fix: gateway sync race condition + hybrid session data loss — v0.50.93 (PR #714)

Fixes and extends PR #676 (yunyunyunyun-yun). Race guard in sessions.js SSE handler; prefix-equality check in routes.py _handle_session_import_cli. Closes #676.

Co-authored-by: yunyunyunyun-yun <yunyunyunyun-yun@users.noreply.github.com>

api/routes.py

@@ -2869,9 +2869,17 @@ def _handle_session_import_cli(handler, body):
 
     sid = str(body["session_id"])
 
-    # Check if already imported — idempotent
+    # Check if already imported — refresh messages from CLI store if new ones arrived
     existing = Session.load(sid)
     if existing:
+        fresh_msgs = get_cli_session_messages(sid)
+        if fresh_msgs and len(fresh_msgs) > len(existing.messages):
+            # Prefix-equality guard: only extend if existing messages are a prefix of
+            # the fresh CLI messages. Prevents silently dropping WebUI-added messages
+            # on hybrid sessions (user sent messages via WebUI while CLI continued).
+            if existing.messages == fresh_msgs[:len(existing.messages)]:
+                existing.messages = fresh_msgs
+                existing.save(touch_updated_at=False)
         return j(
             handler,
             {