feat(cliproxy): implement --nickname flag for account management

- Add renameAccount function to account-manager.ts with validation
- Support --nickname <name> to rename current default account
- Support --nickname with --auth --add to set nickname during OAuth
- Add getDefaultAccount import for nickname operations
- Filter --nickname flag from Claude CLI args

src/cliproxy/account-manager.ts

@@ -304,6 +304,38 @@ export function removeAccount(provider: CLIProxyProvider, accountId: string): bo
   return true;
 }
 
+/**
+ * Rename an account's nickname
+ */
+export function renameAccount(
+  provider: CLIProxyProvider,
+  accountId: string,
+  newNickname: string
+): boolean {
+  const validationError = validateNickname(newNickname);
+  if (validationError) {
+    throw new Error(validationError);
+  }
+
+  const registry = loadAccountsRegistry();
+  const providerAccounts = registry.providers[provider];
+
+  if (!providerAccounts?.accounts[accountId]) {
+    return false;
+  }
+
+  // Check if nickname is already used by another account
+  for (const [id, account] of Object.entries(providerAccounts.accounts)) {
+    if (id !== accountId && account.nickname?.toLowerCase() === newNickname.toLowerCase()) {
+      throw new Error(`Nickname "${newNickname}" is already used by another account`);
+    }
+  }
+
+  providerAccounts.accounts[accountId].nickname = newNickname;
+  saveAccountsRegistry(registry);
+  return true;
+}
+
 /**
  * Update last used timestamp for an account
  */

src/cliproxy/auth-handler.ts

@@ -435,10 +435,16 @@ export function clearAuth(provider: CLIProxyProvider): boolean {
  */
 export async function triggerOAuth(
   provider: CLIProxyProvider,
-  options: { verbose?: boolean; headless?: boolean; account?: string; add?: boolean } = {}
+  options: {
+    verbose?: boolean;
+    headless?: boolean;
+    account?: string;
+    add?: boolean;
+    nickname?: string;
+  } = {}
 ): Promise<AccountInfo | null> {
   const oauthConfig = getOAuthConfig(provider);
-  const { verbose = false, add = false } = options;
+  const { verbose = false, add = false, nickname } = options;
 
   // Auto-detect headless if not explicitly set
   const headless = options.headless ?? isHeadlessEnvironment();
@@ -615,7 +621,7 @@ export async function triggerOAuth(
           console.log('[OK] Authentication successful');
 
           // Register the account in accounts registry
-          const account = registerAccountFromToken(provider, tokenDir);
+          const account = registerAccountFromToken(provider, tokenDir, nickname);
           resolve(account);
         } else {
           if (!headless) spinner.fail('Authentication incomplete');
@@ -658,10 +664,14 @@ export async function triggerOAuth(
 /**
  * Register account from newly created token file
  * Scans auth directory for new token and extracts email
+ * @param provider - The CLIProxy provider
+ * @param tokenDir - Directory containing token files
+ * @param nickname - Optional nickname (uses auto-generated from email if not provided)
  */
 function registerAccountFromToken(
   provider: CLIProxyProvider,
-  tokenDir: string
+  tokenDir: string,
+  nickname?: string
 ): AccountInfo | null {
   try {
     const files = fs.readdirSync(tokenDir);
@@ -692,8 +702,8 @@ function registerAccountFromToken(
     const data = JSON.parse(content);
     const email = data.email || undefined;
 
-    // Register the account with auto-generated nickname
-    return registerAccount(provider, newestFile, email, generateNickname(email));
+    // Register the account (use provided nickname or auto-generate from email)
+    return registerAccount(provider, newestFile, email, nickname || generateNickname(email));
   } catch {
     return null;
   }

src/cliproxy/cliproxy-executor.ts

@@ -33,6 +33,8 @@ import {
   getProviderAccounts,
   setDefaultAccount,
   touchAccount,
+  renameAccount,
+  getDefaultAccount,
 } from './account-manager';
 
 /** Default executor configuration */
@@ -139,6 +141,13 @@ export async function execClaudeWithCLIProxy(
     useAccount = args[useIdx + 1];
   }
 
+  // Parse --nickname <name> flag
+  let setNickname: string | undefined;
+  const nicknameIdx = args.indexOf('--nickname');
+  if (nicknameIdx !== -1 && args[nicknameIdx + 1] && !args[nicknameIdx + 1].startsWith('-')) {
+    setNickname = args[nicknameIdx + 1];
+  }
+
   // Handle --accounts: list accounts and exit
   if (showAccounts) {
     const accounts = getProviderAccounts(provider);
@@ -177,6 +186,29 @@ export async function execClaudeWithCLIProxy(
     console.log(`[OK] Switched to account: ${account.nickname || account.email || account.id}`);
   }
 
+  // Handle --nickname: rename account and exit (unless used with --auth --add)
+  if (setNickname && !addAccount) {
+    const defaultAccount = getDefaultAccount(provider);
+    if (!defaultAccount) {
+      console.error(`[X] No account found for ${providerConfig.displayName}`);
+      console.error(`    Run "ccs ${provider} --auth" to add an account first`);
+      process.exit(1);
+    }
+    try {
+      const success = renameAccount(provider, defaultAccount.id, setNickname);
+      if (success) {
+        console.log(`[OK] Renamed account to: ${setNickname}`);
+      } else {
+        console.error(`[X] Failed to rename account`);
+        process.exit(1);
+      }
+    } catch (err) {
+      console.error(`[X] ${err instanceof Error ? err.message : 'Failed to rename account'}`);
+      process.exit(1);
+    }
+    process.exit(0);
+  }
+
   // Handle --config: configure model selection and exit
   // Pass customSettingsPath for CLIProxy variants to save to correct file
   if (forceConfig && supportsModelConfig(provider)) {
@@ -206,6 +238,7 @@ export async function execClaudeWithCLIProxy(
         verbose,
         add: addAccount,
         ...(forceHeadless ? { headless: true } : {}),
+        ...(setNickname ? { nickname: setNickname } : {}),
       });
       if (!authSuccess) {
         throw new Error(`Authentication required for ${providerConfig.displayName}`);
@@ -314,12 +347,21 @@ export async function execClaudeWithCLIProxy(
   log(`Claude env: ANTHROPIC_MODEL=${envVars.ANTHROPIC_MODEL}`);
 
   // Filter out CCS-specific flags before passing to Claude CLI
-  const ccsFlags = ['--auth', '--headless', '--logout', '--config', '--add', '--accounts', '--use'];
+  const ccsFlags = [
+    '--auth',
+    '--headless',
+    '--logout',
+    '--config',
+    '--add',
+    '--accounts',
+    '--use',
+    '--nickname',
+  ];
   const claudeArgs = args.filter((arg, idx) => {
     // Filter out CCS flags
     if (ccsFlags.includes(arg)) return false;
-    // Filter out value after --use
-    if (args[idx - 1] === '--use') return false;
+    // Filter out value after --use or --nickname
+    if (args[idx - 1] === '--use' || args[idx - 1] === '--nickname') return false;
     return true;
   });