Anthropic: Claude Sonnet 4 degraded performance quality
Timeline of updates
- resolved
From 08:45 UTC on July 8th to 02:00 UTC on July 10th, Claude Sonnet 4 experienced a degradation in quality for some requests. Users, especially tool use and Claude Code users, would have seen lower intelligence responses and malformed tool calls. This was caused by a rollout of our inference stack, which we have since rolled back. While we often make changes intended to improve the efficiency and throughput of our models, our intention is always to retain the same model response quality.
From Anthropic’s published incident history: for incidents before Rewindex began polling this status page, only the final update text is available.
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This incident predates live tracking (October 17, 2026). It came from the vendor’s own published history, which is not covered by checkpoints.
Impact, status and times are the vendor’s own, as last archived. View on status.anthropic.com (opens in new tab).
Cite this
Status incident (vendor impact label: none) posted by Anthropic, started 2025-07-10 02:00 UTC, resolved after 0 min, 1 update(s).
- Title
- Claude Sonnet 4 degraded performance quality
- Vendor
- Anthropic
- Date
- URL
- https://rewindex.com/company/anthropic/incidents/4q9qw2g0nlcb
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