Show a loading message when opening tasks from the agents overview (#45983)

## Why

Task attachment awaits server requests while the event handler cannot process scheduled frames. Prompts and chat widget replacement can also clear the terminal during loading.

## What changed

Draw a bold `Loading task…` message immediately when attaching a task, and redraw it after folder selection, trust prompts, and chat widget replacement. Schedule a frame to restore the normal view afterward.

## Testing

Extend the cold-resume test to verify that a loading message appears before server requests complete, survives widget replacement, and is replaced on the next draw.

GitOrigin-RevId: cb2e73efe38758025964aa53f52127a2b2609fca

codex-rs/tui/src/app/agents_overview.rs

@@ -8,6 +8,9 @@ pub(crate) use new::PendingWorktree;
 #[path = "agents_overview_errors.rs"]
 mod errors;
 
+#[path = "agents_overview_loading.rs"]
+mod loading;
+
 use super::agents_overview_view::AgentsOverviewGroup;
 use super::agents_overview_view::AgentsOverviewRow;
 use super::agents_overview_view::AgentsOverviewView;
@@ -332,6 +335,7 @@ impl App {
             self.chat_widget.pre_draw_tick();
             return Ok(AppRunControl::Continue);
         }
+        loading::draw(tui)?;
         if self.primary_thread_id != Some(root_thread_id) {
             let previous_displayed_thread_id = self.current_displayed_thread_id();
             if let Some(id) = previous_displayed_thread_id
@@ -456,6 +460,8 @@ impl App {
                 }
                 local_settings = crate::local_settings::LocalSettings::from(&resume_config);
             }
+            // Folder selection and trust prompts can replace or clear the loading frame.
+            loading::draw(tui)?;
             let baseline_approval = resume_config.permissions.approval_policy.value();
             let baseline_permissions =
                 RuntimePermissionProfileOverride::from_config(&resume_config);
@@ -608,6 +614,8 @@ impl App {
                 self.add_agents_overview_error(format!("Failed to attach to task: {error}"));
                 return Ok(AppRunControl::Continue);
             }
+            // Replacing the widget clears the terminal before the remaining server requests.
+            loading::draw(tui)?;
             if read_only {
                 self.ensure_thread_channel(root_thread_id)
                     .mark_external_writer();

codex-rs/tui/src/app/agents_overview_loading.rs

@@ -0,0 +1,19 @@
+//! Transient feedback while command-center selection waits for a session to load.
+//! Draw directly because the app event handler cannot process scheduled frames while awaiting.
+
+use crate::tui::Tui;
+use ratatui::style::Stylize;
+use ratatui::text::Line;
+use ratatui::widgets::Paragraph;
+
+pub(super) fn draw(tui: &mut Tui) -> std::io::Result<()> {
+    tui.draw(u16::MAX, |frame| {
+        let lines = textwrap::wrap("Loading task…", usize::from(frame.area().width.max(1)))
+            .into_iter()
+            .map(|line| Line::from(line.into_owned().bold()))
+            .collect::<Vec<_>>();
+        frame.render_widget_ref(&Paragraph::new(lines), frame.area());
+    })?;
+    tui.frame_requester().schedule_frame();
+    Ok(())
+}

codex-rs/tui/src/app/agents_overview_tests.rs

@@ -1830,8 +1830,40 @@ async fn overview_cold_resume_honors_working_directory_selection() -> Result<()>
             test_path_buf("/").abs()
         };
         let mut tui = crate::tui::test_support::make_test_tui()?;
+        // On this current-thread runtime, the server cannot answer until we yield. Cancel the
+        // pending selection to release its terminal borrow and inspect what the user sees now.
+        let mut selection =
+            Box::pin(app.select_agents_overview_thread(&mut tui, &mut app_server, thread_id));
+        assert!(futures::poll!(&mut selection).is_pending());
+        drop(selection);
+        let pending_loading =
+            crate::custom_terminal::test_support::last_rendered_buffer(&tui.terminal).clone();
         app.select_agents_overview_thread(&mut tui, &mut app_server, thread_id)
             .await?;
+        // The widget replacement clears the terminal; feedback must remain until the next draw.
+        let loading =
+            crate::custom_terminal::test_support::last_rendered_buffer(&tui.terminal).clone();
+        assert_eq!(pending_loading, loading);
+        let loading_text = loading
+            .content
+            .chunks(usize::from(loading.area.width))
+            .map(|row| {
+                row.iter()
+                    .map(ratatui::buffer::Cell::symbol)
+                    .collect::<String>()
+            })
+            .map(|line| line.trim_end().to_string())
+            .collect::<Vec<_>>()
+            .join("\n");
+        insta::allow_duplicates! {
+            insta::assert_snapshot!(loading_text.trim_end(), @"Loading task…");
+        }
+        app.handle_tui_event(&mut tui, &mut app_server, TuiEvent::Draw)
+            .await?;
+        assert_ne!(
+            crate::custom_terminal::test_support::last_rendered_buffer(&tui.terminal),
+            &loading,
+        );
         let observed = app_server
             .resume_thread(
                 &app.local_settings,