Reasoning · language

Use Claude 3.5 Sonnet (Thinking) with cURL

Updated 2026-05-21 · By XALEN

How to use Claude 3.5 Sonnet (Thinking) (Reasoning, ~500B) with cURL. Install, authenticate, and make your first API call in minutes. Working code example included.

Model

Claude 3.5 Sonnet (Thinking)

~500B · 200K context · $0.03 input

Framework

cURL

language · No installation needed

1. Install

No installation needed

2. Code

curl https://api.xalen.io/v1/chat/completions \
  -H "Authorization: Bearer xln_test_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-3-5-sonnet-thinking",
    "messages": [{"role": "user", "content": "Hello!"}]
  }'

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Last updated: 2026-05-21