Felipe Coury
48f117d0a2
# Summary This removes startup `skills/list` from the critical path to first input. In release measurements, median startup-to-input time improved from `307.5 ms` to `191.0 ms` across 30 measured runs with 5 warmups. # Background Startup currently waits for a forced `skills/list` app-server request before scheduling the first usable TUI frame. That makes skill metadata freshness part of the process-launch-to-input path, even though the prompt can safely accept normal input before skill metadata has finished loading. I measured startup from process launch until the TUI reports that the user can type. The measurement harness watched the startup measurement record, killed Codex after a successful sample, and enforced a timeout so repeated runs would not leave TUI processes behind. The debug runs had enough outliers that I used median as the primary signal and ran a baseline self-compare to understand the noise floor. # Why skills/list The `skills/list` cut was the best practical optimization because it improved startup without changing the important readiness contract: when the prompt is shown, it is still backed by an active session. Only enrichment data arrives later. | Candidate | Result | Decision | | --- | --- | --- | | Defer startup `skills/list` | Debug median improved from `524.0 ms` to `348.0 ms`; release median improved from `307.5 ms` to `191.0 ms`. | Keep | | Defer fresh `thread/start` | Debug median improved from `494.0 ms` to `256.0 ms`, but the prompt could appear before an active thread was attached. | Reject as too risky for this PR | | Avoid forced skills config reload | Debug median moved from `509.0 ms` to `512.0 ms`. | Reject as neutral | | Skip fresh history metadata | Debug median moved from `496.5 ms` to `531.5 ms`. | Reject as regression/noise | | Defer app-server startup | Not implemented because it would only permit a loading frame unless the TUI gained a deliberate pre-server state. | Out of scope | # Implementation `App::refresh_startup_skills` now clones the app-server request handle, spawns a background task, and issues the same forced `skills/list` request after the first frame is scheduled. When the request completes, the task sends `AppEvent::SkillsListLoaded` back through the normal app event queue. The existing skills response handling still converts the app-server response, updates the chat widget, and emits invalid `SKILL.md` warnings. Explicit user-initiated skills refreshes still use the existing synchronous app command path, so callers that intentionally requested fresh skill state do not race ahead of their own refresh. # Tradeoffs The main tradeoff is a narrow theoretical race at startup: skill mention completion depends on a background `skills/list` response, so it could briefly show stale or empty metadata if opened before that response arrives. In manual testing, pressing `$` as soon as possible after launch still showed populated skill metadata, so this risk appears minimal in normal use. Plain input remains available immediately, and the UI updates through the existing skills response path once the refresh completes. This PR does not change how skills are discovered, cached, force-reloaded, displayed, enabled, or warned about. It only changes when the startup refresh is allowed to complete relative to the first usable TUI frame. # Verification - `cargo test -p codex-tui`
Codex CLI (Rust Implementation)
We provide Codex CLI as a standalone executable to ensure a zero-dependency install.
Installing Codex
Today, the easiest way to install Codex is via npm:
npm i -g @openai/codex
codex
You can also install via Homebrew (brew install --cask codex) or download a platform-specific release directly from our GitHub Releases.
Documentation quickstart
- First run with Codex? Start with
docs/getting-started.md(links to the walkthrough for prompts, keyboard shortcuts, and session management). - Want deeper control? See
docs/config.mdanddocs/install.md.
What's new in the Rust CLI
The Rust implementation is now the maintained Codex CLI and serves as the default experience. It includes a number of features that the legacy TypeScript CLI never supported.
Config
Codex supports a rich set of configuration options. Note that the Rust CLI uses config.toml instead of config.json. See docs/config.md for details.
Model Context Protocol Support
MCP client
Codex CLI functions as an MCP client that allows the Codex CLI and IDE extension to connect to MCP servers on startup. See the configuration documentation for details.
MCP server (experimental)
Codex can be launched as an MCP server by running codex mcp-server. This allows other MCP clients to use Codex as a tool for another agent.
Use the @modelcontextprotocol/inspector to try it out:
npx @modelcontextprotocol/inspector codex mcp-server
Use codex mcp to add/list/get/remove MCP server launchers defined in config.toml, and codex mcp-server to run the MCP server directly.
Notifications
You can enable notifications by configuring a script that is run whenever the agent finishes a turn. The notify documentation includes a detailed example that explains how to get desktop notifications via terminal-notifier on macOS. When Codex detects that it is running under WSL 2 inside Windows Terminal (WT_SESSION is set), the TUI automatically falls back to native Windows toast notifications so approval prompts and completed turns surface even though Windows Terminal does not implement OSC 9.
codex exec to run Codex programmatically/non-interactively
To run Codex non-interactively, run codex exec PROMPT (you can also pass the prompt via stdin) and Codex will work on your task until it decides that it is done and exits. If you provide both a prompt argument and piped stdin, Codex appends stdin as a <stdin> block after the prompt so patterns like echo "my output" | codex exec "Summarize this concisely" work naturally. Output is printed to the terminal directly. You can set the RUST_LOG environment variable to see more about what's going on.
Use codex exec --ephemeral ... to run without persisting session rollout files to disk.
Experimenting with the Codex Sandbox
To test to see what happens when a command is run under the sandbox provided by Codex, we provide the following subcommands in Codex CLI:
# macOS
codex sandbox macos [--full-auto] [--log-denials] [COMMAND]...
# Linux
codex sandbox linux [--full-auto] [COMMAND]...
# Windows
codex sandbox windows [--full-auto] [COMMAND]...
# Legacy aliases
codex debug seatbelt [--full-auto] [--log-denials] [COMMAND]...
codex debug landlock [--full-auto] [COMMAND]...
Selecting a sandbox policy via --sandbox
The Rust CLI exposes a dedicated --sandbox (-s) flag that lets you pick the sandbox policy without having to reach for the generic -c/--config option:
# Run Codex with the default, read-only sandbox
codex --sandbox read-only
# Allow the agent to write within the current workspace while still blocking network access
codex --sandbox workspace-write
# Danger! Disable sandboxing entirely (only do this if you are already running in a container or other isolated env)
codex --sandbox danger-full-access
The same setting can be persisted in ~/.codex/config.toml via the top-level sandbox_mode = "MODE" key, e.g. sandbox_mode = "workspace-write".
In workspace-write, Codex also includes ~/.codex/memories in its writable roots so memory maintenance does not require an extra approval.
Code Organization
This folder is the root of a Cargo workspace. It contains quite a bit of experimental code, but here are the key crates:
core/contains the business logic for Codex. Ultimately, we hope this to be a library crate that is generally useful for building other Rust/native applications that use Codex.exec/"headless" CLI for use in automation.tui/CLI that launches a fullscreen TUI built with Ratatui.cli/CLI multitool that provides the aforementioned CLIs via subcommands.
If you want to contribute or inspect behavior in detail, start by reading the module-level README.md files under each crate and run the project workspace from the top-level codex-rs directory so shared config, features, and build scripts stay aligned.