diff --git a/core/updater.py b/core/updater.py
index 3b075b6..ef9d0f7 100644
--- a/core/updater.py
+++ b/core/updater.py
@@ -268,19 +268,23 @@ class UpdateChecker:
             bat_path = os.path.join(tmp_dir, "sm_update.bat")
             log_path = os.path.join(tmp_dir, "sm_update.log")
             pid = os.getpid()
+            new_size = os.path.getsize(new_exe)
 
             bat_content = f"""@echo off
+setlocal enabledelayedexpansion
 chcp 65001 >nul 2>&1
 set "LOGFILE={log_path}"
 set "SRC={new_exe}"
 set "DST={current_exe}"
 set "PID={pid}"
 set "TMPDIR={tmp_dir}"
+set "EXPECTED_SIZE={new_size}"
 
 echo [%date% %time%] Update script started >> "%LOGFILE%"
 echo [%date% %time%] PID to wait for: %PID% >> "%LOGFILE%"
 echo [%date% %time%] SRC: %SRC% >> "%LOGFILE%"
 echo [%date% %time%] DST: %DST% >> "%LOGFILE%"
+echo [%date% %time%] Expected size: %EXPECTED_SIZE% >> "%LOGFILE%"
 
 :wait_loop
 tasklist /FI "PID eq %PID%" 2>nul | find "%PID%" >nul
@@ -300,17 +304,39 @@ for /d %%D in ("%TMPDIR%\\_MEI*") do (
 )
 timeout /t 1 /nobreak >nul
 
-rem Copy with retry
+rem Log source file size
+for %%F in ("%SRC%") do (
+    echo [%date% %time%] SRC file size: %%~zF >> "%LOGFILE%"
+)
+
+rem Delete old DST first so copy is clean
+echo [%date% %time%] Deleting old DST... >> "%LOGFILE%"
+del /f /q "%DST%" >nul 2>&1
+if exist "%DST%" (
+    echo [%date% %time%] WARNING: could not delete old DST >> "%LOGFILE%"
+)
+timeout /t 1 /nobreak >nul
+
+rem Copy with retry and size verification
 echo [%date% %time%] Starting copy... >> "%LOGFILE%"
 set COPIED=0
 for /L %%i in (1,1,5) do (
     if !COPIED!==0 (
-        copy /Y "%SRC%" "%DST%" >nul 2>&1
+        echo [%date% %time%] Copy attempt %%i... >> "%LOGFILE%"
+        copy /Y /B "%SRC%" "%DST%" >> "%LOGFILE%" 2>&1
         if exist "%DST%" (
-            echo [%date% %time%] Copy attempt %%i done >> "%LOGFILE%"
-            set COPIED=1
+            for %%F in ("%DST%") do set DST_SIZE=%%~zF
+            echo [%date% %time%] DST size after copy: !DST_SIZE! >> "%LOGFILE%"
+            if "!DST_SIZE!"=="%EXPECTED_SIZE%" (
+                echo [%date% %time%] Size verified OK >> "%LOGFILE%"
+                set COPIED=1
+            ) else (
+                echo [%date% %time%] Size mismatch! Expected %EXPECTED_SIZE%, got !DST_SIZE! >> "%LOGFILE%"
+                del /f /q "%DST%" >nul 2>&1
+                timeout /t 2 /nobreak >nul
+            )
         ) else (
-            echo [%date% %time%] Copy attempt %%i failed >> "%LOGFILE%"
+            echo [%date% %time%] Copy failed - DST does not exist >> "%LOGFILE%"
             timeout /t 2 /nobreak >nul
         )
     )
@@ -340,16 +366,12 @@ echo [%date% %time%] Cleanup done >> "%LOGFILE%"
 rem Self-delete
 del /f /q "%~f0" >nul 2>&1
 """
-            # Enable delayed expansion for variables inside for loops
-            bat_content = bat_content.replace("@echo off",
-                                             "@echo off\nsetlocal enabledelayedexpansion")
-
             with open(bat_path, "w", encoding="utf-8") as f:
                 f.write(bat_content)
 
             log.info(f"Update BAT: {bat_path}, log: {log_path}")
 
-            # Launch BAT minimized (not hidden — need cmd.exe to run)
+            # Launch BAT minimized
             subprocess.Popen(
                 ["cmd.exe", "/c", "start", "/min", "", bat_path],
                 creationflags=_SUBPROCESS_FLAGS,
diff --git a/releases/ServerManager-v1.8.99-win-x64.exe b/releases/ServerManager-v1.8.99-win-x64.exe
new file mode 100644
index 0000000..10993c9
Binary files /dev/null and b/releases/ServerManager-v1.8.99-win-x64.exe differ
diff --git a/version.py b/version.py
index 7be74a6..186af30 100755
--- a/version.py
+++ b/version.py
@@ -1,6 +1,6 @@
 """Version info for ServerManager."""
 
-__version__ = "1.8.98"
+__version__ = "1.8.99"
 __app_name__ = "ServerManager"
 __author__ = "aibot777"
 __description__ = "Desktop GUI for managing remote servers"