Claude Sonnet 4 and Opus 4 retire June 15

Sources: Anthropic model deprecations, migration guide
Summary: claude-sonnet-4-20250514 and claude-opus-4-20250514 are removed from the Claude API at 09:00 PT on 2026-06-15. No grace period. Requests to retired model IDs will fail immediately. Successors are claude-sonnet-4-6 and claude-opus-4-8.
Why it matters: Any production integration still pinning the May 2025 model IDs will break on Monday morning.
Follow-up: Confirm migration complete and no breakage after June 15.