Prevent Esc from dismissing or rewinding /side (#22710)

Addresses #22599

## Why
`/side` currently lets `Esc` return to the parent thread. Multiple users
reported that this collides with queued-steer UI that also advertises
`Esc`, so a timing-sensitive keypress can dismiss an ephemeral side chat
instead of sending the queued prompt.

After removing that dismissal shortcut, the same `Esc` path could fall
through to main-thread backtrack/edit-previous handling, which is not
valid for ephemeral side conversations. This keeps `/side` out of both
global `Esc` behaviors.

## What changed
- Remove `Esc` from the `/side` return shortcut matcher while keeping
the existing `Ctrl+C` and `Ctrl+D` behavior.
- Update side-conversation hints and blocked-command copy to advertise
`Ctrl+C` as the return shortcut.
- Rename the reserved `Esc` keymap label to describe backtracking only.
- Block backtrack/edit-previous handling while a side conversation is
active and report `Editing previous prompts is unavailable in side
conversations.` when that path would have fired.
- Keep composer-owned `Esc` behavior, such as Vim insert-mode escape,
routed locally.
- Refresh focused shortcut assertions and TUI snapshots for the updated
footer and new side-conversation error message.

## Verification
Manually tested `/side` use cases and `Esc`, `Ctrl+C`, `Ctrl+D`.

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

@@ -5,6 +5,9 @@
 
 use super::*;
 
+const SIDE_EDIT_PREVIOUS_UNAVAILABLE_MESSAGE: &str =
+    "Editing previous prompts is unavailable in side conversations.";
+
 impl App {
     pub(super) async fn launch_external_editor(&mut self, tui: &mut tui::Tui) {
         let editor_cmd = match external_editor::resolve_editor_command() {
@@ -197,6 +200,8 @@ impl App {
             // handles it.
             if self.should_handle_backtrack_esc(key_event) {
                 self.handle_backtrack_esc_key(tui);
+            } else if self.should_reject_side_backtrack_esc(key_event) {
+                self.reject_side_backtrack_esc();
             } else {
                 self.chat_widget.handle_key_event(key_event);
             }
@@ -252,11 +257,25 @@ impl App {
     }
 
     pub(super) fn should_handle_backtrack_esc(&self, key_event: KeyEvent) -> bool {
-        self.chat_widget.is_normal_backtrack_mode()
+        !self.chat_widget.side_conversation_active()
+            && self.chat_widget.is_normal_backtrack_mode()
             && self.chat_widget.composer_is_empty()
             && !self.chat_widget.should_handle_vim_insert_escape(key_event)
     }
 
+    pub(super) fn should_reject_side_backtrack_esc(&self, key_event: KeyEvent) -> bool {
+        self.chat_widget.side_conversation_active()
+            && self.chat_widget.is_normal_backtrack_mode()
+            && self.chat_widget.composer_is_empty()
+            && !self.chat_widget.should_handle_vim_insert_escape(key_event)
+    }
+
+    pub(super) fn reject_side_backtrack_esc(&mut self) {
+        self.reset_backtrack_state();
+        self.chat_widget
+            .add_error_message(SIDE_EDIT_PREVIOUS_UNAVAILABLE_MESSAGE.to_string());
+    }
+
     fn app_keymap_shortcuts_available(&self) -> bool {
         self.overlay.is_none() && self.chat_widget.no_modal_or_popup_active()
     }

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

@@ -54,24 +54,16 @@ fn send_world_writable_scan_failed(tx: &AppEventSender) {
 }
 
 pub(super) fn side_return_shortcut_matches(key_event: KeyEvent) -> bool {
-    match key_event {
-        KeyEvent {
-            code: KeyCode::Esc,
-            kind: KeyEventKind::Press | KeyEventKind::Repeat,
-            ..
-        } => true,
+    matches!(
+        key_event,
         KeyEvent {
             code: KeyCode::Char(c),
             modifiers,
             kind: KeyEventKind::Press,
             ..
         } if modifiers.contains(KeyModifiers::CONTROL)
-            && (c.eq_ignore_ascii_case(&'c') || c.eq_ignore_ascii_case(&'d')) =>
-        {
-            true
-        }
-        _ => false,
-    }
+            && (c.eq_ignore_ascii_case(&'c') || c.eq_ignore_ascii_case(&'d'))
+    )
 }
 
 #[cfg(test)]
@@ -79,16 +71,7 @@ mod tests {
     use super::*;
 
     #[test]
-    fn side_return_shortcuts_match_esc_ctrl_c_and_ctrl_d() {
-        assert!(side_return_shortcut_matches(KeyEvent::new(
-            KeyCode::Esc,
-            KeyModifiers::NONE,
-        )));
-        assert!(side_return_shortcut_matches(KeyEvent::new_with_kind(
-            KeyCode::Esc,
-            KeyModifiers::NONE,
-            KeyEventKind::Repeat,
-        )));
+    fn side_return_shortcuts_match_ctrl_c_and_ctrl_d() {
         assert!(side_return_shortcut_matches(KeyEvent::new(
             KeyCode::Char('c'),
             KeyModifiers::CONTROL,
@@ -105,6 +88,11 @@ mod tests {
             KeyCode::Char('D'),
             KeyModifiers::CONTROL,
         )));
+        assert!(!side_return_shortcut_matches(KeyEvent::new_with_kind(
+            KeyCode::Esc,
+            KeyModifiers::NONE,
+            KeyEventKind::Press,
+        )));
         assert!(!side_return_shortcut_matches(KeyEvent::new_with_kind(
             KeyCode::Esc,
             KeyModifiers::NONE,

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

@@ -20,7 +20,7 @@ const SIDE_NO_STARTED_CONVERSATION_MESSAGE: &str = concat!(
     "Send a message first, then try /side again."
 );
 const SIDE_ALREADY_OPEN_MESSAGE: &str =
-    "A side conversation is already open. Press Esc to return before starting another.";
+    "A side conversation is already open. Press Ctrl+C to return before starting another.";
 const SIDE_BOUNDARY_PROMPT: &str = r#"Side conversation boundary.
 
 Everything before this boundary is inherited history from the parent thread. It is reference context only. It is not your current task.
@@ -247,7 +247,7 @@ impl App {
         if let Some(parent_status) = parent_status {
             label_parts.push(parent_status.label(parent_is_main).to_string());
         }
-        label_parts.push("Esc to return".to_string());
+        label_parts.push("Ctrl+C to return".to_string());
         self.chat_widget
             .set_side_conversation_context_label(Some(format!("Side {}", label_parts.join(" · "))));
     }

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

@@ -3169,7 +3169,9 @@ async fn side_start_block_message_tracks_open_side_conversation() {
 
     assert_eq!(
         app.side_start_block_message(),
-        Some("A side conversation is already open. Press Esc to return before starting another.")
+        Some(
+            "A side conversation is already open. Press Ctrl+C to return before starting another."
+        )
     );
 
     app.side_threads.remove(&side_thread_id);
@@ -5248,3 +5250,50 @@ async fn backtrack_esc_does_not_steal_empty_vim_insert_escape() {
     assert!(!app.chat_widget.should_handle_vim_insert_escape(esc));
     assert!(app.should_handle_backtrack_esc(esc));
 }
+
+#[tokio::test]
+async fn side_conversations_reject_backtrack_esc_without_stealing_vim_insert_escape() {
+    let mut app = make_test_app().await;
+    let esc = crossterm::event::KeyEvent::new(crossterm::event::KeyCode::Esc, KeyModifiers::NONE);
+
+    app.chat_widget
+        .set_side_conversation_active(/*active*/ true);
+    assert!(app.chat_widget.composer_is_empty());
+    assert!(!app.should_handle_backtrack_esc(esc));
+    assert!(app.should_reject_side_backtrack_esc(esc));
+
+    app.chat_widget.toggle_vim_mode_and_notify();
+    app.chat_widget
+        .handle_key_event(crossterm::event::KeyEvent::new(
+            crossterm::event::KeyCode::Char('i'),
+            KeyModifiers::NONE,
+        ));
+
+    assert!(app.chat_widget.should_handle_vim_insert_escape(esc));
+    assert!(!app.should_handle_backtrack_esc(esc));
+    assert!(!app.should_reject_side_backtrack_esc(esc));
+}
+
+#[tokio::test]
+async fn side_backtrack_rejection_reports_unavailable_message_snapshot() {
+    let (mut app, mut app_event_rx, _op_rx) = make_test_app_with_channels().await;
+    app.backtrack.primed = true;
+
+    app.reject_side_backtrack_esc();
+
+    assert!(!app.backtrack.primed);
+    let cell = match app_event_rx.try_recv() {
+        Ok(AppEvent::InsertHistoryCell(cell)) => cell,
+        other => panic!("expected InsertHistoryCell event, got {other:?}"),
+    };
+    let rendered = cell
+        .display_lines(/*width*/ 80)
+        .into_iter()
+        .map(|line| line.to_string())
+        .collect::<Vec<_>>()
+        .join("\n");
+    assert_app_snapshot!(
+        "side_backtrack_rejection_reports_unavailable_message",
+        rendered
+    );
+}

codex-rs/tui/src/chatwidget/side.rs

@@ -25,6 +25,10 @@ impl ChatWidget {
         self.bottom_pane.set_side_conversation_active(active);
     }
 
+    pub(crate) fn side_conversation_active(&self) -> bool {
+        self.active_side_conversation
+    }
+
     pub(crate) fn set_side_conversation_context_label(&mut self, label: Option<String>) {
         self.bottom_pane.set_side_conversation_context_label(label);
     }

codex-rs/tui/src/chatwidget/slash_dispatch.rs

@@ -32,7 +32,8 @@ struct PreparedSlashCommandArgs {
 const SIDE_STARTING_CONTEXT_LABEL: &str = "Side starting...";
 const SIDE_REVIEW_UNAVAILABLE_MESSAGE: &str =
     "'/side' is unavailable while code review is running.";
-const SIDE_SLASH_COMMAND_UNAVAILABLE_HINT: &str = "Press Esc to return to the main thread first.";
+const SIDE_SLASH_COMMAND_UNAVAILABLE_HINT: &str =
+    "Press Ctrl+C to return to the main thread first.";
 const GOAL_USAGE: &str = "Usage: /goal <objective>";
 const GOAL_USAGE_HINT: &str = "Example: /goal improve benchmark coverage";
 const RAW_USAGE: &str = "Usage: /raw [on|off]";

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__side_context_label_preserves_status_line.snap

@@ -6,4 +6,4 @@ expression: terminal.backend()
 "                                                                                "
 "› Check recently modified functions for compatibility                           "
 "                                                                                "
-"  gpt-5.5                                Side from main thread · Esc to return  "
+"  gpt-5.5                             Side from main thread · Ctrl+C to return  "

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__side_context_label_shows_parent_status.snap

@@ -6,4 +6,4 @@ expression: terminal.backend()
 "                                                                                "
 "› Check recently modified functions for compatibility                           "
 "                                                                                "
-"  gpt-5.5 default · … Side from main thread · main needs input · Esc to return  "
+"  gpt-5.5 default… Side from main thread · main needs input · Ctrl+C to return  "

codex-rs/tui/src/chatwidget/tests/side.rs

@@ -106,7 +106,7 @@ async fn slash_commands_without_side_flag_are_rejected_for_side_threads() {
             let rendered = lines_to_single_string(&cell.display_lines(/*width*/ 80));
             assert!(
                 rendered.contains(
-                    "'/review' is unavailable in side conversations. Press Esc to return to the main thread first."
+                    "'/review' is unavailable in side conversations. Press Ctrl+C to return to the main thread first."
                 ),
                 "expected side conversation slash command error, got {rendered:?}"
             );
@@ -132,7 +132,7 @@ async fn slash_side_is_rejected_for_side_threads() {
             let rendered = lines_to_single_string(&cell.display_lines(/*width*/ 80));
             assert!(
                 rendered.contains(
-                    "'/side' is unavailable in side conversations. Press Esc to return to the main thread first."
+                    "'/side' is unavailable in side conversations. Press Ctrl+C to return to the main thread first."
                 ),
                 "expected side conversation slash command error, got {rendered:?}"
             );
@@ -276,7 +276,7 @@ async fn side_context_label_preserves_status_line_snapshot() {
     chat.refresh_status_line();
     chat.set_side_conversation_active(/*active*/ true);
     chat.set_side_conversation_context_label(Some(
-        "Side from main thread · Esc to return".to_string(),
+        "Side from main thread · Ctrl+C to return".to_string(),
     ));
 
     let width = 80;
@@ -297,7 +297,7 @@ async fn side_context_label_shows_parent_status_snapshot() {
     chat.show_welcome_banner = false;
     chat.set_side_conversation_active(/*active*/ true);
     chat.set_side_conversation_context_label(Some(
-        "Side from main thread · main needs input · Esc to return".to_string(),
+        "Side from main thread · main needs input · Ctrl+C to return".to_string(),
     ));
 
     let width = 80;

codex-rs/tui/src/keymap.rs

@@ -1445,10 +1445,7 @@ const MAIN_RESERVED_BINDINGS: &[(&str, KeyBinding)] = &[
         "fixed.cycle_collaboration_mode",
         key_hint::shift(KeyCode::Tab),
     ),
-    (
-        "fixed.return_from_side_or_backtrack",
-        key_hint::plain(KeyCode::Esc),
-    ),
+    ("fixed.backtrack", key_hint::plain(KeyCode::Esc)),
     ("fixed.previous_agent", key_hint::alt(KeyCode::Left)),
     ("fixed.next_agent", key_hint::alt(KeyCode::Right)),
     ("fixed.slash_command", key_hint::plain(KeyCode::Char('/'))),

codex-rs/tui/src/snapshots/codex_tui__app__tests__side_backtrack_rejection_reports_unavailable_message.snap

@@ -0,0 +1,5 @@
+---
+source: tui/src/app/tests.rs
+expression: rendered
+---
+■ Editing previous prompts is unavailable in side conversations.