> ## Documentation Index
> Fetch the complete documentation index at: https://ara-90a60a07.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# 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](https://agentclientprotocol.com) agent over stdio.<sup>[1](#acp-client)</sup> 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](/docs/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.

<Tabs>
  <Tab title="Zed">
    In `settings.json`:

    ```json theme={null}
    {
      "agent_servers": {
        "Reason": { "type": "custom", "command": "reason", "args": ["acp"] }
      }
    }
    ```

    Open the agent panel, click **+**, and pick **Reason**.
  </Tab>

  <Tab title="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.
  </Tab>
</Tabs>

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.

***

<p id="acp-client"><sup>1</sup> Reason is an ACP agent only. It doesn't act as an ACP client.</p>


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