diff --git a/gateway/stream_consumer_transport.py b/gateway/stream_consumer_transport.py
index c111d322f5..773099436b 100644
--- a/gateway/stream_consumer_transport.py
+++ b/gateway/stream_consumer_transport.py
@@ -334,10 +334,13 @@ class StreamTransportMixin:
         # A segment-break finalize never carries the cursor, so gate it too or a 1-2 token
         # preamble lands durably at every tool boundary and resets the progress anchor
         # (#99026).  Turn finals are exempt: a short complete answer must be delivered.
+        # Tradeoff: on non-cumulative transports the held preamble is DROPPED, not
+        # carried — _end_segment sees update_visible=True and resets the segment.
         preamble_finalize = finalize and not is_turn_final
         if (self._message_id is None and len(visible_stripped) < self._MIN_NEW_MSG_CHARS
                 and (preamble_finalize or (self.cfg.cursor and self.cfg.cursor in text))):
-            return True  # too short for a standalone message — accumulate more
+            # Mid-stream: accumulate more.  Segment-break finalize: dropped (see above).
+            return True
 
         # A failed native/draft transport disables itself and falls through so the
         # accumulated text still reaches the user via edit/send.