fix(gateway): edit streamed message instead of sending duplicate when response_transformed

When a transform_llm_output hook appends content after streaming, the previous
fix skipped the final-send suppression which caused the full response to be
sent as a NEW message (duplicate). Instead, edit the existing streamed message
in-place to append the transformed content, then set already_sent=True.

Added stream_consumer.message_id and .accumulated_text public properties.

gateway/run.py

@@ -17692,6 +17692,28 @@ class GatewayRunner:
                     _content_delivered,
                 )
                 response["already_sent"] = True
+            elif not _is_empty_sentinel and _transformed and _sc is not None:
+                # Plugin hooks transformed the response after streaming — edit the
+                # existing streamed message instead of sending a duplicate.
+                _sc_msg_id = _sc.message_id
+                if _sc_msg_id:
+                    try:
+                        await _sc.adapter.edit_message(
+                            chat_id=source.chat_id,
+                            message_id=_sc_msg_id,
+                            content=response["final_response"],
+                            finalize=True,
+                        )
+                        response["already_sent"] = True
+                        logger.info(
+                            "Edited streamed message %s for session %s to include plugin-transformed content.",
+                            _sc_msg_id, session_key or "?",
+                        )
+                    except Exception as _edit_err:
+                        logger.warning(
+                            "Failed to edit streamed message for session %s: %s",
+                            session_key or "?", _edit_err,
+                        )
 
         # Schedule deletion of tracked temporary progress bubbles after the
         # final response lands. Failed runs skip this so bubbles remain as

gateway/stream_consumer.py

@@ -192,6 +192,16 @@ class GatewayStreamConsumer:
         """True when the stream consumer delivered the final assistant reply."""
         return self._final_response_sent
 
+    @property
+    def message_id(self) -> str | None:
+        """The Discord/chat message ID of the last-sent or edited message."""
+        return self._message_id
+
+    @property
+    def accumulated_text(self) -> str:
+        """The accumulated streamed text (without think-block content)."""
+        return self._accumulated
+
     @property
     def final_content_delivered(self) -> bool:
         """True when the final response content reached the user, even if