After `hermes update`, an existing state.db on an old schema made every
GET /api/sessions poll fail with sqlite3.OperationalError "no such
column: s.last_read_at" (or s.last_activity_at) until something
unrelated forced a writable open — the desktop sidebar showed "No
sessions yet" while every row sat intact on disk (#79531, #80037).
Two remaining root causes (the stale hand-written read probe was
already replaced by the SCHEMA_SQL-derived probe on main, prototyped in
draft PR #80030 by @Tilly-YL):
1. Migrations ran lazily: _init_schema/_reconcile_columns only ran on a
writable open, typically the user's first NEW session. The dashboard
backend now schedules one writable open of its own state.db from the
lifespan (daemon thread, never blocks the ready-probe socket, never
raises), so the store is brought current before the first session-
list poll on every `hermes serve` / `hermes dashboard` / Desktop
headless entrypoint.
2. _reconcile_columns caught sqlite3.OperationalError around every
ALTER TABLE ADD COLUMN and logged at DEBUG. Lock contention from
orphaned sibling backends made the ALTER fail silently — startup
"succeeded" with a half-reconciled schema, and the open-time lock
patience (#74478) never saw the error because it was swallowed
inside first. Now: "duplicate column" races stay at DEBUG,
locked/busy re-raises so _connect_and_init_with_lock_patience
retries the whole idempotent init with jittered backoff, and any
other failure (e.g. un-ADDable NOT NULL) logs at WARNING.
Regression tests: a store missing sessions.last_read_at is healed by
the eager startup reconcile and serves list_sessions_rich; a locked
ALTER propagates and is retried to success by the open lock patience;
duplicate-column races stay quiet; other ALTER failures warn.
Fixes#79531Fixes#80037
Reported-by: @yenhunghuang (#79531) and @FLOW3R0111 (#80037)
Root-cause analysis: @wangyi0177-eng (stale read probe) and
@www654cc-pixel (_reconcile_columns DEBUG-swallow under lock
contention); draft PR #80030 by @Tilly-YL prototyped the probe fix.
f45813ea77