HTTP error triage

An HTTP error tells you a request failed. It usually does not tell you why. Concluding "the key is dead" from a 403 is a guess wearing a number.

Born from a real incident (2026-07-30): a third-party contact-enrichment API returned 403 error code: 1010 to every call for six days. It was read as "key not entitled", "credits exhausted", "monthly quota reached". A 756-line browser automation workaround was built on that belief, and a customer was nearly asked to check a plan that was fine. The actual cause was a missing User-Agent, so the CDN banned the client at the edge. One header fixed it: 200 OK, full data, and the credit balance had been there the whole time.

Run these three controls before you diagnose

1. The invalid-credential control. Send the same request with a deliberately garbage credential, and again with none at all.