Stage 2 · Lesson 4 of 6
Rules that apply to some files
Some guidance only matters for part of the codebase, such as " handlers validate input with zod" or "tests use the factory helpers". Rather than loading it in every session, put it in a scoped rule that loads only when the tool works on matching files, described with a , a file pattern with wildcards that can match, say, every TypeScript file under src/api.
Claude Code uses files in .claude/rules/ with a paths list in the . Cursor uses .mdc rules with globs. Copilot in uses .instructions.md files in .github/instructions/ with applyTo. Scoped rules keep the main file short and put guidance next to the code it governs.
Common trapa pattern that matches nothing, so the rule silently never loads; test it by asking the tool which rules it is following.
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Resources for this stage
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- GitHub repoFreeGitHub Skills: Getting Started with GitHub Copilot
GitHub · Beginner
A free hands-on exercise in a browser Codespace, done in under an hour