Cache diagnostics is out of beta on the Claude API and no longer requires the cache-diagnosis-2026-04-07 beta…
By Steven Van ·
Cache diagnostics no longer needs a beta header; opting in just requires adding a diagnostics object to a Messages request.
The Anthropic Claude API's cache diagnostics feature is now out of beta and no longer requires the cache-diagnosis-2026-04-07 beta header. Developers opt in by including the diagnostics object on a Messages request; requests that still send the old beta header continue to work as before. Responses from POST /v1/messages now always include a diagnostics field, which is null when the request didn't include the diagnostics object. When present, it reports where consecutive requests diverged, such as a changed model, system prompt, tools list, or message history, so developers can find why a prompt cache missed instead of guessing.