Claude Opus 5.5 vs Claude Sonnet 5.5
Which one to choose
Pick Claude Opus 5.5 for complex, open-ended work that needs sustained judgement and for agents that run for many hours. Pick Claude Sonnet 5.5 for everyday coding, browsing and computer-use agents where fast replies and fewer tokens per task matter more. Both are current Anthropic models with always-on reasoning ability, so the question is how hard the work is and how much waiting you accept.
Pricing comparison
| Claude Opus 5.5 | Claude Sonnet 5.5 | |
|---|---|---|
| Model maker | Anthropic | Anthropic |
| Delivery availability | Available | Available |
| Context window | 1M | 1M |
| Max output | 128K | 128K |
| Official price | Input$4.00per 1M tokensOutput$20.00per 1M tokens | Input$2.00per 1M tokensOutput$10.00per 1M tokens |
| TokenLab price | Input$1.20per 1M tokensOutput$6.00per 1M tokens | Input$0.60per 1M tokensOutput$3.00per 1M tokens |
| Model performance |
|
|
| Capabilities | JSON modePrompt CacheReasoningTool useVision | JSON modePrompt CacheReasoningTool useVision |
Choose Claude Opus 5.5 when
- You hand over long agent runs, such as an architecture rework, and expect steady decisions throughout.
- The task is open-ended and success depends on judgement rather than on following clear steps.
- You prefer to raise or lower a single effort setting instead of adding a second model.
Choose Claude Sonnet 5.5 when
- Your agent handles many short coding, browsing or computer-use jobs and latency adds up.
- You want tasks finished in fewer tool-calling steps.
- You want to cut up-front thinking for quick turns with the between_tools setting.
How they differ
| Aspect | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|
| Work it is for | Long-running agentic coding and knowledge work, with the heavier judgement of the two. | Everyday coding, agents and computer use, which Anthropic describes as the best mix of speed and intelligence. |
| Thinking | Adaptive thinking is always on and cannot be disabled; medium is the default effort. | Thinking can be reduced with the between_tools setting for faster replies. |
| Speed | Output is faster than Opus 5, but Sonnet 5.5 still answers simpler jobs sooner. | Generates output more than 30% faster than Sonnet 5 and is the quicker of the two. |
| Safeguards | No fallback to a smaller model applies to cybersecurity requests. | New safeguards restrict some cybersecurity tasks, and higher-risk requests fall back to Sonnet 5. |
| Request rules | Forced tool use returns an error, and progress text between tool calls arrives in empty thinking blocks by default. | Forced tool use returns an error, and non-default temperature, top_p or top_k values are rejected. |
Summary
- Claude Opus 5.5: Input $1.20 / Output $6.00 per 1M tokens; Claude Sonnet 5.5: Input $0.60 / Output $3.00 per 1M tokens. Rates depend on the billing unit, specification, and usage. Compare matching conditions in the model's detailed pricing; a single rate does not determine the total cost.
FAQ
Is Claude Opus 5.5 better than Sonnet 5.5?
Opus 5.5 is stronger on complex, open-ended work that needs sustained judgement, per Anthropic. Sonnet 5.5 is faster and enough for most everyday coding and agent jobs. They are different tiers, not a successor pair.
When should I start with Sonnet 5.5?
Start with Sonnet 5.5 when speed and tokens per task drive your costs, then move individual stages to Opus 5.5 if evaluations show gaps in judgement.
Can I swap one for the other without prompt changes?
Mostly yes, since both are current Claude models with the same message format. Check sampling settings and tool-choice settings, because both reject forced tool use.
Can I use both together?
Yes. Let Sonnet 5.5 handle routine steps such as edits, lookups and browsing, and route the hard planning or review stages to Opus 5.5 where judgement matters most.
Which is cheaper, Claude Opus 5.5 or Claude Sonnet 5.5?
Claude Opus 5.5: Input $1.20 / Output $6.00 per 1M tokens; Claude Sonnet 5.5: Input $0.60 / Output $3.00 per 1M tokens. Rates depend on the billing unit, specification, and usage. Compare matching conditions in the model's detailed pricing; a single rate does not determine the total cost.
What are the key differences between Claude Opus 5.5 and Claude Sonnet 5.5?
Both models share similar capabilities.
Sources
- Introducing Claude Opus 5.5
- Claude Opus 5.5 model overview
- Introducing Claude Sonnet 5.5
- Claude Sonnet 5.5 model overview
Reviewed Oct 2, 2026