diff --git a/apps/desktop/src/app/contrib/surfaces-reactivity.test.tsx b/apps/desktop/src/app/contrib/surfaces.late-routes.test.tsx
similarity index 50%
rename from apps/desktop/src/app/contrib/surfaces-reactivity.test.tsx
rename to apps/desktop/src/app/contrib/surfaces.late-routes.test.tsx
index b3ae15977e..f7b0abe26a 100644
--- a/apps/desktop/src/app/contrib/surfaces-reactivity.test.tsx
+++ b/apps/desktop/src/app/contrib/surfaces.late-routes.test.tsx
@@ -1,3 +1,12 @@
+/**
+ * A plugin page route registered AFTER the workspace surface mounts must
+ * become navigable. Regression for late-loaded desktop plugins (disk plugins
+ * load async): the route table was compiled into a memo slot keyed on
+ * unrelated props, so a late `routes`-area registration never entered the
+ * table — the sidebar row rendered but navigating to the path fell through
+ * to the `:sessionId` chat route. Uses the REAL useContributions + registry
+ * (unlike surfaces.test.tsx) because the reactive flow is the subject.
+ */
 import { act, cleanup, render, screen } from '@testing-library/react'
 import { atom } from 'nanostores'
 import { MemoryRouter } from 'react-router'
@@ -8,13 +17,6 @@ import { registry } from '@/contrib/registry'
 import { ChatRoutesSurface } from './surfaces'
 import type { WiringActions } from './types'
 
-// #109063: the workspace surface subscribes to ROUTES_AREA but used to derive
-// routes via an independently-called `contributedRoutes()`, which React
-// Compiler can keep memoized across the delivered subscription update. The
-// registry, `useContributions` and the routes module all stay REAL here — only
-// unrelated stores and heavy sibling views are stubbed, because mocking the
-// route list is exactly what hid the defect.
-
 vi.mock('@/store/connections', () => ({ $activeConnectionId: atom('local') }))
 vi.mock('@/store/gateway', () => ({ $gateway: atom<unknown>(null) }))
 vi.mock('@/store/profile', () => ({ $activeGatewayProfile: atom('default') }))
@@ -30,61 +32,44 @@ vi.mock('../shell/hooks/use-statusbar-items', () => ({
   useStatusbarItems: () => ({ leftStatusbarItems: [], statusbarItems: [] })
 }))
 vi.mock('../shell/statusbar-controls', () => ({ StatusbarControls: () => null }))
-vi.mock('../shell/model-menu-panel', () => ({ ModelMenuPanel: () => null }))
 vi.mock('./latest-actions', () => ({ latestChatActions: () => ({}), latestSidebarActions: () => ({}) }))
 vi.mock('./panes', () => ({ setStatusbarItemGroup: vi.fn(), useStatusbarContributions: () => [] }))
+vi.mock('../shell/model-menu-panel', () => ({ ModelMenuPanel: () => null }))
+vi.mock('../shell/reasoning-menu-panel', () => ({ ReasoningMenuPanel: () => null }))
 
-afterEach(cleanup)
+afterEach(() => {
+  cleanup()
+})
 
-/** Register (or hot-replace) the plugin route page mounted at `/resetwatch`. */
-function registerResetwatch(label: string) {
-  return registry.register({
-    id: 'resetwatch',
-    area: 'routes',
-    title: `Resetwatch ${label}`,
-    data: { path: '/resetwatch' },
-    render: () => <div>{`PLUGIN-PAGE-${label}`}</div>
-  })
-}
-
-describe('ChatRoutesSurface route-contribution reactivity (#109063)', () => {
-  it('mounts a plugin page registered after the surface, tracks replacement, and unmounts on dispose', () => {
-    const actions = { getGateway: () => null } as unknown as WiringActions
+describe('ChatRoutesSurface late-registered plugin routes', () => {
+  it('renders a page whose route registers after mount', () => {
+    const actions = {} as unknown as WiringActions
 
     render(
-      <MemoryRouter initialEntries={['/resetwatch']}>
+      <MemoryRouter initialEntries={['/late-plugin']}>
         <ChatRoutesSurface actions={actions} />
       </MemoryRouter>
     )
-    // Unregistered path falls through the catch-all redirect to the chat view.
+
+    // Before registration the path falls through to the chat catch-all.
+    expect(screen.queryByTestId('late-page')).toBeNull()
     expect(screen.getByTestId('chat-view')).toBeTruthy()
 
     let dispose = () => {}
     act(() => {
-      // Late registration after the surface has mounted and settled.
-      dispose = registerResetwatch('A')
+      dispose = registry.register({
+        area: 'routes',
+        id: 'late-plugin:page',
+        data: { path: '/late-plugin' },
+        render: () => <div data-testid="late-page" />
+      })
     })
-    expect(screen.getByText('PLUGIN-PAGE-A')).toBeTruthy()
+
+    // The late registration must reach the route table and win over the
+    // `:sessionId` dynamic route.
+    expect(screen.getByTestId('late-page')).toBeTruthy()
     expect(screen.queryByTestId('chat-view')).toBeNull()
 
-    act(() => {
-      dispose()
-      dispose = registerResetwatch('B')
-    })
-    expect(screen.getByText('PLUGIN-PAGE-B')).toBeTruthy()
-
-    act(() => {
-      dispose()
-    })
-    expect(screen.getByTestId('chat-view')).toBeTruthy()
-
-    act(() => {
-      dispose = registerResetwatch('A')
-    })
-    expect(screen.getByText('PLUGIN-PAGE-A')).toBeTruthy()
-
-    act(() => {
-      dispose()
-    })
+    act(() => dispose())
   })
 })