Module path_rules 

BP-5 (catalog D2 “Path-scoped rules”: rule files activated only when matching files are touched; cc§2 “.claude/rules/*.md — modular instruction files; optional paths: frontmatter scopes a rule to file globs so it loads only when Claude touches matching files”).

A prompt-assembly input, not a module. A rule file is an instruction file that happens to carry a selector. There are exactly two ways it can reach a prompt, and both are doors that already existed:

• No paths: — it joins the instruction blob at construction, beside CLAUDE.md/AGENTS.md, under the same core.project_context byte budget (agent::assemble_project_instructions).
• With paths: — it is held back, and injected as a tool-result notice the first time a tool touches a matching file. That is the exact mechanism core.nested_instructions already uses for a subdirectory’s own CLAUDE.md (tools::builtins::nested_instructions_notice), with the selector swapped from “the directory you touched” to “a glob this rule declares”. Each rule is injected at most once per session, deduped by path, exactly as nested instructions are.

Roots. <CLAUDE_CONFIG_DIR>/rules/ (the user tier) and .claude/rules/ in each directory of the instruction walk (docs:memory#organize-rules-with-claude-rules). Read only when [core.path_rules] is on; a config that does not set it opens no directory at all.

Structs

RuleFile

One .claude/rules/*.md file.

Functions

always_on_text

The unscoped rules’ contribution to the instruction blob, in load order. Empty when nothing is unscoped.

load

Every rule file config loads, user tier first, then the instruction walk from the outermost root down to cwd — the same root→cwd ordering instruction files use, so the nearest rule is read last. Empty (and free of any filesystem work) when [core.path_rules] is off.