Max Weinbach7/14/2026, 3:53:27 AM

On Bun >=1.3 --max-concurrency only gates test.concurrent, which this
repo never uses, so the flag serialized nothing. Real parallelism was
measured and rejected for now: --parallel implies per-file isolation,
re-importing the src graph + jsdom preload per file (+2.2s/file, ~4-5x
total CPU), netting only 25% on 16 cores and a regression on CI-sized
runners; --shard surfaced 61 cross-file mock/state coupling failures.
docs/bun-native-migration.md records the measurements and re-adoption
criteria. Workflow pin tests now assert the flag never returns.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

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