Robby He
f3989f6092
# Unified Exec Shell Selection on Windows ## Problem reference issue #7466 The `unified_exec` handler currently deserializes model-provided tool calls into the `ExecCommandArgs` struct: ```rust #[derive(Debug, Deserialize)] struct ExecCommandArgs { cmd: String, #[serde(default)] workdir: Option<String>, #[serde(default = "default_shell")] shell: String, #[serde(default = "default_login")] login: bool, #[serde(default = "default_exec_yield_time_ms")] yield_time_ms: u64, #[serde(default)] max_output_tokens: Option<usize>, #[serde(default)] with_escalated_permissions: Option<bool>, #[serde(default)] justification: Option<String>, } ``` The `shell` field uses a hard-coded default: ```rust fn default_shell() -> String { "/bin/bash".to_string() } ``` When the model returns a tool call JSON that only contains `cmd` (which is the common case), Serde fills in `shell` with this default value. Later, `get_command` uses that value as if it were a model-provided shell path: ```rust fn get_command(args: &ExecCommandArgs) -> Vec<String> { let shell = get_shell_by_model_provided_path(&PathBuf::from(args.shell.clone())); shell.derive_exec_args(&args.cmd, args.login) } ``` On Unix, this usually resolves to `/bin/bash` and works as expected. However, on Windows this behavior is problematic: - The hard-coded `"/bin/bash"` is not a valid Windows path. - `get_shell_by_model_provided_path` treats this as a model-specified shell, and tries to resolve it (e.g. via `which::which("bash")`), which may or may not exist and may not behave as intended. - In practice, this leads to commands being executed under a non-default or non-existent shell on Windows (for example, WSL bash), instead of the expected Windows PowerShell or `cmd.exe`. The core of the issue is that **"model did not specify `shell`" is currently interpreted as "the model explicitly requested `/bin/bash`"**, which is both Unix-specific and wrong on Windows. ## Proposed Solution Instead of hard-coding `"/bin/bash"` into `ExecCommandArgs`, we should distinguish between: 1. **The model explicitly specifying a shell**, e.g.: ```json { "cmd": "echo hello", "shell": "pwsh" } ``` In this case, we *do* want to respect the model’s choice and use `get_shell_by_model_provided_path`. 2. **The model omitting the `shell` field entirely**, e.g.: ```json { "cmd": "echo hello" } ``` In this case, we should *not* assume `/bin/bash`. Instead, we should use `default_user_shell()` and let the platform decide. To express this distinction, we can: 1. Change `shell` to be optional in `ExecCommandArgs`: ```rust #[derive(Debug, Deserialize)] struct ExecCommandArgs { cmd: String, #[serde(default)] workdir: Option<String>, #[serde(default)] shell: Option<String>, #[serde(default = "default_login")] login: bool, #[serde(default = "default_exec_yield_time_ms")] yield_time_ms: u64, #[serde(default)] max_output_tokens: Option<usize>, #[serde(default)] with_escalated_permissions: Option<bool>, #[serde(default)] justification: Option<String>, } ``` Here, the absence of `shell` in the JSON is represented as `shell: None`, rather than a hard-coded string value.
Codex CLI (Rust Implementation)
We provide Codex CLI as a standalone, native 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? Follow the walkthrough in
docs/getting-started.mdfor prompts, keyboard shortcuts, and session management. - Already shipping with Codex and want deeper control? Jump to
docs/advanced.mdand the configuration reference atdocs/config.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.
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. Output is printed to the terminal directly. You can set the RUST_LOG environment variable to see more about what's going on.
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".
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.