Choose Claude Opus 5.5 if
- ✓ The task is a multi-step change in a large codebase where a wrong edit is expensive
- ✓ It is long-horizon agent work that has to survive its own mistakes
- ✓ The output is reviewed by a human who costs more than the tokens
Head to head · OpenRouter
Claude Opus 5.5 vs Claude Sonnet 5.5
Exactly double the price for the same 1M-token window: Opus 5.5 lists $4 / $20 per million against Sonnet 5.5's $2 / $10, and both cap output at 128K with the same input modalities. Cached reads move the same 2x ($0.20 against $0.10).
Quick verdict
Inside one family the choice is unusually clean: you are buying the top tier of the same line, and the cliff between them is the point of the lineup. Route the hard 10% of tasks to Opus and the other 90% to Sonnet, and you cut the bill while keeping the ceiling — providing your routing is better than a coin flip.
Side-by-side comparison
| Field | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Context window | 1M tokens | 1M tokens |
| Input / 1M | $4.00 | $2.00 |
| Output / 1M | $20.00 | $10.00 |
| Modalities | Text, Vision, Files | Text, Vision, Files |
| Best for | Overall, Coding, Agents | Overall, Coding, Agents |
Source
openrouter.ai/api/v1/models Verified 2026-10-10 Cost estimates
| Workload | Input | Output | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|---|---|
| Quick test | 20,000 | 5,000 | $0.180 | $0.090 |
| Product chat month | 500,000 | 125,000 | $4.50 | $2.25 |
| Document batch | 5,000,000 | 1,000,000 | $40.00 | $20.00 |
Estimates use list input/output prices and exclude cache discounts, provider surcharges and tool fees.
Choose Claude Sonnet 5.5 if
- ✓ The work is well-scoped: a feature, a bug, a rewrite of one file
- ✓ You are building a product path where most calls are routine
- ✓ You want the same window and modalities for half the money
FAQ
Is Claude Opus 5.5 cheaper than Claude Sonnet 5.5?
Claude Opus 5.5 costs $4.00 input and $20.00 output per 1M tokens. Claude Sonnet 5.5 costs $2.00 input and $10.00 output per 1M tokens.
Which model has the larger context window?
Claude Opus 5.5 offers 1M tokens; Claude Sonnet 5.5 offers 1M tokens. Provider-specific limits can vary by route.
Which one should I choose?
Inside one family the choice is unusually clean: you are buying the top tier of the same line, and the cliff between them is the point of the lineup. Route the hard 10% of tasks to Opus and the other 90% to Sonnet, and you cut the bill while keeping the ceiling — providing your routing is better than a coin flip.
Claude Opus 5.5 details Claude Sonnet 5.5 details Estimate monthly cost
Pricing and context data are based on a 2026-10-10 snapshot. Provider limits and pricing can change; verify on OpenRouter before production.