gcp

   | jq -rR 'split(".")[1] | gsub("-";"+") | gsub("_";"/") | @base64d | fromjson'
 ```
 
-Check that `iss` is `https://accounts.google.com`, `aud` is `https://api.anthropic.com`, and `email` matches the value in your federation rule. Then run the exchange from the previous section. A successful exchange returns an `access_token` beginning with `sk-ant-oat01-` and an `expires_in` value in seconds. On `400 invalid_grant`, see [Troubleshoot a failed exchange](https://platform.claude.com/docs/en/manage-claude/wif-reference#troubleshoot-a-failed-exchange); the most common Google Cloud-side cause is the `email` claim missing (request the token with `format=full` so it is included).
+Check that `iss` is `https://accounts.google.com`, `aud` is `https://api.anthropic.com`, and `email` matches the value in your federation rule. Then run the exchange from the previous section. A successful exchange returns an `access_token` beginning with `sk-ant-oat01-` and an `expires_in` value in seconds. If the exchange fails with the opaque `401` `authentication_error` response (message `Authentication failed`), check the [authentication history page](https://platform.claude.com/settings/workload-identity-federation?tab=history) for the deny reason and see [Troubleshoot a failed exchange](https://platform.claude.com/docs/en/manage-claude/wif-reference#troubleshoot-a-failed-exchange); the most common Google Cloud-side cause is the `email` claim missing (request the token with `format=full` so it is included).
 
 ## Scope your rule