fix(backend): guard intermediate DB flush with is_final_attempt flag

Add is_final_attempt field to _RetryState so intermediate DB flushes
only run on attempt 0 (optimistic — most turns succeed first try) and
the final retry attempt. Middle retry attempts may be rolled back, and
messages already flushed to DB would persist as orphans since the
in-memory rollback (session.messages truncation) has no corresponding
DB delete.

autogpt_platform/backend/backend/copilot/sdk/service.py

@@ -266,6 +266,7 @@ class _RetryState:
     adapter: SDKResponseAdapter
     transcript_builder: TranscriptBuilder
     usage: _TokenUsage
+    is_final_attempt: bool = True
 
 
 @dataclass
@@ -1493,9 +1494,14 @@ async def _run_stream_attempt(
             # --- Intermediate persistence ---
             # Flush session messages to DB periodically so page reloads
             # show progress during long-running turns.
+            # Guarded by is_final_attempt: earlier retry attempts may be
+            # rolled back in memory (session.messages truncated), but
+            # messages already flushed to DB would persist as orphans.
+            # is_final_attempt is True on attempt 0 (optimistic — most
+            # turns succeed on the first try) and on the last retry.
             _msgs_since_flush += 1
             now = time.monotonic()
-            if (
+            if state.is_final_attempt and (
                 _msgs_since_flush >= _FLUSH_MESSAGE_THRESHOLD
                 or (now - _last_flush_time) >= _FLUSH_INTERVAL_SECONDS
             ):
@@ -1986,6 +1992,11 @@ async def stream_chat_completion_sdk(
         )
 
         for attempt in range(_MAX_STREAM_ATTEMPTS):
+            # Enable intermediate DB flushes on attempt 0 (optimistic: most
+            # turns succeed on the first try) and the last attempt.  Middle
+            # retry attempts may be rolled back, and flushed messages would
+            # persist as DB orphans — so flushes are disabled for those.
+            state.is_final_attempt = attempt == 0 or attempt == _MAX_STREAM_ATTEMPTS - 1
             # Clear any stale stash signal from the previous attempt so
             # wait_for_stash() doesn't fire prematurely on a leftover event.
             reset_stash_event()