GPT-5.6 Terra vs. Claude Sonnet 4.6: API Cost Comparison
On this API, GPT-5.6 Terra costs $0.7 / $4.2 per 1M tokens (in/out) and Claude Sonnet 4.6 costs $1.5 / $7.5. GPT-5.6 Terra is the cheaper option, and both run on the same key — switching is a one-line model parameter change.
Per-token pricing
| GPT-5.6 Terra | Claude Sonnet 4.6 | |
|---|---|---|
| Vendor | OpenAI | Anthropic |
| Input · per 1M tokens · Official list | $2 | $3 |
| Input · per 1M tokens · Your price | $0.7 | $1.5 |
| Output · per 1M tokens · Official list | $12 | $15 |
| Output · per 1M tokens · Your price | $4.2 | $7.5 |
| Discount vs. list | -65% | -50% |
| Context window | 400K tokens | 200K tokens |
| Max output tokens | 128K tokens | 64K 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:
GPT-5.6 Terra
- At official list
- $44 per month
- On this API
- $15.4 per month
Claude Sonnet 4.6
- At official list
- $60 per month
- On this API
- $30 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": "gpt-5.6-terra", "messages": [...]}'curl https://kktt.net/v1/chat/completions \
-H "Authorization: Bearer $API_KEY" \
-d '{"model": "claude-sonnet-4-6", "messages": [...]}'FAQ
Which is cheaper, GPT-5.6 Terra or Claude Sonnet 4.6?
On this API, GPT-5.6 Terra is cheaper: $0.7 in / $4.2 out per 1M tokens, versus $1.5 in / $7.5 out for Claude Sonnet 4.6.
Can I use GPT-5.6 Terra and Claude Sonnet 4.6 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 GPT-5.6 Terra and Claude Sonnet 4.6 differ in context window?
GPT-5.6 Terra supports 400K of context with 128K max output; Claude Sonnet 4.6 supports 200K with 64K max output.