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3.3 Apply path-specific rules for conditional convention loading

Use .claude/rules/ files with YAML `paths` frontmatter so conventions load only when Claude works on matching files, and choose glob rules over directory CLAUDE.md files when a convention spans directories.

Key points

1
A rule is any .md file under .claude/rules/ (discovered recursively). Scope it with YAML frontmatter between --- markers: paths: followed by a list of globs such as ["terraform/**/*"] or ["**/*.test.tsx"]. paths is the only frontmatter field a rule reads.
2
Rules without a paths field load unconditionally in every session. A scope written as a heading or prose inside the rule does nothing; only the frontmatter counts. Malformed YAML is ignored and the rule loads as unconditional.
3
Path-scoped rules load when Claude reads files matching the pattern, which reduces irrelevant context and token usage in sessions that never touch that area. Splitting into @ imports does not have this effect because imports load at launch.
4
Glob cheat sheet: **/*.ts matches every TypeScript file anywhere; src/**/* everything under src/; *.md only root-level Markdown; src/components/*.tsx one directory. Brace expansion (**/*.{test,spec}.ts) covers several extensions in one pattern; a rule may list several patterns.
5
Choose a glob rule over subdirectory CLAUDE.md files when the convention follows a file type spread across the codebase (colocated *.test.tsx files, *.sql migrations in many folders). Directory CLAUDE.md files are directory-bound and cannot follow a naming pattern.
6
Choose a subdirectory CLAUDE.md when the convention is confined to one directory, especially when that directory's maintainers should own the file without editing the shared .claude/ folder.
7
Over-broad globs are a common diagnosis: **/api/** also matches docs/api/ and fixtures. Tighten to the real roots and extension (src/api/**/*.ts, services/*/api/**/*.ts) rather than adding prose caveats.
8
Personal rules go in ~/.claude/rules/ and apply to every project on that machine; they load before project rules but do not override them, so keep the two consistent.
9
Distractors the exam uses: consolidating every convention in the root CLAUDE.md and relying on inference, a CLAUDE.md in every folder, skills that must be invoked, and permission settings, none of which give deterministic path-based loading.

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