Chat/event-plane quality work for the amended Phase 1 scope of #94484
(maintainer restructure: lean chat/event plane, no control-plane
changes). Three fixes came out of a source-level comparison against
OpenHands, Chainlit, VS Code, Zed, LangGraph, and Goose.
1. Per-turn trace_id + active-turn telemetry: _start_inflight_turn mints
a 12-hex trace_id; _event_frame stamps it on every event frame in the
turn, so a client can correlate the full lifecycle (dispatch -> first
token -> tool calls -> complete) from one identifier — none of the six
surveyed projects has frame-level turn correlation.
session.events.stats now reports active_turns (session_id, trace_id,
elapsed_s, streaming).
2. Transient vs durable events (OpenHands StreamingDeltaEvent pattern):
message.delta / thinking.delta are stamped with seqs (live ordering
holds) but never buffered — one streaming turn emitted hundreds of
delta frames and evicted every durable control event from the
512-slot ring, defeating replay for the exact reconnect window it
exists to cover. The ring now evicts manually and records the highest
DURABLE seq dropped, so truncated means real data loss and delta-only
gaps no longer false-positive.
3. Seq-namespace epoch (Goose stale-cursor recovery): event_replay.EPOCH
(8-hex per boot) is announced in gateway.ready and echoed by
session.events.since; the client drops its seq watermarks when the
epoch changes, so a stale HIGH watermark from a previous gateway
process can no longer suppress replay/gap-detection forever. Legacy
backends without an epoch are unaffected (client keeps watermarks).
Validation: Python 85/85 across replay/entry_ws/keepalive/protocol
(12 replay tests, 3 new); vitest 9/9 shared (2 new epoch tests), 66/66
desktop; full tui_gateway sweep 614/615 (1 known ordering flake, passes
in isolation). Live e2e on this tree: 12-event turn -> seqs contiguous
1..12, 8 durable frames buffered + 4 deltas live-only, single trace_id
on all frames, active_turns elapsed_s matches the real turn duration.
Research provenance: NousResearch/hermes-agent#94484 (comparative-scan
comment); techniques credited to OpenHands (transient split), Goose
(epoch/stale-cursor), per maintainer-restructured plan.
kshitijk4poor
874fab0ce0