fix(cliproxy): address PR review issues for backend selection

- Remove duplicate CLIProxyBackend type from platform-detector.ts (import from types.ts)
- Add warning for invalid --backend CLI value (was silently ignored)
- Show toast notification when backend change blocked by running proxy
- Migrate from deprecated CLIPROXY_FALLBACK_VERSION to getFallbackVersion()
- Add comprehensive JSDoc for backend API endpoints

src/cliproxy/platform-detector.ts

@@ -5,10 +5,13 @@
  * Supports 6 platforms: darwin/linux/windows x amd64/arm64
  */
 
-import { PlatformInfo, SupportedOS, SupportedArch, ArchiveExtension } from './types';
-
-// Phase 1 will add CLIProxyBackend type - using string literal temporarily
-type CLIProxyBackend = 'original' | 'plus';
+import {
+  PlatformInfo,
+  SupportedOS,
+  SupportedArch,
+  ArchiveExtension,
+  CLIProxyBackend,
+} from './types';
 
 /** Backend configuration */
 export const BACKEND_CONFIG = {

src/commands/cliproxy-command.ts

@@ -29,7 +29,7 @@ import {
 } from '../cliproxy/account-manager';
 import { fetchAllProviderQuotas } from '../cliproxy/quota-fetcher';
 import { isOnCooldown } from '../cliproxy/quota-manager';
-import { DEFAULT_BACKEND, CLIPROXY_FALLBACK_VERSION } from '../cliproxy/platform-detector';
+import { DEFAULT_BACKEND, getFallbackVersion, BACKEND_CONFIG } from '../cliproxy/platform-detector';
 import { CLIPROXY_PROFILES, CLIProxyProfileName } from '../auth/profile-detector';
 import { supportsModelConfig, getProviderCatalog, ModelEntry } from '../cliproxy/model-catalog';
 import { CLIProxyProvider, CLIProxyBackend } from '../cliproxy/types';
@@ -83,6 +83,7 @@ function parseBackendArg(args: string[]): {
     if (backendEqualsIdx !== -1) {
       const value = args[backendEqualsIdx].split('=')[1] as CLIProxyBackend;
       if (value !== 'original' && value !== 'plus') {
+        warn(`Invalid backend '${value}'. Valid options: original, plus`);
         return { backend: undefined, remainingArgs: args };
       }
       const remainingArgs = [...args];
@@ -93,6 +94,7 @@ function parseBackendArg(args: string[]): {
   }
   const value = args[backendIdx + 1];
   if (value !== 'original' && value !== 'plus') {
+    warn(`Invalid backend '${value}'. Valid options: original, plus`);
     return { backend: undefined, remainingArgs: args };
   }
   const remainingArgs = [...args];
@@ -642,9 +644,9 @@ async function showHelp(): Promise<void> {
   console.log(dim('  Note: CLIProxy now persists by default. Use "stop" to terminate.'));
   console.log('');
   console.log(subheader('Notes:'));
-  console.log(`  Default fallback version: ${color(CLIPROXY_FALLBACK_VERSION, 'info')}`);
+  console.log(`  Default fallback version: ${color(getFallbackVersion(), 'info')}`);
   console.log(
-    `  Releases: ${color('https://github.com/router-for-me/CLIProxyAPIPlus/releases', 'path')}`
+    `  Releases: ${color(`https://github.com/${BACKEND_CONFIG[DEFAULT_BACKEND].repo}/releases`, 'path')}`
   );
   console.log('');
 }

src/web-server/routes/proxy-routes.ts

@@ -68,6 +68,7 @@ router.put('/', async (req: Request, res: Response) => {
 
 /**
  * GET /api/cliproxy-server/backend - Get CLIProxy backend setting
+ * @returns {{ backend: 'original' | 'plus' }} Current backend configuration
  */
 router.get('/backend', async (_req: Request, res: Response) => {
   try {
@@ -81,6 +82,12 @@ router.get('/backend', async (_req: Request, res: Response) => {
 
 /**
  * PUT /api/cliproxy-server/backend - Update CLIProxy backend setting
+ * @param {Object} req.body - Request body
+ * @param {'original' | 'plus'} req.body.backend - Backend to switch to
+ * @param {boolean} [req.body.force=false] - Force change even if proxy is running
+ * @returns {{ backend: 'original' | 'plus' }} Updated backend configuration
+ * @throws {400} Invalid backend value
+ * @throws {409} Proxy is running (unless force=true)
  */
 router.put('/backend', async (req: Request, res: Response) => {
   try {

ui/src/pages/settings/sections/proxy/index.tsx

@@ -18,6 +18,7 @@ import {
   Box,
   AlertTriangle,
 } from 'lucide-react';
+import { toast } from 'sonner';
 import { useProxyConfig, useRawConfig } from '../../hooks';
 import { LocalProxyCard } from './local-proxy-card';
 import { RemoteProxyCard } from './remote-proxy-card';
@@ -110,7 +111,7 @@ export default function ProxySection() {
       const errorMessage = err instanceof Error ? err.message : 'Failed to save backend';
       // Check if error is due to proxy running (409 conflict)
       if (errorMessage.includes('Proxy is running')) {
-        console.warn('[Proxy] Backend change blocked: proxy is running');
+        toast.error('Stop the proxy first to change backend');
       }
       console.error('[Proxy] Failed to save backend:', err);
       setBackend(previousValue);