Claude Sonnet 4.5 20250929 API
Anthropic's chat model. Call it on 666 AI with the same API key as every other model. Pay as you go; prices follow the upstream in real time and this page updates hourly.
| Vendor | Anthropic |
| Type | chat |
| Price | $4.05 per 1M input tokens · $20.25 per 1M output tokens |
| Context window | 200K tokens |
| Live test | Passed our live test in the last 7 days · 4 supply routes, automatic failover |
| Latency (short request) | Median ~1s (5+ calls in the last 7 days) |
| Model ID (use this in your request) | anthropic/claude-sonnet-4-5-20250929 |
How to call Claude Sonnet 4.5 20250929
The API is OpenAI-compatible. Replace YOUR-ENDPOINT with the endpoint shown on your API Key page after you sign up, and YOUR-KEY with your key.
curl https://YOUR-ENDPOINT/v1/chat/completions \
-H "Authorization: Bearer YOUR-KEY" \
-H "Content-Type: application/json" \
-d '{"model": "anthropic/claude-sonnet-4-5-20250929", "messages": [{"role": "user", "content": "Hello"}]}'from openai import OpenAI
client = OpenAI(base_url="https://YOUR-ENDPOINT/v1", api_key="YOUR-KEY")
r = client.chat.completions.create(
model="anthropic/claude-sonnet-4-5-20250929",
messages=[{"role": "user", "content": "Hello"}],
)
print(r.choices[0].message.content)Similar models — price comparison
| Model | Price |
|---|---|
| Gemini 3.1 Pro Preview Customtools | $2.7 per 1M input tokens · $16.2 per 1M output tokens |
| GLM 5.2 Fast Preview | $4.72 per 1M input tokens · $14.85 per 1M output tokens |
| GPT 5.4 | $3.04 per 1M input tokens · $18.23 per 1M output tokens |
| Claude Sonnet 4.6 | $4.05 per 1M input tokens · $20.25 per 1M output tokens |
| GPT 5.6 Sol | $4.86 per 1M input tokens · $24.3 per 1M output tokens |
| Claude Opus 5.5 | $5.4 per 1M input tokens · $27 per 1M output tokens |
More models from Anthropic
| Model | Price |
|---|---|
| Claude Fable 5 | $13.5 per 1M input tokens · $67.5 per 1M output tokens |
| Claude Fable 5.1 | $13.5 per 1M input tokens · $67.5 per 1M output tokens |
| Claude Haiku 5.5 | $0.135 per 1M input tokens · $0.675 per 1M output tokens |
| Claude Opus 4.5 20251101 | $6.75 per 1M input tokens · $33.75 per 1M output tokens |
| Claude Opus 4.6 | $6.75 per 1M input tokens · $33.75 per 1M output tokens |
| Claude Opus 4.7 | $6.75 per 1M input tokens · $33.75 per 1M output tokens |
| Claude Opus 4.8 | $6.75 per 1M input tokens · $33.75 per 1M output tokens |
| Claude Opus 5 | $6.75 per 1M input tokens · $33.75 per 1M output tokens |
FAQ
How much does the Claude Sonnet 4.5 20250929 API cost?
On 666 AI, Claude Sonnet 4.5 20250929 costs $4.05 per 1M input tokens · $20.25 per 1M output tokens. You pay only for what you use — no monthly fee. Prices follow the upstream in real time; this page updates every hour.
Can I use the official OpenAI SDK?
Yes. The API is OpenAI-compatible: in the OpenAI Python or Node.js SDK just change base_url and api_key, and set model to anthropic/claude-sonnet-4-5-20250929.
How do I pay?
Bank card (including Google Pay / Apple Pay), USDT / ETH, or bank wire. Top up once and usage is deducted as you go.