diff --git a/.github/scripts/pr_limit_moderation.js b/.github/scripts/pr_limit_moderation.js
new file mode 100644
index 0000000000..489a06ea78
--- /dev/null
+++ b/.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,
+};
diff --git a/.github/tests/test_pr_limit_moderation.js b/.github/tests/test_pr_limit_moderation.js
new file mode 100644
index 0000000000..67192c8327
--- /dev/null
+++ b/.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);
+  });
+});
diff --git a/.github/workflows/limit-community-prs.yml b/.github/workflows/limit-community-prs.yml
new file mode 100644
index 0000000000..2fe66ccd20
--- /dev/null
+++ b/.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,
+            });