# Claude Sonnet 5.5 vs Claude Opus 5.5

> Markdown mirror of https://router.one/models/compare/claude-sonnet-5-5-vs-claude-opus-5-5 for AI assistants and crawlers. Router One is a unified, OpenAI-compatible LLM API gateway.

Claude Sonnet 5.5 is the lower-priced of the two on Router One — about 40% less on a 1M-input + 1M-output mix. Both carry a 1.05M context window. Both answer on /v1/chat/completions and /v1/messages (Claude Code).

Claude Sonnet 5.5 and Claude Opus 5.5 compared on current per-token rates, context window, and capabilities — both callable through one OpenAI-compatible endpoint with per-request cost traces.

## Claude Sonnet 5.5 vs Claude Opus 5.5: rates, context window, and capabilities

| Spec | Claude Sonnet 5.5 | Claude Opus 5.5 |
| --- | --- | --- |
| Input / 1M tokens | $1.20 | $2.00 |
| Output / 1M tokens | $6.00 | $10.00 |
| Cached input / 1M tokens | $0.12 | $0.20 |
| Context window | 1.05M | 1.05M |
| Capabilities | Chat, Streaming, Tool calling, Vision | Chat, Streaming, Tool calling, Vision |
| Subscription plans | Not in any plan — wallet | Not in any plan — wallet |
| Detail page | [Claude Sonnet 5.5](https://router.one/models/claude-sonnet-5-5) | [Claude Opus 5.5](https://router.one/models/claude-opus-5-5) |

## What does 1M tokens cost on Claude Sonnet 5.5 vs Claude Opus 5.5?

For a workload of 1M input plus 1M output tokens at current rates: Claude Sonnet 5.5 comes to $7.20, Claude Opus 5.5 comes to $12.00 — Claude Sonnet 5.5 is about 40% cheaper on this mix. Real workloads skew heavily toward input tokens, so weigh the input rate by your own ratio; the cached-input row above is the posted catalog rate for that model.

## Switch between Claude Sonnet 5.5 and Claude Opus 5.5

The API key, base URL and endpoints stay the same, and per Anthropic's docs (checked 2026-09-30) both models default to adaptive thinking and reject forced tool use, but three things differ: of the two, only Claude Sonnet 5.5 accepts between_tools to turn up-front thinking off; the API's default effort is high on Sonnet 5.5 and medium on Opus 5.5, so set output_config.effort on /v1/messages instead of relying on the default; and neither model reads the other's thinking blocks, so a conversation that switches loses the earlier reasoning. Router One's compatibility rewrites for Opus 5.5 requests (see /blog/claude-opus-5-5-migration-guide) do not apply to Claude Sonnet 5.5. As of the 2026-09-30 plan response, both models are in no plan tier and bill the wallet per token.

`compare.sh`

```bash
curl https://api.router.one/v1/chat/completions \
  -H "Authorization: Bearer sk-your-router-one-key" \
  -H "Content-Type: application/json" \
  -d '{"model": "anthropic/claude-sonnet-5.5", "messages": [{"role": "user", "content": "Hello"}]}'

# Same request, other model — change one string:
#   "model": "anthropic/claude-opus-5.5"
```

## FAQ

### Is Claude Sonnet 5.5 cheaper than Claude Opus 5.5?

Input: Claude Sonnet 5.5 $1.20 vs Claude Opus 5.5 $2.00 / 1M tokens; Claude Sonnet 5.5 has the lower rate. Output: Claude Sonnet 5.5 $6.00 vs Claude Opus 5.5 $10.00 / 1M tokens; Claude Sonnet 5.5 has the lower rate. Total cost depends on the workload's input, output and cache usage. Rates change; the /models page is the live source of truth.

### Is Claude Sonnet 5.5 or Claude Opus 5.5 included in a Router One subscription?

Neither Claude Sonnet 5.5 nor Claude Opus 5.5 is in a Router One plan, so every call to either bills the wallet per token.

### Can I switch between Claude Sonnet 5.5 and Claude Opus 5.5 without changing code?

The API key, base URL and endpoints stay the same, and per Anthropic's docs (checked 2026-09-30) both models default to adaptive thinking and reject forced tool use, but three things differ: of the two, only Claude Sonnet 5.5 accepts between_tools to turn up-front thinking off; the API's default effort is high on Sonnet 5.5 and medium on Opus 5.5, so set output_config.effort on /v1/messages instead of relying on the default; and neither model reads the other's thinking blocks, so a conversation that switches loses the earlier reasoning. Router One's compatibility rewrites for Opus 5.5 requests (see /blog/claude-opus-5-5-migration-guide) do not apply to Claude Sonnet 5.5. As of the 2026-09-30 plan response, both models are in no plan tier and bill the wallet per token.

### Where do these numbers come from?

Specs and prices on this page render from the live Router One catalog — the same data as the /models page — and refresh with it. Pricing methodology is documented on /pricing-methodology. Rates on this page were read from the live catalog on 2026-09-30 (UTC) and refresh within the hour.

## More comparisons

- [Claude Sonnet 5.5 vs Claude Sonnet 5](https://router.one/models/compare/claude-sonnet-5-5-vs-claude-sonnet-5)
- [Claude Opus 5.5 vs Claude Opus 5](https://router.one/models/compare/claude-opus-5-5-vs-claude-opus-5)
- [Claude Opus 5.5 vs GPT-6 Sol](https://router.one/models/compare/claude-opus-5-5-vs-gpt-6-sol)
- [Claude Opus 5.5 vs Claude Sonnet 5](https://router.one/models/compare/claude-opus-5-5-vs-claude-sonnet-5)

## See also

- Canonical page: https://router.one/models/compare/claude-sonnet-5-5-vs-claude-opus-5-5
- All model comparisons: https://router.one/models/compare
- All models & prices: https://router.one/models (markdown: https://router.one/models.md)
- Pricing: https://router.one/pricing
- Claude API access: https://router.one/cheap-claude-api
- Claude Sonnet 5.5 API guide: https://router.one/blog/claude-sonnet-5-5-api-guide
- Claude Opus 5.5 API guide: https://router.one/blog/claude-opus-5-5-api-guide
- Claude Code on Opus 5.5: https://router.one/blog/claude-code-opus-5-5-setup
- Migrating to Claude Opus 5.5: https://router.one/blog/claude-opus-5-5-migration-guide
- Cost calculator: https://router.one/llm-cost-calculator
- Pricing methodology: https://router.one/pricing-methodology