diff --git a/packages/api/session-controller/src/history.ts b/packages/api/session-controller/src/history.ts
index 19fe5dc5bc..07fbbfe6be 100644
--- a/packages/api/session-controller/src/history.ts
+++ b/packages/api/session-controller/src/history.ts
@@ -393,7 +393,7 @@ function paginate(
   events: readonly SessionEvent[],
   beforeSeq: SessionLogOffsetType | undefined,
   maxMessages: number,
-  throughSeq: SessionSeqCursor = events.at(-1)?.seq ?? -1,
+  throughSeq: SessionSeqCursor,
   turnWindow?: SessionPageRequest['turnWindow'],
 ): { readonly events: SessionEvent[]; readonly hasMore: boolean } {
   const end = SessionLogOffset(Math.min(throughSeq + 1, beforeSeq ?? throughSeq + 1))
diff --git a/packages/client/ui-agent-preset/tests/section.client.spec.tsx b/packages/client/ui-agent-preset/tests/section.client.spec.tsx
index 9add87de92..2079d0c67a 100644
--- a/packages/client/ui-agent-preset/tests/section.client.spec.tsx
+++ b/packages/client/ui-agent-preset/tests/section.client.spec.tsx
@@ -193,13 +193,19 @@ it('closes help even when the browser reports no previously focused element', ()
 it.each([false, true])('only offers a description tooltip when the card clips it: %s', (overflow) => {
   vi.spyOn(Element.prototype, 'scrollHeight', 'get').mockReturnValue(overflow ? 400 : 80)
   vi.spyOn(Element.prototype, 'clientHeight', 'get').mockReturnValue(80)
-  const disconnect = vi.fn()
-  vi.stubGlobal('ResizeObserver', class { observe() {} disconnect = disconnect })
+  const disconnect = vi.spyOn(ResizeObserver.prototype, 'disconnect')
   vi.useFakeTimers()
   view({ rows: [{ id: 'mine', isDefault: false, description: 'Preset description' }] })
   fireEvent.mouseEnter(screen.getByText('Preset description'))
   act(() => { vi.advanceTimersByTime(400) })
   expect(screen.queryByRole('tooltip')?.textContent ?? null).toBe(overflow ? 'Preset description' : null)
   cleanup()
-  expect(disconnect).toHaveBeenCalledOnce()
+  expect(disconnect).toHaveBeenCalledTimes(overflow ? 2 : 1)
+})
+it('renders descriptions and allows selection without resize observation', () => {
+  vi.stubGlobal('ResizeObserver', undefined)
+  const actions = view({ rows: [{ id: 'mine', name: 'Mine', isDefault: false, description: 'Preset description' }] })
+  expect(screen.getByText('Preset description')).toBeTruthy()
+  fireEvent.click(screen.getByRole('button', { name: `${en.setDefault}: Mine` }))
+  expect(actions.makeDefault).toHaveBeenCalledWith('mine')
 })
diff --git a/packages/client/ui-conversation/tests/control-row-dom.ts b/packages/client/ui-conversation/tests/control-row-dom.ts
index 4c1cbc502e..7afc5ffaf7 100644
--- a/packages/client/ui-conversation/tests/control-row-dom.ts
+++ b/packages/client/ui-conversation/tests/control-row-dom.ts
@@ -1,12 +1,8 @@
-/** jsdom omits resize observation and font loading; layout tests drive their own measurements. */
+/** jsdom font-loading events; layout tests drive their own measurements. */
 import { beforeEach, afterEach, vi } from 'vitest'
 
 const fonts = Object.getOwnPropertyDescriptor(document, 'fonts')
 beforeEach(() => {
-  vi.stubGlobal('ResizeObserver', class {
-    observe(): void {}
-    disconnect(): void {}
-  })
   Object.defineProperty(document, 'fonts', { configurable: true, value: new EventTarget() })
 })
 afterEach(() => {
diff --git a/packages/client/ui-dockkit/tests/components.client.spec.tsx b/packages/client/ui-dockkit/tests/components.client.spec.tsx
index 85768ebb55..d2ed9768b9 100644
--- a/packages/client/ui-dockkit/tests/components.client.spec.tsx
+++ b/packages/client/ui-dockkit/tests/components.client.spec.tsx
@@ -462,7 +462,8 @@ describe('DockSurface', () => {
     expect(document.querySelector('[data-dockkit-split-button]')).toBeNull()
   })
 
-  it('names the chip box\'s hidden sides in data-dockkit-strip-scroll as it scrolls', () => {
+  it.each([true, false])('names the chip box\'s hidden sides as it scrolls with resize observation: %s', (observed) => {
+    if (!observed) vi.stubGlobal('ResizeObserver', undefined)
     let scrollLeft = 0
     const descriptors = ['scrollLeft', 'scrollWidth', 'clientWidth'].map(name =>
       [name, Object.getOwnPropertyDescriptor(Element.prototype, name)] as const)
diff --git a/packages/client/ui-primitives/tests/tooltip.client.spec.tsx b/packages/client/ui-primitives/tests/tooltip.client.spec.tsx
index b8d0825b91..787475f721 100644
--- a/packages/client/ui-primitives/tests/tooltip.client.spec.tsx
+++ b/packages/client/ui-primitives/tests/tooltip.client.spec.tsx
@@ -48,6 +48,9 @@ describe('Tooltip', () => {
     const bubble = view.container.querySelector<HTMLElement>('[role="tooltip"]')!
     expect(measured.mock.contexts).toEqual([anchor])
     expect(bubble.style.visibility).toBe('hidden')
+    fireEvent(window, new Event('resize'))
+    expect(bubble.style.visibility).toBe('hidden')
+    expect(measured.mock.contexts).toEqual([anchor])
     bubbleSize = { inlineSize: 100, blockSize: 20 }
     act(() => { observers[0]!.deliver() })
     expect(screen.getByRole('tooltip').style.left).toBe('62px')
diff --git a/packages/client/ui-sidebar-documentpreview/tests/zoom-viewport.client.spec.tsx b/packages/client/ui-sidebar-documentpreview/tests/zoom-viewport.client.spec.tsx
index f7a38e249e..a073c31637 100644
--- a/packages/client/ui-sidebar-documentpreview/tests/zoom-viewport.client.spec.tsx
+++ b/packages/client/ui-sidebar-documentpreview/tests/zoom-viewport.client.spec.tsx
@@ -66,6 +66,23 @@ it('resolves missing and small content to 100 percent', () => {
   expect(fitWidthZoom(200, 100, 24)).toBe(1)
 })
 
+it('fits the initial pane and allows fixed zoom without resize observation', () => {
+  vi.stubGlobal('ResizeObserver', undefined)
+  const onPreference = vi.fn()
+  render(<ZoomViewport preference={FIT_WIDTH} intrinsicWidth={1000} horizontalInset={20}
+    labels={{ controls: 'Zoom controls', menu: 'Choose zoom', out: 'Zoom out', into: 'Zoom in',
+      fitWidth: 'Fit width', value: percent => `${String(percent)}%` }} signal={new AbortController().signal}
+    scrollportRef={() => {}} onPreference={onPreference}>
+    <div className={zoomSurfaceClass} />
+  </ZoomViewport>)
+  const menu = screen.getByRole('button', { name: 'Choose zoom' })
+  expect(menu.textContent).toContain('48%')
+  fireEvent.click(menu)
+  fireEvent.click(screen.getByRole('menuitem', { name: '100%' }))
+  expect(onPreference).toHaveBeenCalledExactlyOnceWith({ kind: 'fixed', scale: 1 })
+  expect(menu.textContent).toContain('100%')
+})
+
 it('keeps a centred surface point under the pointer while crossing into overflow', () => {
   const onPreference = vi.fn()
   const view = render(<ZoomViewport preference={{ kind: 'fixed', scale: 0.5 }} intrinsicWidth={400}