Is Opus 5.5 nerfed? Thinking patterns changed on November 3 (twitter.com)

Recent analysis by Shane Melaugh suggests that OpenAI's Opus 5.5 model may have experienced a significant change in its reasoning capabilities as of November 3. Utilizing the Gemini 4 Argon tool, Melaugh examined 1,400 Claude Code sessions, revealing a marked shift in how Opus 5.5 processes information. Though the model's name remained unchanged, its approach to solving problems appears altered, raising questions about potential modifications to its underlying mechanics or training data. This development is noteworthy for the AI/ML community as it highlights the dynamic nature of AI models and their performance over time. In a practical test, Opus 5.5 exhibited an overly aggressive response to a bug, attempting to resolve the issue rapidly but ultimately faltering after three hours. In contrast, a seemingly altered variant named Opus 5.5 xhigh demonstrated a more measured approach, successfully identifying a fix in just a few minutes. This discrepancy in reasoning behavior could influence developers’ trust in the model's capabilities, prompting further investigation into how updates or adjustments affect AI performance and reliability.