Anthropic Publishes Prompting Guidance For Claude Opus 5.5 via @sejournal, @MattGSouthern
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SEJ ⋅ AI Search Anthropic Publishes Prompting Guidance For Claude Opus 5.5 Anthropic published a prompting guide for Claude Opus 5.5. It says to test effort levels again instead of reusing Opus 5 settings. In its tests, removing a "think carefully" instruction made chat replies start sooner. Anthropic's Claude Opus 5.5 prompting guide asks developers to retest effort settings and reconsider chat prompt lines telling Claude to think carefully. SEJ STAFF Matt G. Southern 2 hours ago ⋅ 4 min read SEJ STAFF Matt G. Southern Senior News Writer at Search Engine Journal Bio Follow Anthropic’s prompting guide for Claude Opus 5.5 advises developers to test multiple effort levels instead of reusing the setting used in Claude Opus 5. It also suggests chat applications remove system-prompt lines instructing Claude to think carefully before responding. Opus 5.5 launched Sept. 22. The guide says Opus 5 prompts should still work well without edits, and that the company’s Opus 5 guidance is a reasonable place to start. When the company tested this in a chat product, removing a think-carefully line made replies start sooner, with “no clear decline in the quality of the reply.” Opus 5.5 runs at medium effort by default, one level below the high default on Opus 5. Thinking can’t be turned off on Opus 5.5, and requests that try get an error. Opus 5 allowed that at high effort or below. The guide calls effort the first setting to adjust when balancing quality against speed and cost. In Anthropic’s testing, Opus 5.5 at medium effort matches or even surpasses Opus 5 at high effort when it comes to coding and knowledge work. To cut thinking, the guide says to try lower effort settings before prompt changes, and save the higher levels like xhigh and max for tasks where they really make a difference in quality. The guide’s reason for suggesting chat apps reconsider think-carefully lines is that Opus 5.5 decides for itself how much to think, with effort as the main control. Anthropic’s own docs include that kind of line. For Claude Opus 4.7, when effort has to stay low to keep responses quick, its page on effort suggests adding guidance such as “This task involves multistep reasoning. Think carefully before responding.” For agent teams, the guide recommends using a time budget based on how long tasks might take. With Opus 5.5, the software helps by tracking elapsed time. Anthropic’s tests have shown that small agent groups, when using time signals, finish research tasks quicker than a single agent working without signals. Even under time budgets, these groups managed to achieve answer quality comparable to solo agents. The guide emphasizes that the time budget is just a suggestion, and setting a strict timeout can be quite helpful. The model might perform slightly less thoroughly under pressure. For users who input text from sources like emails, the guide suggests using tags with a random ID and adding a system note on how to manage tagged text. This approach encourages careful handling and, since tags are plain text that can be copied, they provide only one layer of protection against prompt injection. What Anthropic says to retest, remove, and add when prompting Opus 5.5 Opus 5Opus 5.5 Don’t assume your Claude Opus 5 setting is still the right one for Opus 5.5. EffortPromptFirst Anthropic says effort is the first setting to adjust when balancing quality, speed, and cost. Consider removing ‘think carefully’ in chat prompts “think carefully” In Anthropic’s chat-product testing, removing that instruction made replies start sooner. Anthropic said there was ‘no clear decline’ in reply quality. For multiagent workflows with a sensible task estimate, Anthropic recommends passing elapsed time against that budget. Instructions<…>Pasted text</…> Anthropic recommends marking pasted content and telling Claude how to treat it. It describes this as one guardrail against prompt injection, not a full defense. Several sections of the Opus 5.5 guide ask developers to re-check setup carried over from older models, such as workarounds for reading charts and screenshots, or instructions written for running with thinking off. The Fable 5.1 guide, which Roger Montti covered earlier this month, asked developers to revisit formatting rules. An app that never sets effort runs at medium on Opus 5.5 without any code change. Using an output cap (max_tokens) for Opus 5 with ‘thinking off’ might cut responses off on Opus 5.5. The guide mentions that ‘thinking’ uses some of that cap even when you don’t see it. For frontend projects, the Opus 5.5 guide recommends setting clear styles to avoid defaults like cream backgrounds and pill-shaped buttons. Vague requests to steer clear of a generic AI look often just switch one default for another. Add SEJ as a preferred source on Google Read Full Bio SEJ STAFF Matt G. Southern Senior News Writer at Search Engine Journal Follow on YouTube. Matt G. Southern is the Senior News Writer at Search Engine Journal, where he’s covered Google, SEO, ... Breaking news and insights to help you lead search strategies. Trending Content Output Compared In ChatGPT, Gemini, And Claude How To Write ChatGPT Prompts To Get The Best Results Introducing SEOntology: The Future Of SEO In The Age Of AI The AI Search & SEO News That Matters Breaking news and insights to help you lead search strategies. Breaking news and insights to help you lead search strategies. In a world ruled by algorithms, SEJ brings timely, relevant information for SEOs, marketers, and entrepreneurs to optimize and grow their businesses -- and careers.
Source: Search Engine Journal
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