Commit Graph

19 Commits

  • Reapply "Move skills watcher to app-server" (#21652)
    ## Why
    
    PR #21460 reverted the earlier move of skills change watching from
    `codex-core` into app-server. This reapplies that boundary change so
    app-server owns client-facing `skills/changed` notifications and core no
    longer carries the watcher.
    
    ## What
    
    - Restore the app-server `SkillsWatcher` and register it from thread
    listener setup.
    - Remove the core-owned skills watcher and its core live-reload
    integration surface.
    - Restore app-server coverage for `skills/changed` notifications after a
    watched skill file changes.
    
    ## Validation
    
    - `cargo test -p codex-app-server --test all
    suite::v2::skills_list::skills_changed_notification_is_emitted_after_skill_change
    -- --exact --nocapture`
    - `cargo test -p codex-core --lib --no-run`
  • Move skills watcher to app-server (#21287)
    ## Why
    
    Skills update notifications are app-server API behavior, but the watcher
    lived in `codex-core` and surfaced through
    `EventMsg::SkillsUpdateAvailable`. Moving the watcher out keeps core
    focused on thread execution and lets app-server own both cache
    invalidation and the `skills/changed` notification.
    
    ## What changed
    
    - Added an app-server-owned skills watcher that watches local skill
    roots, clears the shared skills cache, and emits `skills/changed`
    directly.
    - Registers skill watches from the common app-server thread listener
    attach path, including direct starts, resumes, and app-server-observed
    child or forked threads.
    - Stores the `WatchRegistration` on `ThreadState`, so listener
    replacement, thread teardown, idle unload, and app-server shutdown
    deregister by dropping the RAII guard.
    - Removed `EventMsg::SkillsUpdateAvailable`, the core watcher, and the
    old core live-reload test.
    - Extended the app-server skills change test to verify a cached skills
    list is refreshed after a filesystem change without forcing reload.
    
    ## Validation
    
    - `cargo check -p codex-core -p codex-app-server -p codex-mcp-server -p
    codex-rollout -p codex-rollout-trace`
    - `cargo test -p codex-app-server
    skills_changed_notification_is_emitted_after_skill_change`
  • Remove core MCP list tools op (#21281)
    ## Why
    
    The core `Op::ListMcpTools` request path is no longer needed. Keeping it
    around left a dead request/response surface alongside the app-server MCP
    inventory APIs that own current server status listing.
    
    ## What Changed
    
    - Removed `Op::ListMcpTools`, `EventMsg::McpListToolsResponse`, and the
    core handler that built the MCP snapshot response.
    - Removed the now-unused `codex-mcp` snapshot wrapper/export and passive
    event handling arms in rollout and MCP-server consumers.
    - Updated tests that used the old op as a synchronization hook to wait
    on existing startup/skills events, and deleted the plugin test that only
    exercised the removed listing op.
    
    ## Validation
    
    - `cargo test -p codex-protocol`
    - `cargo test -p codex-mcp`
    - `cargo test -p codex-rollout -p codex-rollout-trace -p
    codex-mcp-server`
    - `cargo test -p codex-core --test all
    pending_input::queued_inter_agent_mail`
    - `cargo test -p codex-core --test all
    rmcp_client::stdio_mcp_tool_call_includes_sandbox_state_meta`
    - `cargo test -p codex-core --test all
    rmcp_client::stdio_image_responses`
    - `just fix -p codex-core -p codex-protocol -p codex-mcp -p
    codex-rollout -p codex-rollout-trace -p codex-mcp-server`
  • Move message history out of core (#21278)
    ## Why
    
    Message history was implemented inside `codex-core` and surfaced through
    core protocol ops and `SessionConfiguredEvent` fields even though the
    current consumer is TUI-local prompt recall. That made core own UI
    history persistence and exposed `history_log_id` / `history_entry_count`
    through surfaces that app-server and other clients do not need.
    
    This change moves message history persistence out of core and keeps the
    recall plumbing local to the TUI.
    
    ## What changed
    
    - Added a new `codex-message-history` crate for appending, looking up,
    trimming, and reading metadata from `history.jsonl`.
    - Removed core protocol history ops/events: `AddToHistory`,
    `GetHistoryEntryRequest`, and `GetHistoryEntryResponse`.
    - Removed `history_log_id` and `history_entry_count` from
    `SessionConfiguredEvent` and updated exec/MCP/test fixtures accordingly.
    - Updated the TUI to dispatch local app events for message-history
    append/lookup and keep its persistent-history metadata in TUI session
    state.
    
    ## Validation
    
    - `cargo test -p codex-message-history -p codex-protocol`
    - `cargo test -p codex-exec event_processor_with_json_output`
    - `cargo test -p codex-mcp-server outgoing_message`
    - `cargo test -p codex-tui`
    - `just fix -p codex-message-history -p codex-protocol -p codex-core -p
    codex-tui -p codex-exec -p codex-mcp-server`
  • [codex] Remove legacy ListSkills op (#21282)
    ## Why
    
    `skills/list` is already exposed through app-server v2 and covered by
    the app-server test suite. Keeping the separate core `Op::ListSkills`
    path leaves a duplicate legacy protocol surface that no longer needs to
    be maintained.
    
    ## What Changed
    
    - Removed `Op::ListSkills` and `EventMsg::ListSkillsResponse` from the
    core protocol.
    - Deleted the corresponding core session handler and stale core
    integration tests.
    - Removed rollout/MCP ignore branches and protocol v1 docs references
    for the deleted event/op.
    - Left app-server `skills/list` and its existing coverage intact.
    
    ## Validation
    
    - `cargo test -p codex-protocol`
    - `cargo test -p codex-core --test all suite::skills`
    - `cargo check -p codex-mcp-server -p codex-rollout -p
    codex-rollout-trace`
    - `just fix -p codex-core`
  • [codex] Move thread naming to app server (#21260)
    ## Why
    
    Thread names are app-server metadata now, backed by the thread store and
    sqlite state database. Keeping a core `SetThreadName` op plus a rollout
    `thread_name_updated` event made rename persistence live in the wrong
    layer and required historical replay support for an event that new
    app-server flows should not write.
    
    ## What changed
    
    - Removed `Op::SetThreadName` and `EventMsg::ThreadNameUpdated` from the
    core protocol and deleted the core handler path that appended rename
    events to rollouts.
    - Updated app-server `thread/name/set` so both loaded and unloaded
    threads write through thread-store metadata and app-server emits
    `thread/name/updated` notifications.
    - Updated local thread-store name metadata updates to write sqlite title
    metadata and the legacy thread-name index without appending rollout
    events.
    - Removed state extraction and rollout handling for the deleted
    thread-name event.
    
    ## Validation
    
    - `cargo test -p codex-app-server thread_name_updated_broadcasts`
    - `cargo test -p codex-app-server
    thread_name_set_is_reflected_in_read_list_and_resume`
    - `cargo test -p codex-thread-store
    update_thread_metadata_sets_name_on_active_rollout_and_indexes_name`
    - `cargo test -p codex-state`
    - `cargo check -p codex-mcp-server -p codex-rollout-trace`
    - `just fix -p codex-app-server -p codex-thread-store -p codex-state -p
    codex-mcp-server -p codex-rollout-trace`
    
    ## Docs
    
    No external documentation update is expected for this internal ownership
    change.
  • feat: add remote compaction v2 Responses client path (#20773)
    ## Why
    
    This adds the `remote_compaction_v2` client path so remote compaction
    can run through the normal Responses stream and install a
    `context_compaction` item that trigger a compaction.
    
    The goal is to migrate some of the compaction logic on the client side
    
    We keeps the v2 transport behind a feature flag while letting follow-up
    requests reuse the compacted context instead of falling back to the
    legacy compaction item shape.
    
    ## What changed
    
    - add `ResponseItem::ContextCompaction` and refresh the generated
    app-server / schema / TypeScript fixtures that expose response items on
    the wire
    - add `core/src/compact_remote_v2.rs` to send compaction through the
    standard streamed Responses client, require exactly one
    `context_compaction` output item, and install that item into compacted
    history
    - route manual compact and auto-compaction through the v2 path when
    `remote_compaction_v2` is enabled, while keeping the existing remote
    compaction path as the fallback
    - preserve the new item type across history retention, follow-up request
    construction, telemetry, rollout persistence, and rollout-trace
    normalization
    - add targeted coverage for the feature flag, `context_compaction`
    serialization, rollout-trace normalization, and remote-compaction
    follow-up behavior
    
    ## Verification
    
    - added protocol tests for `context_compaction`
    serialization/deserialization in `protocol/src/models.rs`
    - added rollout-trace coverage for `context_compaction` normalization in
    `rollout-trace/src/reducer/conversation_tests.rs`
    - added remote compaction integration coverage for v2 follow-up reuse
    and mixed compaction output streams in
    `core/tests/suite/compact_remote.rs`
    
    ---------
    
    Co-authored-by: Codex <noreply@openai.com>
  • [codex] Emit image view as core item (#20512)
    ## Why
    
    Image-view results should be represented as a core-produced turn item
    instead of being reconstructed by app-server. At the same time, existing
    rollout/history paths still understand the legacy `ViewImageToolCall`
    event, so this keeps that event as compatibility output generated from
    the new item lifecycle.
    
    ## What changed
    
    - Added `TurnItem::ImageView` to `codex-protocol`.
    - Emitted image-view item start/completion directly from the core
    `view_image` handler.
    - Kept `ViewImageToolCall` as a legacy event and generate it from
    completed `TurnItem::ImageView` items.
    - Kept `thread_history.rs` on the legacy `ViewImageToolCall` replay
    path, with `ImageView` item lifecycle events ignored there.
    - Updated app-server protocol conversion, rollout persistence, and
    affected exhaustive event matches for the new item plus legacy fan-out
    shape.
    
    ## Verification
    
    - `cargo test -p codex-protocol -p codex-app-server-protocol -p
    codex-rollout -p codex-rollout-trace -p codex-mcp-server -p
    codex-app-server --lib`
    - `cargo test -p codex-core --test all
    view_image_tool_attaches_local_image`
    - `just fix -p codex-protocol -p codex-core -p codex-app-server-protocol
    -p codex-app-server -p codex-rollout -p codex-rollout-trace -p
    codex-mcp-server`
    - `git diff --check`
  • [codex] Remove unused event messages (#20511)
    ## Why
    
    Several legacy `EventMsg` variants were still emitted or mapped even
    though clients either ignored them or had moved to item/lifecycle
    events. `Op::Undo` had also degraded to an unavailable shim, so this
    removes that dead task path instead of preserving a command that cannot
    do useful work.
    
    `McpStartupComplete`, `WebSearchBegin`, and `ImageGenerationBegin` are
    intentionally kept because useful consumers still depend on them: MCP
    startup completion drives readiness behavior, and the begin events let
    app-server/core consumers surface in-progress web-search and
    image-generation items before the final payload arrives.
    
    ## What Changed
    
    - Removed weak legacy event variants and payloads from `codex-protocol`,
    including legacy agent deltas, background events, and undo lifecycle
    events.
    - Kept/restored `EventMsg::McpStartupComplete`,
    `EventMsg::WebSearchBegin`, and `EventMsg::ImageGenerationBegin` with
    serializer and emission coverage.
    - Updated core, rollout, MCP server, app-server thread history,
    review/delegate filtering, and tests to rely on the useful replacement
    events that remain.
    - Removed `Op::Undo`, `UndoTask`, the undo test module, and stale TUI
    slash-command comments.
    - Stopped agent job/background progress and compaction retry notices
    from emitting `BackgroundEvent` payloads.
    
    ## Verification
    
    - `cargo check -p codex-protocol -p codex-app-server-protocol -p
    codex-core -p codex-rollout -p codex-rollout-trace -p codex-mcp-server`
    - `cargo test -p codex-protocol -p codex-app-server-protocol -p
    codex-rollout -p codex-rollout-trace -p codex-mcp-server`
    - `cargo test -p codex-core --test all suite::items`
    - `just fix -p codex-protocol -p codex-app-server-protocol -p codex-core
    -p codex-rollout -p codex-rollout-trace -p codex-mcp-server`
    - Earlier coverage on this PR also included `codex-mcp`, `codex-tui`,
    core library tests, MCP/plugin/delegate/review/agent job tests, and MCP
    startup TUI tests.
  • [rollout-tracer] Match analysis messages on encrypted id. (#20123)
    In some setups the summary or raw content can be dropped between
    requests. This triggers a check in the reducer which expects that the
    messages should remain identical between requests.
    
    This PR relaxes the checks to only focus on the encrypted ID instead. It
    also changes the reducer to keep the most rich version of the message
    observed during the rollout (this ensures that we don't accidentally
    lose the CoT nor summary when available).
  • [rollout-trace] Include x-request-id in rollout trace. (#20066)
    ## Why
    
    Rollout traces need an identifier that can be used to correlate a Codex
    inference with upstream Responses API, proxy, and engine logs. The
    reduced trace model already exposed `upstream_request_id`, but it was
    being populated from the Responses API `response.id`. That value is
    useful for `previous_response_id` chaining, but it is not the transport
    request id that upstream systems key on.
    
    This PR separates those concepts so trace consumers can reliably answer
    both questions:
    
    - which Responses API response did this inference produce?
    - which upstream request handled it?
    
    ## Structure
    
    The change keeps the upstream request id at the same lifecycle level as
    the provider stream:
    
    - `codex-api` captures the `x-request-id` HTTP response header when the
    SSE stream is created and exposes it on `ResponseStream`. Fixture and
    websocket streams set the field to `None` because they do not have that
    HTTP response header.
    - `codex-core` carries that stream-level id into `InferenceTraceAttempt`
    when recording terminal stream outcomes. Completed, failed, cancelled,
    dropped-stream, and pre-response error paths all record the id when it
    is available.
    - `rollout-trace` now records both identifiers in raw terminal inference
    events and response payloads: `response_id` for the Responses API
    `response.id`, and `upstream_request_id` for `x-request-id`.
    - The reducer stores both fields on `InferenceCall`. It also uses
    `response_id` for `previous_response_id` conversation linking, which
    removes the old accidental dependency on the misnamed
    `upstream_request_id` field.
    - Terminal inference reduction now consumes the full terminal payload
    (`InferenceCompleted`, `InferenceFailed`, or `InferenceCancelled`) in
    one place. That keeps status, partial payloads, response ids, and
    upstream request ids consistent across success, failure, cancellation,
    and late stream-mapper events.
    
    ## Why This Shape
    
    `x-request-id` is a property of the HTTP/provider response envelope, not
    an SSE event. Capturing it once in `codex-api` and plumbing it through
    terminal trace recording avoids trying to infer the value from stream
    contents, and it preserves the id even when the stream fails or is
    cancelled after only partial output.
    
    Keeping `response_id` separate from `upstream_request_id` also makes the
    reduced trace model less surprising: `response_id` remains the
    conversation-continuation id, while `upstream_request_id` is the
    operational correlation id for upstream debugging.
    
    ## Validation
    
    The PR updates trace and reducer coverage for:
    
    - reading `x-request-id` from SSE response headers;
    - storing the true upstream request id on completed inference calls;
    - preserving upstream request ids for cancelled and late-cancelled
    inference streams;
    - keeping `previous_response_id` reconstruction tied to `response_id`
    rather than transport request ids.
  • [codex] Trace cancelled inference streams (#19839)
    Records cancelled inference streams when Codex stops consuming a
    provider response before `response.completed`, preserving complete
    output items observed before cancellation.
    
    Also closes still-running inference calls when the owning turn ends, so
    reduced rollout traces do not leave stale `Running` inference nodes.
    
    Covered by focused reducer coverage and a core stream-drop test for
    partial output preservation.
  • Add goal app-server API (2 / 5) (#18074)
    Adds the app-server v2 goal API on top of the persisted goal state from
    PR 1.
    
    ## Why
    
    Clients need a stable app-server surface for reading and controlling
    materialized thread goals before the model tools and TUI can use them.
    Goal changes also need to be observable by app-server clients, including
    clients that resume an existing thread.
    
    ## What changed
    
    - Added v2 `thread/goal/get`, `thread/goal/set`, and `thread/goal/clear`
    RPCs for materialized threads.
    - Added `thread/goal/updated` and `thread/goal/cleared` notifications so
    clients can keep local goal state in sync.
    - Added resume/snapshot wiring so reconnecting clients see the current
    goal state for a thread.
    - Added app-server handlers that reconcile persisted rollout state
    before direct goal mutations.
    - Updated the app-server README plus generated JSON and TypeScript
    schema fixtures for the new API surface.
    
    ## Verification
    
    - Added app-server v2 coverage for goal get/set/clear behavior,
    notification emission, resume snapshots, and non-local thread-store
    interactions.
  • permissions: make profiles represent enforcement (#19231)
    ## Why
    
    `PermissionProfile` is becoming the canonical permissions abstraction,
    but the old shape only carried optional filesystem and network fields.
    It could describe allowed access, but not who is responsible for
    enforcing it. That made `DangerFullAccess` and `ExternalSandbox` lossy
    when profiles were exported, cached, or round-tripped through app-server
    APIs.
    
    The important model change is that active permissions are now a disjoint
    union over the enforcement mode. Conceptually:
    
    ```rust
    pub enum PermissionProfile {
        Managed {
            file_system: FileSystemSandboxPolicy,
            network: NetworkSandboxPolicy,
        },
        Disabled,
        External {
            network: NetworkSandboxPolicy,
        },
    }
    ```
    
    This distinction matters because `Disabled` means Codex should apply no
    outer sandbox at all, while `External` means filesystem isolation is
    owned by an outside caller. Those are not equivalent to a broad managed
    sandbox. For example, macOS cannot nest Seatbelt inside Seatbelt, so an
    inner sandbox may require the outer Codex layer to use no sandbox rather
    than a permissive one.
    
    ## How Existing Modeling Maps
    
    Legacy `SandboxPolicy` remains a boundary projection, but it now maps
    into the higher-fidelity profile model:
    
    - `ReadOnly` and `WorkspaceWrite` map to `PermissionProfile::Managed`
    with restricted filesystem entries plus the corresponding network
    policy.
    - `DangerFullAccess` maps to `PermissionProfile::Disabled`, preserving
    the “no outer sandbox” intent instead of treating it as a lax managed
    sandbox.
    - `ExternalSandbox { network_access }` maps to
    `PermissionProfile::External { network }`, preserving external
    filesystem enforcement while still carrying the active network policy.
    - Split runtime policies that legacy `SandboxPolicy` cannot faithfully
    express, such as managed unrestricted filesystem plus restricted
    network, stay `Managed` instead of being collapsed into
    `ExternalSandbox`.
    - Per-command/session/turn grants remain partial overlays via
    `AdditionalPermissionProfile`; full `PermissionProfile` is reserved for
    complete active runtime permissions.
    
    ## What Changed
    
    - Change active `PermissionProfile` into a tagged union: `managed`,
    `disabled`, and `external`.
    - Keep partial permission grants separate with
    `AdditionalPermissionProfile` for command/session/turn overlays.
    - Represent managed filesystem permissions as either `restricted`
    entries or `unrestricted`; `glob_scan_max_depth` is non-zero when
    present.
    - Preserve old rollout compatibility by accepting the pre-tagged `{
    network, file_system }` profile shape during deserialization.
    - Preserve fidelity for important edge cases: `DangerFullAccess`
    round-trips as `disabled`, `ExternalSandbox` round-trips as `external`,
    and managed unrestricted filesystem + restricted network stays managed
    instead of being mistaken for external enforcement.
    - Preserve configured deny-read entries and bounded glob scan depth when
    full profiles are projected back into runtime policies, including
    unrestricted replacements that now become `:root = write` plus deny
    entries.
    - Regenerate the experimental app-server v2 JSON/TypeScript schema and
    update the `command/exec` README example for the tagged
    `permissionProfile` shape.
    
    ## Compatibility
    
    Legacy `SandboxPolicy` remains available at config/API boundaries as the
    compatibility projection. Existing rollout lines with the old
    `PermissionProfile` shape continue to load. The app-server
    `permissionProfile` field is experimental, so its v2 wire shape is
    intentionally updated to match the higher-fidelity model.
    
    ## Verification
    
    - `just write-app-server-schema`
    - `cargo check --tests`
    - `cargo test -p codex-protocol permission_profile`
    - `cargo test -p codex-protocol
    preserving_deny_entries_keeps_unrestricted_policy_enforceable`
    - `cargo test -p codex-app-server-protocol
    permission_profile_file_system_permissions`
    - `cargo test -p codex-app-server-protocol serialize_client_response`
    - `cargo test -p codex-core
    session_configured_reports_permission_profile_for_external_sandbox`
    - `just fix`
    - `just fix -p codex-protocol`
    - `just fix -p codex-app-server-protocol`
    - `just fix -p codex-core`
    - `just fix -p codex-app-server`
  • [rollout_trace] Add debug trace reduction command (#18880)
    ## Summary
    
    Adds the debug CLI entry point for reducing recorded rollout traces.
    This gives developers a direct way to inspect whether the emitted trace
    stream reduces into the expected conversation/runtime model.
    
    ## Stack
    
    This is PR 5/5 in the rollout trace stack.
    
    - [#18876](https://github.com/openai/codex/pull/18876): Add rollout
    trace crate
    - [#18877](https://github.com/openai/codex/pull/18877): Record core
    session rollout traces
    - [#18878](https://github.com/openai/codex/pull/18878): Trace tool and
    code-mode boundaries
    - [#18879](https://github.com/openai/codex/pull/18879): Trace sessions
    and multi-agent edges
    - [#18880](https://github.com/openai/codex/pull/18880): Add debug trace
    reduction command
    
    ## Review Notes
    
    This PR is intentionally last: it depends on the trace crate, core
    recorder, runtime/tool events, and session/agent edge data all existing.
    The command should remain a debug/developer tool and avoid adding new
    runtime behavior.
    
    The useful review question is whether the CLI exposes the reducer in the
    smallest practical way for local inspection without turning the debug
    command into a supported user-facing workflow.
  • [rollout_trace] Trace tool and code-mode boundaries (#18878)
    ## Summary
    
    Extends rollout tracing across tool dispatch and code-mode runtime
    boundaries. This records canonical tool-call lifecycle events and links
    code-mode execution/wait operations back to the model-visible calls that
    caused them.
    
    ## Stack
    
    This is PR 3/5 in the rollout trace stack.
    
    - [#18876](https://github.com/openai/codex/pull/18876): Add rollout
    trace crate
    - [#18877](https://github.com/openai/codex/pull/18877): Record core
    session rollout traces
    - [#18878](https://github.com/openai/codex/pull/18878): Trace tool and
    code-mode boundaries
    - [#18879](https://github.com/openai/codex/pull/18879): Trace sessions
    and multi-agent edges
    - [#18880](https://github.com/openai/codex/pull/18880): Add debug trace
    reduction command
    
    ## Review Notes
    
    This PR is about attribution. Reviewers should focus on whether direct
    tool calls, code-mode-originated tool calls, waits, outputs, and
    cancellation boundaries are recorded with enough source information for
    deterministic reduction without coupling the reducer to live runtime
    internals.
    
    The stack remains valid after this layer: tool and code-mode traces
    reduce through the existing crate model, while the broader session and
    multi-agent relationships are added in the next PR.
  • [rollout_trace] Record core session rollout traces (#18877)
    ## Summary
    
    Wires rollout trace recording into `codex-core` session and turn
    execution. This records the core model request/response, compaction, and
    session lifecycle boundaries needed for replay without yet tracing every
    nested runtime/tool boundary.
    
    ## Stack
    
    This is PR 2/5 in the rollout trace stack.
    
    - [#18876](https://github.com/openai/codex/pull/18876): Add rollout
    trace crate
    - [#18877](https://github.com/openai/codex/pull/18877): Record core
    session rollout traces
    - [#18878](https://github.com/openai/codex/pull/18878): Trace tool and
    code-mode boundaries
    - [#18879](https://github.com/openai/codex/pull/18879): Trace sessions
    and multi-agent edges
    - [#18880](https://github.com/openai/codex/pull/18880): Add debug trace
    reduction command
    
    ## Review Notes
    
    This layer is the first live integration point. The important review
    question is whether trace recording is isolated from normal session
    behavior: trace failures should not become user-visible execution
    failures, and recording should preserve the existing turn/session
    lifecycle semantics.
    
    The PR depends on the reducer/data model from the first stack entry and
    only introduces the core recorder surface that later PRs use for richer
    runtime and relationship events.
  • [rollout_trace] Add rollout trace crate (#18876)
    ## Summary
    
    Adds the standalone `codex-rollout-trace` crate, which defines the raw
    trace event format, replay/reduction model, writer, and reducer logic
    for reconstructing model-visible conversation/runtime state from
    recorded rollout data.
    
    The crate-level design is documented in
    [`codex-rs/rollout-trace/README.md`](https://github.com/openai/codex/blob/codex/rollout-trace-crate/codex-rs/rollout-trace/README.md).
    
    ## Stack
    
    This is PR 1/5 in the rollout trace stack.
    
    - [#18876](https://github.com/openai/codex/pull/18876): Add rollout
    trace crate
    - [#18877](https://github.com/openai/codex/pull/18877): Record core
    session rollout traces
    - [#18878](https://github.com/openai/codex/pull/18878): Trace tool and
    code-mode boundaries
    - [#18879](https://github.com/openai/codex/pull/18879): Trace sessions
    and multi-agent edges
    - [#18880](https://github.com/openai/codex/pull/18880): Add debug trace
    reduction command
    
    ## Review Notes
    
    This PR intentionally does not wire tracing into live Codex execution.
    It establishes the data model and reducer contract first, with
    crate-local tests covering conversation reconstruction, compaction
    boundaries, tool/session edges, and code-cell lifecycle reduction. Later
    PRs emit into this model.
    
    The README is the best entry point for reviewing the intended trace
    format and reduction semantics before diving into the reducer modules.