EIP-712 signed, timestamped attestation binding an agentId, the keccak256 digest of a declared state, and the paying wallet; attestor key at /transparency, verify offline with ethers.verifyTypedData. MUST be invoked when an agent needs third-party, non-repudiable proof that a state or decision existed at a point in time (audit trails, hand-offs, escrow). Do NOT use for hardware TEE, zk proofs or on-chain EAS. Settles $0.040 USDC via x402 on Base; no charge on failure; receipts at /api/ledger.