forked from unom/punktfunk
enricobuehler
5e19a4611f
The client-decoder knee latch (decode_cap_kbps) was unreachable in production — zero "decode cap learned" lines across every field log, while its own doc named the exact sawtooth it exists to end (the 2026-08-03 1440p120 field trace: 220↔450 Mbps for nine minutes, five knee backoffs, no latch): - The ordinary two-bad-window backoff — the knee's most common presentation, a standing 15–45 ms decode rise below the severe tier — carried no decode evidence at decision time, because evidence was judged from the deciding window alone. Worse, the backoff the decode signal itself caused then RESET the knee streak. Now the streak carries its own attribution (streak_decode_windows): a backoff whose bad windows were all decode-flagged is decode evidence. - A cascade's second backoff can never agree with the first: a live host acks the ×0.7 request in ~100 ms, so the second sample always sits at the reduced rate — outside the ±1/8 similarity band by construction (0.7 < 7/8). The canonical test never acked between its backoffs, which is how the premise survived. Now a backoff only samples a rate the controller climbed back to (climb_since_backoff, armed by any ack that raises the rate); a drain-time backoff neither latches nor erases the reference the real knee set. - A keyframe-ask storm on a clean link (the Steam Deck presentation: the overdriven decoder wedges and begs instead of queueing — 14–19 asks at ~300 Mbps with loss_ppm=0 in the field traces) is decode evidence too; with real loss present the asks stay network-attributed. The reworked tests model the ack round-trip (choke → ack → re-climb → choke), including a regression test replaying the field trace's rates and decode figures, which must latch at its second knee encounter.