Claude Sonnet 4 and Opus 4 retired on the Claude API

What's new

• Retirement of the original 4.0 models: claude-sonnet-4-20250514 and claude-opus-4-20250514 now return errors on every call as of June 15, 2026.
• Recommended migration: Sonnet 4 → Sonnet 4.6, Opus 4 → Opus 4.8.
• External Researcher Access Program: researchers can request ongoing access to the retired snapshots.
• Consumer claude.ai and Claude Code are unaffected – Anthropic manages model selection there automatically.

Why it matters

This is the oldest Claude 4 generation, still pinned in many enterprise apps in production. The retirement was telegraphed back in April 2026 but many teams kept postponing the migration.

How to try it

Check your configs for hard-coded model IDs and switch to claude-sonnet-4-6 / claude-opus-4-8, or jump straight to claude-opus-4-7 for heavier agentic workloads.