GoKawiilUsers report altered reasoning behavior in Anthropic's Claude Opus model since Nov 3
A user-submitted post claims that Anthropic's Claude Opus (referred to as 'Opus 5.5') began showing changed 'thinking patterns' starting November 3, with some users describing it as 'nerfed.' The post argues that the earlier common advice to set reasoning effort to 'high' for all tasks may no longer hold given this shift.
GoKawiil's interpretation of the reporting above, not reported fact.
Anthropic has not issued a statement confirming any change, so this appears to be based on user observation rather than confirmed facts, which means the claim should be treated cautiously. If true, it could suggest Anthropic is quietly adjusting model behavior or compute allocation without public disclosure, which could affect how developers configure prompts and reasoning settings. Such unannounced tuning, if it occurs, raises broader questions about transparency in how AI labs manage model versions post-release.
- A user report claims Claude Opus's reasoning behavior changed around November 3
- No official confirmation from Anthropic has been cited
- Advice to always use 'high' reasoning effort may need reconsideration, according to the poster
Source: twitter.com, 2026-11-09
Published there as: “Is Opus 5.5 nerfed? Thinking patterns changed on November 3”
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