Choose Edit ▸ Preferences… (Ctrl+K). View ▸ Units & Increments…, Type ▸ Text Preferences… and View ▸ Grids & Guides ▸ Grid Preferences… open the matching section directly.
The upper sections (General, File Handling, Display Performance, AI, MCP Server, Debug) are preferences of the app and take effect as you change them; the Document sections below (Units & Increments, Guides & Pasteboard, Grids, Type, Dictionary, Transparency, Text Defaults) belong to the open document and are applied with their Apply button. The preferences of the app are kept for your Windows account, in %LOCALAPPDATA%\MasterPage\settings.json.
Click Reset to Defaults… at the bottom of the Preferences window and confirm. General, File Handling, Display Performance, AI, MCP Server and Debug go back to the values Master Page starts with. Your AI keys, your prompt presets and the open document's preferences are not changed. No key needs to be held down at launch.
The AI Console (Window ▸ AI Console, Alt+F7) works with Claude or Gemini using your own key, entered in Preferences ▸ AI. The key is stored in Windows Credential Manager, never in a file, and only sent to the provider you chose.
Master Page can be driven by an AI assistant or any other MCP client. Turn on Allow external control in Preferences ▸ MCP Server; the section shows the configuration to paste into the client. The client starts masterpage.exe --mcp-stdio, which passes each command to the Master Page that is running on this PC; no network port is opened.
Window ▸ Workspace ▸ Reset Palette Locations puts the palettes back where they start; New Workspace… saves the current arrangement under a name.