fix(cli): reset terminal input modes on TUI exit to stop focus/mouse leaks

[maxmilian]

Summary

When the TUI exits via Ctrl+C, SIGTERM/SIGHUP, or a crash, prompt_toolkit's teardown can be bypassed, leaving DEC 1004 (focus reporting) and 1000/1002/1003 (mouse tracking) enabled. The terminal then emits raw ESC[I / ESC[O focus events and fragmented SGR mouse reports as visible text in whatever runs next in the same tab.

Fixes #36823.

Root cause

_TERMINAL_INPUT_MODE_RESET_SEQ already exists and is emitted by _recover_terminal_input_modes — but only reactively, mid-session, when leaked mouse reports are detected. Nothing emits it on exit. On a clean teardown prompt_toolkit restores the modes itself; on Ctrl+C / signal / crash that unwind is skipped and the modes leak.

Fix

_run_cleanup() — the once-only cleanup that runs on every exit path (it's atexit-registered and also called explicitly on normal/EOF/interrupt exit) — now calls a new _reset_terminal_input_modes_on_exit() as its final step. The helper writes _TERMINAL_INPUT_MODE_RESET_SEQ to sys.stdout guarded on isatty(). The disable codes are no-ops for any mode that was never enabled, so emitting them unconditionally on a TTY is safe and idempotent.

Scope / known limitation: SIGKILL is uncatchable, so kill -9 mid-run still leaves the modes set — nothing in-process can prevent that. This fix covers normal quit, Ctrl+C, and SIGTERM/SIGHUP, which are the catchable paths.

Tests

tests/cli/test_tui_terminal_reset_on_exit.py (4, all pass):

• emits the full reset sequence (incl. ESC[?1004l) and flushes on a TTY
• no-ops when stdout is not a TTY (won't pollute piped/redirected output)
• swallows stdout errors (cleanup must never raise at teardown)
• is wired into _run_cleanup (the catch-all exit path)

ruff check clean; scripts/check-windows-footguns.py clean; existing tests/cli import sanity passes.

Infographic

[tonydwb]

Code Review Summary

Verdict: Approved

✅ Looks Good

• Fixes a real UX issue: terminal input modes (focus reporting + mouse tracking) leaking into next shell session
• Properly gated on _tui_input_modes_active flag so one-shot non-TUI CLI runs don't emit escape codes
• Written as first step in _run_cleanup (atexit) so it runs even if later cleanup raises
• Falls back to /dev/tty when stdout is redirected
• Graceful error handling: all exceptions swallowed (cleanup must never raise)
• Comprehensive tests: 7 test cases covering TTY, non-TTY, /dev/tty fallback, stdout errors, flag lifecycle, and cleanup wiring
• Known limitation documented: kill -9 and os._exit(0) paths bypass atexit

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Reviewed by Hermes Agent