Anthropic status: Model output quality (via) Anthropic previously reported model serving bugs that affected Claude Opus 4 and 4.1 for 56.5 hours. They've now fixed additional bugs affecting "a small percentage" of Sonnet 4 requests for almost a month, plus a less long-lived Haiku 3.5 issue:
Resolved issue 1 - A small percentage of Claude Sonnet 4 requests experienced degraded output quality due to a bug from Aug 5-Sep 4, with the impact increasing from Aug 29-Sep 4. A fix has been rolled out and this incident has been resolved.
Resolved issue 2 - A separate bug affected output quality for some Claude Haiku 3.5 and Claude Sonnet 4 requests from Aug 26-Sep 5. A fix has been rolled out and this incident has been resolved.
They directly address accusations that these stem from deliberate attempts to save money on serving models:
Importantly, we never intentionally degrade model quality as a result of demand or other factors, and the issues mentioned above stem from unrelated bugs.
The timing of these issues is really unfortunate, corresponding with the rollout of GPT-5 which I see as the non-Anthropic model to feel truly competitive with Claude for writing code since their release of Claude 3.5 back in June last year.
Recent articles
- Recreating the Apollo AI adoption rate chart with GPT-5, Python and Pyodide - 9th September 2025
- GPT-5 Thinking in ChatGPT (aka Research Goblin) is shockingly good at search - 6th September 2025
- V&A East Storehouse and Operation Mincemeat in London - 27th August 2025