feat(gateway): add websocket ingress rate limiting

src/gateway/server.test.ts

@@ -503,3 +503,77 @@ describe('GatewayServer request body limits', () => {
     expect(gmailHandler.handlePushNotification).not.toHaveBeenCalled();
   });
 });
+
+describe('GatewayServer WebSocket ingress rate limiting', () => {
+  const RATE_PORT = 18895;
+  let rateServer: GatewayServer;
+
+  beforeAll(async () => {
+    if (!LISTEN_ALLOWED) {
+      return;
+    }
+    rateServer = new GatewayServer({
+      port: RATE_PORT,
+      sessionManager: mockSessionManager as unknown as GatewayServerConfig['sessionManager'],
+      modelClient: mockModelClient,
+      systemPrompt: 'Test prompt',
+      toolRegistry: mockToolRegistry as unknown as GatewayServerConfig['toolRegistry'],
+      toolExecutor: mockToolExecutor as unknown as GatewayServerConfig['toolExecutor'],
+      uiDir: resolve(import.meta.dirname, 'ui'),
+      wsRateLimit: {
+        enabled: true,
+        capacity: 2,
+        refillPerSec: 1,
+        maxViolations: 3,
+        violationWindowMs: 10_000,
+      },
+    });
+    await rateServer.start();
+  });
+
+  afterAll(async () => {
+    if (!LISTEN_ALLOWED) {
+      return;
+    }
+    await rateServer.stop();
+  });
+
+  it('throttles bursts and closes repeated offenders', async () => {
+    if (!LISTEN_ALLOWED) {
+      return;
+    }
+
+    const ws = await new Promise<WebSocket>((resolve, reject) => {
+      const c = new WebSocket(`ws://127.0.0.1:${RATE_PORT}`);
+      c.on('open', () => resolve(c));
+      c.on('error', reject);
+    });
+
+    try {
+      const first = await sendAndReceive(ws, { id: 1, method: 'system.health' });
+      expect((first as GatewayResponse).id).toBe(1);
+
+      const second = await sendAndReceive(ws, { id: 2, method: 'system.health' });
+      expect((second as GatewayResponse).id).toBe(2);
+
+      const third = await sendAndReceive(ws, { id: 3, method: 'system.health' });
+      const rateErr = third as GatewayError;
+      expect(rateErr.error.code).toBe(ErrorCode.InternalError);
+      expect(rateErr.error.message).toContain('Rate limit exceeded');
+
+      // Trigger additional violations; server should close on max violation threshold.
+      ws.send(JSON.stringify({ id: 4, method: 'system.health' }));
+      ws.send(JSON.stringify({ id: 5, method: 'system.health' }));
+
+      const close = await new Promise<{ code: number; reason: string }>((resolve) => {
+        ws.on('close', (code, reason) => resolve({ code, reason: reason.toString() }));
+      });
+      expect(close.code).toBe(4008);
+      expect(close.reason).toContain('Rate limit exceeded');
+    } finally {
+      if (ws.readyState === WebSocket.OPEN) {
+        ws.close();
+      }
+    }
+  });
+});