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>
Mark
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