feat(gateway): add optional bonjour/mdns discovery

src/gateway/server.ts

@@ -9,6 +9,7 @@ import { LaneQueue } from './lane-queue.js';
 import { MetricsCollector } from './metrics.js';
 import { authenticateRequest } from './auth.js';
 import type { AuthConfig } from './auth.js';
+import { startGatewayDiscovery, type GatewayDiscoveryHandle } from './discovery.js';
 import {
   parseMessage,
   makeError,
@@ -86,6 +87,12 @@ export interface GatewayServerConfig {
   commandRegistry?: CommandRegistry;
   intentRegistry?: ComponentRegistry;
   routingPolicy?: RoutingPolicy;
+  discovery?: {
+    enabled: boolean;
+    serviceName: string;
+    serviceType: string;
+    txtRecord?: Record<string, string>;
+  };
 }
 
 export class GatewayServer {
@@ -103,6 +110,7 @@ export class GatewayServer {
   private sessionBridge: SessionBridge;
   private laneQueue: LaneQueue;
   private metrics: MetricsCollector;
+  private discoveryHandle: GatewayDiscoveryHandle | null = null;
   private connectionMap: Map<WebSocket, string> = new Map();
   private connectionRateMap: Map<string, {
     tokens: number;
@@ -272,12 +280,24 @@ export class GatewayServer {
 
       this.httpServer.listen(port, host, () => {
         console.log(`Gateway server listening on ${host}:${port}`);
-        resolve();
+        void this.startDiscovery(host, port).finally(() => {
+          resolve();
+        });
       });
     });
   }
 
   async stop(): Promise<void> {
+    if (this.discoveryHandle) {
+      try {
+        await this.discoveryHandle.stop();
+      } catch (err) {
+        console.error('Failed to stop mDNS discovery:', err instanceof Error ? err.message : err);
+      } finally {
+        this.discoveryHandle = null;
+      }
+    }
+
     // Close all WebSocket connections first
     for (const [ws, connectionId] of this.connectionMap) {
       this.sessionBridge.disconnect(connectionId);
@@ -543,6 +563,35 @@ export class GatewayServer {
     this.config.gmailHandler = handler;
   }
 
+  private async startDiscovery(host: string, port: number): Promise<void> {
+    const discovery = this.config.discovery;
+    if (!discovery?.enabled) {
+      return;
+    }
+
+    if (host === '127.0.0.1' || host === '::1') {
+      console.warn('mDNS discovery is enabled, but server.localhost=true restricts gateway to loopback; skipping advertisement');
+      return;
+    }
+
+    try {
+      const txtRecord: Record<string, string> = {
+        instance: `pid-${process.pid}`,
+        version: this.config.version ?? '0.1.0',
+        ...(discovery.txtRecord ?? {}),
+      };
+      this.discoveryHandle = await startGatewayDiscovery({
+        serviceName: discovery.serviceName,
+        serviceType: discovery.serviceType,
+        port,
+        txtRecord,
+      });
+      console.log(`mDNS discovery enabled: ${discovery.serviceName}.${discovery.serviceType}.local:${port}`);
+    } catch (err) {
+      console.warn(`mDNS discovery failed to start: ${err instanceof Error ? err.message : String(err)}`);
+    }
+  }
+
   /** Read the full request body as a string. */
   private readRequestBody(req: IncomingMessage): Promise<string> {
     const maxBytes = this.config.maxRequestBodyBytes ?? GatewayServer.DEFAULT_MAX_REQUEST_BODY_BYTES;