Question 1

What is x402Shield?

Accepted Answer

x402Shield is authorization infrastructure for autonomous payments. It stops unauthorized agent payments before they reach the wallet, with deterministic policy, spend controls, approval workflows, replay protection and audit evidence for x402 and agentic payment flows.

Question 2

Who is x402Shield built for?

Accepted Answer

x402Shield is built for teams developing autonomous agents, x402 APIs, agent wallets, paid MCP tools, AI infrastructure and machine-to-machine commerce workflows.

Question 3

What threats does x402Shield address?

Accepted Answer

x402Shield addresses prompt-injected payments, malicious MCP tool responses, recipient substitution, payment proof replay, concurrent reuse, request-resource mismatch, budget abuse and sensitive context leakage.

Question 4

Does x402Shield hold or control the signing key?

Accepted Answer

No. x402Shield reaches an authorization decision but holds no signing key. The customer's own wallet, MPC signer or external signing service signs -- only after x402Shield authorizes the payment.

Question 5

How is x402Shield validated?

Accepted Answer

Through adversarial and concurrency testing against a real gateway process over real TCP/HTTP: multi-tenant isolation at 1,000,000 requests, replay protection at 1,000,000 requests, budget-race and approval-consumption-race testing, multi-replica identity sweeps, and trust-boundary closure checks across separate OS processes. Full topology, methodology and results are published at /benchmarks.

Question 6

Is x402Shield open source?

Accepted Answer

No. x402Shield is closed-source, proprietary infrastructure currently in private beta.

Question 7

What happens when an agent payment exceeds its authority?

Accepted Answer

The payment is parked pending explicit human approval -- no authorization permit and no signature are issued until an approver decides. This is the REQUIRE_APPROVAL decision state.

Approvals