In the Claude Opus+Sonnet 4 and Claude Sonnet 4.5 system cards, it was stated that Anthropic usually shares the full reasoning trace, with the exception of a small fraction of prompts where the reasoning trace is too long, after which it is summarized. From what I remember, the reasoning traces of those models usually looked legible.
They’ve removed this language from the recent Opus 4.5 and 4.6 system cards, which makes me think it is now likely summarized a larger fraction of the time or even all the time.
In the Claude Opus+Sonnet 4 and Claude Sonnet 4.5 system cards, it was stated that Anthropic usually shares the full reasoning trace, with the exception of a small fraction of prompts where the reasoning trace is too long, after which it is summarized. From what I remember, the reasoning traces of those models usually looked legible.
They’ve removed this language from the recent Opus 4.5 and 4.6 system cards, which makes me think it is now likely summarized a larger fraction of the time or even all the time.