Claude Opus 4 vs Claude Sonnet 4.6: Which AI Model Should You Choose?

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.RAILWAIL_API_KEY,
  baseURL: "https://railwail.com/v1",
});

// Before — using Claude Opus 4
let r = await client.chat.completions.create({
  model: "claude-opus-4-20250514",
  messages: [{ role: "user", content: "Hello" }],
});

// After — switched to Claude Sonnet 4.6
r = await client.chat.completions.create({
  model: "claude-sonnet-4-6-20260217",
  messages: [{ role: "user", content: "Hello" }],
});

from openai import OpenAI

client = OpenAI(
    api_key=os.environ["RAILWAIL_API_KEY"],
    base_url="https://railwail.com/v1",
)

# Before — using Claude Opus 4
r = client.chat.completions.create(
    model="claude-opus-4-20250514",
    messages=[{"role": "user", "content": "Hello"}],
)

# After — switched to Claude Sonnet 4.6
r = client.chat.completions.create(
    model="claude-sonnet-4-6-20260217",
    messages=[{"role": "user", "content": "Hello"}],
)

# Before — using Claude Opus 4
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-opus-4-20250514",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

# After — switched to Claude Sonnet 4.6
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-6-20260217",
    "messages": [{"role": "user", "content": "Hello"}]
  }'