feat: restore gateway HMR and add WRN formatting

packages/dev-server/README.md

@@ -142,7 +142,7 @@ interface ProdOptions {
 
 ### `startGateway(opts)` — multi-app gateway
 
-Serves several apps behind one port and routes each request to the right app by its `Host` header. Each app runs as its own child process (full isolation); the gateway is a thin host-based reverse proxy for HTTP and WebSocket. Apps communicate at runtime via `@wrnexus/pubsub` (use the Redis driver so messages cross processes).
+Serves several apps behind one port and routes each request to the right app by its `Host` header. Each app runs as its own child process (full isolation); the gateway is a thin host-based reverse proxy for HTTP and WebSocket. In development, the gateway supervises every child: editing a page, component, API, or middleware restarts only that app and the HMR client reconnects to display the latest page. Apps communicate at runtime via `@wrnexus/pubsub` (use the Redis driver so messages cross processes).
 
 ```ts
 interface GatewayOptions {

packages/dev-server/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@wrnexus/dev-server",
-  "version": "0.2.18",
+  "version": "0.2.19",
   "type": "module",
   "main": "src/index.ts",
   "exports": {

packages/dev-server/src/gateway.ts

@@ -12,6 +12,7 @@
 import { spawn, type ChildProcess } from "node:child_process";
 import { join, resolve } from "node:path";
 import { fileURLToPath } from "node:url";
+import { RESTART_EXIT_CODE } from "./restart.ts";
 
 /** Per-app access control, enforced at the gateway before proxying. */
 export interface GatewayAuth {
@@ -71,7 +72,7 @@ export interface RunningGateway {
 interface Target extends GatewayApp {
   port: number;
   origin: string;
-  child: ChildProcess;
+  child?: ChildProcess;
 }
 
 interface WsBridge {
@@ -81,6 +82,18 @@ interface WsBridge {
   queue: (string | ArrayBufferLike | ArrayBufferView)[];
 }
 
+/** Decide whether a gateway child should be relaunched after it exits. */
+export function gatewayRestartDelay(
+  mode: "development" | "production",
+  code: number | null,
+  signal: NodeJS.Signals | null,
+): number | null {
+  if (mode !== "development" || signal) return null;
+  if (code === RESTART_EXIT_CODE) return 0;
+  if (code && code !== 0) return 1200;
+  return null;
+}
+
 /** Fixed-window rate limiter keyed by client IP. */
 function makeRateLimiter(max: number, windowMs: number) {
   const hits = new Map<string, { count: number; reset: number }>();
@@ -196,9 +209,9 @@ function applyEdgeHeaders(res: Response): Response {
 async function waitReady(target: Target, timeoutMs = 15000): Promise<void> {
   const deadline = Date.now() + timeoutMs;
   for (;;) {
-    if (target.child.exitCode !== null) {
+    if (!target.child || target.child.exitCode !== null) {
       throw new Error(
-        `app '${target.name}' exited with code ${target.child.exitCode} during startup`,
+        `app '${target.name}' exited with code ${target.child?.exitCode ?? "unknown"} during startup`,
       );
     }
     try {
@@ -245,28 +258,52 @@ export async function startGateway(opts: GatewayOptions): Promise<RunningGateway
   const displayHost = hostname === "0.0.0.0" || hostname === "::" ? "localhost" : hostname;
   const serveEntry = fileURLToPath(import.meta.resolve("@wrnexus/dev-server/serve-entry"));
 
+  let stopping = false;
   const targets: Target[] = opts.apps.map((app, i) => {
     const appPort = app.port ?? port + 1 + i;
     const dir = resolve(app.dir);
-    const child =
-      mode === "production"
-        ? spawn(process.execPath, [join(dir, "dist", "server.js")], {
-            stdio: "inherit",
-            env: { ...process.env, PORT: String(appPort) },
-          })
-        : spawn(
-            process.execPath,
-            [serveEntry, join(dir, "app"), String(appPort), mode, "127.0.0.1"],
-            {
+    const target: Target = {
+      ...app,
+      port: appPort,
+      origin: `http://127.0.0.1:${appPort}`,
+    };
+
+    const launch = (): void => {
+      if (stopping) return;
+      const child =
+        mode === "production"
+          ? spawn(process.execPath, [join(dir, "dist", "server.js")], {
               stdio: "inherit",
-            },
-          );
-    return { ...app, port: appPort, origin: `http://127.0.0.1:${appPort}`, child };
+              env: { ...process.env, PORT: String(appPort) },
+            })
+          : spawn(
+              process.execPath,
+              [serveEntry, join(dir, "app"), String(appPort), mode, "127.0.0.1"],
+              { stdio: "inherit" },
+            );
+      target.child = child;
+
+      child.once("exit", (code, signal) => {
+        if (stopping || target.child !== child) return;
+        const delay = gatewayRestartDelay(mode, code, signal);
+        if (delay === null) return;
+        if (delay > 0) {
+          console.error(`[wrnexus] app '${target.name}' exited (code ${code}); retrying in 1.2s…`);
+          setTimeout(launch, delay);
+        } else {
+          launch();
+        }
+      });
+    };
+
+    launch();
+    return target;
   });
 
   const stopChildren = () => {
+    stopping = true;
     for (const target of targets) {
-      if (target.child.exitCode === null) target.child.kill();
+      if (target.child?.exitCode === null) target.child.kill();
     }
   };
 

packages/dev-server/src/index.ts

@@ -28,9 +28,9 @@ import { createHandlers, type WsData } from "./runtime.ts";
 import { createDevAssetServer } from "./assets.ts";
 import { HmrHub } from "./hmr.ts";
 import { startWatcher } from "./watch.ts";
+import { RESTART_EXIT_CODE } from "./restart.ts";
 
-/** Exit code the child uses to ask the dev supervisor for a fresh process. */
-export const RESTART_EXIT_CODE = 97;
+export { RESTART_EXIT_CODE } from "./restart.ts";
 
 export interface ServeOptions {
   appDir: string;

packages/dev-server/src/restart.ts

@@ -0,0 +1,2 @@
+/** Exit code a dev-server child uses to request a clean supervisor restart. */
+export const RESTART_EXIT_CODE = 97;

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

@@ -4,6 +4,7 @@ import {
   forwardAuthFailure,
   forwardAuthHeaders,
   gatewayProxyHeaders,
+  gatewayRestartDelay,
 } from "../src/gateway.ts";
 
 test("gateway uses platform-safe hostname defaults", () => {
@@ -56,3 +57,11 @@ test("forward auth describes the original gateway request", () => {
   expect(headers.get("cookie")).toBe("session=abc");
   expect(headers.get("authorization")).toBe("Bearer token");
 });
+
+test("gateway respawns development apps after an HMR restart exit", () => {
+  expect(gatewayRestartDelay("development", 97, null)).toBe(0);
+  expect(gatewayRestartDelay("development", 1, null)).toBe(1200);
+  expect(gatewayRestartDelay("development", 0, null)).toBeNull();
+  expect(gatewayRestartDelay("development", 97, "SIGTERM")).toBeNull();
+  expect(gatewayRestartDelay("production", 97, null)).toBeNull();
+});