fix(tui): prevent false 'task crashed' errors due to race condition

cortex-tui/src/runner/event_loop.rs

@@ -3473,59 +3473,59 @@ impl EventLoop {
     /// Checks for crashed background tool tasks (panics or cancelled).
     ///
     /// This method is called periodically to detect subagent tasks that have
-    /// terminated unexpectedly without sending a completion or failure event.
+    /// terminated unexpectedly due to a panic or cancellation.
     /// When a crashed task is detected, it sends a ToolEvent::Failed to ensure
     /// the main agent always receives a response.
+    ///
+    /// IMPORTANT: We only send a Failed event if the task actually panicked or
+    /// was cancelled. If the task completed normally (Ok(())), we do NOT send
+    /// a failure event because the task already sent its own Completed/Failed
+    /// event through the channel - it just hasn't been processed yet due to
+    /// the async nature of the event loop.
     async fn check_crashed_tasks(&mut self) {
-        // Collect crashed task IDs and their errors
-        let mut crashed_tasks: Vec<(String, String)> = Vec::new();
-
-        // Check all running tool tasks
-        for (id, handle) in self.running_tool_tasks.iter() {
-            if handle.is_finished() {
-                // Task finished - check if it panicked by trying to get the result
-                // Note: We can't actually await the handle here since we don't own it,
-                // but is_finished() alone tells us the task ended unexpectedly
-                // (if it ended normally, it would have sent Completed/Failed events
-                // which would have removed it from running_tool_tasks)
-                crashed_tasks.push((
-                    id.clone(),
-                    "Subagent task terminated unexpectedly (possible panic or cancellation)"
-                        .to_string(),
-                ));
-            }
-        }
-
-        // Process crashed tasks
-        for (id, error) in crashed_tasks {
-            tracing::error!("Detected crashed subagent task: {} - {}", id, error);
+        // Collect finished task IDs
+        let finished_task_ids: Vec<String> = self
+            .running_tool_tasks
+            .iter()
+            .filter(|(_, handle)| handle.is_finished())
+            .map(|(id, _)| id.clone())
+            .collect();
 
-            // Remove from running tasks
+        // Process finished tasks - check if they actually crashed
+        for id in finished_task_ids {
             if let Some(handle) = self.running_tool_tasks.remove(&id) {
-                // Try to get the panic message if possible
-                let error_msg = match handle.await {
-                    Ok(()) => error, // Task completed but didn't send event - shouldn't happen
+                // Await the handle to check if it panicked or was cancelled
+                match handle.await {
+                    Ok(()) => {
+                        // Task completed normally - it sent its own Completed/Failed event
+                        // through the channel. Don't send another Failed event.
+                        // The event is just in transit and will be processed soon.
+                        tracing::debug!("Task {} finished normally, event pending in channel", id);
+                    }
                     Err(join_error) => {
-                        if join_error.is_panic() {
+                        // Task actually crashed - send a failure event
+                        let error_msg = if join_error.is_panic() {
                             format!("Subagent panicked: {:?}", join_error.into_panic())
                         } else if join_error.is_cancelled() {
                             "Subagent task was cancelled".to_string()
                         } else {
                             format!("Subagent task failed: {}", join_error)
-                        }
-                    }
-                };
+                        };
 
-                // Send failure event through the tool event channel
-                let _ = self
-                    .tool_event_tx
-                    .send(ToolEvent::Failed {
-                        id: id.clone(),
-                        name: "Task".to_string(),
-                        error: error_msg,
-                        duration: std::time::Duration::from_secs(0),
-                    })
-                    .await;
+                        tracing::error!("Detected crashed task: {} - {}", id, error_msg);
+
+                        // Send failure event through the tool event channel
+                        let _ = self
+                            .tool_event_tx
+                            .send(ToolEvent::Failed {
+                                id: id.clone(),
+                                name: "Task".to_string(),
+                                error: error_msg,
+                                duration: std::time::Duration::from_secs(0),
+                            })
+                            .await;
+                    }
+                }
             }
         }
     }