diff --git a/src-tauri/src/commands/registry.rs b/src-tauri/src/commands/registry.rs
index 29bffa8..f062007 100644
--- a/src-tauri/src/commands/registry.rs
+++ b/src-tauri/src/commands/registry.rs
@@ -63,6 +63,8 @@ pub fn save_user_paths(paths: Vec<String>) -> Result<(), String> {
     save_paths(HKEY_CURRENT_USER, USER_REG_PATH, "用户", &paths)
 }
 
+/// 将分号分隔的 PATH 字符串拆分为数组。
+/// 注意：TS 端 src/core/validation.ts 有相同逻辑的 split_path，修改时需同步两端。
 pub(crate) fn split_path(raw: &str) -> Vec<String> {
     raw.split(';')
         .map(|s| s.trim().to_string())
diff --git a/src-tauri/src/error.rs b/src-tauri/src/error.rs
deleted file mode 100644
index 97ca0e5..0000000
--- a/src-tauri/src/error.rs
+++ /dev/null
@@ -1,36 +0,0 @@
-use serde::Serialize;
-
-/// 传给前端的统一错误类型（保留供未来迁移使用，届时所有命令改为返回 Result<T, AppError>）
-#[allow(dead_code)]
-#[derive(Debug, Serialize)]
-pub struct AppError {
-    pub message: String,
-}
-
-impl std::fmt::Display for AppError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.message)
-    }
-}
-
-impl From<&str> for AppError {
-    fn from(s: &str) -> Self {
-        AppError {
-            message: s.to_string(),
-        }
-    }
-}
-
-impl From<String> for AppError {
-    fn from(s: String) -> Self {
-        AppError { message: s }
-    }
-}
-
-impl From<std::io::Error> for AppError {
-    fn from(e: std::io::Error) -> Self {
-        AppError {
-            message: format!("IO 错误: {}", e),
-        }
-    }
-}
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index fe116f4..a5294ee 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -1,5 +1,4 @@
 mod commands;
-mod error;
 
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
diff --git a/src/config/default.json b/src/config/default.json
index e5775a1..4f078d9 100644
--- a/src/config/default.json
+++ b/src/config/default.json
@@ -12,8 +12,8 @@
     "dir": ""
   },
   "path": {
-    "maxSystemLength": 2048,
-    "maxUserLength": 2048,
-    "maxCombinedLength": 8191
+    "maxSystemLength": 32767,
+    "maxUserLength": 32767,
+    "maxCombinedLength": 32767
   }
 }
diff --git a/src/core/import-export.ts b/src/core/import-export.ts
index 3cbf1e0..ba62c13 100644
--- a/src/core/import-export.ts
+++ b/src/core/import-export.ts
@@ -2,7 +2,7 @@
  * 导入导出模块 — 对应 C 版 import_export.c
  * 支持 JSON、CSV、TXT 三种格式
  */
-export type ExportFormat = 'json' | 'csv';
+export type ExportFormat = 'json' | 'csv' | 'txt';
 
 export interface ExportData {
   system: string[];
@@ -11,7 +11,9 @@ export interface ExportData {
 
 /** 根据文件扩展名检测格式 */
 export function detectExportFormat(filepath: string): ExportFormat {
-  if (filepath.toLowerCase().endsWith('.csv')) return 'csv';
+  const lower = filepath.toLowerCase();
+  if (lower.endsWith('.csv')) return 'csv';
+  if (lower.endsWith('.txt')) return 'txt';
   return 'json';
 }
 
@@ -65,10 +67,10 @@ export function importFromCsv(content: string): ImportResult {
 
   let hasHeader = false;
 
-  for (const rawLine of lines) {
-    // 跳过 BOM
-    let line = rawLine;
-    if (line.startsWith('')) {
+  for (let i = 0; i < lines.length; i++) {
+    // 跳过 BOM（仅首行）
+    let line = lines[i];
+    if (i === 0 && line.startsWith('')) {
       line = line.slice(1);
     }
 
@@ -174,9 +176,10 @@ export function importFromTxt(content: string): string[] {
   const paths: string[] = [];
   const lines = content.split(/\r?\n/);
 
-  for (let line of lines) {
-    // 跳过 BOM
-    if (line.startsWith('')) line = line.slice(1);
+  for (let i = 0; i < lines.length; i++) {
+    // 跳过 BOM（仅首行）
+    let line = lines[i];
+    if (i === 0 && line.startsWith('')) line = line.slice(1);
 
     const trimmed = line.trim();
     if (trimmed.length === 0 || trimmed.startsWith('#')) continue;
diff --git a/src/core/validation.ts b/src/core/validation.ts
index b10743b..80a030d 100644
--- a/src/core/validation.ts
+++ b/src/core/validation.ts
@@ -26,7 +26,8 @@ export function join_path(paths: string[]): string {
   return paths.join(';');
 }
 
-/** 分割 PATH 字符串 */
+/** 分割 PATH 字符串。
+ *  注意：Rust 端 src-tauri/src/commands/registry.rs 有相同逻辑的 split_path，修改时需同步两端。 */
 export function split_path(raw: string): string[] {
   return raw
     .split(';')
diff --git a/src/hooks/use-app-actions.ts b/src/hooks/use-app-actions.ts
index b42c820..1541912 100644
--- a/src/hooks/use-app-actions.ts
+++ b/src/hooks/use-app-actions.ts
@@ -92,9 +92,9 @@ export function useAppActions(activeTab: TabId, dialogs: DialogState) {
     if (result.system.length > 0 && result.user.length > 0) {
       setImportDialog({ open: true, system: result.system, user: result.user });
     } else if (result.system.length > 0) {
-      useAppStore.getState().importPaths(TargetType.SYSTEM, result.system);
+      useAppStore.getState().replacePaths(TargetType.SYSTEM, result.system);
     } else if (result.user.length > 0) {
-      useAppStore.getState().importPaths(TargetType.USER, result.user);
+      useAppStore.getState().replacePaths(TargetType.USER, result.user);
     }
   }, [setImportDialog]);
 
@@ -159,8 +159,8 @@ export function useAppActions(activeTab: TabId, dialogs: DialogState) {
   const handleImportSelect = useCallback((target: 'system' | 'user' | 'both') => {
     const { system, user } = dialogs.importDialog;
     const flat = flattenImportResult({ system, user }, target);
-    if (flat.system.length > 0) useAppStore.getState().importPaths(TargetType.SYSTEM, flat.system);
-    if (flat.user.length > 0) useAppStore.getState().importPaths(TargetType.USER, flat.user);
+    if (flat.system.length > 0) useAppStore.getState().replacePaths(TargetType.SYSTEM, flat.system);
+    if (flat.user.length > 0) useAppStore.getState().replacePaths(TargetType.USER, flat.user);
     setImportDialog({ open: false, system: [], user: [] });
   }, [dialogs.importDialog, setImportDialog]);
 
diff --git a/src/store/app-store.ts b/src/store/app-store.ts
index 3ce9de2..509b4f6 100644
--- a/src/store/app-store.ts
+++ b/src/store/app-store.ts
@@ -34,7 +34,7 @@ interface AppState {
   moveUp: (index: number, target: TargetType) => void;
   moveDown: (index: number, target: TargetType) => void;
   cleanPaths: (target: TargetType, validateFn: (p: string) => boolean) => string[];
-  importPaths: (target: TargetType, importPaths: string[]) => void;
+  replacePaths: (target: TargetType, newPaths: string[]) => void;
   clearPaths: (target: TargetType) => void;
 
   undo: () => void;
@@ -169,18 +169,18 @@ export const useAppStore = create<AppState>((set, get) => ({
     return removed;
   },
 
-  importPaths: (target, importPaths) => {
-    if (importPaths.length === 0) return;
+  replacePaths: (target, newPaths) => {
+    if (newPaths.length === 0) return;
     const state = get();
     const list = target === TargetType.SYSTEM ? state.sysPaths : state.userPaths;
 
     state.undoRedo.push({
-      type: OperationType.IMPORT, target, index: 0, count: importPaths.length,
-      oldPaths: [...list], newPaths: [...importPaths],
+      type: OperationType.IMPORT, target, index: 0, count: newPaths.length,
+      oldPaths: [...list], newPaths: [...newPaths],
     });
 
-    if (target === TargetType.SYSTEM) set({ sysPaths: [...importPaths], selectedIndices: [] });
-    else set({ userPaths: [...importPaths], selectedIndices: [] });
+    if (target === TargetType.SYSTEM) set({ sysPaths: [...newPaths], selectedIndices: [] });
+    else set({ userPaths: [...newPaths], selectedIndices: [] });
     get()._markDirty();
   },
 
diff --git a/tests/unit/app-store.test.ts b/tests/unit/app-store.test.ts
index de73fea..c2243f2 100644
--- a/tests/unit/app-store.test.ts
+++ b/tests/unit/app-store.test.ts
@@ -140,11 +140,11 @@ describe('app-store CRUD', () => {
     expect(useAppStore.getState().sysPaths).toEqual(['C:\\valid']);
   });
 
-  it('importPaths 整体替换列表', () => {
+  it('replacePaths 整体替换列表', () => {
     const store = useAppStore.getState();
     store.addPath('old1', TargetType.USER);
     store.addPath('old2', TargetType.USER);
-    store.importPaths(TargetType.USER, ['new1', 'new2', 'new3']);
+    store.replacePaths(TargetType.USER, ['new1', 'new2', 'new3']);
     expect(useAppStore.getState().userPaths).toEqual(['new1', 'new2', 'new3']);
   });
 
diff --git a/tests/unit/import-export.test.ts b/tests/unit/import-export.test.ts
index b49a2d6..5c957cf 100644
--- a/tests/unit/import-export.test.ts
+++ b/tests/unit/import-export.test.ts
@@ -116,10 +116,11 @@ describe('detectExportFormat', () => {
   it('.csv 检测为 CSV', () => {
     expect(detectExportFormat('data.CSV')).toBe('csv');
   });
-
+  it('.txt 检测为 TXT', () => {
+    expect(detectExportFormat('data.txt')).toBe('txt');
+  });
   it('其他扩展名检测为 JSON', () => {
     expect(detectExportFormat('data.json')).toBe('json');
-    expect(detectExportFormat('data.txt')).toBe('json');
   });
 });