Anthropic/v1/ai/anthropic/claude-sonnet-4.5

Claude Sonnet 4.5

Access Claude Sonnet 4.5 through one API key. Previous-gen Anthropic flagship.

Previous-gen Claude Sonnet model. Still a capable all-rounder with strong reasoning and 1M context.

Full Docs Get API Key

Context Window

1M tokens

Max Output

64K tokens

Input Price

$3.00 / 1M tokens

Output Price

$15.00 / 1M tokens

Try it live

Send a message and see Claude Sonnet 4.5 respond in real time.

POST /v1/ai/anthropic/claude-sonnet-4.5Live testing

API Key

Message *

Max Tokens

Maximum tokens in the response.

Stream

Real-time token streaming

Hit "Run" to see the response

Strengths

✓Reasoning

✓Coding

✓Writing

✓Analysis

Quick start

Copy this snippet and start making calls with Claude Sonnet 4.5.

const res = await fetch('https://api.yepapi.com/v1/ai/anthropic/claude-sonnet-4.5', {
  method: 'POST',
  headers: {
    'x-api-key': 'YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "messages": [
      {
        "role": "user",
        "content": "Explain API gateways in 2 sentences."
      }
    ],
    "maxTokens": 256
  }),
});
const data = await res.json();
console.log(data);

Why use Claude Sonnet 4.5 through YepAPI?

✓One API key for all models — no separate accounts

✓OpenAI SDK compatible — just change the base URL

✓No monthly minimums — pay per token

✓Switch models with one line of code

✓Full provider passthrough — citations, search results, and all extras included

✓Streaming and non-streaming support on every model

✓Works with Cursor, Claude, LangChain, and any LLM tool

✓Unified billing across all providers

Frequently asked questions

Previous-gen Claude Sonnet model. Still a capable all-rounder with strong reasoning and 1M context.

Input tokens cost $3.00 per 1M tokens and output tokens cost $15.00 per 1M tokens through YepAPI. No monthly minimums — you only pay for what you use.

Sign up for a free API key, then send requests to the /v1/ai/anthropic/claude-sonnet-4.5 endpoint. YepAPI is OpenAI SDK compatible, so you can use it with any tool that supports OpenAI — just change the base URL.

Claude Sonnet 4.5 supports a 1M token context window with up to 64K output tokens per request.