fxrs

fxrs is a compact Rust rewrite of vercel-labs/fx. It preserves the coding-agent semantics reachable through ACP while keeping providers, authentication, tools, persistence, and host effects behind independent boundaries.

It includes a fast full-screen terminal interface and an ACP stdio server. The TUI is itself an ACP client, so interactive use and editor integrations share the same provider, authentication, session, tool, and permission semantics.

Quick start

Start the terminal interface in the current workspace:

fxrs

Enter sends a prompt, Shift+Enter inserts a newline, Esc cancels an active turn, Ctrl+M selects a model, and Shift+Tab cycles the session mode. Use /help for the complete keyboard and command reference. Notable commands include /login, /model, /mode, /resume, /new, /clear, and /quit.

The interface streams Markdown responses and reasoning, updates tool cards in place, provides foldable scrollback, queues follow-up prompts, and presents ACP permission requests as keyboard- and mouse-operable cards. Set NO_COLOR=1 for a monochrome theme.

The focus, scrollback, and contextual-permission interactions take inspiration from xAI's grok-build; fxrs keeps its implementation and runtime architecture independent.

Install

Install the complete command set from crates.io:

cargo install fxrs --locked

Prebuilt archives are also available from GitHub Releases. Both methods install the same four executables, which must remain in the same directory:

fxrs
fx-tui
fx-acp
fx-terminal-host

fx-tui is the interactive frontend. fx-acp and fx-terminal-host are private companions; the latter retains PTYs and monitors across sessions.

To build from source:

git clone https://github.com/Leeeon233/fx-rs.git
cd fx-rs
cargo build --release --locked --workspace
./target/release/fxrs acp --help

Resume a durable session or select a different workspace with:

fxrs tui --session <session-id>
fxrs tui --cwd /path/to/project

ACP integration

Configure an ACP client to launch fxrs with acp as its first argument. An optional model route can be selected explicitly:

fxrs acp --model codex/gpt-5.6-sol

Authentication

The ACP initialize response advertises the codex:chatgpt authentication method. An ACP client can invoke authenticate to open the browser-based ChatGPT OAuth flow. fxrs stores credentials it owns under ~/.fx/credentials, with private permissions, process locks, and atomic replacement.

If no fxrs-owned credential exists, the Codex Provider can read a valid ~/.codex/auth.json created by codex login. That ambient credential is never refreshed, rewritten, or deleted by fxrs.

In the TUI, run /login to invoke the advertised authentication method; when multiple providers advertise methods, fxrs opens a provider picker. Authentication remains provider-owned, and the frontend contains no Codex-specific credential logic.

Architecture

Codex is the first concrete Provider. The registry supports multiple providers at once and routes models as provider/model, so adding OpenAI API-key, Anthropic, or other adapters does not change the agent loop, ACP projection, credential store, or child-agent model selection.

ACP-reachable capabilities include durable event-log sessions, streaming and cancellation, permission review, filesystem tools, PTY sessions and monitors, web search/fetch, skills, memory, stored tool results, MCP stdio/Streamable HTTP tools, scoped project instructions, and durable subagents.

See the architecture, migration map, release procedure, and frozen Zig source inventory.

Development

cargo fmt --all --check
cargo clippy --workspace --all-targets --locked -- -D warnings
cargo test --workspace --locked

See the contribution guidelines and security policy.

License

Licensed under the Apache License 2.0.