diff --git a/apps/desktop/src/app/chat/composer/attachments.test.tsx b/apps/desktop/src/app/chat/composer/attachments.test.tsx
index 8bde5b944592..52e8f6bf98e8 100644
--- a/apps/desktop/src/app/chat/composer/attachments.test.tsx
+++ b/apps/desktop/src/app/chat/composer/attachments.test.tsx
@@ -1,4 +1,4 @@
-import { cleanup, render, screen } from '@testing-library/react'
+import { act, cleanup, render, screen } from '@testing-library/react'
 import { afterEach, describe, expect, it } from 'vitest'
 
 import { I18nProvider } from '@/i18n/context'
@@ -10,12 +10,17 @@ function makeAttachment(id: string, label = 'test.pdf'): ComposerAttachment {
   return { id, kind: 'file', label }
 }
 
-function renderWithI18n(ui: React.ReactNode) {
-  return render(
-    <I18nProvider configClient={{ getConfig: async () => ({}), saveConfig: async () => ({ ok: true }) }}>
-      {ui}
-    </I18nProvider>
-  )
+async function renderWithI18n(ui: React.ReactNode) {
+  let result: ReturnType<typeof render>
+  await act(async () => {
+    result = render(
+      <I18nProvider configClient={{ getConfig: async () => ({}), saveConfig: async () => ({ ok: true }) }}>
+        {ui}
+      </I18nProvider>
+    )
+  })
+
+  return result!
 }
 
 describe('AttachmentList', () => {
@@ -23,22 +28,22 @@ describe('AttachmentList', () => {
     cleanup()
   })
 
-  it('renders valid attachments', () => {
+  it('renders valid attachments', async () => {
     const attachments = [makeAttachment('a', 'doc.pdf'), makeAttachment('b', 'img.png')]
-    renderWithI18n(<AttachmentList attachments={attachments} />)
+    await renderWithI18n(<AttachmentList attachments={attachments} />)
     expect(screen.getByText('doc.pdf')).toBeDefined()
     expect(screen.getByText('img.png')).toBeDefined()
   })
 
-  it('renders empty list without error', () => {
-    const { container } = renderWithI18n(<AttachmentList attachments={[]} />)
+  it('renders empty list without error', async () => {
+    const { container } = await renderWithI18n(<AttachmentList attachments={[]} />)
 
     const attachmentList = container.querySelector('[data-slot="composer-attachments"]')
 
     expect(attachmentList).toBeDefined()
   })
 
-  it('does not crash when attachments array contains undefined entries', () => {
+  it('does not crash when attachments array contains undefined entries', async () => {
     // Repro: session switch can leave stale/undefined entries in the
     // attachments array, causing a TypeError at attachment.refText.
     const attachments = [
@@ -47,21 +52,17 @@ describe('AttachmentList', () => {
       makeAttachment('b', 'also-good.png')
     ]
 
-    expect(() => {
-      renderWithI18n(<AttachmentList attachments={attachments} />)
-    }).not.toThrow()
+    await expect(renderWithI18n(<AttachmentList attachments={attachments} />)).resolves.toBeTruthy()
 
     // Only valid attachments should render
     expect(screen.getByText('good.pdf')).toBeDefined()
     expect(screen.getByText('also-good.png')).toBeDefined()
   })
 
-  it('does not crash when attachments array contains null entries', () => {
+  it('does not crash when attachments array contains null entries', async () => {
     const attachments = [null as unknown as ComposerAttachment, makeAttachment('a', 'valid.txt')]
 
-    expect(() => {
-      renderWithI18n(<AttachmentList attachments={attachments} />)
-    }).not.toThrow()
+    await expect(renderWithI18n(<AttachmentList attachments={attachments} />)).resolves.toBeTruthy()
 
     expect(screen.getByText('valid.txt')).toBeDefined()
   })
diff --git a/apps/desktop/src/app/chat/right-rail/preview-pane.test.tsx b/apps/desktop/src/app/chat/right-rail/preview-pane.test.tsx
index 51e5539bac9e..650900a42e9d 100644
--- a/apps/desktop/src/app/chat/right-rail/preview-pane.test.tsx
+++ b/apps/desktop/src/app/chat/right-rail/preview-pane.test.tsx
@@ -19,7 +19,7 @@ describe('PreviewPane console state', () => {
     vi.unstubAllGlobals()
   })
 
-  it('does not watch backend-only remote filesystem previews locally', () => {
+  it('does not watch backend-only remote filesystem previews locally', async () => {
     const watchPreviewFile = vi.fn(async () => ({ id: 'watch-1', path: '/remote/file.txt' }))
     const onPreviewFileChanged = vi.fn(() => vi.fn())
     $connection.set({ mode: 'remote' } as never)
@@ -31,38 +31,43 @@ describe('PreviewPane console state', () => {
       }
     })
 
-    render(
-      <PreviewPane
-        setTitlebarToolGroup={vi.fn()}
-        target={{
-          kind: 'file',
-          label: 'file.txt',
-          path: '/remote/file.txt',
-          previewKind: 'text',
-          source: '/remote/file.txt',
-          url: 'file:///remote/file.txt'
-        }}
-      />
-    )
+    await act(async () => {
+      render(
+        <PreviewPane
+          setTitlebarToolGroup={vi.fn()}
+          target={{
+            kind: 'file',
+            label: 'file.txt',
+            path: '/remote/file.txt',
+            previewKind: 'text',
+            source: '/remote/file.txt',
+            url: 'file:///remote/file.txt'
+          }}
+        />
+      )
+    })
 
     expect(watchPreviewFile).not.toHaveBeenCalled()
     expect(onPreviewFileChanged).not.toHaveBeenCalled()
   })
 
-  it('does not rebuild the pane titlebar group for streamed console logs', () => {
+  it('does not rebuild the pane titlebar group for streamed console logs', async () => {
     const setTitlebarToolGroup = vi.fn()
 
-    const rendered = render(
-      <PreviewPane
-        setTitlebarToolGroup={setTitlebarToolGroup}
-        target={{
-          kind: 'url',
-          label: 'Preview',
-          source: 'http://localhost:5174',
-          url: 'http://localhost:5174'
-        }}
-      />
-    )
+    let rendered!: ReturnType<typeof render>
+    await act(async () => {
+      rendered = render(
+        <PreviewPane
+          setTitlebarToolGroup={setTitlebarToolGroup}
+          target={{
+            kind: 'url',
+            label: 'Preview',
+            source: 'http://localhost:5174',
+            url: 'http://localhost:5174'
+          }}
+        />
+      )
+    })
 
     const initialCalls = setTitlebarToolGroup.mock.calls.length
     const webview = rendered.container.querySelector('webview')
diff --git a/apps/desktop/src/app/messaging/index.test.tsx b/apps/desktop/src/app/messaging/index.test.tsx
index a7d9273c0c90..b078a2043b1d 100644
--- a/apps/desktop/src/app/messaging/index.test.tsx
+++ b/apps/desktop/src/app/messaging/index.test.tsx
@@ -1,5 +1,5 @@
 // @vitest-environment jsdom
-import { cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { act, cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
 import { MemoryRouter } from 'react-router-dom'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
@@ -53,12 +53,16 @@ afterEach(() => {
 
 async function renderMessaging() {
   const { MessagingView } = await import('./index')
+  let result: ReturnType<typeof render>
+  await act(async () => {
+    result = render(
+      <MemoryRouter>
+        <MessagingView />
+      </MemoryRouter>
+    )
+  })
 
-  return render(
-    <MemoryRouter>
-      <MessagingView />
-    </MemoryRouter>
-  )
+  return result!
 }
 
 describe('MessagingView setup-guide link', () => {
@@ -82,7 +86,9 @@ describe('MessagingView setup-guide link', () => {
     await renderMessaging()
 
     const link = await screen.findByText('Open setup guide')
-    fireEvent.click(link)
+    await act(async () => {
+      fireEvent.click(link)
+    })
 
     await waitFor(() => expect(openExternalLink).toHaveBeenCalledWith(docsUrl))
   })
diff --git a/apps/desktop/src/app/session/hooks/use-prompt-actions/index.test.tsx b/apps/desktop/src/app/session/hooks/use-prompt-actions/index.test.tsx
index 66a216d14ae7..3e725b1480d3 100644
--- a/apps/desktop/src/app/session/hooks/use-prompt-actions/index.test.tsx
+++ b/apps/desktop/src/app/session/hooks/use-prompt-actions/index.test.tsx
@@ -1,4 +1,4 @@
-import { cleanup, render, waitFor } from '@testing-library/react'
+import { act, cleanup, render, waitFor } from '@testing-library/react'
 import type { MutableRefObject } from 'react'
 import { useEffect, useRef } from 'react'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
@@ -43,6 +43,18 @@ function sessionInfo(overrides: Partial<SessionInfo> = {}): SessionInfo {
   }
 }
 
+// Wrap render() in act() so the Harness's useEffect (onReady callback +
+// internal state from usePromptActions) flushes synchronously instead of
+// spilling async state updates outside act().
+async function actRender(ui: React.ReactElement) {
+  let result: ReturnType<typeof render>
+  await act(async () => {
+    result = render(ui)
+  })
+
+  return result!
+}
+
 interface HarnessHandle {
   cancelRun: () => Promise<void>
   restoreToMessage: (messageId: string, target?: { text?: string; userOrdinal?: number | null }) => Promise<void>
@@ -125,10 +137,14 @@ function Harness({
 
   useEffect(() => {
     onReady({
-      cancelRun: actions.cancelRun,
-      restoreToMessage: actions.restoreToMessage,
-      steerPrompt: actions.steerPrompt,
-      submitText: actions.submitText
+      cancelRun: (...args: Parameters<typeof actions.cancelRun>) =>
+        act(async () => actions.cancelRun(...args)) as Promise<void>,
+      restoreToMessage: (...args: Parameters<typeof actions.restoreToMessage>) =>
+        act(async () => actions.restoreToMessage(...args)) as Promise<void>,
+      steerPrompt: (...args: Parameters<typeof actions.steerPrompt>) =>
+        act(async () => actions.steerPrompt(...args)) as Promise<boolean>,
+      submitText: (...args: Parameters<typeof actions.submitText>) =>
+        act(async () => actions.submitText(...args)) as Promise<boolean>
     })
   }, [actions.cancelRun, actions.restoreToMessage, actions.steerPrompt, actions.submitText, onReady])
 
@@ -153,7 +169,9 @@ describe('usePromptActions /title', () => {
     )
 
     let handle: HarnessHandle | null = null
-    render(<Harness onReady={h => (handle = h)} refreshSessions={refreshSessions} requestGateway={requestGateway} />)
+    await actRender(
+      <Harness onReady={h => (handle = h)} refreshSessions={refreshSessions} requestGateway={requestGateway} />
+    )
 
     await handle!.submitText('/title New title')
 
@@ -177,7 +195,9 @@ describe('usePromptActions /title', () => {
     )
 
     let handle: HarnessHandle | null = null
-    render(<Harness onReady={h => (handle = h)} refreshSessions={refreshSessions} requestGateway={requestGateway} />)
+    await actRender(
+      <Harness onReady={h => (handle = h)} refreshSessions={refreshSessions} requestGateway={requestGateway} />
+    )
 
     await handle!.submitText('/title Fresh chat')
 
@@ -195,7 +215,9 @@ describe('usePromptActions /title', () => {
     const requestGateway = vi.fn(async () => ({ output: 'Title: Old title' }) as never)
 
     let handle: HarnessHandle | null = null
-    render(<Harness onReady={h => (handle = h)} refreshSessions={refreshSessions} requestGateway={requestGateway} />)
+    await actRender(
+      <Harness onReady={h => (handle = h)} refreshSessions={refreshSessions} requestGateway={requestGateway} />
+    )
 
     await handle!.submitText('/title')
 
@@ -215,7 +237,9 @@ describe('usePromptActions /title', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(<Harness onReady={h => (handle = h)} refreshSessions={refreshSessions} requestGateway={requestGateway} />)
+    await actRender(
+      <Harness onReady={h => (handle = h)} refreshSessions={refreshSessions} requestGateway={requestGateway} />
+    )
 
     await handle!.submitText('/title way too long title')
 
@@ -254,7 +278,7 @@ describe('usePromptActions slash.exec dispatch payloads', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         onSeedState={s => states.push(s)}
@@ -304,7 +328,7 @@ describe('usePromptActions slash.exec dispatch payloads', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         onSeedState={s => states.push(s)}
@@ -342,7 +366,7 @@ describe('usePromptActions slash.exec dispatch payloads', () => {
     const requestGateway = vi.fn(async () => ({}) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -372,7 +396,7 @@ describe('usePromptActions desktop slash pickers', () => {
     const requestGateway = vi.fn(async () => ({}) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         refreshSessions={async () => undefined}
@@ -392,7 +416,7 @@ describe('usePromptActions desktop slash pickers', () => {
     const requestGateway = vi.fn(async () => ({}) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         openMemoryGraph={openMemoryGraph}
@@ -425,7 +449,7 @@ describe('usePromptActions desktop slash pickers', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -455,7 +479,7 @@ describe('usePromptActions submit / queue drain semantics', () => {
     const requestGateway = vi.fn(async () => ({}) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         onSeedState={s => seeds.push(s)}
@@ -488,7 +512,7 @@ describe('usePromptActions submit / queue drain semantics', () => {
     const requestGateway = vi.fn(async () => ({}) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         busyRef={busyRef}
         onReady={h => (handle = h)}
@@ -530,7 +554,7 @@ describe('usePromptActions submit / queue drain semantics', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         refreshSessions={async () => undefined}
@@ -574,7 +598,7 @@ describe('usePromptActions submit / queue drain semantics', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         onSeedState={s => seeds.push(s)}
@@ -596,7 +620,7 @@ describe('usePromptActions submit / queue drain semantics', () => {
     const requestGateway = vi.fn(async () => ({}) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         busyRef={busyRef}
         onReady={h => (handle = h)}
@@ -622,7 +646,7 @@ describe('usePromptActions steerPrompt', () => {
     const requestGateway = vi.fn(async () => ({ status: 'queued' }) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -641,7 +665,7 @@ describe('usePromptActions steerPrompt', () => {
     const requestGateway = vi.fn(async () => ({ status: 'rejected' }) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -654,7 +678,7 @@ describe('usePromptActions steerPrompt', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -665,7 +689,7 @@ describe('usePromptActions steerPrompt', () => {
     const requestGateway = vi.fn(async () => ({ status: 'queued' }) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -697,7 +721,7 @@ describe('usePromptActions restoreToMessage', () => {
     let lastState: Record<string, unknown> = {}
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         onSeedState={state => (lastState = state)}
@@ -732,7 +756,7 @@ describe('usePromptActions restoreToMessage', () => {
     let lastState: Record<string, unknown> = {}
     let handle: HarnessHandle | null = null
 
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         onSeedState={state => (lastState = state)}
@@ -765,7 +789,7 @@ describe('usePromptActions restoreToMessage', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         refreshSessions={async () => undefined}
@@ -793,7 +817,7 @@ describe('usePromptActions restoreToMessage', () => {
     const requestGateway = vi.fn(async () => ({}) as never)
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -808,7 +832,7 @@ describe('usePromptActions restoreToMessage', () => {
 
     let lastState: Record<string, unknown> = {}
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         onSeedState={state => (lastState = state)}
@@ -882,7 +906,7 @@ describe('usePromptActions file attachment sync', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -936,7 +960,7 @@ describe('usePromptActions file attachment sync', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -965,7 +989,7 @@ describe('usePromptActions file attachment sync', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -1025,7 +1049,7 @@ describe('usePromptActions eager-upload races', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
     await waitFor(() => expect(handle).not.toBeNull())
@@ -1083,7 +1107,7 @@ describe('usePromptActions sleep/wake session recovery', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         refreshSessions={async () => undefined}
@@ -1126,7 +1150,7 @@ describe('usePromptActions sleep/wake session recovery', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         refreshSessions={async () => undefined}
@@ -1159,7 +1183,7 @@ describe('usePromptActions sleep/wake session recovery', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         onSeedState={s => states.push(s)}
@@ -1189,7 +1213,7 @@ describe('usePromptActions sleep/wake session recovery', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         refreshSessions={async () => undefined}
@@ -1233,7 +1257,7 @@ describe('usePromptActions sleep/wake session recovery', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         onReady={h => (handle = h)}
         refreshSessions={async () => undefined}
@@ -1273,7 +1297,7 @@ describe('usePromptActions sleep/wake session recovery', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         activeSessionId={null}
         createBackendSessionForSend={createBackendSessionForSend}
@@ -1315,7 +1339,7 @@ describe('usePromptActions sleep/wake session recovery', () => {
     })
 
     let handle: HarnessHandle | null = null
-    render(
+    await actRender(
       <Harness
         activeSessionId={null}
         activeSessionIdRef={activeSessionIdRef}
@@ -1592,7 +1616,7 @@ describe('usePromptActions eager attachment upload (drop-time)', () => {
       { id: 'file:devis', kind: 'file', label: 'DEVIS_signed.pdf', path: '/Users/mahmoud/Downloads/DEVIS_signed.pdf' }
     ])
 
-    render(
+    await actRender(
       <Harness onReady={() => undefined} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -1622,7 +1646,7 @@ describe('usePromptActions eager attachment upload (drop-time)', () => {
 
     $composerAttachments.set([{ id: 'file:x', kind: 'file', label: 'x.pdf', path: '/abs/x.pdf' }])
 
-    render(
+    await actRender(
       <Harness onReady={() => undefined} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
@@ -1646,7 +1670,7 @@ describe('usePromptActions eager attachment upload (drop-time)', () => {
       }
     ])
 
-    render(
+    await actRender(
       <Harness onReady={() => undefined} refreshSessions={async () => undefined} requestGateway={requestGateway} />
     )
 
diff --git a/apps/desktop/src/app/settings/provider-config-panel.test.tsx b/apps/desktop/src/app/settings/provider-config-panel.test.tsx
index 774d45f40793..fa95f9dcd70a 100644
--- a/apps/desktop/src/app/settings/provider-config-panel.test.tsx
+++ b/apps/desktop/src/app/settings/provider-config-panel.test.tsx
@@ -1,4 +1,4 @@
-import { cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { act, cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
 import type { MemoryProviderConfig } from '@/types/hermes'
@@ -97,7 +97,12 @@ afterEach(() => {
 async function renderPanel(provider = 'hindsight') {
   const { ProviderConfigPanel } = await import('./provider-config-panel')
 
-  return render(<ProviderConfigPanel provider={provider} />)
+  let result: ReturnType<typeof render>
+  await act(async () => {
+    result = render(<ProviderConfigPanel provider={provider} />)
+  })
+
+  return result!
 }
 
 describe('ProviderConfigPanel', () => {
@@ -115,9 +120,13 @@ describe('ProviderConfigPanel', () => {
     await renderPanel()
 
     expect(await screen.findByLabelText('API URL')).toBeTruthy()
-    fireEvent.click(screen.getByRole('button', { name: /Hindsight settings/ }))
+    await act(async () => {
+      fireEvent.click(screen.getByRole('button', { name: /Hindsight settings/ }))
+    })
     expect(screen.queryByLabelText('API URL')).toBeNull()
-    fireEvent.click(screen.getByRole('button', { name: /Hindsight settings/ }))
+    await act(async () => {
+      fireEvent.click(screen.getByRole('button', { name: /Hindsight settings/ }))
+    })
     expect(await screen.findByLabelText('API URL')).toBeTruthy()
   })
 
@@ -125,9 +134,11 @@ describe('ProviderConfigPanel', () => {
     await renderPanel()
 
     const apiUrl = await screen.findByLabelText('API URL')
-    fireEvent.change(apiUrl, { target: { value: 'http://localhost:8888' } })
-    fireEvent.change(screen.getByLabelText('Bank ID'), { target: { value: 'ben-bank' } })
-    fireEvent.click(screen.getByRole('button', { name: 'Save' }))
+    await act(async () => {
+      fireEvent.change(apiUrl, { target: { value: 'http://localhost:8888' } })
+      fireEvent.change(screen.getByLabelText('Bank ID'), { target: { value: 'ben-bank' } })
+      fireEvent.click(screen.getByRole('button', { name: 'Save' }))
+    })
 
     await waitFor(() =>
       expect(saveMemoryProviderConfig).toHaveBeenCalledWith('hindsight', {
diff --git a/apps/desktop/src/app/settings/providers-settings.test.tsx b/apps/desktop/src/app/settings/providers-settings.test.tsx
index 8a894e27ab15..ac63be962ae2 100644
--- a/apps/desktop/src/app/settings/providers-settings.test.tsx
+++ b/apps/desktop/src/app/settings/providers-settings.test.tsx
@@ -1,4 +1,4 @@
-import { cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { act, cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
 import { atom } from 'nanostores'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
@@ -73,8 +73,12 @@ afterEach(() => {
 
 async function renderProvidersSettings() {
   const { ProvidersSettings } = await import('./providers-settings')
+  let result: ReturnType<typeof render>
+  await act(async () => {
+    result = render(<ProvidersSettings onClose={vi.fn()} onViewChange={vi.fn()} view="accounts" />)
+  })
 
-  return render(<ProvidersSettings onClose={vi.fn()} onViewChange={vi.fn()} view="accounts" />)
+  return result!
 }
 
 describe('ProvidersSettings', () => {
@@ -82,7 +86,9 @@ describe('ProvidersSettings', () => {
     await renderProvidersSettings()
 
     const remove = await screen.findByRole('button', { name: 'Remove Nous Portal' })
-    fireEvent.click(remove)
+    await act(async () => {
+      fireEvent.click(remove)
+    })
 
     await waitFor(() => expect(disconnectOAuthProvider).toHaveBeenCalledWith('nous'))
     expect(listOAuthProviders).toHaveBeenCalledTimes(2)
@@ -91,7 +97,9 @@ describe('ProvidersSettings', () => {
   it('keeps provider selection separate from account removal', async () => {
     await renderProvidersSettings()
 
-    fireEvent.click(await screen.findByText('Nous Portal'))
+    await act(async () => {
+      fireEvent.click(await screen.findByText('Nous Portal'))
+    })
 
     expect(startManualProviderOAuth).toHaveBeenCalledWith('nous')
     expect(disconnectOAuthProvider).not.toHaveBeenCalled()
@@ -132,7 +140,9 @@ describe('ProvidersSettings', () => {
     listOAuthProviders.mockResolvedValue({ providers: [] })
 
     const { ProvidersSettings } = await import('./providers-settings')
-    render(<ProvidersSettings onClose={vi.fn()} onViewChange={vi.fn()} view="keys" />)
+    await act(async () => {
+      render(<ProvidersSettings onClose={vi.fn()} onViewChange={vi.fn()} view="keys" />)
+    })
 
     expect(await screen.findByText('WidgetAI')).toBeTruthy()
   })
@@ -158,14 +168,18 @@ describe('ProvidersSettings', () => {
 
     // Typing narrows the list to matching providers only.
     const search = screen.getByPlaceholderText('Search providers…')
-    fireEvent.change(search, { target: { value: 'mid' } })
+    await act(async () => {
+      fireEvent.change(search, { target: { value: 'mid' } })
+    })
 
     await waitFor(() => expect(screen.queryByText('Acme')).toBeNull())
     expect(screen.getByText('Middle')).toBeTruthy()
     expect(screen.queryByText('Zebra')).toBeNull()
 
     // A non-matching query shows the empty-state copy.
-    fireEvent.change(search, { target: { value: 'nonesuch-xyz' } })
+    await act(async () => {
+      fireEvent.change(search, { target: { value: 'nonesuch-xyz' } })
+    })
     expect(await screen.findByText('No providers match your search.')).toBeTruthy()
   })
 })
diff --git a/apps/desktop/src/app/skills/index.test.tsx b/apps/desktop/src/app/skills/index.test.tsx
index fe3e39a72c76..f4057a4f2b88 100644
--- a/apps/desktop/src/app/skills/index.test.tsx
+++ b/apps/desktop/src/app/skills/index.test.tsx
@@ -1,6 +1,6 @@
 // @vitest-environment jsdom
 import { QueryClientProvider } from '@tanstack/react-query'
-import { cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { act, cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
 import { MemoryRouter } from 'react-router-dom'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
@@ -48,9 +48,11 @@ function toolset(overrides: Record<string, unknown> = {}) {
   }
 }
 
-function renderSkills() {
-  return import('./index').then(({ SkillsView }) =>
-    render(
+async function renderSkills() {
+  const { SkillsView } = await import('./index')
+  let result: ReturnType<typeof render>
+  await act(async () => {
+    result = render(
       // SkillsView reads skills/toolsets via useQuery, so it needs a provider.
       <QueryClientProvider client={queryClient}>
         <MemoryRouter initialEntries={['/skills?tab=toolsets']}>
@@ -58,7 +60,9 @@ function renderSkills() {
         </MemoryRouter>
       </QueryClientProvider>
     )
-  )
+  })
+
+  return result!
 }
 
 beforeEach(() => {
@@ -83,7 +87,9 @@ describe('SkillsView toolset management', () => {
     const sw = await screen.findByRole('switch', { name: 'Toggle Web Search toolset' })
     expect(sw.getAttribute('aria-checked')).toBe('true')
 
-    fireEvent.click(sw)
+    await act(async () => {
+      fireEvent.click(sw)
+    })
 
     await waitFor(() => expect(toggleToolset).toHaveBeenCalledWith('web', false))
   })
diff --git a/apps/desktop/src/components/gateway-connecting-overlay.test.tsx b/apps/desktop/src/components/gateway-connecting-overlay.test.tsx
index 0225e8cb22d0..1a4fcca270a7 100644
--- a/apps/desktop/src/components/gateway-connecting-overlay.test.tsx
+++ b/apps/desktop/src/components/gateway-connecting-overlay.test.tsx
@@ -1,4 +1,4 @@
-import { cleanup, render, screen } from '@testing-library/react'
+import { act, cleanup, render, screen } from '@testing-library/react'
 import { afterEach, beforeEach, describe, expect, it } from 'vitest'
 
 import { $desktopBoot } from '@/store/boot'
@@ -61,7 +61,7 @@ const isRecoveryShown = () =>
   Boolean(screen.queryByText(/use local gateway/i) || screen.queryByText(/retry/i) || screen.queryByText(/sign in/i))
 
 describe('connecting overlay vs recovery surface', () => {
-  it('hard initial-boot failure surfaces the recovery overlay (the working path)', () => {
+  it('hard initial-boot failure surfaces the recovery overlay (the working path)', async () => {
     // failDesktopBoot() ran: error set, gateway never opened.
     $desktopBoot.set({
       ...$desktopBoot.get(),
@@ -71,28 +71,35 @@ describe('connecting overlay vs recovery surface', () => {
     })
     setGatewayState('error')
 
-    render(
-      <>
-        <GatewayConnectingOverlay />
-        <BootFailureOverlay />
-      </>
-    )
+    await act(async () => {
+      render(
+        <>
+          <GatewayConnectingOverlay />
+          <BootFailureOverlay />
+        </>
+      )
+    })
 
     expect(isRecoveryShown()).toBe(true)
     // Connecting overlay bows out when boot.error is set.
     expect(isConnectingShown()).toBe(false)
   })
 
-  it('post-boot socket drops do not re-cover the app with the initial CONNECTING overlay', () => {
+  it('post-boot socket drops do not re-cover the app with the initial CONNECTING overlay', async () => {
     // 1. Initial boot succeeded: gateway opened, boot completed (no error).
     setGatewayState('open')
 
-    const { rerender } = render(
-      <>
-        <GatewayConnectingOverlay />
-        <BootFailureOverlay />
-      </>
-    )
+    let rerender!: (ui: React.ReactElement) => void
+    await act(async () => {
+      const result = render(
+        <>
+          <GatewayConnectingOverlay />
+          <BootFailureOverlay />
+        </>
+      )
+
+      rerender = result.rerender
+    })
 
     expect(isConnectingShown()).toBe(false)
 
@@ -100,12 +107,14 @@ describe('connecting overlay vs recovery surface', () => {
     //    bootCompleted is true, so useGatewayBoot routes this through
     //    scheduleReconnect() — boot.error stays NULL.
     setGatewayState('closed')
-    rerender(
-      <>
-        <GatewayConnectingOverlay />
-        <BootFailureOverlay />
-      </>
-    )
+    await act(async () => {
+      rerender!(
+        <>
+          <GatewayConnectingOverlay />
+          <BootFailureOverlay />
+        </>
+      )
+    })
 
     // The initial-boot connecting overlay stays out of the way, so settings and
     // the composer remain reachable during the reconnect loop.
@@ -116,12 +125,14 @@ describe('connecting overlay vs recovery surface', () => {
     //    → error → closed. Until the escalation path sets boot.error, the app
     //    remains usable instead of modal-blocked.
     setGatewayState('error')
-    rerender(
-      <>
-        <GatewayConnectingOverlay />
-        <BootFailureOverlay />
-      </>
-    )
+    await act(async () => {
+      rerender!(
+        <>
+          <GatewayConnectingOverlay />
+          <BootFailureOverlay />
+        </>
+      )
+    })
     expect($desktopBoot.get().error).toBeNull()
     expect(isConnectingShown()).toBe(false)
     expect(isRecoveryShown()).toBe(false)
@@ -156,7 +167,7 @@ describe('connecting overlay vs recovery surface', () => {
     expect(isRecoveryShown()).toBe(false)
   })
 
-  it('FIX: once the prolonged reconnect raises a recoverable boot error, the recovery overlay takes over', () => {
+  it('FIX: once the prolonged reconnect raises a recoverable boot error, the recovery overlay takes over', async () => {
     // Mirrors what useGatewayBoot.scheduleReconnect() now does after ~45s of
     // failed post-boot reconnects: it calls failDesktopBoot(), flipping the UI
     // from the dead-end CONNECTING overlay to the recovery surface.
@@ -168,12 +179,14 @@ describe('connecting overlay vs recovery surface', () => {
       visible: true
     })
 
-    render(
-      <>
-        <GatewayConnectingOverlay />
-        <BootFailureOverlay />
-      </>
-    )
+    await act(async () => {
+      render(
+        <>
+          <GatewayConnectingOverlay />
+          <BootFailureOverlay />
+        </>
+      )
+    })
 
     // Escape hatch is now reachable; the connecting overlay bows out.
     expect(isRecoveryShown()).toBe(true)
diff --git a/apps/desktop/vitest.config.ts b/apps/desktop/vitest.config.ts
index 7ec1b7f80949..4bdc3793fa53 100644
--- a/apps/desktop/vitest.config.ts
+++ b/apps/desktop/vitest.config.ts
@@ -11,6 +11,7 @@ export default defineConfig({
   },
   test: {
     environment: "jsdom",
+    setupFiles: ["./vitest.setup.ts"],
     include: ["src/**/*.test.{ts,tsx}"],
     globals: true
   },
diff --git a/apps/desktop/vitest.setup.ts b/apps/desktop/vitest.setup.ts
new file mode 100644
index 000000000000..a671ac3ae971
--- /dev/null
+++ b/apps/desktop/vitest.setup.ts
@@ -0,0 +1,6 @@
+import '@testing-library/react'
+
+// React 19 + Testing Library 16: opt into the act environment so render(),
+// fireEvent(), and findBy* queries automatically flush state updates without
+// spurious "not wrapped in act(...)" warnings.
+;(globalThis as any).IS_REACT_ACT_ENVIRONMENT = true