MCP servers: register once, switch on per session

The agent always has the built-in desktop MCP server (screen, mouse, keyboard) and, unless its policy is Off, the sessionboxer one (The agent and Sessionboxer itself). You can give it more: register MCP servers once in Settings, then choose per session which ones are on.

• Global settings → MCP & connectors → MCP servers: Add server (a name, then either a command to run inside the box such as npx -y @modelcontextprotocol/server-github or uvx mcp-server-fetch, or the URL of an HTTP/SSE server, plus environment variables or headers) or Import JSON… and paste the {"mcpServers": {...}} block most servers document for Claude Desktop or Cursor. Mark values like tokens as secret: they are stored in ~/.sessionboxer/config.json, never shown again in the UI, and never end up in snapshot images. Default decides whether new sessions start with the server on.
• New session shows the registered servers as checkboxes.
• MCP in the session header shows how many servers are on and opens a switch per server. Toggle at any time: when the agent is idle it restarts in place and keeps the conversation; while it is working the change waits until the current turn ends (the button shows pending). The chat shows an MCP servers now: … marker when the set changes.

Servers running on your machine are reachable from the box: localhost in a URL means your machine, and host.docker.internal works too. node, npx, python3, uv/uvx and docker are available in the box for command-based servers.