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Documentation Index

Fetch the complete documentation index at: https://docs.mains.dev/llms.txt

Use this file to discover all available pages before exploring further.

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:
curl https://cursor.com/install -fsS | bash
2

Authenticate

Launch the CLI once to log in with your Cursor account:
agent
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.
ModeDescription
agentFull autonomous agent mode — Cursor plans and executes tool calls automatically (default).
planPlan first, then execute — Cursor produces a plan and pauses for confirmation before taking action.
askAnswer-only mode — Cursor responds to questions but does not invoke tools or modify files.
See Modes for guidance on which mode to pick for which task.
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.
BehaviorDescription
Default modelApplied to every new session unless overridden per run.
Per-run modelSet on individual runs to test different models without changing your default.
ResumeWhen you continue a previous session, Mains re-applies your model and mode settings.

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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. See Permissions for the full approval flow and how to pre-approve tools.