Two data-loss / leak gaps in HindsightMemoryProvider.on_session_switch
introduced by #17409.
1. Buffered turns silently lost when retain_every_n_turns > 1.
on_session_switch unconditionally cleared _session_turns without
flushing. Users who batched every N>1 turns and switched mid-batch
(/reset, /new, /resume, /branch, or context compression) had those
buffered turns disappear. Same data-loss class as the shutdown race,
different lifecycle event.
Note commit_memory_session() -> on_session_end() runs *before*
on_session_switch on /reset, but Hindsight doesn't implement
on_session_end so the buffer survives that step and dies at clear
time. /resume, /branch, and compression skip commit_memory_session
entirely so an on_session_end impl wouldn't help them anyway.
Fix: snapshot the old _session_id, _document_id, _parent_session_id,
_turn_index, and _session_turns; spawn one final retain that lands
under the OLD document_id; then rotate state. Metadata is built
synchronously against the old self._* so session_id / lineage tags
on the flushed item all reference the prior session consistently.
2. Stale _prefetch_result leaks across switch.
If queue_prefetch ran in the old session and the result hadn't been
consumed by prefetch() yet, on_session_switch left the cached recall
text in place. The next session's first prefetch() call would return
text mined from the prior session's bank/query.
Fix: join any in-flight _prefetch_thread (3s bounded — matches
shutdown()), then clear _prefetch_result under _prefetch_lock before
rotating session_id.
Tests
-----
- tests/plugins/memory/test_hindsight_provider.py (TestSessionSwitchBufferFlush):
- buffered turns flushed under OLD document_id with OLD lineage tags
- empty buffer => no spurious retain
- _prefetch_result cleared on switch
- in-flight prefetch thread is awaited before clear (no race)
- tests/agent/test_memory_session_switch.py: factory extended to seed the
attrs the new flush path reads (_retain_source, _platform, _bank_id,
prefetch state, etc.) and stub _run_hindsight_operation so existing
switch-state assertions keep passing without network setup.
c38dac742b