Anthropic’s guide to using Opus 5.5 has one central rule: stop asking it to think. Eddie Osmani says Opus 5.5 already thinks before every answer and decides how much thinking is needed. “Think carefully” or “step by step” can delay the response without clearly improving quality. For simple questions, ask it to “answer directly”; in Claude Code, change effort level instead of the prompt.
The bigger shift is autonomy. Give long tasks in one message, define what “done” means and when it should stop for you. Early testers ran code for hours with little supervision. If you remember something, send another message while it works. For long projects, Anthropic recommends putting continuation/stop rules in CLAUDE.md and tracking tasks in TASKS.md, since chat history gets compressed. Ask the model to verify changes before human review and, for audits or migrations, split work among subagents and check each result.
Opus 5.5 also handles images better than Opus 5, including charts, calendars and schema changes. Don’t rewrite numbers from screenshots; ask it to deliver actual spreadsheets rather than plans. For research, have it note what it couldn’t verify and where it searched.
There’s also a safety change: Opus 5.5 launched with Fable-level protections for biological and cyber threats. Restricted messages are usually handed to an older model. In Claude Code, /fast provides earlier text at a higher per-token cost.
The overall advice: stop controlling every step and intervene only when the decision actually depends on you.