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JamesandClaude Opus 4.7
c139197b37
Part of Phase 2 of the distributed rendering plan (determinism hardening).
See DISTRIBUTED-RENDERING-PLAN.md §5.2 (lastFrameCache row) and §17.2
(gating table).
Adds `discardWarmupCapture(session, frameIndex=0, time=0, innerCapture?)`
in packages/engine/src/services/frameCapture.ts. Performs one capture
through the standard `captureFrameCore` path, throws the buffer away, and
restores the session's perf and BeginFrame damage counters.
Distributed chunk workers need this because Chrome's BeginFrame screenshot
pipeline maintains a per-process `lastFrameCache`: when a captured frame's
`hasDamage` reports `false`, the screenshot path returns the previously
captured buffer. For chunk N (N > 0) the worker has no prior frame in its
cache, so the very first capture's `hasDamage` reporting diverges from
what an in-process render at the same absolute frame index would see (the
in-process renderer always has frame N-1 cached). Running a discarded
warmup capture before the first real capture primes the cache so chunk
output is byte-identical to in-process output.
The wrapper:
- Takes an injectable `innerCapture` so tests can stub the Chrome path
(default is the real `captureFrameCore`).
- Restores `session.capturePerf`, `beginFrameHasDamageCount`, and
`beginFrameNoDamageCount` after the inner call — even on error — so
warmup captures don't pollute `getCapturePerfSummary()` averages.
- Writes no file to disk.
In-process behavior is unchanged: no caller invokes the new helper yet.
Phase 3's `renderChunk()` will run it as the first step after
`initializeSession` resolves.
Re-exported from packages/engine/src/index.ts.
7 unit tests at packages/engine/src/services/
frameCapture-discardWarmup.test.ts cover the post-conditional contract:
single inner-capture invocation, perf/damage restoration on success,
restoration on error, no-fs-write.
This is part of a stack of 10 PRs; this is PR 6 of 10.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>