Verification review — reviewed the diff for correctness.

What I checked:

1. Dedup logic — the backward scan through messages correctly stops at the first user role message, preventing false matches from earlier turns. The normalization via _normalize_interim_visible_text ensures whitespace differences don't cause duplicate appends.
2. Two recovery paths — partial_stream_recovery uses final_response while interrupted uses _current_streamed_assistant_text (stripped of think blocks). Both paths are correctly gated.
3. Append-before-persist ordering — the new assistant message is appended to messages before _persist_session is called, so the persisted session includes the recovered text.
4. Test coverage — both partial_stream_recovery and interrupted paths have dedicated tests that verify the persisted messages contain the expected assistant text. copy.deepcopy in the capture mock is correct for snapshot isolation.

Verdict: Clean. The fix correctly addresses the data loss scenario where interrupted or partially-recovered streams leave no assistant message in the persisted session.

Verified clean — LGTM

Reviewed the diff: turn_finalizer.py persist-on-interrupt fix + 2 tests.

What I checked:

• Dedup loop correctness: Iterates backward through messages, checks each assistant message against normalized visible text. Stops at first user message boundary (prevents matching a stale assistant message from a previous turn). Uses _normalize_interim_visible_text + _strip_think_blocks for robust comparison. ✓
• Insertion timing: _visible_assistant_text is appended to messages before _persist_session(messages) is called. This ensures the persisted conversation includes the interrupted/visible text. ✓
• Two paths covered:
  • partial_stream_recovery → uses final_response directly
  • interrupted → uses _current_streamed_assistant_text (stripped of think blocks)
  • Neither path → _visible_assistant_text is None → no append. ✓
• No double-persist: If the assistant message is already in messages (e.g., from a previous recovery), the dedup loop sets _already_persisted = True and skips the append. ✓
• Test coverage: test_partial_stream_recovery_persists_recovered_assistant_message and test_interrupted_stream_persists_visible_assistant_text both verify the persisted message is the last entry. ✓

Edge case note: The _drop_trailing_empty_response_scaffolding call happens before the dedup check. If scaffolding removes an empty assistant message that happens to match, the dedup correctly re-appends the real content. This is the right order.

Heads up that this overlaps in intent with #45277 (which I just opened for #43936) but they fix different layers and are complementary — flagging so a reviewer can consider them together.

• This PR (fix(agent): persist delivered assistant text on interrupted turns #43962) backfills already-delivered visible assistant text in turn_finalizer.py when messages is missing the assistant row (interrupt / partial_stream_recovery). It fixes the case where the row never made it into the turn's message list.
• fix(agent): identity-based session-DB flush — stop positional assistant drops (#43936) #45277 fixes the case where the assistant row is present in messages but _flush_messages_to_session_db skips it. The flush was position-based (messages[max(start_idx, _last_flushed_db_idx):]); two divergence paths (a cursor corrupted by overlapping turns, and conversation_history growing longer than messages after repair_message_sequence shrinks a drop-poisoned history) make the slice land past the end, so a completed, delivered assistant response is silently dropped. It replaces the slice with identity-based dedup.

They don't conflict: a row this PR appends carries no _db_persisted stamp and isn't in _hist_ids, so #45277's flush writes it exactly once. And the divergence path #45277 covers (a non-interrupt, repair-shrink loop on a turn that did append its assistant row) is outside this PR's interrupted / partial_stream_recovery conditions, so the two cover the prevention and the recovery sides of #43936 respectively. Either can land independently.