The spawn-time output tail (#93608) puts child stdout into flowing mode at
spawn. Both backend spawn paths in main.ts then await claimBackendChild
(whose Windows Get-Process probe cold-starts in 2-8s) and boot-progress IPC
BEFORE waitForDashboardPortAnnouncement attaches its stdout listener. Node
streams never replay consumed chunks to late listeners, so a READY sentinel
printed during that window was lost forever — the wait hit its 90s timeout
and a healthy backend was killed (deterministic on Windows, racy on
macOS/Linux; still firing on v0.21.0 incl. concurrent multi-profile boots).
Fix (belt and suspenders, both spawn paths — primary and profile pool):
- create the port-announcement promise immediately after spawn, before any
await
- new bufferedOutput option on waitForDashboardPortAnnouncement: after
attaching its own listener, waitForDashboardPort scans the output tail's
already-buffered text for the sentinel, making listener-attach ordering
irrelevant regardless of call-site shape
The readyFile path was already ordering-safe (it polls a file, not the
stream). Approach follows stale PR #60986 by @ParaWheeler, rebased onto the
output-tail/readyFile plumbing added since.
Fixes#60323
A start-marker probe failure (Get-Process timing out on a PowerShell 5.1
cold start, #87169) in claimBackendChild used to stop the freshly spawned
backend and rethrow — killing a healthy backend, triggering the renderer's
repair respawn, and looping. And because stderr piping only attached after
the claim, every before-ready failure surfaced as a bare exit code.
- extract probe + claim policy into electron/backend-claim.ts:
processStartMarker/execText (moved verbatim from main.ts), probeStartMarker,
and a pure claimDecision(childAlive, probe) a Windows CI lane can drive
with real PowerShell
- probe failure + LIVE child now degrades to PID-only identity
(pid-only:<pid> marker, WARNING logged), matching the existing
createParentStartMarkerResolver degrade pattern; processIdentityMatches
verifies degraded identities by PID liveness (command check still layers
on top in backendIdentityMatches)
- probe failure + DEAD child keeps the fail-closed throw, now carrying the
child's buffered stderr/stdout tail
- ring-buffered ~8KB output tail attached at spawn time in BOTH spawn paths
(pool + primary); tail appended to claim errors, before-ready exit
messages, and backend-ready's exited-before-port-announcement errors so
the real exit reason reaches desktop.log and the boot UI
- tests: claimDecision matrix (degrade test fails against the old
stop+throw behavior), real processStartMarker probe, ring-buffer caps,
and output-tail suffixes on backend-ready exit errors
hermes-seaeye[bot]