Claude 4.5 Sonnet Thinking API

anthropic/claude-sonnet-4.5
Claude 4.
Context
200K tokens
Input
$4.1262 / 1M tokens
Output
$20.631 / 1M tokens
Released
Oct 1, 2025

How to use Claude 4.5 Sonnet Thinking API

Install any OpenAI-compatible SDK, point it at api.aimlapi.com/v1, and set the model to anthropic/claude-sonnet-4.5.
import requests

r = requests.post(
    "https://api.aimlapi.com/v1/chat/completions",
    headers={"Authorization": "Bearer " + AIMLAPI_KEY},
    json={
      "model": "anthropic/claude-sonnet-4.5",
      "messages": [
        {
          "role": "user",
          "content": "Hello!"
        }
      ]
    },
)
print(r.json())
const r = await fetch("https://api.aimlapi.com/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.AIMLAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "anthropic/claude-sonnet-4.5",
    "messages": [
      {
        "role": "user",
        "content": "Hello!"
      }
    ]
  }),
});
console.log(await r.json());
curl -X POST https://api.aimlapi.com/v1/chat/completions \
  -H "Authorization: Bearer $AIMLAPI_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"anthropic/claude-sonnet-4.5","messages":[{"role":"user","content":"Hello!"}]}'

OpenAI-compatible — swap the base URL and it works with your existing SDK.

Claude 4.5 Sonnet Thinking API Pricing

TypePrice
Input
$4.1262 / 1M tokens
Output
$20.631 / 1M tokens
Cached input
$0.41262 / 1M tokens

Claude 4.5 Sonnet Thinking Benchmarks

BenchmarkScoreWhat it measuresSourceRetrieved
Intelligence
21.2
Composite score across standardised reasoning, knowledge and problem-solving evaluations, measured independently by Artificial AnalysisSourceSeptember 12, 2026
Coding
52.1
Composite score across standardised coding evaluations, measured independently by Artificial AnalysisSourceSeptember 12, 2026
Math
88
Composite score across standardised mathematics evaluations, measured independently by Artificial AnalysisSourceSeptember 12, 2026
SWE-bench Verified
77.2%
Resolving verified real GitHub issuesSourceSeptember 22, 2026
OSWorld
61.4%
Computer-use across real desktop applicationsSourceSeptember 22, 2026

Claude 4.5 Sonnet Thinking vs other models

ModelInputOutputContextBest for
$4.1262 / 1M tokens
$20.631 / 1M tokens
200K tokens
Chat + assistants
$6.5 / 1M tokens
$39 / 1M tokens
1M tokens
Reasoning + agents
$2.6 / 1M tokens
$13 / 1M tokens
1M tokens
Balanced coding + agents
$3.9 / 1M tokens
$19.5 / 1M tokens
1M tokens
Long-context, multimodal & agentic workflows
$1.95 / 1M tokens
$11.7 / 1M tokens
1M tokens
Reasoning + agents

Frequently asked questions

Claude 4.5 Sonnet Thinking has a 200,000 tokens context window and can return up to 64,000 tokens.

Claude 4.5 Sonnet Thinking takes text as input and returns text.

Use anthropic/claude-sonnet-4.5 as the model id. Requests go to https://api.aimlapi.com/v1/chat/completions.

Claude 4.5 Sonnet Thinking is priced at input $4.1262 / 1M tokens, output $19.5 / 1M tokens, cached input $0.41262 / 1M tokens.

Yes, Claude 4.5 Sonnet Thinking can stream responses as they are generated.

Claude 4.5 Sonnet Thinking was built by Anthropic.

Its name includes 'Thinking,' indicating it is built for extended reasoning tasks.

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