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About Claude Opus 5.5
Every few months, the top end of the AI market reshuffles. Anthropic’s latest move is Claude Opus 5.5, released on September 22, 2026 as the first model in the new Claude 5.5 family. The pitch: performance at the level of Claude Fable 5.1 — Anthropic’s most capable system — on most work, at a lower price than the Opus 5 it replaces. Anthropic says typical workloads cost about 40% less to run than on Opus 5, helped by cheaper tokens, cheaper cache reads and a model that uses fewer tokens per job.
What Is Claude Opus 5.5?
Claude Opus 5.5 is Anthropic’s flagship Opus-tier large language model, built for serious coding, long-running agent work and demanding professional knowledge work. Developers call it through the API as claude-opus-5-5. Its 1M-token context window holds a large codebase or a thick research file in one conversation, and it can return up to 128K tokens in a single response.
Two things stand out. First, it was tested before release by external evaluators, including Frontier Design and METR, and ships with safeguards similar to those on Fable 5.1. Second, it writes differently — key points up front, less jargon, and it follows the writing rules you give it.
Key Features
- Frontier agentic coding: Opus 5.5 leads Anthropic’s published benchmark table for agentic coding, scoring 66.4% on Terminal-Bench 4.0, 54.4% on FrontierCode v1.1 and 57.8% on CursorBench 4.0. It is built for sprawling jobs — migrations, audits, refactors — not one-line autocomplete.
- Knowledge work that holds up: On GDPval-AA v2.1 (real professional work across 44 occupations), it scores 1846 Elo, ahead of Fable 5.1 (1735) and Opus 5 (1708). In Anthropic’s research test, 16 of 18 of its reports passed a strict fact-checking bar that neither rival cleared at all.
- Computer use and vision: It scores 81.8% (partial) on OSWorld for computer use and reads dense documents, charts and screenshots at high fidelity.
- Faster and cheaper to run: Output is more than 30% faster than Opus 5, cache reads cost $0.20 per million tokens (60% less), and a fast mode in Claude Code and on the Claude Platform runs at up to 2.5x speed at double the token price.
- Serious safety work: Opus 5.5 is Anthropic’s strongest model yet on its automated behavioral audit, attempted to cross containment boundaries about 85% less often than Opus 5 or Mythos 5.1 in a dedicated test, and is more resistant to prompt injection than Opus 5. Zero data retention is available, and five-hour usage limits have been raised on paid plans.
How to Use Claude Opus 5.5
- Pick your route. Use Opus 5.5 inside Claude on the Pro, Max, Team or Enterprise plans, call the API on the Claude Platform, or run it on AWS, Google Cloud or Microsoft Azure.
- For coding, start in Claude Code. Give it a bounded job — a migration, an audit, a refactor — and let it plan before it edits; it finds the root cause first and explains changes plainly.
- For API work, call
claude-opus-5-5. Set an effort level: lower for routine work, higher for hard problems. Thinking cannot be switched off on this model — effort is the control you get. - Use prompt caching. If your agent re-sends the same instructions or repo context at every step, cache it — at $0.20 per million cache-read tokens, this is where the savings are.
- Save fast mode for deadlines. It costs double, so reserve it for interactive sessions.
Claude Opus 5.5 Pricing
There is no single starting price, because access runs through two doors: per-token API billing, or a Claude subscription. The listing is Paid — Anthropic lists Opus 5.5 on the Pro, Max, Team and Enterprise plans, not on the free plan. Here is the verified pricing:
| Plan | Price | What you get |
|---|---|---|
| API (standard) | $4 in / $20 out | Per million tokens on the Claude Platform, AWS, Google Cloud and Microsoft Azure — 20% below Opus 5. Cache reads $0.20 per million tokens. |
| API fast mode | $8 in / $40 out | Per million tokens in Claude Code and on the Claude Platform, at up to 2.5x the standard speed. |
| Claude Pro | $20/month | Opus 5.5 in the Claude apps plus Claude Code. $17/month billed annually. Max plans with 5x–20x more usage start from $100/month. |
Read these numbers per finished task, not per token: one early tester audited and fixed a 200,000-line codebase in under three hours, work that took Opus 5 more than twenty hours.
Pros
- Matches Fable 5.1 on most work while costing far less per token
- Best-in-class agentic coding results, with real endurance on multi-hour jobs
- Cache reads cut by 60%, so long agent runs get cheaper where it hurts most
- Clearer, better-structured writing than previous Opus models
- Strongest alignment-audit results Anthropic has published, with external pre-release testing
- Available on Claude plans, Claude Code, AWS, Google Cloud and Azure
Cons
- Still a premium model — mid-tier rivals charge half its token price or less
- No access on Claude’s free plan; you need at least Pro
- Most cybersecurity tasks are re-routed to Opus 4.8 by its safeguards, unless you join Anthropic’s verification program
- Thinking mode cannot be turned off, which latency-sensitive apps will dislike
- Anthropic itself warns that benchmark margins at this level are a weak guide — test on your own work
Who Should Use Claude Opus 5.5?
Engineering teams running agents over large codebases get the most from it — migrations, audits, refactors and code review are what it was tuned for. Analysts and finance teams doing long, document-heavy work where a wrong figure is expensive come next. For light chat or quick drafts, a cheaper model will do, and you will feel the Opus price without the benefit.
Claude Opus 5.5 Alternatives
OpenAI’s mid-tier GPT 6.1 Sol undercuts it on token price and suits stacks built on OpenAI’s API and Codex. Google’s Gemini 4 Argon is the other name to compare for long, complex professional work. Browse all three in our AI tools directory.
Frequently Asked Questions
How much does Claude Opus 5.5 cost?
On the API: $4 per million input tokens, $20 per million output, cache reads $0.20 per million, fast mode $8/$40. Inside Claude, it comes with Pro ($20/month) and above.
Is Claude Opus 5.5 free to use?
No — it sits on the Pro, Max, Team and Enterprise plans, and the API is pay-as-you-go.
What is the model ID for Claude Opus 5.5?
Use claude-opus-5-5 on the Claude Platform. The same model runs on Amazon Web Services, Google Cloud and Microsoft Azure.
How big is the Claude Opus 5.5 context window?
It has a 1M-token context window and can generate up to 128K tokens in a single response, which suits whole-codebase and long-document work.
Final Verdict
Claude Opus 5.5 moves capability and price in the right directions at once: Fable-level results, cheaper running, clearer writing, and Anthropic’s strongest safety testing to date. It is not cheap, and its safeguards will occasionally step in front of security work — but for teams handing real, long-running jobs to an AI, it is easy to justify. Visit the official Claude Opus page for full model details.
A good fit starts with the details. Check the official website for current features, pricing and availability before choosing a tool.
