[Feature] Quick audio menu (#4275)

* Give the microphone level its own observable
* Add a microphone level meter
* Show speakers and microphones in the quick audio menu
* Wire speaker selection through the call footer
* Add stories for the meter and the device menu
* Add end-to-end specs for the quick audio menu
* Keep the footer while a menu opened from it is open
* Use the shared audio capture stub in the lobby test
---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

locales/en/app.json

@@ -163,6 +163,12 @@
   "login_auth_links_prompt": "Not registered yet?",
   "login_subheading": "To continue to Element",
   "login_title": "Login",
+  "microphone_level": {
+    "label": "Microphone level",
+    "no_device": "No microphone found. Connect one, then try again.",
+    "permission_denied": "Microphone access is blocked. Allow it, then try again.",
+    "value": "{{level}} of {{max}}"
+  },
   "microphone_off": "Microphone off",
   "microphone_on": "Microphone on",
   "mute_microphone_button_label": "Mute microphone",
@@ -215,11 +221,14 @@
       "activating": "Activating…",
       "camera": "Camera",
       "camera_numbered": "Camera {{n}}",
+      "camera_source": "Camera Source",
       "change_device_button": "Change audio device",
       "default": "Default",
       "default_named": "Default <2>({{name}})</2>",
+      "default_named_plain": "Default ({{name}})",
       "handset": "Handset",
       "loudspeaker": "Loudspeaker",
+      "mic_source": "Mic Source",
       "microphone": "Microphone",
       "microphone_numbered": "Microphone {{n}}",
       "speaker": "Speaker",

playwright/audio-menu.spec.ts

@@ -0,0 +1,229 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { expect, test, type Locator, type Page } from "@playwright/test";
+
+import { SpaHelpers } from "./spa-helpers.ts";
+import { installFakeDevices } from "./utils/fake-devices.ts";
+
+test.describe("the quick audio menu", () => {
+  test("lists speakers and microphones with a live level meter", async ({
+    page,
+  }) => {
+    await installFakeDevices(page, { microphones: 3, speakers: 3 });
+    await joinACall(page, "Menu user", "Audio menu");
+    await openAudioMenu(page);
+
+    await expect(page.getByRole("group", { name: "Speaker" })).toBeVisible();
+    await expect(page.getByRole("group", { name: "Microphone" })).toBeVisible();
+    // By name, not count: the browser adds its own fake output and a Default.
+    for (const n of [1, 2, 3])
+      await expect(
+        page
+          .getByRole("group", { name: "Speaker" })
+          .getByRole("menuitemradio", { name: `Fake Speaker ${n}` }),
+      ).toBeVisible();
+
+    await expect(
+      page.getByRole("menuitemradio", { checked: true }),
+    ).toHaveCount(2);
+    const meter = page.getByRole("meter", { name: "Microphone level" });
+    await expect(meter).toBeVisible();
+    await expect(meter).toHaveAttribute("aria-valuenow", /\d+/);
+    await expect(meter).toHaveAttribute("aria-valuetext", /\d+ of \d+/);
+
+    // Both browsers here can route audio; the platform that can't is a unit check.
+    await expect(
+      page
+        .getByRole("group", { name: "Speaker" })
+        .getByRole("menuitemradio")
+        .first(),
+    ).toHaveAttribute("aria-disabled", "false");
+  });
+
+  test("moves the microphone and the speaker without disturbing the call", async ({
+    browser,
+  }) => {
+    // Two browsers and a real call.
+    test.slow();
+    const hostContext = await browser.newContext({ reducedMotion: "reduce" });
+    const host = await hostContext.newPage();
+    await installFakeDevices(host, { microphones: 3, speakers: 3 });
+    await joinACall(host, "Host", "Device switch");
+
+    const inviteLink = await SpaHelpers.getCallInviteLink(host);
+    const guestContext = await browser.newContext({ reducedMotion: "reduce" });
+    const guest = await guestContext.newPage();
+    await SpaHelpers.joinCallFromInviteLink(guest, inviteLink, "Guest");
+    await SpaHelpers.expectVideoTilesCount(guest, 2);
+
+    await openAudioMenu(host);
+    await selectDevice(host, "Microphone", "Fake Microphone 2");
+    await openAudioMenu(host);
+    await selectDevice(host, "Speaker", "Fake Speaker 2");
+
+    // Not a rejoin: neither side drops, and the guest still has both tiles.
+    await expect(
+      host.getByRole("dialog", { name: "Reconnecting…" }),
+    ).not.toBeVisible();
+    await expect(
+      guest.getByRole("dialog", { name: "Reconnecting…" }),
+    ).not.toBeVisible();
+    await SpaHelpers.expectVideoTilesCount(guest, 2);
+    await expect(guest.getByText("Waiting for media...")).not.toBeVisible();
+
+    await hostContext.close();
+    await guestContext.close();
+  });
+
+  test("keeps the meter moving while muted, and sends nothing", async ({
+    browser,
+  }) => {
+    // Two browsers and a real call.
+    test.slow();
+    const hostContext = await browser.newContext({ reducedMotion: "reduce" });
+    const host = await hostContext.newPage();
+    await installFakeDevices(host);
+    await joinACall(host, "Muted host", "Muted meter");
+
+    const inviteLink = await SpaHelpers.getCallInviteLink(host);
+    const guestContext = await browser.newContext({ reducedMotion: "reduce" });
+    const guest = await guestContext.newPage();
+    await SpaHelpers.joinCallFromInviteLink(guest, inviteLink, "Listener");
+    await SpaHelpers.expectVideoTilesCount(guest, 2);
+
+    const mute = host.getByTestId("incall_mute");
+    await mute.click();
+    await expect(mute).toHaveAttribute("aria-checked", "false");
+    await openAudioMenu(host);
+
+    const meter = host.getByRole("meter", { name: "Microphone level" });
+    await expect(meter).toBeVisible();
+    // By test id: the modal menu hides the rest of the call from the a11y tree.
+    await expect(mute).toHaveAttribute("aria-checked", "false");
+    await expect(mute).toBeVisible();
+    // And the guest is shown the mute.
+    await expect(
+      guest.getByTestId("videoTile").filter({ hasText: "Muted host" }),
+    ).toBeVisible();
+
+    await hostContext.close();
+    await guestContext.close();
+  });
+
+  test("keeps the meter at the foot of the list while it scrolls", async ({
+    page,
+  }) => {
+    await installFakeDevices(page, { microphones: 20, speakers: 4 });
+    await joinACall(page, "Scroller", "Long device list");
+    await openAudioMenu(page);
+
+    const meter = page.getByRole("meter", { name: "Microphone level" });
+    await expect(meter).toBeVisible();
+
+    // Scrolled so the microphones start at the top: only there does a pinned
+    // meter differ from one that is simply last.
+    const list = page.locator("[role='menu'] div[role='none']").first();
+    await list.evaluate((element) => {
+      const group = element.querySelector("[role='group'][aria-label*='icro']");
+      element.scrollTop +=
+        group!.getBoundingClientRect().top -
+        element.getBoundingClientRect().top;
+    });
+
+    await expect(meter).toBeInViewport();
+    await expectPinnedInside(meter, list);
+    await expect(
+      page.getByRole("menuitemradio", { name: "Fake Microphone 20" }),
+    ).toBeVisible();
+  });
+
+  test("shows the focus ring only when the keyboard moved the focus", async ({
+    page,
+    browserName,
+  }) => {
+    test.skip(
+      browserName === "firefox",
+      "Headless Firefox does not deliver synthetic key presses reliably; see reconnect.spec.ts",
+    );
+    await installFakeDevices(page);
+    await joinACall(page, "Keyboard user", "Focus ring");
+    await openAudioMenu(page);
+
+    const first = page.getByRole("menuitemradio").first();
+    // Opened by pointer: no ring, though Radix has moved focus into the menu.
+    await expect.poll(async () => outlineWidth(first)).toBe(0);
+
+    await page.keyboard.press("ArrowDown");
+    const focused = page.locator("[role='menuitemradio']:focus");
+    await expect.poll(async () => outlineWidth(focused)).toBeGreaterThan(0);
+
+    // And the pointer takes it away again.
+    await first.hover();
+    await expect.poll(async () => outlineWidth(focused)).toBe(0);
+  });
+});
+
+/** Creates a call and joins it, leaving the page in the call. */
+async function joinACall(
+  page: Page,
+  userName: string,
+  callName: string,
+): Promise<void> {
+  await page.goto("/");
+  await SpaHelpers.createCall(page, userName, callName, true);
+  await expect(page.getByTestId("name_tag")).toContainText(userName);
+  // The media controls stay disabled until devices have enumerated.
+  await expect(page.getByTestId("incall_mute")).toBeEnabled({
+    timeout: 10_000,
+  });
+}
+
+async function openAudioMenu(page: Page): Promise<void> {
+  await page.getByRole("button", { name: "Microphone" }).click();
+  await expect(page.getByRole("menu")).toBeVisible();
+}
+
+async function selectDevice(
+  page: Page,
+  section: "Speaker" | "Microphone",
+  name: string,
+): Promise<void> {
+  const item = page
+    .getByRole("group", { name: section })
+    .getByRole("menuitemradio", { name });
+  await item.click();
+  // Selecting doesn't close the menu, so dismiss it.
+  await page.keyboard.press("Escape");
+  await expect(page.getByRole("menu")).not.toBeVisible();
+}
+
+/** Asserts the meter sits within the scrollport and inside the menu's frame. */
+async function expectPinnedInside(
+  meter: Locator,
+  list: Locator,
+): Promise<void> {
+  const meterBox = (await meter.boundingBox())!;
+  const listBox = (await list.boundingBox())!;
+  const frame = (await meter.page().getByRole("menu").boundingBox())!;
+
+  expect(meterBox.y + meterBox.height).toBeLessThanOrEqual(
+    listBox.y + listBox.height + 1,
+  );
+  expect(meterBox.y).toBeGreaterThanOrEqual(listBox.y - 1);
+  expect(meterBox.x).toBeGreaterThan(frame.x);
+  expect(meterBox.x + meterBox.width).toBeLessThan(frame.x + frame.width);
+}
+
+/** Painted outline width, in px. */
+async function outlineWidth(item: Locator): Promise<number> {
+  if ((await item.count()) === 0) return 0;
+  return item.first().evaluate((element) => {
+    const { outlineStyle, outlineWidth } = getComputedStyle(element);
+    return outlineStyle === "none" ? 0 : Number.parseFloat(outlineWidth) || 0;
+  });
+}

playwright/component/audio-menu.spec.ts

@@ -0,0 +1,135 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { expect, type Locator, type Page, test } from "@playwright/test";
+
+import { createUserAndRoom, resizeContainer, startHarness } from "./harness.ts";
+import { installFakeDevices } from "../utils/fake-devices.ts";
+
+/**
+ * The device menu with Element Call as a component in a host page, where the
+ * portalled menu must be sized against the call, not the window. Driven from
+ * the lobby: it builds the same menu, without two connections' worth of flake.
+ */
+
+// Sign-in, crypto setup and sync happen twice before anything shows.
+test.describe.configure({ timeout: 180_000 });
+
+test("sizes the device list against the call, not the window", async ({
+  page,
+}) => {
+  await installFakeDevices(page, { microphones: 20, speakers: 4 });
+  const { username, roomId } = await createUserAndRoom("menusize");
+  const panes = await startHarness(page, username, roomId);
+  const pane = panes.first();
+
+  // A short call in a much taller page.
+  const container = pane.getByTestId("call-container");
+  await resizeContainer(container, { width: 900, height: 400 });
+  await expect(pane.getByTestId("lobby_joinCall")).toBeVisible({
+    timeout: 60_000,
+  });
+
+  const list = await openDeviceList(page, pane);
+  const callHeight = (await container.boundingBox())!.height;
+  const windowHeight = page.viewportSize()!.height;
+  const listHeight = (await list.boundingBox())!.height;
+
+  expect(callHeight).toBeLessThan(windowHeight * 0.75);
+  expect(listHeight).toBeLessThanOrEqual(callHeight);
+  expect(listHeight).toBeLessThan(windowHeight * 0.6);
+});
+
+test("follows the call area when the host resizes it", async ({ page }) => {
+  await installFakeDevices(page, { microphones: 20, speakers: 4 });
+  const { username, roomId } = await createUserAndRoom("menuresize");
+  const panes = await startHarness(page, username, roomId);
+  const pane = panes.first();
+
+  const container = pane.getByTestId("call-container");
+  await resizeContainer(container, { width: 900, height: 360 });
+  await expect(pane.getByTestId("lobby_joinCall")).toBeVisible({
+    timeout: 60_000,
+  });
+
+  const list = await openDeviceList(page, pane);
+  const whenShort = (await list.boundingBox())!.height;
+
+  // The host grows the call while the menu is open.
+  await resizeContainer(container, { width: 900, height: 700 });
+  await expect
+    .poll(async () => (await list.boundingBox())!.height)
+    .toBeGreaterThan(whenShort);
+});
+
+test("keeps every device reachable in a small container", async ({ page }) => {
+  await installFakeDevices(page, { microphones: 20, speakers: 4 });
+  const { username, roomId } = await createUserAndRoom("menureach");
+  const panes = await startHarness(page, username, roomId);
+  const pane = panes.first();
+
+  const container = pane.getByTestId("call-container");
+  await resizeContainer(container, { width: 400, height: 360 });
+  await expect(pane.getByTestId("lobby_joinCall")).toBeVisible({
+    timeout: 60_000,
+  });
+
+  const list = await openDeviceList(page, pane);
+  // More devices than fit, so the list must scroll.
+  expect(await list.evaluate((el) => el.scrollHeight > el.clientHeight)).toBe(
+    true,
+  );
+
+  const last = page.getByRole("menuitemradio", { name: "Fake Microphone 20" });
+  await last.scrollIntoViewIfNeeded();
+  await expect(last).toBeInViewport();
+  // Reachable means clickable: the menu may be drawn outside the call area.
+  await last.click();
+  await expect(last).toHaveAttribute("aria-checked", "true");
+});
+
+test("tracks the focus source of its own call, not the page", async ({
+  page,
+}) => {
+  await installFakeDevices(page);
+  const { username, roomId } = await createUserAndRoom("menufocus");
+  const panes = await startHarness(page, username, roomId);
+  const pane = panes.first();
+  const other = panes.nth(1);
+
+  await expect(pane.getByTestId("lobby_joinCall")).toBeVisible({
+    timeout: 60_000,
+  });
+  await openDeviceList(page, pane);
+  const menu = page.getByRole("menu");
+
+  // Asserted on the attribute: the component build's scoped stylesheet doesn't
+  // reach the portalled menu, so its ring can't be read here.
+  await expect(menu).toHaveAttribute("data-focus-source", "pointer");
+
+  // A key pressed in the other call says nothing about this menu.
+  await other.evaluate((element) =>
+    element.dispatchEvent(
+      new KeyboardEvent("keydown", { key: "ArrowDown", bubbles: true }),
+    ),
+  );
+  await expect(menu).toHaveAttribute("data-focus-source", "pointer");
+
+  await page.keyboard.press("ArrowDown");
+  await expect(menu).toHaveAttribute("data-focus-source", "keyboard");
+});
+
+/** Opens a component's microphone menu and returns its device list. */
+async function openDeviceList(page: Page, pane: Locator): Promise<Locator> {
+  await pane
+    .getByRole("button", { name: "Microphone" })
+    .click({ timeout: 60_000 });
+  await expect(page.getByRole("menu")).toBeVisible();
+  const list = page.locator("[role='menu'] div[role='none']").first();
+  await expect(list).toBeVisible();
+  return list;
+}

playwright/utils/fake-devices.ts

@@ -0,0 +1,85 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { type Page } from "@playwright/test";
+
+/**
+ * Adds synthetic devices beside the browser's one fake microphone and speaker,
+ * so the menu has a choice to show. They share one capture and `setSinkId` is
+ * accepted but not honoured: routing still needs hardware and a manual check.
+ * Call before the page navigates.
+ */
+export async function installFakeDevices(
+  page: Page,
+  { microphones = 2, speakers = 2 } = {},
+): Promise<void> {
+  await page.addInitScript(
+    ({ microphones, speakers }) => {
+      const synthetic = (
+        kind: MediaDeviceKind,
+        count: number,
+        name: string,
+      ): MediaDeviceInfo[] =>
+        Array.from({ length: count }, (_, i) => {
+          const info = {
+            deviceId: `${kind}-${i + 1}`,
+            groupId: `${kind}-group-${i + 1}`,
+            kind,
+            label: `${name} ${i + 1}`,
+          };
+          return { ...info, toJSON: () => info } as MediaDeviceInfo;
+        });
+      const ids = new Set(
+        [
+          ...synthetic("audioinput", microphones, ""),
+          ...synthetic("audiooutput", speakers, ""),
+        ].map((d) => d.deviceId),
+      );
+
+      const devices = navigator.mediaDevices;
+      const enumerate = devices.enumerateDevices.bind(devices);
+      devices.enumerateDevices = async (): Promise<MediaDeviceInfo[]> => [
+        ...(await enumerate()),
+        ...synthetic("audioinput", microphones, "Fake Microphone"),
+        ...synthetic("audiooutput", speakers, "Fake Speaker"),
+      ];
+
+      // Our ids name no hardware, so drop the exact-device constraint.
+      const getUserMedia = devices.getUserMedia.bind(devices);
+      devices.getUserMedia = async (
+        constraints?: MediaStreamConstraints,
+      ): Promise<MediaStream> => {
+        const audio = constraints?.audio;
+        if (typeof audio === "object") {
+          const requested = audio.deviceId;
+          const id =
+            typeof requested === "object" && requested !== null
+              ? ((requested as ConstrainDOMStringParameters).exact as string)
+              : (requested as string | undefined);
+          if (id !== undefined && ids.has(id))
+            return getUserMedia({ ...constraints, audio: true });
+        }
+        return getUserMedia(constraints);
+      };
+
+      // Accept routing to our ids on both media elements and the AudioContext,
+      // which the app also routes.
+      for (const proto of [
+        HTMLMediaElement.prototype,
+        AudioContext.prototype,
+      ]) {
+        const sink = proto as { setSinkId?: (id: string) => Promise<void> };
+        const setSinkId = sink.setSinkId;
+        if (setSinkId === undefined) continue;
+        sink.setSinkId = async function (id: string): Promise<void> {
+          if (!ids.has(id)) await setSinkId.call(this, id);
+        };
+      }
+    },
+    { microphones, speakers },
+  );
+}

src/components/CallFooter.module.css

@@ -43,7 +43,10 @@ Please see LICENSE in the repository root for full details.
   inset-inline: 0;
 }
 
-.footer.overlay:has(:focus-visible) {
+/* Keep the footer while it is in use: focus inside it, or a menu opened from
+   it. The menu is portalled out, so the trigger's aria-expanded tracks it. */
+.footer.overlay:has(:focus-visible),
+.footer.overlay:has([aria-expanded="true"]) {
   opacity: 1;
   pointer-events: initial;
 }

src/components/CallFooter.stories.tsx

@@ -13,6 +13,7 @@ import { Link } from "@vector-im/compound-web";
 import type { Meta, StoryObj } from "@storybook/react-vite";
 import { CallFooter, type FooterSnapshot } from "./CallFooter";
 import inCallViewStyles from "../room/InCallView.module.css";
+import styles from "./CallFooter.module.css";
 import { useStaticViewModel } from "../state/ViewModel";
 import { ReactionsSenderContext } from "../reactions/useReactionsSender";
 import { type ReactionOption } from "../reactions";
@@ -137,10 +138,13 @@ export const Default: Story = {
     debugTileLayout: false,
     tileStoreGeneration: undefined,
     audioOptions: [],
+    audioOutputOptions: [],
     videoOptions: [],
     selectedAudio: undefined,
+    selectedAudioOutput: undefined,
     selectedVideo: undefined,
     selectAudioButtonOption: undefined,
+    selectAudioOutputOption: undefined,
     selectVideoButtonOption: undefined,
   },
   parameters: {
@@ -158,15 +162,46 @@ export const WithAudioAndVideoOptions: Story = {
       { label: { type: "name", name: "Microphone 1" }, id: "1" },
       { label: { type: "name", name: "Microphone 2" }, id: "2" },
     ],
+    audioOutputOptions: [
+      { label: { type: "default", name: "Built-in Output" }, id: "default" },
+      { label: { type: "name", name: "Headset" }, id: "2" },
+    ],
     videoOptions: [
       { label: { type: "name", name: "Camera 1" }, id: "1" },
       { label: { type: "name", name: "Camera 2" }, id: "2" },
     ],
     selectedAudio: "2",
+    selectedAudioOutput: "default",
     selectedVideo: "1",
   },
 };
 
+export const StaysWhileAMenuIsOpen: Story = {
+  ...Default,
+  args: {
+    ...WithAudioAndVideoOptions.args,
+    // In a short window the footer overlays the call and hides itself.
+    asOverlay: true,
+    showFooter: true,
+  },
+  play: async ({ canvasElement }): Promise<void> => {
+    const footer = canvasElement.querySelector<HTMLElement>(
+      '[data-testid="footer-container"]',
+    )!;
+    await userEvent.click(
+      within(canvasElement).getByRole("button", { name: "Microphone" }),
+    );
+    await expect(document.body.querySelector('[role="menu"]')).not.toBeNull();
+
+    // The call hides the footer with this class.
+    footer.classList.add(styles.hidden);
+
+    // Read after the 0.15s fade, not mid-transition.
+    await new Promise((settled) => setTimeout(settled, 400));
+    await expect(getComputedStyle(footer).opacity).toBe("1");
+  },
+};
+
 export const AudioBusy: Story = {
   ...Default,
   args: {

src/components/CallFooter.tsx

@@ -99,11 +99,15 @@ export interface FooterState {
 
   /** Providing no options `[]` or `undefined` will imply that we dont have a audio fast switcher */
   audioOptions: MenuOptions[];
+  /** Output (speaker) devices. */
+  audioOutputOptions: MenuOptions[];
   /** Providing no options `[]` or `undefined` will imply that we dont have a audio fast switcher */
   videoOptions: MenuOptions[];
   selectedAudio: string | undefined;
+  selectedAudioOutput: string | undefined;
   selectedVideo: string | undefined;
   selectAudioButtonOption: ((deviceId: string) => void) | undefined;
+  selectAudioOutputOption: ((deviceId: string) => void) | undefined;
   selectVideoButtonOption: ((option: string) => void) | undefined;
 }
 
@@ -143,6 +147,9 @@ export const CallFooter: FC<FooterProps> = ({
   const audioOptions = useBehavior(vm.audioOptions$);
   const selectedAudio = useBehavior(vm.selectedAudio$);
   const selectAudioButtonOption = useBehavior(vm.selectAudioButtonOption$);
+  const audioOutputOptions = useBehavior(vm.audioOutputOptions$);
+  const selectedAudioOutput = useBehavior(vm.selectedAudioOutput$);
+  const selectAudioOutputOption = useBehavior(vm.selectAudioOutputOption$);
   const selectVideoButtonOption = useBehavior(vm.selectVideoButtonOption$);
   const toggleBlur = useBehavior(vm.toggleBlur$);
   const videoBlurEnabled = useBehavior(vm.videoBlurEnabled$);
@@ -168,7 +175,6 @@ export const CallFooter: FC<FooterProps> = ({
   if ((audioOptions?.length ?? 0) > 0) {
     buttons.push(
       <MediaMuteAndSwitchButton
-        title={"Mic Source"}
         key="audio"
         iconsAndLabels="audio"
         enabled={audioEnabled ?? false}
@@ -178,6 +184,9 @@ export const CallFooter: FC<FooterProps> = ({
         options={audioOptions}
         selectedOption={selectedAudio}
         onSelect={selectAudioButtonOption}
+        outputOptions={audioOutputOptions}
+        selectedOutputOption={selectedAudioOutput}
+        onSelectOutput={selectAudioOutputOption}
       />,
     );
   } else {
@@ -197,7 +206,6 @@ export const CallFooter: FC<FooterProps> = ({
   if ((videoOptions?.length ?? 0) > 0) {
     buttons.push(
       <MediaMuteAndSwitchButton
-        title={"Camera Source"}
         key="video"
         iconsAndLabels="video"
         enabled={videoEnabled ?? false}

src/components/CallFooterViewModel.test.ts

@@ -30,6 +30,11 @@ vi.mock("@livekit/track-processors", () => ({
   supportsBackgroundProcessors: (): boolean => false,
 }));
 
+const outputSelectionMock = vi.hoisted(() => vi.fn(() => true));
+vi.mock("livekit-client", () => ({
+  supportsAudioOutputSelection: (): boolean => outputSelectionMock(),
+}));
+
 /**
  * Returns the minimum set of CallViewModel fields required by
  * createCallFooterViewModel, with all other properties stubbed to
@@ -96,6 +101,65 @@ const twoMicsAndOneCamMediaDevices = mockMediaDevices({
 });
 
 describe("createCallFooterViewModel", () => {
+  describe("selectAudioOutputOption", () => {
+    function buildFooterVm(): ReturnType<typeof createCallFooterViewModel> {
+      platformMock.mockReturnValue("desktop");
+      return createCallFooterViewModel(
+        testScope(),
+        buildMinimalCallViewModel(gridLayout),
+        mockMuteStates(),
+        twoMicsAndOneCamMediaDevices,
+        /* reactionIdentifier */ undefined,
+        { showControls: true, header: HeaderStyle.Standard },
+      );
+    }
+
+    it("is withheld where the platform cannot route audio to a chosen device", () => {
+      outputSelectionMock.mockReturnValue(false);
+      expect(buildFooterVm().selectAudioOutputOption$.value).toBeUndefined();
+    });
+
+    it("is offered where the platform can route audio to a chosen device", () => {
+      outputSelectionMock.mockReturnValue(true);
+      expect(buildFooterVm().selectAudioOutputOption$.value).toBeDefined();
+    });
+  });
+
+  describe("audioOutputOptions", () => {
+    it("is an empty list, not absent, where the platform enumerates no outputs", () => {
+      platformMock.mockReturnValue("desktop");
+      outputSelectionMock.mockReturnValue(true);
+
+      const vm = createCallFooterViewModel(
+        testScope(),
+        buildMinimalCallViewModel(gridLayout),
+        mockMuteStates(),
+        mockMediaDevices({
+          audioInput: {
+            available$: constant(
+              new Map<string, DeviceLabel>([
+                ["mic1", { type: "name", name: "Microphone 1" }],
+              ]),
+            ),
+            selected$: constant(undefined),
+            select: vi.fn(),
+          },
+          // As Safari: no outputs listed.
+          audioOutput: {
+            available$: constant(new Map<string, DeviceLabel>()),
+            selected$: constant(undefined),
+            select: vi.fn(),
+          },
+        }),
+        /* reactionIdentifier */ undefined,
+        { showControls: true, header: HeaderStyle.Standard },
+      );
+
+      // Empty, not undefined: undefined would hide the section.
+      expect(vm.audioOutputOptions$.value).toEqual([]);
+    });
+  });
+
   describe("audioOptions and videoOptions", () => {
     function checkEmptyFor(platform: string, layout: Layout): void {
       platformMock.mockReturnValue(platform);

src/components/CallFooterViewModel.tsx

@@ -5,8 +5,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { combineLatest, map, switchMap } from "rxjs";
+import { combineLatest, map, type Observable, switchMap } from "rxjs";
 import { supportsBackgroundProcessors } from "@livekit/track-processors";
+import { supportsAudioOutputSelection } from "livekit-client";
 
 import { type CallViewModel } from "../state/CallViewModel/CallViewModel";
 import { type MenuOptions } from "./MediaMuteAndSwitchButton";
@@ -67,49 +68,50 @@ function buildDeviceBehaviors(
   | "audioOptions$"
   | "selectedAudio$"
   | "selectAudioButtonOption$"
+  | "audioOutputOptions$"
+  | "selectedAudioOutput$"
+  | "selectAudioOutputOption$"
   | "videoOptions$"
   | "selectedVideo$"
   | "selectVideoButtonOption$"
   | "toggleBlur$"
   | "videoBlurEnabled$"
 > {
-  return {
+  const options$ = (
-    audioOptions$: scope.behavior(
+    available$: Behavior<Map<string, MenuOptions["label"]>>,
-      disableSwitcher$.pipe(
+  ): Observable<MenuOptions[]> =>
-        switchMap((disable) =>
+    disableSwitcher$.pipe(
-          disable
+      switchMap((disable) =>
-            ? constant([] as MenuOptions[])
+        disable
-            : mediaDevices.audioInput.available$.pipe(
+          ? constant([] as MenuOptions[])
-                map((available) =>
+          : available$.pipe(
-                  [...available.entries()].map(([id, label]) => ({
+              map((available) =>
-                    id,
+                [...available.entries()].map(([id, label]) => ({ id, label })),
-                    label,
-                  })),
-                ),
               ),
-        ),
+            ),
       ),
-    ),
+    );
+
+  return {
+    audioOptions$: scope.behavior(options$(mediaDevices.audioInput.available$)),
     selectedAudio$: scope.behavior(
       mediaDevices.audioInput.selected$.pipe(map((s) => s?.id)),
     ),
     selectAudioButtonOption$: constant(mediaDevices.audioInput.select),
-    videoOptions$: scope.behavior(
+    audioOutputOptions$: scope.behavior(
-      disableSwitcher$.pipe(
+      options$(mediaDevices.audioOutput.available$),
-        switchMap((disable) =>
-          disable
-            ? constant([] as MenuOptions[])
-            : mediaDevices.videoInput.available$.pipe(
-                map((available) =>
-                  [...available.entries()].map(([id, label]) => ({
-                    id,
-                    label,
-                  })),
-                ),
-              ),
-        ),
-      ),
     ),
+    selectedAudioOutput$: scope.behavior(
+      mediaDevices.audioOutput.selected$.pipe(map((s) => s?.id)),
+    ),
+    // Withheld where the platform can't route audio to a chosen device, which
+    // disables the speaker section.
+    selectAudioOutputOption$: constant(
+      supportsAudioOutputSelection()
+        ? mediaDevices.audioOutput.select
+        : undefined,
+    ),
+    videoOptions$: scope.behavior(options$(mediaDevices.videoInput.available$)),
     selectedVideo$: scope.behavior(
       mediaDevices.videoInput.selected$.pipe(map((s) => s?.id)),
     ),
@@ -263,10 +265,13 @@ export function createLobbyFooterViewModel(
       reactionData: undefined,
       tileStoreGeneration: undefined,
       audioOptions: undefined,
+      audioOutputOptions: undefined,
       videoOptions: undefined,
       selectedAudio: undefined,
+      selectedAudioOutput: undefined,
       selectedVideo: undefined,
       selectAudioButtonOption: undefined,
+      selectAudioOutputOption: undefined,
       selectVideoButtonOption: undefined,
     }),
     ...buildMuteBehaviors(scope, muteStates),

src/components/MediaMuteAndSwitchButton.module.css

@@ -35,3 +35,60 @@ Please see LICENSE in the repository root for full details.
     transform: rotate(360deg);
   }
 }
+
+.menu {
+  display: flex;
+  flex-direction: column;
+}
+
+/* Only the device lists scroll, bounded by the measured call area: the menu is
+   portalled out of the root, so CSS can't size it against the call. */
+.deviceList {
+  overflow-y: auto;
+  min-block-size: 0;
+  max-block-size: var(--device-list-max-height);
+  /* Keeps a row reached by keyboard clear of the sticky heading and meter. */
+  scroll-padding-block: var(--device-list-scroll-padding-start, 0)
+    var(--device-list-scroll-padding-end, 0);
+}
+
+/* Compound's heading rule heads each section; the design adds space below it. */
+.menu h3 {
+  margin-block-end: var(--cpd-space-5x);
+}
+
+/* And more above a heading that follows another section. */
+.deviceList [role="group"] + [role="group"] h3 {
+  margin-block-start: var(--cpd-space-7x);
+}
+
+/* Sticky within its own section. Opaque and inset a border width so it doesn't
+   paint over the menu's outline. */
+.sectionHeading {
+  position: sticky;
+  inset-block-start: 0;
+  background: var(--cpd-color-bg-canvas-default);
+  margin-inline: var(--cpd-border-width-1);
+  margin-block-start: var(--cpd-border-width-1);
+}
+
+/* Sticky at the foot of the microphone section; opaque and inset as above. */
+.stickyMeter {
+  position: sticky;
+  inset-block-end: 0;
+  background: var(--cpd-color-bg-canvas-default);
+  margin-inline: var(--cpd-border-width-1);
+  margin-block-end: var(--cpd-border-width-1);
+}
+
+/* Radix focuses whatever the pointer is over, so the browser's ring would
+   follow the mouse. Replaced by one shown only for keyboard focus. */
+.menu [role^="menuitem"]:focus,
+.menu [role^="menuitem"]:focus-visible {
+  outline: none;
+}
+
+.menu[data-focus-source="keyboard"] [role^="menuitem"]:focus {
+  outline: var(--cpd-border-width-2) solid var(--cpd-color-border-focused);
+  outline-offset: calc(-1 * var(--cpd-border-width-2));
+}

src/components/MediaMuteAndSwitchButton.stories.tsx

@@ -5,12 +5,15 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { fn, userEvent, within, expect } from "storybook/test";
+import { fn, userEvent, waitFor, within, expect } from "storybook/test";
-import { type JSX } from "react";
+import { useEffect, useState, type FC, type JSX, type ReactNode } from "react";
 
 import type { Meta, StoryObj } from "@storybook/react-vite";
 import { MediaMuteAndSwitchButton } from "./MediaMuteAndSwitchButton";
+import styles from "./MediaMuteAndSwitchButton.module.css";
+import meterStyles from "./MicrophoneLevelMeter.module.css";
 import { MediaDevicesContext } from "../MediaDevicesContext";
+import { RootElementProvider } from "../RootElementContext";
 import { MediaDevices } from "../state/MediaDevices";
 import { globalScope } from "../state/ObservableScope";
 
@@ -18,12 +21,74 @@ const mediaDevices = new MediaDevices(globalScope, {
   controlledAudioDevices: false,
 });
 
+/** Supplies a microphone, a wavering tone: a story's invented device ids match no hardware. */
+const WithAMicrophone: FC<{ children: ReactNode }> = ({ children }) => {
+  useEffect(() => {
+    const context = new AudioContext();
+    const microphone = context.createMediaStreamDestination();
+    const tone = context.createOscillator();
+    const loudness = context.createGain();
+    // Wavers between a third and two thirds of full scale, so it reads as live.
+    const swing = context.createOscillator();
+    const depth = context.createGain();
+    loudness.gain.value = 0.25;
+    depth.gain.value = 0.2;
+    swing.frequency.value = 0.6;
+    tone.frequency.value = 220;
+    swing.connect(depth).connect(loudness.gain);
+    tone.connect(loudness).connect(microphone);
+    tone.start();
+    swing.start();
+
+    const devices = navigator.mediaDevices;
+    const openedForReal = devices.getUserMedia.bind(devices);
+    const opened = Promise.resolve(microphone.stream);
+    // A fresh clone each time, so a caller stopping its tracks doesn't end the next.
+    devices.getUserMedia = async (): Promise<MediaStream> =>
+      (await opened).clone();
+
+    return (): void => {
+      devices.getUserMedia = openedForReal;
+      tone.stop();
+      swing.stop();
+      void context.close();
+    };
+  }, []);
+
+  return <>{children}</>;
+};
+
+/** Supplies a call-sized root. Without one the list is bounded by the whole Storybook frame. */
+const WithACallArea: FC<{ children: ReactNode }> = ({ children }) => {
+  const [callArea, setCallArea] = useState<HTMLElement | null>(null);
+  return (
+    <div
+      ref={setCallArea}
+      style={{
+        // A call's size: anything smaller makes a short device list scroll.
+        blockSize: 720,
+        display: "flex",
+        alignItems: "flex-end",
+        justifyContent: "center",
+      }}
+    >
+      {callArea !== null && (
+        <RootElementProvider value={callArea}>{children}</RootElementProvider>
+      )}
+    </div>
+  );
+};
+
 const meta = {
   component: MediaMuteAndSwitchButton,
   decorators: [
     (Story): JSX.Element => (
       <MediaDevicesContext value={mediaDevices}>
-        <Story />
+        <WithACallArea>
+          <WithAMicrophone>
+            <Story />
+          </WithAMicrophone>
+        </WithACallArea>
       </MediaDevicesContext>
     ),
   ],
@@ -34,7 +99,6 @@ type Story = StoryObj<typeof meta>;
 
 export const Default: Story = {
   args: {
-    title: "SomeMenu",
     iconsAndLabels: "audio",
     enabled: true,
     options: [
@@ -42,6 +106,13 @@ export const Default: Story = {
       { label: { type: "name", name: "Option 2" }, id: "2" },
     ],
     selectedOption: "1",
+    // The footer always passes an output list to the audio menu.
+    outputOptions: [
+      { label: { type: "default", name: "Built-in Output" }, id: "default" },
+      { label: { type: "name", name: "Headset" }, id: "spk2" },
+    ],
+    selectedOutputOption: "default",
+    onSelectOutput: fn(),
     onMuteClick: fn(),
     onSelect: fn(),
   },
@@ -50,7 +121,6 @@ export const Default: Story = {
 export const AudioMute: Story = {
   args: {
     ...Default.args,
-    title: "Microphone",
     iconsAndLabels: "audio",
     enabled: false,
     options: [
@@ -73,21 +143,19 @@ export const AudioMute: Story = {
 
 export const AudioUnmute: Story = {
   args: {
-    title: "Microphone",
+    ...Default.args,
     iconsAndLabels: "audio",
     enabled: true,
     options: [
       { label: { type: "name", name: "Microphone 1" }, id: "1" },
       { label: { type: "name", name: "Microphone 2" }, id: "2" },
     ],
-
     selectedOption: "2",
   },
 };
 
 export const VideoMute: Story = {
   args: {
-    title: "Camera",
     iconsAndLabels: "video",
     enabled: false,
     options: [
@@ -101,7 +169,6 @@ export const VideoMute: Story = {
 
 export const VideoUnmute: Story = {
   args: {
-    title: "Camera",
     iconsAndLabels: "video",
     enabled: true,
     options: [
@@ -113,3 +180,479 @@ export const VideoUnmute: Story = {
     selectedOption: "2",
   },
 };
+
+export const SpeakerAndMicrophoneSections: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    options: [
+      { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+      { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+    ],
+    selectedOption: "mic1",
+    outputOptions: [
+      { label: { type: "default", name: "Built-in Output" }, id: "default" },
+      { label: { type: "name", name: "Headset" }, id: "spk2" },
+    ],
+    selectedOutputOption: "default",
+    onSelectOutput: fn(),
+  },
+  play: async ({ args, canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+
+    const headset = await within(document.body).findByRole("menuitemradio", {
+      name: "Headset",
+    });
+    await userEvent.click(headset);
+    await expect(args.onSelectOutput).toHaveBeenCalledWith("spk2");
+
+    // A few devices fit, so the list doesn't scroll.
+    const list = document.body.querySelector<HTMLElement>(
+      `.${styles.deviceList}`,
+    )!;
+    await expect(list.scrollHeight).toBe(list.clientHeight);
+
+    // Each section is headed by its own edge-to-edge rule, with no separator.
+    const menu = document.body.querySelector("[role='menu']")!;
+    await expect(
+      document.body.querySelectorAll("[role='separator']"),
+    ).toHaveLength(0);
+    const headings = document.body.querySelectorAll<HTMLElement>(
+      `.${styles.sectionHeading}`,
+    );
+    await expect(headings).toHaveLength(2);
+    const frame = menu.getBoundingClientRect();
+    for (const heading of headings) {
+      const rule = heading.querySelector("h3")!;
+      await expect(
+        Number.parseFloat(getComputedStyle(rule).borderBottomWidth),
+      ).toBeGreaterThan(0);
+      // Edge to edge, within the frame.
+      const box = rule.getBoundingClientRect();
+      await expect(box.left - frame.left).toBeLessThanOrEqual(2);
+      await expect(frame.right - box.right).toBeLessThanOrEqual(2);
+    }
+
+    // The first device sits further below the rule than from the menu's edge.
+    // Asserted as a relationship, not pixels: the asymmetry is the design.
+    const control = document.body.querySelector("input[type='radio']")!;
+    const ruleBottom = headings[0]
+      .querySelector("h3")!
+      .getBoundingClientRect().bottom;
+    const box = control.getBoundingClientRect();
+    await expect(box.top - ruleBottom).toBeGreaterThan(box.left - frame.left);
+
+    // And a section stands further from the one above than from its own first
+    // device.
+    const groups = document.body.querySelectorAll("[role='group']");
+    const speakers = groups[0].querySelectorAll("input[type='radio']");
+    const lastSpeaker = speakers[speakers.length - 1].getBoundingClientRect();
+    const nextHeading = groups[1]!.querySelector("h3")!.getBoundingClientRect();
+    await expect(nextHeading.top - lastSpeaker.bottom).toBeGreaterThan(
+      box.top - ruleBottom,
+    );
+  },
+};
+
+export const OutputCannotBeChosen: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    options: [
+      { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+      { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+    ],
+    selectedOption: "mic1",
+    outputOptions: [
+      { label: { type: "name", name: "Speakers" }, id: "spk1" },
+      { label: { type: "name", name: "Headset" }, id: "spk2" },
+    ],
+    selectedOutputOption: "spk1",
+    // No callback: the speakers are listed, but none can be picked.
+    onSelectOutput: undefined,
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+
+    const speakers = await within(document.body).findByRole("menuitemradio", {
+      name: "Speakers",
+    });
+    await expect(speakers).toHaveAttribute("aria-disabled", "true");
+  },
+};
+
+export const OnlyOneDevice: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    options: [{ label: { type: "name", name: "Microphone 1" }, id: "mic1" }],
+    selectedOption: "mic1",
+    outputOptions: [{ label: { type: "name", name: "Speakers" }, id: "spk1" }],
+    selectedOutputOption: "spk1",
+    onSelectOutput: fn(),
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+
+    // Shown, disabled, rather than hidden.
+    const only = await within(document.body).findByRole("menuitemradio", {
+      name: "Microphone 1",
+    });
+    await expect(only).toHaveAttribute("aria-disabled", "true");
+  },
+};
+
+/** A requested device hasn't arrived: nothing in either section can be picked. */
+export const SelectionSettling: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    options: [
+      { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+      { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+    ],
+    selectedOption: "mic1",
+    outputOptions: [
+      { label: { type: "name", name: "Speakers" }, id: "spk1" },
+      { label: { type: "name", name: "Headset" }, id: "spk2" },
+    ],
+    selectedOutputOption: "spk1",
+    onSelectOutput: fn(),
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+    const menu = within(document.body);
+
+    // selectedOption never changes, so the request stays in flight.
+    await userEvent.click(
+      await menu.findByRole("menuitemradio", { name: "Microphone 2" }),
+    );
+
+    await expect(await menu.findByLabelText("Activating…")).toBeVisible();
+    for (const item of menu.getAllByRole("menuitemradio"))
+      await expect(item).toHaveAttribute("aria-disabled", "true");
+  },
+};
+
+/**
+ * The ring shows for keyboard focus only. Asserted on the painted outline:
+ * asserting data-focus-source would still pass with the CSS rule deleted.
+ */
+export const KeyboardFocusRing: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    options: [
+      { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+      { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+    ],
+    selectedOption: "mic1",
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+    const menu = within(document.body);
+    const first = await menu.findByRole("menuitemradio", {
+      name: "Microphone 1",
+    });
+
+    // Opened by pointer: no ring, even though Radix has moved focus.
+    await expect(outlineWidth(first)).toBe(0);
+
+    await userEvent.keyboard("{ArrowDown}");
+    const focused = document.activeElement as HTMLElement;
+    await expect(focused).toHaveRole("menuitemradio");
+    await expect(outlineWidth(focused)).toBeGreaterThan(0);
+
+    // And the pointer takes it away again.
+    await userEvent.hover(first);
+    await expect(outlineWidth(document.activeElement as HTMLElement)).toBe(0);
+  },
+};
+
+/** The list scrolls; the meter stays at the foot of the microphone section. */
+export const ManyDevices: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    options: Array.from({ length: 20 }, (_, i) => ({
+      label: { type: "name" as const, name: `Microphone ${i + 1}` },
+      id: `mic${i + 1}`,
+    })),
+    selectedOption: "mic1",
+    outputOptions: Array.from({ length: 6 }, (_, i) => ({
+      label: { type: "name" as const, name: `Speaker ${i + 1}` },
+      id: `spk${i + 1}`,
+    })),
+    selectedOutputOption: "spk1",
+    onSelectOutput: fn(),
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+    const menu = within(document.body);
+
+    // The sticky wrapper rather than the meter: without a fake microphone (as on
+    // WebKit) the meter shows a message instead of a level.
+    const list = document.body.querySelector<HTMLElement>(
+      `.${styles.deviceList}`,
+    )!;
+    const sticky = await waitFor(() => {
+      const element = document.body.querySelector<HTMLElement>(
+        `.${styles.stickyMeter}`,
+      );
+      if (element === null) throw new Error("the meter has not rendered yet");
+      return element;
+    });
+    await expect(list.scrollHeight).toBeGreaterThan(list.clientHeight);
+
+    // Scrolled so the microphone section starts at the top: only there does a
+    // pinned meter differ from one that is simply last.
+    const group = await menu.findByRole("group", { name: "Microphone" });
+    list.scrollTop +=
+      group.getBoundingClientRect().top - list.getBoundingClientRect().top;
+    await expect(list.scrollTop + list.clientHeight).toBeLessThan(
+      list.scrollHeight,
+    );
+
+    const scrollport = list.getBoundingClientRect();
+    const pinned = sticky.getBoundingClientRect();
+    await expect(pinned.bottom).toBeLessThanOrEqual(scrollport.bottom + 1);
+    await expect(pinned.top).toBeGreaterThanOrEqual(scrollport.top - 1);
+
+    // The whole menu is on screen, not bounded by the document.
+    const frame = document.body
+      .querySelector("[role='menu']")!
+      .getBoundingClientRect();
+    await expect(frame.top).toBeGreaterThanOrEqual(0);
+    await expect(frame.bottom).toBeLessThanOrEqual(window.innerHeight + 1);
+
+    // The meter is the menu's one opaque part, so it must stay inside the frame.
+    await expect(pinned.left).toBeGreaterThan(frame.left);
+    await expect(pinned.right).toBeLessThan(frame.right);
+  },
+};
+
+/** Painted outline width, in px. */
+function outlineWidth(element: HTMLElement): number {
+  const { outlineStyle, outlineWidth } = getComputedStyle(element);
+  if (outlineStyle === "none") return 0;
+  return Number.parseFloat(outlineWidth) || 0;
+}
+
+/** Safari lists no outputs: a disabled, selected Default stands in. */
+export const OutputNotEnumerated: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    options: [
+      { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+      { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+    ],
+    selectedOption: "mic1",
+    outputOptions: [],
+    selectedOutputOption: undefined,
+    onSelectOutput: undefined,
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+
+    const speakers = await within(document.body).findByRole("menuitemradio", {
+      name: "Default",
+    });
+    await expect(speakers).toHaveAttribute("aria-disabled", "true");
+  },
+};
+
+/** The meter's icon shares the radio controls' centre line; only a real browser lays this out. */
+export const MeterAlignsWithTheDeviceRows: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    options: [
+      { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+      { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+    ],
+    selectedOption: "mic1",
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+
+    const menu = document.body.querySelector("[role='menu']")!;
+    const radio = menu.querySelector("input[type='radio']")!;
+    const icon = await waitFor(() => {
+      const element = document.body.querySelector(`.${meterStyles.icon}`);
+      if (element === null) throw new Error("the meter has not rendered yet");
+      return element;
+    });
+
+    // A pixel of slack, for subpixel layout.
+    await expect(Math.abs(centre(icon) - centre(radio))).toBeLessThanOrEqual(1);
+  },
+};
+
+/** Inline-axis centre of an element. */
+function centre(element: Element): number {
+  const box = element.getBoundingClientRect();
+  return box.left + box.width / 2;
+}
+
+/** Every row the keyboard reaches is fully visible, not under a heading or the meter. */
+export const KeyboardReachesEveryDevice: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    // Enough to scroll both ways, so either end can hide a row.
+    options: Array.from({ length: 20 }, (_, i) => ({
+      label: { type: "name" as const, name: `Microphone ${i + 1}` },
+      id: `mic${i + 1}`,
+    })),
+    selectedOption: "mic1",
+    outputOptions: Array.from({ length: 4 }, (_, i) => ({
+      label: { type: "name" as const, name: `Speaker ${i + 1}` },
+      id: `spk${i + 1}`,
+    })),
+    selectedOutputOption: "spk1",
+    onSelectOutput: fn(),
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+
+    const meter = await waitFor(() => {
+      const element = document.body.querySelector<HTMLElement>(
+        `.${styles.stickyMeter}`,
+      );
+      if (element === null) throw new Error("the meter has not rendered yet");
+      return element;
+    });
+
+    // Drawn over the list: the sticky headings and the meter.
+    const overlays = [
+      meter,
+      ...document.body.querySelectorAll<HTMLElement>(
+        `.${styles.sectionHeading}`,
+      ),
+    ];
+    const items = within(document.body).getAllByRole("menuitemradio");
+
+    // Down to the last device and back up.
+    for (const key of ["{ArrowDown}", "{ArrowUp}"])
+      for (let i = 0; i < items.length; i++) {
+        await userEvent.keyboard(key);
+        const focused = document.activeElement as HTMLElement;
+        await expect(focused).toHaveRole("menuitemradio");
+        // Checked as overlap: a heading only covers rows while its section is on
+        // screen.
+        await expect(overlapping(focused, overlays)).toBeLessThanOrEqual(1);
+      }
+  },
+};
+
+/** A section's heading stays at the top while the section is in view, and leaves with it. */
+export const HeadingsStayWhileScrolling: Story = {
+  args: {
+    ...Default.args,
+    iconsAndLabels: "audio",
+    enabled: true,
+    options: Array.from({ length: 20 }, (_, i) => ({
+      label: { type: "name" as const, name: `Microphone ${i + 1}` },
+      id: `mic${i + 1}`,
+    })),
+    selectedOption: "mic1",
+    outputOptions: Array.from({ length: 4 }, (_, i) => ({
+      label: { type: "name" as const, name: `Speaker ${i + 1}` },
+      id: `spk${i + 1}`,
+    })),
+    selectedOutputOption: "spk1",
+    onSelectOutput: fn(),
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+    const menu = within(document.body);
+
+    const list = document.body.querySelector<HTMLElement>(
+      `.${styles.deviceList}`,
+    )!;
+    const group = await menu.findByRole("group", { name: "Microphone" });
+    // By class: the heading is aria-hidden, and its group carries the name.
+    const heading = group.querySelector<HTMLElement>(
+      `.${styles.sectionHeading}`,
+    )!;
+
+    // Far enough that the heading is only on screen if it is stuck there.
+    list.scrollTop +=
+      group.getBoundingClientRect().top - list.getBoundingClientRect().top + 80;
+
+    const scrollport = list.getBoundingClientRect();
+    await expect(heading.getBoundingClientRect().top).toBeLessThanOrEqual(
+      scrollport.top + 2,
+    );
+    await expect(heading.getBoundingClientRect().bottom).toBeGreaterThan(
+      scrollport.top,
+    );
+    // Clear of the menu's frame.
+    const frame = document.body
+      .querySelector("[role='menu']")!
+      .getBoundingClientRect();
+    await expect(heading.getBoundingClientRect().left).toBeGreaterThan(
+      frame.left,
+    );
+  },
+};
+
+/** How far the most overlapping of `overlays` covers `element`, in px. */
+function overlapping(element: Element, overlays: Element[]): number {
+  const box = element.getBoundingClientRect();
+  return overlays.reduce((worst, overlay) => {
+    const over = overlay.getBoundingClientRect();
+    const shared =
+      Math.min(box.bottom, over.bottom) - Math.max(box.top, over.top);
+    return Math.max(worst, shared);
+  }, 0);
+}
+
+/** The blur toggle gets the keyboard ring too: it is the menu's child, not the list's. */
+export const FocusRingCoversTheBlurToggle: Story = {
+  args: {
+    ...VideoUnmute.args,
+    iconsAndLabels: "video",
+    videoBlurEnabled: false,
+    videoBlurToggleClick: fn(),
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Camera" }));
+    const toggle = await within(document.body).findByRole("menuitemcheckbox", {
+      name: /Blur background/,
+    });
+
+    // Arrow down past the cameras to the toggle.
+    for (let i = 0; i < 6 && document.activeElement !== toggle; i++)
+      await userEvent.keyboard("{ArrowDown}");
+    await expect(document.activeElement).toBe(toggle);
+    // The same ring the device rows get.
+    await expect(outlineWidth(toggle)).toBeGreaterThan(0);
+
+    // And the pointer takes it away, with the toggle still focused.
+    await userEvent.hover(toggle);
+    await expect(document.activeElement).toBe(toggle);
+    await expect(outlineWidth(toggle)).toBe(0);
+  },
+};

src/components/MediaMuteAndSwitchButton.test.tsx

@@ -5,40 +5,61 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { describe, expect, test, vi } from "vitest";
+import { afterEach, describe, expect, test, vi } from "vitest";
-import { act, render, screen, type RenderResult } from "@testing-library/react";
+import { axe } from "vitest-axe";
+import {
+  act,
+  render,
+  screen,
+  within,
+  type RenderResult,
+} from "@testing-library/react";
 import userEvent from "@testing-library/user-event";
-import { type JSX, useState, type ReactNode } from "react";
+import { Profiler, type JSX, useState, type ReactNode } from "react";
 import { TooltipProvider } from "@vector-im/compound-web";
 
-import { MediaMuteAndSwitchButton } from "./MediaMuteAndSwitchButton";
+import {
+  MediaMuteAndSwitchButton,
+  type MenuOptions,
+} from "./MediaMuteAndSwitchButton";
 import { MediaDevicesContext } from "../MediaDevicesContext";
 import { type MediaDevices } from "../state/MediaDevices";
+import { restoreAudioCapture, stubAudioCapture } from "../utils/test";
 
 interface RenderOptions {
   requestDeviceNames: () => void;
 }
 
-function renderComponent(
+function withProviders(
   component: ReactNode,
   { requestDeviceNames = (): void => {} }: Partial<RenderOptions> = {},
-): RenderResult {
+): JSX.Element {
-  return render(
+  return (
     <TooltipProvider>
       <MediaDevicesContext
         value={{ requestDeviceNames } as unknown as MediaDevices}
       >
         {component}
       </MediaDevicesContext>
-    </TooltipProvider>,
+    </TooltipProvider>
   );
 }
 
+function renderComponent(
+  component: ReactNode,
+  options: Partial<RenderOptions> = {},
+): RenderResult {
+  return render(withProviders(component, options));
+}
+
 describe("MediaMuteAndSwitchButton", () => {
+  // Only one test stubs the capture; don't let it leak into the rest.
+  afterEach(restoreAudioCapture);
+
   test("renders", () => {
     const { container } = renderComponent(
       <TooltipProvider>
-        <MediaMuteAndSwitchButton title={"Switcher"} iconsAndLabels={"audio"} />
+        <MediaMuteAndSwitchButton iconsAndLabels={"audio"} />
       </TooltipProvider>,
     );
     expect(container).toMatchSnapshot();
@@ -50,11 +71,7 @@ describe("MediaMuteAndSwitchButton", () => {
       enabled: boolean,
     ): RenderResult => {
       return renderComponent(
-        <MediaMuteAndSwitchButton
+        <MediaMuteAndSwitchButton iconsAndLabels={type} enabled={enabled} />,
-          title={"Switcher"}
-          iconsAndLabels={type}
-          enabled={enabled}
-        />,
       );
     };
     const renderAudioEndabled = renderLabels("audio", true);
@@ -81,7 +98,6 @@ describe("MediaMuteAndSwitchButton", () => {
     const onMute = vi.fn();
     const { getByRole } = renderComponent(
       <MediaMuteAndSwitchButton
-        title={"Switcher"}
         onMuteClick={onMute}
         iconsAndLabels="audio"
         enabled={true}
@@ -98,7 +114,6 @@ describe("MediaMuteAndSwitchButton", () => {
     const onMute = vi.fn();
     const { getByRole } = renderComponent(
       <MediaMuteAndSwitchButton
-        title={"Switcher"}
         onMuteClick={onMute}
         iconsAndLabels="audio"
         enabled={true}
@@ -119,7 +134,6 @@ describe("MediaMuteAndSwitchButton", () => {
     const onMute = vi.fn();
     const { getByRole } = renderComponent(
       <MediaMuteAndSwitchButton
-        title={"Switcher"}
         onMuteClick={onMute}
         iconsAndLabels="video"
         enabled={true}
@@ -139,11 +153,7 @@ describe("MediaMuteAndSwitchButton", () => {
     const user = userEvent.setup();
     const requestDeviceNames = vi.fn();
     renderComponent(
-      <MediaMuteAndSwitchButton
+      <MediaMuteAndSwitchButton iconsAndLabels="audio" enabled />,
-        title="Switcher"
-        iconsAndLabels="audio"
-        enabled
-      />,
       { requestDeviceNames },
     );
 
@@ -157,7 +167,6 @@ describe("MediaMuteAndSwitchButton", () => {
     renderComponent(
       <>
         <MediaMuteAndSwitchButton
-          title="Switcher"
           iconsAndLabels="audio"
           enabled
           options={[
@@ -167,7 +176,6 @@ describe("MediaMuteAndSwitchButton", () => {
           selectedOption="mic1"
         />
         <MediaMuteAndSwitchButton
-          title="Switcher"
           iconsAndLabels="video"
           enabled
           options={[
@@ -193,7 +201,6 @@ describe("MediaMuteAndSwitchButton", () => {
     const onSelect = vi.fn();
     const { getByRole } = renderComponent(
       <MediaMuteAndSwitchButton
-        title="Switcher"
         iconsAndLabels="audio"
         enabled={true}
         options={[
@@ -217,7 +224,6 @@ describe("MediaMuteAndSwitchButton", () => {
     const onSelect = vi.fn();
     const { getByRole } = renderComponent(
       <MediaMuteAndSwitchButton
-        title="Switcher"
         iconsAndLabels="audio"
         enabled={true}
         options={[
@@ -246,7 +252,6 @@ describe("MediaMuteAndSwitchButton", () => {
       const [selectedOption, setSelectedOption] = useState("mic1");
       return (
         <MediaMuteAndSwitchButton
-          title="Switcher"
           iconsAndLabels="audio"
           enabled={true}
           options={[
@@ -306,7 +311,6 @@ describe("MediaMuteAndSwitchButton", () => {
     const onVideoBlurToggle = vi.fn();
     const { getByRole } = renderComponent(
       <MediaMuteAndSwitchButton
-        title="Switcher"
         iconsAndLabels="video"
         enabled={true}
         videoBlurToggleClick={onVideoBlurToggle}
@@ -327,11 +331,10 @@ describe("MediaMuteAndSwitchButton", () => {
     expect(onVideoBlurToggle).toHaveBeenCalled();
   });
 
-  test("renders check icon to mark the selected menu item", async () => {
+  test("marks the selected menu item as checked", async () => {
     const user = userEvent.setup();
     const { getByRole } = renderComponent(
       <MediaMuteAndSwitchButton
-        title="Switcher"
         iconsAndLabels="audio"
         enabled={true}
         options={[
@@ -342,19 +345,493 @@ describe("MediaMuteAndSwitchButton", () => {
       />,
     );
 
-    // open menu
     await user.click(getByRole("button", { name: "Microphone" }));
 
-    // The selected item (mic2) renders both an IconOptions SVG and a CheckIcon SVG
+    screen.getByRole("menuitemradio", { name: "Microphone 2", checked: true });
-    const mic1Item = screen.getByRole("menuitemradio", {
+    screen.getByRole("menuitemradio", { name: "Microphone 1", checked: false });
-      name: "Microphone 2",
+  });
-    });
-    expect(mic1Item.querySelectorAll("svg").length).toBe(2);
 
-    // The unselected item (mic1) only renders its IconOptions SVG
+  test("disables every device while a selection is settling", async () => {
-    const mic2Item = screen.getByRole("menuitemradio", {
+    const user = userEvent.setup();
+    const { promise, resolve } = Promise.withResolvers<void>();
+    function Wrapper(): JSX.Element {
+      const [selectedOption, setSelectedOption] = useState("mic1");
+      return (
+        <MediaMuteAndSwitchButton
+          iconsAndLabels="audio"
+          enabled={true}
+          options={[
+            { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+            { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+          ]}
+          selectedOption={selectedOption}
+          onSelect={(id) => {
+            void promise.then(() => setSelectedOption(id));
+          }}
+          outputOptions={[
+            { label: { type: "name", name: "Speakers" }, id: "spk1" },
+            { label: { type: "name", name: "Headset" }, id: "spk2" },
+          ]}
+          selectedOutputOption="spk1"
+          onSelectOutput={vi.fn()}
+        />
+      );
+    }
+
+    const { getByRole } = renderComponent(<Wrapper />);
+    await user.click(getByRole("button", { name: "Microphone" }));
+    await user.click(
+      screen.getByRole("menuitemradio", { name: "Microphone 2" }),
+    );
+
+    // In flight: nothing else can be picked, in either section.
+    for (const name of ["Microphone 1", "Speakers", "Headset"]) {
+      expect(screen.getByRole("menuitemradio", { name })).toHaveAttribute(
+        "aria-disabled",
+        "true",
+      );
+    }
+
+    await act(async () => {
+      resolve();
+      await promise;
+    });
+
+    // Settled: selectable again.
+    expect(
+      screen.getByRole("menuitemradio", { name: "Microphone 1" }),
+    ).not.toHaveAttribute("aria-disabled", "true");
+    expect(
+      screen.getByRole("menuitemradio", { name: "Headset" }),
+    ).not.toHaveAttribute("aria-disabled", "true");
+  });
+
+  test("lets go of a device switch that never arrives", async () => {
+    const user = userEvent.setup();
+    // onSelect never reports back, as when a device is removed mid-switch.
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+          { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+        ]}
+        selectedOption="mic1"
+        onSelect={vi.fn()}
+        outputOptions={[
+          { label: { type: "name", name: "Speakers" }, id: "spk1" },
+          { label: { type: "name", name: "Headset" }, id: "spk2" },
+        ]}
+        selectedOutputOption="spk1"
+        onSelectOutput={vi.fn()}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+    await user.click(
+      screen.getByRole("menuitemradio", { name: "Microphone 2" }),
+    );
+    await user.keyboard("{Escape}");
+    await user.click(getByRole("button", { name: "Microphone" }));
+
+    for (const name of ["Microphone 1", "Speakers", "Headset"]) {
+      expect(screen.getByRole("menuitemradio", { name })).not.toHaveAttribute(
+        "aria-disabled",
+        "true",
+      );
+    }
+  });
+
+  test("lets go of a device switch whose device is unplugged", async () => {
+    const user = userEvent.setup();
+    const mics: MenuOptions[] = [
+      { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+      { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+    ];
+    const menu = (options: MenuOptions[]): JSX.Element => (
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={options}
+        selectedOption="mic1"
+        onSelect={vi.fn()}
+        outputOptions={[
+          { label: { type: "name", name: "Speakers" }, id: "spk1" },
+          { label: { type: "name", name: "Headset" }, id: "spk2" },
+        ]}
+        selectedOutputOption="spk1"
+        onSelectOutput={vi.fn()}
+      />
+    );
+
+    const { getByRole, rerender } = renderComponent(menu(mics));
+    await user.click(getByRole("button", { name: "Microphone" }));
+    await user.click(
+      screen.getByRole("menuitemradio", { name: "Microphone 2" }),
+    );
+
+    // The second microphone is unplugged before the switch lands.
+    rerender(withProviders(menu(mics.slice(0, 1))));
+
+    // Selectable again without closing the menu.
+    expect(
+      screen.getByRole("menuitemradio", { name: "Headset" }),
+    ).not.toHaveAttribute("aria-disabled", "true");
+  });
+
+  test("moves the level without re-rendering anything", async () => {
+    // The level is drawn into the DOM, so a moving level commits nothing.
+    const capture = stubAudioCapture();
+    const user = userEvent.setup();
+    let commits = 0;
+
+    const { getByRole } = renderComponent(
+      <Profiler
+        id="menu"
+        onRender={(): void => {
+          commits++;
+        }}
+      >
+        <MediaMuteAndSwitchButton
+          iconsAndLabels="audio"
+          enabled={true}
+          options={[
+            { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+            { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+          ]}
+          selectedOption="mic1"
+          onSelect={vi.fn()}
+          outputOptions={[
+            { label: { type: "name", name: "Speakers" }, id: "spk1" },
+            { label: { type: "name", name: "Headset" }, id: "spk2" },
+          ]}
+          selectedOutputOption="spk1"
+          onSelectOutput={vi.fn()}
+        />
+      </Profiler>,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+    capture.grant();
+    await vi.waitFor(() => expect(capture.contexts).toHaveLength(1));
+    const meter = await screen.findByRole("meter");
+    // The capture's arrival is one render: the idle level swapped for its own.
+    await act(async () => {});
+    const settled = commits;
+
+    // The meter smooths by elapsed time, so hand-driven frames need a clock.
+    let elapsed = performance.now();
+    const clock = vi
+      .spyOn(performance, "now")
+      .mockImplementation(() => (elapsed += 16));
+
+    // One frame per task, as a browser delivers them: one act() would batch them.
+    for (let step = 1; step <= 8; step++) {
+      capture.speak(step / 8);
+      await act(async () => {
+        capture.drawFrames(1);
+        await Promise.resolve();
+      });
+    }
+    clock.mockRestore();
+
+    expect(meter.getAttribute("aria-valuenow")).not.toBe("0");
+    expect(commits - settled).toBe(0);
+  });
+
+  test("camera menu uses the same selection pattern and keeps the blur toggle", async () => {
+    const user = userEvent.setup();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="video"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Camera 1" }, id: "cam1" },
+          { label: { type: "name", name: "Camera 2" }, id: "cam2" },
+        ]}
+        selectedOption="cam1"
+        onSelect={vi.fn()}
+        videoBlurToggleClick={vi.fn()}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Camera" }));
+
+    screen.getByRole("menuitemradio", { name: "Camera 1", checked: true });
+    screen.getByRole("menuitemradio", { name: "Camera 2", checked: false });
+    expect(
+      screen.getByRole("menuitemcheckbox", { name: "Blur background" }),
+    ).toBeInTheDocument();
+  });
+
+  test("marks focus as keyboard-driven only when the keyboard moved it", async () => {
+    const user = userEvent.setup();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+          { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+        ]}
+        selectedOption="mic1"
+        onSelect={vi.fn()}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+    const list = screen
+      .getByRole("menuitemradio", { name: "Microphone 1" })
+      .closest("[data-focus-source]");
+
+    // The menu focuses whatever the pointer is over, so focus alone says nothing.
+    expect(list).toHaveAttribute("data-focus-source", "pointer");
+
+    await user.keyboard("{ArrowDown}");
+    expect(list).toHaveAttribute("data-focus-source", "keyboard");
+
+    await user.pointer({
+      target: screen.getByRole("menuitemradio", { name: "Microphone 2" }),
+      coords: { clientX: 10, clientY: 10 },
+    });
+    expect(list).toHaveAttribute("data-focus-source", "pointer");
+  });
+
+  test("marks the selected device with the accent fill", async () => {
+    const user = userEvent.setup();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+          { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+        ]}
+        selectedOption="mic2"
+        onSelect={vi.fn()}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+
+    const selected = screen
+      .getByRole("menuitemradio", { name: "Microphone 2" })
+      .querySelector("input[type=radio]");
+    expect(selected).toBeChecked();
+    // readOnly would paint the selected radio muted.
+    expect(selected).not.toHaveAttribute("readonly");
+  });
+
+  test("the open menu has no accessibility violations", async () => {
+    const user = userEvent.setup();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+          { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+        ]}
+        selectedOption="mic1"
+        onSelect={vi.fn()}
+        outputOptions={[
+          { label: { type: "name", name: "Speakers" }, id: "spk1" },
+          { label: { type: "name", name: "Headset" }, id: "spk2" },
+        ]}
+        selectedOutputOption="spk1"
+        onSelectOutput={vi.fn()}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+
+    const menu = document.querySelector('[role="menu"]');
+    expect(await axe(menu as HTMLElement)).toHaveNoViolations();
+  });
+
+  test("puts the speaker section above the microphone section", async () => {
+    const user = userEvent.setup();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+          { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+        ]}
+        selectedOption="mic1"
+        onSelect={vi.fn()}
+        outputOptions={[
+          { label: { type: "name", name: "Speakers" }, id: "spk1" },
+          { label: { type: "name", name: "Headset" }, id: "spk2" },
+        ]}
+        selectedOutputOption="spk1"
+        onSelectOutput={vi.fn()}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+
+    const speakers = screen.getByRole("menuitemradio", { name: "Speakers" });
+    const microphone = screen.getByRole("menuitemradio", {
       name: "Microphone 1",
     });
-    expect(mic2Item.querySelectorAll("svg").length).toBe(1);
+    expect(
+      speakers.compareDocumentPosition(microphone) &
+        Node.DOCUMENT_POSITION_FOLLOWING,
+    ).toBeTruthy();
+  });
+
+  test("lists speaker and microphone sections", async () => {
+    const user = userEvent.setup();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+          { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+        ]}
+        selectedOption="mic1"
+        onSelect={vi.fn()}
+        outputOptions={[
+          {
+            label: { type: "default", name: "Built-in Output" },
+            id: "default",
+          },
+          { label: { type: "name", name: "Headset" }, id: "spk2" },
+        ]}
+        selectedOutputOption="default"
+        onSelectOutput={vi.fn()}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+
+    screen.getByRole("menuitemradio", {
+      name: "Default (Built-in Output)",
+      checked: true,
+    });
+    screen.getByRole("menuitemradio", { name: "Headset", checked: false });
+    screen.getByRole("menuitemradio", { name: "Microphone 1", checked: true });
+    screen.getByRole("menuitemradio", { name: "Microphone 2", checked: false });
+  });
+
+  test("calls the output select callback on speaker click", async () => {
+    const user = userEvent.setup();
+    const onSelectOutput = vi.fn();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+          { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+        ]}
+        selectedOption="mic1"
+        outputOptions={[
+          { label: { type: "name", name: "Speakers" }, id: "spk1" },
+          { label: { type: "name", name: "Headset" }, id: "spk2" },
+        ]}
+        selectedOutputOption="spk1"
+        onSelectOutput={onSelectOutput}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+    await user.click(screen.getByRole("menuitemradio", { name: "Headset" }));
+
+    expect(onSelectOutput).toHaveBeenCalledWith("spk2");
+  });
+
+  test("shows a single device entry disabled", async () => {
+    const user = userEvent.setup();
+    const onSelect = vi.fn();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+        ]}
+        selectedOption="mic1"
+        onSelect={onSelect}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+
+    // Shown, but not selectable.
+    const only = screen.getByRole("menuitemradio", { name: "Microphone 1" });
+    expect(only).toHaveAttribute("aria-disabled", "true");
+  });
+
+  test("shows a default speaker where the platform lists none", async () => {
+    const user = userEvent.setup();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+          { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+        ]}
+        selectedOption="mic1"
+        onSelect={vi.fn()}
+        // As Safari: no outputs listed.
+        outputOptions={[]}
+        selectedOutputOption={undefined}
+        onSelectOutput={undefined}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+
+    const speakers = screen
+      .getAllByRole("group")
+      .find((group) => group.getAttribute("aria-label") === "Speaker")!;
+    const entries = within(speakers).getAllByRole("menuitemradio");
+    expect(entries).toHaveLength(1);
+    expect(entries[0]).toHaveAccessibleName("Default");
+    expect(entries[0]).toHaveAttribute("aria-disabled", "true");
+    expect(entries[0]).toHaveAttribute("aria-checked", "true");
+    expect(
+      within(entries[0]).getByRole("radio", { hidden: true }),
+    ).toBeChecked();
+  });
+
+  test("shows the speaker section disabled when output selection is unsupported", async () => {
+    const user = userEvent.setup();
+    const { getByRole } = renderComponent(
+      <MediaMuteAndSwitchButton
+        iconsAndLabels="audio"
+        enabled={true}
+        options={[
+          { label: { type: "name", name: "Microphone 1" }, id: "mic1" },
+          { label: { type: "name", name: "Microphone 2" }, id: "mic2" },
+        ]}
+        selectedOption="mic1"
+        onSelect={vi.fn()}
+        outputOptions={[
+          { label: { type: "name", name: "Speakers" }, id: "spk1" },
+          { label: { type: "name", name: "Headset" }, id: "spk2" },
+        ]}
+        selectedOutputOption="spk1"
+        onSelectOutput={undefined}
+      />,
+    );
+
+    await user.click(getByRole("button", { name: "Microphone" }));
+
+    expect(
+      screen.getByRole("menuitemradio", { name: "Speakers" }),
+    ).toHaveAttribute("aria-disabled", "true");
+    expect(
+      screen.getByRole("menuitemradio", { name: "Headset" }),
+    ).toHaveAttribute("aria-disabled", "true");
+    expect(
+      screen.getByRole("menuitemradio", { name: "Microphone 2" }),
+    ).not.toHaveAttribute("aria-disabled", "true");
   });
 });

src/components/MediaMuteAndSwitchButton.tsx

@@ -5,37 +5,48 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { type ComponentType, useState, type FC, useEffect } from "react";
+import {
+  useCallback,
+  useState,
+  type CSSProperties,
+  type FC,
+  useEffect,
+  type ReactElement,
+} from "react";
 import {
   Button,
   Menu,
   MenuItem,
+  MenuTitle,
+  RadioInput,
   ToggleMenuItem,
 } from "@vector-im/compound-web";
 import {
-  CheckIcon,
   ChevronUpIcon,
   ChevronDownIcon,
-  MicOnIcon,
   SpinnerIcon,
-  VideoCallIcon,
 } from "@vector-im/compound-design-tokens/assets/web/icons";
 import classNames from "classnames";
 import { useTranslation } from "react-i18next";
+import { distinctUntilChanged, map } from "rxjs";
 
 import styles from "./MediaMuteAndSwitchButton.module.css";
 import { MicButton, VideoButton } from "../button";
-import { type DeviceLabel } from "../state/MediaDevices";
+import {
+  type AudioOutputDeviceLabel,
+  type DeviceLabel,
+} from "../state/MediaDevices";
 import { useMediaDevices } from "../MediaDevicesContext";
+import { useRootElement } from "../RootElementContext";
+import { observeElementSize$ } from "../utils/elementSize";
+import { LiveMicrophoneLevelMeter } from "./MicrophoneLevelMeter";
 
 export interface MenuOptions {
-  label: DeviceLabel;
+  label: DeviceLabel | AudioOutputDeviceLabel;
   id: string;
 }
 
 export interface MediaMuteAndSwitchButtonProps {
-  /** The title used in the Switcher modal. */
-  title: string;
   /** If the Mute button is enabled */
   enabled?: boolean;
   /** Callback if the mute button is clicked */
@@ -47,6 +58,12 @@ export interface MediaMuteAndSwitchButtonProps {
   options?: MenuOptions[];
   /** The option that will currently be rendered as the selected option */
   selectedOption?: string;
+  /** Output (speaker) devices. Audio menu only. */
+  outputOptions?: MenuOptions[];
+  /** The output option currently rendered as selected */
+  selectedOutputOption?: string;
+  /** Picks an output device. Undefined disables the speaker section. */
+  onSelectOutput?: (id: string) => void;
   videoBlurToggleClick?: () => void;
   videoBlurEnabled?: boolean;
   /**
@@ -58,90 +75,240 @@ export interface MediaMuteAndSwitchButtonProps {
 
 const BLUR_ID = "blur";
 
+/** Id of the placeholder "Default" row, shown when the platform lists no outputs. */
+const DEFAULT_OUTPUT_ID = "default";
+
+/** Largest share of the call area's height the device list may take. */
+const LIST_SHARE_OF_CALL = 0.6;
+
+/** Smallest device list height in px, so a short call still shows more than one device. */
+const MIN_LIST_HEIGHT = 160;
+
 export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
-  title,
   enabled,
   busy,
   onMuteClick,
   iconsAndLabels,
   options,
   selectedOption,
+  outputOptions,
+  selectedOutputOption,
+  onSelectOutput,
   videoBlurEnabled,
   videoBlurToggleClick,
   onSelect,
 }) => {
-  const [plannedSelection, setPlannedSelection] = useState<string | null>(null);
+  // Requested but not yet selected. Keyed by kind too, since Chrome uses
+  // "default" for both an input and an output.
+  const [plannedSelection, setPlannedSelection] = useState<{
+    kind: "input" | "output";
+    id: string;
+  } | null>(null);
   const [menuOpen, setMenuOpen] = useState(false);
+  const onOpenChange = useCallback((open: boolean): void => {
+    setMenuOpen(open);
+    // Drop a request that never arrived.
+    if (!open) setPlannedSelection(null);
+  }, []);
   const isBusy = busy ?? false;
   const { t } = useTranslation();
   const devices = useMediaDevices();
 
+  /**
+   * Records on the menu whether the keyboard or the pointer moved focus, for
+   * the focus ring. `:focus-visible` can't tell: Radix focuses whatever the
+   * pointer is over. Listened for on the menu, not the document, so a second
+   * Element Call on the page doesn't answer for this one.
+   */
+  const trackFocusSource = useCallback(
+    (list: HTMLDivElement | null): (() => void) | undefined => {
+      const menu = list?.closest<HTMLElement>('[role="menu"]');
+      if (menu === null || menu === undefined) return;
+      const record = (source: "keyboard" | "pointer"): void => {
+        menu.dataset.focusSource = source;
+      };
+      record("pointer");
+      const usedKeyboard = (): void => record("keyboard");
+      const usedPointer = (): void => record("pointer");
+      menu.addEventListener("keydown", usedKeyboard, true);
+      menu.addEventListener("pointermove", usedPointer, true);
+      return (): void => {
+        menu.removeEventListener("keydown", usedKeyboard, true);
+        menu.removeEventListener("pointermove", usedPointer, true);
+      };
+    },
+    [],
+  );
+
+  // Measured on the call area: CSS can't size the portalled menu against it.
+  const rootElement = useRootElement();
+  const [listMaxHeight, setListMaxHeight] = useState<number>();
+  useEffect(() => {
+    if (!menuOpen) return;
+    // Followed, since a host can resize the call while the menu is open.
+    const subscription = observeElementSize$(rootElement)
+      .pipe(
+        map(({ height }) =>
+          Math.max(MIN_LIST_HEIGHT, Math.round(height * LIST_SHARE_OF_CALL)),
+        ),
+        distinctUntilChanged(),
+      )
+      .subscribe(setListMaxHeight);
+    return (): void => subscription.unsubscribe();
+  }, [menuOpen, rootElement]);
+
+  // Kept clear at the list's foot, so a row reached by keyboard isn't under
+  // the meter.
+  const [meterHeight, meter] = useMeasuredHeight();
+
+  // Likewise at its head, for the sticky headings.
+  const [headingHeight, heading] = useMeasuredHeight();
+
   useEffect(() => {
     if (menuOpen) devices.requestDeviceNames(); // No-op after the first call
   }, [menuOpen, devices]);
 
-  let button;
+  const MuteButton = iconsAndLabels === "audio" ? MicButton : VideoButton;
-  let toggles: { label: string; enabled: boolean; id: string }[] = [];
+  const button = (
-  switch (iconsAndLabels) {
+    <MuteButton
-    case "video":
+      enabled={enabled ?? false}
-      button = (
+      busy={isBusy}
-        <VideoButton
+      onClick={(e) => {
-          enabled={enabled ?? false}
+        onMuteClick?.();
-          busy={isBusy}
+        e.preventDefault();
-          onClick={(e) => {
+        e.stopPropagation();
-            onMuteClick?.();
+      }}
-            e.preventDefault();
+      disabled={isBusy || onMuteClick === undefined}
-            e.stopPropagation();
+      data-testid={
-          }}
+        iconsAndLabels === "audio" ? "incall_mute" : "incall_videomute"
-          disabled={isBusy || onMuteClick === undefined}
+      }
-          data-testid="incall_videomute"
+    />
-        />
+  );
-      );
+
-      if (videoBlurToggleClick !== undefined) {
+  const toggles =
-        toggles = [
+    iconsAndLabels === "video" && videoBlurToggleClick !== undefined
+      ? [
           {
             label: t("action.blur_background"),
             enabled: videoBlurEnabled ?? false,
             id: BLUR_ID,
           },
-        ];
+        ]
-      }
+      : [];
-      break;
-    case "audio":
-      button = (
-        <MicButton
-          enabled={enabled ?? false}
-          busy={isBusy}
-          onClick={(e) => {
-            onMuteClick?.();
-            e.preventDefault();
-            e.stopPropagation();
-          }}
-          disabled={isBusy || onMuteClick === undefined}
-          data-testid="incall_mute"
-        />
-      );
-      break;
-  }
 
-  let IconOptions: ComponentType<React.SVGAttributes<SVGElement>> | undefined;
   let optionsButtonLabel: string;
+  let menuTitle: string;
   let numberedLabel: (number: number) => string;
   switch (iconsAndLabels) {
     case "video":
-      IconOptions = VideoCallIcon;
       optionsButtonLabel = t("settings.devices.camera");
+      menuTitle = t("settings.devices.camera_source");
       numberedLabel = (n): string =>
         t("settings.devices.camera_numbered", { n });
       break;
     case "audio":
-      IconOptions = MicOnIcon;
       optionsButtonLabel = t("settings.devices.microphone");
+      menuTitle = t("settings.devices.mic_source");
       numberedLabel = (n): string =>
         t("settings.devices.microphone_numbered", { n });
       break;
   }
 
+  const labelText = (
+    label: MenuOptions["label"],
+    numbered: (n: number) => string,
+  ): string => {
+    switch (label.type) {
+      case "name":
+        return label.name;
+      case "number":
+        return numbered(label.number);
+      case "default":
+        return label.name === null
+          ? t("settings.devices.default")
+          : t("settings.devices.default_named_plain", { name: label.name });
+      case "speaker":
+        return t("settings.devices.loudspeaker");
+      case "earpiece":
+        return t("settings.devices.handset");
+    }
+  };
+
+  // Nothing can be picked while a requested device is on offer but not yet
+  // selected, so a second request can't overtake it.
+  const plannedOutput = plannedSelection?.kind === "output";
+  const selectedOfPlannedKind = plannedOutput
+    ? selectedOutputOption
+    : selectedOption;
+  const offeredOfPlannedKind = plannedOutput ? outputOptions : options;
+  const settling =
+    plannedSelection !== null &&
+    plannedSelection.id !== selectedOfPlannedKind &&
+    offeredOfPlannedKind?.some(({ id }) => id === plannedSelection.id) === true;
+
+  // Safari lists no outputs: show a disabled, selected Default rather than an
+  // empty section.
+  const noOutputsListed = outputOptions?.length === 0;
+  const speakerOptions: MenuOptions[] | undefined = noOutputsListed
+    ? [{ id: DEFAULT_OUTPUT_ID, label: { type: "default", name: null } }]
+    : outputOptions;
+  const selectedSpeaker = noOutputsListed
+    ? DEFAULT_OUTPUT_ID
+    : selectedOutputOption;
+
+  const deviceItems = (
+    kind: "input" | "output",
+    items: MenuOptions[] | undefined,
+    selected: string | undefined,
+    select: ((id: string) => void) | undefined,
+    numbered: (n: number) => string,
+  ): ReactElement[] => {
+    const list = items ?? [];
+    // Disabled rather than hidden, so the menu keeps its shape.
+    const disabled = select === undefined || list.length <= 1 || settling;
+    return list.map(({ label, id }) => (
+      <MenuItem
+        // A radio input may not sit inside a button.
+        as="div"
+        hideChevron
+        disabled={disabled}
+        label={labelText(label, numbered)}
+        Icon={
+          // Inert, not aria-hidden: aria-hidden alone leaves it focusable.
+          <span inert>
+            <RadioInput
+              checked={selected === id}
+              disabled={disabled}
+              // Not readOnly, which mutes the selected fill. The item handles
+              // the click.
+              onChange={(): void => {}}
+            />
+          </span>
+        }
+        onSelect={(e) => {
+          e.preventDefault();
+          if (id === selected) return;
+          setPlannedSelection({ kind, id });
+          select?.(id);
+        }}
+        key={id}
+        role="menuitemradio"
+        aria-checked={selected === id}
+      >
+        {selected !== id &&
+          plannedSelection?.kind === kind &&
+          plannedSelection.id === id && (
+            <SpinnerIcon
+              width={24}
+              height={24}
+              className={styles.rotate}
+              aria-label={t("settings.devices.activating")}
+            />
+          )}
+      </MenuItem>
+    ));
+  };
+
   return (
     <div
       className={classNames({
@@ -152,10 +319,12 @@ export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
       {/* The mute button lives inside */}
       {button}
       <Menu
-        title={title}
+        className={styles.menu}
-        showTitle={true}
+        // Named for screen readers only: each section has its own heading.
+        title={menuTitle}
+        showTitle={false}
         open={menuOpen}
-        onOpenChange={setMenuOpen}
+        onOpenChange={onOpenChange}
         side="top"
         trigger={
           <Button
@@ -171,67 +340,74 @@ export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
           />
         }
       >
-        {options?.map(({ label, id }) => {
+        <div
-          let labelText: string;
+          ref={trackFocusSource}
-          switch (label.type) {
+          // Keeps the items the menu's own children for assistive tech.
-            case "name":
+          role="none"
-              labelText = label.name;
+          className={styles.deviceList}
-              break;
+          style={
-            case "number":
+            {
-              labelText = numberedLabel(label.number);
+              "--device-list-max-height":
-              break;
+                listMaxHeight === undefined ? undefined : `${listMaxHeight}px`,
+              "--device-list-scroll-padding-end":
+                meterHeight === undefined ? undefined : `${meterHeight}px`,
+              "--device-list-scroll-padding-start":
+                headingHeight === undefined ? undefined : `${headingHeight}px`,
+            } as CSSProperties
           }
-          return (
+        >
-            <MenuItem
+          {iconsAndLabels === "audio" && speakerOptions && (
-              hideChevron
+            <>
-              label={labelText}
+              {/* A menu may only contain items, separators and groups, so each
-              Icon={
+                  heading is a hidden part of a named group. */}
-                IconOptions && (
+              <div role="group" aria-label={t("settings.devices.speaker")}>
-                  <IconOptions
+                <div aria-hidden className={styles.sectionHeading}>
-                    width={24}
+                  <MenuTitle title={t("settings.devices.speaker")} />
-                    height={24}
+                </div>
-                    className={styles.itemIcon}
+                {deviceItems(
-                    aria-hidden
+                  "output",
-                  />
+                  speakerOptions,
-                )
+                  selectedSpeaker,
-              }
+                  onSelectOutput,
-              onSelect={(e) => {
+                  (n) => t("settings.devices.speaker_numbered", { n }),
-                e.preventDefault();
+                )}
-                if (id === selectedOption) return;
+              </div>
-                setPlannedSelection(id);
+            </>
-                onSelect?.(id);
+          )}
-              }}
+          <div role="group" aria-label={optionsButtonLabel}>
-              key={id}
+            <div ref={heading} aria-hidden className={styles.sectionHeading}>
-              role="menuitemradio"
+              <MenuTitle title={optionsButtonLabel} />
-              aria-checked={selectedOption === id}
+            </div>
-            >
+            {/* Apart from the heading, so the sticky meter can't ride over it. */}
-              {selectedOption === id && (
+            <div role="none">
-                <CheckIcon
+              {deviceItems(
-                  width={24}
+                "input",
-                  height={24}
+                options,
-                  aria-hidden // A label would be redundant to aria-checked above
+                selectedOption,
+                onSelect,
+                numberedLabel,
+              )}
+              {iconsAndLabels === "audio" && (
+                <LiveMicrophoneLevelMeter
+                  ref={meter}
+                  deviceId={selectedOption}
+                  // Only while open, so the microphone isn't held all call.
+                  active={menuOpen}
+                  className={styles.stickyMeter}
                 />
               )}
-              {selectedOption !== id && plannedSelection === id && (
+            </div>
-                <SpinnerIcon
+          </div>
-                  width={24}
+        </div>
-                  height={24}
+        {toggles.length > 0 && <hr />}
-                  className={styles.rotate}
+        {toggles.map((toggle) => (
-                  aria-label={t("settings.devices.activating")}
-                />
-              )}
-            </MenuItem>
-          );
-        })}
-        {(toggles?.length ?? 0) > 0 && <hr />}
-        {toggles?.map((toggle) => (
           <ToggleMenuItem
             label={toggle.label}
             onSelect={(e) => {
               videoBlurToggleClick?.();
               e.preventDefault();
             }}
-            checked={toggle.enabled ?? false}
+            checked={toggle.enabled}
             key={toggle.id}
           />
         ))}
@@ -239,3 +415,25 @@ export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
     </div>
   );
 };
+
+/** Follows an element's height. */
+function useMeasuredHeight(): [
+  number | undefined,
+  (element: HTMLElement | null) => (() => void) | undefined,
+] {
+  const [height, setHeight] = useState<number>();
+  const ref = useCallback(
+    (element: HTMLElement | null): (() => void) | undefined => {
+      if (element === null) return;
+      const subscription = observeElementSize$(element)
+        .pipe(
+          map((size) => size.height),
+          distinctUntilChanged(),
+        )
+        .subscribe(setHeight);
+      return (): void => subscription.unsubscribe();
+    },
+    [],
+  );
+  return [height, ref];
+}

src/components/MicrophoneLevelMeter.module.css

@@ -0,0 +1,65 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+.meter {
+  /* A device row's icon column, so the bars start where the names do. */
+  --meter-icon-size: 24px;
+
+  /* Compound's radio size, whose centre line the icon shares. */
+  --device-control-size: 20px;
+
+  display: flex;
+  align-items: center;
+  gap: var(--cpd-space-3x);
+  padding-block: var(--cpd-space-2x);
+  /* Centres the icon on the radio column: less the row's inset border and half
+     the icon's extra width. Checked in the MeterAlignsWithTheDeviceRows story. */
+  padding-inline-start: calc(
+    var(--cpd-space-4x) - var(--cpd-border-width-1) -
+      (var(--meter-icon-size) - var(--device-control-size)) / 2
+  );
+  padding-inline-end: calc(var(--cpd-space-4x) * 2 + var(--cpd-space-2x));
+}
+
+.icon {
+  color: var(--cpd-color-icon-secondary);
+  flex-shrink: 0;
+  inline-size: var(--meter-icon-size);
+  block-size: var(--meter-icon-size);
+}
+
+.segments {
+  /* Bars keep one size and the width decides how many; the component reads the
+     sizes back from here. */
+  flex: 1;
+  /* So the bars never set the menu's width. */
+  contain: inline-size;
+  min-inline-size: 0;
+  display: flex;
+  align-items: center;
+  /* Half again a bar's width, per the design. */
+  gap: var(--cpd-space-1-5x);
+}
+
+.segment {
+  flex: none;
+  inline-size: var(--cpd-space-1x);
+  block-size: var(--cpd-space-4x);
+  border-radius: var(--cpd-space-1x);
+  background: var(--cpd-color-bg-subtle-primary);
+}
+
+/* The count of lit bars carries the level as well as their colour. */
+.segmentLit {
+  background: var(--cpd-color-bg-accent-rest);
+}
+
+.message {
+  color: var(--cpd-color-text-secondary);
+  /* A paragraph's margin would lift the text off centre. */
+  margin-block: 0;
+}

src/components/MicrophoneLevelMeter.stories.tsx

@@ -0,0 +1,161 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { expect, within } from "storybook/test";
+import { type JSX } from "react";
+
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import {
+  MicrophoneLevelMeter,
+  type MicrophoneLevelMeterProps,
+} from "./MicrophoneLevelMeter";
+import styles from "./MicrophoneLevelMeter.module.css";
+import { LEVEL_SCALE } from "../state/MicrophoneLevel";
+import { constant } from "../state/Behavior";
+
+/** Roughly the menu's width. It only decides how many bars fit. */
+const STORY_WIDTH = 256;
+
+const meta = {
+  component: MicrophoneLevelMeter,
+  decorators: [
+    (Story): JSX.Element => (
+      <div style={{ inlineSize: STORY_WIDTH }}>
+        <Story />
+      </div>
+    ),
+  ],
+  argTypes: {
+    state: {
+      description:
+        "What the selected microphone can say about itself: a level, or a reason there is none.",
+    },
+  },
+} satisfies Meta<typeof MicrophoneLevelMeter>;
+
+export default meta;
+type Story = StoryObj<typeof meta>;
+
+/** A quiet room: hiss below the noise floor lights nothing. */
+export const Silent: Story = {
+  args: { state: { type: "level", level$: constant(0) } },
+  play: async ({ canvasElement }) => {
+    await expect(litSegments(canvasElement)).toBe(0);
+  },
+};
+
+export const QuietSpeech: Story = {
+  args: { state: { type: "level", level$: constant(5) } },
+};
+
+export const NormalSpeech: Story = {
+  args: { state: { type: "level", level$: constant(12) } },
+  play: async ({ canvasElement }) => {
+    // A floor, not a count: the count follows from the design's bar and gap sizes.
+    await expect(
+      canvasElement.getElementsByClassName(styles.segment).length,
+    ).toBeGreaterThanOrEqual(15);
+  },
+};
+
+export const LoudSpeech: Story = {
+  args: { state: { type: "level", level$: constant(LEVEL_SCALE) } },
+};
+
+/** The three volumes differ in how many bars are lit, not only in colour. */
+export const VolumesAreDistinguishable: Story = {
+  args: { state: { type: "level", level$: constant(5) } },
+  play: async ({ canvasElement, mount }) => {
+    const lit: number[] = [];
+    for (const level of [5, 12, LEVEL_SCALE]) {
+      await mount(
+        <MicrophoneLevelMeter
+          state={{ type: "level", level$: constant(level) }}
+        />,
+      );
+      lit.push(litSegments(canvasElement));
+      await expect(within(canvasElement).getByRole("meter")).toHaveAttribute(
+        "aria-valuenow",
+        String(level),
+      );
+    }
+    await expect(new Set(lit).size).toBe(lit.length);
+    await expect(lit).toEqual([...lit].sort((a, b) => a - b));
+  },
+};
+
+/** Permission refused: a message with a next action, not a still meter. */
+export const PermissionDenied: Story = {
+  args: { state: { type: "permission-denied" } },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await expect(canvas.queryByRole("meter")).toBeNull();
+    await expect(
+      canvas.getByText(/Microphone access is blocked/),
+    ).toBeVisible();
+  },
+};
+
+/** No input device, told apart from a refusal. */
+export const NoDevice: Story = {
+  args: { state: { type: "no-device" } },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await expect(canvas.queryByRole("meter")).toBeNull();
+    await expect(canvas.getByText(/No microphone found/)).toBeVisible();
+
+    // The icon sits on the middle of the text, however many lines it runs to.
+    const middle = (element: Element): number => {
+      const box = element.getBoundingClientRect();
+      return box.top + box.height / 2;
+    };
+    const icon = canvasElement.getElementsByClassName(styles.icon)[0];
+    const words = canvasElement.getElementsByClassName(styles.message)[0];
+    await expect(Math.abs(middle(icon) - middle(words))).toBeLessThanOrEqual(1);
+  },
+};
+
+/** The same meter at two widths: the bars keep their size and only their count changes. */
+export const ShapeStaysTheSameAtAnyWidth: Story = {
+  args: { state: { type: "level", level$: constant(12) } },
+  play: async ({ mount, args }) => {
+    const narrow = await measureAt(mount, args, 180);
+    const wide = await measureAt(mount, args, 400);
+
+    await expect(narrow.bar).toBe(wide.bar);
+    await expect(narrow.gap).toBe(wide.gap);
+    await expect(narrow.count).toBeLessThan(wide.count);
+    // The bars are still separate, not one run of colour.
+    await expect(narrow.gap).toBeGreaterThan(0);
+  },
+};
+
+/** How many bars are lit. */
+function litSegments(canvasElement: HTMLElement): number {
+  return canvasElement.getElementsByClassName(styles.segmentLit).length;
+}
+
+/** Renders the meter at one width and reports its bars' shape. */
+async function measureAt(
+  mount: (ui: JSX.Element) => Promise<unknown>,
+  args: MicrophoneLevelMeterProps,
+  width: number,
+): Promise<{ count: number; bar: number; gap: number }> {
+  await mount(
+    <div style={{ inlineSize: width }}>
+      <MicrophoneLevelMeter {...args} />
+    </div>,
+  );
+  const bars = Array.from(document.body.getElementsByClassName(styles.segment));
+  const first = bars[0].getBoundingClientRect();
+  const second = bars[1].getBoundingClientRect();
+  return {
+    count: bars.length,
+    bar: first.width,
+    gap: second.left - first.right,
+  };
+}

src/components/MicrophoneLevelMeter.test.tsx

@@ -0,0 +1,42 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { describe, expect, test } from "vitest";
+import { render, screen } from "@testing-library/react";
+
+import { MicrophoneLevelMeter } from "./MicrophoneLevelMeter";
+import { LEVEL_SCALE } from "../state/MicrophoneLevel";
+import { constant } from "../state/Behavior";
+
+describe("MicrophoneLevelMeter", () => {
+  test("announces the level rather than relying on hue", () => {
+    render(
+      <MicrophoneLevelMeter state={{ type: "level", level$: constant(6) }} />,
+    );
+
+    const meter = screen.getByRole("meter", { name: "Microphone level" });
+    expect(meter).toHaveAttribute("aria-valuenow", "6");
+    expect(meter).toHaveAttribute("aria-valuemax", String(LEVEL_SCALE));
+    expect(meter).toHaveAttribute("aria-valuetext", `6 of ${LEVEL_SCALE}`);
+  });
+
+  test("shows distinct messages for denied permission and no input device", () => {
+    const denied = render(
+      <MicrophoneLevelMeter state={{ type: "permission-denied" }} />,
+    );
+    expect(
+      denied.getByText(/Microphone access is blocked/),
+    ).toBeInTheDocument();
+    expect(denied.queryByRole("meter")).toBeNull();
+
+    const missing = render(
+      <MicrophoneLevelMeter state={{ type: "no-device" }} />,
+    );
+    expect(missing.getByText(/No microphone found/)).toBeInTheDocument();
+    expect(missing.queryByRole("meter")).toBeNull();
+  });
+});

src/components/MicrophoneLevelMeter.tsx

@@ -0,0 +1,146 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import {
+  useCallback,
+  useLayoutEffect,
+  useRef,
+  useState,
+  type FC,
+  type Ref,
+} from "react";
+import { Text } from "@vector-im/compound-web";
+import { MicOnIcon } from "@vector-im/compound-design-tokens/assets/web/icons";
+import classNames from "classnames";
+import { useTranslation } from "react-i18next";
+
+import { distinctUntilChanged, map } from "rxjs";
+
+import styles from "./MicrophoneLevelMeter.module.css";
+import { LEVEL_SCALE, type MicrophoneState } from "../state/MicrophoneLevel";
+import { observeElementSize$ } from "../utils/elementSize";
+import { useMicrophoneLevel } from "./useMicrophoneLevel";
+
+export interface LiveMicrophoneLevelMeterProps {
+  /** The microphone to listen to. */
+  deviceId: string | undefined;
+  /** Whether to hold a capture at all. */
+  active: boolean;
+  className?: string;
+  ref?: Ref<HTMLDivElement>;
+}
+
+/**
+ * The meter, wired to a live capture. Its own component so a changing level
+ * re-renders the meter, not its parent.
+ */
+export const LiveMicrophoneLevelMeter: FC<LiveMicrophoneLevelMeterProps> = ({
+  deviceId,
+  active,
+  className,
+  ref,
+}) => {
+  const state = useMicrophoneLevel(deviceId, active);
+  return <MicrophoneLevelMeter state={state} className={className} ref={ref} />;
+};
+
+export interface MicrophoneLevelMeterProps {
+  state: MicrophoneState;
+  className?: string;
+  ref?: Ref<HTMLDivElement>;
+}
+
+/** The input level of a microphone, or why there is none. */
+export const MicrophoneLevelMeter: FC<MicrophoneLevelMeterProps> = ({
+  state,
+  className,
+  ref,
+}) => {
+  const { t } = useTranslation();
+  // Bars keep one size, so their count follows the width. Starts full so the
+  // first paint, and jsdom, draw a whole meter.
+  const [barCount, setBarCount] = useState(LEVEL_SCALE);
+  const segments = useRef<HTMLDivElement | null>(null);
+  const track = useCallback(
+    (element: HTMLDivElement | null): (() => void) | undefined => {
+      if (element === null) return;
+      segments.current = element;
+      const subscription = observeElementSize$(element)
+        .pipe(
+          map(({ width }) => barsThatFit(element, width)),
+          distinctUntilChanged(),
+        )
+        .subscribe(setBarCount);
+      return (): void => {
+        subscription.unsubscribe();
+        segments.current = null;
+      };
+    },
+    [],
+  );
+
+  // Drawn straight into the DOM: the level changes many times a second, and
+  // re-rendering for each change is what this avoids.
+  useLayoutEffect(() => {
+    const element = segments.current;
+    if (state.type !== "level" || element === null) return;
+    const subscription = state.level$.subscribe((level) => {
+      element.setAttribute("aria-valuenow", String(level));
+      element.setAttribute(
+        "aria-valuetext",
+        t("microphone_level.value", { level, max: LEVEL_SCALE }),
+      );
+      // The level is a share of the scale, not a bar count.
+      const lit = Math.round((level / LEVEL_SCALE) * barCount);
+      Array.from(element.children).forEach((bar, i) =>
+        bar.classList.toggle(styles.segmentLit, i < lit),
+      );
+    });
+    return (): void => subscription.unsubscribe();
+  }, [state, barCount, t]);
+
+  return (
+    <div ref={ref} className={classNames(styles.meter, className)}>
+      <MicOnIcon className={styles.icon} aria-hidden />
+      {state.type !== "level" ? (
+        <Text size="sm" className={styles.message}>
+          {state.type === "permission-denied"
+            ? t("microphone_level.permission_denied")
+            : t("microphone_level.no_device")}
+        </Text>
+      ) : (
+        <div
+          ref={track}
+          className={styles.segments}
+          role="meter"
+          aria-label={t("microphone_level.label")}
+          aria-valuemin={0}
+          aria-valuemax={LEVEL_SCALE}
+          // The first paint's value; the effect above keeps it current.
+          aria-valuenow={state.level$.value}
+          aria-valuetext={t("microphone_level.value", {
+            level: state.level$.value,
+            max: LEVEL_SCALE,
+          })}
+        >
+          {Array.from({ length: barCount }, (_, i) => (
+            <span key={i} aria-hidden className={styles.segment} />
+          ))}
+        </div>
+      )}
+    </div>
+  );
+};
+
+/** How many bars fit across `width`, measured so the stylesheet alone sets their size. */
+function barsThatFit(track: HTMLElement, width: number): number {
+  const gap = Number.parseFloat(getComputedStyle(track).columnGap);
+  const bar = track.firstElementChild?.getBoundingClientRect().width ?? 0;
+  // No layout (jsdom): keep the full count.
+  if (!(bar > 0) || !(gap >= 0)) return LEVEL_SCALE;
+  return Math.max(1, Math.floor((width + gap) / (bar + gap)));
+}

src/components/useMicrophoneLevel.test.tsx

@@ -0,0 +1,41 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { afterEach, describe, expect, test } from "vitest";
+import { renderHook } from "@testing-library/react";
+
+import { useMicrophoneLevel } from "./useMicrophoneLevel";
+import { restoreAudioCapture, stubAudioCapture } from "../utils/test";
+
+// Capture and release are covered in MicrophoneLevel.test.ts; this covers the bridge.
+describe("useMicrophoneLevel", () => {
+  afterEach(restoreAudioCapture);
+
+  test("holds no capture while the meter is not shown", () => {
+    const capture = stubAudioCapture();
+
+    renderHook(() => useMicrophoneLevel("mic1", false));
+
+    expect(capture.getUserMedia).not.toHaveBeenCalled();
+  });
+
+  test("starts from nothing rather than the previous device's level", () => {
+    const capture = stubAudioCapture();
+
+    const { result, rerender } = renderHook(
+      ({ id }: { id: string }) => useMicrophoneLevel(id, true),
+      { initialProps: { id: "mic1" } },
+    );
+    capture.grant();
+
+    rerender({ id: "mic2" });
+
+    // No level carried over from the previous device.
+    const state = result.current;
+    expect(state.type === "level" ? state.level$.value : state.type).toBe(0);
+  });
+});

src/components/useMicrophoneLevel.ts

@@ -0,0 +1,34 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { useEffect, useState } from "react";
+
+import {
+  type MicrophoneState,
+  observeMicrophoneState$,
+} from "../state/MicrophoneLevel";
+import { constant } from "../state/Behavior";
+
+const IDLE: MicrophoneState = { type: "level", level$: constant(0) };
+
+/** The live level of a microphone, captured only while `active`. */
+export function useMicrophoneLevel(
+  deviceId: string | undefined,
+  active: boolean,
+): MicrophoneState {
+  const [state, setState] = useState<MicrophoneState>(IDLE);
+
+  useEffect(() => {
+    if (!active) return;
+    // Idle first, so a new device doesn't start from the previous level.
+    setState(IDLE);
+    const subscription = observeMicrophoneState$(deviceId).subscribe(setState);
+    return (): void => subscription.unsubscribe();
+  }, [deviceId, active]);
+
+  return state;
+}

src/room/LobbyView.test.tsx

@@ -5,8 +5,10 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { describe, expect, it, vi } from "vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
-import { render } from "@testing-library/react";
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { of } from "rxjs";
 import { LeaveToHomeProvider } from "../LeaveToHomeContext";
 import { TooltipProvider } from "@vector-im/compound-web";
 import { type MatrixClient } from "matrix-js-sdk";
@@ -18,7 +20,13 @@ import {
 
 import { LobbyView } from "./LobbyView";
 import { E2eeType } from "../e2ee/e2eeType";
-import { mockMediaDevices, mockMuteStates } from "../utils/test";
+import {
+  mockMediaDevices,
+  mockMuteStates,
+  restoreAudioCapture,
+  stubAudioCapture,
+} from "../utils/test";
+import { type MediaDevices } from "../state/MediaDevices";
 import { MediaDevicesContext } from "../MediaDevicesContext";
 import { type ProcessorState } from "../livekit/TrackProcessorContext";
 import { type EncryptionSystem } from "../e2ee/sharedKeyManagement";
@@ -77,9 +85,10 @@ function renderLobbyView(
   props: Partial<Parameters<typeof LobbyView>[0]> = {},
   withAppBar = false,
   platform = "android",
+  devices: Partial<MediaDevices> = {},
 ): ReturnType<typeof render> {
   platformMock.mockReturnValue(platform);
-  const mediaDevices = mockMediaDevices({});
+  const mediaDevices = mockMediaDevices(devices);
   const muteStates = mockMuteStates();
   const hideHeader = withAppBar ? true : false;
   const lobbyView = (
@@ -178,3 +187,30 @@ describe("LobbyView", () => {
     expect(await axe(container)).toHaveNoViolations();
   });
 });
+
+describe("LobbyView microphone level", () => {
+  afterEach(restoreAudioCapture);
+
+  it("shows the microphone level meter", async () => {
+    const capture = stubAudioCapture();
+    capture.grant();
+    const user = userEvent.setup();
+    const { getByRole } = renderLobbyView({}, false, "desktop", {
+      requestDeviceNames: (): void => {},
+      audioInput: {
+        available$: of(
+          new Map([["mic1", { type: "name", name: "Microphone 1" }]]),
+        ),
+        selected$: of({ id: "mic1" }),
+        select: (): void => {},
+      },
+    } as unknown as Partial<MediaDevices>);
+
+    // Pre-join reaches the meter through the same chevron as a call.
+    await user.click(getByRole("button", { name: "Microphone" }));
+
+    expect(
+      await screen.findByRole("meter", { name: "Microphone level" }),
+    ).toBeInTheDocument();
+  });
+});

src/state/MediaDevices.test.ts

@@ -5,8 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { describe, expect, test, vi } from "vitest";
+import { afterEach, describe, expect, test, vi } from "vitest";
-import { of } from "rxjs";
 
 const getPlatform = vi.hoisted(() => vi.fn(() => "desktop"));
 vi.mock("../Platform", () => ({
@@ -15,9 +14,22 @@ vi.mock("../Platform", () => ({
   },
   isFirefox: (): boolean => false,
 }));
-vi.mock("@livekit/components-core", () => ({
+const observers = vi.hoisted(
-  createMediaDeviceObserver: () => of([]),
+  () => new Map<string, { next: (devices: unknown[]) => void }>(),
-}));
+);
+vi.mock("@livekit/components-core", async () => {
+  const { BehaviorSubject: Subject } = await import("rxjs");
+  return {
+    createMediaDeviceObserver: (kind: string) => {
+      let observer = observers.get(kind);
+      if (observer === undefined) {
+        observer = new Subject<unknown[]>([]);
+        observers.set(kind, observer);
+      }
+      return observer;
+    },
+  };
+});
 
 import { AudioOutput, MediaDevices } from "./MediaDevices";
 import { AndroidControlledAudioOutput } from "./AndroidControlledAudioOutput";
@@ -57,3 +69,125 @@ describe("MediaDevices audio output", () => {
     expect(devices.audioOutput).toBeInstanceOf(IOSControlledAudioOutput);
   });
 });
+
+function device(deviceId: string, label: string, groupId = deviceId): object {
+  return { deviceId, label, groupId, kind: "audioinput" };
+}
+
+/** Replaces the devices of one kind, as the browser reports them. */
+function setDevices(kind: string, devices: object[]): void {
+  const observer = observers.get(kind);
+  if (observer === undefined) throw new Error(`nothing observing ${kind}`);
+  observer.next(devices);
+}
+
+function newMediaDevices(): MediaDevices {
+  return new MediaDevices(new ObservableScope(), {
+    controlledAudioDevices: false,
+  });
+}
+
+describe("MediaDevices selection", () => {
+  afterEach(() => {
+    localStorage.clear();
+    for (const kind of observers.keys()) setDevices(kind, []);
+  });
+
+  test("persists the selected device across sessions", () => {
+    const devices = newMediaDevices();
+    setDevices("audioinput", [
+      device("mic1", "Microphone 1"),
+      device("mic2", "Microphone 2"),
+    ]);
+
+    devices.audioInput.select("mic2");
+
+    // A later call reads the same stored preference.
+    expect(newMediaDevices().audioInput.selected$.value?.id).toBe("mic2");
+  });
+
+  test("updates the available devices when hardware changes", () => {
+    const devices = newMediaDevices();
+    setDevices("audioinput", [device("mic1", "Microphone 1")]);
+    expect([...devices.audioInput.available$.value.keys()]).toEqual(["mic1"]);
+
+    setDevices("audioinput", [
+      device("mic1", "Microphone 1"),
+      device("mic2", "Headset"),
+    ]);
+    expect([...devices.audioInput.available$.value.keys()]).toEqual([
+      "mic1",
+      "mic2",
+    ]);
+
+    setDevices("audioinput", [device("mic1", "Microphone 1")]);
+    expect([...devices.audioInput.available$.value.keys()]).toEqual(["mic1"]);
+  });
+
+  test("falls back to the default device when the selected device disappears", () => {
+    const devices = newMediaDevices();
+    setDevices("audioinput", [
+      device("mic1", "Microphone 1"),
+      device("mic2", "Headset"),
+    ]);
+    devices.audioInput.select("mic2");
+    expect(devices.audioInput.selected$.value?.id).toBe("mic2");
+
+    setDevices("audioinput", [device("mic1", "Microphone 1")]);
+
+    expect(devices.audioInput.selected$.value?.id).toBe("mic1");
+  });
+
+  test("falls back when the remembered device is absent", () => {
+    const devices = newMediaDevices();
+    setDevices("audioinput", [device("mic1", "Microphone 1")]);
+    devices.audioInput.select("a-device-from-last-time");
+
+    expect(devices.audioInput.selected$.value?.id).toBe("mic1");
+  });
+
+  test("falls back to numbered labels when labels are unavailable", () => {
+    const devices = newMediaDevices();
+    // Names are withheld until permission is granted.
+    setDevices("audioinput", [device("mic1", ""), device("mic2", "")]);
+
+    expect([...devices.audioInput.available$.value.values()]).toEqual([
+      { type: "number", number: 1 },
+      { type: "number", number: 2 },
+    ]);
+  });
+
+  test("lists Default as a distinct entry", () => {
+    const devices = newMediaDevices();
+    setDevices("audiooutput", [device("spk1", "Speakers")]);
+
+    const available = devices.audioOutput.available$.value;
+    // Default is its own entry, unnamed: which device it resolves to isn't knowable.
+    expect(available.get("spk1")).toEqual({ type: "name", name: "Speakers" });
+    expect(available.get("")).toEqual({ type: "default", name: null });
+  });
+
+  test("selecting one device kind leaves the others unchanged", () => {
+    const devices = newMediaDevices();
+    setDevices("audioinput", [
+      device("mic1", "Microphone 1"),
+      device("mic2", "Headset"),
+    ]);
+    setDevices("audiooutput", [
+      device("spk1", "Speakers"),
+      device("spk2", "Headset"),
+    ]);
+    setDevices("videoinput", [device("cam1", "Camera 1")]);
+
+    devices.audioOutput.select("spk2");
+    const audioInputBefore = devices.audioInput.selected$.value?.id;
+    const videoInputBefore = devices.videoInput.selected$.value?.id;
+
+    devices.audioInput.select("mic2");
+
+    expect(devices.audioOutput.selected$.value?.id).toBe("spk2");
+    expect(devices.videoInput.selected$.value?.id).toBe(videoInputBefore);
+    expect(audioInputBefore).not.toBe("mic2");
+    expect(devices.audioInput.selected$.value?.id).toBe("mic2");
+  });
+});

src/state/MicrophoneLevel.test.ts

@@ -0,0 +1,183 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { afterEach, describe, expect, test, vi } from "vitest";
+
+import {
+  ATTACK_MS,
+  LEVEL_SCALE,
+  observeMicrophoneState$,
+  RELEASE_MS,
+  segmentsForVolume,
+  smoothVolume,
+} from "./MicrophoneLevel";
+import { restoreAudioCapture, stubAudioCapture } from "../utils/test";
+
+describe("segmentsForVolume", () => {
+  test("shows nothing for silence", () => {
+    expect(segmentsForVolume(0)).toBe(0);
+  });
+
+  test("shows nothing for the hiss of a quiet room", () => {
+    expect(segmentsForVolume(0.005)).toBe(0);
+    expect(segmentsForVolume(0.015)).toBe(0);
+  });
+
+  test("distinguishes quiet, normal and loud speech", () => {
+    const quiet = segmentsForVolume(0.06);
+    const normal = segmentsForVolume(0.2);
+    const loud = segmentsForVolume(0.8);
+
+    expect(quiet).toBeGreaterThan(0);
+    expect(normal).toBeGreaterThan(quiet);
+    expect(loud).toBeGreaterThan(normal);
+  });
+
+  test("moves the meter visibly for normal speech", () => {
+    // Ordinary speech reaches the middle of the meter.
+    expect(segmentsForVolume(0.2)).toBeGreaterThanOrEqual(LEVEL_SCALE / 4);
+  });
+
+  test("never exceeds the meter", () => {
+    expect(segmentsForVolume(1)).toBe(LEVEL_SCALE);
+    expect(segmentsForVolume(4)).toBe(LEVEL_SCALE);
+  });
+
+  test("treats a missing reading as silence", () => {
+    expect(segmentsForVolume(NaN)).toBe(0);
+    expect(segmentsForVolume(-1)).toBe(0);
+  });
+});
+
+describe("smoothVolume", () => {
+  test("rises faster than it falls", () => {
+    const rise = smoothVolume(0, 1, 50);
+    const fall = 1 - smoothVolume(1, 0, 50);
+
+    expect(rise).toBeGreaterThan(fall);
+  });
+
+  test("registers a syllable as it starts", () => {
+    // Most of the way within one attack time constant.
+    expect(smoothVolume(0, 1, ATTACK_MS)).toBeGreaterThan(0.6);
+  });
+
+  test("rides over the gaps between words", () => {
+    // A short pause doesn't collapse the meter...
+    expect(smoothVolume(1, 0, 30)).toBeGreaterThan(0.7);
+    // ...but a real silence brings it down.
+    expect(smoothVolume(1, 0, RELEASE_MS * 3)).toBeLessThan(0.1);
+  });
+
+  test("behaves the same whatever the frame rate", () => {
+    const oneStep = smoothVolume(0, 1, 32);
+    let twoSteps = smoothVolume(0, 1, 16);
+    twoSteps = smoothVolume(twoSteps, 1, 16);
+
+    expect(twoSteps).toBeCloseTo(oneStep, 5);
+  });
+
+  test("holds still when no time has passed", () => {
+    expect(smoothVolume(0.5, 1, 0)).toBe(0.5);
+  });
+});
+
+describe("observeMicrophoneState$", () => {
+  afterEach(restoreAudioCapture);
+
+  test("releases a capture the browser grants after nobody is watching", async () => {
+    const capture = stubAudioCapture();
+
+    const subscription = observeMicrophoneState$("mic1").subscribe();
+    // The menu closes before the browser hands the microphone over.
+    subscription.unsubscribe();
+    capture.grant();
+    await vi.waitFor(() => expect(capture.track.stop).toHaveBeenCalled());
+  });
+
+  test("releases the capture and the audio context when the subscription ends", async () => {
+    const capture = stubAudioCapture();
+
+    const subscription = observeMicrophoneState$("mic1").subscribe();
+    capture.grant();
+    await vi.waitFor(() => expect(capture.contexts).toHaveLength(1));
+
+    subscription.unsubscribe();
+
+    expect(capture.track.stop).toHaveBeenCalled();
+    expect(capture.contexts[0].close).toHaveBeenCalled();
+  });
+
+  test("gives the microphone back when the audio graph fails to build", async () => {
+    const capture = stubAudioCapture();
+    // Fails only after getUserMedia has granted the device.
+    vi.stubGlobal(
+      "AudioContext",
+      class {
+        public constructor() {
+          throw new Error("no audio context for you");
+        }
+      },
+    );
+
+    const seen: string[] = [];
+    const subscription = observeMicrophoneState$("mic1").subscribe((state) =>
+      seen.push(state.type),
+    );
+    capture.grant();
+
+    await vi.waitFor(() => expect(seen).toContain("no-device"));
+    expect(capture.track.stop).toHaveBeenCalled();
+
+    subscription.unsubscribe();
+  });
+
+  test("tells denied permission and a missing device apart", async () => {
+    for (const [name, expected] of [
+      ["NotAllowedError", "permission-denied"],
+      ["NotFoundError", "no-device"],
+    ] as const) {
+      const capture = stubAudioCapture();
+      capture.getUserMedia.mockRejectedValue(named(new Error(name), name));
+
+      const seen: string[] = [];
+      const subscription = observeMicrophoneState$("mic1").subscribe((state) =>
+        seen.push(state.type),
+      );
+      await vi.waitFor(() => expect(seen).toContain(expected));
+      subscription.unsubscribe();
+      restoreAudioCapture();
+    }
+  });
+
+  test("says nothing on a frame that did not change the level", async () => {
+    const capture = stubAudioCapture();
+
+    const states: string[] = [];
+    let levels = 0;
+    const subscription = observeMicrophoneState$("mic1").subscribe((state) => {
+      states.push(state.type);
+      if (state.type === "level") state.level$.subscribe(() => levels++);
+    });
+    capture.grant();
+    await vi.waitFor(() => expect(levels).toBe(1));
+
+    // Read every frame, but a steady signal emits once, and the state itself
+    // arrives only once.
+    capture.drawFrames(20);
+    expect(levels).toBe(1);
+    expect(states).toEqual(["level"]);
+
+    subscription.unsubscribe();
+  });
+});
+
+/** An error carrying the browser's `name`. */
+function named(error: Error, name: string): Error {
+  error.name = name;
+  return error;
+}

src/state/MicrophoneLevel.ts

@@ -0,0 +1,143 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { BehaviorSubject, Observable } from "rxjs";
+import { logger } from "matrix-js-sdk/lib/logger";
+
+import { type Behavior } from "./Behavior";
+
+/** What the microphone picks up, or why it can't be read. */
+export type MicrophoneState =
+  // A Behavior, so a changing level can be drawn without re-rendering.
+  | { type: "level"; level$: Behavior<number> }
+  | { type: "permission-denied" }
+  | { type: "no-device" };
+
+/** Scale a level is reported on. Fixed rather than the bar count, so a level reads the same at any width. */
+export const LEVEL_SCALE = 24;
+
+/**
+ * The level of a microphone, captured while subscribed. Its own capture rather
+ * than the call's track, because pre-join freezes that track to the device
+ * selected at mount.
+ */
+export function observeMicrophoneState$(
+  deviceId: string | undefined,
+): Observable<MicrophoneState> {
+  return new Observable<MicrophoneState>((subscriber) => {
+    let stream: MediaStream | undefined;
+    let context: AudioContext | undefined;
+    let frame: number | undefined;
+    let level: BehaviorSubject<number> | undefined;
+
+    // Idempotent: teardown and start can both call it.
+    const release = (): void => {
+      if (frame !== undefined) cancelAnimationFrame(frame);
+      stream?.getTracks().forEach((track) => track.stop());
+      void context?.close();
+      frame = undefined;
+      stream = undefined;
+      context = undefined;
+      level?.complete();
+      level = undefined;
+    };
+
+    const start = async (): Promise<void> => {
+      stream = await navigator.mediaDevices.getUserMedia({
+        audio:
+          deviceId === undefined ? true : { deviceId: { exact: deviceId } },
+      });
+      // Unsubscribed while the permission prompt was open.
+      if (subscriber.closed) return release();
+
+      context = new AudioContext();
+      // Starts suspended outside a user gesture, which would read as silence.
+      if (context.state === "suspended") await context.resume();
+      if (subscriber.closed) return release();
+
+      const analyser = context.createAnalyser();
+      analyser.fftSize = 1024;
+      context.createMediaStreamSource(stream).connect(analyser);
+      const samples = new Uint8Array(analyser.fftSize);
+      let displayed = 0;
+      let previousFrame = performance.now();
+      const current = new BehaviorSubject(0);
+      level = current;
+      subscriber.next({ type: "level", level$: current });
+
+      const read = (): void => {
+        analyser.getByteTimeDomainData(samples);
+        // RMS: perceived loudness rather than the peak.
+        let sum = 0;
+        for (const sample of samples) {
+          const centred = (sample - 128) / 128;
+          sum += centred * centred;
+        }
+        const now = performance.now();
+        displayed = smoothVolume(
+          displayed,
+          Math.sqrt(sum / samples.length),
+          now - previousFrame,
+        );
+        previousFrame = now;
+        // Frames that don't move the quantised level say nothing.
+        const next = segmentsForVolume(displayed);
+        if (next !== current.value) current.next(next);
+        frame = requestAnimationFrame(read);
+      };
+      read();
+    };
+
+    start().catch((e: unknown) => {
+      // Building the graph can fail after the device was granted.
+      release();
+      subscriber.next(stateForFailure(e));
+    });
+
+    return release;
+  });
+}
+
+/** What a failure to open the microphone means for the person using it. */
+function stateForFailure(e: unknown): MicrophoneState {
+  const name = e instanceof Error ? e.name : "";
+  if (name === "NotAllowedError" || name === "SecurityError")
+    return { type: "permission-denied" };
+  if (name === "NotFoundError" || name === "OverconstrainedError")
+    return { type: "no-device" };
+  logger.error("Could not read the microphone level", e);
+  return { type: "no-device" };
+}
+
+/** Below this counts as silence, so a quiet room's hiss doesn't light the first bars. */
+const NOISE_FLOOR = 0.02;
+
+/** Quantises a 0..1 volume onto {@link LEVEL_SCALE}. */
+export function segmentsForVolume(volume: number): number {
+  if (!Number.isFinite(volume) || volume <= NOISE_FLOOR) return 0;
+  // Square root, so ordinary speech reaches the middle of the scale.
+  const aboveFloor = (Math.min(volume, 1) - NOISE_FLOOR) / (1 - NOISE_FLOOR);
+  return Math.min(LEVEL_SCALE, Math.ceil(Math.sqrt(aboveFloor) * LEVEL_SCALE));
+}
+
+/** Rise time constant: short, so a syllable registers as it starts. */
+export const ATTACK_MS = 50;
+
+/** Fall time constant: longer, so the gaps between words don't flicker. */
+export const RELEASE_MS = 120;
+
+/** Eases towards a reading, by elapsed time so the frame rate doesn't matter. */
+export function smoothVolume(
+  displayed: number,
+  reading: number,
+  elapsedMs: number,
+): number {
+  if (elapsedMs <= 0) return displayed;
+  const timeConstant = reading > displayed ? ATTACK_MS : RELEASE_MS;
+  const towards = 1 - Math.exp(-elapsedMs / timeConstant);
+  return displayed + (reading - displayed) * towards;
+}

src/utils/test.ts

@@ -8,6 +8,7 @@ import { map, type Observable, of, type SchedulerLike } from "rxjs";
 import { type RunHelpers, TestScheduler } from "rxjs/testing";
 import {
   expect,
+  type Mock,
   type MockedObject,
   type MockInstance,
   onTestFinished,
@@ -590,3 +591,98 @@ export class MockConnection extends Connection {
   public async start(): Promise<void> {}
   public async stop(): Promise<void> {}
 }
+
+export interface StubbedCapture {
+  getUserMedia: Mock;
+  /** Grants the microphone, as the browser does once permission is given. */
+  grant: () => void;
+  track: { stop: Mock };
+  contexts: { close: Mock }[];
+  /** Runs the pending animation frames, in order. */
+  drawFrames: (count: number) => void;
+  /** Sets the microphone's loudness from the next frame, 0 to 1. */
+  speak: (amplitude: number) => void;
+}
+
+/**
+ * Stubs the capture and Web Audio APIs, with the grant and the animation
+ * frames driven by the test. Undo with {@link restoreAudioCapture}.
+ */
+export function stubAudioCapture(): StubbedCapture {
+  const track = { stop: vi.fn() };
+  const contexts: { close: Mock }[] = [];
+  let grant = (): void => {};
+  const granted = new Promise<MediaStream>((resolve) => {
+    grant = (): void =>
+      resolve({ getTracks: () => [track] } as unknown as MediaStream);
+  });
+
+  const frames: FrameRequestCallback[] = [];
+  let amplitude = 0;
+  vi.stubGlobal("requestAnimationFrame", (callback: FrameRequestCallback) => {
+    frames.push(callback);
+    return frames.length;
+  });
+  vi.stubGlobal("cancelAnimationFrame", vi.fn());
+  vi.stubGlobal(
+    "AudioContext",
+    class {
+      public readonly state = "running";
+      public readonly close = vi.fn();
+      public constructor() {
+        contexts.push(this);
+      }
+      public createAnalyser(): object {
+        return {
+          fftSize: 1024,
+          getByteTimeDomainData: (samples: Uint8Array): void => {
+            // Silence is the midpoint of the range; a zeroed buffer reads as full scale.
+            if (amplitude <= 0) {
+              samples.fill(128);
+              return;
+            }
+            const peak = Math.round(Math.min(1, amplitude) * 127);
+            for (let i = 0; i < samples.length; i++)
+              samples[i] = 128 + (i % 2 ? peak : -peak);
+          },
+        };
+      }
+      public createMediaStreamSource(): object {
+        return { connect: (): void => {} };
+      }
+    },
+  );
+  // Only this property: replacing navigator loses getters like userAgent.
+  Object.defineProperty(navigator, "mediaDevices", {
+    configurable: true,
+    value: { getUserMedia: vi.fn().mockReturnValue(granted) },
+  });
+
+  return {
+    getUserMedia: navigator.mediaDevices.getUserMedia as unknown as Mock,
+    grant: () => grant(),
+    track,
+    contexts,
+    drawFrames: (count): void => {
+      for (let i = 0; i < count; i++) frames.shift()?.(i);
+    },
+    speak: (next): void => {
+      amplitude = next;
+    },
+  };
+}
+
+const realMediaDevices = Object.getOwnPropertyDescriptor(
+  navigator,
+  "mediaDevices",
+);
+
+/** Undoes {@link stubAudioCapture}. */
+export function restoreAudioCapture(): void {
+  vi.unstubAllGlobals();
+  if (realMediaDevices === undefined) {
+    Reflect.deleteProperty(navigator, "mediaDevices");
+  } else {
+    Object.defineProperty(navigator, "mediaDevices", realMediaDevices);
+  }
+}