ordinary being f34e1a8105
fix(mcp): consume resolved notification snapshots instead of launching empty events (#6693)
* fix(mcp): consume resolved notification snapshots instead of launching empty events

A tracking-degraded snapshot recorded by a failed poll can resolve before any
notification worker claims it: the next poll succeeds, or an answered
input_required prompt returns the task to working. _record_event_if_changed
left that pending snapshot in place when the event disappeared, so
claim_notification_work rebuilt it as None and still claimed it, and the
service launched an empty notification run (dispatch_event or {}).

Consume such snapshots at claim time instead: advance notified_version, return
the status to none, clear the claim, and skip the row. The same guard consumes
rows left without a dispatch event by pre-fix claims, which would otherwise
relaunch empty notifications on every retry until dead-lettering.

* fix(mcp): clear consumed snapshot state for the review follow-ups

Review feedback on the claim-time consume guard:
- clear event_fingerprint when consuming, so an identical later attention
  event is recorded again instead of being suppressed by a snapshot that was
  never delivered;
- clear stale notification_error/attempt/dispatch state so a status
  projection cannot show a notification that no longer exists;
- cover the reclaimed expired-claim shape (claim, lease expiry, resolve,
  reclaim) and the identical-event sequence with regressions.

* docs(persistence): document the notification consume rule

mcp/AGENTS.md's effective chain has only 85 bytes of headroom on main (98,219 / 98,304), so the rule moves to persistence/AGENTS.md, which owns the mcp_tasks storage contract. No behavior change.

* fix(mcp): fence the notification consume against newer events (review)

Two P2 findings on the claim-time consume:
- the consume acknowledged the latest event version from a stale read, so on
  SQLite a completion recorded after the claim's SELECT was overwritten with
  status none and lost forever. The consume is now a conditional UPDATE fenced
  on the event version and phase that were read; a newer event makes it a
  no-op and stays claimable;
- a legacy launching/dispatched row whose dispatch payload is empty but whose
  event version moved on consumed that newer event. Such rows are now rebuilt
  and claimed; only a generation with nothing newer is consumed.
Regressions: a completion recorded while a claim is paused after its SELECT,
and legacy launching/dispatched rows with and without a newer completion.
2026-10-18 07:49:46 +08:00
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