fix: prevent message duplication in ProjectMCPServer and handle_call_tool (#8918)

* Updated the message processing logic in both ProjectMCPServer and handle_call_tool to ensure that duplicate messages are not added to the collected results.
* Introduced a helper function to manage the addition of results, enhancing code clarity and maintainability.

Co-authored-by: Cristhian Zanforlin Lousa <cristhian.lousa@gmail.com>

src/backend/base/langflow/api/v1/mcp.py

@@ -251,10 +251,7 @@ async def handle_call_tool(name: str, arguments: dict) -> list[types.TextContent
             input_value=processed_inputs.get("input_value", ""), session_id=conversation_id
         )
 
-        async def send_progress_updates():
+        async def send_progress_updates(progress_token):
-            if not (mcp_config.enable_progress_notifications and server.request_context.meta.progressToken):
-                return
-
             try:
                 progress = 0.0
                 while True:
@@ -274,7 +271,7 @@ async def handle_call_tool(name: str, arguments: dict) -> list[types.TextContent
         try:
             progress_task = None
             if mcp_config.enable_progress_notifications and server.request_context.meta.progressToken:
-                progress_task = asyncio.create_task(send_progress_updates())
+                progress_task = asyncio.create_task(send_progress_updates(server.request_context.meta.progressToken))
 
             try:
                 try:
@@ -284,20 +281,25 @@ async def handle_call_tool(name: str, arguments: dict) -> list[types.TextContent
                         stream=False,
                         api_key_user=current_user,
                     )
-                    # Process all outputs and messages
+                    # Process all outputs and messages, ensuring no duplicates
+                    processed_texts = set()
+
+                    def add_result(text: str):
+                        if text not in processed_texts:
+                            processed_texts.add(text)
+                            collected_results.append(types.TextContent(type="text", text=text))
+
                     for run_output in result.outputs:
                         for component_output in run_output.outputs:
                             # Handle messages
                             for msg in component_output.messages or []:
-                                text_content = types.TextContent(type="text", text=msg.message)
+                                add_result(msg.message)
-                                collected_results.append(text_content)
                             # Handle results
                             for value in (component_output.results or {}).values():
                                 if isinstance(value, Message):
-                                    text_content = types.TextContent(type="text", text=value.get_text())
+                                    add_result(value.get_text())
-                                    collected_results.append(text_content)
                                 else:
-                                    collected_results.append(types.TextContent(type="text", text=str(value)))
+                                    add_result(str(value))
                 except Exception as e:  # noqa: BLE001
                     error_msg = f"Error Executing the {flow.name} tool. Error: {e!s}"
                     collected_results.append(types.TextContent(type="text", text=error_msg))
@@ -306,9 +308,7 @@ async def handle_call_tool(name: str, arguments: dict) -> list[types.TextContent
             finally:
                 if progress_task:
                     progress_task.cancel()
-                    await asyncio.wait([progress_task])
+                    await asyncio.gather(progress_task, return_exceptions=True)
-                    if not progress_task.cancelled() and (exc := progress_task.exception()) is not None:
-                        raise exc
 
         except Exception:
             if mcp_config.enable_progress_notifications and (

src/backend/base/langflow/api/v1/mcp_projects.py

@@ -838,20 +838,25 @@ class ProjectMCPServer:
                                 stream=False,
                                 api_key_user=current_user,
                             )
-                            # Process all outputs and messages
+                            # Process all outputs and messages, ensuring no duplicates
+                            processed_texts = set()
+
+                            def add_result(text: str):
+                                if text not in processed_texts:
+                                    processed_texts.add(text)
+                                    collected_results.append(types.TextContent(type="text", text=text))
+
                             for run_output in result.outputs:
                                 for component_output in run_output.outputs:
                                     # Handle messages
                                     for msg in component_output.messages or []:
-                                        text_content = types.TextContent(type="text", text=msg.message)
+                                        add_result(msg.message)
-                                        collected_results.append(text_content)
                                     # Handle results
                                     for value in (component_output.results or {}).values():
                                         if isinstance(value, Message):
-                                            text_content = types.TextContent(type="text", text=value.get_text())
+                                            add_result(value.get_text())
-                                            collected_results.append(text_content)
                                         else:
-                                            collected_results.append(types.TextContent(type="text", text=str(value)))
+                                            add_result(str(value))
                         except Exception as e:  # noqa: BLE001
                             error_msg = f"Error Executing the {flow.name} tool. Error: {e!s}"
                             collected_results.append(types.TextContent(type="text", text=error_msg))