Apply path-specific rules for conditional convention loading

Path-specific rules solve a targeting problem. Directory-level CLAUDE.md files scope conventions by location; path-specific rules scope them by file pattern. Many real conventions are file-type conventions, and those files are scattered across the tree.

A rule file in .claude/rules/ can carry YAML frontmatter with a paths field containing glob patterns.³³ The rule is then activated conditionally: it loads only when a file that is read or edited matches one of those globs. A Terraform rule with paths: ["terraform/**/*"] is invisible while you work on the React frontend, and appears the moment you touch infrastructure code.

Why conditional loading matters

Two effects, and the exam cares about both:

• Less irrelevant context. Claude is not reading Terraform naming conventions while fixing a CSS bug, so the instructions it does see are all relevant to the task.
• Lower token usage. Always-loaded memory is paid for in every session. Path-scoped rules are paid for only in the sessions that need them, which is what lets a large team keep a genuinely detailed rule set without bloating every conversation.

Globs vs directory-level CLAUDE.md

This is the discrimination the exam tests. Use a directory-level CLAUDE.md when the convention really is about a place: everything under services/billing/ must go through the ledger client. Use a path-scoped rule when the convention is about a kind of file that spans multiple directories:³⁵

• **/*.test.tsx — test conventions, when tests sit next to the code they test all over the repo.
• **/migrations/*.sql — migration safety rules, one folder per service.
• terraform/**/* — infrastructure conventions.

With directory-level files you would have to duplicate the same test conventions into a CLAUDE.md in every directory that happens to contain tests, and then keep those copies in sync forever. A single glob-scoped rule file expresses the intent once, applies it by file type regardless of directory location, and stays out of context when it does not apply.

Path-scoped rule or skill?

Migrations show up on both sides of this line, so fix the discriminator now. A procedure you invoke — the steps for generating a migration — belongs in a skill (3.2). A convention that should apply whenever matching files come into play — migrations must be reversible — belongs in a path-scoped rule. Same subject, different trigger: one is called on demand, the other activates from the files read or edited.

The mental model: paths turns a rule from "always on" into "on when relevant", and the glob is how you express relevance.

One operational note: after /compact, a project-root CLAUDE.md is re-read from disk, but path-scoped rules are not — they reload the next time a matching file comes up.³³

---
description: Frontend test conventions
paths: ["**/*.test.tsx", "**/*.test.ts"]
---

# Test conventions

- Use React Testing Library. Never add snapshot tests.
- Query by accessible role or label, never by test id.
- One top-level describe block per exported symbol.
- Shared fixtures live in tests/fixtures/; do not build ad hoc factories.
- Assert on user-visible behavior, not on internal state.

---
description: Terraform module and tagging conventions
paths:
  - "terraform/**/*"
  - "**/*.tf"
---
# body: the actual conventions follow as markdown