Path-specific rules for conditional loading

A rule file in .claude/rules/ can carry a paths field in its YAML frontmatter — the settings block at the top of the file — holding glob patterns. The rule then loads only when the file being edited matches.

paths: ["terraform/**/*"]

paths is also what makes a rule conditional at all. A rule file with no paths field loads unconditionally, on every turn, like always-loaded configuration that happens to live in the rules directory. That's intended, not an error: storing a file in .claude/rules/ splits configuration into topics, and adding paths is the separate decision that narrows one.

Glob mechanics decide whether a rule ever fires

A single * matches within one directory level and doesn't cross a /. A double ** descends through directories.

pattern            file being edited        match?
*.py               main.py                  yes
*.py               src/pipeline/main.py     no   (* stops at the /)
**/*.py            src/pipeline/main.py     yes
packages/api/**/*  packages/api/db/pool.ts  yes

So paths: ["*.py"] matches Python files only at the repository root. It does not match Python files in subdirectories. A convention that applies throughout the repository needs the **/ prefix.

It matches the file, not the person

Rules posted in a study room belong to the room: whoever books it that hour follows them, whichever department they came from. There is no way to post a rule that applies only to you.

The glob is evaluated against the path of the file in hand. It knows nothing about who is editing, which team they belong to, or where the session started. The rule file's own location doesn't limit its reach either. Every rule lives in .claude/rules/, but its pattern can match files anywhere in the repository. Anyone opening a file under packages/checkout/ gets the checkout conventions, because those conventions belong to the code. That also sets a limit: paths cannot express a personal preference, which has no path to attach to.

Why conditional loading matters

Rules that are always loaded cost context on every turn, whether or not they are relevant. Conditional loading means Terraform conventions are present when you edit Terraform and absent when you don't — less irrelevant context, fewer tokens, and less noise competing for attention.

When globs are the better choice

Directory-level CLAUDE.md covers a place. Glob rules cover a kind of file.

Test files are the clearest example: **/*.test.tsx matches them wherever they live. Expressing that with directory CLAUDE.md files would mean one per directory containing tests, duplicated and drifting apart.

The rule of thumb: if a convention follows a file type rather than a location, use a path-scoped rule. If it genuinely belongs to one part of the tree, either works — with one point for the rule file, which keeps every rule in one directory somebody can review at once.