Claude Sonnet 4.5 deprecated, retires 2026-09-29 → Claude Sonnet 5.5

Anthropic has deprecated Claude Sonnet 4.5 (claude-sonnet-4-5-20250929), with retirement set for 2026-09-29, according to the provider's model deprecation announcement. The model, which supports text and vision with a 1000k context window and 64k max output, is being succeeded by Claude Sonnet 5.5. The deprecation affects code that calls the model under aliases including claude-sonnet-4-5, claude-sonnet-4.5, and anthropic/claude-sonnet-4-5.

AN✕ Retired Claude Sonnet 4.5 Anthropic · claude-sonnet-4-5-20250929 Claude Sonnettext+vision1000k context64k max out also matches: claude-sonnet-4-5-20250929 claude-sonnet-4-5 claude-sonnet-4.5 microsoft/claude-sonnet-4-5 anthropic/claude-sonnet-4-5-20250929 anthropic/claude-sonnet-4-5 provider announcement → https://docs.claude.com/en/docs/about-claude/model-deprecations Does your code call Claude Sonnet 4.5? $ curl -fsSL https://llmstatus.ai/install.sh | bash Then mm status in any repo — it finds every model you use and flags the ones on a clock. No account, nothing uploaded. Get alerted before it retires → https://llmstatus.ai/sign-up