Anthropic makes Claude Opus 5.5 default, tells users to drop "think hard"
Anthropic has made Claude Opus 5.5 the default model on all paid plans and published a prompting guide that advises retiring older habits. The headline recommendation is to stop using instructions like “think hard” and instead start at Medium effort. The Decoder’s report relays Anthropic’s own announcement and does not include benchmarks or measurements showing how much the older prompting style actually costs users. The guidance is therefore a vendor recommendation rather than an independently verified result.
Why old prompting habits carried over
Earlier Claude models required explicit instructions such as “think hard” to trigger deeper reasoning, so users built prompts around coaxing more deliberation out of the model. Anthropic’s guidance for Opus 5.5 describes a different setup: thinking is always on, reasoning depth is set through effort levels from low to max, and the model defaults to medium effort. One analysis of those levels reports that Opus 5.5 at medium effort beats Opus 5 at high effort, which is why guidance now points users to start at medium rather than pushing for maximum reasoning.
Impact
Paid-plan users will now reach Opus 5.5 without selecting it, so existing prompts and saved templates that lean on “think hard” phrasing should be re-checked against the new Medium-effort starting point rather than carried over unchanged.
