The Membrane is a self-hosted, fail-closed authorization gateway for AI agents with production write access. Every model and tool call needs a live, signed, time-bounded scope. Each allowed action writes a tamper-evident, hash-linked receipt. A replayed proof, a swapped model or an expired scope is refused; a broken chain severs the agent. Your keys, your models, your policy. Open source (Rust). Clone to a refused call in about five minutes, or watch a recorded replay in the browser demo.
