1 files changed, 3 insertions, 1 deletions
diff --git a/scripts/chat.py b/scripts/chat.py
index e19fb6b..5b44b64 100755
--- a/scripts/chat.py
+++ b/scripts/chat.py
@@ -78,9 +78,11 @@ def reply(thread, text):
             with open(tmp, 'w') as fh:
                 json.dump(msgs, fh, ensure_ascii=False)
             os.chmod(tmp, 0o664)
+            # replace INSIDE the lock: doing it after unlock lets a second writer read
+            # the pre-replace snapshot and rename over this message (lost update).
+            os.replace(tmp, path)
         finally:
             fcntl.flock(lock, fcntl.LOCK_UN)
-    os.replace(tmp, path)          # atomic: a poll never sees a half-written file
     return msg