TLDR Tech / Practical
Anthropic's Claude Sonnet 5.5 replaces 4.5, requires code changes
Anthropic is retiring Claude Sonnet 4.5 on November 30, 2026, and recommends migrating to Claude Sonnet 5.5. The author notes that standard Go tools do not detect incompatibilities when upgrading, as Sonnet 5.5 introduces breaking changes. These include rejecting certain parameter configurations, disabling assistant message prefill, and altering thinking behavior.
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