- When a sender's key cannot be fetched because its server timed out or answered 5xx, the inbox answers 503 with Retry-After: 300 instead of 401, so Mastodon 4.7 retries rather than switching to RFC 9421 signatures we do not verify yet. The fetcher's failure cache now remembers whether a failure was temporary. - Follow, Like, Block, Accept, Reject and Undo ids are deliberately not dereferenceable: serving them would publish who follows, likes and blocks whom. They are always sent with their object embedded. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB