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The Cursor agent runtime in Mains uses the Cursor Agent CLI (the agent binary) and communicates with it over the Agent Client Protocol (ACP) via stdio. These settings control authentication, model selection, and how the agent operates during runs.

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Installation & Authentication

Mains drives the Cursor Agent CLI as a subprocess. You must install and authenticate the CLI before using it inside Mains.
1

Install the Cursor Agent CLI

Run the official installer in your terminal:
2

Authenticate

Launch the CLI once to log in with your Cursor account:
Follow the browser prompt to complete authentication. Mains reuses these credentials automatically.
3

Open Mains

Open a Cursor workspace from the sidebar. Mains spawns the CLI on demand and connects via ACP.
Need help with the CLI itself? See the official Cursor CLI Setup Guide.

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Mode

The mode controls how Cursor behaves during runs. You set it once in Settings > Cursor, and Mains applies it to every session.
Pulse-driven runs always force agent mode regardless of your default. This guarantees scheduled tasks can complete autonomously without human input.

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Model Selection

Cursor exposes the list of available models through ACP after a session starts. Mains picks them up automatically and lets you choose a default model in settings. When you start a run, Mains sends session/set_config_option with your preferred model. If the model is unavailable, the session falls back to Cursor’s default for your account.

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MCP Tools

Cursor sessions automatically receive Mains’ bundled MCP tools at startup — these include git operations, package safety checks, and workspace utilities. You can also add your own MCP servers; see MCP Servers for setup. Cursor extensions like update_todos, generate_image, and the task subagent are exposed as native ACP capabilities, not MCP tools.

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Tool Approval

Cursor sends a session/request_permission ACP request when it wants to invoke a tool that requires user confirmation. Mains shows an interactive approval dialog in the workspace UI — you can allow once, deny, or remember the decision for the session.