fix(agent): treat gateway 413 as prompt-too-long

[brandonleung]

Problem

Cloud tasks running Cloudflare-hosted models (e.g. @cf/zai-org/glm-5.2) through the LLM gateway fail permanently once a resumed transcript outgrows the model's context window: the gateway rejects every attempt with HTTP 413, the run ends in error, and each orchestrator restart replays the same oversized transcript indefinitely.

Changes

The oversized-resume recovery already exists (retryOversizedResumeOnFreshSession restarts the run on a fresh session with summarized history) but only triggered on Anthropic's "prompt is too long" phrasing.

• isPromptTooLongError now also matches the gateway's 413 shapes ("exceeded this model context window limit" and any API Error: 413), so the recovery fires instead of the restart loop.
• 413 stays a non-retryable agent_error, pinned by test, so transient-retry paths never burn attempts on it.

How did you test this?

Each matcher has a unit case only it matches (deleting any one pattern fails a test), and the agent-server fresh-session-retry test drives the full wrapped gateway 413 message through the recovery end-to-end. vitest, tsc, and biome pass.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

[trunk-io]

😎 Merged directly without going through the merge queue, as the queue was empty and the PR was up to date with the target branch - details.

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit c445055.}

[posthog]

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[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix(agent): treat gateway 413 as prompt-..." | Re-trigger Greptile}

[brandonleung]

/trunk merge