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TL;DR
- Opus 5.5 lists at $4 and $20 per million input and output tokens. Sonnet 5 lists at $2 and $10.
- Both have a 1M token context window and the same integration surface, so routing between them is cheap to build.
- Sonnet 5 is positioned for real-time agents and high-volume work. Opus 5.5 is positioned for the hardest agentic coding and long-running autonomous work.
- A common pattern: default to Sonnet 5, escalate the hard tail of requests to Opus 5.5.
- Opus 5 now costs more than Opus 5.5 at every price line, so there is little reason to start new work on it.
Every Anthropic pricing page hides the same question: pay double for the flagship, or run the daily driver? After the Claude Opus 5.5 release on September 22, 2026, the gap is easy to state and harder to answer. Opus 5.5 lists at $4 and $20 per million input and output tokens. Sonnet 5 lists at $2 and $10. Same 1M token context window, same API, double the bill.
The two models at a glance
| Dimension | Opus 5.5 | Sonnet 5 |
|---|---|---|
| Input price, per 1M tokens | $4 | $2 |
| Output price, per 1M tokens | $20 | $10 |
| Context window | 1M tokens | 1M tokens |
| Positioning | hardest agentic coding, long-running agents, computer use | real-time agents, high-volume work, daily use |
| Where you get it | Claude apps for Pro, Max, Team, Enterprise; Claude Code; API; AWS, Google Cloud, Microsoft Foundry | Claude.ai for anyone; same API and cloud platforms |
The pattern echoes the classic Opus-versus-Sonnet split, but this generation makes the routing decision easier to act on. Both models sit behind the same API with the same message shape, and both support adaptive thinking with effort settings. Switching a call between them is a model-id change, not a rewrite.
What Sonnet 5 is built for
Anthropic’s Sonnet page pitches it as fast, capable intelligence for real-time agents and high-volume work. The use cases it names are the ones a consumer product actually runs all day: customer-facing agents, content generation and editing, document work, and coding across the development lifecycle. It also lists up to 90% cost savings with prompt caching, which matters when the same instructions and context get re-sent on every request.
If your AI feature answers a user question, drafts something, classifies input, or drives a support agent, Sonnet 5 is the tier Anthropic built for that job. It is also the model anyone can try on Claude.ai, which makes it easy to sanity-check quality before committing API spend.
When Opus 5.5 earns its price
The Opus 5.5 launch makes a specific claim: it is the model for long-running, lightly supervised work. Agents that plan across steps, use memory between sessions, coordinate subagents, and keep going for hours. The early-tester examples are all in that shape: a 680,000-line code migration finished in under a day, an overnight multi-repository task that stayed on track for over 18 hours, a load-time optimization pass that succeeded 39 of 40 times without breaking app behavior.
Those are vendor-published results, but the pattern is consistent. The premium pays off when a task is long, multi-step, and expensive to babysit. It also covers computer use and dense document vision, where Anthropic says Opus 5.5 is the Opus tier’s strongest.
A practical test before you commit: take the tasks where your current model fails or stalls, the ones that need retries and human nudges, and run them on both models. If Opus 5.5 finishes them in fewer steps and fewer tokens, the double price pays for itself. If your traffic is all short prompts and quick generations, it probably does not.
A routing pattern that uses both
Because the models share one API, the cheapest architecture is usually both:
- Default every request to Sonnet 5.
- Escalate to Opus 5.5 on the signals that predict hard work: long context, multi-step plans, tool orchestration, or a failure on the first attempt.
- Keep prompt caching on for both, since repeated context is where the biggest savings live.
The escalation rule can be a complexity classifier, a token-count threshold, or a retry hook. Whichever you use, log which tier handled each request. Without that log, you cannot tell whether the flagship is earning its share of the bill, and the drift is always toward more escalation.
What about Opus 5?
The 5.5 release quietly ended the case for starting new work on Opus 5. It lists at $5 and $25 per million input and output tokens, with cache reads at $0.50. Opus 5.5 is $4 and $20 with cache reads at $0.20, generates output more than 30% faster, and, by Anthropic’s estimate, uses fewer tokens per task. The flagship got better and cheaper in the same move.
Keep Opus 5 pinned only where a platform has not added Opus 5.5 yet. And if the cross-vendor question is live for your team, Opus 5.5 vs GPT-6 Sol covers the same-day OpenAI release, with the full Opus 5.5 breakdown in Claude Opus 5.5 explained.
Sources
FAQ
- Is Opus 5.5 worth it over Sonnet 5?
- It depends on the workload. Opus 5.5 costs double Sonnet 5's list price and is positioned for the hardest agentic coding, long-running agents, and computer use. For everyday generation and high-volume work, Anthropic positions Sonnet 5 as the better fit.
- How much cheaper is Sonnet 5 than Opus 5.5?
- Half the list price on every line: $2 versus $4 per million input tokens, $10 versus $20 per million output tokens. Anthropic also lists up to 90% cost savings on Sonnet 5 with prompt caching.
- Can I use both Opus 5.5 and Sonnet 5 in one product?
- Yes. Both models share the same API and integration surface, and a common pattern routes routine requests to Sonnet 5 while escalating hard or long-running tasks to Opus 5.5.
- What is Opus 5.5 best at?
- Anthropic positions it as the strongest Opus model yet for agentic coding, long-running autonomous agents, computer use, and knowledge work, with adaptive thinking effort settings.
