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Large Language ModelsAI Coding AssistantsZenn AI/MLPublished: Oct 2, 2026, 22:00 JST

Claude Opus 5 / Sonnet 5 / Fable 5.1 migration guide warns of silent API breaks

Claude Opus 5 / Sonnet 5 / Fable 5.1 migration guide warns of silent API breaks

A Zenn guide documents moving Opus 4.x / Sonnet 4.x code to Claude Opus 5 / Sonnet 5 / Fable 5.1, flagging newly failing spots, silent behavior changes, and prompt rewrites. Scanner tools scan.py and prompt_audit.py ship in an attached repository.

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