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Claude 4 Deprecation Checklist: Step-by-Step Migration Before June 15

Claude 4 Opus and Claude Sonnet 4 retire on June 15, 2026. You have 13 days. This checklist walks you through every step — from auditing your codebase to deploying the migration. Follow it top to bottom.

The Complete Checklist

Follow these 8 steps in order. Each one builds on the previous. Total estimated time: under an hour for most projects.

• 1

  Audit Your Codebase

  Find every reference to deprecated model names. Search your entire codebase — including config files, environment variables, and hardcoded strings:

  # Search for Claude 4 Opus references
  grep -r "claude-4-opus" . --include="*.js" --include="*.py" --include="*.ts" --include="*.json" --include="*.yaml" --include="*.yml" --include="*.env" --include="*.toml"
  
  # Search for Claude Sonnet 4 references
  grep -r "claude-sonnet-4" . --include="*.js" --include="*.py" --include="*.ts" --include="*.json" --include="*.yaml" --include="*.yml" --include="*.env" --include="*.toml"

  Also check: database records, admin panels, prompt templates, and any documentation that references the old model names.

  Estimated time: 10 minutes
• 2

  Document Current Costs

  Before migrating, record your current Claude 4 spending. This gives you a baseline to verify savings after migration.

  Check your Anthropic billing dashboard and note your monthly spend on Claude 4 Opus and Sonnet 4. Or use our deprecation calculator to model your costs.

  Model	Monthly Input Tokens	Monthly Output Tokens	Current Cost
  Claude 4 Opus	Your usage	Your usage	Your cost
  Claude Sonnet 4	Your usage	Your usage	Your cost

  Estimated time: 5 minutes
• 3

  Choose Your Replacement

  Decide what to migrate to. The simplest path is Anthropic's newer models. For maximum savings, consider cross-provider alternatives.

  Option	Replace	Price (per M tokens)	Savings	Effort
  Claude Opus 4.8	Claude 4 Opus	$5 / $25	67%	Minimal
  Claude Sonnet 4.6	Claude Sonnet 4	$3 / $15	0% (same price)	Minimal
  GPT-5	Either	$1.25 / $10	89%	Moderate
  Gemini 3.1 Pro	Either	$1 / $5	93%	Moderate
  DeepSeek V4 Pro	Either	$0.44 / $0.87	98%	Higher

  For most teams, Claude Opus 4.8 is the right choice — 67% cheaper, same SDK, same API key, one-line change.

  Estimated time: 5 minutes
• 4

  Update Model Names

  Replace the deprecated model name strings in your code. Here's the mapping:

  Deprecated	Replacement
  claude-4-opus	claude-opus-4-8
  claude-sonnet-4	claude-sonnet-4-6

  Python

  # Before
  client.messages.create(
      model="claude-4-opus",
      messages=[{"role": "user", "content": "Hello"}]
  )
  
  # After
  client.messages.create(
      model="claude-opus-4-8",
      messages=[{"role": "user", "content": "Hello"}]
  )

  Node.js

  // Before
  const response = await anthropic.messages.create({
      model: "claude-4-opus",
      messages: [{ role: "user", content: "Hello" }]
  });
  
  // After
  const response = await anthropic.messages.create({
      model: "claude-opus-4-8",
      messages: [{ role: "user", content: "Hello" }]
  });

  REST API (curl)

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

  Estimated time: 15 minutes
• 5

  Update Environment Variables

  Check your .env files, Docker configs, and deployment settings. Many projects store the model name as an environment variable:

  # .env or .env.local
  # Before
  ANTHROPIC_MODEL=claude-4-opus
  
  # After
  ANTHROPIC_MODEL=claude-opus-4-8

  Also check: Vercel environment variables, AWS Parameter Store, Kubernetes secrets, or any config management system.

  Estimated time: 5 minutes
• 6

  Test in Development

  Before deploying to production, test the new model name with your existing API key. Both old and new model names work until June 15, so you can run parallel tests.

  1. Run your test suite with the new model name
  2. Verify API responses are correct
  3. Check that streaming works (if you use it)
  4. Test function calling / tool use (if applicable)
  5. Verify output quality meets your requirements

  Pro tip: Run the same prompt with both models side-by-side to compare output quality. The new models may produce slightly different results.

  Estimated time: 15 minutes
• 7

  Deploy to Production

  Once tests pass, deploy your changes. Since the API key and SDK don't change, this is a standard code deployment — no infrastructure changes needed.

  1. Commit and push your changes
  2. Deploy to production
  3. Monitor for errors in your first few requests
  4. Verify your Anthropic billing dashboard shows the new model

  Estimated time: 5 minutes
• 8

  Verify Savings

  After 24-48 hours of production usage, check your Anthropic billing dashboard. Your costs should be lower (if you migrated to Claude Opus 4.8) or the same (Sonnet 4.6).

  Use our deprecation calculator to compare your actual savings against projections.

  Estimated time: 2 minutes

  🚨 June 15 deadline: See all 34 alternatives, calculate your savings, and get migration code on our Claude 4 Deprecation Hub.

Common Migration Issues

"Model not found" error

If you get a "model not found" error after deploying, double-check that you replaced all instances of the old model name. Check config files, environment variables, and any hardcoded strings in prompt templates.

Different output quality

Claude Opus 4.8 and Sonnet 4.6 are improvements over their predecessors, but the output may differ slightly for the same prompt. If quality matters for your use case, test with representative prompts before deploying.

Prompt chains with model names in the prompt

If your prompts reference model names (e.g., "You are Claude 4 Opus"), update those references too. The new model names should be used wherever the old ones appear.

Third-party libraries

If you use third-party libraries that wrap the Anthropic API, check if they have hardcoded model names. Some libraries may need updates or configuration changes.

Related Resources

• Claude 4 Stopped Working? — Quick fix guide if your API calls are already failing
• Claude Deprecation Calculator — Calculate your exact migration cost and savings
• Claude 4 Migration Tool — Compare all 34 alternatives with your exact usage
• Claude 4 Migration Guide — Detailed code examples in Python, Node.js, and REST API
• Claude 4 Deprecation FAQ — Every question answered about the deprecation
• Claude 4 Deprecation Countdown — Live countdown and timeline
• Best Claude 4 Alternatives — Detailed comparison of all replacement options
• LLM Pricing Comparison — Compare all 34 models across 10 providers