New model guide · September 22, 2026
10 Things You Can Do With Claude Opus 5.5
Opus 5.5 is built for substantial coding and knowledge-work tasks. Here are ten useful ways to put it to work, with prompts that keep the output reviewable.
Claude Opus 5.5 is available now in Claude, Claude Code and the Claude Platform. Anthropic calls it the first model in the Claude 5.5 family and says it leads its reported evaluations in agentic coding, computer use and knowledge work.
The practical upgrade is not just a higher benchmark score. Anthropic says typical workloads cost 40% less than Opus 5, output is generated more than 30% faster, and communication is clearer. API pricing at launch is $4 per million input tokens and $20 per million output tokens; cache reads are $0.20 per million tokens. Fast mode is available at a higher price.
Those are Anthropic's launch claims, and real results will vary with the task, tools, effort setting and review process. The ten ideas below are best treated as workflows to test—not guarantees that a model can replace accountable professional judgment.
1 of 10
Modernize a large codebase
Use Opus 5.5 to map dependencies, plan a staged migration, change code in reviewable batches and run the project’s tests after each batch. This is the kind of sprawling work Anthropic highlights: one early tester reportedly completed a 680,000-line migration in less than a day. Treat that as an example, not a promise for every repository.
Try this prompt
Inspect this repository and propose a staged migration from [current stack] to [target stack]. First map dependencies and risky boundaries. Do not edit anything yet. Give me acceptance tests, rollback points and a batch plan small enough to review.
2 of 10
Audit software and fix performance bottlenecks
Ask the model to profile a slow application, trace expensive paths and suggest fixes that preserve behavior. Anthropic says Opus 5.5 is better at finding and correcting inefficiencies across a whole app. Give it measurements, logs and tests; do not ask it to infer performance from source code alone.
Try this prompt
Find the causes of these slow page loads using the attached traces and repository. Rank findings by measured impact. For each proposed change, state the behavior that must remain unchanged and the test that will prove it.
3 of 10
Build a working prototype from a product brief
Turn a rough idea into a small app, internal tool or game. Opus 5.5 can help translate requirements into screens, data flows, code and a test checklist. Start with one end-to-end user journey; a polished narrow prototype is easier to evaluate than a giant one-shot build.
Try this prompt
Build a narrow prototype for [idea]. The primary user is [user], and the one journey that must work is [journey]. Before coding, write five acceptance criteria and identify any decisions you need me to make. Keep the architecture simple and test the completed flow.
4 of 10
Research a difficult question and produce a sourced report
Give Opus 5.5 access to approved web or internal sources, then ask it to locate evidence, reconcile conflicts and produce a report with citations. Anthropic reports strong results on research tasks where every figure and quotation was checked. You should still open the cited sources and verify consequential claims yourself.
Try this prompt
Research [question] using primary sources published after [date]. Create a claim table with the exact source URL, publication date, supporting evidence and confidence. Flag disagreements and missing evidence. Draft the report only from claims that survive that check.
5 of 10
Analyze spreadsheets and build a financial model
Use the model to inspect a workbook, identify assumptions, repair formulas, run scenarios and explain the result. Anthropic tested Opus 5.5 on a fictional merger analysis that moved from an Excel model to an executive recommendation. For real financial decisions, keep a human owner for inputs, formulas and sign-off.
Try this prompt
Audit this workbook before changing it. List input cells, formulas, hidden assumptions, broken references and reconciliation checks. Then create base, upside and downside scenarios. Keep assumptions separate from calculations and show every changed cell.
6 of 10
Turn analysis into an executive presentation
Ask Opus 5.5 to turn a detailed report or model into a short decision deck. It can select the evidence, build a narrative and draft slide content while keeping the recommendation tied to the analysis. Give it an audience, decision and slide limit so the result does not become a generic summary.
Try this prompt
Turn this analysis into an eight-slide decision deck for [audience]. Lead with the decision, then evidence, trade-offs, risks and next steps. Every number must trace to a named table or source. Add speaker notes for nuance that should not crowd the slides.
7 of 10
Automate a multi-step business workflow
With the right tools and permissions, Opus 5.5 can collect information, update systems and prepare a finished deliverable across several steps. Good candidates include weekly reporting, customer-feedback triage and document intake. Start in read-only mode, require confirmation before external or irreversible actions, and log what the agent changes.
Try this prompt
Design a workflow for [process]. Separate read-only steps from actions that change data or contact people. Pause for approval before every external, financial or irreversible action. Produce an audit log with sources, tool calls, changed records and unresolved exceptions.
8 of 10
Collect and compare information at scale
Use Opus 5.5 to assemble a structured dataset from many documents or approved web pages, deduplicate records and explain discrepancies. Anthropic reports gains on large-scale data collection evaluations. Define the schema first and retain a source beside every row so errors remain traceable.
Try this prompt
Collect [fields] for [entities] from these approved sources. Define the schema and validation rules before extraction. Preserve a source URL and quoted evidence for every record, mark missing values as unknown, and send ambiguous matches to an exceptions table.
9 of 10
Coordinate a long-running project
Break a complicated goal into parallel workstreams, maintain a decision log and resume from checkpoints instead of restating the entire project. This can help with repository-wide changes, due diligence or launch preparation. Keep authority bounded: the model should surface decisions, not quietly make high-impact choices for you.
Try this prompt
Create a project plan for [goal] with workstreams, dependencies, owners, checkpoints and a definition of done. Maintain a decision log and an assumptions register. At each checkpoint, summarize completed evidence, failed attempts, open risks and the smallest next action.
10 of 10
Rewrite dense material in a clear house style
Opus 5.5 is designed to put the important point first, use less jargon and follow writing rules more closely. Use it to turn a long thread into an update, explain a technical change or revise a design document. Supply real examples of your preferred style and ask it to preserve facts rather than embellish them.
Try this prompt
Rewrite this for [audience] in our house style. Put the decision and its impact first, use plain language, preserve every factual qualifier, and remove repetition. Do not add facts. End with owner, deadline and next step only when they appear in the source.
How to choose the right Opus 5.5 effort level
Start at the default setting for ordinary work. Increase effort when the task has many dependencies, ambiguous evidence or a costly error. For repeatable production workflows, test several effort levels on the same representative task set and compare quality, latency, token use and review time. A more expensive setting is useful only when the result improves enough to justify it.
Where human review still matters
Check citations against the original source, recalculate important numbers, run code in an isolated environment, inspect diffs and require an accountable person to approve legal, financial, medical, security or personnel decisions. Anthropic says Opus 5.5 is less likely to take hard-to-reverse actions and is more resistant to prompt injection than Opus 5, but its announcement also says the model still has limits.
Be especially careful when a task mixes untrusted web content with tools that can change systems. Limit permissions, keep sensitive data out unless your organization has approved the product and configuration, and make irreversible actions require explicit confirmation.
Bottom line
Opus 5.5 looks most useful when the job is too large for a one-shot chat: a repository migration, a research trail, a workbook-to-deck workflow or a multi-stage operational process. The winning pattern is to let the model do substantial work while keeping sources, tests, checkpoints and final authority visible to a human.
Primary sources
Pricing, limits and availability can change. Verify the live Anthropic pages before making a purchase or production commitment.