AGENTS.md

1# src/hooks/rules-injector/ — Conditional Rules Injection
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3**Generated:** 2026-05-15
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5## OVERVIEW
6 
719 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.
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9## HOW IT WORKS
10 
11```
12tool.execute.after (read/write/edit/multiedit)
13  → Extract file path from tool output
14  → Find rule files near that path (finder.ts)
15  → Already injected this session? (cache.ts)
16  → Inject rule content into tool output (injector.ts)
17```
18 
19## TRACKED TOOLS
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21`["read", "write", "edit", "multiedit"]` — triggers only on file manipulation tools.
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23## KEY FILES
24 
25| File | Purpose |
26|------|---------|
27| `hook.ts` | `createRulesInjectorHook()` — wires cache + injector, handles tool events |
28| `injector.ts` | `createRuleInjectionProcessor()` — orchestrates find → cache → inject |
29| `finder.ts` | `findRuleFiles()` + `calculateDistance()` — locate AGENTS.md near target path |
30| `rule-file-finder.ts` | Walk directory tree to find AGENTS.md / .rules files |
31| `rule-file-scanner.ts` | Scan for rule files in a directory |
32| `matcher.ts` | Match file paths against rule file scope |
33| `rule-distance.ts` | Calculate path distance between file and rule file |
34| `project-root-finder.ts` | Find project root (stops at .git, package.json) |
35| `output-path.ts` | Extract file paths from tool output text |
36| `cache.ts` | `createSessionCacheStore()` — per-session injection dedup |
37| `storage.ts` | Persist injected paths across tool calls |
38| `parser.ts` | Parse rule file content |
39| `constants.ts` | Rule file names: `AGENTS.md`, `.rules`, `CLAUDE.md` |
40| `types.ts` | `RuleFile`, `InjectionResult`, `RuleFileScope` |
41 
42## RULE FILE DISCOVERY
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44Priority (closest → farthest from target file):
451. Same directory as target file
462. Parent directories up to project root
473. Project root itself
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49Same-distance tie: all injected. Per-session dedup prevents re-injection.
50 
51## TRUNCATION
52 
53Uses `DynamicTruncator` — adapts injection size based on model context window (1M context models get full content, smaller models get truncated summaries).
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