diff --git a/src/cliproxy/config-generator.ts b/src/cliproxy/config-generator.ts
index 9cf354d6..d0ca4b95 100644
--- a/src/cliproxy/config-generator.ts
+++ b/src/cliproxy/config-generator.ts
@@ -490,9 +490,13 @@ export function ensureProviderSettings(provider: CLIProxyProvider): void {
  */
 export function getRemoteEnvVars(
   provider: CLIProxyProvider,
-  remoteConfig: { host: string; port: number; protocol: 'http' | 'https'; authToken?: string }
+  remoteConfig: { host: string; port?: number; protocol: 'http' | 'https'; authToken?: string }
 ): Record<string, string> {
-  const baseUrl = `${remoteConfig.protocol}://${remoteConfig.host}:${remoteConfig.port}/api/provider/${provider}`;
+  // Build URL with smart port handling - omit if using protocol default
+  const defaultPort = remoteConfig.protocol === 'https' ? 443 : 80;
+  const effectivePort = remoteConfig.port ?? defaultPort;
+  const portSuffix = effectivePort === defaultPort ? '' : `:${effectivePort}`;
+  const baseUrl = `${remoteConfig.protocol}://${remoteConfig.host}${portSuffix}/api/provider/${provider}`;
   const models = getModelMapping(provider);
 
   // Get global env vars (DISABLE_TELEMETRY, etc.)
diff --git a/src/cliproxy/remote-proxy-client.ts b/src/cliproxy/remote-proxy-client.ts
index c4c8a321..047ea356 100644
--- a/src/cliproxy/remote-proxy-client.ts
+++ b/src/cliproxy/remote-proxy-client.ts
@@ -26,8 +26,13 @@ export interface RemoteProxyStatus {
 export interface RemoteProxyClientConfig {
   /** Remote proxy host (IP or hostname) */
   host: string;
-  /** Remote proxy port */
-  port: number;
+  /**
+   * Remote proxy port.
+   * Optional - defaults based on protocol:
+   * - HTTPS: 443
+   * - HTTP: 80
+   */
+  port?: number;
   /** Protocol to use (http or https) */
   protocol: 'http' | 'https';
   /** Optional auth token for Authorization header */
@@ -41,12 +46,45 @@ export interface RemoteProxyClientConfig {
 /** Default timeout for remote proxy requests (aggressive for CLI UX) */
 const DEFAULT_TIMEOUT_MS = 2000;
 
+/**
+ * Get default port for protocol
+ */
+function getDefaultPort(protocol: 'http' | 'https'): number {
+  return protocol === 'https' ? 443 : 80;
+}
+
+/**
+ * Build URL for remote proxy, intelligently omitting default ports
+ */
+function buildProxyUrl(
+  host: string,
+  port: number | undefined,
+  protocol: 'http' | 'https',
+  path: string
+): string {
+  const defaultPort = getDefaultPort(protocol);
+  const effectivePort = port ?? defaultPort;
+
+  // Omit port from URL if it matches the default for the protocol
+  if (effectivePort === defaultPort) {
+    return `${protocol}://${host}${path}`;
+  }
+  return `${protocol}://${host}:${effectivePort}${path}`;
+}
+
 /**
  * Map error to RemoteProxyErrorCode
+ *
+ * Handles various error types including:
+ * - NodeJS.ErrnoException (ECONNREFUSED, ETIMEDOUT)
+ * - Fetch errors (AbortError, TypeError)
+ * - HTTP status codes (401, 403)
  */
 function mapErrorToCode(error: Error, statusCode?: number): RemoteProxyErrorCode {
   const message = error.message.toLowerCase();
-  const code = (error as NodeJS.ErrnoException).code?.toLowerCase();
+  // Handle error.code safely - it may be string, number, or undefined
+  const rawCode = (error as NodeJS.ErrnoException).code;
+  const code = typeof rawCode === 'string' ? rawCode.toLowerCase() : undefined;
 
   // Connection refused
   if (code === 'econnrefused' || message.includes('connection refused')) {
@@ -110,7 +148,17 @@ export async function checkRemoteProxy(
   const { host, port, protocol, authToken, allowSelfSigned = false } = config;
   const timeout = config.timeout ?? DEFAULT_TIMEOUT_MS;
 
-  const url = `${protocol}://${host}:${port}/health`;
+  // Validate host is provided
+  if (!host || host.trim() === '') {
+    return {
+      reachable: false,
+      error: 'Host is required',
+      errorCode: 'UNKNOWN',
+    };
+  }
+
+  // Use smart URL building - omit port if it's the default for the protocol
+  const url = buildProxyUrl(host, port, protocol, '/health');
   const startTime = Date.now();
 
   try {
diff --git a/src/config/unified-config-loader.ts b/src/config/unified-config-loader.ts
index 98c72da1..24a36b0b 100644
--- a/src/config/unified-config-loader.ts
+++ b/src/config/unified-config-loader.ts
@@ -184,7 +184,8 @@ function mergeWithDefaults(partial: Partial<UnifiedConfig>): UnifiedConfig {
         enabled:
           partial.cliproxy_server?.remote?.enabled ?? DEFAULT_CLIPROXY_SERVER_CONFIG.remote.enabled,
         host: partial.cliproxy_server?.remote?.host ?? DEFAULT_CLIPROXY_SERVER_CONFIG.remote.host,
-        port: partial.cliproxy_server?.remote?.port ?? DEFAULT_CLIPROXY_SERVER_CONFIG.remote.port,
+        // Port is optional - undefined means use protocol default (443/80)
+        port: partial.cliproxy_server?.remote?.port,
         protocol:
           partial.cliproxy_server?.remote?.protocol ??
           DEFAULT_CLIPROXY_SERVER_CONFIG.remote.protocol,
diff --git a/src/config/unified-config-types.ts b/src/config/unified-config-types.ts
index fcffd26d..271ee7f5 100644
--- a/src/config/unified-config-types.ts
+++ b/src/config/unified-config-types.ts
@@ -195,8 +195,14 @@ export interface ProxyRemoteConfig {
   enabled: boolean;
   /** Remote proxy hostname or IP (empty = not configured) */
   host: string;
-  /** Remote proxy port (default: 8317) */
-  port: number;
+  /**
+   * Remote proxy port.
+   * Optional - defaults based on protocol:
+   * - HTTPS: 443
+   * - HTTP: 80
+   * When empty/undefined, uses protocol default.
+   */
+  port?: number;
   /** Protocol for remote connection */
   protocol: 'http' | 'https';
   /** Auth token for remote proxy (optional, sent as header) */
@@ -345,12 +351,13 @@ export const DEFAULT_COPILOT_CONFIG: CopilotConfig = {
 /**
  * Default CLIProxy server configuration.
  * Local mode by default - remote must be explicitly enabled.
+ * Port is optional for remote - defaults based on protocol.
  */
 export const DEFAULT_CLIPROXY_SERVER_CONFIG: CliproxyServerConfig = {
   remote: {
     enabled: false,
     host: '',
-    port: 8317,
+    // port is intentionally omitted - will use protocol default (443 for HTTPS, 80 for HTTP)
     protocol: 'http',
     auth_token: '',
   },
diff --git a/src/web-server/routes/proxy-routes.ts b/src/web-server/routes/proxy-routes.ts
index 2a9b1d9a..51978bf1 100644
--- a/src/web-server/routes/proxy-routes.ts
+++ b/src/web-server/routes/proxy-routes.ts
@@ -72,14 +72,20 @@ router.post('/test', async (req: Request, res: Response) => {
   try {
     const { host, port, protocol, authToken, allowSelfSigned } = req.body;
 
-    if (!host || !port) {
-      res.status(400).json({ error: 'Host and port are required' });
+    // Host is required, port is optional (uses protocol defaults)
+    if (!host) {
+      res.status(400).json({ error: 'Host is required' });
       return;
     }
 
+    // Parse port - treat empty string, 0, null as "use default"
+    const parsedPort = port && port !== '' ? parseInt(String(port), 10) : undefined;
+    const effectivePort =
+      parsedPort && !isNaN(parsedPort) && parsedPort > 0 ? parsedPort : undefined;
+
     const status = await testConnection({
       host,
-      port: typeof port === 'number' ? port : parseInt(port, 10),
+      port: effectivePort,
       protocol: protocol || 'http',
       authToken,
       allowSelfSigned: allowSelfSigned || false,
diff --git a/ui/src/lib/api-client.ts b/ui/src/lib/api-client.ts
index 4e0f6d21..5a4e8881 100644
--- a/ui/src/lib/api-client.ts
+++ b/ui/src/lib/api-client.ts
@@ -166,7 +166,8 @@ export interface RemoteProxyStatus {
 export interface ProxyRemoteConfig {
   enabled: boolean;
   host: string;
-  port: number;
+  /** Port is optional - uses protocol default (443 for HTTPS, 80 for HTTP) */
+  port?: number;
   protocol: 'http' | 'https';
   auth_token: string;
 }
@@ -402,7 +403,8 @@ export const api = {
     /** Test remote proxy connection */
     test: (params: {
       host: string;
-      port: number;
+      /** Port is optional - uses protocol default (443 for HTTPS, 80 for HTTP) */
+      port?: number;
       protocol: 'http' | 'https';
       authToken?: string;
       allowSelfSigned?: boolean;
diff --git a/ui/src/pages/settings.tsx b/ui/src/pages/settings.tsx
index 1fdb9138..a30e46cb 100644
--- a/ui/src/pages/settings.tsx
+++ b/ui/src/pages/settings.tsx
@@ -463,8 +463,8 @@ export function SettingsPage() {
     if (!proxyConfig) return;
 
     const { host, port, protocol, auth_token } = proxyConfig.remote;
-    if (!host || !port) {
-      setProxyError('Host and port are required');
+    if (!host) {
+      setProxyError('Host is required');
       return;
     }
 
@@ -475,7 +475,7 @@ export function SettingsPage() {
 
       const result = await api.cliproxyServer.test({
         host,
-        port,
+        port: port || undefined, // Empty/0 means use protocol default
         protocol,
         authToken: auth_token || undefined,
       });
@@ -1310,20 +1310,24 @@ function ProxyContent({
   fetchCliproxyServerConfig,
   fetchRawConfig,
 }: ProxyContentProps) {
-  // Memoized default config to avoid recreation
+  // Default configs for fallback
   const defaultRemote = {
     enabled: false,
     host: '',
-    port: 8317,
+    port: undefined as number | undefined,
     protocol: 'http' as const,
     auth_token: '',
   };
   const defaultFallback = { enabled: true, auto_start: true };
   const defaultLocal = { port: 8317, auto_start: true };
 
+  // Helper to get default port based on protocol
+  const getDefaultPort = (protocol: 'http' | 'https') => (protocol === 'https' ? 443 : 80);
+
   // Sync local state with config (using refs to avoid lint warnings)
   const hostInput = config?.remote.host ?? '';
-  const portInput = (config?.remote.port ?? 8317).toString();
+  // Show empty string for port if undefined (will use protocol default)
+  const portInput = config?.remote.port !== undefined ? config.remote.port.toString() : '';
   const authTokenInput = config?.remote.auth_token ?? '';
   const localPortInput = (config?.local.port ?? 8317).toString();
 
@@ -1365,9 +1369,13 @@ function ProxyContent({
   };
 
   const savePort = () => {
-    const port = parseInt(editedPort ?? displayPort, 10);
-    if (!isNaN(port) && port !== config?.remote.port) {
-      saveCliproxyServerConfig({ remote: { ...remoteConfig, port } });
+    const portStr = editedPort ?? displayPort;
+    // Empty string means use protocol default (undefined)
+    const port = portStr === '' ? undefined : parseInt(portStr, 10);
+    const effectivePort = port && !isNaN(port) && port > 0 ? port : undefined;
+
+    if (effectivePort !== config?.remote.port) {
+      saveCliproxyServerConfig({ remote: { ...remoteConfig, port: effectivePort } });
     }
     setEditedPort(null);
   };
@@ -1496,13 +1504,19 @@ function ProxyContent({
               {/* Port and Protocol */}
               <div className="grid grid-cols-2 gap-3">
                 <div className="space-y-1">
-                  <label className="text-sm text-muted-foreground">Port</label>
+                  <label className="text-sm text-muted-foreground">
+                    Port{' '}
+                    <span className="text-xs opacity-70">
+                      (default: {getDefaultPort(config?.remote.protocol || 'http')})
+                    </span>
+                  </label>
                   <Input
-                    type="number"
+                    type="text"
+                    inputMode="numeric"
                     value={displayPort}
-                    onChange={(e) => setEditedPort(e.target.value)}
+                    onChange={(e) => setEditedPort(e.target.value.replace(/\D/g, ''))}
                     onBlur={savePort}
-                    placeholder="8317"
+                    placeholder={`Leave empty for ${getDefaultPort(config?.remote.protocol || 'http')}`}
                     className="font-mono"
                     disabled={saving}
                   />
@@ -1545,7 +1559,7 @@ function ProxyContent({
               <div className="space-y-3 pt-2">
                 <Button
                   onClick={handleTestConnection}
-                  disabled={testing || !displayHost || !displayPort}
+                  disabled={testing || !displayHost}
                   variant="outline"
                   className="w-full"
                 >