Claude API cache diagnostics no longer require a beta header
Anthropic says cache diagnostics are out of beta on the Claude API. Requests can opt in with a diagnostics object, and Messages responses now include a diagnostics field that is null when diagnostics were not requested.
SessionWatcher editorial · Published · Updated · Source announcement: 2026-09-23
How to enable cache diagnostics
Anthropic's September 23, 2026 release notes say cache diagnostics are out of beta on the Claude API. To opt in, include the diagnostics object on a Messages request. The cache-diagnosis-2026-04-07 beta header is no longer required. Requests that continue sending the header work as before.
Sources: Anthropic release notes: 2026-09-23
What to expect in responses
Responses from POST /v1/messages now always include a diagnostics field. If the request did not include the diagnostics object, that field is null. If your integration parses Messages responses, account for the field being present even when you did not opt in to diagnostics.
Sources: Anthropic release notes: 2026-09-23
AI assisted reporting, checked against the linked official sources. Source pages checked 2026-09-30. Editorial process and corrections.