diff --git a/relay/test/setup.ts b/relay/test/setup.ts
new file mode 100644
index 0000000..5338f7e
--- /dev/null
+++ b/relay/test/setup.ts
@@ -0,0 +1,18 @@
+// The hub logs one `{"evt":"channel_closed",...}` JSON line per retired
+// client, on purpose: it is the per-channel counter feed for Workers Logs
+// (src/hub.ts, retireClient). Under vitest that purpose does not exist, and
+// the suites retire enough clients to bury a CI log in seventy-odd of them —
+// so the line is dropped here, at the printing edge, and nowhere else.
+//
+// Only this line, by its prefix: anything else the Worker says still prints,
+// because an unexpected log in a test run is signal. And the test that proves
+// the counters ("... logs the counters", test/hub.test.ts) keeps working
+// unchanged: its vi.spyOn(console, 'log') wraps this filter, so it records
+// the call and its arguments whether or not anything reaches the terminal.
+
+const passThrough = console.log.bind(console)
+
+console.log = (...args: unknown[]) => {
+  if (typeof args[0] === 'string' && args[0].startsWith('{"evt":"channel_closed"')) return
+  passThrough(...args)
+}
diff --git a/relay/vitest.config.ts b/relay/vitest.config.ts
index 8aba76b..e1816f9 100644
--- a/relay/vitest.config.ts
+++ b/relay/vitest.config.ts
@@ -43,5 +43,10 @@ export default defineConfig({
       },
     }),
   ],
-  test: { include: ['test/**/*.test.ts'] },
+  test: {
+    include: ['test/**/*.test.ts'],
+    // Drops the hub's per-channel Workers Logs line from test output — the
+    // line itself is deliberate production logging. See test/setup.ts.
+    setupFiles: ['test/setup.ts'],
+  },
 })
diff --git a/web/src/components/app-shell.test.tsx b/web/src/components/app-shell.test.tsx
index a80d3e3..14cdc42 100644
--- a/web/src/components/app-shell.test.tsx
+++ b/web/src/components/app-shell.test.tsx
@@ -1,5 +1,5 @@
 import { afterEach, describe, expect, it } from 'vitest'
-import { screen, waitFor, within } from '@testing-library/react'
+import { act, screen, waitFor, within } from '@testing-library/react'
 import userEvent from '@testing-library/user-event'
 import { FlueClientContext } from '@/client/provider'
 import { renderWithRouter } from '@/testing/render'
@@ -186,8 +186,12 @@ describe('AppShell', () => {
     // state for a line nobody is waiting on.
     expect(screen.queryByText(/^flue /)).toBeNull()
 
-    last().open()
-    last().emitControl({ type: 'welcome', daemonId: 'local', host: 'macbook', ver: '0.4.1' })
+    // FakeSocket delivers synchronously, so the welcome's setState lands right
+    // here — inside act, or as an act warning for every listening component.
+    act(() => {
+      last().open()
+      last().emitControl({ type: 'welcome', daemonId: 'local', host: 'macbook', ver: '0.4.1' })
+    })
 
     const line = await screen.findByText('flue 0.4.1')
     // The daemon's releases, not a tag assembled from the string above — a
@@ -199,7 +203,9 @@ describe('AppShell', () => {
 
     // And it follows a reconnect, since a welcome is a claim about the daemon
     // and the daemon may have been restarted into a new build under the tab.
-    last().emitControl({ type: 'welcome', daemonId: 'local', host: 'macbook', ver: '0.5.0' })
+    act(() => {
+      last().emitControl({ type: 'welcome', daemonId: 'local', host: 'macbook', ver: '0.5.0' })
+    })
     expect(await screen.findByText('flue 0.5.0')).toBeTruthy()
   })
 
diff --git a/web/src/components/update-notice.test.tsx b/web/src/components/update-notice.test.tsx
index 18d4eb3..0491f0d 100644
--- a/web/src/components/update-notice.test.tsx
+++ b/web/src/components/update-notice.test.tsx
@@ -1,4 +1,4 @@
-import { render, screen, waitFor } from '@testing-library/react'
+import { act, render, screen, waitFor } from '@testing-library/react'
 import userEvent from '@testing-library/user-event'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 
@@ -63,8 +63,12 @@ function mount() {
       <UpdateNotice />
     </FlueClientContext.Provider>,
   )
-  last().open()
-  last().emitControl({ type: 'welcome', daemonId: 'local', host: 'macbook', ver: '0.4.1' })
+  // FakeSocket delivers synchronously, so the welcome's setState lands right
+  // here — inside act, or as an act warning from every test in the file.
+  act(() => {
+    last().open()
+    last().emitControl({ type: 'welcome', daemonId: 'local', host: 'macbook', ver: '0.4.1' })
+  })
   return view
 }
 
diff --git a/web/src/router.test.tsx b/web/src/router.test.tsx
index 64e2cc3..53aa3b4 100644
--- a/web/src/router.test.tsx
+++ b/web/src/router.test.tsx
@@ -32,11 +32,18 @@ async function renderAt(path: string) {
   const router = createFlueRouter()
   await router.load()
   const { client, sockets } = fakeClient()
-  const view = render(
-    <FlueClientProvider client={client}>
-      <RouterProvider router={router} />
-    </FlueClientProvider>,
-  )
+  // Async act, not a bare render: mounting RouterProvider re-runs
+  // router.load() from Transitioner's mount effect, and its continuations
+  // update the router stores a microtask after RTL's synchronous act exits —
+  // an act warning per mounted Match on a runner slow enough to print them.
+  let view!: ReturnType<typeof render>
+  await act(async () => {
+    view = render(
+      <FlueClientProvider client={client}>
+        <RouterProvider router={router} />
+      </FlueClientProvider>,
+    )
+  })
   return { ...view, client, sockets }
 }
 
@@ -56,11 +63,15 @@ async function renderFleet(path: string) {
     { id: 'local', name: '', client: local.client },
     { id: 'attic-pi', name: 'Attic Pi', client: attic.client },
   ])
-  const view = render(
-    <FleetProvider fleet={fleet}>
-      <RouterProvider router={router} />
-    </FleetProvider>,
-  )
+  // The same async act as renderAt, for the same post-mount load.
+  let view!: ReturnType<typeof render>
+  await act(async () => {
+    view = render(
+      <FleetProvider fleet={fleet}>
+        <RouterProvider router={router} />
+      </FleetProvider>,
+    )
+  })
   return { ...view, local, attic }
 }
 
@@ -74,7 +85,12 @@ async function renderPicker(path: string) {
   window.history.replaceState(null, '', path)
   const router = createFlueRouter({ picker: true })
   await router.load()
-  return render(<RouterProvider router={router} />)
+  // The same async act as renderAt, for the same post-mount load.
+  let view!: ReturnType<typeof render>
+  await act(async () => {
+    view = render(<RouterProvider router={router} />)
+  })
+  return view
 }
 
 /**
@@ -104,7 +120,10 @@ async function renderBare(path: string, picker = false): Promise<string[]> {
   window.history.replaceState(null, '', path)
   const router = createFlueRouter({ picker })
   await router.load()
-  render(<RouterProvider router={router} />)
+  // The same async act as renderAt, for the same post-mount load.
+  await act(async () => {
+    render(<RouterProvider router={router} />)
+  })
   return urls
 }
 
@@ -360,11 +379,16 @@ describe('createFlueRouter', () => {
       [{ id: 'local', name: '', client: local.client }],
       () => Promise.resolve([{ id: 'attic-pi', name: 'Attic Pi', client: attic.client }]),
     )
-    const { container } = render(
-      <FleetProvider fleet={fleet}>
-        <RouterProvider router={router} />
-      </FleetProvider>,
-    )
+    // The same async act as renderAt, for the same post-mount load. The fleet
+    // has not been welcomed yet, so nothing here settles the adoption early.
+    let container!: HTMLElement
+    await act(async () => {
+      container = render(
+        <FleetProvider fleet={fleet}>
+          <RouterProvider router={router} />
+        </FleetProvider>,
+      ).container
+    })
 
     // Before the welcome, not paired is all this browser can truthfully say.
     expect(screen.getByRole('status').textContent).toContain('Machine not paired on this browser')
diff --git a/web/src/routes/pair.test.tsx b/web/src/routes/pair.test.tsx
index 642a63c..ec2d4cb 100644
--- a/web/src/routes/pair.test.tsx
+++ b/web/src/routes/pair.test.tsx
@@ -1,4 +1,4 @@
-import { render, screen, waitFor } from '@testing-library/react'
+import { act, render, screen, waitFor } from '@testing-library/react'
 import userEvent from '@testing-library/user-event'
 import { RouterProvider } from '@tanstack/react-router'
 import { IDBFactory } from 'fake-indexeddb'
@@ -79,7 +79,15 @@ async function renderPair(search = '') {
   window.history.replaceState(null, '', `/pair${search}`)
   const router = createFlueRouter()
   await router.load()
-  return render(<RouterProvider router={router} />)
+  // Async act, because mounting RouterProvider re-runs router.load() from
+  // Transitioner's mount effect, and its continuations update the router
+  // stores a microtask after RTL's synchronous act exits — an act warning per
+  // mounted Match on a runner slow enough to print them.
+  let view!: ReturnType<typeof render>
+  await act(async () => {
+    view = render(<RouterProvider router={router} />)
+  })
+  return view
 }
 
 const pairButton = () => screen.getByRole('button', { name: 'Pair' })
@@ -468,7 +476,12 @@ async function renderRelayPair(search = '') {
   })
   const router = createFlueRouter()
   await router.load()
-  return render(<RouterProvider router={router} />)
+  // The same async act as renderPair, for the same post-mount load.
+  let view!: ReturnType<typeof render>
+  await act(async () => {
+    view = render(<RouterProvider router={router} />)
+  })
+  return view
 }
 
 describe('PairRoute on a relay origin', () => {
diff --git a/web/src/routes/sessions.test.tsx b/web/src/routes/sessions.test.tsx
index a2b4eb3..a6138ae 100644
--- a/web/src/routes/sessions.test.tsx
+++ b/web/src/routes/sessions.test.tsx
@@ -97,13 +97,21 @@ async function mountSessions({ open = true, strict = false, solo = false } = {})
   // tree and every query misses.
   await router.load()
 
-  const view = render(
-    <SidebarProvider>
-      <FleetProvider fleet={fleet}>
-        <RouterProvider router={router as never} />
-      </FleetProvider>
-    </SidebarProvider>,
-  )
+  // Async act, because mounting RouterProvider re-runs router.load() from
+  // Transitioner's mount effect, and its continuations update the router
+  // stores a microtask after RTL's synchronous act exits — an act warning per
+  // mounted Match on a runner slow enough to print them. No socket is open
+  // yet, so nothing else can settle early in here.
+  let view!: ReturnType<typeof render>
+  await act(async () => {
+    view = render(
+      <SidebarProvider>
+        <FleetProvider fleet={fleet}>
+          <RouterProvider router={router as never} />
+        </FleetProvider>
+      </SidebarProvider>,
+    )
+  })
   const sock = local.sockets[0]!
   if (open) act(() => sock.open())
 
@@ -629,7 +637,11 @@ describe('SessionsRoute', () => {
       // `spawn` carries no metadata, so the tag can only be applied once the
       // session exists — which is the `attached` that answers it.
       expect(sock.ofType('update')).toEqual([])
-      act(() => sock.emitControl(attached({ ref: 3, id: 'fresh1', reqId: 1 })))
+      // Async, unlike the emits above: this `attached` answers a spawn, so it
+      // also starts the navigation to the new session, and the router's
+      // continuations land a microtask after a synchronous act exits. The
+      // update frame itself is sent synchronously, before the screen changes.
+      await act(async () => sock.emitControl(attached({ ref: 3, id: 'fresh1', reqId: 1 })))
 
       expect(sock.ofType('update')).toEqual([{ type: 'update', id: 'fresh1', tags: ['api'] }])
     })
diff --git a/web/src/testing/render.tsx b/web/src/testing/render.tsx
index 94e84fb..8c5eaec 100644
--- a/web/src/testing/render.tsx
+++ b/web/src/testing/render.tsx
@@ -1,5 +1,5 @@
 import type { ReactNode } from 'react'
-import { render } from '@testing-library/react'
+import { act, render } from '@testing-library/react'
 import {
   createMemoryHistory,
   createRootRoute,
@@ -52,12 +52,19 @@ export async function renderWithRouter(ui: ReactNode, initialPath = '/sessions')
   // empty tree and every query in the test misses. Loading first is what
   // makes the render synchronous, which is why this helper is async.
   await router.load()
-  return {
-    router,
-    ...render(
+  // The async act matters even though the router is already loaded: mounting
+  // RouterProvider runs Transitioner's mount effect, which calls router.load()
+  // again, and that call's continuations update the router stores a microtask
+  // after RTL's own synchronous act has exited. Flushing them inside act here
+  // is what keeps every consumer of this helper from tripping "not wrapped in
+  // act(...)" warnings — one per mounted Match — on the first update.
+  let view!: ReturnType<typeof render>
+  await act(async () => {
+    view = render(
       <SidebarProvider>
         <RouterProvider router={router as never} />
       </SidebarProvider>,
-    ),
-  }
+    )
+  })
+  return { router, ...view }
 }
diff --git a/web/src/testing/test-setup.ts b/web/src/testing/test-setup.ts
index 231b84d..718a632 100644
--- a/web/src/testing/test-setup.ts
+++ b/web/src/testing/test-setup.ts
@@ -46,6 +46,26 @@ if (globalThis.Element && !Element.prototype.scrollIntoView) {
   Element.prototype.scrollIntoView = function scrollIntoView() {}
 }
 
+// window.scrollTo exists in jsdom, but as a stub that logs "Not implemented:
+// Window's scrollTo() method" to stderr every time focus mode or a Radix
+// primitive calls it — sixty-odd lines per full run, none of them news. The
+// no-op is the same honest stub as scrollIntoView above: nothing in jsdom
+// scrolls. Overwritten unconditionally, because unlike the globals above the
+// jsdom version is present — presence is the problem.
+if (globalThis.window) {
+  window.scrollTo = () => {}
+}
+
+// getContext is the same story: jsdom ships the method, and without the
+// `canvas` package it logs "Not implemented" and returns null. Returning the
+// null directly keeps the behaviour every caller already handles — the QR
+// code on Devices falls back to a link when the context is missing, and a
+// test pins exactly that — while dropping the log line.
+if (globalThis.HTMLCanvasElement) {
+  HTMLCanvasElement.prototype.getContext = (() =>
+    null) as typeof HTMLCanvasElement.prototype.getContext
+}
+
 /*
  * Fail a test that logged one of flue's own swallowed errors.
  *