x402 client checklist

You can see status 402, not only a generic network error. If the browser hides it, you have a server-side or curl path.

All four are present on the requirement you intend to pay.

The asset address is USDC (or the token you expect) on that network, not a lookalike.

maxTimeoutSeconds gives the wallet enough time to sign and submit.

After paying, the client can send the payment header and read the 200. CORS is solved for that hop too.

A human or an explicit policy confirms payTo and amount before any signature.

You compared a paid response with the challenge so a still-402 is not treated as success.