What
When a request to the API fails, the server sends back a status number. Numbers from 400 to 499 usually mean something was wrong with the request itself. Before, Claude Code skipped the automatic retry only for 404 (not found). Now it skips the retry for every status from 400 to 499 except these three, which are still retried:
408: the request timed out409: a conflict429: too many requests
Why
Retrying a request that cannot succeed only adds waiting. Failures like these should now reach you straight away, while the three temporary cases still get another try.