x402Shield is authorization infrastructure for autonomous payments. It evaluates and authorizes agent payment intent before wallet signing, with deterministic policy enforcement, spend controls, approval workflows, replay protection, and audit evidence for x402 and agentic payment flows.

• Deterministic Policy Enforcement: Define and enforce granular rules for agent spending, including limits on transaction amounts, budgets, allowed assets, networks, and recipients.

• Pre-Signing Authorization: x402Shield intercepts payment requests and enforces defined policies *before* a wallet or MPC signer is prompted to sign, preventing unauthorized transactions.

• Spend Controls and Approvals: Implement transaction limits, daily budgets, and set approval thresholds that require human intervention for exceptional payments.

• Replay Protection: Ensures that payment requests cannot be replayed, preventing duplicate transactions.

• Audit Evidence: Every authorization decision generates a hash-linked record detailing what was checked, authorized, signed, and observed, providing a clear audit trail.

• Separation of Concerns: Authorization, permit issuance, and payment signing are handled by distinct services with separate keys, enhancing security.

• Customizable Signing Infrastructure: Integrates with customer-controlled signing solutions, including browser wallets, MPC signers, and external signing services, while maintaining custody of keys.

• Landscape Comparison: Offers a detailed comparison with other agent payment and wallet infrastructure products, highlighting unique capabilities.

x402Shield is designed for teams building autonomous agents, x402 APIs, agent wallets, paid MCP tools, AI infrastructure, and machine-to-machine commerce workflows. It addresses threats such as prompt-injected payments, malicious MCP tool responses, recipient substitution, and payment proof replay.