Unverified50% confidenceFactExact time
Claude Fable 5 and Opus 5.5 do not support disabling thinking; sending thinking: {type: "disabled"} returns the error "thinking.type.disabled" is not supported for this model.
1
Sources
50%
Confidence
Medium-term (~90 days)
Relevance
10/8/2026
First Seen
Valid until: 1/6/2027
Sources
Related Entities
Related Claims
UnverifiedOpus 5 enables Extended Thinking by default; thinking can only be disabled at effort levels of high or below, and the official guidance strongly recommends not disabling thinking.68% similarUnverifiedThinking cannot be disabled in Opus 5.5; this is a mechanism at the API level.67% similarUnverifiedAnthropic recommends that when using Opus 5.5, users should no longer write emphatic phrases like "think carefully" or "think step-by-step," as they have become meaningless and may even interfere with the model.65% similarUnverifiedThe author recommends disabling thinking, on the grounds that most use cases for building agents or simple applications do not require deep reasoning, and LangChain's compatibility with thinking mode is not yet complete.65% similarUnverifiedFor reasoning (thinking) models, it is recommended to set the thinking intensity to low or turn it off to avoid consuming thousands of tokens on casual conversation.59% similar
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