Claude 4 Deprecation in 6 Days — Complete Migration Checklist

The clock is ticking. Anthropic's Claude 4 Opus and Claude Sonnet 4 will be permanently retired on June 15, 2026 — just 6 days from now. After that date, every API call to these models returns an HTTP 410 Gone error.

If your application uses claude-4-opus or claude-sonnet-4, it will stop working. No grace period. No warnings. Just errors.

The good news: migrating takes about 15 minutes, and you'll actually save 67% on costs while getting 5x more context. Here's everything you need.

What's Changing

The 15-Minute Migration Plan

Step 1: Find all model ID references (5 min)

Search your codebase for the old model IDs:

# Find all files using Claude 4
grep -r "claude-4-opus" . --include="*.py" --include="*.js" --include="*.ts" --include="*.go" --include="*.env"
grep -r "claude-sonnet-4" . --include="*.py" --include="*.js" --include="*.ts" --include="*.go" --include="*.env"

Step 2: Update model IDs (5 min)

Replace the old model IDs with the new ones:

Step 3: Update your code (3 min)

Python (Anthropic SDK):

# Before
client = anthropic.Anthropic()
response = client.messages.create(
    model="claude-4-opus",  # ← This will break June 15
    max_tokens=4096,
    messages=[{"role": "user", "content": "Hello"}]
)

# After — just change the model ID
response = client.messages.create(
    model="claude-opus-4-8",  # ← Updated
    max_tokens=4096,
    messages=[{"role": "user", "content": "Hello"}]
)

JavaScript/TypeScript:

// Before
const response = await anthropic.messages.create({
    model: "claude-sonnet-4",  // ← This will break June 15
    max_tokens: 4096,
    messages: [{ role: "user", content: "Hello" }]
});

// After — just change the model ID
const response = await anthropic.messages.create({
    model: "claude-sonnet-4-6",  // ← Updated
    max_tokens: 4096,
    messages: [{ role: "user", content: "Hello" }]
});

Environment variables:

# .env file
# Before
ANTHROPIC_MODEL=claude-4-opus

# After
ANTHROPIC_MODEL=claude-opus-4-8

Step 4: Add a fallback chain (2 min)

Don't get caught off guard. Add a fallback so your app degrades gracefully:

const MODELS = {
    primary: "claude-opus-4-8",
    fallback1: "claude-sonnet-4-6",
    fallback2: "gpt-5"  // Cross-provider fallback
};

async function callAI(messages) {
    for (const model of Object.values(MODELS)) {
        try {
            return await anthropic.messages.create({
                model, max_tokens: 4096, messages
            });
        } catch (e) {
            if (e.status === 410) continue; // Model deprecated
            throw e;
        }
    }
    throw new Error("All models exhausted");
}

Step 5: Test and deploy (5 min)

Cost Comparison: Claude 4 vs Claude Opus 4.8

For a workload of 10M input + 5M output tokens per month:

• Claude 4 Opus: $150 input + $375 output = $525/month
• Claude Opus 4.8: $50 input + $125 output = $175/month
• You save $350/month ($4,200/year) by migrating to Opus 4.8

Alternative Migration Paths

If you're not tied to Anthropic, consider these alternatives:

Don't Wait Until June 14

Every year, developers get caught by API deprecations. The model IDs above will start returning 410 Gone errors on June 15. If you're reading this on June 9, you have 6 days. That's plenty of time — but only if you start now.

The migration is genuinely simple: change one string in your code. The hardest part is finding everywhere that string appears. Use grep, fix it all, add a fallback, test, deploy. 15 minutes.

And the upside? You'll save 67% on costs and get 5x more context window. This isn't just a migration — it's an upgrade.