diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..2bc648d
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2024-05-14 - Optimize file system traversal
+**Learning:** `fs.readdirSync(..., { withFileTypes: true })` is significantly faster than combining `fs.readdirSync` with `fs.statSync` in Node.js because it avoids extra syscalls for statting files that can be returned directly by the directory read. This was a critical bottleneck when recursively reading large sets of spec markdown files in this local-first CLI.
+**Action:** Always prefer `withFileTypes: true` when doing recursive directory reads in Node.js, unless we specifically need full stat info.
diff --git a/src/files.ts b/src/files.ts
index b1e1e43..07462ea 100644
--- a/src/files.ts
+++ b/src/files.ts
@@ -1,4 +1,4 @@
-import { existsSync, readdirSync, readFileSync, statSync } from "node:fs";
+import { existsSync, readdirSync, readFileSync } from "node:fs";
 import { basename, dirname, join, relative, resolve } from "node:path";
 
 export type VspecConfig = { vspec_format: 1; key_prefix: string; spec_language?: "ko" | "en" | "match-input" };
@@ -27,10 +27,9 @@ export function projectKey(start = process.cwd()): string | null {
 export function walkFiles(root: string, predicate: (path: string) => boolean): string[] {
   if (!existsSync(root)) return [];
   const files: string[] = [];
-  for (const entry of readdirSync(root)) {
-    const path = join(root, entry);
-    const stat = statSync(path);
-    if (stat.isDirectory()) files.push(...walkFiles(path, predicate));
+  for (const entry of readdirSync(root, { withFileTypes: true })) {
+    const path = join(root, entry.name);
+    if (entry.isDirectory()) files.push(...walkFiles(path, predicate));
     else if (predicate(path)) files.push(path);
   }
   return files.sort();