Mark 1fb3e978cb feat(option-c-offscreen): port health probe + request-id'd BUFFER + H1 try/catch ...

Implements the offscreen-side architectural refactor per
.planning/debug/empty-archive-port-race.md "Fix Strategy: Option C":

1. **Retired** the 290_000 ms pre-emptive reconnect setTimeout. Its race
   window between the synchronous .disconnect() and the onDisconnect
   handler running was the bisect-confirmed proximate cause of the H1
   "Attempting to use a disconnected port object" Uncaught Errors.

2. **Added** PONG-based health probe: each ping increments missedPongs;
   if MAX_MISSED_PONGS (3) consecutive PINGs go without echo, reconnect
   via the same clean teardown path the onDisconnect handler uses.
   PONG receipt resets the counter. Liveness-based replacement for the
   time-based pre-emptive rotation.

3. **H1 fix** — wrap PING postMessage in try/catch. The port object can
   transition to disconnected synchronously (SW eviction, port glitch)
   between the interval-callback being queued and it running. The catch
   absorbs the throw and routes through reconnectPort() — no more
   uncaught throws bubble out to the offscreen console.

4. **Request-id'd protocol** — REQUEST_BUFFER carries the SW-generated
   requestId; BUFFER response echoes it. The offscreen now posts on the
   CURRENT keepalivePort (no more portAtRequest stale-port refuse-to-
   post). The SW matches BUFFER → request by id, so port replacement
   mid-encode no longer drops the response — the SW retries on the new
   port and the matching BUFFER routes correctly.

5. **reconnectPort(reason)** — new helper consolidating the
   teardown+disconnect+reconnect dance used by both the missed-PONG
   path and the synchronous-throw path. Idempotent w.r.t. the chained
   onDisconnect callback.

Test updates:
  - H2 now sends REQUEST_BUFFER with a requestId (Option C contract).
  - H1.b refactored to test the externally-disconnected path (since the
    pre-emptive timeout path is gone): port._disconnected=true, fire
    ping, assert no throw + a fresh port appears.
  - Top-level snapshots of timer globals + afterEach restoration so a
    failing test doesn't leak overridden globals into the next test.

Status: 48 GREEN, 4 RED (the remaining RED is all SW-side — addressed
in next commit). All H1 + H1.b + H2 contracts now GREEN. Pinning
contracts (D-12 port-serialization, D-13 segment-rotation, A3 webm-
playback) untouched. tsc --noEmit exit 0; type-safety grep clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-05-16 14:37:22 +02:00

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