Claude Opus 5.5 vs. Claude Opus 5: API Cost Comparison
On this API, Claude Opus 5.5 costs $2 / $10 per 1M tokens (in/out) and Claude Opus 5 costs $2.5 / $12.5. Claude Opus 5.5 is the cheaper option, and both run on the same key — switching is a one-line model parameter change.
Per-token pricing
| Claude Opus 5.5 | Claude Opus 5 | |
|---|---|---|
| Vendor | Anthropic | Anthropic |
| Input · per 1M tokens · Official list | $4 | $5 |
| Input · per 1M tokens · Your price | $2 | $2.5 |
| Output · per 1M tokens · Official list | $20 | $25 |
| Output · per 1M tokens · Your price | $10 | $12.5 |
| Discount vs. list | -50% | -50% |
| Context window | 200K tokens | 200K tokens |
| Max output tokens | 128K tokens | 128K tokens |
All prices in USD per 1M tokens.
What a real workload costs
Same request stream priced on both models — 10M input + 2M output tokens per month, a typical coding-agent load:
Claude Opus 5.5
- At official list
- $80 per month
- On this API
- $40 per month
Claude Opus 5
- At official list
- $100 per month
- On this API
- $50 per month
Switching between them
Both models answer on the same endpoint. Keep your base URL and key; change only the model parameter to reroute a request:
curl https://kktt.net/v1/chat/completions \
-H "Authorization: Bearer $API_KEY" \
-d '{"model": "claude-opus-5-5", "messages": [...]}'curl https://kktt.net/v1/chat/completions \
-H "Authorization: Bearer $API_KEY" \
-d '{"model": "claude-opus-5", "messages": [...]}'FAQ
Which is cheaper, Claude Opus 5.5 or Claude Opus 5?
On this API, Claude Opus 5.5 is cheaper: $2 in / $10 out per 1M tokens, versus $2.5 in / $12.5 out for Claude Opus 5.
Can I use Claude Opus 5.5 and Claude Opus 5 with the same API key?
Yes. Both are callable with one key on the same base URL — switching between them is a one-line change of the model parameter, which makes A/B testing or fallback routing trivial.
Do Claude Opus 5.5 and Claude Opus 5 differ in context window?
Claude Opus 5.5 supports 200K of context with 128K max output; Claude Opus 5 supports 200K with 128K max output.