diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index bbe625d..e402f8b 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -16,8 +16,8 @@ android {
         applicationId = "com.rainy.token"
         minSdk = 31
         targetSdk = 35
-        versionCode = 20
-        versionName = "1.7.0"
+        versionCode = 21
+        versionName = "1.7.1"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
         vectorDrawables {
diff --git a/app/src/main/java/com/rainy/token/data/repository/UpdateRepository.kt b/app/src/main/java/com/rainy/token/data/repository/UpdateRepository.kt
index 32b8151..921f23c 100644
--- a/app/src/main/java/com/rainy/token/data/repository/UpdateRepository.kt
+++ b/app/src/main/java/com/rainy/token/data/repository/UpdateRepository.kt
@@ -56,7 +56,7 @@ class UpdateRepository @Inject constructor(
         }
     }
 
-    /** 下载 APK 到缓存目录。onProgress 回调下载字节数/总字节数（total 可能为 -1）。 */
+    /** 下载 APK 到缓存目录；同版本已下载完成时直接复用，不重复下载。 */
     suspend fun downloadApk(
         info: UpdateInfo,
         onProgress: (downloaded: Long, total: Long) -> Unit
@@ -64,6 +64,11 @@ class UpdateRepository @Inject constructor(
         try {
             val dir = File(appContext.cacheDir, "apk_downloads").apply { mkdirs() }
             val file = File(dir, "rainytoken-" + info.versionName + ".apk")
+            if (file.exists() && file.length() > 0L) {
+                return@withContext Result.success(file)
+            }
+            // 先写 .part，下载完整后再替换正式文件名，避免半截文件被当成完整包
+            val part = File(dir, file.name + ".part")
             val request = Request.Builder().url(info.apkUrl).get().build()
             okHttpClient.newCall(request).execute().use { resp ->
                 if (!resp.isSuccessful) {
@@ -71,7 +76,7 @@ class UpdateRepository @Inject constructor(
                 }
                 val body = resp.body ?: return@withContext Result.failure(IOException("empty body"))
                 val total = body.contentLength()
-                file.outputStream().buffered().use { output ->
+                part.outputStream().buffered().use { output ->
                     body.byteStream().use { input ->
                         val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
                         var downloaded = 0L
@@ -84,6 +89,8 @@ class UpdateRepository @Inject constructor(
                     }
                 }
             }
+            if (file.exists()) file.delete()
+            part.renameTo(file)
             Result.success(file)
         } catch (e: Exception) {
             Result.failure(e)
diff --git a/app/src/main/java/com/rainy/token/ui/settings/SettingsScreen.kt b/app/src/main/java/com/rainy/token/ui/settings/SettingsScreen.kt
index 6344a8a..6b25d18 100644
--- a/app/src/main/java/com/rainy/token/ui/settings/SettingsScreen.kt
+++ b/app/src/main/java/com/rainy/token/ui/settings/SettingsScreen.kt
@@ -508,9 +508,23 @@ private fun UpdateCard(
                         style = MaterialTheme.typography.bodyMedium,
                         color = InkMuted
                     )
+                    if (phase.error != null) {
+                        Spacer(modifier = Modifier.padding(top = 4.dp))
+                        Text(
+                            text = phase.error,
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.error
+                        )
+                    }
                     Spacer(modifier = Modifier.padding(top = 8.dp))
                     Button(onClick = { viewModel.install(phase.file) }) {
-                        Text(stringResource(R.string.update_install))
+                        Text(
+                            if (phase.error == null) {
+                                stringResource(R.string.update_install)
+                            } else {
+                                "重试安装"
+                            }
+                        )
                     }
                 }
                 is UpdateViewModel.Phase.NeedInstallPermission -> {
@@ -529,6 +543,9 @@ private fun UpdateCard(
                     }) {
                         Text(stringResource(R.string.update_enable_permission))
                     }
+                    TextButton(onClick = { viewModel.install(phase.file) }) {
+                        Text("已开启，继续安装")
+                    }
                 }
                 is UpdateViewModel.Phase.Error -> {
                     Text(
diff --git a/app/src/main/java/com/rainy/token/ui/settings/UpdateViewModel.kt b/app/src/main/java/com/rainy/token/ui/settings/UpdateViewModel.kt
index 3fc9456..6b56e0e 100644
--- a/app/src/main/java/com/rainy/token/ui/settings/UpdateViewModel.kt
+++ b/app/src/main/java/com/rainy/token/ui/settings/UpdateViewModel.kt
@@ -30,8 +30,8 @@ class UpdateViewModel @Inject constructor(
         object Latest : Phase
         data class Available(val info: UpdateRepository.UpdateInfo) : Phase
         data class Downloading(val progress: Float) : Phase
-        data class Ready(val file: File) : Phase
-        object NeedInstallPermission : Phase
+        data class Ready(val file: File, val error: String? = null) : Phase
+        data class NeedInstallPermission(val file: File) : Phase
         data class Error(val message: String) : Phase
     }
 
@@ -83,7 +83,7 @@ class UpdateViewModel @Inject constructor(
         val canInstall = runCatching { context.packageManager.canRequestPackageInstalls() }
             .getOrDefault(false)
         if (!canInstall) {
-            _uiState.update { it.copy(phase = Phase.NeedInstallPermission) }
+            _uiState.update { it.copy(phase = Phase.NeedInstallPermission(file)) }
             return
         }
         _uiState.update { it.copy(phase = Phase.Ready(file)) }
@@ -91,7 +91,7 @@ class UpdateViewModel @Inject constructor(
         val uri = try {
             FileProvider.getUriForFile(context, authority, file)
         } catch (e: Exception) {
-            _uiState.update { it.copy(phase = Phase.Error("安装文件无效：" + (e.message ?: "未知错误"))) }
+            _uiState.update { it.copy(phase = Phase.Ready(file, "安装文件无效：" + (e.message ?: "未知错误"))) }
             return
         }
         val actionView = Intent(Intent.ACTION_VIEW).apply {
@@ -105,7 +105,7 @@ class UpdateViewModel @Inject constructor(
                 addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION or Intent.FLAG_ACTIVITY_NEW_TASK)
             }
             runCatching { context.startActivity(actionInstall) }.onFailure { e ->
-                _uiState.update { it.copy(phase = Phase.Error(e.message ?: "无法启动安装器")) }
+                _uiState.update { it.copy(phase = Phase.Ready(file, "无法启动安装器：" + (e.message ?: "未知错误"))) }
             }
         }
     }