diff --git a/src/main/services/BackupManager.ts b/src/main/services/BackupManager.ts
index c6d3ee1841..84a4815e58 100644
--- a/src/main/services/BackupManager.ts
+++ b/src/main/services/BackupManager.ts
@@ -617,13 +617,8 @@ class BackupManager {
   }
 
   async backupToS3(_: Electron.IpcMainInvokeEvent, data: string, s3Config: S3Config) {
-    const os = require('os')
-    const deviceName = os.hostname ? os.hostname() : 'device'
-    const timestamp = new Date()
-      .toISOString()
-      .replace(/[-:T.Z]/g, '')
-      .slice(0, 14)
-    const filename = s3Config.fileName || `cherry-studio.backup.${deviceName}.${timestamp}.zip`
+    // Use the filename provided by frontend, or a simple default (no timestamp generation here)
+    const filename = s3Config.fileName || 'cherry-studio.backup.zip'
 
     logger.debug(`Starting S3 backup to ${filename}`)
 
diff --git a/src/renderer/src/services/BackupService.ts b/src/renderer/src/services/BackupService.ts
index c78e0ef28b..57559df763 100644
--- a/src/renderer/src/services/BackupService.ts
+++ b/src/renderer/src/services/BackupService.ts
@@ -197,10 +197,15 @@ export async function backupToWebdav({
   let finalFileName: string
 
   // 覆盖式单文件备份（仅在自动备份流程且保留份数=1时生效）
+  logger.debug(
+    `[WebDAV Backup] Overwrite check: autoBackupProcess=${autoBackupProcess}, maxBackups=${webdavMaxBackups}, singleFileOverwrite=${webdavSingleFileOverwrite}`
+  )
   if (autoBackupProcess && webdavMaxBackups === 1 && webdavSingleFileOverwrite) {
     finalFileName = generateOverwriteFilename(webdavSingleFileName, hostname, deviceType)
+    logger.debug(`[WebDAV Backup] Using overwrite filename: ${finalFileName}`)
   } else {
     finalFileName = generateTimestampedFilename(customFileName, hostname, deviceType, timestamp)
+    logger.debug(`[WebDAV Backup] Using timestamped filename: ${finalFileName}`)
   }
   const backupData = await getBackupData()
 
@@ -377,10 +382,15 @@ export async function backupToS3({
   let finalFileName: string
 
   // 覆盖式单文件备份（仅在自动备份流程且保留份数=1时生效）
+  logger.debug(
+    `[S3 Backup] Overwrite check: autoBackupProcess=${autoBackupProcess}, maxBackups=${s3Config.maxBackups}, singleFileOverwrite=${s3Config.singleFileOverwrite}`
+  )
   if (autoBackupProcess && s3Config.maxBackups === 1 && s3Config.singleFileOverwrite) {
     finalFileName = generateOverwriteFilename(s3Config.singleFileName, hostname, deviceType)
+    logger.debug(`[S3 Backup] Using overwrite filename: ${finalFileName}`)
   } else {
     finalFileName = generateTimestampedFilename(customFileName, hostname, deviceType, timestamp)
+    logger.debug(`[S3 Backup] Using timestamped filename: ${finalFileName}`)
   }
   const backupData = await getBackupData()
 
@@ -987,10 +997,15 @@ export async function backupToLocal({
   let finalFileName: string
 
   // 覆盖式单文件备份（仅在自动备份流程且保留份数=1时生效）
+  logger.debug(
+    `[Local Backup] Overwrite check: autoBackupProcess=${autoBackupProcess}, maxBackups=${localBackupMaxBackups}, singleFileOverwrite=${localSingleFileOverwrite}`
+  )
   if (autoBackupProcess && localBackupMaxBackups === 1 && localSingleFileOverwrite) {
     finalFileName = generateOverwriteFilename(localSingleFileName, hostname, deviceType)
+    logger.debug(`[Local Backup] Using overwrite filename: ${finalFileName}`)
   } else {
     finalFileName = generateTimestampedFilename(customFileName, hostname, deviceType, timestamp)
+    logger.debug(`[Local Backup] Using timestamped filename: ${finalFileName}`)
   }
   const backupData = await getBackupData()