Claude Opus 4.5

Anthropic's Claude 4.5 flagship for complex software engineering, agentic workflows and long-horizon computer use, with a 200K token context window.

POST/v1/ai/chat

$0.01/call

Overview

Anthropic's Claude 4.5 flagship for complex software engineering, agentic workflows and long-horizon computer use, with a 200K token context window.

Property	Value
Model ID	`anthropic/claude-opus-4.5`
Context Window	200,000 tokens
Max Output	64,000 tokens
Input Price	$7.38 / 1M tokens
Output Price	$36.92 / 1M tokens

Usage

const res = await fetch('https://api.yepapi.com/v1/ai/chat', {
  method: 'POST',
  headers: {
    'x-api-key': 'YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    model: 'anthropic/claude-opus-4.5',
    messages: [{ role: 'user', content: 'Review this pull request for correctness and security issues.' }],
  }),
});
const { data } = await res.json();
console.log(data.message.content);

curl -X POST https://api.yepapi.com/v1/ai/chat \
  -H "x-api-key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "anthropic/claude-opus-4.5", "messages": [{"role": "user", "content": "Review this pull request for correctness and security issues."}]}'

Request Body

Parameter	Type	Required	Description	Default
`model`	`string`	Yes	Model ID (e.g. `anthropic/claude-opus-4.5`)	—
`messages`	`Message[]`	Yes	Array of `{ role, content }` objects	—
`maxTokens`	`number`	No	Maximum tokens in the response	Model default
`temperature`	`number`	No	Sampling temperature (0.0–2.0)	`1.0`
`topP`	`number`	No	Nucleus sampling threshold	`1.0`
`frequencyPenalty`	`number`	No	Penalize repeated tokens	`0`
`presencePenalty`	`number`	No	Penalize tokens already present	`0`
`stream`	`boolean`	No	Enable SSE streaming	`false`

Info

All AI models use the /v1/ai/chat endpoint. Specify the model with the model field.

Response

{
  "ok": true,
  "data": {
    "model": "anthropic/claude-opus-4.5",
    "message": {
      "role": "assistant",
      "content": "The handler trusts the user id from the request body instead of the session, the SQL is built by string concatenation, and the retry loop has no backoff. Fix all three before merging; the rest is fine."
    },
    "usage": {
      "promptTokens": 16,
      "completionTokens": 245,
      "totalTokens": 261
    }
  }
}

Streaming

Set "stream": true to receive Server-Sent Events. Each chunk contains a delta object:

data: {"delta":{"content":"Use"},"model":"anthropic/claude-opus-4.5","index":0}
data: [DONE]

Under the Hood

We handle auth, billing, and response normalization — you just send messages.