fix(gateway): prevent duplicate final send when only cosmetic edit failed

When the stream consumer's got_done handler successfully delivers the
final response content via _send_or_edit but the subsequent edit
(e.g. cursor removal) fails, final_response_sent remains False even
though the user has already received the final answer. The gateway's
fallback send path then re-delivers the same content, causing the
user to see the response twice on Telegram.

Introduce a new _final_content_delivered flag on the stream consumer,
set by the got_done handler when the final content has reached the
user. The _run_agent suppression logic now treats this flag as an
additional signal (alongside final_response_sent and
response_previewed) that final delivery is already complete.

This preserves the existing behavior for intermediate-text-only
streams (where already_sent=True but no final content has been
delivered) — those still receive the gateway's fallback send, matching
the test expectation in test_partial_stream_output_does_not_set_already_sent.

Adds TestFinalContentDeliveredSuppression with two cases covering
both the suppression (content delivered + edit failed) and the
non-suppression (intermediate text only) branches.

gateway/run.py

@@ -16131,6 +16131,7 @@ class GatewayRunner:
                     _already_streamed = bool(
                         (_sc and getattr(_sc, "final_response_sent", False))
                         or _previewed
+                        or (_sc and getattr(_sc, "final_content_delivered", False))
                     )
                     first_response = result.get("final_response", "")
                     if first_response and not _already_streamed:
@@ -16292,12 +16293,16 @@ class GatewayRunner:
             # response_previewed means the interim_assistant_callback already
             # sent the final text via the adapter (non-streaming path).
             _previewed = bool(response.get("response_previewed"))
-            if not _is_empty_sentinel and (_streamed or _previewed):
+            _content_delivered = bool(
+                _sc and getattr(_sc, "final_content_delivered", False)
+            )
+            if not _is_empty_sentinel and (_streamed or _previewed or _content_delivered):
                 logger.info(
-                    "Suppressing normal final send for session %s: final delivery already confirmed (streamed=%s previewed=%s).",
+                    "Suppressing normal final send for session %s: final delivery already confirmed (streamed=%s previewed=%s content_delivered=%s).",
                     session_key or "?",
                     _streamed,
                     _previewed,
+                    _content_delivered,
                 )
                 response["already_sent"] = True
 

gateway/stream_consumer.py

@@ -150,6 +150,10 @@ class GatewayStreamConsumer:
         self._flood_strikes = 0         # Consecutive flood-control edit failures
         self._current_edit_interval = self.cfg.edit_interval  # Adaptive backoff
         self._final_response_sent = False
+        # Set when the final response content was sent to the user via
+        # streaming, even if the final edit (cursor removal etc.)
+        # subsequently failed.
+        self._final_content_delivered = False
         # Cache adapter lifecycle capability: only platforms that need an
         # explicit finalize call (e.g. DingTalk AI Cards) force us to make
         # a redundant final edit.  Everyone else keeps the fast path.
@@ -187,6 +191,12 @@ class GatewayStreamConsumer:
         """True when the stream consumer delivered the final assistant reply."""
         return self._final_response_sent
 
+    @property
+    def final_content_delivered(self) -> bool:
+        """True when the final response content reached the user, even if
+        the subsequent cosmetic edit (cursor removal) failed."""
+        return self._final_content_delivered
+
     def on_segment_break(self) -> None:
         """Finalize the current stream segment and start a fresh message."""
         self._queue.put(_NEW_SEGMENT)
@@ -455,6 +465,8 @@ class GatewayStreamConsumer:
                             # tool-progress edits or fallback-mode promotion (#10748)
                             # — that doesn't mean the final answer reached the user.
                             self._final_response_sent = chunks_delivered
+                            if chunks_delivered:
+                                self._final_content_delivered = True
                             return
                         if got_segment_break:
                             self._message_id = None
@@ -505,6 +517,11 @@ class GatewayStreamConsumer:
                     self._last_edit_time = time.monotonic()
 
                 if got_done:
+                    # Record that the final content reached the user even
+                    # if the cosmetic final edit below fails.
+                    if current_update_visible and self._accumulated:
+                        self._final_content_delivered = True
+
                     # Final edit without cursor. If progressive editing failed
                     # mid-stream, send a single continuation/fallback message
                     # here instead of letting the base gateway path send the