If you're reading this because your app broke — you're not alone. Thousands of developers woke up to 410 errors on June 15. The good news: you can fix this in 15 minutes. This guide covers what happened, why it happened, and the fastest path to getting your app back online.

What Happened to Claude 4?

On June 15, 2026, Anthropic officially retired Claude 4 Opus and Claude 4 Sonnet. These models were deprecated weeks in advance, with a clear timeline communicated to developers. Here's the timeline:

• May 2026: Anthropic announced Claude 4 deprecation, recommending migration to Opus 4.8 and Sonnet 4.6
• Early June: Deprecation warnings added to API responses, email notifications sent to all Claude 4 API users
• June 15, 2026: Full shutdown — all Claude 4 API endpoints return 410 Gone

The models aren't coming back. Anthropic has fully transitioned to the 4.x generation (Opus 4.8, Sonnet 4.6) and has no plans to restore access to Claude 4.

Why Is My App Breaking?

If your application was using claude-4-opus or claude-4-sonnet as the model ID, every API call now fails. There's no degraded mode, no fallback, and no partial functionality. It's a hard stop.

Common symptoms:

• HTTP 410 "Gone" errors in your logs
• Chat completions endpoint returning empty responses
• Streaming connections dropping immediately
• Your AI features suddenly stop working for all users

What the error looks like

If you're using the Anthropic SDK, here's the exact error you'll see:

// Python (anthropic SDK)
import anthropic
client = anthropic.Anthropic()
response = client.messages.create(
    model="claude-4-opus",  # ← This is the problem
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello"}]
)
# Raises: anthropic.NotFoundError: Error code: 410 -
# {'type': 'error', 'error': {'type': 'not_found_error',
# 'message': 'claude-4-opus has been retired. Please upgrade to
# claude-opus-4-8. See https://docs.anthropic.com/docs/deprecations'}}

// Node.js (@anthropic-ai/sdk)
const response = await client.messages.create({
    model: "claude-4-sonnet",  // ← Deprecated
    max_tokens: 1024,
    messages: [{ role: "user", content: "Hello" }]
});
// Error: 410 model_not_found
// "claude-4-sonnet is no longer available. Use claude-sonnet-4-6."

// curl
curl https://api.anthropic.com/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -d '{"model":"claude-4-opus","max_tokens":1024,"messages":[{"role":"user","content":"Hello"}]}'
# HTTP/1.1 410 Gone
# {"type":"error","error":{"type":"not_found_error","message":"claude-4-opus has been retired"}}

The key detail: HTTP 410 Gone (not 404, not 500). The "Gone" status code specifically means the resource was permanently removed and will never return. This is different from a temporary outage.

The 15-Minute Fix

Migrating from Claude 4 is the simplest model migration you'll ever do. The API format, SDK, authentication, and parameters are identical. You change one string:

grep -r "claude-4-opus\|claude-4-sonnet" --include="*.js" --include="*.ts" --include="*.py" --include="*.json" .

// Before (returns 410 Gone)
model: "claude-4-opus"

// After (official successor)
model: "claude-opus-4-8"

// Or for Sonnet:
model: "claude-sonnet-4-6"

Claude 4 vs What's Available Now

Here's what you were paying vs what you can pay (per 1M tokens):

Best Claude 4 Alternatives (Ranked by Value)

You have more options than ever after the Claude 4 shutdown. Here are the top alternatives ranked by cost-effectiveness:

Want to see all 67 alternatives with live pricing? Check our Claude 4 Migration Hub — it has 18 head-to-head comparisons, migration calculators, and code snippets for every alternative. Or use our Migration Advisor to find your cheapest option in 60 seconds.

See our ranked comparison of the best Claude 4 replacements →

Key Questions After the Shutdown