Felipe Coury
ec8d4bfc77
## Problem When a user resumed or forked a session, the TUI could render the restored thread history immediately, but it did not receive token usage until a later model turn emitted a fresh usage event. That left the context/status UI blank or stale during the exact window where the user expects resumed state to look complete. Core already reconstructed token usage from the rollout; the missing behavior was app-server lifecycle replay to the client that just attached. ## Mental model Token usage has two representations. The rollout is the durable source of historical `TokenCount` events, and the core session cache is the in-memory snapshot reconstructed from that rollout on resume or fork. App-server v2 clients do not read core state directly; they learn about usage through `thread/tokenUsage/updated`. The fix keeps those roles separate: core exposes the restored `TokenUsageInfo`, and app-server sends one targeted notification after a successful `thread/resume` or `thread/fork` response when that restored snapshot exists. This notification is not a new model event. It is a replay of already-persisted state for the client that just attached. That distinction matters because using the normal core event path here would risk duplicating `TokenCount` entries in the rollout and making future resumes count historical usage twice. ## Non-goals This change does not add a new protocol method or payload shape. It reuses the existing v2 `thread/tokenUsage/updated` notification and the TUI’s existing handler for that notification. This change does not alter how token usage is computed, accumulated, compacted, or written during turns. It only exposes the token usage that resume and fork reconstruction already restored. This change does not broadcast historical usage replay to every subscribed client. The replay is intentionally scoped to the connection that requested resume or fork so already-attached clients are not surprised by an old usage update while they may be rendering live activity. ## Tradeoffs Sending the usage notification after the JSON-RPC response preserves a clear lifecycle order: the client first receives the thread object, then receives restored usage for that thread. The tradeoff is that usage is still a notification rather than part of the `thread/resume` or `thread/fork` response. That keeps the protocol shape stable and avoids duplicating usage fields across response types, but clients must continue listening for notifications after receiving the response. The helper selects the latest non-in-progress turn id for the replayed usage notification. This is conservative because restored usage belongs to completed persisted accounting, not to newly attached in-flight work. The fallback to the last turn preserves a stable wire payload for unusual histories, but histories with no meaningful completed turn still have a weak attribution story. ## Architecture Core already seeds `Session` token state from the last persisted rollout `TokenCount` during `InitialHistory::Resumed` and `InitialHistory::Forked`. The new core accessor exposes the complete `TokenUsageInfo` through `CodexThread` without giving app-server direct session mutation authority. App-server calls that accessor from three lifecycle paths: cold `thread/resume`, running-thread resume/rejoin, and `thread/fork`. In each path, the server sends the normal response first, then calls a shared helper that converts core usage into `ThreadTokenUsageUpdatedNotification` and sends it only to the requesting connection. The tests build fake rollouts with a user turn plus a persisted token usage event. They then exercise `thread/resume` and `thread/fork` without starting another model turn, proving that restored usage arrives before any next-turn token event could be produced. ## Observability The primary debug path is the app-server JSON-RPC stream. After `thread/resume` or `thread/fork`, a client should see the response followed by `thread/tokenUsage/updated` when the source rollout includes token usage. If the notification is absent, check whether the rollout contains an `event_msg` payload of type `token_count`, whether core reconstruction seeded `Session::token_usage_info`, and whether the connection stayed attached long enough to receive the targeted notification. The notification is sent through the existing `OutgoingMessageSender::send_server_notification_to_connections` path, so existing app-server tracing around server notifications still applies. Because this is a replay, not a model turn event, debugging should start at the resume/fork handlers rather than the turn event translation in `bespoke_event_handling`. ## Tests The focused regression coverage is `cargo test -p codex-app-server emits_restored_token_usage`, which covers both resume and fork. The core reconstruction guard is `cargo test -p codex-core record_initial_history_seeds_token_info_from_rollout`. Formatting and lint/fix passes were run with `just fmt`, `just fix -p codex-core`, and `just fix -p codex-app-server`. Full crate test runs surfaced pre-existing unrelated failures in command execution and plugin marketplace tests; the new token usage tests passed in focused runs and within the app-server suite before the unrelated command execution failure.
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 [--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 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.
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.