSession(session_id="session-1")
+    store = InMemoryAgentFileStore()
+    provider = FileAccessProvider(store=store)
+    agent = Agent(client=chat_client_base, context_providers=[provider])
+
+    _, options = await agent._prepare_session_and_messages(  # type: ignore[reportPrivateUsage]
+        session=session,
+        input_messages=[Message(role="user", contents=["work with files"])],
+    )
+    tools = options["tools"]
+    assert isinstance(tools, list)
+
+    save_file = _tool_by_name(tools, "file_access_save_file")
+    read_file = _tool_by_name(tools, "file_access_read_file")
+    delete_file = _tool_by_name(tools, "file_access_delete_file")
+    list_files = _tool_by_name(tools, "file_access_list_files")
+    search_files = _tool_by_name(tools, "file_access_search_files")
+
+    saved = await save_file.invoke(arguments={"file_name": "plan.md", "content": "step 1\nERROR step 2"})
+    assert "plan.md" in saved[0].text and "saved" in saved[0].text
+
+    # Default overwrite=False should refuse the second save.
+    refused = await save_file.invoke(arguments={"file_name": "plan.md", "content": "stomp"})
+    assert "already exists" in refused[0].text
+
+    # overwrite=True should succeed.
+    overwritten = await save_file.invoke(
+        arguments={"file_name": "plan.md", "content": "stomp\nERROR replaced", "overwrite": True}
+    )
+    assert "saved" in overwritten[0].text
+
+    read_back = await read_file.invoke(arguments={"file_name": "plan.md"})
+    assert read_back[0].text == "stomp\nERROR replaced"
+
+    listed = await list_files.invoke()
+    assert json.loads(listed[0].text) == ["plan.md"]
+
+    # The list tool should accept an optional directory argument so agents can
+    # enumerate nested folders (not only the root).
+    await save_file.invoke(arguments={"file_name": "reports/2024.md", "content": "annual"})
+    listed_nested = await list_files.invoke(arguments={"directory": "reports"})
+    assert json.loads(listed_nested[0].text) == ["2024.md"]
+    # Blank / whitespace directory should fall back to the root listing.
+    listed_blank = await list_files.invoke(arguments={"directory": "   "})
+    assert sorted(json.loads(listed_blank[0].text)) == ["plan.md"]
+
+    missing = await read_file.invoke(arguments={"file_name": "missing.md"})
+    assert "not found" in missing[0].text
+
+    search_payload = await search_files.invoke(arguments={"regex_pattern": "error", "file_pattern": "*.md"})
+    parsed = json.loads(search_payload[0].text)
+    assert parsed[0]["file_name"] == "plan.md"
+    assert parsed[0]["matching_lines"][0]["line"] == "ERROR replaced"
+
+    # The search tool should likewise accept an optional directory argument so
+    # agents can scope a search to a subfolder.
+    await save_file.invoke(arguments={"file_name": "reports/issues.md", "content": "ERROR nested"})
+    scoped = await search_files.invoke(
+        arguments={"regex_pattern": "error", "file_pattern": "*.md", "directory": "reports"}
+    )
+    scoped_parsed = json.loads(scoped[0].text)
+    assert [entry["file_name"] for entry in scoped_parsed] == ["issues.md"]
+
+    deleted = await delete_file.invoke(arguments={"file_name": "plan.md"})
+    assert "deleted" in deleted[0].text
+
+    missing_delete = await delete_file.invoke(arguments={"file_name": "plan.md"})
+    assert "not found" in missing_delete[0].text
+
+
+async def test_file_access_provider_accepts_custom_instructions() -> None:
+    """Custom instructions should override the default banner."""
+    store = InMemoryAgentFileStore()
+    provider = FileAccessProvider(store=store, instructions="custom-banner")
+    assert provider.instructions == "custom-banner"
+    assert provider.source_id == DEFAULT_FILE_ACCESS_SOURCE_ID
+
+
+async def test_in_memory_store_write_file_raises_when_exists_and_no_overwrite() -> None:
+    """The atomic exclusive-create path should raise ``FileExistsError`` under the lock."""
+    store = InMemoryAgentFileStore()
+    await store.write_file("plan.md", "v1")
+
+    with pytest.raises(FileExistsError):
+        await store.write_file("plan.md", "v2", overwrite=False)
+
+    # The original content is preserved.
+    assert await store.read_file("plan.md") == "v1"
+
+    # Default ``overwrite=True`` still replaces.
+    await store.write_file("plan.md", "v3")
+    assert await store.read_file("plan.md") == "v3"
+
+
+async def test_filesystem_store_write_file_raises_when_exists_and_no_overwrite(tmp_path: Path) -> None:
+    """The filesystem store should use exclusive-create semantics when ``overwrite=False``."""
+    store = FileSystemAgentFileStore(tmp_path)
+    await store.write_file("plan.md", "v1")
+
+    with pytest.raises(FileExistsError):
+        await store.write_file("plan.md", "v2", overwrite=False)
+
+    assert (tmp_path / "plan.md").read_text(encoding="utf-8") == "v1"
+
+    await store.write_file("plan.md", "v3", overwrite=True)
+    assert (tmp_path / "plan.md").read_text(encoding="utf-8") == "v3"
+
+
+async def test_run_search_with_timeout_raises_value_error(monkeypatch: pytest.MonkeyPatch) -> None:
+    """A scan that exceeds the timeout should surface a clean ``ValueError``."""
+    monkeypatch.setattr(_file_access_module, "_SEARCH_TIMEOUT_SECONDS", 0.01)
+
+    def slow() -> list[FileSearchResult]:
+        time.sleep(0.5)
+        return []
+
+    with pytest.raises(ValueError, match="did not complete"):
+        await _run_search_with_timeout(slow)
+
+
+async def test_filesystem_store_symlink_probe_fails_closed_on_oserror(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """If ``Path.is_symlink`` raises during the probe, the operation must be refused."""
+    store = FileSystemAgentFileStore(tmp_path)
+    await store.write_file("ok.txt", "content")
+
+    def boom(self: Path) -> bool:
+        raise PermissionError("access denied")
+
+    monkeypatch.setattr(Path, "is_symlink", boom)
+
+    with pytest.raises(ValueError, match="symbolic link or reparse point"):
+        await store.read_file("ok.txt")
+
+
+def test_file_access_harness_classes_are_marked_experimental() -> None:
+    """File-access harness public classes should expose HARNESS experimental metadata."""
+    assert AgentFileStore.__feature_id__ == ExperimentalFeature.HARNESS.value
+    assert InMemoryAgentFileStore.__feature_id__ == ExperimentalFeature.HARNESS.value
+    assert FileSystemAgentFileStore.__feature_id__ == ExperimentalFeature.HARNESS.value
+    assert FileSearchMatch.__feature_id__ == ExperimentalFeature.HARNESS.value
+    assert FileSearchResult.__feature_id__ == ExperimentalFeature.HARNESS.value
+    assert FileAccessProvider.__feature_id__ == ExperimentalFeature.HARNESS.value
+    assert ".. warning:: Experimental" in (FileAccessProvider.__doc__ or "")
+
+
+async def test_in_memory_store_preserves_original_case_on_list_and_search() -> None:
+    """``list_files`` / ``search_files`` should return original-case names, not lowercased keys.
+
+    Matches :class:`FileSystemAgentFileStore` on case-preserving filesystems so
+    tests written against the in-memory backend cannot encode a contract that
+    will diverge in production.
+    """
+    store = InMemoryAgentFileStore()
+    await store.write_file("Plan.MD", "ERROR happens here\n")
+    await store.write_file("Reports/Q1.MD", "alpha")
+
+    # list_files keeps the original case
+    assert sorted(await store.list_files()) == ["Plan.MD"]
+    assert sorted(await store.list_files("Reports")) == ["Q1.MD"]
+
+    # case-insensitive directory lookup still works
+    assert sorted(await store.list_files("reports")) == ["Q1.MD"]
+
+    # search_files emits the original-case file name in FileSearchResult
+    results = await store.search_files("", "error", "*.MD")
+    assert [r.file_name for r in results] == ["Plan.MD"]
+
+    # read_file remains case-insensitive
+    assert await store.read_file("plan.md") == "ERROR happens here\n"
+
+
+async def test_filesystem_store_read_file_raises_value_error_on_non_utf8(tmp_path: Path) -> None:
+    """Binary / non-UTF-8 files should raise a clean ``ValueError`` rather than ``UnicodeDecodeError``.
+
+    The tool-layer wrapper relies on this contract to convert the failure into
+    a recoverable string response for the agent.
+    """
+    store = FileSystemAgentFileStore(tmp_path)
+    (tmp_path / "blob.bin").write_bytes(b"\x80\x81\x82\x83")
+
+    with pytest.raises(ValueError, match="not UTF-8 text"):
+        await store.read_file("blob.bin")
+
+
+async def test_filesystem_store_search_logs_skipped_non_utf8_files(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    """``search_files`` skips non-UTF-8 files but logs per-file and a summary so operators have signal."""
+    store = FileSystemAgentFileStore(tmp_path)
+    await store.write_file("notes.md", "ERROR happens here")
+    (tmp_path / "blob.bin").write_bytes(b"\x80\x81\x82\x83")
+
+    with caplog.at_level("INFO", logger="agent_framework._harness._file_access"):
+        results = await store.search_files("", "error")
+
+    assert [r.file_name for r in results] == ["notes.md"]
+    assert any("Skipping non-UTF-8 file during search" in rec.message for rec in caplog.records)
+    assert any("skipped 1 non-UTF-8 file" in rec.message for rec in caplog.records)
+
+
+async def test_file_access_tool_wrappers_surface_value_error_as_message(
+    chat_client_base: SupportsChatGetResponse,
+) -> None:
+    """Recoverable failures (bad path, oversized regex, non-UTF-8 read) should be returned as strings.
+
+    Without these wrappers the model sees a raw stack trace for "you used ``..``"
+    but a polite message for "the file already exists", which is the opposite
+    of what is recoverable.
+    """
+    session = AgentSession(session_id="session-1")
+    store = InMemoryAgentFileStore()
+    provider = FileAccessProvider(store=store)
+    agent = Agent(client=chat_client_base, context_providers=[provider])
+
+    _, options = await agent._prepare_session_and_messages(  # type: ignore[reportPrivateUsage]
+        session=session,
+        input_messages=[Message(role="user", contents=["work with files"])],
+    )
+    tools = options["tools"]
+    assert isinstance(tools, list)
+
+    save_file = _tool_by_name(tools, "file_access_save_file")
+    read_file = _tool_by_name(tools, "file_access_read_file")
+    delete_file = _tool_by_name(tools, "file_access_delete_file")
+    list_files = _tool_by_name(tools, "file_access_list_files")
+    search_files = _tool_by_name(tools, "file_access_search_files")
+
+    # Path-traversal attempts on each tool should return a clean string, not raise.
+    saved = await save_file.invoke(arguments={"file_name": "../escape.txt", "content": "x"})
+    assert "Could not save" in saved[0].text and "escape" in saved[0].text.lower()
+    read = await read_file.invoke(arguments={"file_name": "../escape.txt"})
+    assert "Could not read" in read[0].text
+    deleted = await delete_file.invoke(arguments={"file_name": "../escape.txt"})
+    assert "Could not delete" in deleted[0].text
+    listed = await list_files.invoke(arguments={"directory": "../escape"})
+    assert "Could not list" in listed[0].text
+
+    # Regex length cap should also be returned to the model as text.
+    too_long = "a" * 1024
+    searched = await search_files.invoke(arguments={"regex_pattern": too_long})
+    assert "Could not search files" in searched[0].text
+
+
+async def test_file_access_tool_read_file_wrapper_surfaces_non_utf8(
+    tmp_path: Path, chat_client_base: SupportsChatGetResponse
+) -> None:
+    """The read-file tool wrapper should convert a non-UTF-8 ``ValueError`` into a readable string."""
+    store = FileSystemAgentFileStore(tmp_path)
+    (tmp_path / "blob.bin").write_bytes(b"\x80\x81\x82\x83")
+
+    session = AgentSession(session_id="session-1")
+    provider = FileAccessProvider(store=store)
+    agent = Agent(client=chat_client_base, context_providers=[provider])
+
+    _, options = await agent._prepare_session_and_messages(  # type: ignore[reportPrivateUsage]
+        session=session,
+        input_messages=[Message(role="user", contents=["read it"])],
+    )
+    read_file = _tool_by_name(options["tools"], "file_access_read_file")
+    response = await read_file.invoke(arguments={"file_name": "blob.bin"})
+    assert "Could not read" in response[0].text and "UTF-8" in response[0].text
+
+
+_NEEDS_SYMLINK = "Symbolic links are not supported in this environment"
+
+
+async def test_filesystem_store_rejects_symlink_on_delete_search_and_list(tmp_path: Path) -> None:
+    """The same symlink probe must front delete/search/list, not just read/write."""
+    target = tmp_path / "outside.txt"
+    target.write_text("outside", encoding="utf-8")
+    root = tmp_path / "root"
+    root.mkdir()
+    link = root / "link.txt"
+    try:
+        link.symlink_to(target)
+    except (OSError, NotImplementedError) as exc:
+        pytest.skip(f"{_NEEDS_SYMLINK}: {exc!r}")
+
+    store = FileSystemAgentFileStore(root)
+
+    with pytest.raises(ValueError, match="symbolic link"):
+        await store.delete_file("link.txt")
+
+    # search_files of the root never touches the symlink leaf directly, but
+    # search_files of a symlinked *directory* path must be rejected by the
+    # safe-directory resolver.
+    dir_link = root / "alias_dir"
+    other_dir = tmp_path / "outside_dir"
+    other_dir.mkdir()
+    try:
+        dir_link.symlink_to(other_dir)
+    except (OSError, NotImplementedError) as exc:
+        pytest.skip(f"{_NEEDS_SYMLINK}: {exc!r}")
+
+    with pytest.raises(ValueError, match="symbolic link"):
+        await store.search_files("alias_dir", "anything")
+    with pytest.raises(ValueError, match="symbolic link"):
+        await store.list_files("alias_dir")
+
+
+async def test_filesystem_store_rejects_symlinked_intermediate_directory(tmp_path: Path) -> None:
+    """A symlink used as a non-leaf path segment must still be rejected.
+
+    The classic escape vector is ``root/aliased_dir/file.txt`` where
+    ``aliased_dir`` is a symlink to somewhere outside the root. The
+    ``_throw_if_contains_symlink`` walk must check every segment, not only
+    the leaf.
+    """
+    outside = tmp_path / "outside_dir"
+    outside.mkdir()
+    (outside / "secret.txt").write_text("payload", encoding="utf-8")
+    root = tmp_path / "root"
+    root.mkdir()
+    link = root / "aliased_dir"
+    try:
+        link.symlink_to(outside)
+    except (OSError, NotImplementedError) as exc:
+        pytest.skip(f"{_NEEDS_SYMLINK}: {exc!r}")
+
+    store = FileSystemAgentFileStore(root)
+
+    for op in ("read", "write", "delete"):
+        with pytest.raises(ValueError, match="symbolic link"):
+            if op == "read":
+                await store.read_file("aliased_dir/secret.txt")
+            elif op == "write":
+                await store.write_file("aliased_dir/secret.txt", "stomp")
+            else:
+                await store.delete_file("aliased_dir/secret.txt")

python/packages/core/tests/core/test_mcp.py

@@ -1161,6 +1161,43 @@ async def test_local_mcp_server_function_execution_error():
             await func.invoke(param="test_value")
 
 
+async def test_mcp_tool_reconnects_after_session_terminated_error():
+    """Session termination errors should reconnect once and retry the tool call."""
+
+    class TestServer(MCPTool):
+        def __init__(self, **kwargs: Any) -> None:
+            super().__init__(**kwargs)
+            self.connect_count = 0
+            self.sessions: list[Any] = []
+
+        async def connect(self, *, reset: bool = False) -> None:
+            self.connect_count += 1
+            self.session = Mock(spec=ClientSession)
+            self.sessions.append(self.session)
+            if self.connect_count == 1:
+                self.session.call_tool = AsyncMock(
+                    side_effect=McpError(types.ErrorData(code=-32000, message="Session terminated"))
+                )
+            else:
+                self.session.call_tool = AsyncMock(
+                    return_value=types.CallToolResult(content=[types.TextContent(type="text", text="recovered")])
+                )
+            self.is_connected = True
+
+        def get_mcp_client(self) -> _AsyncGeneratorContextManager[Any, None]:
+            return None
+
+    server = TestServer(name="test_server")
+    await server.connect()
+
+    result = await server.call_tool("test_tool", param="test_value")
+
+    assert _mcp_result_to_text(result) == "recovered"
+    assert server.connect_count == 2
+    assert server.sessions[0].call_tool.await_count == 1
+    assert server.sessions[1].call_tool.await_count == 1
+
+
 async def test_mcp_tool_call_tool_raises_on_is_error():
     """Test that call_tool raises ToolExecutionException when MCP returns isError=True."""
 
@@ -3260,6 +3297,68 @@ async def test_load_prompts_pagination_with_duplicates():
     assert [f.name for f in tool._functions] == ["prompt_1", "prompt_2"]
 
 
+async def test_load_tools_concurrent_reload_does_not_duplicate_tools_and_preserves_meta():
+    """Concurrent tool reloads should not duplicate functions or lose tools/list metadata."""
+    tool = MCPTool(name="test_tool")
+    mock_session = AsyncMock()
+    tool.session = mock_session
+    tool.load_tools_flag = True
+
+    page = Mock()
+    page.tools = [
+        types.Tool(
+            name="tool_1",
+            description="First tool",
+            inputSchema={"type": "object", "properties": {"param": {"type": "string"}}},
+            _meta={"echo": "tool_1"},
+        ),
+    ]
+    page.nextCursor = None
+
+    async def mock_list_tools(params: Any = None) -> Any:
+        assert params is None
+        await asyncio.sleep(0)
+        return page
+
+    mock_session.list_tools = AsyncMock(side_effect=mock_list_tools)
+
+    await asyncio.wait_for(asyncio.gather(tool.load_tools(), tool.load_tools()), timeout=1)
+
+    assert mock_session.list_tools.call_count == 2
+    assert [f.name for f in tool._functions] == ["tool_1"]
+    assert tool._tool_call_meta_by_name == {"tool_1": {"echo": "tool_1"}}
+
+
+async def test_load_prompts_concurrent_reload_does_not_duplicate_prompts():
+    """Concurrent prompt reloads should not duplicate functions."""
+    tool = MCPTool(name="test_tool")
+    mock_session = AsyncMock()
+    tool.session = mock_session
+    tool.load_prompts_flag = True
+
+    page = Mock()
+    page.prompts = [
+        types.Prompt(
+            name="prompt_1",
+            description="First prompt",
+            arguments=[types.PromptArgument(name="arg1", description="Arg 1", required=True)],
+        ),
+    ]
+    page.nextCursor = None
+
+    async def mock_list_prompts(params: Any = None) -> Any:
+        assert params is None
+        await asyncio.sleep(0)
+        return page
+
+    mock_session.list_prompts = AsyncMock(side_effect=mock_list_prompts)
+
+    await asyncio.wait_for(asyncio.gather(tool.load_prompts(), tool.load_prompts()), timeout=1)
+
+    assert mock_session.list_prompts.call_count == 2
+    assert [f.name for f in tool._functions] == ["prompt_1"]
+
+
 async def test_load_tools_pagination_exception_handling():
     """Test that load_tools handles exceptions during pagination gracefully."""
     from unittest.mock import AsyncMock
@@ -3891,6 +3990,31 @@ async def test_mcp_tool_safe_close_handles_cancelled_error():
     mock_exit_stack.aclose.assert_called_once()
 
 
+async def test_mcp_tool_safe_close_handles_cleanup_exception_group():
+    """Cleanup task groups should not hide the original connect failure."""
+    import builtins
+    from contextlib import AsyncExitStack
+
+    exception_group_type = getattr(builtins, "ExceptionGroup", None)
+    if exception_group_type is None:
+        pytest.skip("ExceptionGroup is not available on this Python version")
+
+    tool = MCPStreamableHTTPTool(
+        name="test",
+        url="http://example.com/mcp",
+        load_tools=False,
+        load_prompts=False,
+    )
+
+    mock_exit_stack = AsyncMock(spec=AsyncExitStack)
+    mock_exit_stack.aclose = AsyncMock(side_effect=exception_group_type("cleanup failed", [RuntimeError("reader")]))
+    tool._exit_stack = mock_exit_stack
+
+    await tool._safe_close_exit_stack()
+
+    mock_exit_stack.aclose.assert_called_once()
+
+
 async def test_connect_sets_logging_level_when_logger_level_is_set():
     """Test that connect() sets the MCP server logging level when the logger level is not NOTSET."""
 
@@ -4389,6 +4513,52 @@ async def test_mcp_tool_call_tool_forwards_tool_list_meta():
         assert server.session.call_tool.call_args.kwargs["meta"] == tool_meta
 
 
+async def test_mcp_tool_call_tool_user_meta_merges_with_tool_list_meta():
+    """User-provided _meta should be sent as MCP request metadata, not tool arguments."""
+    from opentelemetry import trace
+
+    tool_meta = {"from_tool": "tool-value", "shared": "tool-value"}
+    user_meta = {"from_user": "user-value", "shared": "user-value"}
+
+    class TestServer(MCPTool):
+        async def connect(self) -> None:
+            self.session = Mock(spec=ClientSession)
+            self.session.list_tools = AsyncMock(
+                return_value=types.ListToolsResult(
+                    tools=[
+                        types.Tool(
+                            name="test_tool",
+                            description="Test tool",
+                            inputSchema={"type": "object", "properties": {"param": {"type": "string"}}},
+                            _meta=tool_meta,
+                        )
+                    ]
+                )
+            )
+            self.session.call_tool = AsyncMock(
+                return_value=types.CallToolResult(content=[types.TextContent(type="text", text="result")])
+            )
+
+        def get_mcp_client(self) -> _AsyncGeneratorContextManager[Any, None]:
+            return None
+
+    server = TestServer(name="test_server")
+    async with server:
+        await server.load_tools()
+
+        with trace.use_span(trace.NonRecordingSpan(trace.INVALID_SPAN_CONTEXT)):
+            await server.call_tool("test_tool", param="test_value", _meta=user_meta)
+
+        call_kwargs = server.session.call_tool.call_args.kwargs
+        assert call_kwargs["arguments"] == {"param": "test_value"}
+        assert call_kwargs["meta"] == {
+            "from_tool": "tool-value",
+            "from_user": "user-value",
+            "shared": "user-value",
+        }
+        assert user_meta == {"from_user": "user-value", "shared": "user-value"}
+
+
 async def test_mcp_streamable_http_tool_hook_not_duplicated_on_repeated_get_mcp_client():
     """Test that calling get_mcp_client multiple times does not accumulate duplicate hooks."""
     tool = MCPStreamableHTTPTool(
@@ -4641,6 +4811,42 @@ async def test_mcp_streamable_http_tool_header_provider_with_httpx_event_hook():
             await tool._httpx_client.aclose()
 
 
+async def test_mcp_streamable_http_tool_header_provider_skips_cross_origin_redirect():
+    """The request hook must not re-add caller headers after a cross-origin redirect."""
+    import httpx
+
+    from agent_framework._mcp import _mcp_call_headers
+
+    tool = MCPStreamableHTTPTool(
+        name="test",
+        url="http://example.com/mcp",
+        header_provider=lambda kw: {"Authorization": f"Bearer {kw.get('token', '')}"},
+    )
+
+    try:
+        with patch("agent_framework._mcp.streamable_http_client"):
+            tool.get_mcp_client()
+
+            assert tool._httpx_client is not None
+            hooks = tool._httpx_client.event_hooks.get("request", [])
+            assert len(hooks) == 1
+
+            token = _mcp_call_headers.set({"Authorization": "Bearer secret"})
+            try:
+                same_origin = httpx.Request("POST", "http://example.com/redirected")
+                await hooks[0](same_origin)
+                assert same_origin.headers.get("Authorization") == "Bearer secret"
+
+                cross_origin = httpx.Request("POST", "http://attacker.example/capture")
+                await hooks[0](cross_origin)
+                assert "Authorization" not in cross_origin.headers
+            finally:
+                _mcp_call_headers.reset(token)
+    finally:
+        if getattr(tool, "_httpx_client", None) is not None:
+            await tool._httpx_client.aclose()
+
+
 async def test_mcp_streamable_http_tool_header_provider_with_user_httpx_client():
     """Test that header_provider works when the user provides their own httpx client."""
     import httpx

python/packages/core/tests/core/test_observability.py

@@ -3449,6 +3449,140 @@ def test_capture_response_with_error_type(span_exporter: InMemorySpanExporter):
     assert spans[0].attributes.get(OtelAttr.ERROR_TYPE) == "ValueError"
 
 
+def test_backfill_request_model_when_unknown(span_exporter: InMemorySpanExporter):
+    """_backfill_request_model updates the span name and REQUEST_MODEL attribute when unknown."""
+    from agent_framework.observability import OtelAttr, get_tracer
+
+    span_exporter.clear()
+    tracer = get_tracer()
+
+    attrs: dict[str, Any] = {
+        OtelAttr.OPERATION: "chat",
+        OtelAttr.REQUEST_MODEL: "unknown",
+        OtelAttr.RESPONSE_MODEL: "gpt-4o-mini",
+    }
+
+    with tracer.start_as_current_span("chat unknown") as span:
+        ChatTelemetryLayer._backfill_request_model(span, attrs)
+
+    assert attrs[OtelAttr.REQUEST_MODEL] == "gpt-4o-mini"
+    spans = span_exporter.get_finished_spans()
+    assert len(spans) == 1
+    assert spans[0].name == "chat gpt-4o-mini"
+
+
+def test_backfill_request_model_noop_when_request_model_known(span_exporter: InMemorySpanExporter):
+    """_backfill_request_model leaves a known REQUEST_MODEL and span name untouched."""
+    from agent_framework.observability import OtelAttr, get_tracer
+
+    span_exporter.clear()
+    tracer = get_tracer()
+
+    attrs: dict[str, Any] = {
+        OtelAttr.OPERATION: "chat",
+        OtelAttr.REQUEST_MODEL: "gpt-4o",
+        OtelAttr.RESPONSE_MODEL: "gpt-4o-mini",
+    }
+
+    with tracer.start_as_current_span("chat gpt-4o") as span:
+        ChatTelemetryLayer._backfill_request_model(span, attrs)
+
+    assert attrs[OtelAttr.REQUEST_MODEL] == "gpt-4o"
+    spans = span_exporter.get_finished_spans()
+    assert len(spans) == 1
+    assert spans[0].name == "chat gpt-4o"
+
+
+def test_backfill_request_model_noop_when_response_model_missing(span_exporter: InMemorySpanExporter):
+    """_backfill_request_model is a no-op when no RESPONSE_MODEL is available."""
+    from agent_framework.observability import OtelAttr, get_tracer
+
+    span_exporter.clear()
+    tracer = get_tracer()
+
+    attrs: dict[str, Any] = {
+        OtelAttr.OPERATION: "chat",
+        OtelAttr.REQUEST_MODEL: "unknown",
+    }
+
+    with tracer.start_as_current_span("chat unknown") as span:
+        ChatTelemetryLayer._backfill_request_model(span, attrs)
+
+    assert attrs[OtelAttr.REQUEST_MODEL] == "unknown"
+    spans = span_exporter.get_finished_spans()
+    assert len(spans) == 1
+    assert spans[0].name == "chat unknown"
+
+
+async def test_chat_client_backfills_request_model_from_response(span_exporter: InMemorySpanExporter):
+    """Non-streaming chat: when REQUEST_MODEL is unknown, the response model backfills it."""
+
+    class BackfillingChatClient(ChatTelemetryLayer, BaseChatClient[Any]):
+        def service_url(self):
+            return "https://test.example.com"
+
+        def _inner_get_response(
+            self, *, messages: MutableSequence[Message], stream: bool, options: dict[str, Any], **kwargs: Any
+        ) -> Awaitable[ChatResponse] | ResponseStream[ChatResponseUpdate, ChatResponse]:
+            async def _get() -> ChatResponse:
+                return ChatResponse(
+                    messages=[Message("assistant", ["Test response"])],
+                    model="resolved-model",
+                )
+
+            return _get()
+
+    client = BackfillingChatClient()
+    span_exporter.clear()
+    # Note: no "model" in options, so REQUEST_MODEL starts as "unknown".
+    await client.get_response(messages=[Message(role="user", contents=["Hi"])], options={})
+
+    spans = span_exporter.get_finished_spans()
+    assert len(spans) == 1
+    span = spans[0]
+    assert span.name == "chat resolved-model"
+    assert span.attributes[OtelAttr.REQUEST_MODEL] == "resolved-model"
+    assert span.attributes[OtelAttr.RESPONSE_MODEL] == "resolved-model"
+
+
+async def test_chat_client_streaming_backfills_request_model_from_response(
+    span_exporter: InMemorySpanExporter,
+):
+    """Streaming chat: when REQUEST_MODEL is unknown, the response model backfills it."""
+
+    class BackfillingStreamingChatClient(ChatTelemetryLayer, BaseChatClient[Any]):
+        def service_url(self):
+            return "https://test.example.com"
+
+        def _inner_get_response(
+            self, *, messages: MutableSequence[Message], stream: bool, options: dict[str, Any], **kwargs: Any
+        ) -> Awaitable[ChatResponse] | ResponseStream[ChatResponseUpdate, ChatResponse]:
+            async def _stream() -> AsyncIterable[ChatResponseUpdate]:
+                yield ChatResponseUpdate(contents=[Content.from_text("Hello")], role="assistant")
+                yield ChatResponseUpdate(contents=[Content.from_text(" world")], role="assistant", finish_reason="stop")
+
+            def _finalize(updates: Sequence[ChatResponseUpdate]) -> ChatResponse:
+                response = ChatResponse.from_updates(updates)
+                response.model = "resolved-stream-model"
+                return response
+
+            return ResponseStream(_stream(), finalizer=_finalize)
+
+    client = BackfillingStreamingChatClient()
+    span_exporter.clear()
+    stream = client.get_response(stream=True, messages=[Message(role="user", contents=["Hi"])], options={})
+    async for _ in stream:
+        pass
+    await stream.get_final_response()
+
+    spans = span_exporter.get_finished_spans()
+    assert len(spans) == 1
+    span = spans[0]
+    assert span.name == "chat resolved-stream-model"
+    assert span.attributes[OtelAttr.REQUEST_MODEL] == "resolved-stream-model"
+    assert span.attributes[OtelAttr.RESPONSE_MODEL] == "resolved-stream-model"
+
+
 def test_configure_otel_providers_with_env_file_path(monkeypatch, tmp_path):
     """Test configure_otel_providers with env_file_path creates new settings."""
     import importlib

python/packages/core/tests/core/test_sessions.py

@@ -307,6 +307,63 @@ class TestHistoryProviderBase:
         assert provider.stored[0].text == "hello"
         assert provider.stored[1].text == "hi"
 
+    async def test_after_run_stores_coalesced_code_interpreter_chunks(self) -> None:
+        from agent_framework import AgentResponse, AgentResponseUpdate, Content
+
+        provider = ConcreteHistoryProvider("mem", store_inputs=False)
+        updates = [
+            AgentResponseUpdate(
+                role="assistant",
+                contents=[
+                    Content.from_code_interpreter_tool_result(
+                        call_id="ci_123",
+                        outputs=[],
+                    )
+                ],
+            ),
+            AgentResponseUpdate(
+                contents=[
+                    Content.from_code_interpreter_tool_call(
+                        call_id="ci_123",
+                        inputs=[Content.from_text(text="import")],
+                        additional_properties={"sequence_number": 1},
+                    )
+                ],
+            ),
+            AgentResponseUpdate(
+                contents=[
+                    Content.from_code_interpreter_tool_call(
+                        call_id="ci_123",
+                        inputs=[Content.from_text(text=" pandas")],
+                        additional_properties={"sequence_number": 2},
+                    )
+                ],
+            ),
+            AgentResponseUpdate(
+                contents=[
+                    Content.from_code_interpreter_tool_call(
+                        call_id="ci_123",
+                        inputs=[Content.from_text(text="import pandas as pd")],
+                        additional_properties={"sequence_number": 3},
+                    )
+                ],
+            ),
+        ]
+        ctx = SessionContext(session_id="s1", input_messages=[Message(role="user", contents=["make a sheet"])])
+        ctx._response = AgentResponse.from_updates(updates)
+
+        await provider.after_run(agent=None, session=AgentSession(), context=ctx, state={})  # type: ignore[arg-type]
+
+        assert len(provider.stored) == 1
+        stored_contents = provider.stored[0].contents
+        calls = [content for content in stored_contents if content.type == "code_interpreter_tool_call"]
+        results = [content for content in stored_contents if content.type == "code_interpreter_tool_result"]
+        assert len(calls) == 1
+        assert len(results) == 1
+        assert calls[0].inputs is not None
+        assert len(calls[0].inputs) == 1
+        assert calls[0].inputs[0].text == "import pandas as pd"
+
     async def test_after_run_skips_inputs_when_disabled(self) -> None:
         from agent_framework import AgentResponse
 

python/packages/core/tests/core/test_skills.py

@@ -4086,8 +4086,8 @@ class TestClassSkill:
 
     async def test_content_is_cached(self) -> None:
         skill = _MinimalClassSkill()
-        content1 = (await skill.get_content())
-        content2 = (await skill.get_content())
+        content1 = await skill.get_content()
+        content2 = await skill.get_content()
         assert content1 is content2
 
     def test_resources_are_lazy_cached(self) -> None:
@@ -5587,8 +5587,8 @@ class TestInlineSkillContentCaching:
     async def test_content_cached_after_first_access(self) -> None:
         """InlineSkill.content returns the same object on subsequent accesses."""
         skill = InlineSkill(frontmatter=SkillFrontmatter(name="test-skill", description="Test"), instructions="Body")
-        first = (await skill.get_content())
-        second = (await skill.get_content())
+        first = await skill.get_content()
+        second = await skill.get_content()
         assert first is second  # Same object (cached)
         assert "<name>test-skill</name>" in first
 

python/packages/declarative/README.md

@@ -6,6 +6,18 @@ Please install this package via pip:
 pip install agent-framework-declarative --pre
 ```
 
+## Release stage
+
+This package ships at two different stability levels:
+
+- **Declarative workflows** (`WorkflowFactory`, executors, handlers, and the
+  `_workflows` surface) are at **release-candidate** stability and may receive only
+  minor refinements before GA.
+- **Declarative agents** (`AgentFactory` and the YAML agent loading/parsing path:
+  `DeclarativeLoaderError`, `ProviderLookupError`, `ProviderTypeMapping`) are
+  **experimental** and may change or be removed in future versions without notice.
+  Using any of these symbols emits an `ExperimentalWarning` on first use.
+
 ## Declarative features
 
 The declarative packages provides support for building agents based on a declarative yaml specification.

python/packages/declarative/agent_framework_declarative/__init__.py

@@ -1,5 +1,18 @@
 # Copyright (c) Microsoft. All rights reserved.
 
+"""Declarative specification support for Microsoft Agent Framework.
+
+Release stage:
+
+* The declarative-workflows surface (``WorkflowFactory``, executors, handlers,
+  etc.) is at release-candidate stability.
+* The declarative-agents surface (``AgentFactory`` and the YAML agent
+  loading/parsing path: ``DeclarativeLoaderError``, ``ProviderLookupError``,
+  ``ProviderTypeMapping``) is *experimental* and may change or be removed in
+  future versions without notice. Using these symbols emits an
+  ``ExperimentalWarning`` on first use.
+"""
+
 from importlib import metadata
 
 from ._loader import AgentFactory, DeclarativeLoaderError, ProviderLookupError, ProviderTypeMapping

python/packages/declarative/agent_framework_declarative/_loader.py

@@ -15,6 +15,10 @@ from agent_framework import (
 from agent_framework import (
     FunctionTool as AFFunctionTool,
 )
+from agent_framework._feature_stage import (  # type: ignore[reportPrivateUsage]
+    ExperimentalFeature,
+    experimental,
+)
 from agent_framework.exceptions import AgentException
 from dotenv import load_dotenv
 
@@ -43,6 +47,7 @@ else:
     from typing_extensions import TypedDict  # type: ignore # pragma: no cover
 
 
+@experimental(feature_id=ExperimentalFeature.DECLARATIVE_AGENTS)
 class ProviderTypeMapping(TypedDict, total=True):
     package: str
     name: str
@@ -118,18 +123,21 @@ PROVIDER_TYPE_OBJECT_MAPPING: dict[str, ProviderTypeMapping] = {
 }
 
 
+@experimental(feature_id=ExperimentalFeature.DECLARATIVE_AGENTS)
 class DeclarativeLoaderError(AgentException):
     """Exception raised for errors in the declarative loader."""
 
     pass
 
 
+@experimental(feature_id=ExperimentalFeature.DECLARATIVE_AGENTS)
 class ProviderLookupError(DeclarativeLoaderError):
     """Exception raised for errors in provider type lookup."""
 
     pass
 
 
+@experimental(feature_id=ExperimentalFeature.DECLARATIVE_AGENTS)
 class AgentFactory:
     """Factory for creating Agent instances from declarative YAML definitions.
 

python/packages/declarative/pyproject.toml

@@ -4,7 +4,7 @@ description = "Declarative specification support for Microsoft Agent Framework."
 authors = [{ name = "Microsoft", email = "af-support@microsoft.com"}]
 readme = "README.md"
 requires-python = ">=3.10"
-version = "1.0.0b260528"
+version = "1.0.0rc1"
 license-files = ["LICENSE"]
 urls.homepage = "https://aka.ms/agent-framework"
 urls.source = "https://github.com/microsoft/agent-framework/tree/main/python"
@@ -29,7 +29,7 @@ dependencies = [
 ]
 [dependency-groups]
 dev = [
-    "types-PyYaml==6.0.12.20250915"
+    "types-PyYaml==6.0.12.20260518"
 ]
 
 [tool.uv]
@@ -49,7 +49,8 @@ addopts = "-ra -q -r fEX"
 asyncio_mode = "auto"
 asyncio_default_fixture_loop_scope = "function"
 filterwarnings = [
-    "ignore:Support for class-based `config` is deprecated:DeprecationWarning:pydantic.*"
+    "ignore:Support for class-based `config` is deprecated:DeprecationWarning:pydantic.*",
+    "ignore::agent_framework._feature_stage.ExperimentalWarning",
 ]
 timeout = 120
 markers = [

python/packages/devui/agent_framework_devui/_server.py

@@ -375,13 +375,15 @@ class DevServer:
             logger.info("Starting Agent Framework Server")
             await self._ensure_executor()
             await self._ensure_openai_executor()  # Initialize OpenAI executor
-            yield
-            # Shutdown
-            logger.info("Shutting down Agent Framework Server")
+            try:
+                yield
+            finally:
+                # Shutdown
+                logger.info("Shutting down Agent Framework Server")
 
-            # Cleanup entity resources (e.g., close credentials, clients)
-            if self.executor:
-                await self._cleanup_entities()
+                # Cleanup entity resources (e.g., close credentials, clients)
+                if self.executor:
+                    await self._cleanup_entities()
 
         app = FastAPI(
             title="Agent Framework Server",

python/packages/durabletask/pyproject.toml

@@ -30,7 +30,7 @@ dependencies = [
 
 [dependency-groups]
 dev = [
-    "types-python-dateutil==2.9.0.20260402",
+    "types-python-dateutil==2.9.0.20260518",
 ]
 
 [tool.uv]

python/packages/foundry/agent_framework_foundry/_agent.py

@@ -57,8 +57,6 @@ if TYPE_CHECKING:
     from agent_framework import (
         Agent,
         AgentRunInputs,
-        ChatAndFunctionMiddlewareTypes,
-        ContextProvider,
         MiddlewareTypes,
         ToolTypes,
     )
@@ -507,10 +505,10 @@ class _FoundryAgentChatClient(  # type: ignore[misc]
         .. code-block:: python
 
             from agent_framework import Agent
-            from agent_framework.foundry import FoundryAgentClient
+            from agent_framework.foundry import FoundryAgent
             from azure.identity import AzureCliCredential
 
-            client = FoundryAgentClient(
+            client = FoundryAgent(
                 project_endpoint="https://your-project.services.ai.azure.com",
                 agent_name="my-prompt-agent",
                 agent_version="1",

python/packages/lab/pyproject.toml

@@ -57,19 +57,19 @@ math = [
 
 [dependency-groups]
 dev = [
-    "uv==0.11.6",
-    "ruff==0.15.8",
+    "uv==0.11.17",
+    "ruff==0.15.15",
     "pytest==9.0.3",
     "mypy==1.20.0",
     "pyright==1.1.408",
     #tasks
-    "poethepoet==0.42.1",
+    "poethepoet==0.46.0",
     "rich>=13.7.1,<15.0.0",
     "tomli==2.4.1",
     "tomli-w==1.2.0",
     # tau2 from source (not available on PyPI)
     "tau2@ git+https://github.com/sierra-research/tau2-bench@5ba9e3e56db57c5e4114bf7f901291f09b2c5619",
-    "prek==0.3.9",
+    "prek==0.4.3",
 ]
 
 [project.scripts]