diff --git a/packages/tools/cli/bin/ua.js b/packages/tools/cli/bin/ua.js
index eb85cb5..048557b 100644
--- a/packages/tools/cli/bin/ua.js
+++ b/packages/tools/cli/bin/ua.js
@@ -56,6 +56,13 @@ function collectManifests() {
   return out;
 }
 
+/*** 内容无变化则跳过写入（幂等，行尾归一化防 CRLF 误判），避免时间戳刷新弄脏工作区 ***/
+function writeIfChanged(file, content) {
+  if (fs.existsSync(file) && fs.readFileSync(file, 'utf8').replace(/\r\n/g, '\n') === content) return false;
+  fs.writeFileSync(file, content);
+  return true;
+}
+
 /*** 聚合清单，生成 .ua/index.json 与 llms.txt ***/
 function cmdIndex() {
   const packages = collectManifests();
@@ -66,7 +73,11 @@ function cmdIndex() {
     repoRoot: '.',
     packages,
   };
-  fs.writeFileSync(INDEX_FILE, JSON.stringify(index, null, 2) + '\n');
+  // 幂等：剔除 generatedAt 后内容一致即不写入，连续 check 不弄脏工作区
+  const json = JSON.stringify(index, null, 2) + '\n';
+  const stripTs = (s) => s.replace(/"generatedAt": "[^"]*"/, '"generatedAt": ""');
+  const changed = !fs.existsSync(INDEX_FILE) || stripTs(fs.readFileSync(INDEX_FILE, 'utf8').replace(/\r\n/g, '\n')) !== stripTs(json);
+  if (changed) fs.writeFileSync(INDEX_FILE, json);
 
   const lines = [
     '# @ui-arch 私人组件库索引',
@@ -87,8 +98,8 @@ function cmdIndex() {
     for (const c of p.conventions ?? []) lines.push(`- 约定: ${c}`);
     lines.push('');
   }
-  fs.writeFileSync(LLMS_FILE, lines.join('\n'));
-  console.log(`indexed ${packages.length} package(s) -> .ua/index.json, llms.txt`);
+  writeIfChanged(LLMS_FILE, lines.join('\n'));
+  console.log(`indexed ${packages.length} package(s) -> .ua/index.json, llms.txt${changed ? '' : ' (unchanged, skip)'}`);
 }
 
 /*** 读取注册表索引；缺失则报错退出 ***/