Use Reason in your editor (ACP)

Run Reason as the agent in Zed or any Agent Client Protocol editor.

reason acp runs Reason as an Agent Client Protocol agent over stdio.¹ Each editor thread is a Reason Session with the same ID, so you can continue it in the app or with reason --resume ID.

Set up

Install the Reason CLI (0.2.406 or later; reason update) and sign in with reason login, or set REASON_API_KEY. Then add Reason as a custom agent.

Zed

In settings.json:

{
  "agent_servers": {
    "Reason": { "type": "custom", "command": "reason", "args": ["acp"] }
  }
}

Open the agent panel, click +, and pick Reason.

Any ACP client

Add a custom agent with the command reason and the argument acp. It speaks ACP on stdin and stdout and writes logs to stderr.

If you aren’t signed in, the editor shows Sign in to Reason, which runs reason login in its terminal.

Where Sessions run

reason acp takes the same flags as reason "PROMPT". Add them to args.

args	Runs on
["acp"]	This computer, in the editor’s project folder, through reason connect. Edits land in your files.
["acp", "--cloud"]	Reason’s cloud, on the folder’s GitHub or GitLab repository if it has one.
["acp", "--on", "NAME"]	The machine NAME.

--model ID and --reasoning-effort LEVEL set the starting choice. You can also change both from the editor’s pickers.

What works

• Streaming replies, reasoning, tool calls, and file edits as diffs
• Stop, follow-ups, and questions Reason asks (answer with your next prompt)
• @ file mentions and images
• Thread history: the editor lists your workspace’s recent Sessions and reopens them with their history

Reason runs its own tools, so it doesn’t use the editor’s file system, terminal, or MCP servers. Sending images with an API key needs the deployment:read scope.

---

¹ Reason is an ACP agent only. It doesn’t act as an ACP client.