Registration fails with 'Expected 402 response' despite valid 402 — api.strale.io/x402/iban-validate

[petterlindstrom79]

Problem

Registering https://api.strale.io/x402/iban-validate on x402scan.com/resources/register fails with:

Registration Failed — Failed to register all 1 resources
URL: https://api.strale.io/x402/iban-validate
Error: Expected 402 response

This happens with both "Add Server" and "Register This URL Only" buttons.

The endpoint returns a valid 402

Verified via curl:

$ curl -s -w "\nHTTP_STATUS: %{http_code}\n" "https://api.strale.io/x402/iban-validate"

{"x402Version":1,"paymentRequirements":[{"scheme":"exact","network":"eip155:8453","maxAmountRequired":"10000","resource":"https://api.strale.io/x402/iban-validate","description":"Validate IBAN numbers","mimeType":"application/json","payTo":"0x66D7C2F952362BFB24FD7F02a9beC9c754ea83bC","maxTimeoutSeconds":300,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"}],"error":"Payment required","accepts":[{"network":"eip155:8453","asset":"USDC","amount":"$0.01"}]}
HTTP_STATUS: 402

Full response headers:

HTTP/1.1 402 Payment Required
Content-Type: application/json
Payment-Required: eyJ4NDAyVmVyc2lvbiI6MSwi...  (base64 v1 payload)
Access-Control-Allow-Origin: *
Access-Control-Expose-Headers: Payment-Required,X-Payment-Response

What we have

• HTTP 402 status ✅
• Payment-Required header with base64 v1 payload ✅
• JSON body with paymentRequirements array (v2 format) ✅
• scheme: "exact" ✅
• network: "eip155:8453" (Base mainnet) ✅
• asset: USDC contract on Base ✅
• payTo: valid wallet address ✅
• Both GET and POST return 402 ✅

Environment

• Server: Hono on Railway (europe-west4)
• Agent card at /.well-known/agent-card.json
• TLS: Railway edge handles TLS, curl shows a renegotiation during handshake

Question

Is there something specific about the 402 response format that x402scan expects beyond the standard x402 spec? For example:

• Does x402scan require the header to be PAYMENT-REQUIRED (all-caps) instead of Payment-Required?
• Does it need a specific x402Version value (2 instead of 1)?
• Does it validate against a registered facilitator?
• Could TLS renegotiation be causing the probe to fail?

Happy to adjust our response format if needed. Thanks!