Phase 2c review follow-up on the id()-reuse persistence fix:
- test_recycled_id_in_dedup_set_still_persists_new_message seeded an EMPTY
dedup set, so it never injected a collision and passed under id-based dedup
too (couldn't distinguish the designs). Replace with
test_stale_seed_id_from_prior_flush_cannot_suppress_new_message, which asserts
the durable invariant: the seed is empty after every flush (mutation-checked:
removing the post-flush reset now fails BOTH id-reuse tests).
- Refresh the _flush_messages_to_session_db docstring: it still described the
old per-session identity tracking; document the intrinsic-marker mechanism,
that _flushed_db_message_ids is now a one-shot seed, and the shared-dict
mutation safety note.
_flush_messages_to_session_db deduped persisted messages with a retained
{id(msg)} set (_flushed_db_message_ids) kept across turns. Once a flushed dict
is dropped from the live list (scaffolding rewind / in-place compaction) and
GC'd, CPython recycles its address onto a new assistant/tool dict whose id()
collides with the stale entry — so the real turn is silently never written to
state.db.
Replace the retained id-set with an intrinsic _DB_PERSISTED_MARKER stamped on
each dict. The id-set is demoted to a one-shot seed (valid only while the
caller's objects are alive) that is translated to markers and cleared after
every flush, so no id() outlives a flush to alias a future message. The marker
is _-prefixed so the wire sanitizers strip it before any request leaves.
Preserves the existing _is_ephemeral_scaffolding skip. Salvaged from #50372.
Co-authored-by: rrevenanttt <290873280+rrevenanttt@users.noreply.github.com>
