Attached repo and coding

Brain is not a full IDE (no LSP or inline apply). In Agent mode you can attach a GitHub repo so the agent clones it into a temporary sandbox at /workspace — not onto your Brain server disk.

Attach a repo

1. Switch composer mode to Agent
2. Open the Attached repo control in the composer
3. Paste owner/name or a GitHub URL (optional git ref)
4. Clear the attachment when finished

For private repositories, connect GitHub first so clone credentials work.

What the agent does

• Clones into the sandbox workspace
• Explores and edits with coding tools
• Can follow the open PR skill: create a branch, commit, push, and open a pull request

Ask mode ignores coding tools even if a repo is attached.

Opening a pull request

Ask in Agent mode to open a PR after the change is ready. Typical flow:

1. Branch from the attached ref
2. Commit sandbox changes
3. Push to GitHub
4. Open the PR via GitHub MCP (needs GitHub connected)

Review the PR on GitHub like any other change.

Dual path

Prefer the sandbox harness for local file edits; use GitHub MCP for remote GitHub API operations (PRs, issues).

Host requirements (microsandbox)

Brain pins microsandbox for the coding sandbox (not Vercel Sandbox).

If the runtime is missing, coding tools fail with a clear error. Operators may need the microsandbox platform install or MSB_PATH pointing at the binary. There is no Brain-specific sandbox API key in .env.example.

See Troubleshooting if attached-repo turns fail after deploy.