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codex/codex-rs/tui
Eric Traut adca1b643f [1 of 2] Optimize TUI startup terminal probes (#23175)
## Why

Codex TUI startup still feels slower than 0.117.0 after the app-server
move in 0.118.0. A visible chunk of launch-to-input latency comes from
serial terminal startup probes: cursor position, keyboard enhancement
support, and default foreground/background color queries can each wait
on terminal responses before the first usable frame.

Refs #16335.

## What

This PR batches the terminal startup probes into one bounded probe. It
also reuses the probed cursor position and default colors during TUI
setup, fast-paths the primary-device-attributes fallback as keyboard
enhancement unsupported, and keeps lightweight startup timing logs for
future tuning.

The startup telemetry is intentionally left in production: it records
phase timings for terminal probes and initial-frame scheduling so future
startup regressions can be diagnosed from normal logs rather than
re-adding one-off debug instrumentation.

## Benchmark

In the local pty startup benchmark, the pre-optimization `main` baseline
was about 250.5ms median from launch to accepted chat input. This
probe-only branch measured about 152ms median, for an approximate
savings of 95-100ms.

## Stack

1. [#23175: [1 of 2] Optimize TUI startup terminal
probes](https://github.com/openai/codex/pull/23175) — this PR
2. [#23176: [2 of 2] Start fresh TUI thread in
background](https://github.com/openai/codex/pull/23176) — layered on
this PR

## Verification

- `cargo test -p codex-tui`
2026-05-18 09:04:02 -07:00
..