889ee018e7
## Why Codex intentionally ignores unknown `config.toml` fields by default so older and newer config files keep working across versions. That leniency also makes typo detection hard because misspelled or misplaced keys disappear silently. This change adds an opt-in strict config mode so users and tooling can fail fast on unrecognized config fields without changing the default permissive behavior. This feature is possible because `serde_ignored` exposes the exact signal Codex needs: it lets Codex run ordinary Serde deserialization while recording fields Serde would otherwise ignore. That avoids requiring `#[serde(deny_unknown_fields)]` across every config type and keeps strict validation opt-in around the existing config model. ## What Changed ### Added strict config validation - Added `serde_ignored`-based validation for `ConfigToml` in `codex-rs/config/src/strict_config.rs`. - Combined `serde_ignored` with `serde_path_to_error` so strict mode preserves typed config error paths while also collecting fields Serde would otherwise ignore. - Added strict-mode validation for unknown `[features]` keys, including keys that would otherwise be accepted by `FeaturesToml`'s flattened boolean map. - Kept typed config errors ahead of ignored-field reporting, so malformed known fields are reported before unknown-field diagnostics. - Added source-range diagnostics for top-level and nested unknown config fields, including non-file managed preference source names. ### Kept parsing single-pass per source - Reworked file and managed-config loading so strict validation reuses the already parsed `TomlValue` for that source. - For actual config files and managed config strings, the loader now reads once, parses once, and validates that same parsed value instead of deserializing multiple times. - Validated `-c` / `--config` override layers with the same base-directory context used for normal relative-path resolution, so unknown override keys are still reported when another override contains a relative path. ### Scoped `--strict-config` to config-heavy entry points - Added support for `--strict-config` on the main config-loading entry points where it is most useful: - `codex` - `codex resume` - `codex fork` - `codex exec` - `codex review` - `codex mcp-server` - `codex app-server` when running the server itself - the standalone `codex-app-server` binary - the standalone `codex-exec` binary - Commands outside that set now reject `--strict-config` early with targeted errors instead of accepting it everywhere through shared CLI plumbing. - `codex app-server` subcommands such as `proxy`, `daemon`, and `generate-*` are intentionally excluded from the first rollout. - When app-server strict mode sees invalid config, app-server exits with the config error instead of logging a warning and continuing with defaults. - Introduced a dedicated `ReviewCommand` wrapper in `codex-rs/cli` instead of extending shared `ReviewArgs`, so `--strict-config` stays on the outer config-loading command surface and does not become part of the reusable review payload used by `codex exec review`. ### Coverage - Added tests for top-level and nested unknown config fields, unknown `[features]` keys, typed-error precedence, source-location reporting, and non-file managed preference source names. - Added CLI coverage showing invalid `--enable`, invalid `--disable`, and unknown `-c` overrides still error when `--strict-config` is present, including compound-looking feature names such as `multi_agent_v2.subagent_usage_hint_text`. - Added integration coverage showing both `codex app-server --strict-config` and standalone `codex-app-server --strict-config` exit with an error for unknown config fields instead of starting with fallback defaults. - Added coverage showing unsupported command surfaces reject `--strict-config` with explicit errors. ## Example Usage Run Codex with strict config validation enabled: ```shell codex --strict-config ``` Strict config mode is also available on the supported config-heavy subcommands: ```shell codex --strict-config exec "explain this repository" codex review --strict-config --uncommitted codex mcp-server --strict-config codex app-server --strict-config --listen off codex-app-server --strict-config --listen off ``` For example, if `~/.codex/config.toml` contains a typo in a key name: ```toml model = "gpt-5" approval_polic = "on-request" ``` then `codex --strict-config` reports the misspelled key instead of silently ignoring it. The path is shortened to `~` here for readability: ```text $ codex --strict-config Error loading config.toml: ~/.codex/config.toml:2:1: unknown configuration field `approval_polic` | 2 | approval_polic = "on-request" | ^^^^^^^^^^^^^^ ``` Without `--strict-config`, Codex keeps the existing permissive behavior and ignores the unknown key. Strict config mode also validates ad-hoc `-c` / `--config` overrides: ```text $ codex --strict-config -c foo=bar Error: unknown configuration field `foo` in -c/--config override $ codex --strict-config -c features.foo=true Error: unknown configuration field `features.foo` in -c/--config override ``` Invalid feature toggles are rejected too, including values that look like nested config paths: ```text $ codex --strict-config --enable does_not_exist Error: Unknown feature flag: does_not_exist $ codex --strict-config --disable does_not_exist Error: Unknown feature flag: does_not_exist $ codex --strict-config --enable multi_agent_v2.subagent_usage_hint_text Error: Unknown feature flag: multi_agent_v2.subagent_usage_hint_text ``` Unsupported commands reject the flag explicitly: ```text $ codex --strict-config cloud list Error: `--strict-config` is not supported for `codex cloud` ``` ## Verification The `codex-cli` `strict_config` tests cover invalid `--enable`, invalid `--disable`, the compound `multi_agent_v2.subagent_usage_hint_text` case, unknown `-c` overrides, app-server strict startup failure through `codex app-server`, and rejection for unsupported commands such as `codex cloud`, `codex mcp`, `codex remote-control`, and `codex app-server proxy`. The config and config-loader tests cover unknown top-level fields, unknown nested fields, unknown `[features]` keys, source-location reporting, non-file managed config sources, and `-c` validation for keys such as `features.foo`. The app-server test suite covers standalone `codex-app-server --strict-config` startup failure for an unknown config field. ## Documentation The Codex CLI docs on developers.openai.com/codex should mention `--strict-config` as an opt-in validation mode for supported config-heavy entry points once this ships.
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 [--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.