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Anthropic — Most Capable Model · September 22, 2026

Claude Opus 5.5 Prompt Generator

20 free Claude Opus 5.5 prompts for frontier tasks — full codebase audits, legal contracts, research synthesis, security red-teams, and complex agentic workflows. Copy directly into Claude.ai or the API. No signup.

Frontier Reasoning Depth 1M Token Context Window 200-Page Document Analysis Advanced Agentic Tasks Released Sep 22 2026

What Is the Claude Opus 5.5 Prompt Generator?

This page gives you 20 copy-paste prompts built for Claude Opus 5.5 — Anthropic's most capable AI model as of September 22, 2026. Opus 5.5 is not a general-purpose model upgrade. It is a specialist for tasks where Claude Sonnet 5 at xhigh reasoning still falls short: full codebase audits spanning hundreds of files, 200-page legal and research documents, multi-step security red-team analysis, and complex agentic workflows requiring sustained decision-making across many sequential steps.

Each prompt is structured to extract the capabilities Opus 5.5 is uniquely suited for — deep reasoning chains, cross-document synthesis, adversarial analysis, and precision on highly constrained multi-part tasks. Paste any prompt into Claude.ai Pro/Max or the Anthropic API and fill in the bracketed placeholders with your specific context.

When to Use Claude Opus 5.5 vs Sonnet 5

Use Opus 5.5 for:
  • Full codebase audits (100+ files, architecture-level analysis)
  • Legal contracts over 50 pages requiring clause-level review
  • Research synthesis from 5+ papers or 200+ page documents
  • Adversarial red-team analysis and security threat modelling
  • Multi-stage agentic tasks requiring 10+ sequential decisions
  • Statistical model review requiring methodological depth
  • M&A due diligence and regulatory compliance audits
Use Sonnet 5 instead for:
  • Standard code review and debugging (Sonnet 5 xhigh is enough)
  • Emails, blog posts, and short-form writing
  • Data analysis on spreadsheets or short datasets
  • API documentation and standard technical writing
  • Competitive research on 2–3 sources
  • Interview prep, decision frameworks, and strategy memos
  • Anything where cost is a constraint — Sonnet 5 is much cheaper

20 Free Claude Opus 5.5 Prompts — Copy & Paste

Optimised for Claude Opus 5.5 on Claude.ai Pro/Max or the Anthropic API.

F
Coding frontier

Full Codebase Architecture Audit

Perform a deep architecture audit of this codebase. Review for: 1. STRUCTURAL ISSUES — tight coupling, circular dependencies, god objects, missing abstraction layers 2. SECURITY — injection risks, authentication gaps, secret exposure patterns, insecure defaults 3. SCALABILITY — bottlenecks that will break under 10× current load 4. MAINTAINABILITY — naming inconsistencies, undocumented invariants, dead code 5. DEBT RANKING — list every issue in priority order: what to fix first, what to schedule, what to live with For each issue: the file/function involved, a one-paragraph explanation of why it matters, and the minimum code change to resolve it. [Paste your codebase or key files]

L
Legal frontier

Legal Contract Deep Review

Review this contract as an expert attorney with a focus on protecting the party named as [Client / Counterparty]. Contract type: [SaaS agreement / employment / NDA / partnership / other] Our role: [which party are you representing?] Identify: 1. UNACCEPTABLE CLAUSES — clauses that create material legal or business risk (rate each: critical / high / medium) 2. MISSING PROTECTIONS — standard clauses that are absent and why their absence matters 3. AMBIGUOUS LANGUAGE — phrases that a court could interpret against our favour 4. NEGOTIATION LEVERAGE POINTS — the 5 clauses most likely to be negotiated and our fallback positions 5. RED-LINE SUMMARY — a plain-English paragraph describing the overall risk profile Present findings as a structured memo a non-lawyer senior executive can act on. [Paste your contract text]

R
Research frontier

Research Synthesis — 200-Page Document

I am attaching a [200-page report / large academic paper / full book / regulatory document]. Synthesise it into a structured briefing for a senior decision-maker with no time to read the full document. Audience: [who will read this — CEO, regulator, investor, researcher, etc.] Decision it informs: [what decision does this research support?] Deliver: 1. EXECUTIVE SUMMARY — 3 paragraphs: the core argument, key evidence, and practical implication 2. TOP 10 FINDINGS — bulleted, ordered by relevance to the decision 3. METHODOLOGY CRITIQUE — 3 limitations of the research the reader should know before acting on it 4. COMPETING VIEWS — are there credible counter-arguments this document underweights? 5. ACTION BRIEF — the single most important thing to do with this information, and by when Do not omit any finding that directly contradicts the report's main conclusion. [Paste your document]

M
Coding hard

Multi-File Refactor Plan

Plan and execute a refactor of the following multi-file module. The goal is [describe goal: e.g. 'migrate from class-based to functional React components', 'extract a shared utility layer', 'replace a REST API client with a GraphQL client']. Constraints: - Zero breaking changes to the public API - All existing tests must still pass - Incremental — the codebase should be deployable at each step Deliver: 1. A step-by-step migration plan with each step as a standalone PR (safe to merge independently) 2. The exact code changes for Step 1, ready to commit 3. The test I should write to confirm Step 1 is safe before Step 2 4. The 3 places most likely to cause a regression and why Files to refactor: [Paste your files]

A
Security frontier

Adversarial Red-Team Analysis

Act as an adversarial red-team analyst. Your goal is to identify every realistic way the following system could be exploited, broken, manipulated, or abused — including ways the designers did not anticipate. System description: [describe your system — its purpose, users, data it handles, trust boundaries] Attacker profile: [who are the most plausible adversaries — script kiddies, insiders, nation-state actors, financially motivated attackers?] Report structure: 1. ATTACK SURFACE MAP — every entry point and trust boundary, with a risk score (1–10) 2. TOP 5 ATTACK SCENARIOS — each with: attack vector, pre-conditions, impact, and detection difficulty 3. CASCADING FAILURE ANALYSIS — how one breach enables the next 4. BLIND SPOTS — threats the current design philosophy is most likely to underestimate 5. PRIORITY HARDENING ACTIONS — the 3 changes that eliminate the most risk for the least cost Be specific and concrete. Do not recommend generic 'use encryption' advice.

S
Research hard

Scientific Literature Review

Conduct a systematic literature review of the following research question. Treat the provided papers as the complete corpus. Research question: [your question] Discipline: [field] Audience: [who will read this review — academics submitting a paper / practitioners making decisions / policymakers?] Deliver a structured review: 1. SEARCH STRATEGY — how this corpus addresses the question (or doesn't) 2. THEMES — 4–6 major themes across the literature, with supporting citations and a brief synthesis of each 3. CONSENSUS — what the field broadly agrees on, with confidence level (strong / moderate / weak) 4. DISAGREEMENTS — the 3 most significant debates, with the strongest arguments on each side 5. GAPS — where the literature is silent or methodologically weak 6. FUTURE DIRECTIONS — the 2 most important unanswered questions 7. FORMATTED REFERENCES — in [APA / MLA / Chicago / Vancouver] format [Paste your papers or abstracts]

S
Strategy hard

Strategic Business Plan

Write a complete strategic business plan for the following venture: Venture: [one sentence description] Stage: [pre-revenue / seed / Series A / established] Target market: [describe] Primary revenue model: [how will this make money?] Plan structure: 1. EXECUTIVE SUMMARY — 3 paragraphs: the opportunity, the solution, the ask 2. MARKET ANALYSIS — TAM/SAM/SOM with reasoning, top 3 competitors and their weaknesses 3. PRODUCT/SERVICE — what it is, what makes it defensible, the roadmap for the first 18 months 4. GO-TO-MARKET — the specific channel strategy for the first 500 customers, not a generic funnel 5. FINANCIAL MODEL — a 3-year P&L projection with explicit assumptions listed (not hidden in formulas) 6. TEAM — what roles the founding team must cover in year 1 and what the first 3 hires should be 7. RISK REGISTER — top 5 risks ranked by probability × impact, each with a mitigation strategy 8. THE ASK — what you need (capital, partnerships, talent) and what milestones it unlocks Write for a sophisticated investor who has seen 500 pitch decks.

C
Coding frontier

Complex Bug — Root Cause + Fix

Use your maximum reasoning depth to diagnose this production bug. Walk through every hypothesis systematically — do not skip steps. Symptom: [describe what breaks, when it breaks, and under what conditions] Error logs: ``` [Paste logs] ``` Relevant code: ``` [Paste code] ``` Environment: [OS, runtime, framework versions] What we have already ruled out: [list attempts] When it started: [date / deploy] Frequency: [always / intermittent / under load / specific input] Deliver: 1. HYPOTHESIS RANKING — all plausible causes, ordered by probability, each with the evidence for and against 2. THE FIX — exact code changes for the most likely cause 3. VERIFICATION PLAN — how to confirm the fix worked before calling it done 4. REGRESSION GUARD — a test that will catch this class of bug in future 5. POST-MORTEM NOTE — one paragraph suitable for a team incident retrospective

L
Writing hard

Long-Form Investigative Article

Write a 3,000-word investigative-style article on the following topic. This is not a summary — it requires synthesis, analysis, and an editorial point of view. Topic: [your topic] Publisher/audience: [who will read this and what do they already know?] Central argument (your thesis): [what single claim should the reader believe after reading this?] The most uncomfortable implication: [what does the evidence suggest that most people don't want to accept?] Structure: - Opening scene or specific example that makes the abstract concrete (300 words) - Context and background — why this matters now (400 words) - The evidence — 4 sections of 400 words each, each advancing the argument with a specific example or data point - The counterargument — the strongest challenge to your thesis, taken seriously (300 words) - Conclusion — what this means for the reader and what they should do (200 words) Every claim must be supported by a specific piece of evidence. No vague assertions.

P
Writing hard

Policy Memo — Senior Government

Write a policy memo on the following issue for a senior government official (Secretary-level or equivalent). The official has 10 minutes to read it before a briefing. Issue: [describe the policy challenge] Relevant jurisdiction: [country/region] Decision required: [what decision does this official need to make?] Deadline: [when is the decision needed?] Key stakeholders affected: [list the main affected parties] Memo structure (follow exactly): 1. PURPOSE — one sentence 2. SITUATION — 2 paragraphs: current state, what has changed recently 3. OPTIONS — 3 options (including a 'do nothing' option), each with pros, cons, and one risk the reader may not have considered 4. RECOMMENDATION — one clear recommendation with 3 supporting reasons 5. IMPLEMENTATION NOTES — the 2 most important execution risks 6. NEXT STEPS — 3 specific actions with owners and dates Tone: neutral, precise, no jargon, no passive voice.

C
Strategy medium

Competitive Intelligence Brief

Write a comprehensive competitive intelligence brief on [competitor company name] for our leadership team. Our company: [one sentence on what you do] Competitor: [name and what they do] Context: [why are we analysing them now — new product, funding round, market entry, pricing change?] Brief sections: 1. OVERVIEW — who they are, their stage, their stated mission (2 paragraphs) 2. PRODUCT COMPARISON — feature-by-feature table: their strengths, their weaknesses, where they beat us, where we beat them 3. CUSTOMER PROFILE — who buys from them and why (use any publicly available signals: reviews, job postings, customer logos, case studies) 4. BUSINESS MODEL — how they make money, their pricing structure, and estimated revenue if public or estimable 5. STRATEGIC INTENT — where are they going in the next 12–18 months? What signals indicate this? 6. VULNERABILITIES — the 3 things they are doing wrong that we can exploit 7. THREAT ASSESSMENT — rate the threat level (Low / Medium / High / Critical) with a one-paragraph rationale Base only on publicly available information.

M
Research hard

Medical Research Summary

Summarise the following clinical research for a well-informed patient (or their family member) who has a science background but is not a clinician. Context: [describe who is asking and why — e.g. 'evaluating a treatment option for a family member with X condition'] Research to summarise: [paste abstract, study, or relevant sections] Deliver: 1. PLAIN ENGLISH SUMMARY — what this study found, in 3 sentences, without medical jargon 2. STUDY QUALITY — was this a randomised trial, observational study, meta-analysis, or case series? What are the key limitations? 3. EFFECT SIZE — how large was the benefit (or harm)? Put it in absolute terms (e.g. '5 people out of 100' not '30% relative reduction') 4. WHO DOES IT APPLY TO — are there patient characteristics that make this finding more or less relevant? 5. WHAT IT DOESN'T ANSWER — the most important question this study cannot resolve 6. QUESTIONS TO ASK YOUR DOCTOR — 3 specific questions based on this research Note: this is for information, not medical advice.

D
Strategy hard

Due Diligence Checklist

Create a comprehensive due diligence checklist and findings template for the following transaction: Transaction type: [acquisition / investment / partnership / vendor selection / hiring a key executive] Target: [describe the entity being evaluated] Deal size / scope: [approximate] Key risks we already know about: [list any known concerns] Timeline: [how long do we have?] Team doing the diligence: [who is involved — legal, finance, technical, operations?] Deliver: 1. A prioritised checklist organised by workstream (legal, financial, technical, operational, market, people) 2. For each item: what document or data point to request, what red flag to watch for, and who on the team owns it 3. A 'must-have before proceeding' list — the 5 items that are dealbreakers if unsatisfactory 4. A findings template (blank table the team fills in: item, finding, risk rating, recommendation) 5. A final recommendation framework — what score / threshold triggers a 'proceed', 'proceed with conditions', or 'walk away'

P
Analysis hard

Philosophy — Argument Construction

Construct the strongest possible argument for and against the following philosophical position. Do not take a side — your goal is to maximally strengthen both positions. Position: [state the claim, e.g. 'Consciousness cannot be explained by physical processes alone'] Context: [academic essay / debate preparation / personal exploration / teaching material] Length: [250 words per side / 500 words per side / as long as needed] For each side: 1. THE CORE CLAIM — restated with full precision, no straw-manning 2. THE STRONGEST ARGUMENT — the best philosophical or empirical case for this position 3. THE KEY PREMISES — the 3 claims this argument requires to be true 4. THE MOST POWERFUL OBJECTION — the single hardest challenge this view faces 5. A REPLY TO THAT OBJECTION — how a sophisticated proponent would respond End with: the crux — the single factual or logical question that, if resolved, would settle the debate.

M
Strategy frontier

M&A Integration Plan

Draft an M&A integration plan for the following acquisition. Focus on the 100 days immediately post-close. Acquirer: [describe — industry, size, culture] Target: [describe — industry, size, culture, what was acquired: talent, product, market, IP?] Strategic rationale: [why was this acquisition made — synergies, market entry, acqui-hire, consolidation?] Known friction points: [what differences in culture, system, or process are already apparent?] Plan: 1. DAY 1 PRIORITIES — the 10 things that must happen on close day to prevent disruption 2. FIRST 30 DAYS — stabilise: communications plan, retention risk assessment, process freeze (what not to change yet) 3. DAYS 31–60 — integrate: the 3 highest-priority systems/processes to merge, and how 4. DAYS 61–100 — optimise: the first synergy to realise and how to measure it 5. RISK REGISTER — top 5 integration risks (talent flight, culture clash, customer disruption, technical debt, regulatory) with mitigation 6. SUCCESS METRICS — the 5 KPIs that will tell us if integration is on track at day 100

R
Legal frontier

Regulatory Compliance Audit

Audit the following product/process for compliance with [GDPR / HIPAA / SOC 2 / CCPA / PCI-DSS / applicable regulation]. Product/process description: [describe what your system does, the data it handles, and who has access] Regulation(s) to audit against: [name the specific regulation(s)] Current controls in place: [describe any existing compliance measures] Audit audience: [internal team / external auditor / legal counsel / board] Audit report structure: 1. SCOPE — what is and is not covered by this audit 2. REQUIREMENTS MAP — a table of every relevant regulatory requirement, with a pass/fail/partial status for each 3. GAPS — every non-compliant item, ranked by severity (Critical, High, Medium, Low) 4. REMEDIATION PLAN — for each gap: the specific technical or process change needed, estimated effort (days), and a suggested owner 5. TIMELINE — a 90-day remediation roadmap prioritising Critical and High items 6. RESIDUAL RISK — risks that cannot be eliminated and must be accepted or insured against

N
Writing hard

Novel Chapter — Literary Fiction

Write a 2,500-word chapter of literary fiction with the following parameters: Genre/tone: [literary fiction / psychological thriller / historical / speculative — pick one and describe the tone] Setting: [time period, location, atmosphere] Point of view character: [name, age, key personality traits, what they want and what they fear] Chapter goal: [what must this chapter accomplish in the story — introduce a character, escalate conflict, reveal backstory?] Opening image or line: [give me a specific image or first sentence to build from, or leave blank] Technical requirements: - Show internal monologue and external action in alternating rhythm - At least one piece of dialogue that reveals character without stating it - A setting detail that carries thematic weight (not decoration) - The emotional state must shift at least twice — the chapter cannot end where it begins emotionally - No adverbs modifying dialogue tags (said quietly, whispered softly, etc.) After the chapter: a 2-sentence note on the craft decisions made and why.

E
Research frontier

Econometric Model Review

Critically review the following econometric model or statistical analysis. Identify every methodological weakness that could invalidate the conclusions. Paper/model: [paste the relevant sections — methodology, results, conclusions] Claim being tested: [what causal or correlational claim is the paper making?] Audience for this review: [peer reviewer / policy team / investment committee / media fact-checker] Review structure: 1. MODEL SPECIFICATION — is the dependent variable correctly defined? Are the independent variables the right ones? Are important controls omitted? 2. IDENTIFICATION STRATEGY — how does the model claim to establish causation (or correlation)? Is this credible? 3. DATA QUALITY — selection bias, measurement error, survivorship bias, data vintage issues 4. STATISTICAL ISSUES — heteroskedasticity, multicollinearity, serial correlation, p-hacking, multiple comparisons 5. EXTERNAL VALIDITY — can the findings be generalised? To which populations, contexts, or time periods? 6. CONCLUSION OVERSHOOT — does the paper's conclusion claim more than the data can support? 7. VERDICT — on a scale of 'credible and actionable' to 'methodologically invalid', where does this land and why?

A
Agentic frontier

Agentic Workflow — End-to-End Task

Execute the following multi-step agentic task. At each step: state what you are doing, what information you need, what assumption you are making, and what the output is before moving to the next step. Task: [describe the full goal in detail — e.g. 'Research three SaaS competitors, summarise their pricing and positioning, identify our top 3 differentiators, and draft a competitive one-pager for the sales team'] Available context and data: [Paste any relevant documents, data, or background] Deliverable format: [what does the final output look like — a document, a table, a structured JSON, a slide outline?] After completing all steps: 1. Final output in the requested format 2. A list of every assumption you made (so a human can validate them) 3. The 2 steps where you had the least confidence in your output, and why

E
Analysis hard

Ethical Dilemma Analysis

Analyse the following ethical dilemma using multiple ethical frameworks. Do not collapse to a single answer — the goal is rigorous multi-perspective analysis. Dilemma: [describe the situation and the decision to be made] Stakeholders: [who is affected and how?] Constraints: [any facts that constrain the options — legal, physical, financial] Context: [why does this matter — academic exercise / real decision / policy formation?] Analyse through each lens: 1. CONSEQUENTIALISM — what does maximising aggregate welfare recommend? What are the second-order effects? 2. DEONTOLOGY — what do duty-based ethics require, regardless of outcome? Are there rights being violated? 3. VIRTUE ETHICS — what would a person of good character do? What does this decision say about the decision-maker? 4. CONTRACTUALISM — what principles could be justified to all affected parties? 5. CARE ETHICS — how does this affect relationships and dependencies between people? Synthesis: - Where do the frameworks agree? - Where do they conflict, and why? - The crux — what is the hardest thing to resolve, and what information would resolve it?

Claude Opus 5.5 vs Other Frontier AI Models (2026)

Where Opus 5.5 sits in the current landscape of leading AI models.

Model Best For Context Reasoning Depth Relative Cost
Claude Opus 5.5 ✓ Frontier reasoning, full codebases, long documents, red-teams 1M tokens Very High High
Claude Fable 5 Absolute frontier — hardest agentic + research tasks 1M tokens Maximum Very High
Claude Sonnet 5 Everyday power use — coding, writing, analysis, agentic tasks 1M tokens High (xhigh mode) Low–Medium
GPT-5.5 Broad general use, plugin ecosystem, image understanding 128K tokens High (o-series mode) Medium
Gemini 4 Multimodal, Google Workspace, video understanding 1M tokens High (thinking mode) Medium–High

Claude Opus 5.5 Prompting Tips

Do This:

  • Specify a clear output structure — Opus 5.5 follows complex multi-part deliverable specs precisely
  • Provide the full context — use the 1M window; don't pre-summarise documents for Opus 5.5
  • Assign an expert role ("act as an adversarial red-team analyst") — it shapes depth, not tone
  • Ask for risk ratings and priority ordering — Opus 5.5 produces actionable ranked outputs
  • Include failure modes: "flag the 3 places most likely to cause a regression"
  • Request a steelman of the opposing view on analysis tasks — it strengthens the final output

Avoid This:

  • Using Opus 5.5 for tasks Sonnet 5 handles well — it's slower and more expensive
  • Vague scope on frontier tasks — "review this codebase" with no specific goal wastes the model
  • Asking for fabricated data, reviews, or citations — specify "based only on the provided documents"
  • Treating its output as a final answer on legal or medical matters — it is research support, not advice
  • Over-constraining format before stating the goal — goal and context first, format constraints last
  • Ignoring the model ID in API calls — pin to claude-opus-5-5 explicitly

Claude Opus 5.5 — Frequently Asked Questions

What is Claude Opus 5.5?

Claude Opus 5.5 is Anthropic's most capable AI model, released September 22, 2026. It is designed for the hardest frontier tasks — full codebase audits, 200-page document synthesis, complex legal analysis, multi-step agentic workflows, and tasks requiring sustained deep reasoning across extremely long contexts. Opus 5.5 succeeds Claude Opus 4.8 with significantly improved reasoning depth, better instruction following on complex multi-part prompts, and stronger performance on long-context tasks where Sonnet 5 begins to show limitations.

How is Claude Opus 5.5 different from Claude Sonnet 5?

Claude Sonnet 5 and Opus 5.5 are both highly capable, but they are optimised for different workloads. Sonnet 5 is the best-value choice for everyday power use — coding, writing, analysis, and moderate agentic tasks — at $2/$10 per million tokens. Opus 5.5 is for tasks where you need maximum reasoning depth: full codebase audits across millions of lines, 200-page legal or research documents, complex multi-agent orchestration, and tasks requiring sustained focus over extremely long contexts. If Sonnet 5 at xhigh reasoning still gives you shallow output, Opus 5.5 is the right model.

What tasks is Claude Opus 5.5 best at?

Claude Opus 5.5 excels at: full codebase architectural audits, legal contract deep review (including 100+ page agreements), comprehensive research synthesis from long documents, complex security red-team analysis, multi-file refactors with zero breaking changes, econometric and statistical model review, long-form literary and investigative writing, M&A due diligence, regulatory compliance audits, and long-horizon agentic workflows requiring many sequential decisions. For simpler tasks (emails, standard code review, short articles), Sonnet 5 is faster and significantly cheaper.

Can I use these prompts for free?

All 20 prompts on this page are free to copy and use. Claude Opus 5.5 is available on the Claude.ai Pro and Max subscriptions, and via the Anthropic API. Due to its significantly higher computation requirements, Opus 5.5 is not available on the free tier of Claude.ai. API pricing is higher than Sonnet 5 — check the Anthropic pricing page for current rates. For budget-conscious use, Sonnet 5 at xhigh reasoning handles many frontier tasks at a fraction of the cost.

What is the context window for Claude Opus 5.5?

Claude Opus 5.5 has a 1M token context window — the same as Sonnet 5 and Fable 5. This fits approximately 750,000 words, a large codebase with hundreds of files, or a 200-page document comfortably. Opus 5.5's advantage over Sonnet 5 on long contexts is not the window size but the quality of reasoning across it: Opus 5.5 is less likely to lose track of earlier sections, miss cross-document contradictions, or produce conclusions that ignore content from the middle of a long input.

Should I use Claude Fable 5 or Claude Opus 5.5?

Claude Fable 5 is Anthropic's absolute frontier model — Opus 5.5 is the step below it, positioned between Fable 5 and Sonnet 5. If your task truly requires the maximum possible reasoning depth and you are willing to pay Fable 5 pricing, use Fable 5. For most frontier tasks — complex coding audits, long document synthesis, deep research — Opus 5.5 delivers near-Fable-5 quality at meaningfully lower cost. A practical heuristic: try Opus 5.5 first; step up to Fable 5 only if the output is clearly insufficient.

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