gating AI agent access to Coinbase x402 with policy enforcement

Coinbase x402 gives agents programmatic access to custodial accounts, which is powerful — and dangerous if the agent gets compromised.

the missing piece is a governance layer that enforces spending policies before the agent ever calls the x402 API.

here's how mnemopay handles it:

1. policy enforcement middleware — the agent doesn't call x402 directly. it calls mnemopay's governance API, which validates the transaction against your rules, then forwards approved transactions to x402.
2. per-counterparty spending caps — limit how much the agent can send to any single wallet address in a rolling 24h or 30d window.
3. counterparty whitelist — the agent can only pay addresses you've pre-approved.
4. two-phase commit — the agent proposes a payment, the policy engine validates it, then the transaction commits or aborts atomically.
5. merkle audit trail — every proposed and executed transaction gets logged in a tamper-evident chain.

if the agent tries to exceed a cap or pay an unapproved address, the transaction aborts and the attempt gets logged. if the agent gets compromised (prompt injection, logic bug, etc.), the governance layer acts as a circuit breaker.

this isn't just a safety feature — it's a compliance requirement under EU AI Act Article 12 for high-risk systems. the audit trail has to be immutable and exportable.

i built mnemopay to wrap x402 and other payment rails with policy enforcement as infrastructure. the SDK handles the governance logic so you don't have to roll your own for every agent project.

if you're building on x402, treat the governance layer as a first-class dependency, not a feature you add later.