quest: plan the TS export's remaining MP2 join hole

quest/m1/test-flakes-2/README.md

@@ -35,6 +35,7 @@ Public API: none. Wire: none.
 
 ## Required
 
+- [TS MP2 join hole](/quest/m1/test-flakes-2/ts-mp2-join-hole.md) - the TS export skips no MPEG-1 audio group right after its live join, fixed at the cause
 - [Auth refresh mocks time](/quest/m1/test-flakes-2/auth-refresh-mock-time.md) - moq-relay's auth refresh and fixed-lease tests measure a grant's life on one mocked clock
 - [uring teardown close](/quest/m1/test-flakes-2/uring-teardown-close.md) - moq-uring's published-close teardown test holds under load, fixed at its cause
 - [Relay burst drill](/quest/m1/test-flakes-2/relay-burst-impaired.md) - the impaired transport-peer burst drill never aborts its subscription while the link is up

quest/m1/test-flakes-2/ts-mp2-join-hole.md

@@ -0,0 +1,52 @@
+# [M] TS export loses no MP2 group after its live join
+
+## Goal
+
+TS validation's "TS full multiplex at its own rate" step (`just test ts --full`) passes
+reliably because the exporter never skips an MPEG-1 audio group right after it joins.
+The fix lands at the cause, with a deterministic regression test that fails without it.
+
+## Plan
+
+Seen 2026-10-17 on #5857's TS validation run 39042472016 (head 754a5af, `main` with
+#5854 plus a test-only change). PID 0x101 lost 96 ms in one 120 ms step at 2.390 s,
+right after the capture's first MP2 frame. The exporter logged it itself, so this is
+real loss, not one of the ffprobe ghost holes #5854 fixed in `holes.py`:
+`media skipped upstream ... track="2.mp2" at=2.389977s skipped=120ms`.
+
+Evidence kept from that run's `ts-failure` artifact, which expires about 2026-10-24
+and holds only INFO logs, not the consumer's decisions:
+
+- Publisher instance up at 15:04:31.10. The subscriber subscribed to `2.mp2` at
+  15:04:33.082 with `max_delay: 450ms`, `start_group: None`, `order: Descending`. The
+  relay forwarded the same upstream at 15:04:33.083.
+- The skip was logged at 15:04:33.143, about 60 ms after subscribing. The capture's
+  first MP2 frame is at 2.366 s against a source starting at 1.070 s. Video starts at
+  2.080 s, AC-3 at 2.515 s, both without holes.
+- MP2 is published as one group per 24 ms frame, about five per PES, so the 120 ms
+  step is about one PES.
+
+What #5854 already rules out: the zero-budget race it fixed (reproduced by
+`a_live_start_loses_no_group_the_publisher_bursts`), since this SUBSCRIBE carried the
+real budget. What it doesn't rule out: the consumer measures `max_delay` in media time
+(`max_timestamp - next_start`), not wall time, so 60 ms after subscribing is no bound.
+The publisher had run about two seconds before the join, so its cache could hand the
+budget a backlog spanning that much media time even though the relay held none.
+
+Suspicion, unverified: #5854's live latch (`container::Consumer::live`) starts at the
+newest group *announced* when any frame first arrives, and drops what lies below it.
+A group's announcement and its frames race on separate streams, and the backlog
+arrives beside the live groups. So the latch, or the budget's skip rules right after
+it, may misjudge a burst that is still in flight.
+
+First step: reproduce it deterministically over `moq_net::transport::memory`, the way
+#5857's test does. Use a publisher holding a backlog when the live export joins, then
+bursting a PES of one-frame groups. Trace which skip or latch rule declares the gap
+before choosing a fix.
+
+Public API: none expected. Wire: none expected.
+
+## Related
+
+- [Audio join budget](/quest/m2/audio-join-budget.md) - moq-audio's live join may share the same race; whichever lands first should check the other
+- [TS fidelity and recovery](/quest/m1/ts-reliability/README.md) - loss after a late join is part of the TS contract

quest/m2/audio-join-budget.md

@@ -20,3 +20,6 @@ Reproduce it the same way first: a publisher bursting one-frame groups over
 budget from the start and keep the warmup reach local, as the export now picks its live
 edge in the consumer instead of on the wire.
 
+## Related
+
+- [TS MP2 join hole](/quest/m1/test-flakes-2/ts-mp2-join-hole.md) - the TS export still loses MP2 groups after its live join; it may share this race