POSIX rename(2) atomically replaces dest even when readers hold open
handles. Windows MoveFileEx (which fs.renameSync uses with
MOVEFILE_REPLACE_EXISTING) cannot — it throws EPERM/EBUSY when another
process has the destination open. Concurrent install.js readers and
antivirus scanners are realistic triggers; both release within ms.
renameAtomicWithRetry() preserves the bare renameSync call on POSIX
(no overhead) and on Windows retries up to 4 times with 10/30/90/270ms
backoff, then falls back to copyFileSync + unlinkSync. If even copy
fails because dest is hard-locked, log a non-fatal warning and leave
the prior dest in place — a subsequent build retries from a fresh
state. The build no longer crashes on Windows transient locking.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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