fix(codex): omit historical turns when resuming threads

[dviejokfs]

Long Codex conversations could not continue because thread/resume returned their historical turns in a single JSON frame, exceeding the SDK's default 2 MiB limit. Request excludeTurns: true for resume and its active-writer fork fallback. Codex retains the saved context; only the response history is omitted. New-thread requests and the frame limit stay unchanged.

Evidence

• Affected thread: read-only thread/read with includeTurns: true returned 2,889,662 bytes (16 turns); about 2.66 MB was command-execution items.
• Actual thread/resume with excludeTurns: true on the same thread succeeded: 1,993 bytes, zero returned historical turns. No prompt/model turn sent.
• cargo test --locked resume_and_writer_conflict_fork_exclude_historical_turns failed before the fix (Null versus true).
• cargo test --locked --all-features: 312 passed, 1 existing ignored test.
• cargo clippy --locked --all-targets --all-features -- -D warnings: passed.
• cargo check --lib --locked: passed.
• cargo fmt --all and git diff --check: passed.

The generated schema from the installed Codex CLI documents excludeTurns on both resume and fork. An existing handshake regression verifies a metadata-only resume response still starts the next turn.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; the resume optimization is covered by focused tests and the prior documentation discoverability issue is fully addressed.

Findings

1.  Guide Is Not Discoverable ▶

Summary

This PR prevents oversized Codex resume responses by requesting metadata-only responses while preserving the provider’s saved conversation context.

• Adds excludeTurns: true to resumed threads and the active-writer fork fallback.
• Keeps new-thread behavior and the existing frame-size limit unchanged.
• Adds regression coverage for resume, fork, and new-thread request parameters.
• Documents the behavior in the changelog, README, how-to guide, and documentation portal.
• The previously reported documentation discoverability issue is fixed by registering the guide in the portal.

Diagram

sequenceDiagram
    participant Client
    participant SDK
    participant Codex

    Client->>SDK: Continue saved session
    SDK->>Codex: thread/resume(threadId, excludeTurns: true)
    alt Resume succeeds
        Codex-->>SDK: Thread metadata without historical turns
    else Active writer conflict
        SDK->>Codex: thread/fork(threadId, excludeTurns: true)
        Codex-->>SDK: Fork metadata without historical turns
    end
    SDK->>Codex: Start next turn

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_{Reviews (2) · Last reviewed commit: "docs: link the large Codex conversation ..."}

[greptile-apps]

Guide Is Not Discoverable

The documentation portal uses an explicit page registry, but this new guide is not registered there. As a result, users cannot find it through the portal navigation or search. Add it to site/src/content/docs.ts alongside the other how-to guides.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!