Codex review of #4502 flagged that a bare `.catch(() => undefined)`
neutralizes the unhandledRejection but leaves the affected `runInTab`
call blocked inside `runCmuxCode` until timeout when the in-flight
code does not make another cmux socket request (e.g. `await
wait(60_000)`). `releaseTab` was signaling the run only by rejecting
an orphaned promise.
Wire the tab-close event all the way into the cmux run body:
- `PendingRun` gains a `closeAc: AbortController` that `releaseTab`
aborts BEFORE calling `pending.reject`. `wait(...)` (via
`waitForBrowserRun` -> `untilAborted`), in-flight cmux socket calls
(via CmuxTab's `#request` -> `untilAborted`), and facade proxies
(via `bindBrowserRunFacade`) all consume the composed signal, so
the run body unwinds within a microtask instead of blocking to its
own timeout.
- `runInTabWithSnapshot`'s cmux branch composes `closeAc.signal` into
the run's signal (`AbortSignal.any([opts.signal, closeAc.signal])`)
and now publishes `runCmuxCode(...)`'s outcome to the shared
`promise` via `.then(resolve, reject)` and returns `await promise`.
Both branches thus await the same promise, so `pending.reject`
always has an attached handler (removing the original crash) AND
the caller sees `Tab "..." was closed` immediately instead of
waiting on the run's timeout.
- Drop the defensive `promise.catch(() => undefined)` — the promise
is now actively consumed on both backends.
The new regression test adds a second case that exercises the
reviewer's exact scenario (`await wait(60_000);`) and asserts:
1. `pending.closeAc.signal.aborted` flips from `false` to `true`
across `releaseTab`, with the tab-close error as its reason.
2. The awaited `runInTab(...)` rejects with `Tab "..." was closed`.
3. No `unhandledRejection` fires.
Verified locally by temporarily removing `closeAc.abort(...)` in
`releaseTab` — the new assertions fail; restoring it makes them pass.
Fixes#4499
roboomp
a6a8258945