Claude Sonnet 4 and Opus 4 Shut Down June 15: The Two-Week Routing Migration You Can't Skip

Two weeks from today, any API call that still uses claude-sonnet-4-20250514 or claude-opus-4-20250514 will fail. Anthropic deprecated both model IDs on April 14, 2026, and the hard shutdown is June 15, 2026 at 9 AM PT. If your routing layer, fallback chain, or SDK default still references either of these strings, you have a production incident waiting to happen.

This is not a soft deprecation where the model silently redirects. It is a full retirement: the model IDs stop responding.

What happened

Anthropic announced on April 14, 2026 that the original Claude 4 generation — claude-sonnet-4-20250514 and claude-opus-4-20250514, both released May 22, 2025 — would be retired on June 15, 2026. The recommended replacements are:

• claude-sonnet-4-20250514 → claude-sonnet-4-6 (active, supported until at least February 17, 2027)
• claude-opus-4-20250514 → claude-opus-4-8 (active, supported until at least April 16, 2027)

The -20250514 suffix models were the original Claude 4 launch versions. They have been superseded by multiple point releases since then. The 4.6 and 4.8 variants are not just renamed aliases — they carry capability improvements, better tool use, and updated safety tuning.

Why it matters for AI engineering teams

The failure mode here is silent until it isn't. Teams that hardcoded model IDs at integration time — in environment variables, routing configs, SDK initializers, or prompt management systems — often don't revisit those strings until something breaks. June 15 is the break point.

Three places where this tends to hide:

Routing and gateway configs. If you're running a proxy or gateway that maps incoming requests to specific model IDs, any rule that names claude-sonnet-4-20250514 or claude-opus-4-20250514 will start returning 404 or 400 errors after the shutdown. The error won't be a graceful fallback — it will be a hard API rejection.

Fallback chains. Teams that set up fallback logic like "try Opus 4, fall back to Sonnet 4" using the original model IDs will find both legs of the fallback broken simultaneously. If your fallback was designed to handle provider outages but not model retirements, this is the gap.

SDK and library defaults. Some integrations set a model ID once at initialization and never revisit it. Claude Code, LangChain, and similar tools that were configured against the original Claude 4 IDs need to be updated. Check your .env files, settings.json, and any infrastructure-as-code that references these strings.

The router/operator angle

Model deprecations are a recurring operational pattern, not a one-time event. Anthropic has now retired eight Claude models in twelve months. The cadence is roughly: new generation ships, previous generation gets a 60-90 day deprecation window, then hard shutdown. OpenAI follows a similar pattern. This is the new normal for teams running production AI workloads.

The routing implication is that pinning to dated model IDs is a liability. The safer pattern is to pin to the latest stable alias within a generation — claude-sonnet-4-6 rather than claude-sonnet-4-20250514 — and treat the alias as your routing target. Aliases get updated to point to the latest safe version within a family; dated IDs do not.

For teams running multi-provider routing, this is also a reminder to audit your fallback model list. A fallback that points to a retired model is worse than no fallback: it adds latency before the real error surfaces.

Migration checklist for June 15:

• Search your codebase and configs for claude-sonnet-4-20250514 and claude-opus-4-20250514
• Replace with claude-sonnet-4-6 and claude-opus-4-8 respectively
• Update any routing rules, gateway configs, or proxy model maps
• Verify fallback chains don't reference the deprecated IDs
• Check Claude Code settings.json and any .env files with ANTHROPIC_MODEL or similar
• Test the updated model IDs in staging before June 15

What TheRouter users should watch or try

If you're routing Anthropic traffic through TheRouter, verify that your model routing rules reference the current model IDs. The June 15 deadline applies to any system that calls the Anthropic API directly — including traffic routed through a gateway that passes the model ID through to Anthropic.

More broadly, this deprecation cycle is a good prompt to review your routing policy for all providers: are you pinning to dated model IDs anywhere? The pattern of "latest stable alias" over "specific dated version" reduces the operational surface area for future deprecation events.

Anthropic's full deprecation history and current model status table is at platform.claude.com/docs/en/about-claude/model-deprecations.