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## Why The desktop app on Windows needs a read-only way to tell, before the next tool call, whether the local Windows sandbox setup is in a state that should block the user and ask for setup again. The main case we want to cover is the elevated sandbox setup version bump. Today, if the app is configured for elevated Windows sandboxing and the installed setup is stale, the next sandboxed shell/exec path can end up triggering the elevated setup flow directly. That means the user can see an unexpected UAC prompt with no UI explanation. This change adds a small app-server preflight so the desktop app can ask “is Windows sandbox ready, not configured, or update-required?” during startup and show the appropriate blocking UI before the user hits a tool call. ## What changed - Added a new read-only app-server RPC: `windowsSandbox/readiness` - Added a new protocol enum and response type: - `WindowsSandboxReadiness` - `WindowsSandboxReadinessResponse` - Added core readiness logic in `core/src/windows_sandbox.rs`: - `ready` - `notConfigured` - `updateRequired` - Wired the new request through `codex_message_processor` - Regenerated the vendored app-server schema fixtures ## Readiness semantics This is intentionally a coarse startup/version-bump readiness check, not a full predictor of every runtime repair case. For now, readiness is determined from: - the configured Windows sandbox level - `sandbox_setup_is_complete()` for elevated mode That means: - `disabled` maps to `notConfigured` - `restricted token` maps to `ready` - `elevated` maps to `ready` or `updateRequired` depending on `sandbox_setup_is_complete()` This is deliberate for the first UI integration because the common case we want to catch is “the app updated, the elevated setup version bumped, and the user should see an update-required blocker instead of a surprise UAC prompt”. It does not attempt to model every case where the deeper runtime path might decide to repair or re-run setup. ## Testing - Ran `cargo fmt --all -- app-server-protocol/src/protocol/common.rs app-server-protocol/src/protocol/v2.rs app-server/src/codex_message_processor.rs core/src/windows_sandbox.rs core/src/windows_sandbox_tests.rs` - Added unit tests for the pure readiness mapping in `core/src/windows_sandbox_tests.rs` - Regenerated vendored schema fixtures with `cargo run -p codex-app-server-protocol --bin write_schema_fixtures -- --schema-root app-server-protocol/schema` - Did not run the full cargo test suite
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
The legacy notify setting is deprecated and will be removed in a future release. Existing configurations still work, but new automation should use lifecycle hooks instead. The notify documentation explains the remaining compatibility behavior. 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 [--log-denials] [COMMAND]...
# Linux
codex sandbox linux [COMMAND]...
# Windows
codex sandbox windows [COMMAND]...
# Legacy aliases
codex debug seatbelt [--log-denials] [COMMAND]...
codex debug landlock [COMMAND]...
To try a writable legacy sandbox mode with these commands, pass an explicit config override such
as -c 'sandbox_mode="workspace-write"'.
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 becomes 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.