Claude Sonnet 4.5 20250929

Claude Sonnet 4.5 API provides frontier intelligence at scale. This claude model offers a 200k context window, 92.4% HumanEval score, and reliable tool calling, making it the premier choice for developers using the sonnet 4.5 api via GPTProto.

Modalities

Context

API Usage Examples

curl --request POST "https://gptproto.com/v1/chat/completions" \
  --header "Authorization: Bearer $GPTPROTO_API_KEY" \
  --header "Content-Type: application/json" \
  --data '{
    "model": "claude-sonnet-4-5-20250929",
    "messages": [
      {
        "role": "user",
        "content": "Hello"
      }
    ]
  }'

Claude Sonnet 4.5 20250929 pricing

Estimate a request with real work scenarios. GPTProto token pricing is 20% below official rates.

Cost calculator

Multi-turn agent with cached context.

Input tokens$2.4 / 1M$0.0036

Output tokens$12 / 1M$0.0096

Cache write tokens$3 / 1M$0.009

Cache read tokens$0.24 / 1M$0.006

Cost per request$0.0282

Top up

GPTProto vs official pricing.

Requests

You pay

20% off

$100

You receive$100.00

Save$25.00 (20%)vs Claude official

Related Models

All Models

Model					Input → Output
Claude Sonnet 4.5 20250929Current		1M	$2.40 / $12.00 per 1M	$3.00 / $0.24 per 1M	Input: TextInput: Document Output: Text
GLM 5.3		1.05M	$1.26 / $3.96 per 1M	— / $0.23 per 1M	Input: TextInput: ImageInput: Document Output: Text
Gemini 3.7 Flash		1.05M	$0.45 / $2.25 per 1M	— / $0.04 per 1M	Input: TextInput: ImageInput: Document Output: Text
Grok 4.6		500K	$1.20 / $3.60 per 1M	— / $0.30 per 1M	Input: TextInput: Image Output: Text
Qwen3.8 Max		1M	$1.80 / $5.40 per 1M	$2.25 / $0.23 per 1M	Input: TextInput: ImageInput: VideoInput: Document Output: Text
Claude Opus 5		1M	$4.00 / $20.00 per 1M	$5.00 / $0.40 per 1M	Input: TextInput: ImageInput: Document Output: Text
Gemini 3.6 Flash		1.05M	$0.45 / $2.25 per 1M	— / $0.04 per 1M	Input: TextInput: ImageInput: Document Output: Text
Gemini 3.5 Flash Lite		1.05M	$0.18 / $1.50 per 1M	$0.02 / $0.02 per 1M	Input: TextInput: ImageInput: Document Output: Text
Kimi K3		1.05M	$2.70 / $13.50 per 1M	$0.27 / $0.27 per 1M	Input: TextInput: ImageInput: Document Output: Text
GPT 5.6 Luna		1.05M	$0.16 / $0.96 per 1M	$0.20 / $0.02 per 1M	Input: TextInput: ImageInput: Document Output: Text
GPT 5.6 Terra		1.05M	$1.60 / $9.60 per 1M	$2.00 / $0.16 per 1M	Input: TextInput: ImageInput: Document Output: Text
GPT 5.6 Sol		1.05M	$4.00 / $24.00 per 1M	$5.00 / $0.40 per 1M	Input: TextInput: ImageInput: Document Output: Text
Grok 4.5		500K	$1.20 / $3.60 per 1M	$0.30 / $0.30 per 1M	Input: TextInput: Image Output: Text
Claude Sonnet 5		1M	$1.60 / $8.00 per 1M	$2.00 / $0.16 per 1M	Input: TextInput: Document Output: Text
Minimax M3		1.05M	$0.48 / $0.96 per 1M	$0.10 / $0.10 per 1M	Input: TextInput: ImageInput: Document Output: Text
GLM 5.2		1.05M	$1.26 / $3.96 per 1M	$0.23 / $0.23 per 1M	Input: TextInput: ImageInput: Document Output: Text
Claude Fable 5		1M	$8.00 / $40.00 per 1M	$10.00 / $0.80 per 1M	Input: TextInput: Document Output: Text
Qwen3.7 Max		1M	$0.36 / $1.44 per 1M	$0.07 / $0.07 per 1M	Input: TextInput: Document Output: Text
Claude Opus 4.8 Thinking		1M	$4.00 / $20.00 per 1M	$5.00 / $0.40 per 1M	Input: TextInput: Document Output: Text
Claude Opus 4.8		1M	$4.00 / $20.00 per 1M	$5.00 / $0.40 per 1M	Input: TextInput: Document Output: Text
DeepSeek v4 Flash	—	1.05M	$0.44 / $1.32 per 1M	— / $0.01 per 1M	Input: Text Output: Text
DeepSeek v4 Pro	—	1.05M	$1.32 / $3.96 per 1M	— / $0.04 per 1M	Input: Text Output: Text
Grok 4.3		1M	$0.75 / $1.50 per 1M	$0.12 / $0.12 per 1M	Input: TextInput: Image Output: Text
Kimi K2.6		262K	$0.85 / $3.60 per 1M	$0.14 / $0.14 per 1M	Input: TextInput: Document Output: Text
Claude Opus 4.7 Thinking		1M	$4.00 / $20.00 per 1M	$5.00 / $0.40 per 1M	Input: TextInput: Document Output: Text
GLM 5.1		205K	$1.26 / $3.96 per 1M	$0.23 / $0.23 per 1M	Input: TextInput: Document Output: Text
DeepSeek v3.2		164K	$0.17 / $0.25 per 1M	$0.02 / $0.02 per 1M	Input: Text Output: Text
Minimax M2.5		205K	$0.24 / $0.96 per 1M	$0.30 / $0.02 per 1M	Input: TextInput: Document Output: Text
Kimi K2.5		262K	$0.54 / $2.70 per 1M	$0.09 / $0.09 per 1M	Input: TextInput: Document Output: Text
Qwen Turbo		—	$0.04 / $0.18 per 1M	$0.009 / $0.009 per 1M	Input: Text Output: Text
Doubao Seed 1.6 Thinking 250715		262K	$0.10 / $0.97 per 1M	—	Input: TextInput: Image Output: Text
Doubao Seed 1.6 Thinking 250615		262K	$0.10 / $0.97 per 1M	—	Input: TextInput: Image Output: Text
Doubao Seed 1.6 Flash 250615		262K	$0.02 / $0.18 per 1M	—	Input: TextInput: Image Output: Text

Core Claude Sonnet 4.5 API Features

Standout capabilities that define the claude 4.5 experience for enterprise-grade applications.

Frontier-Grade Coding

Claude hits 92.4% on HumanEval, excelling at multi-file refactors and logic error detection in complex codebases.

Reliable Tool Invocation

Optimized for agentic workflows with a sub-1% syntax failure rate for autonomous claude execution and tool use.

High-Fidelity RAG

Maintain 99.8% recall accuracy across a massive 200k context window with this claude 4.5 model and api.

Advanced Visual Reasoning

Extract structured data from charts and blueprints with industry-leading OCR via the claude sonnet 4.5 api.

Claude Sonnet 4.5 API Common Questions

Expert answers regarding the claude sonnet 4.5 api integration, pricing, and performance metrics for professional developers.

How do I migrate to the Claude Sonnet 4.5 API?

Transitioning is straightforward. Simply update your model parameter to claude-sonnet-4-5-20250929 in your requests. This claude version is backwards compatible with existing sonnet 3.5 prompt formats and system message behaviors, requiring minimal code changes. Using the api via GPTProto allows you to test this latest iteration instantly through our unified endpoint.

Is data sent to the Claude API used for training?

No. Data privacy is a core pillar of the GPTProto and Anthropic partnership. Any data passed through the claude sonnet 4.5 api is not used to train foundation models. Many features are also ZDR-eligible, ensuring your proprietary code and sensitive documents remain private and secure according to strict enterprise standards.

What is the Claude 4.5 Sonnet context window?

This claude model features a standard 200k token context window. In 'Needle In A Haystack' benchmarks, it maintains a 99.8% recall accuracy rate, making it exceptionally reliable for analyzing long-form documents or large codebases. The sonnet 4.5 api also supports prompt caching, which can reduce costs by up to 90% for repetitive long-context blocks.

How does Claude Sonnet 4.5 handle coding tasks?

Claude is a leader in coding proficiency, achieving 92.4% on HumanEval. It is specifically optimized for complex software engineering, such as refactoring across multiple files and fixing race conditions in async code. Developers using the sonnet 4.5 api find it significantly more capable than previous iterations at following multi-part negative constraints.

What are the Claude Sonnet 4.5 API pricing tiers?

Pricing for this claude model is set at $3.00 per 1M input tokens and $15.00 per 1M output tokens. Prompt caching is also available at $3.75 per 1M tokens for writes and $0.30 for reads. This makes the sonnet 4.5 api roughly five times more affordable than the Opus tier while maintaining near-flagship performance levels for most business use cases.

Does the Claude API support visual reasoning?

Yes, claude includes native multimodal support. It can interpret financial charts, architectural blueprints, and complex UI mockups with high OCR accuracy. The sonnet 4.5 api is particularly effective at extracting structured data from these visual assets and converting them into validated JSON schemas for automated data processing pipelines.

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