MCP servers at a URL that never expires

public: true on sbx.mcp.start (public=True in Python, Public in Go, --public in the CLI, public on POST /v1/sandboxes/{id}/mcp and the runtime_sandboxes_mcp tool) serves the sandbox's MCP servers at a public preview: URLs with no link token, so an agent is set up with them once. The Authorization header still guards every request, and stays the same at every start, after a restart too, until you stop the gateway. An idle sandbox pauses with its servers in memory and wakes on the next request. Reading the gateway no longer turns a public preview of its port back to private. Needs a kept top-up. See MCP servers.