fix(tui): display error message when subagent crashes

cortex-tui/src/app.rs

@@ -272,6 +272,9 @@ pub struct SubagentTaskDisplay {
     pub started_at: Instant,
     /// Current todo items from the subagent (if any).
     pub todos: Vec<SubagentTodoItem>,
+    /// Error message if the subagent failed.
+    /// Stored separately so it can be displayed even when the task is removed.
+    pub error_message: Option<String>,
 }
 
 impl SubagentTaskDisplay {
@@ -294,6 +297,7 @@ impl SubagentTaskDisplay {
             output_preview: String::new(),
             started_at: Instant::now(),
             todos: Vec::new(),
+            error_message: None,
         }
     }
 

cortex-tui/src/runner/event_loop.rs

@@ -3419,12 +3419,23 @@ impl EventLoop {
                     format!("Error: {}", error),
                 );
 
-                // If this is a Task tool, remove the subagent from display
+                // If this is a Task tool, update subagent status to Failed with error message
+                // Keep the subagent visible so users can see what error occurred
                 if name == "Task" || name == "task" {
                     let session_id = format!("subagent_{}", id);
-                    self.app_state.remove_subagent(&session_id);
-                    // Stop delegation mode if no more active subagents
-                    if !self.app_state.has_active_subagents() {
+                    let error_clone = error.clone();
+                    self.app_state.update_subagent(&session_id, |task| {
+                        task.status = SubagentDisplayStatus::Failed;
+                        task.error_message = Some(error_clone);
+                        task.current_activity = "Failed".to_string();
+                    });
+                    // Stop delegation mode if no more active (non-failed) subagents
+                    let has_running_subagents = self
+                        .app_state
+                        .active_subagents
+                        .iter()
+                        .any(|t| !t.status.is_terminal());
+                    if !has_running_subagents {
                         self.app_state.streaming.stop_delegation();
                     }
                 }

cortex-tui/src/views/minimal_session.rs

@@ -413,8 +413,35 @@ impl<'a> MinimalSessionView<'a> {
             ),
         ]));
 
-        // Display todos if any - use ⎿ prefix for first, space for rest
-        if !task.todos.is_empty() {
+        // Display error message if task failed
+        if task.status == SubagentDisplayStatus::Failed {
+            if let Some(ref error_msg) = task.error_message {
+                lines.push(Line::from(vec![
+                    Span::styled("  ⎿ ", Style::default().fg(self.colors.text_muted)),
+                    Span::styled("Error: ", Style::default().fg(self.colors.error)),
+                ]));
+                // Display error message, truncate if too long
+                for (i, err_line) in error_msg.lines().take(5).enumerate() {
+                    let truncated = if err_line.len() > 70 {
+                        format!("{}...", &err_line.chars().take(67).collect::<String>())
+                    } else {
+                        err_line.to_string()
+                    };
+                    let prefix = if i == 0 { "    " } else { "    " };
+                    lines.push(Line::from(vec![
+                        Span::styled(prefix, Style::default().fg(self.colors.text_muted)),
+                        Span::styled(truncated, Style::default().fg(self.colors.error)),
+                    ]));
+                }
+            } else {
+                // Fallback: no error message provided
+                lines.push(Line::from(vec![
+                    Span::styled("  ⎿ ", Style::default().fg(self.colors.text_muted)),
+                    Span::styled("Task failed", Style::default().fg(self.colors.error)),
+                ]));
+            }
+        } else if !task.todos.is_empty() {
+            // Display todos if any - use ⎿ prefix for first, space for rest
             for (i, todo) in task.todos.iter().enumerate() {
                 let (status_text, status_color) = match todo.status {
                     SubagentTodoStatus::Completed => ("[completed]", self.colors.success),