Files
codex/codex-rs
T
jif-oai fd36838cf3 Add MultiAgentV2 root and subagent context hints (#19805)
## Why

MultiAgentV2 sessions need startup guidance that matches the role of the
thread that is actually being created. Root agents and subagents have
different responsibilities, and forked subagents can inherit parent
rollout history. If the parent hint is carried into the child context,
the child can see stale or conflicting developer guidance before its own
session-specific context is added.

## What changed

- Added `features.multi_agent_v2.root_agent_usage_hint_text` and
`features.multi_agent_v2.subagent_usage_hint_text` config fields,
including schema/config parsing support.
- Injected the matching root or subagent hint into the initial context
as its own developer message when `multi_agent_v2` is enabled.
- Filtered configured MultiAgentV2 usage-hint developer messages out of
forked parent history so a child thread receives fresh guidance for its
own session source/config.
- Added targeted coverage for config parsing, initial-context rendering,
feature-config deserialization, and forked-history filtering.

## Context examples

With this config:

```toml
[features.multi_agent_v2]
enabled = true
root_agent_usage_hint_text = "Root guidance."
subagent_usage_hint_text = "Subagent guidance."
```

A root thread initial context renders the root hint as a standalone
developer message:

```text
[developer]
<existing developer context, when present>

[developer]
Root guidance.
```

A subagent thread initial context renders the subagent hint instead:

```text
[developer]
<existing developer context, when present>

[developer]
Subagent guidance.
```

When a subagent forks parent history, any parent developer message whose
text exactly matches the configured MultiAgentV2 root or subagent hint
is omitted from the forked history before the child receives its fresh
subagent hint.
fd36838cf3 · 2026-04-28 12:31:45 +02:00
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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

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 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.