Anthropic says outdated prompting habits are slowing down Claude Opus 5.5

Anyone using Claude Opus 5.5 should first drop several prompting habits carried over from older model generations, according to Anthropic.

Anthropic says the model, now the default on Pro, Max, Ultra, and Team plans, works differently from its predecessors and that many users hold it back with outdated instructions.

Topping the list is Anthropic's advice to cut phrases like "think hard" or "think carefully" from prompts. According to the company, the model always reasons on its own and scales its reasoning depth to the task and the selected effort level. In Anthropic's tests, responses without these phrases started faster with no measurable drop in quality.

These phrases date back to the early days of reasoning models, before today's standard adaptive reasoning existed. "Back then," meaning about a year and a half ago, users could sometimes coax more performance out of a model or steer the router this way.

Anthropic also recommends starting at the "Medium" effort level, the default for Opus 5.5. In internal tests, Opus 5.5 on Medium matched the performance of its predecessor Opus 5 on "High," the company says. Higher settings cost more and don't always produce better results. Anthropic advises switching to "High" only when Medium isn't enough, and users can change the setting in the model menu next to the send button.

Teams that previously used the cheaper Sonnet and reserved Opus for complex projects should rethink that approach, according to Anthropic. The company argues that a more capable model can finish a task in fewer steps, which can partly offset its higher per-token price. Anyone who regularly cranks Sonnet up to "Extra High" or "Max" effort ends up paying about as much as with Opus 5.5, Anthropic says.

From chatting to setting goals

Anthropic recommends attaching diagrams and tables as images or files instead of typing them out. Workarounds that older models required, such as manually transcribing chart values, are no longer needed, the company says.