src/hooks/rules-injector/ — Conditional Rules Injection

Generated: 2026-02-21

OVERVIEW

19 files (~1604 LOC). The rulesInjectorHook — Tool Guard Tier hook that auto-injects AGENTS.md (and similar rule files) into context when a file in a directory is read, written, or edited. Proximity-based: closest rule file to the target path wins.

HOW IT WORKS

tool.execute.after (read/write/edit/multiedit)
  → Extract file path from tool output
  → Find rule files near that path (finder.ts)
  → Already injected this session? (cache.ts)
  → Inject rule content into tool output (injector.ts)

TRACKED TOOLS

["read", "write", "edit", "multiedit"] — triggers only on file manipulation tools.

KEY FILES

File	Purpose
`hook.ts`	`createRulesInjectorHook()` — wires cache + injector, handles tool events
`injector.ts`	`createRuleInjectionProcessor()` — orchestrates find → cache → inject
`finder.ts`	`findRuleFiles()` + `calculateDistance()` — locate AGENTS.md near target path
`rule-file-finder.ts`	Walk directory tree to find AGENTS.md / .rules files
`rule-file-scanner.ts`	Scan for rule files in a directory
`matcher.ts`	Match file paths against rule file scope
`rule-distance.ts`	Calculate path distance between file and rule file
`project-root-finder.ts`	Find project root (stops at .git, package.json)
`output-path.ts`	Extract file paths from tool output text
`cache.ts`	`createSessionCacheStore()` — per-session injection dedup
`storage.ts`	Persist injected paths across tool calls
`parser.ts`	Parse rule file content
`constants.ts`	Rule file names: `AGENTS.md`, `.rules`, `CLAUDE.md`
`types.ts`	`RuleFile`, `InjectionResult`, `RuleFileScope`

RULE FILE DISCOVERY

Priority (closest → farthest from target file):

Same directory as target file
Parent directories up to project root
Project root itself

Same-distance tie: all injected. Per-session dedup prevents re-injection.

TRUNCATION

Uses DynamicTruncator — adapts injection size based on model context window (1M context models get full content, smaller models get truncated summaries).

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