diff --git a/OpenBitFun-Installer/AGENTS-CN.md b/OpenBitFun-Installer/AGENTS-CN.md
index e096c75d23..6be918588c 100644
--- a/OpenBitFun-Installer/AGENTS-CN.md
+++ b/OpenBitFun-Installer/AGENTS-CN.md
@@ -26,6 +26,8 @@
 Language Select → Options → Progress → Model Setup → Theme Setup
 ```
 
+如果所选路径已有 OpenBitFun 安装，流程会在 `Progress` 后结束，保留已有的模型和主题配置。
+
 ## 命令
 
 这些是命令参考，不是默认预检清单。PR 范围请以下方 Verification 为准。
diff --git a/OpenBitFun-Installer/AGENTS.md b/OpenBitFun-Installer/AGENTS.md
index 336bcd60b2..10f1e5bff5 100644
--- a/OpenBitFun-Installer/AGENTS.md
+++ b/OpenBitFun-Installer/AGENTS.md
@@ -26,6 +26,9 @@ Install flow:
 Language Select → Options → Progress → Model Setup → Theme Setup
 ```
 
+For an existing installation at the selected path, the flow ends after
+`Progress`; model and theme setup are retained from the existing installation.
+
 ## Commands
 
 These are command references, not the default precheck list. Use Verification
diff --git a/OpenBitFun-Installer/README.md b/OpenBitFun-Installer/README.md
index bed1129cf5..e33607a651 100644
--- a/OpenBitFun-Installer/README.md
+++ b/OpenBitFun-Installer/README.md
@@ -114,6 +114,11 @@ Language Select → Options → Progress → Model Setup → Theme Setup
     language      options    install      model config    launch/close
 ```
 
+When the selected installation path already contains the current OpenBitFun
+installation, the update flow ends after Progress. The existing model and theme
+configuration are preserved, and the installer launches the updated application
+when launch-after-install is enabled.
+
 ## Development
 
 ### Prerequisites
diff --git a/OpenBitFun-Installer/src/hooks/useInstaller.ts b/OpenBitFun-Installer/src/hooks/useInstaller.ts
index aa52b6a45f..ab50d6b1db 100644
--- a/OpenBitFun-Installer/src/hooks/useInstaller.ts
+++ b/OpenBitFun-Installer/src/hooks/useInstaller.ts
@@ -52,6 +52,23 @@ export interface UseInstallerReturn {
 
 const STEPS: InstallStep[] = ['lang', 'options', 'progress', 'model', 'theme'];
 
+function normalizeInstallPath(path: string): string {
+  return path.trim().replace(/[\\/]+$/, '');
+}
+
+function isSameInstallPath(left: string, right: string): boolean {
+  const normalizedLeft = normalizeInstallPath(left);
+  const normalizedRight = normalizeInstallPath(right);
+  if (normalizedLeft === normalizedRight) return true;
+
+  // Windows registry paths are case-insensitive. Keep POSIX paths case-sensitive.
+  const isWindowsPath = /^[A-Za-z]:[\\/]/.test(normalizedLeft)
+    || /^[A-Za-z]:[\\/]/.test(normalizedRight)
+    || normalizedLeft.includes('\\')
+    || normalizedRight.includes('\\');
+  return isWindowsPath && normalizedLeft.toLowerCase() === normalizedRight.toLowerCase();
+}
+
 export function useInstaller(): UseInstallerReturn {
   const [previewOnly, setPreviewOnly] = useState(false);
   const [step, setStep] = useState<InstallStep>('lang');
@@ -243,9 +260,16 @@ export function useInstaller(): UseInstallerReturn {
     setInstallationCompleted(false);
     setCanConfirmProgress(false);
     try {
+      const detectedInstall = await refreshExistingInstall();
       const validated = await invoke<InstallPathValidation>('validate_install_path', {
         path: options.installPath,
       });
+      const isUpdate = Boolean(
+        detectedInstall.detected
+        && detectedInstall.mainBinaryPresent
+        && detectedInstall.installLocation
+        && isSameInstallPath(detectedInstall.installLocation, validated.installPath),
+      );
       const effectiveOptions = {
         ...options,
         installPath: validated.installPath,
@@ -257,6 +281,13 @@ export function useInstaller(): UseInstallerReturn {
       setProgress({ step: 'prepare', percent: 0, message: '' });
       await invoke('start_installation', { options: effectiveOptions });
       setInstallationCompleted(true);
+      if (isUpdate) {
+        if (options.launchAfterInstall) {
+          await invoke('launch_application', { installPath: effectiveOptions.installPath });
+        }
+        await invoke('close_installer');
+        return;
+      }
       setStep('model');
       try {
         const info = await readExistingInstall();
@@ -270,7 +301,7 @@ export function useInstaller(): UseInstallerReturn {
     } finally {
       setIsInstalling(false);
     }
-  }, [options, readExistingInstall]);
+  }, [options, readExistingInstall, refreshExistingInstall]);
 
   const confirmProgress = useCallback(() => {
     if (!canConfirmProgress) return;