Surfil is an on-device control plane that installs beside AI coding agents such as Claude Code, Cursor, Codex, and Copilot to reduce token spend, block risky tool calls, and provide persistent memory across sessions. It intercepts agent traffic at a single local point, ensuring source code never leaves the device while producing Ed25519-signed, offline-verifiable receipts for every measured saving. Its modular product suite includes Cap for cost measurement, Guard for pre-flight secret and injection blocking, and Mind for portable encrypted agent memory. Surfil connects to editors via MCP and supports over 30 agents from one install, with uninstall restoring all original configs byte-for-byte.