The typed failure boundary is a strong improvement overall: cancellation is authoritative, worker diagnostics stay immutable and attached to the representative failure, and the first fatal worker now stops sibling capture without hiding cleanup. The linear same-line I/O scan and 100k-character adversarial test also close the CodeQL finding without broadening classification.

One retry regression remains:

• [P1] Preserve retryability for the drawElement worker watchdog timeout — packages/engine/src/services/captureFailure.ts:57-64 enumerates protocol timeout strings but omits the engine's own drawElement worker encode timed out (frame N) failure. That error is produced by the 30-second lost-message/OOM-killed-worker watchdog at packages/engine/src/services/drawElementService.ts:674-684 (and the batch sibling at :901-906), then propagates through captureFrameRange's awaited encodeResult. On this exact head, classifyCaptureFailure(new Error("drawElement worker encode timed out (frame 42)")) returns authoring, so parallelCoordinator.ts:594-598 treats it as fatal and aborts peers, while renderOrchestrator.ts:817-821 refuses the worker-halving retry. Before this PR, the broad timed out recovery matcher covered this concrete failure. Please classify this exact watchdog failure as non-fatal/retryable and pin both classification and recovery behavior with a regression test.

Exact head reviewed: 9ad957786d14040f72b87ac2f72ac59a028e6f90. All exact-head required checks are green; this is a code-contract blocker rather than a CI failure.

Verdict: REQUEST CHANGES
Reasoning: The typed model and peer-abort mechanism are sound, but a real engine-generated worker timeout regresses from retryable to fatal, causing avoidable render failures instead of the prior recovery path.

— Magi