The three salvaged PRs (#46647, #54583, #55013) were authored against a
tree where _refresh_agent_cache_message_count was sync and _session_db was
the raw SessionDB. On current main the helper is async and awaits the
AsyncSessionDB facade, and _run_agent was split into _run_agent_inner.
- Wrap test _session_db in AsyncSessionDB so the awaited get_session works
- Make refresh-calling tests async + await the helper
- Point the placement-guard test at _run_agent_inner (recursion lives there
post-mixin-extraction)
- Relocated production call sites now correctly await the async helper
The cross-process cache-coherence guard (#45966) compares a session's
on-disk message_count against a snapshot stored next to the cached agent,
rebuilding the agent on a mismatch so a foreign writer (e.g. the dashboard
backend) can't leave the in-memory transcript stale.
On a fresh gateway conversation the post-turn re-baseline
(_refresh_agent_cache_message_count) ran BEFORE the first-turn `session_meta`
marker row was appended to the transcript. That append goes through
append_to_transcript -> append_message, which increments message_count
unconditionally. So the snapshot was left exactly one short of the live
count, and on turn 2 of every fresh conversation the guard mistook this
process's own session_meta write for a foreign write, evicting and rebuilding
the cached agent — silently busting the per-conversation prompt cache the
cache exists to protect.
Move the re-baseline to after the turn's full transcript persistence block
(including the session_meta append and the compression session_id swap). The
snapshot now matches the live count, so the guard fires only on genuinely
foreign writes. This also makes the call honor its own documented contract of
using the compaction-updated session_id.
Adds a regression test that drives the real _handle_message_with_agent
against a real SessionDB and asserts the invariant: after a fresh first turn,
snapshot == live message_count, so the next turn's guard reuses the cached
agent. Fails before this change, passes after.
