tui: double-press Ctrl+C/Ctrl+D to quit (#8936)

## Problem

Codex’s TUI quit behavior has historically been easy to trigger
accidentally and hard to reason
about.

- `Ctrl+C`/`Ctrl+D` could terminate the UI immediately, which is a
common key to press while trying
  to dismiss a modal, cancel a command, or recover from a stuck state.
- “Quit” and “shutdown” were not consistently separated, so some exit
paths could bypass the
  shutdown/cleanup work that should run before the process terminates.

This PR makes quitting both safer (harder to do by accident) and more
uniform across quit
gestures, while keeping the shutdown-first semantics explicit.

## Mental model

After this change, the system treats quitting as a UI request that is
coordinated by the app
layer.

- The UI requests exit via `AppEvent::Exit(ExitMode)`.
- `ExitMode::ShutdownFirst` is the normal user path: the app triggers
`Op::Shutdown`, continues
rendering while shutdown runs, and only ends the UI loop once shutdown
has completed.
- `ExitMode::Immediate` exists as an escape hatch (and as the
post-shutdown “now actually exit”
signal); it bypasses cleanup and should not be the default for
user-triggered quits.

User-facing quit gestures are intentionally “two-step” for safety:

- `Ctrl+C` and `Ctrl+D` no longer exit immediately.
- The first press arms a 1-second window and shows a footer hint (“ctrl
+ <key> again to quit”).
- Pressing the same key again within the window requests a
shutdown-first quit; otherwise the
  hint expires and the next press starts a fresh window.

Key routing remains modal-first:

- A modal/popup gets first chance to consume `Ctrl+C`.
- If a modal handles `Ctrl+C`, any armed quit shortcut is cleared so
dismissing a modal cannot
  prime a subsequent `Ctrl+C` to quit.
- `Ctrl+D` only participates in quitting when the composer is empty and
no modal/popup is active.

The design doc `docs/exit-confirmation-prompt-design.md` captures the
intended routing and the
invariants the UI should maintain.

## Non-goals

- This does not attempt to redesign modal UX or make modals uniformly
dismissible via `Ctrl+C`.
It only ensures modals get priority and that quit arming does not leak
across modal handling.
- This does not introduce a persistent confirmation prompt/menu for
quitting; the goal is to keep
  the exit gesture lightweight and consistent.
- This does not change the semantics of core shutdown itself; it changes
how the UI requests and
  sequences it.

## Tradeoffs

- Quitting via `Ctrl+C`/`Ctrl+D` now requires a deliberate second
keypress, which adds friction for
  users who relied on the old “instant quit” behavior.
- The UI now maintains a small time-bounded state machine for the armed
shortcut, which increases
  complexity and introduces timing-dependent behavior.

This design was chosen over alternatives (a modal confirmation prompt or
a long-lived “are you
sure” state) because it provides an explicit safety barrier while
keeping the flow fast and
keyboard-native.

## Architecture

- `ChatWidget` owns the quit-shortcut state machine and decides when a
quit gesture is allowed
  (idle vs cancellable work, composer state, etc.).
- `BottomPane` owns rendering and local input routing for modals/popups.
It is responsible for
consuming cancellation keys when a view is active and for
showing/expiring the footer hint.
- `App` owns shutdown sequencing: translating
`AppEvent::Exit(ShutdownFirst)` into `Op::Shutdown`
  and only terminating the UI loop when exit is safe.

This keeps “what should happen” decisions (quit vs interrupt vs ignore)
in the chat/widget layer,
while keeping “how it looks and which view gets the key” in the
bottom-pane layer.

## Observability

You can tell this is working by running the TUIs and exercising the quit
gestures:

- While idle: pressing `Ctrl+C` (or `Ctrl+D` with an empty composer and
no modal) shows a footer
hint for ~1 second; pressing again within that window exits via
shutdown-first.
- While streaming/tools/review are active: `Ctrl+C` interrupts work
rather than quitting.
- With a modal/popup open: `Ctrl+C` dismisses/handles the modal (if it
chooses to) and does not
arm a quit shortcut; a subsequent quick `Ctrl+C` should not quit unless
the user re-arms it.

Failure modes are visible as:

- Quits that happen immediately (no hint window) from `Ctrl+C`/`Ctrl+D`.
- Quits that occur while a modal is open and consuming `Ctrl+C`.
- UI termination before shutdown completes (cleanup skipped).

## Tests

- Updated/added unit and snapshot coverage in `codex-tui` and
`codex-tui2` to validate:
  - The quit hint appears and expires on the expected key.
- Double-press within the window triggers a shutdown-first quit request.
- Modal-first routing prevents quit bypass and clears any armed shortcut
when a modal consumes
    `Ctrl+C`.

These tests focus on the UI-level invariants and rendered output; they
do not attempt to validate
real terminal key-repeat timing or end-to-end process shutdown behavior.

---
Screenshot:
<img width="912" height="740" alt="Screenshot 2026-01-13 at 1 05 28 PM"
src="https://github.com/user-attachments/assets/18f3d22e-2557-47f2-a369-ae7a9531f29f"
/>

docs/config.md

@@ -21,3 +21,9 @@ Codex can run a notification hook when the agent finishes a turn. See the config
 ## JSON Schema
 
 The generated JSON Schema for `config.toml` lives at `codex-rs/core/config.schema.json`.
+
+## Notices
+
+Codex stores "do not show again" flags for some UI prompts under the `[notice]` table.
+
+Ctrl+C/Ctrl+D quitting uses a ~1 second double-press hint (`ctrl + c again to quit`).

docs/exit-confirmation-prompt-design.md

@@ -0,0 +1,96 @@
+# Exit and shutdown flow (tui + tui2)
+
+This document describes how exit, shutdown, and interruption work in the Rust TUIs (`codex-rs/tui`
+and `codex-rs/tui2`). It is intended for Codex developers and Codex itself when reasoning about
+future exit/shutdown changes.
+
+This doc replaces earlier separate history and design notes. High-level history is summarized
+below; full details are captured in PR #8936.
+
+## Terms
+
+- **Exit**: end the UI event loop and terminate the process.
+- **Shutdown**: request a graceful agent/core shutdown (`Op::Shutdown`) and wait for
+  `ShutdownComplete` so cleanup can run.
+- **Interrupt**: cancel a running operation (`Op::Interrupt`).
+
+## Event model (AppEvent)
+
+Exit is coordinated via a single event with explicit modes:
+
+- `AppEvent::Exit(ExitMode::ShutdownFirst)`
+  - Prefer this for user-initiated quits so cleanup runs.
+- `AppEvent::Exit(ExitMode::Immediate)`
+  - Escape hatch for immediate exit. This bypasses shutdown and can drop
+    in-flight work (e.g., tasks, rollout flush, child process cleanup).
+
+`App` is the coordinator: it submits `Op::Shutdown` and it exits the UI loop only when
+`ExitMode::Immediate` arrives (typically after `ShutdownComplete`).
+
+## User-triggered quit flows
+
+### Ctrl+C
+
+Priority order in the UI layer:
+
+1. Active modal/view gets the first chance to consume (`BottomPane::on_ctrl_c`).
+   - If the modal handles it, the quit flow stops.
+   - When a modal/popup handles Ctrl+C, the quit shortcut is cleared so dismissing a modal cannot
+     accidentally prime a subsequent Ctrl+C to quit.
+2. If the user has already armed Ctrl+C and the 1 second window has not expired, the second Ctrl+C
+   triggers shutdown-first quit immediately.
+3. Otherwise, `ChatWidget` arms Ctrl+C and shows the quit hint (`ctrl + c again to quit`) for
+   1 second.
+4. If cancellable work is active (streaming/tools/review), `ChatWidget` submits `Op::Interrupt`.
+
+### Ctrl+D
+
+- Only participates in quit when the composer is empty **and** no modal is active.
+  - On first press, show the quit hint (same as Ctrl+C) and start the 1 second timer.
+  - If pressed again while the hint is visible, request shutdown-first quit.
+- With any modal/popup open, key events are routed to the view and Ctrl+D does not attempt to
+  quit.
+
+### Slash commands
+
+- `/quit`, `/exit`, `/logout` request shutdown-first quit **without** a prompt,
+  because slash commands are harder to trigger accidentally and imply clear intent to quit.
+
+### /new
+
+- Uses shutdown without exit (suppresses `ShutdownComplete`) so the app can
+  start a fresh session without terminating.
+
+## Shutdown completion and suppression
+
+`ShutdownComplete` is the signal that core cleanup has finished. The UI treats it as the boundary
+for exit:
+
+- `ChatWidget` requests `Exit(Immediate)` on `ShutdownComplete`.
+- `App` can suppress a single `ShutdownComplete` when shutdown is used as a
+  cleanup step (e.g., `/new`).
+
+## Edge cases and invariants
+
+- **Review mode** counts as cancellable work. Ctrl+C should interrupt review, not
+  quit.
+- **Modal open** means Ctrl+C/Ctrl+D should not quit unless the modal explicitly
+  declines to handle Ctrl+C.
+- **Immediate exit** is not a normal user path; it is a fallback for shutdown
+  completion or an emergency exit. Use it sparingly because it skips cleanup.
+
+## Testing expectations
+
+At a minimum, we want coverage for:
+
+- Ctrl+C while working interrupts, does not quit.
+- Ctrl+C while idle and empty shows quit hint, then shutdown-first quit on second press.
+- Ctrl+D with modal open does not quit.
+- `/quit` / `/exit` / `/logout` quit without prompt, but still shutdown-first.
+  - Ctrl+D while idle and empty shows quit hint, then shutdown-first quit on second press.
+
+## History (high level)
+
+Codex has historically mixed "exit immediately" and "shutdown-first" across quit gestures, largely
+due to incremental changes and regressions in state tracking. This doc reflects the current
+unified, shutdown-first approach. See PR #8936 for the detailed history and rationale.