Immune is an MCP firewall with a memory. It sits between any agent and its tool servers and catches poisoned tool descriptions, injected results and secret exfiltration. When a novel variant gets through, it synthesizes a countermeasure, proves it by replaying the whole corpus in ClickHouse, rescans with Semgrep, signs a receipt, publishes a ruling, and verifies that the same attack now bounces. Headline metric: Time to Immunity, in seconds.