Language model by Anthropic
Claude Sonnet 4.5 (Thinking) API
model: claude-sonnet-4-5-20250929-thinking
Call Claude Sonnet 4.5 (Thinking) with your KeelRouter API key, the same key you use for every other model. From $2.97 / $14.90 per 1M tokens, paid per call from a prepaid balance. Failed calls are free.
Pricing
| Option | Price |
|---|---|
| Input | $2.97 per 1M tokens |
| Output | $14.90 per 1M tokens |
Call it
OpenAI-compatible endpoint /v1/chat/completions. Anthropic SDKs work on /v1/messages.
curl https://api.keelrouter.com/v1/chat/completions \
-H "Authorization: Bearer $KEELROUTER_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "claude-sonnet-4-5-20250929-thinking",
"messages": [
{
"role": "user",
"content": "Write a haiku about the sea."
}
]
}'Parameters
| Name | Type | Notes |
|---|---|---|
| model | string | Required. claude-sonnet-4-5-20250929-thinking |
| messages | array | Required. OpenAI chat format |
| max_tokens | integer | Output cap; also sets the hold |
| stream | boolean | Server-sent events; usage is billed at the end |
| temperature | number | Passed through |
| tools | array | Passed through when the model supports them |
FAQ
- How much does the Claude Sonnet 4.5 (Thinking) API cost on KeelRouter?
- From $2.97 / $14.90 per 1M tokens. You pay per call from a prepaid USD balance; failed calls are not charged.
- How do I call Claude Sonnet 4.5 (Thinking)?
- Send an OpenAI-compatible request to /v1/chat/completions with model "claude-sonnet-4-5-20250929-thinking" and your KeelRouter API key.
- Is this the official Claude Sonnet 4.5 (Thinking) API?
- No. KeelRouter is an independent API gateway. Requests run on Claude Sonnet 4.5 (Thinking) through our upstream providers, and the language model keeps its own safety filters.
- How long are results kept?
- We keep request records (tokens and cost), not your prompts or answers.
More from Anthropic
KeelRouter is an independent service and is not affiliated with Anthropic. Claude Sonnet 4.5 (Thinking) is a trademark of its owner, used here only to name the model a request runs on.