As of 1:05 PT / 8:05 UTC the errors are back to the baseline.
Update · UTC
This incident has been resolved.
Resolved · UTC
We saw an elevated number of errors on Claude 4 Sonnet starting at 06:00 PT / 13:00 UTC, having a peak at around 08:30 PT / 15:30 UTC, and being resolved at 09:05 PT / 16:05 PT.