Claude Sonnet 4.5
VerifiedAnthropic's Claude Sonnet 4.5 excels at large-scale multimodal reasoning and analysis.
About Claude Sonnet 4.5
Developed as a closed-source system by Anthropic, Claude Sonnet 4.5 integrates advanced capabilities for handling diverse input types. Its architecture emphasizes safety and alignment alongside performance. The model avoids open-weight distribution to maintain controlled access and updates.
With its extensive context window, the model handles lengthy documents and complex multimodal data effectively. It demonstrates strong performance in reasoning across text and visual elements. File processing adds versatility for real-world applications.
Users typically apply it to research, coding assistance, and content analysis involving images or attachments. The model suits professional environments requiring detailed comprehension over large inputs. Integration into tools benefits from its multimodal features for enhanced productivity.
Capabilities
How Claude Sonnet 4.5 compares
Claude Sonnet 4.5 (striped bar) vs other multimodal on intelligence, speed and price.
Price
USD per 1M output tokens · Lower is better · Claude Sonnet 4.5 ranks #76 of 97
Nova Premier 1.0Sources: Artificial Analysis (intelligence, speed) · OpenRouter (price).
Best for
Large-scale code analysis
Developers use it to review and refactor entire codebases or repositories that span hundreds of files while maintaining coherence across the full context.
Multimodal document workflows
It handles mixed text-and-image documents such as research papers, slide decks, or scanned reports, extracting insights and answering detailed follow-up questions.
Complex multi-step reasoning tasks
The model breaks down intricate problems in science, engineering, or business into sequential steps while tracking dependencies over very long inputs.
Strengths & limitations
Strengths
- +Strong safety alignment
- +Reliable handling of large contexts
- +Careful and detailed reasoning
- +Effective multimodal file support
Limitations
- –Can be overly cautious with refusals
- –Vision performance varies by image complexity
- –May produce verbose responses
Cost calculator
Estimate what Claude Sonnet 4.5 would cost for your usage.
Based on Claude Sonnet 4.5's $3.00/1M input · $15.00/1M output. Estimate only — actual cost varies by provider and caching.
Quick start
OpenRouter's API is OpenAI-compatible — most SDKs work by just swapping the base URL. Only the model slug changes between models.
import OpenAI from "openai";
const client = new OpenAI({
baseURL: "https://openrouter.ai/api/v1",
apiKey: process.env.OPENROUTER_API_KEY,
});
const completion = await client.chat.completions.create({
model: "anthropic/claude-sonnet-4.5",
messages: [{ role: "user", content: "Hello!" }],
});
console.log(completion.choices[0].message.content);Model slug: anthropic/claude-sonnet-4.5
Editor's verdict
Claude Sonnet 4.5 is Anthropic's proprietary multimodal with a 1000K-token context window.
At $15.00 per 1M output tokens, it is premium-priced for its class.
It is available through Anthropic's API and aggregators like OpenRouter.
Best suited to strong safety alignment and reliable handling of large contexts.
Frequently asked questions
The model supports a context length of 1,000,000 tokens.
User reviews
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