@@ -0,0 +1,222 @@
+import {
+  EnvironmentId,
+  ThreadId,
+  type DeviceServiceState,
+  type ScopedThreadRef,
+} from "@t3tools/contracts";
+import { act, type ReactNode } from "react";
+import { create, type ReactTestRenderer } from "react-test-renderer";
+import { beforeEach, describe, expect, it, vi } from "vite-plus/test";
+
+import type { RightPanelSurface } from "~/rightPanelStore";
+
+import { DevicePanel } from "./DevicePanel";
+
+type CommandResult =
+  | { _tag: "Success"; value: { hostId: string; deviceId: string } }
+  | { _tag: "Failure"; cause: unknown };
+const mocks = vi.hoisted(() => ({
+  open: vi.fn<(request: unknown) => Promise<CommandResult>>(),
+  close: vi.fn<(request: unknown) => Promise<CommandResult>>(),
+  openDevice: vi.fn(),
+  closeSurface: vi.fn(),
+}));
+const phone = {
+  hostId: "local",
+  id: "phone",
+  name: "Phone",
+  platform: "ios",
+  version: "iOS 19",
+  booted: false,
+  physical: false,
+} as const;
+const deviceState: DeviceServiceState = {
+  hosts: [
+    {
+      id: "local",
+      kind: "local",
+      label: "This Mac",
+      platforms: [{ platform: "ios", available: true }],
+      hubInstalled: true,
+      agentDeviceInstalled: true,
+    },
+  ],
+  hostStatus: "ready",
+  hostStatuses: { local: { status: "ready" } },
+  devices: [phone],
+  sessions: [
+    {
+      threadId: ThreadId.make("thread-1"),
+      hostId: "local",
+      deviceId: "phone",
+      platform: "ios",
+      openedAt: "2026-01-01T00:00:00.000Z",
+    },
+  ],
+  onboardingCompleted: true,
+  agentAccessEnabled: true,
+  hubBasePath: "/api/device-hub",
+  revision: 1,
+};
+vi.mock("~/state/device", () => ({
+  deviceEnvironment: { list: "list", open: "open", close: "close" },
+  useDeviceState: () => ({ state: deviceState, loaded: true }),
+}));
+vi.mock("~/state/use-atom-command", () => ({
+  useAtomCommand: (command: string) =>
+    command === "open"
+      ? mocks.open
+      : command === "close"
+        ? mocks.close
+        : () => Promise.resolve({ _tag: "Success", value: {} }),
+}));
+vi.mock("~/state/query", () => ({ formatEnvironmentQueryError: () => "Device failed" }));
+vi.mock("~/rightPanelStore", () => ({
+  useRightPanelStore: {
+    getState: () => ({ openDevice: mocks.openDevice, closeSurface: mocks.closeSurface }),
+  },
+}));
+vi.mock("~/components/device/DeviceHostUpdates", () => ({ DeviceHostUpdates: () => null }));
+vi.mock("~/components/device/DeviceLoadingView", () => ({ DeviceLoadingView: () => null }));
+vi.mock("~/components/device/DeviceWorkspace", () => ({ DeviceWorkspace: () => null }));
+vi.mock("~/components/preview/PreviewPanelShell", () => ({
+  PreviewPanelShell: ({ children }: { children: ReactNode }) => children,
+}));
+
+// Same thread id in another environment: the surface id collides, so the panel
+// stays mounted across the switch, as it does under ChatView's surface key.
+const picking = {
+  environmentId: EnvironmentId.make("environment-a"),
+  threadId: ThreadId.make("thread-1"),
+};
+const next = { environmentId: EnvironmentId.make("environment-b"), threadId: picking.threadId };
+const picker: Extract<RightPanelSurface, { kind: "device" }> = { id: "device", kind: "device" };
+const streaming: Extract<RightPanelSurface, { kind: "device" }> = {
+  id: "device:phone",
+  kind: "device",
+  target: { hostId: "local", deviceId: "phone", platform: "ios", name: "Phone" },
+};
+
+const render = (threadRef: ScopedThreadRef, surface = picker) => (
+  <DevicePanel
+    key={surface.id}
+    mode="embedded"
+    threadRef={threadRef}
+    surface={surface}
+    visible
+    onDismissSetup={() => undefined}
+  />
+);
+const deferred = () => {
+  let settle!: (result: CommandResult) => void;
+  const promise = new Promise<CommandResult>((resolve) => (settle = resolve));
+  return { promise, settle };
+};
+const startPhone = (renderer: ReactTestRenderer) =>
+  act(async () => {
+    renderer.root.findByProps({ "aria-label": "Start Phone" }).props.onClick();
+  });
+const errors = (renderer: ReactTestRenderer) => renderer.root.findAllByProps({ role: "alert" });
+const opened = { _tag: "Success", value: { hostId: "local", deviceId: "phone" } } as const;
+
+beforeEach(() => {
+  vi.clearAllMocks();
+});
+
+describe("DevicePanel", () => {
+  it("opens a picked device when the pick settles in the same thread", async () => {
+    const pick = deferred();
+    mocks.open.mockReturnValue(pick.promise);
+    const renderer = await act(async () => create(render(picking)));
+
+    await startPhone(renderer);
+    expect(mocks.open).toHaveBeenCalledWith({
+      environmentId: picking.environmentId,
+      input: { threadId: picking.threadId, hostId: "local", deviceId: "phone", platform: "ios" },
+    });
+    await act(async () => pick.settle(opened));
+
+    expect(mocks.openDevice).toHaveBeenCalledExactlyOnceWith(picking, {
+      hostId: "local",
+      deviceId: "phone",
+      platform: "ios",
+      name: "Phone",
+    });
+  });
+
+  it("keeps the next thread's picker usable while an earlier pick is pending", async () => {
+    mocks.open.mockReturnValue(deferred().promise);
+    const renderer = await act(async () => create(render(picking)));
+
+    await startPhone(renderer);
+    await act(async () => renderer.update(render(next)));
+
+    expect(renderer.root.findByProps({ "aria-label": "Start Phone" }).props.disabled).toBe(false);
+  });
+
+  it("drops a pick that settles after the panel moved to a colliding thread", async () => {
+    const pick = deferred();
+    mocks.open.mockReturnValue(pick.promise);
+    const renderer = await act(async () => create(render(picking)));
+
+    await startPhone(renderer);
+    await act(async () => renderer.update(render(next)));
+    await act(async () => pick.settle(opened));
+
+    expect(mocks.openDevice).not.toHaveBeenCalled();
+  });
+
+  it("drops a failed pick that settles after the panel moved, even back again", async () => {
+    const pick = deferred();
+    mocks.open.mockReturnValue(pick.promise);
+    const renderer = await act(async () => create(render(picking)));
+
+    await startPhone(renderer);
+    await act(async () => renderer.update(render(next)));
+    await act(async () => renderer.update(render(picking)));
+    await act(async () => pick.settle({ _tag: "Failure", cause: new Error("boom") }));
+
+    expect(errors(renderer)).toHaveLength(0);
+    expect(mocks.openDevice).not.toHaveBeenCalled();
+  });
+
+  it("does not carry an operation error into another thread", async () => {
+    mocks.open.mockResolvedValue({ _tag: "Failure", cause: new Error("boom") });
+    const renderer = await act(async () => create(render(picking)));
+
+    await startPhone(renderer);
+    expect(errors(renderer)).toHaveLength(1);
+    await act(async () => renderer.update(render(next)));
+
+    expect(errors(renderer)).toHaveLength(0);
+  });
+
+  it("drops a power-off that settles after the panel moved to a colliding thread", async () => {
+    const powerOff = deferred();
+    mocks.close.mockReturnValue(powerOff.promise);
+    const renderer = await act(async () => create(render(picking, streaming)));
+
+    await act(async () => {
+      renderer.root.findByProps({ hostLabel: "This Mac" }).props.onPowerOff();
+    });
+    expect(mocks.close).toHaveBeenCalledWith({
+      environmentId: picking.environmentId,
+      input: { threadId: picking.threadId, hostId: "local", deviceId: "phone", shutdown: true },
+    });
+    await act(async () => renderer.update(render(next, streaming)));
+    await act(async () => powerOff.settle(opened));
+
+    expect(mocks.closeSurface).not.toHaveBeenCalled();
+  });
+
+  it("closes the surface when a power-off settles in the same thread", async () => {
+    mocks.close.mockResolvedValue(opened);
+    const renderer = await act(async () => create(render(picking, streaming)));
+
+    await act(async () => {
+      renderer.root.findByProps({ hostLabel: "This Mac" }).props.onPowerOff();
+    });
+
+    expect(mocks.closeSurface).toHaveBeenCalledExactlyOnceWith(picking, streaming.id);
+  });
+});
@@ -6,7 +6,7 @@ import type {
   ScopedThreadRef,
 } from "@t3tools/contracts";
 import { Smartphone, X } from "lucide-react";
-import { useEffect, useMemo, useState } from "react";
+import { useEffect, useLayoutEffect, useMemo, useRef, useState } from "react";
 
 import { usePreviewMiniPlayerStore } from "~/previewMiniPlayerStore";
 import { useRightPanelStore, type RightPanelSurface } from "~/rightPanelStore";
@@ -45,6 +45,15 @@ export function DevicePanel(props: {
   const close = useAtomCommand(deviceEnvironment.close);
   const [operationError, setOperationError] = useState<string | null>(null);
   const [pendingDevice, setPendingDevice] = useState<DeviceSummary | null>(null);
+  // Operation state belongs to one scoped thread; drop it when the panel moves on.
+  const scopeKey = `${environmentId}\u0000${threadId}`;
+  const [operationScopeKey, setOperationScopeKey] = useState(scopeKey);
+  if (operationScopeKey !== scopeKey) {
+    setOperationScopeKey(scopeKey);
+    setOperationError(null);
+    setPendingDevice(null);
+  }
+  const isCurrentScope = useScopeGuard(scopeKey);
   const pendingDeviceKey = pendingDevice ? deviceKey(pendingDevice) : null;
 
   const hostDisabled = state.hostStatus === "disabled";
@@ -79,6 +88,7 @@ export function DevicePanel(props: {
     if (!device) return;
     setOperationError(null);
     setPendingDevice(device);
+    const stillCurrent = isCurrentScope();
     try {
       const result = await open({
         environmentId,
@@ -89,6 +99,7 @@ export function DevicePanel(props: {
           platform: device.platform,
         },
       });
+      if (!stillCurrent()) return;
       if (result._tag === "Failure") setOperationError(formatEnvironmentQueryError(result.cause));
       else
         useRightPanelStore.getState().openDevice(props.threadRef, {
@@ -98,7 +109,7 @@ export function DevicePanel(props: {
           name: device.name,
         });
     } finally {
-      setPendingDevice(null);
+      if (stillCurrent()) setPendingDevice(null);
     }
   };
 
@@ -122,6 +133,7 @@ export function DevicePanel(props: {
     }
     if (!activeSession) return;
     setOperationError(null);
+    const stillCurrent = isCurrentScope();
     void close({
       environmentId,
       input: {
@@ -131,6 +143,7 @@ export function DevicePanel(props: {
         shutdown: powerOff,
       },
     }).then((result) => {
+      if (!stillCurrent()) return;
       if (result._tag === "Failure") setOperationError(formatEnvironmentQueryError(result.cause));
       else useRightPanelStore.getState().closeSurface(props.threadRef, props.surface.id);
     });
@@ -313,6 +326,27 @@ export function DevicePanel(props: {
   );
 }
 
+/**
+ * Binds async work to the committed scope. Call the returned function when the
+ * work starts; the check it returns is false once the panel moved to another
+ * thread (even back again) or unmounted, so late results are dropped.
+ */
+function useScopeGuard(scopeKey: string) {
+  const scopeRef = useRef<{ readonly key: string } | null>(null);
+  useLayoutEffect(() => {
+    // A fresh token per commit of a scope, so returning to a thread is a new scope.
+    const scope = { key: scopeKey };
+    scopeRef.current = scope;
+    return () => {
+      scopeRef.current = null;
+    };
+  }, [scopeKey]);
+  return () => {
+    const started = scopeRef.current;
+    return () => started !== null && scopeRef.current === started;
+  };
+}
+
 function groupDevices(state: DeviceServiceState) {
   const groups: Array<{ platform: DevicePlatform; devices: DeviceSummary[] }> = [];
   for (const platform of ["ios", "android"] as const) {