Ace: GitHub Next's open-source tool for multiplayer agentic development

Ace is an open-source experiment from GitHub Next for real-time, multiplayer software development with AI agents. It lets teammates join shared channels, discuss a task, and direct an agent in the conversation; the agent can respond to questions from anyone in the channel. Each piece of work uses an isolated Git worktree and branch, with one chat writing to a lane at a time, and completed work landing as a pull request. Channels run on a host machine, usually a Mac, so agents can use its shell, development tools, signed-in command-line apps, desktop software, and connected hardware. Teammates can see activity and catch up on messages and agent work they missed.

Ace coordinates teams through Tailscale: people and machines on the same network form the team, while project access depends on GitHub permissions or explicit sharing. A small directory service, deployed to the team’s own account, lists projects, hosts, and channels but stores no messages, code, or diffs. Channel traffic travels between hosts over the tailnet; an optional beta cloud channel can run in the team’s account when laptops are offline. The main tradeoff is that agents run with the host user’s privileges, not inside sandboxes, and can affect files beyond a project. Teammate access to an agent starts disabled, and the guidance is to collaborate only with trusted people and keep the host private. Ace is MIT licensed, has no service behind it, and is presented as a fast-moving tool with rough edges.