From 46b965b9daa2ca3e9c4bcc4d74defbbe4deb10c2 Mon Sep 17 00:00:00 2001
From: YeonGyu-Kim <code.yeon.gyu@gmail.com>
Date: Mon, 18 May 2026 12:36:33 +0900
Subject: [PATCH] fix(rules-injector): bound matcher cache

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
---
 src/hooks/rules-injector/matcher.test.ts | 13 +++++++++++++
 src/hooks/rules-injector/matcher.ts      | 13 ++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/hooks/rules-injector/matcher.test.ts b/src/hooks/rules-injector/matcher.test.ts
index 009c19645..fce36bc4e 100644
--- a/src/hooks/rules-injector/matcher.test.ts
+++ b/src/hooks/rules-injector/matcher.test.ts
@@ -30,6 +30,19 @@ describe("shouldApplyRule", () => {
     expect(getMatcherCacheStats()).toEqual({ entries: 2 })
   })
 
+  it("#given many unique globs #when matching repeatedly #then matcher cache stays bounded", () => {
+    // given
+    const projectRoot = "/workspace/project"
+
+    // when
+    for (let index = 0; index < 300; index += 1) {
+      shouldApplyRule({ globs: `src/file-${index}.ts` }, `${projectRoot}/src/file-${index}.ts`, projectRoot)
+    }
+
+    // then
+    expect(getMatcherCacheStats().entries <= 256).toBe(true)
+  })
+
   it("#given matching glob #when path is under project root #then returns matching reason", () => {
     // given / when
     const result = shouldApplyRule({ globs: "src/**/*.ts" }, "/workspace/project/src/index.ts", "/workspace/project")
diff --git a/src/hooks/rules-injector/matcher.ts b/src/hooks/rules-injector/matcher.ts
index d68dae109..cd6995f6e 100644
--- a/src/hooks/rules-injector/matcher.ts
+++ b/src/hooks/rules-injector/matcher.ts
@@ -15,13 +15,24 @@ export interface MatcherCacheStats {
 }
 
 const PICOMATCH_OPTIONS = { dot: true, bash: true } as const
+const MAX_MATCHER_CACHE_ENTRIES = 256
 const matcherCache = new Map<string, PathMatcher>()
 
 function matcherFor(pattern: string): PathMatcher {
   const cached = matcherCache.get(pattern)
-  if (cached) return cached
+  if (cached) {
+    matcherCache.delete(pattern)
+    matcherCache.set(pattern, cached)
+    return cached
+  }
 
   const matcher = picomatch(pattern, PICOMATCH_OPTIONS)
+  if (matcherCache.size >= MAX_MATCHER_CACHE_ENTRIES) {
+    const oldestPattern = matcherCache.keys().next().value
+    if (oldestPattern !== undefined) {
+      matcherCache.delete(oldestPattern)
+    }
+  }
   matcherCache.set(pattern, matcher)
   return matcher
 }