Build CLAUDE.md (and GEMINI.md) Rules Files for Your Projects

One of the highest-ROI things you can do: create a CLAUDE.md (or equivalent) in your repo root with coding style rules, patterns to avoid, preferred libraries, and lint requirements. When you load this at the start of each session, the model adheres to your conventions instead of defaulting to generic patterns. Copilot and Cursor both support similar project-level instruction files.

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Sources: Addy Osmani's Blog · Stack Overflow Blog: Coding Guidelines for AI