{"slug": "opus-5-5-is-probably-still-nerfed", "title": "Opus 5.5 is probably still nerfed", "summary": "An analysis of reported reasoning tokens per request found that Anthropic's Opus 5.5 likely remains nerfed after the November 9 launch of Fable 5.2, with a bootstrap test comparing before and after the Fable release yielding p=0.105. The finding follows an earlier blog post theorizing that Opus 5.5's reduced output stemmed from testing of Fable 5.2, a theory the new data cannot confirm at conventional significance levels.", "body_md": "# Opus 5.5 is probably still nerfed\n\nA few days ago, [I wrote about Opus 5.5 being nerfed](https://micjm.com/blog/get-ready-for-fewer-opus-5.5-em-dashes/). One theory was that this was because of testing Fable 5.2, so I wanted to check again, since [Fable has now launched](https://www.anthropic.com/claude-fable-and-mythos-5-2).\n\nHere’s a chart of Opus 5.5’s reported reasoning tokens per request, relative to alternative models in the same battles. The vertical line is the Fable release date, November 9:\n\nFrom our data alone, we can only say that it’s likely that Opus is still nerfed. The p-val on the bootstrap test of before and after the Fable launch is p=0.105.", "url": "https://wpnews.pro/news/opus-5-5-is-probably-still-nerfed", "canonical_source": "https://micjm.com/blog/opus-5.5-after-fable/", "published_at": "2026-11-13 18:00:00+00:00", "updated_at": "2026-11-13 22:58:37.939296+00:00", "lang": "en", "topics": ["large-language-models", "artificial-intelligence", "ai-research"], "entities": ["Anthropic", "Opus 5.5", "Fable 5.2"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/opus-5-5-is-probably-still-nerfed", "markdown": "https://wpnews.pro/news/opus-5-5-is-probably-still-nerfed.md", "text": "https://wpnews.pro/news/opus-5-5-is-probably-still-nerfed.txt", "jsonld": "https://wpnews.pro/news/opus-5-5-is-probably-still-nerfed.jsonld"}}