Elevated error rates on Sonnet 4

Incident Report for Claude

Resolved

This incident has been resolved.
Posted Dec 17, 2025 - 11:20 UTC

Monitoring

A fix has been implemented and we are monitoring the results.
Posted Dec 17, 2025 - 11:13 UTC

Identified

The issue has been identified and a fix is being implemented.
Posted Dec 17, 2025 - 11:09 UTC

Update

We have identified that this affects only free tier claude.ai users.
Posted Dec 17, 2025 - 10:49 UTC

Investigating

We are currently investigating this issue.
Posted Dec 17, 2025 - 10:45 UTC
This incident affected: claude.ai and Claude API (api.anthropic.com).