The /api/session handler already has _t0.._t6 local timers plus an
env-var-gated [SLOW] WARNING that logs the total wall time and the
_tN-to-_tN+1 deltas, but only when HERMES_DEBUG_SLOW is set or total
>= 2s. In production we cannot rely on the env var, and the 2s
threshold means the typical chat-open (sub-2s on Tier 1) never logs
at all — we only see the worst cases, never the marginal ones that
would tell us where the next bottleneck is.
This wires the handler into the existing RequestDiagnostics framework:
- add ('GET', '/api/session') to the allowlist
- call RequestDiagnostics.maybe_start() at the _t0 boundary
- call stage() at each of _t1.._t6
- call finish() before the response returns
The watchdog fires _on_timeout (with thread stack snapshot) when the
request crosses the per-path slow threshold, and finish() emits a
single structured log line on the same threshold crossing. The
existing env-var-gated [SLOW] log stays as a no-diag fallback.
Greptile P1 trap avoidance: previous allowlist additions for similar
endpoints were flagged as dead code because the handler was never
updated to call maybe_start/finish. Both halves are present in this
commit so the watchdog entry actually registers.
No behavior change observable on the happy path (diag is None for
non-allowlisted paths; the existing _tN log is the fallback for both
None-diag and slow cases). No public API change. The /api/sessions
and /api/profiles handlers already use this pattern.
3a330ceff5