# Anthropic: Claude Sonnet 4 degraded performance quality

> Anthropic status incident “Claude Sonnet 4 degraded performance quality” on 2025-07-10: impact none (vendor’s label), 0 min, 1 update(s). Archived by Rewindex.

Canonical: https://rewindex.com/company/anthropic/incidents/4q9qw2g0nlcb
Last updated: 2025-07-10T02:00:00Z

- Impact (vendor’s label): none
- Status: resolved
- Started: 2025-07-10 02:00 UTC · Resolved: 2025-07-10 02:00 UTC · Duration: 0 min
- Updates: 1
- [Vendor status page: https://status.anthropic.com/incidents/4q9qw2g0nlcb](https://status.anthropic.com/incidents/4q9qw2g0nlcb)
- [Company: Anthropic](https://rewindex.com/company/anthropic.md)

## Timeline of updates

- **resolved** 2025-07-10 02:00 UTC: 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 the vendor’s published history: only the final update text is available for incidents before Rewindex began polling this page._

## 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).

- Canonical URL: https://rewindex.com/company/anthropic/incidents/4q9qw2g0nlcb
- Citation: Anthropic, “Claude Sonnet 4 degraded performance quality” (2025-07-10 02:00 UTC). Archived by Rewindex: https://rewindex.com/company/anthropic/incidents/4q9qw2g0nlcb (CC BY 4.0).
- Markdown link: `[Anthropic: Claude Sonnet 4 degraded performance quality (2025-07-10)](https://rewindex.com/company/anthropic/incidents/4q9qw2g0nlcb)`


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Canonical: https://rewindex.com/company/anthropic/incidents/4q9qw2g0nlcb · Markdown: https://rewindex.com/company/anthropic/incidents/4q9qw2g0nlcb.md · JSON: https://rewindex.com/api/v1/companies/anthropic/incidents/4q9qw2g0nlcb · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-11-04T18:04:15.533Z