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## Why The split filesystem policy stack already supports exact and glob `access = none` read restrictions on macOS and Linux. Windows still needed subprocess handling for those deny-read policies without claiming enforcement from a backend that cannot provide it. ## Key finding The unelevated restricted-token backend cannot safely enforce deny-read overlays. Its `WRITE_RESTRICTED` token model is authoritative for write checks, not read denials, so this PR intentionally fails that backend closed when deny-read overrides are present instead of claiming unsupported enforcement. ## What changed This PR adds the Windows deny-read enforcement layer and makes the backend split explicit: - Resolves Windows deny-read filesystem policy entries into concrete ACL targets. - Preserves exact missing paths so they can be materialized and denied before an enforceable sandboxed process starts. - Snapshot-expands existing glob matches into ACL targets for Windows subprocess enforcement. - Honors `glob_scan_max_depth` when expanding Windows deny-read globs. - Plans both the configured lexical path and the canonical target for existing paths so reparse-point aliases are covered. - Threads deny-read overrides through the elevated/logon-user Windows sandbox backend and unified exec. - Applies elevated deny-read ACLs synchronously before command launch rather than delegating them to the background read-grant helper. - Reconciles persistent deny-read ACEs per sandbox principal so policy changes do not leave stale deny-read ACLs behind. - Fails closed on the unelevated restricted-token backend when deny-read overrides are present, because its `WRITE_RESTRICTED` token model is not authoritative for read denials. ## Landed prerequisites These prerequisite PRs are already on `main`: 1. #15979 `feat(permissions): add glob deny-read policy support` 2. #18096 `feat(sandbox): add glob deny-read platform enforcement` 3. #17740 `feat(config): support managed deny-read requirements` This PR targets `main` directly and contains only the Windows deny-read enforcement layer. ## Implementation notes - Exact deny-read paths remain enforceable on the elevated path even when they do not exist yet: Windows materializes the missing path before applying the deny ACE, so the sandboxed command cannot create and read it during the same run. - Existing exact deny paths are preserved lexically until the ACL planner, which then adds the canonical target as a second ACL target when needed. That keeps both the configured alias and the resolved object covered. - Windows ACLs do not consume Codex glob syntax directly, so glob deny-read entries are expanded to the concrete matches that exist before process launch. - Glob traversal deduplicates directory visits within each pattern walk to avoid cycles, without collapsing distinct lexical roots that happen to resolve to the same target. - Persistent deny-read ACL state is keyed by sandbox principal SID, so cleanup only removes ACEs owned by the same backend principal. - Deny-read ACEs are fail-closed on the elevated path: setup aborts if mandatory deny-read ACL application fails. - Unelevated restricted-token sessions reject deny-read overrides early instead of running with a silently unenforceable read policy. ## Verification - `cargo test -p codex-core windows_restricted_token_rejects_unreadable_split_carveouts` - `just fmt` - `just fix -p codex-core` - `just fix -p codex-windows-sandbox` - GitHub Actions rerun is in progress on the pushed head. --------- Co-authored-by: Codex <noreply@openai.com>
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.