Claude Sonnet 4.5 (2025-09-29) API

Input / 1M tokens$2.64~~$3.00~~

Output / 1M tokens$13.20~~$15.00~~

LLMAnthropic12% below official128K contextPrompt cachingAnthropic API

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About Claude Sonnet 4.5 (2025-09-29)

Claude Sonnet 4.5 (2025-09-29) by Anthropic is available on API Many from $2.64 per million input tokens and $13.20 per million output tokens, and you call it with the same API key you use for every other model.

It accepts OpenAI-style chat requests with streaming and tools, has a 128K context window and can return up to 16,000 tokens per response.

Claude models also speak the Anthropic Messages API at /v1/messages, so the official Anthropic SDK works by changing only the base URL.

Prompt caching is supported: cached input tokens are billed at the lower cached rate shown in the price table.

You pay only for successful results: failed or rejected requests are refunded automatically, and every call is recorded in your console with its exact cost.

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Frequently asked questions

How much does the Claude Sonnet 4.5 (2025-09-29) API cost?

Claude Sonnet 4.5 (2025-09-29) starts at $2.64 per million input tokens and $13.20 per million output tokens on API Many. The price table on this page lists every tier; you are charged only for successful requests.

How do I call Claude Sonnet 4.5 (2025-09-29)?

Create an API key in the console, then send a request to /v1/chat/completions with "model": "claude-sonnet-4-5-20250929". The API tab has copy-ready examples in cURL, Python and Node.js.

Is this the official Claude Sonnet 4.5 (2025-09-29) model?

Yes. Requests are forwarded to the model maker or an authorized channel with the same parameters, so the output matches the official API.

What happens if a request fails?

Failed, rejected or timed-out requests are not charged. Reserved balance is released automatically and the reason is shown in the call record.