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In development · no stable release yet GPLv3, royalty-free or commercial — your choice

cox.

A modular terminal coding agent in Rust with a safe, event-driven core.

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/pyrlyn/cox/releases/latest/download/cox-installer.sh | sh
View on GitHub Read the docs
Abstract interlocking glass rings glowing lime green on a dark background.
StatusActive development
APIsNot yet stable
ReleaseNo stable release yet
SurfacesTUI · headless · ACP · MCP

See it run

cox, in the terminal.

cox — interactive 
$ cox
# Enter sends, Esc interrupts
$ cox "explain the layout of this repository"
# optionally with a first prompt
From the cox README: Enter sends, Esc interrupts; y/s/n answer approval prompts, /model switches tiers, /compact compacts context.
cox — headless 
$ cox run -p "add a unit test for parse_args" --output-format json --max-turns 20
$ cox run --continue -p "now run the tests"
$ cox sessions --grep "parse_args"
$ cox stats --day
From the cox README: script a headless run and pick up where it stopped.
cox — editor & agents 
$ cox acp
# Zed and JetBrains, over the Agent Client Protocol
$ cox mcp --allow-write
# built-in tools for other agents; read-only unless you opt in
From the cox README: cox acp serves Zed and JetBrains over the Agent Client Protocol; cox mcp serves the built-in tools to other agents (read-only unless you opt in).

One event stream

  1. Submission prompt, approval, command
  2. Core pure state machine
  3. Event typed, streamed
  4. Surfaces TUI · headless · ACP · MCP

Overview

What cox does.

cox is named for the coxswain: it steers the work while models, tools, and extensions row. It is one reliable, testable agent core with several ways to use it: an interactive terminal UI, headless automation, editor integration through ACP, and MCP tools for other agents.

cox is under active development. APIs, configuration, and installation instructions are not yet stable.

Features

Built for real workflows.

Install

Up and running in a minute.

Install

Prebuilt binaries for macOS (Apple silicon) and Linux (x86-64 and arm64):

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/pyrlyn/cox/releases/latest/download/cox-installer.sh | sh

From source (Rust is pinned with mise):

git clone https://github.com/pyrlyn/cox && cd cox
mise exec -- cargo build -p cox

Update an installed binary with cox self update.

Usage

Check the machine, then run one prompt headlessly:

export ANTHROPIC_API_KEY=sk-...   # or OPENAI_API_KEY
cox doctor
cox run -p "create hello.txt containing hi"

More examples below.

Usage examples

Real commands, straight from the docs.

Open the interactive TUI (Enter sends, Esc interrupts; y/s/n answer approval prompts, /model switches tiers, /compact compacts context), optionally with a first prompt:

cox
cox "explain the layout of this repository"

Script a headless run and pick up where it stopped:

cox run -p "add a unit test for parse_args" --output-format json --max-turns 20
cox run --continue -p "now run the tests"

Find a past session, read archived output and costs:

cox sessions --grep "parse_args"
cox expand <id> --lines 60-90
cox stats --day
cox stats --cache

Inspect configuration and extensions:

cox config show --sources
cox config set tiers.code.model '"claude-sonnet-5"'
cox ext list

Serve cox to an editor or another agent:

cox acp
cox mcp --allow-write

Links

License

You can use cox under any of the following licenses, at your choice:

  1. GNU GPLv3 — free for open-source applications on any platform, including embedded systems.
  2. Royalty-free license — free for proprietary desktop, mobile and web applications, as long as you disclose that your application uses the project. Embedded systems are not covered.
  3. Commercial license — for proprietary applications, including embedded systems, without the attribution requirement.

Pricing

Pro is a placeholder

Free forever. Pro when you need it.

Free · open source

GPLv3, royalty-free or commercial — your choice

$0forever

  • Terminal UI and headless runs
  • Sandboxed tools by default
  • Local cost ledger
Install free

cox Pro

Placeholder

$15 / moper seat

  • Shared session history
  • Org permission policies
  • Priority support

Placeholder — the Pro waitlist is not open yet.

Try cox today.

Free and open source. Star it, file an issue, or send a pull request.

Read the docs github.com/pyrlyn/cox