Compositional Security for Blockchain-Based Agentic Commerce: Cross-Layer Binding, Predicate-Constrained Settlement, and Evidence-Linked Verification in AI-Agent Payments

Plain-English abstract

Four standards are converging to let AI agents pay — ERC-8004 (identity), AP2 (authorization), x402 (settlement), ACP (checkout). Each secures its own layer. None binds them. So the agent you trusted isn’t necessarily the key that paid, and a mandate for $2 can settle for $3. CLB-ACEL binds identity, authorization, and settlement in one EIP-712 commitment, derives the payment nonce from it, and enforces the human’s spending predicate on-chain — a violating delegated payment reverts on Base Sepolia instead of being flagged after the fact. Formally verified in Tamarin. Running live with real agents.