Claude 4 Deprecation: Sonnet 4 and Opus 4 Retire June 15, 2026

If you’re still running the original Claude Sonnet 4 or Opus 4 model strings in production, you have a hard deadline: June 15, 2026. After that date, calls to claude-sonnet-4-20250514 and claude-opus-4-20250514 will fail on the Anthropic API. Here’s exactly what’s being deprecated, what to migrate to, and what you’ll gain from upgrading.

What’s Being Deprecated

Anthropic is retiring the original Claude 4.0 model versions — the ones that shipped in May 2025. These are distinct from the 4.x versions released since. The specific API strings going offline:

These are not the latest Claude 4 models. If you’ve been on Anthropic’s recommended defaults, you’re likely already on 4.6. This deprecation primarily affects teams that pinned specific model version strings in their API calls rather than using the alias endpoints.

What to Migrate To

Anthropic’s recommendation is a direct version bump within the same model tier:

The 4.6 models are meaningful upgrades — not just version bumps. Claude Sonnet 4.6 ships with near-Opus-level performance on coding and document tasks, dramatically improved computer use capabilities, and a 1 million token context window in beta. Claude Opus 4.6 adds the same 1M context window alongside improvements to long-horizon reasoning and multi-step agentic work.

Why Anthropic Deprecates Models

Anthropic follows a predictable model lifecycle: new versions within a generation ship as upgrades, and older version strings are retired on a roughly 12-month timeline after a successor is available. This keeps the API surface clean and pushes users toward better-performing models. The deprecation of the original Claude 4.0 strings follows the same pattern as prior Claude 3 and 3.5 retirements.

For most API users, the migration is a one-line change — swap the model string. Prompting styles, tool use conventions, and JSON response formats are stable across 4.x generations. Anthropic has not announced breaking changes that would require prompt rewrites when moving from 4.0 to 4.6.

How This Fits the Claude 4 Generation Timeline

What If You Don’t Migrate Before June 15?

API calls to claude-sonnet-4-20250514 or claude-opus-4-20250514 after June 15, 2026 will return errors. There is no automatic failover to a newer model — the call simply fails. If you have any production systems, scheduled jobs, or automated pipelines using these version strings, audit them now. A global search for 20250514 in your codebase is the fastest way to find exposure.

What Comes After Claude 4.x

Claude 5 is expected in Q2-Q3 2026, based on Anthropic’s release cadence and early signals from Vertex AI deployment logs. As has been the pattern with prior generations, Claude 5’s mid-tier Sonnet model is expected to outperform the current Opus 4.6 on most benchmarks at a lower price point. No official announcement has been made as of April 2026.