diff --git a/action.yml b/action.yml
index 8a391e4..fc5dff4 100644
--- a/action.yml
+++ b/action.yml
@@ -1,5 +1,5 @@
 # 檔案用途：定義 CLEANUP OLD RELEASES 這個 Docker action 的輸入參數與執行環境
-# 更新日期：2026/07/15 11:17:00
+# 更新日期：2026/07/15 13:05:00
 
 # Action 名稱，會顯示在 action 市集與文件中
 name: 'CLEANUP OLD RELEASES'
@@ -12,10 +12,10 @@ author: 'Jeffery'
 
 # 定義可由使用者或呼叫端傳入的輸入參數
 inputs:
-  # KEEP_COUNT 用於控制保留的 release 數量
+  # KEEP_COUNT 用於控制保留的 release 數量；正式版與預發行版（prerelease）分組各自保留這個數量
   KEEP_COUNT:
-    # 參數說明，這裡表示保留的版本數量
-    description: '保留的版本數量'
+    # 參數說明，這裡表示每組（正式版／預發行版）各自保留的版本數量
+    description: '保留的版本數量（正式版與預發行版各自保留）'
     # 預設保留 2 個版本，避免完全刪除歷史 release
     default: '2'
 
diff --git a/src/index.js b/src/index.js
index a3fd6cc..2504ab8 100644
--- a/src/index.js
+++ b/src/index.js
@@ -395,7 +395,7 @@ function hasBatchFailure(results) {
 }
 
 /**
- * 執行 release 與 tag 清理流程。
+ * 執行 release 與 tag 清理流程；正式版與預發行版（prerelease）分組計算，各自保留最新 `KEEP_COUNT` 筆。
  */
 async function main() {
   const GITEA_SERVER_URL = normalizeEnvValue(process.env.GITEA_SERVER_URL);
@@ -454,16 +454,21 @@ async function main() {
     return 0;
   });
 
-  const releaseCount = releaseJson.length;
-  info(`RELEASE_COUNT=${releaseCount}`);
+  const stableReleases = releaseJson.filter((item) => !item?.prerelease);
+  const preReleases = releaseJson.filter((item) => item?.prerelease);
+
+  info(`RELEASE_COUNT=${releaseJson.length}`);
+  info(`STABLE_COUNT=${stableReleases.length}`);
+  info(`PRERELEASE_COUNT=${preReleases.length}`);
   info(`KEEP_COUNT=${KEEP_COUNT}`);
 
-  if (releaseCount <= keepCount) {
+  const releaseToKeep = [...stableReleases.slice(0, keepCount), ...preReleases.slice(0, keepCount)];
+  const releaseToDelete = [...stableReleases.slice(keepCount), ...preReleases.slice(keepCount)];
+
+  if (releaseToDelete.length === 0) {
     info('沒有需要清理的舊版本成品');
   } else {
     section('刪除舊版本成品');
-
-    const releaseToDelete = releaseJson.slice(keepCount);
     const releaseResults = await processInBatches(releaseToDelete, DELETE_CONCURRENCY, async (releaseItem) => {
       const releaseId = releaseItem?.id;
       if (!Number.isSafeInteger(releaseId) || releaseId <= 0) {
@@ -496,8 +501,7 @@ async function main() {
   section('刪除未指定 release 的 tag');
 
   const releaseTags = new Set(
-    releaseJson
-      .slice(0, keepCount)
+    releaseToKeep
       .map((item) => item?.tag_name)
       .filter((tag) => !isEmptyOrNull(tag)),
   );