diff --git a/ui/src/ui/app-gateway.node.test.ts b/ui/src/ui/app-gateway.node.test.ts
new file mode 100644
index 00000000000..ee52c423d45
--- /dev/null
+++ b/ui/src/ui/app-gateway.node.test.ts
@@ -0,0 +1,146 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { connectGateway } from "./app-gateway.ts";
+
+type GatewayClientMock = {
+  start: ReturnType<typeof vi.fn>;
+  stop: ReturnType<typeof vi.fn>;
+  emitClose: (code: number, reason?: string) => void;
+  emitGap: (expected: number, received: number) => void;
+  emitEvent: (evt: { event: string; payload?: unknown; seq?: number }) => void;
+};
+
+const gatewayClientInstances: GatewayClientMock[] = [];
+
+vi.mock("./gateway.ts", () => {
+  class GatewayBrowserClient {
+    readonly start = vi.fn();
+    readonly stop = vi.fn();
+
+    constructor(
+      private opts: {
+        onClose?: (info: { code: number; reason: string }) => void;
+        onGap?: (info: { expected: number; received: number }) => void;
+        onEvent?: (evt: { event: string; payload?: unknown; seq?: number }) => void;
+      },
+    ) {
+      gatewayClientInstances.push({
+        start: this.start,
+        stop: this.stop,
+        emitClose: (code, reason) => {
+          this.opts.onClose?.({ code, reason: reason ?? "" });
+        },
+        emitGap: (expected, received) => {
+          this.opts.onGap?.({ expected, received });
+        },
+        emitEvent: (evt) => {
+          this.opts.onEvent?.(evt);
+        },
+      });
+    }
+  }
+
+  return { GatewayBrowserClient };
+});
+
+function createHost() {
+  return {
+    settings: {
+      gatewayUrl: "ws://127.0.0.1:18789",
+      token: "",
+      sessionKey: "main",
+      lastActiveSessionKey: "main",
+      theme: "system",
+      chatFocusMode: false,
+      chatShowThinking: true,
+      splitRatio: 0.6,
+      navCollapsed: false,
+      navGroupsCollapsed: {},
+    },
+    password: "",
+    client: null,
+    connected: false,
+    hello: null,
+    lastError: null,
+    eventLogBuffer: [],
+    eventLog: [],
+    tab: "overview",
+    presenceEntries: [],
+    presenceError: null,
+    presenceStatus: null,
+    agentsLoading: false,
+    agentsList: null,
+    agentsError: null,
+    debugHealth: null,
+    assistantName: "OpenClaw",
+    assistantAvatar: null,
+    assistantAgentId: null,
+    sessionKey: "main",
+    chatRunId: null,
+    refreshSessionsAfterChat: new Set<string>(),
+    execApprovalQueue: [],
+    execApprovalError: null,
+  } as unknown as Parameters<typeof connectGateway>[0];
+}
+
+describe("connectGateway", () => {
+  beforeEach(() => {
+    gatewayClientInstances.length = 0;
+  });
+
+  it("ignores stale client onGap callbacks after reconnect", () => {
+    const host = createHost();
+
+    connectGateway(host);
+    const firstClient = gatewayClientInstances[0];
+    expect(firstClient).toBeDefined();
+
+    connectGateway(host);
+    const secondClient = gatewayClientInstances[1];
+    expect(secondClient).toBeDefined();
+
+    firstClient.emitGap(10, 13);
+    expect(host.lastError).toBeNull();
+
+    secondClient.emitGap(20, 24);
+    expect(host.lastError).toBe(
+      "event gap detected (expected seq 20, got 24); refresh recommended",
+    );
+  });
+
+  it("ignores stale client onEvent callbacks after reconnect", () => {
+    const host = createHost();
+
+    connectGateway(host);
+    const firstClient = gatewayClientInstances[0];
+    expect(firstClient).toBeDefined();
+
+    connectGateway(host);
+    const secondClient = gatewayClientInstances[1];
+    expect(secondClient).toBeDefined();
+
+    firstClient.emitEvent({ event: "presence", payload: { presence: [{ host: "stale" }] } });
+    expect(host.eventLogBuffer).toHaveLength(0);
+
+    secondClient.emitEvent({ event: "presence", payload: { presence: [{ host: "active" }] } });
+    expect(host.eventLogBuffer).toHaveLength(1);
+    expect(host.eventLogBuffer[0]?.event).toBe("presence");
+  });
+
+  it("ignores stale client onClose callbacks after reconnect", () => {
+    const host = createHost();
+
+    connectGateway(host);
+    const firstClient = gatewayClientInstances[0];
+    expect(firstClient).toBeDefined();
+
+    connectGateway(host);
+    const secondClient = gatewayClientInstances[1];
+    expect(secondClient).toBeDefined();
+
+    firstClient.emitClose(1005);
+    expect(host.lastError).toBeNull();
+
+    secondClient.emitClose(1005);
+    expect(host.lastError).toBe("disconnected (1005): no reason");
+  });
+});
diff --git a/ui/src/ui/app-gateway.ts b/ui/src/ui/app-gateway.ts
index 4cfa01134e9..12b2c7b6d9e 100644
--- a/ui/src/ui/app-gateway.ts
+++ b/ui/src/ui/app-gateway.ts
@@ -122,14 +122,17 @@ export function connectGateway(host: GatewayHost) {
   host.execApprovalQueue = [];
   host.execApprovalError = null;
 
-  host.client?.stop();
-  host.client = new GatewayBrowserClient({
+  const previousClient = host.client;
+  const client = new GatewayBrowserClient({
     url: host.settings.gatewayUrl,
     token: host.settings.token.trim() ? host.settings.token : undefined,
     password: host.password.trim() ? host.password : undefined,
     clientName: "openclaw-control-ui",
     mode: "webchat",
     onHello: (hello) => {
+      if (host.client !== client) {
+        return;
+      }
       host.connected = true;
       host.lastError = null;
       host.hello = hello;
@@ -147,18 +150,31 @@ export function connectGateway(host: GatewayHost) {
       void refreshActiveTab(host as unknown as Parameters<typeof refreshActiveTab>[0]);
     },
     onClose: ({ code, reason }) => {
+      if (host.client !== client) {
+        return;
+      }
       host.connected = false;
       // Code 1012 = Service Restart (expected during config saves, don't show as error)
       if (code !== 1012) {
         host.lastError = `disconnected (${code}): ${reason || "no reason"}`;
       }
     },
-    onEvent: (evt) => handleGatewayEvent(host, evt),
+    onEvent: (evt) => {
+      if (host.client !== client) {
+        return;
+      }
+      handleGatewayEvent(host, evt);
+    },
     onGap: ({ expected, received }) => {
+      if (host.client !== client) {
+        return;
+      }
       host.lastError = `event gap detected (expected seq ${expected}, got ${received}); refresh recommended`;
     },
   });
-  host.client.start();
+  host.client = client;
+  previousClient?.stop();
+  client.start();
 }
 
 export function handleGatewayEvent(host: GatewayHost, evt: GatewayEventFrame) {