Etch

Etch is a signed audit chain that captures every AI agent decision as a tamper-evident event: prompt, context, tools called, outcome. When production breaks, replay the exact chain. When a regulator or auditor asks six months later, verify the same record offline against pinned public keys with no dependency on Etch staying online. Events are signed with a hybrid Ed25519 + FIPS 205 SLH-DSA-SHA2-128f envelope, Merkle-chained into epochs, and anchored to Sigstore Rekor and Bitcoin OpenTimestamps. Free tier, MCP-native, works with any agent stack.