PR #29211 dropped JSONL gateway transcripts and noted that the platform's
own `message_id` field (used by Yuanbao's recall guard to redact a
message by exact platform id) was no longer preserved — falling back to
content-match. That fallback works for the common case but redacts the
wrong row when two messages share text (or fails to match when content
is post-processed).
Restore exact-id matching by giving state.db a column for it:
- New `platform_message_id TEXT` column on the messages table
(SCHEMA_VERSION bump 11 → 12; column added via declarative reconciler
on existing DBs, no version-gated migration block needed)
- Partial index `idx_messages_platform_msg_id` on
(session_id, platform_message_id) to keep recall's point-lookup cheap
even on large sessions
- `append_message()` and `replace_messages()` accept the new value:
the gateway-facing `append_to_transcript` in `gateway/session.py`
forwards either `message["platform_message_id"]` or the legacy
`message["message_id"]` key (yuanbao's existing convention)
- `get_messages_as_conversation()` surfaces the column back on the
message dict as `message_id` so platform code reads the same shape
it used to read from JSONL
- Yuanbao `_patch_transcript`: restore branch A1 (exact id match)
ahead of A2 (content match) ahead of B (system-note). Both branches
log which one fired so operators can tell from gateway.log whether
recall hit the canonical path or had to fall back.
Tests:
- New low-level round-trip tests in `test_hermes_state.py` for both
`append_message` and `replace_messages` paths
- The PR's `test_yuanbao_recall_db_only.py` was rewritten to assert
the new contract: branch A1 (id match) works against DB-only
transcripts, and branch A2 (content match) still recovers rows that
were observed without a platform id (e.g. agent-processed @bot
messages where run.py doesn't carry msg_id through)
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