When your account enters the usage-limit grace window (reported via anthropic-ratelimit-unified-grace-status and utilization headers), a persistent warning now appears in the session:
> [Usage limit reached — grace window active. Wrap up: finish or checkpoint; don't start subagents or long work.]
The grace state is tracked from anthropic-ratelimit-unified-grace-5h-utilization and anthropic-ratelimit-unified-grace-7d-utilization response headers. The signal is latched on first observation (grace > 0) and cleared when a subsequent response reports it back at zero.
Grace window message (search for "grace window active") and header names (search for "anthropic-ratelimit-unified-grace-5h-utilization")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.