The mocked process.send consumed vitest's own fork-pool IPC messages and immediately ran the post callback, whose disconnect() severed the test worker's channel (process.connected is true under forks) — the whole spec's results vanished and win32-dialog-bindings.ts/win32-dialog-worker.ts fell to near-zero coverage on CI. The mock now records without invoking the callback or disconnecting; the real close lifecycle stays with built-worker.e2e.ts. Verified under both the threads and forks pools.