Developer builds grounding rules to stop LLMs fabricating software breaking changes

A developer building a tool to track breaking changes in releases of React, TypeScript, and Vite has detailed the techniques used to prevent large language models from inventing migration requirements. The system prompt strictly instructs the model to use only the release notes provided in the user message, explicitly barring it from drawing on prior training knowledge about a project. Requests are blocked entirely if notes are absent or exceed 80,000 characters, since truncated input can produce confidently wrong summaries. The model is asked to list breaking changes verbatim from the notes rather than infer them, and version numbers are treated purely as metadata, not as evidence of what changed. To enable accurate source linking, the model returns exact quoted text from the notes rather than line numbers, which models are known to miscalculate silently.