Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
ElsewhereArea: what it touches
Internal ChangesKind: in v2.1.301,
Internal ChangesSection of the release
What
Claude Code can record the requests it sends to the API so they can be replayed later. To do that it computes a fingerprint, called a hash, for each message in the conversation. Before this release, it recomputed every message's hash on every request.
It now remembers the hashes it has already computed and reuses earlier work. To catch mistakes, it checks one randomly chosen message each time. If that message's hash no longer matches the remembered one, Claude Code throws away everything it remembered and records the failure reason stale_hash.
Why
This cuts processing work in long sessions, where rehashing every message on every request adds up.
