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JamesandClaude Opus 4.7
8bac7ba0d1
Part of Phase 2 of the distributed rendering plan (determinism hardening).
See DISTRIBUTED-RENDERING-PLAN.md §5.2 (Math.random row) and §17.2
(gating table).
The existing `VIRTUAL_TIME_SHIM` freezes Date.now / performance.now / rAF
on a render seek but leaves `Math.random` and `crypto.getRandomValues` as
native non-deterministic. Compositions that paint stochastic visuals
through these APIs produce different pixels on distributed retries.
This change adds `buildVirtualTimeShim({ seedRandomFromFrame: boolean })`.
Default `false` returns a string byte-identical to today's
`VIRTUAL_TIME_SHIM` (pinned by a new unit test). When `true`, the script
additionally:
- Installs a Mulberry32 PRNG with a single uint32 state
- Reseeds the state from the current virtual time on every
`seekToTime(ms)` call (Knuth multiplicative hash + golden-ratio offset)
- Replaces `Math.random` with the PRNG output
- Replaces `crypto.getRandomValues` to fill the buffer from the PRNG
`VIRTUAL_TIME_SHIM` (the const consumed by `renderOrchestrator` +
`probeStage`) is now `buildVirtualTimeShim({ seedRandomFromFrame: false })`
— in-process behavior unchanged, producer regression baselines unaffected.
Phase 3 distributed primitives will pass `true` when building the chunk
worker's file-server scripts.
10 new unit tests at packages/producer/src/services/
fileServer-seededRandom.test.ts use node:vm to evaluate the shim in
isolated contexts and pin both branches:
- default emits no RNG override and leaves Math.random native
- locked emits the seeded block, produces identical sequences across
fresh VMs at the same time, and yields different sequences for
different times
This is part of a stack of 10 PRs; this is PR 4 of 10.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>