Anthropic to retire Claude Sonnet 4.5 on November 30, 2026

Anthropic moved Claude Sonnet 4.5 (id claude-sonnet-4-5-20250929) to Deprecated status on September 30, 2026. Requests to that id will fail after November 30, 2026, with no grace period; the recommended replacement is claude-sonnet-5-5 at the same price with a 1M token context window.

• Deprecation notice posted September 30, 2026, giving 61 days to migrate
• After November 30, 2026, requests to claude-sonnet-4-5-20250929 will fail with no grace period
• Replacement claude-sonnet-5-5 costs the same and keeps the 1M token context window
• Bedrock and Google Cloud set their own retirement dates, so Anthropic's deadline may not apply