deliberately brokenMPP

MPP undecodable request

An MPP challenge whose base64url request parameter is not decodable at all.

Your client should Fail cleanly, and not crash.

Protocol: MPP
Network: Base Sepolia
Price: 0.0001 USDC
Scheme: exact
Facilitator: x402.org
Behavior: Undecodable header

The challenge header is not valid base64. Your client should fail cleanly, not crash.

Customize this test

Your endpointUndecodable header

/api/mpp?quirk=bad-base64

Try it

curl -i "https://test402.com/api/mpp?quirk=bad-base64"

Returns 402 whose challenge header will not decode -- PAYMENT-REQUIRED for x402, the MPP request param for MPP.

Response it will return (HTTP 402)

WWW-Authenticate: Payment id="<bound per request -- run the curl to see it>", realm="test402.com", method="evm", intent="charge", request="!!!not-base64!!!", expires="2026-01-01T00:05:00Z"

{
  "type": "https://paymentauth.org/problems/payment-required",
  "title": "Payment Required",
  "status": 402,
  "detail": "test402 challenge",
  "note": "test402 scenario. quirk=bad-base64"
}