fix(gateway): keep production app ports private

packages/dev-server/src/gateway.ts

@@ -337,6 +337,9 @@ export async function startGateway(opts: GatewayOptions): Promise<RunningGateway
               env: {
                 ...process.env,
                 PORT: String(appPort),
+                // App ports are private gateway internals. Loopback prevents
+                // clients from bypassing gateway auth and edge middleware.
+                WRNEXUS_HOSTNAME: "127.0.0.1",
                 WRNEXUS_ENV: environment,
                 WRNEXUS_APP_NAME: app.name,
                 WRNEXUS_APP_ORIGIN: app.publicOrigin ?? `http://${app.domains[0]}:${port}`,

packages/dev-server/src/prod.ts

@@ -141,6 +141,15 @@ function resolvePort(explicit?: number): number {
   return Number.isFinite(parsed) ? parsed : 3000;
 }
 
+/** Resolve the production bind address. Gateway-managed app servers override
+ * this with loopback so only the gateway is externally reachable. */
+export function resolveProductionHostname(
+  explicit?: string,
+  environmentHostname = process.env.WRNEXUS_HOSTNAME,
+): string {
+  return environmentHostname?.trim() || explicit || "0.0.0.0";
+}
+
 /** Build the route-matching tables + a module map from the manifest. */
 function buildProdRouter(manifest: ProdManifest): {
   router: Router;
@@ -353,7 +362,7 @@ export async function createProductionServer(manifest: ProdManifest, opts: ProdO
 
   const server = Bun.serve<WsData>({
     port: resolvePort(opts.port),
-    hostname: opts.hostname ?? "0.0.0.0",
+    hostname: resolveProductionHostname(opts.hostname),
     development: false,
     maxRequestBodySize: opts.maxBodyBytes ?? 10 * 1024 * 1024,
     fetch: handlers.fetch,

packages/dev-server/test/gateway.test.ts

@@ -6,6 +6,14 @@ import {
   gatewayProxyHeaders,
   gatewayRestartDelay,
 } from "../src/gateway.ts";
+import { resolveProductionHostname } from "../src/prod.ts";
+
+test("gateway-managed production apps bind to loopback", () => {
+  expect(resolveProductionHostname(undefined, "127.0.0.1")).toBe("127.0.0.1");
+  expect(resolveProductionHostname("0.0.0.0", "127.0.0.1")).toBe("127.0.0.1");
+  expect(resolveProductionHostname("10.0.0.5", "")).toBe("10.0.0.5");
+  expect(resolveProductionHostname(undefined, "")).toBe("0.0.0.0");
+});
 
 test("gateway uses platform-safe hostname defaults", () => {
   expect(defaultGatewayHostname("development")).toBe("127.0.0.1");