Claude 4 Deprecated: Complete Migration Guide for Developers

Anthropic is retiring Claude 4 Opus and Claude Sonnet 4 on June 15, 2026. If your code uses claude-4-opus or claude-sonnet-4 as the model name, it will break after the deadline.

The good news: migration is a one-line change per model reference, and the direct replacements are 67% cheaper. This guide covers exactly what changed, how to migrate, and which alternative models save you the most money.

What's Changing

Anthropic is deprecating two model IDs:

Your Anthropic API key, SDK, and endpoint stay the same. Only the model string changes.

How to Migrate (Step by Step)

Step 1: Find model references in your code

Search your codebase for the deprecated model strings:

# Find all references to deprecated models
grep -r "claude-4-opus\|claude-sonnet-4" ./src/

Step 2: Update the model string

Replace the deprecated model ID with the new one:

# Before (deprecated)
model = "claude-4-opus"

# After
model = "claude-opus-4-8"  # Claude Opus 4.8 — 67% cheaper, 5x context

For Sonnet:

# Before (deprecated)
model = "claude-sonnet-4"

# After
model = "claude-sonnet-4-6"  # Claude Sonnet 4.6 — same price, 5x context

Step 3: Test your integration

Run your existing test suite. The API behavior is identical — only the model string changes. No SDK updates, no API key changes, no endpoint changes.

Step 4: Update environment variables

If you store model names in environment variables or config files:

# .env or config
ANTHROPIC_MODEL=claude-opus-4-8      # was claude-4-opus
ANTHROPIC_MODEL_SONNET=claude-sonnet-4-6  # was claude-sonnet-4

Top 5 Claude 4 Alternatives Compared

If you want to migrate to a cheaper model (not just the direct replacement), here are the top 5 alternatives ranked by cost savings:

Need more options? Use the Provider Switch Calculator to compare all 34 models side by side.

Code Examples: Migration by Language

Python (Anthropic SDK)

# Before
import anthropic
client = anthropic.Anthropic()
message = client.messages.create(
    model="claude-4-opus",  # DEPRECATED
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello"}]
)

# After
message = client.messages.create(
    model="claude-opus-4-8",  # Claude Opus 4.8
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello"}]
)

Node.js (Anthropic SDK)

// Before
const message = await anthropic.messages.create({
    model: 'claude-4-opus',  // DEPRECATED
    max_tokens: 1024,
    messages: [{ role: 'user', content: 'Hello' }]
});

// After
const message = await anthropic.messages.create({
    model: 'claude-opus-4-8',  // Claude Opus 4.8
    max_tokens: 1024,
    messages: [{ role: 'user', content: 'Hello' }]
});

cURL

# Before
curl https://api.anthropic.com/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -d '{"model": "claude-4-opus", ...}'  # DEPRECATED

# After
curl https://api.anthropic.com/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -d '{"model": "claude-opus-4-8", ...}'

Migration Checklist

1. Search codebase for claude-4-opus and claude-sonnet-4
2. Update model strings to claude-opus-4-8 / claude-sonnet-4-6
3. Update config files and environment variables
4. Run tests — behavior is identical, just the model string changes
5. Deploy before June 15, 2026

FAQ

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