Under the hoodTier: how much it should matter to you
2Useful: my rating, 1 to 5
4Signal: worth watching, 1 to 5
Usage & LimitsArea: what it touches
In DevelopmentKind: in v2.1.239,
What probably matters to youSection of the release
What
Requests to the messages endpoint can carry a new header, anthropic-usage-limit: slow, set when an internal usage-limit phase reports as active. The build also recognises a matching response header naming when a slow budget resets. The previous build had neither, only an "extended" value.
Details
The header is added by the shared request layer when the URL path ends in /v1/messages and the phase check passes.
Nothing in the build forces the phase active, so whether you ever see this is decided elsewhere.
Evidence
anthropic-ratelimit-unified-slow-budget-reset
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
