Add playwright test to check EW error screen dismiss on room switch

Add a devtool button to mock an error
2026-11-01 00:32:28 +00:00 · 2026-10-14 12:45:49 +02:00 · 2026-10-14 11:36:54 +02:00
38 changed files with 745 additions and 1465 deletions
@@ -19,7 +19,7 @@ services:
      - ./backend/playwright_homeserver-othersite.yaml:/data/cfg/homeserver.yaml:Z
  element-web:
    # Pin to a SHA so that upstream cannot break our tests. Renovate handles regular updates.
-    image: ghcr.io/element-hq/element-web:develop@sha256:79e47d8d5a93848403cb83042a405d8ed233a7727c499fa53b4b39a80f090be4
+    image: ghcr.io/element-hq/element-web:develop@sha256:e464b2aca73e248195b24b8c6f62cd331100302284d60cc735405807fb2730be
  element-web-1:
    # Pin to a SHA so that upstream cannot break our tests. Renovate handles regular updates.
-    image: ghcr.io/element-hq/element-web:develop@sha256:79e47d8d5a93848403cb83042a405d8ed233a7727c499fa53b4b39a80f090be4
+    image: ghcr.io/element-hq/element-web:develop@sha256:e464b2aca73e248195b24b8c6f62cd331100302284d60cc735405807fb2730be
@@ -88,6 +88,7 @@
    },
    "mute_all_audio": "Mute all audio (participants, reactions, join sounds)",
    "show_connection_stats": "Show connection statistics",
+    "throw_error_button": "Throw test error",
    "url_params": "URL parameters"
  },
  "disconnected_banner": "Connectivity to the server has been lost.",
@@ -106,7 +107,7 @@
    "insufficient_capacity_description": "The server has reached its maximum capacity and you cannot join the call at this time. Try again later, or contact your server admin if the problem persists.",
    "livekit_connection_error": "Failed to connect to Livekit server",
    "livekit_connection_error_description": "An error occurred while connecting to the Livekit server (<1>Reason:</1> <2>{{ reason }}</2>).",
-    "matrix_rtc_transport_missing": "The server is not configured to work with {{brand}} and no other call participant provides a usable transport. Please contact your server admin (Domain: {{domain}}, Error Code: {{ errorCode }}).",
+    "matrix_rtc_transport_missing": "The server is not configured to work with {{brand}}. Please contact your server admin (Domain: {{domain}}, Error Code: {{ errorCode }}).",
    "membership_manager": "Membership Manager Error",
    "membership_manager_description": "The Membership Manager had to shut down. This is caused by many consecutive failed network requests.",
    "no_matrix_2_authorization_service": "The authorization service for your media server (SFU) is out of date.",
@@ -107,7 +107,7 @@
    "livekit-client": "^2.18.1",
    "lodash-es": "^4.17.21",
    "loglevel": "^1.9.1",
-    "matrix-js-sdk": "github:matrix-org/matrix-js-sdk#3f05dc4d104a3dfc753c5e3549a18c74fab4b076",
+    "matrix-js-sdk": "github:matrix-org/matrix-js-sdk#develop",
    "matrix-widget-api": "^1.18.0",
    "node-stdlib-browser": "^1.3.1",
    "normalize.css": "^8.0.1",
@@ -133,7 +133,7 @@ async function disableLeaveDelegation(page: Page): Promise<void> {
 * Expect a certain number of video tiles to be present and visible.
 */
 async function expectVideoTilesCount(page: Page, count: number): Promise<void> {
-  await expect(page.getByTestId("videoTile")).toHaveCount(count);
+  await expect(page.getByTestId("videoTile")).toHaveCount(2);

  // No one should be waiting for media
  await expect(page.getByText("Waiting for media...")).not.toBeVisible({
@@ -31,11 +31,7 @@ interface Transport {
 */
 const shapes = {
  url: { type: "livekit", url: sfuUrl },
-  "url+legacy": {
-    type: "livekit",
-    url: sfuUrl,
-    livekit_service_url: serviceUrl,
-  },
+  both: { type: "livekit", url: sfuUrl, livekit_service_url: serviceUrl },
  legacy: null,
 } satisfies Record<string, Transport | null>;
 type Shape = keyof typeof shapes;
@@ -60,15 +56,15 @@ const cases: {
  {
    // Publishers keep the legacy participant identity that clients predating
    // MSC4195 expect, which only the JWT service assigns.
-    hostShape: "url+legacy",
-    guestShape: "url+legacy",
+    hostShape: "both",
+    guestShape: "both",
    hostFlows: ["service-legacy"],
    guestFlows: ["service-legacy"],
  },
  {
    // The MatrixRTC mode has no bearing on the choice.
-    hostShape: "url+legacy",
-    guestShape: "url+legacy",
+    hostShape: "both",
+    guestShape: "both",
    mode: "2_0",
    hostFlows: ["service-legacy"],
    guestFlows: ["service-legacy"],
@@ -79,12 +75,6 @@ const cases: {
    hostFlows: ["cs-api", "service-default"],
    guestFlows: ["service-legacy", "cs-api"],
  },
-  {
-    hostShape: "url",
-    guestShape: "url+legacy",
-    hostFlows: ["cs-api", "service-default"],
-    guestFlows: ["service-legacy", "cs-api"],
-  },
 ];

 for (const { hostShape, guestShape, mode, hostFlows, guestFlows } of cases) {
@@ -136,6 +126,47 @@ for (const { hostShape, guestShape, mode, hostFlows, guestFlows } of cases) {
  });
 }

+test("Subscriber falls back to the JWT service when the homeserver lacks MSC4195", async ({
+  browser,
+  page,
+  browserName,
+}) => {
+  skipOnFirefox(browserName);
+
+  // The host starts the call with both transport shapes.
+  await advertiseTransport(page, shapes.both);
+  await page.goto("/");
+  await SpaHelpers.createCall(page, "Androl", "HelloCall", true);
+  const inviteLink = await SpaHelpers.getCallInviteLink(page);
+
+  // The guest joins but their C-S requests fail.
+  const guestContext = await browser.newContext({ reducedMotion: "reduce" });
+  const guestPage = await guestContext.newPage();
+  await rejectCsApiTokens(guestPage);
+  const guestRequests = recordAuthRequests(guestPage);
+  await SpaHelpers.joinCallFromInviteLink(guestPage, inviteLink, "Pevara");
+
+  // Wait for the call to connect and render.
+  await SpaHelpers.expectVideoTilesCount(page, 2);
+  await SpaHelpers.expectVideoTilesCount(guestPage, 2);
+
+  // The guest ran through all flows.
+  expect(flowsOf(guestRequests)).toEqual(
+    new Set<Flow>(["cs-api", "service-legacy", "service-default"]),
+  );
+
+  // The C-S token requests failed.
+  for (const request of guestRequests) {
+    expect(request.status).toBe(request.flow === "cs-api" ? 404 : 200);
+  }
+
+  // The C-S token requests preceeded the fallback request.
+  const flows = guestRequests.map((r) => r.flow);
+  expect(flows.indexOf("service-default")).toBeGreaterThan(
+    flows.indexOf("cs-api"),
+  );
+});
+
 test("Publisher shows an error when the homeserver lacks MSC4195", async ({
  page,
  browserName,
@@ -160,38 +191,6 @@ test("Publisher shows an error when the homeserver lacks MSC4195", async ({
  ).toBeVisible();
 });

-test("Group call with all possible transport shapes at once", async ({
-  browser,
-  page,
-  browserName,
-}) => {
-  test.slow();
-  skipOnFirefox(browserName);
-
-  // The host starts the call with a url transport.
-  await advertiseTransport(page, shapes.url);
-  await page.goto("/");
-  await SpaHelpers.createCall(page, "Alice", "HelloCall", true);
-  const inviteLink = await SpaHelpers.getCallInviteLink(page);
-
-  // The guest with a legacy transport joins.
-  const bobContext = await browser.newContext({ reducedMotion: "reduce" });
-  const bobPage = await bobContext.newPage();
-  await advertiseTransport(bobPage, shapes.legacy);
-  await SpaHelpers.joinCallFromInviteLink(bobPage, inviteLink, "Bob");
-
-  // The guest with a url+legacy transport joins.
-  const carolContext = await browser.newContext({ reducedMotion: "reduce" });
-  const carolPage = await carolContext.newPage();
-  await advertiseTransport(carolPage, shapes["url+legacy"]);
-  await SpaHelpers.joinCallFromInviteLink(carolPage, inviteLink, "Carol");
-
-  // Wait for the call to connect and render.
-  await SpaHelpers.expectVideoTilesCount(page, 3);
-  await SpaHelpers.expectVideoTilesCount(bobPage, 3);
-  await SpaHelpers.expectVideoTilesCount(carolPage, 3);
-});
-
 /**
 * Delegation follows the flow that authenticated the publisher: the homeserver
 * for a `url`-only transport, the JWT service wherever there is one.
@@ -199,7 +198,7 @@ test("Group call with all possible transport shapes at once", async ({
 const delegationCases: { shape: Shape; via: Delegation["via"] }[] = [
  { shape: "url", via: "homeserver" },
  { shape: "legacy", via: "service" },
-  { shape: "url+legacy", via: "service" },
+  { shape: "both", via: "service" },
 ];

 for (const { shape, via } of delegationCases) {
@@ -0,0 +1,64 @@
+/*
+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 } from "@playwright/test";
+
+import { widgetTest } from "../fixtures/widget-user.ts";
+import { TestHelpers } from "./test-helpers.ts";
+
+widgetTest.skip(
+  ({ browserName }) => browserName === "firefox",
+  "Widget specs only run on Chromium, see simple-create.spec.ts",
+);
+
+widgetTest(
+  "Switching rooms away from a crashed call dismisses it for good",
+  async ({ asWidget }) => {
+    test.slow();
+    const { brooks } = asWidget;
+    const page = brooks.page;
+    const call = page.locator('iframe[title="Element Call"]');
+    const callFrame = call.contentFrame();
+
+    // Somewhere to switch to once the call has crashed
+    await TestHelpers.createRoom("Other Room", page);
+    await TestHelpers.switchToRoomNamed(page, "Welcome Room");
+
+    await TestHelpers.startCallInCurrentRoom(page);
+    // A dev server compiles the widget on first load
+    await expect(callFrame.getByTestId("lobby_joinCall")).toBeVisible({
+      timeout: 30000,
+    });
+    await TestHelpers.joinCallFromLobby(page);
+    await expect(
+      callFrame.getByRole("button", { name: "End call" }),
+    ).toBeVisible();
+
+    // Crash the call from its developer settings
+    await callFrame.getByRole("button", { name: "Settings" }).click();
+    await callFrame.getByRole("tab", { name: "Preferences" }).click();
+    await callFrame.getByText("Developer mode", { exact: true }).check();
+    await callFrame.getByRole("tab", { name: "Developer" }).click();
+    await callFrame.getByRole("button", { name: "Throw test error" }).click();
+    await expect(callFrame.getByText("Something went wrong")).toBeVisible();
+
+    // Showing the call collapses the room list
+    await TestHelpers.expandRoomList(page);
+    await TestHelpers.switchToRoomNamed(page, "Other Room");
+    await expect(
+      page.getByRole("banner").getByRole("heading", { name: "Other Room" }),
+    ).toBeVisible();
+
+    // The crashed call is gone and stays gone: no restart, no reconnect
+    await expect(call).toHaveCount(0);
+    await page.waitForTimeout(5000);
+    await expect(call).toHaveCount(0);
+    await expect(
+      page.getByRole("banner").getByRole("heading", { name: "Other Room" }),
+    ).toBeVisible();
+  },
+);
@@ -159,7 +159,7 @@ export class TestHelpers {
  public static async dismissStartupToasts(page: Page): Promise<void> {
    const expectedToasts = [
      { title: "Failed to load service worker", button: "OK" },
-      { title: "Back up your chats", button: "Not now" },
+      { title: "Back up your chats", button: "Dismiss" },
      { title: "Turn on key storage", button: "Dismiss" },
      { title: "Element does not support this browser", button: "Dismiss" },
    ];
@@ -178,11 +178,7 @@ export class TestHelpers {
        );

        if (toastConfig) {
-          // Bounded so that a renamed button leaves the toast in place and the
-          // next step reports it, instead of hanging until the test timeout.
-          await toast
-            .getByRole("button", { name: toastConfig.button })
-            .click({ timeout: 5000 });
+          await toast.getByRole("button", { name: toastConfig.button }).click();
        } else {
          // Unknown toast. We don't want to act on unknown toasts
          break;
@@ -11,12 +11,13 @@ import { widgetTest } from "../fixtures/widget-user.ts";
 import { HOST1, TestHelpers } from "./test-helpers.ts";

 const sfuUrl = "wss://matrix-rtc.m.localhost/livekit/sfu";
+const serviceUrl = "https://matrix-rtc.m.localhost/livekit/jwt";

 /** Which endpoint a page asks for its SFU tokens. */
 type Flow = "cs-api" | "service-legacy" | "service-default";

 widgetTest(
-  "Call between a url transport and a legacy one",
+  "Call between a url + livekit_service_url transport and a legacy one",
  async ({ addUser, browserName }) => {
    test.skip(
      browserName === "firefox",
@@ -29,10 +30,12 @@ widgetTest(
      addUser("Pevara", HOST1),
    ]);

-    // Host advertises a url transport, guest still advertises a legacy one
+    // The host's homeserver has started advertising a `url` next to its JWT
+    // service; the guest's still advertises the JWT service alone.
    await advertiseTransport(host.page, {
      type: "livekit",
      url: sfuUrl,
+      livekit_service_url: serviceUrl,
    });
    // Element Web answers the widget from a cache it filled at login, so make
    // it fetch the transports again now that they are rerouted
@@ -63,9 +66,13 @@ widgetTest(
      await TestHelpers.expectVisibleVideoCount(frame, 2);
    }

-    // Element Web used for Playwright does support MSC4195 for widgets.
-    expect(hostFlows).toEqual(new Set(["cs-api", "service-default"]));
-    expect(guestFlows).toEqual(new Set(["service-legacy", "cs-api"]));
+    // Element Web does not expose the MSC4195 endpoints to widgets yet, so
+    // neither side reached the CS API. The host published through the JWT
+    // service's legacy endpoint and subscribed to the guest through its
+    // default one; the guest published the same way and fell back to the
+    // default endpoint for the host's transport.
+    expect(hostFlows).toEqual(new Set(["service-legacy", "service-default"]));
+    expect(guestFlows).toEqual(new Set(["service-legacy", "service-default"]));
  },
 );

@@ -101,8 +101,6 @@ LiveKit participants.
  │  create ───▶│                                       │                         │
  │             │ GET rtc/transports (session) ────────▶│                         │
  │             │◀── first transport of the backend's type                        │
-  │             │   (none, LiveKit only: a member's SFU │                         │
-  │             │    that lets us publish, get_token) ─▶│                         │
  │             │ prepareLocalTransport (backend):      │                         │
  │             │   publisher token: CS API get_token,  │                         │
  │             │   or OpenID token then /sfu/get ─────▶│                         │
@@ -558,10 +556,7 @@ export interface MediaBackend {
 ```

 What stays on the client's side: discovery of the local transport from the
-homeserver's list (a homeserver endpoint, so not a backend's) with, for the
-LiveKit backend only, a last resort of another member's SFU that lets us
-publish (`findRemotePublishLivekitTransport`, wired in by `RTCParticipation` rather
-than by the backend interface, since it is an MSC4195 matter), the membership
+homeserver's list (a homeserver endpoint, so not a backend's), the membership
 state machine in `LocalMembership.ts` and its combination with
 `local.connectionState$` into `state$`, the choice of delayed leave timings,
 mapping a data packet's sender to a member, and the transport registry, which keys on the raw
@@ -1,9 +0,0 @@
-lockfileVersion: '9.0'
-
-settings:
-  autoInstallPeers: false
-  excludeLinksFromLockfile: false
-
-importers:
-
-  .: {}
@@ -8,11 +8,9 @@ Please see LICENSE in the repository root for full details.
 import { type MatrixClient, type Room, SyncState } from "matrix-js-sdk";
 import { logger } from "matrix-js-sdk/lib/logger";
 import {
-  type CallMembership,
  MatrixRTCSessionEvent,
  MembershipManagerEvent,
  type Transport,
-  type UnstableLivekitTransport,
 } from "matrix-js-sdk/lib/matrixrtc";
 import { BehaviorSubject, EMPTY, Subject } from "rxjs";
 import { describe, expect, it, type Mock, vi } from "vitest";
@@ -40,32 +38,13 @@ import { constant } from "./reactive/Behavior";
 import { ObservableScope } from "./reactive/ObservableScope";
 import { createRTCParticipation } from "./RTCParticipation";
 import { transportId } from "./matrixrtc/Transports";
-import {
-  flushPromises,
-  mockEmitter,
-  mockRtcMembership,
-  MockRTCSession,
-} from "./utils/test";
+import { flushPromises, mockEmitter, MockRTCSession } from "./utils/test";

-const transport: UnstableLivekitTransport = {
+const transport: Transport = {
  type: "livekit",
  livekit_service_url: "https://lk.example.org",
 };
-
-const transportWithAlias: Transport = {
-  livekit_alias: "!room:example.org",
-  ...transport,
-};
-
 const userId = "@alice:example.org";
-/** A token with the publish grant, as a homeserver issues it for its own SFU. */
-const publisherJWT = [
-  {},
-  { sub: "identity", video: { room: "room", canPublish: true } },
-  {},
-]
-  .map((d) => global.btoa(JSON.stringify(d)))
-  .join(".");
 const deviceId = "AAAA";
 const legacyMemberId = `${userId}:${deviceId}`;

@@ -112,13 +91,6 @@ interface FakeBackend {
 function setup(
  options: Partial<RTCParticipationOptions> = {},
  slotOptions: { matrixRTCMode?: MatrixRTCMode } = {},
-  {
-    homeserverTransports = [transport],
-    memberships = [],
-  }: {
-    homeserverTransports?: Transport[];
-    memberships?: CallMembership[];
-  } = {},
 ): {
  scope: ObservableScope;
  participation: ReturnType<typeof createRTCParticipation>["participation"];
@@ -131,7 +103,7 @@ function setup(
 } {
  const scope = new ObservableScope();
  const room = { roomId: "!room:example.org" } as Room;
-  const session = new MockRTCSession(room, memberships);
+  const session = new MockRTCSession(room);
  const mockedSession = session.asMockedSession();
  const join = vi.spyOn(session, "join");
  const client = {
@@ -140,8 +112,7 @@ function setup(
    getDeviceId: () => deviceId,
    getDomain: () => "example.org",
    getSyncState: () => SyncState.Syncing,
-    _unstable_getRTCTransports: vi.fn().mockResolvedValue(homeserverTransports),
-    _unstable_getLivekitToken: vi.fn().mockResolvedValue({ jwt: publisherJWT }),
+    _unstable_getRTCTransports: vi.fn().mockResolvedValue([transport]),
  } as unknown as MatrixClient;
  const members$ = new BehaviorSubject<RTCMember[]>([]);

@@ -230,7 +201,7 @@ describe("createRTCParticipation", () => {
    await flushPromises();
    expect(join).toHaveBeenCalledWith(
      { userId, deviceId, memberId: legacyMemberId },
-      [transportWithAlias],
+      [transport],
      expect.objectContaining({
        manageMediaKeys: true,
        unstableSendStickyEvents: false,
@@ -249,32 +220,6 @@ describe("createRTCParticipation", () => {
    });
  });

-  it("publishes on another member's SFU where the homeserver advertises none", async () => {
-    const bobOnSfu = mockRtcMembership("@bob:example.org", "BOB", {
-      fociPreferred: [{ type: "livekit", url: "wss://sfu.example.org" }],
-    });
-    const { join, fake } = setup(
-      {},
-      {},
-      { homeserverTransports: [], memberships: [bobOnSfu] },
-    );
-    fake.prepared.resolve({ canDelegateDelayedLeave: false });
-    await flushPromises();
-    await flushPromises();
-
-    expect(join).toHaveBeenCalledWith(
-      expect.anything(),
-      [
-        {
-          type: "livekit",
-          url: "wss://sfu.example.org",
-          server_name: "example.org",
-        },
-      ],
-      expect.anything(),
-    );
-  });
-
  it("publishes only while joined", async () => {
    const { participation, session, fake, scope } = setup();
    const ended = vi.fn();
@@ -326,7 +271,7 @@ describe("createRTCParticipation", () => {
    await flushPromises();
    expect(join).toHaveBeenCalledWith(
      expect.anything(),
-      [transportWithAlias],
+      [transport],
      expect.objectContaining({ delayedLeaveEventDelayMs: 7_200_000 }),
    );
    expect(fake.delegateDelayedLeave).not.toHaveBeenCalled();
@@ -11,7 +11,6 @@ import {
  type MatrixRTCSession as JsSdkRTCSession,
  MatrixRTCSessionEvent,
  MembershipManagerEvent,
-  type Transport,
 } from "matrix-js-sdk/lib/matrixrtc";
 import { type IMembershipManager } from "matrix-js-sdk/lib/matrixrtc/IMembershipManager";
 import { type CallMembershipIdentityParts } from "matrix-js-sdk/lib/matrixrtc/EncryptionManager";
@@ -51,7 +50,6 @@ import {
  type MediaKey,
 } from "./media-backend/api";
 import { createLivekitBackend } from "./media-backend/livekit/LivekitBackend";
-import { findRemotePublishLivekitTransport } from "./media-backend/livekit/RemotePublishTransport";
 import { createHomeserverConnected$ } from "./matrixrtc/HomeserverConnected";
 import { joinJsSdkSession } from "./matrixrtc/joinJsSdkSession";
 import {
@@ -132,34 +130,13 @@ export function createRTCParticipation(
    logger,
  });

-  // If the backend is LiveKit, we check it for transports as well, as a
-  // fallback: another member's SFU may let us publish (MSC4195). LiveKit only,
-  // so it stays out of the backend interface
-  const transportFromBackends = async (): Promise<Transport | null> =>
-    backend.transportType === "livekit"
-      ? findRemotePublishLivekitTransport({
-          client,
-          // A snapshot: if nobody with a usable SFU is here yet, the user has
-          // to come back later rather than wait in a half-working lobby
-          memberships: jsSdkSession.memberships,
-          ownMembershipIdentity,
-          roomId: room.roomId,
-          slotId: jsSdkSession.slotId,
-          logger,
-        })
-      : null;
-
  const preparedTransport$ = from(
-    discoverLocalTransport(
-      client,
-      backend.transportType,
-      options,
-      transportFromBackends,
-      logger,
-    ).then(async (transport): Promise<PreparedTransport> => ({
-      transport,
-      ...(await backend.prepareLocalTransport(transport)),
-    })),
+    discoverLocalTransport(client, backend.transportType, options, logger).then(
+      async (transport): Promise<PreparedTransport> => ({
+        transport,
+        ...(await backend.prepareLocalTransport(transport)),
+      }),
+    ),
  );

  const localMembership = createLocalMembership$({
@@ -174,20 +151,14 @@ export function createRTCParticipation(
      timings.syncDisconnectGracePeriodMs,
    ),
    joinMatrixRTC: (transport, delayedLeave) =>
-      joinJsSdkSession(
-        room.roomId,
-        jsSdkSession,
-        ownMembershipIdentity,
-        transport,
-        {
-          encryptMedia: encryptionSystem.kind !== E2eeType.NONE,
-          matrixRTCMode,
-          sendNotificationType: options.sendNotificationType,
-          applicationData: options.applicationData,
-          timings,
-          delayedLeave,
-        },
-      ),
+      joinJsSdkSession(jsSdkSession, ownMembershipIdentity, transport, {
+        encryptMedia: encryptionSystem.kind !== E2eeType.NONE,
+        matrixRTCMode,
+        sendNotificationType: options.sendNotificationType,
+        applicationData: options.applicationData,
+        timings,
+        delayedLeave,
+      }),
    membershipManagerError$: fromEvent(
      jsSdkSession,
      MatrixRTCSessionEvent.MembershipManagerError,
@@ -20,11 +20,6 @@ const hostTransport: Transport = {
  type: "livekit",
  livekit_service_url: "https://host.example.org",
 };
-const bobsTransport: Transport = {
-  type: "livekit",
-  url: "wss://sfu.bob.com",
-  server_name: "bob.com",
-};

 function client(
  advertised: Transport[],
@@ -35,12 +30,6 @@ function client(
  };
 }

-function fromBackends(
-  transport: Transport | null = null,
-): ReturnType<typeof vi.fn<() => Promise<Transport | null>>> {
-  return vi.fn(async () => Promise.resolve(transport));
-}
-
 describe("discoverLocalTransport", () => {
  it("takes the transport the host names without asking the homeserver", async () => {
    const c = client([homeserverTransport]);
@@ -50,7 +39,6 @@ describe("discoverLocalTransport", () => {
        c,
        "livekit",
        { transport: hostTransport },
-        fromBackends(),
        logger,
      ),
    ).resolves.toBe(hostTransport);
@@ -63,7 +51,6 @@ describe("discoverLocalTransport", () => {
        client([homeserverTransport]),
        "livekit",
        { fallbackTransport: hostTransport },
-        fromBackends(),
        logger,
      ),
    ).resolves.toEqual(homeserverTransport);
@@ -75,35 +62,13 @@ describe("discoverLocalTransport", () => {
        client([{ type: "not_livekit" }]),
        "livekit",
        { fallbackTransport: hostTransport },
-        fromBackends(),
        logger,
      ),
    ).resolves.toEqual(hostTransport);
  });

-  it("prefers a local transport over the backends' without asking them", async () => {
-    const backends = fromBackends(bobsTransport);
-
-    await expect(
-      discoverLocalTransport(
-        client([homeserverTransport]),
-        "livekit",
-        {},
-        backends,
-        logger,
-      ),
-    ).resolves.toEqual(homeserverTransport);
-    expect(backends).not.toHaveBeenCalled();
-  });
-
  it("fails naming the homeserver where there is no transport at all", async () => {
-    const promise = discoverLocalTransport(
-      client([]),
-      "livekit",
-      {},
-      fromBackends(),
-      logger,
-    );
+    const promise = discoverLocalTransport(client([]), "livekit", {}, logger);

    await expect(promise).rejects.toBeInstanceOf(
      MatrixRTCTransportMissingError,
@@ -15,10 +15,7 @@ import { TransportAutoDiscovery } from "./TransportAutoDiscovery";

 /**
 * The transport the local member advertises: the one the host names, else the
- * homeserver's first of the type the backend serves, else the host's fallback,
- * else the first the backends can provide, which are asked only then.
- *
- * @throws {MatrixRTCTransportMissingError} where none of these exists.
+ * homeserver's first of the type the backend serves, else the host's fallback.
 */
 export async function discoverLocalTransport(
  client: Pick<MatrixClient, "getDomain" | "_unstable_getRTCTransports">,
@@ -27,7 +24,6 @@ export async function discoverLocalTransport(
    transport: override,
    fallbackTransport,
  }: Pick<RTCParticipationOptions, "transport" | "fallbackTransport">,
-  transportFromBackends: () => Promise<Transport | null>,
  logger: Logger,
 ): Promise<Transport> {
  const transport =
@@ -37,9 +33,7 @@ export async function discoverLocalTransport(
      transportType,
      fallbackTransport,
      logger,
-    }).discoverPreferredTransport()) ??
-    (await transportFromBackends()) ??
-    null;
+    }).discoverPreferredTransport());
  if (transport === null)
    throw new MatrixRTCTransportMissingError(client.getDomain() ?? "");
  return transport;
@@ -6,7 +6,6 @@ Please see LICENSE in the repository root for full details.
 */

 import {
-  type UnstableLivekitTransport,
  type MatrixRTCSession,
  type Transport,
 } from "matrix-js-sdk/lib/matrixrtc";
@@ -16,16 +15,11 @@ import { defaultSessionTimings, MatrixRTCMode } from "../config";
 import { ownMemberMock } from "../utils/test";
 import { joinJsSdkSession } from "./joinJsSdkSession";

-const transport: UnstableLivekitTransport = {
+const transport: Transport = {
  type: "livekit",
  livekit_service_url: "https://lk.example.org",
 };

-const transportWithAlias: Transport = {
-  livekit_alias: "!room:example.org",
-  ...transport,
-};
-
 /** A session that only records the join; nothing else of it is touched. */
 function session(): MatrixRTCSession & {
  join: Mock<MatrixRTCSession["join"]>;
@@ -45,7 +39,7 @@ describe("joinJsSdkSession", () => {
      keyRotationParticipantLimit: 20,
    };

-    joinJsSdkSession("!room:example.org", s, ownMemberMock, transport, {
+    joinJsSdkSession(s, ownMemberMock, transport, {
      encryptMedia: true,
      matrixRTCMode: MatrixRTCMode.Compatibility,
      sendNotificationType: "ring",
@@ -57,7 +51,7 @@ describe("joinJsSdkSession", () => {
      },
    });

-    expect(s.join).toHaveBeenCalledWith(ownMemberMock, [transportWithAlias], {
+    expect(s.join).toHaveBeenCalledWith(ownMemberMock, [transport], {
      notificationType: "ring",
      callIntent: undefined,
      applicationData: {},
@@ -78,7 +72,7 @@ describe("joinJsSdkSession", () => {
  it("gives up on the network once the delayed leave has probably been sent", () => {
    const s = session();

-    joinJsSdkSession("!room:example.org", s, ownMemberMock, transport, {
+    joinJsSdkSession(s, ownMemberMock, transport, {
      encryptMedia: false,
      matrixRTCMode: MatrixRTCMode.Compatibility,
      timings: { ...defaultSessionTimings, networkErrorRetryMs: 4_000 },
@@ -87,7 +81,7 @@ describe("joinJsSdkSession", () => {

    expect(s.join).toHaveBeenCalledWith(
      ownMemberMock,
-      [transportWithAlias],
+      [transport],
      expect.objectContaining({
        manageMediaKeys: false,
        maximumNetworkErrorRetryCount: 4,
@@ -98,30 +92,7 @@ describe("joinJsSdkSession", () => {
  it("lifts the call intent out of the application data and sends sticky events in Matrix 2.0 mode", () => {
    const s = session();

-    joinJsSdkSession("!room:example.org", s, ownMemberMock, transport, {
-      encryptMedia: true,
-      matrixRTCMode: MatrixRTCMode.Matrix_2_0,
-      applicationData: { "m.call.intent": "audio", custom: 1 },
-      timings: defaultSessionTimings,
-      delayedLeave: defaultSessionTimings.delayedLeave,
-    });
-
-    expect(s.join).toHaveBeenCalledWith(
-      ownMemberMock,
-      [transportWithAlias],
-      expect.objectContaining({
-        callIntent: "audio",
-        applicationData: { custom: 1 },
-        unstableSendStickyEvents: true,
-      }),
-    );
-  });
-
-  it("does not add livekit_alias to newer transport format", () => {
-    const s = session();
-    const transport = { type: "livekit", url: "wss://lk.example.org" };
-
-    joinJsSdkSession("!room:example.org", s, ownMemberMock, transport, {
+    joinJsSdkSession(s, ownMemberMock, transport, {
      encryptMedia: true,
      matrixRTCMode: MatrixRTCMode.Matrix_2_0,
      applicationData: { "m.call.intent": "audio", custom: 1 },
@@ -35,7 +35,6 @@ interface Options {
 * @throws If the join could not be started.
 */
 export function joinJsSdkSession(
-  roomId: string,
  session: JsSdkRTCSession,
  ownMembershipIdentity: CallMembershipIdentityParts,
  transport: Transport,
@@ -59,37 +58,20 @@ export function joinJsSdkSession(
    timings.syncDisconnectGracePeriodMs,
    delayedLeave.delay_ms,
  );
-
-  session.join(
-    ownMembershipIdentity,
-    // TODO: `livekit_alias` should be unused these days, but some Ruma-based
-    // clients still expect it to be present. Remove from `publishedTransports`
-    // as soon as https://github.com/ruma/ruma/pull/2642 and
-    // https://github.com/matrix-org/matrix-rust-sdk/pull/7335 are widely
-    // deployed.
-    [
-      {
-        ...("livekit_service_url" in transport
-          ? { livekit_alias: roomId }
-          : {}),
-        ...transport,
-      },
-    ],
-    {
-      notificationType: sendNotificationType,
-      callIntent,
-      applicationData: rest,
-      manageMediaKeys: encryptMedia,
-      delayedLeaveEventRestartMs: delayedLeave.restart_ms,
-      delayedLeaveEventDelayMs: delayedLeave.delay_ms,
-      delayedLeaveEventRestartLocalTimeoutMs: delayedLeave.restart_timeout_ms,
-      networkErrorRetryMs: timings.networkErrorRetryMs,
-      makeKeyDelay: timings.waitForKeyRotationMs,
-      membershipEventExpiryMs: timings.membershipEventExpiryMs,
-      keyRotationParticipantLimit: timings.keyRotationParticipantLimit,
-      unstableSendStickyEvents: matrixRTCMode === MatrixRTCMode.Matrix_2_0,
-      maximumNetworkErrorRetryCount:
-        Math.ceil(maxWaitMs / timings.networkErrorRetryMs) + 1,
-    },
-  );
+  session.join(ownMembershipIdentity, [transport], {
+    notificationType: sendNotificationType,
+    callIntent,
+    applicationData: rest,
+    manageMediaKeys: encryptMedia,
+    delayedLeaveEventRestartMs: delayedLeave.restart_ms,
+    delayedLeaveEventDelayMs: delayedLeave.delay_ms,
+    delayedLeaveEventRestartLocalTimeoutMs: delayedLeave.restart_timeout_ms,
+    networkErrorRetryMs: timings.networkErrorRetryMs,
+    makeKeyDelay: timings.waitForKeyRotationMs,
+    membershipEventExpiryMs: timings.membershipEventExpiryMs,
+    keyRotationParticipantLimit: timings.keyRotationParticipantLimit,
+    unstableSendStickyEvents: matrixRTCMode === MatrixRTCMode.Matrix_2_0,
+    maximumNetworkErrorRetryCount:
+      Math.ceil(maxWaitMs / timings.networkErrorRetryMs) + 1,
+  });
 }
@@ -24,7 +24,7 @@ import {
 import { type ConnectionFactory } from "./ConnectionFactory.ts";
 import { type Connection } from "./Connection.ts";
 import { ownMemberMock, withTestScheduler } from "../../utils/test";
-import { constant, type Behavior } from "../../reactive/Behavior";
+import { type Behavior } from "../../reactive/Behavior";
 import { type TransportLocator } from "./auth";

 const TRANSPORT_1: TransportLocator = {
@@ -207,7 +207,7 @@ describe("connections$ stream", () => {
    });
  });

-  test("Keeps one connection per homeserver for url transports", () => {
+  test("Keeps one connection per homeserver for transports with a url", () => {
    withTestScheduler(({ behavior, expectObservable }) => {
      const urlTransport: TransportLocator = {
        transport: { type: "livekit", url: "wss://sfu.example.org" },
@@ -243,94 +243,6 @@ describe("connections$ stream", () => {
    });
  });

-  test("Shares connection between local livekit_service_url transport and remote url + livekit_service_url transport", () => {
-    withTestScheduler(({ behavior, expectObservable, scope }) => {
-      const serviceUrlTransport: TransportLocator = {
-        transport: {
-          type: "livekit",
-          livekit_service_url: "https://jwt.example.org",
-        },
-        serverName: "example.org",
-      };
-      const urlAndServiceUrlTransport: TransportLocator = {
-        transport: {
-          type: "livekit",
-          livekit_service_url: "https://jwt.example.org",
-          url: "wss://sfu.elsewhere.org",
-        },
-        // Should pass even if local server != remote server
-        serverName: "elsewhere.org",
-      };
-      const connectionMap$ = createConnectionMap$({
-        scope,
-        connectionFactory: fakeConnectionFactory,
-        localTransport: serviceUrlTransport,
-        remoteTransports$: constant(new Epoch([urlAndServiceUrlTransport])),
-        logger,
-        ownMembershipIdentity: ownMemberMock,
-      });
-
-      expectObservable(
-        connectionMap$.pipe(mapEpoch((d) => d.getConnections())),
-      ).toBe("a", {
-        a: expect.toSatisfy(({ value: cs }: Epoch<Connection[]>) => {
-          // One connection total, since local and remote connections are shared
-          expect(cs.length).toBe(1);
-          expect(findConnection(serviceUrlTransport, cs)).toBeDefined();
-          expect(findConnection(serviceUrlTransport, cs)).toBe(
-            findConnection(urlAndServiceUrlTransport, cs),
-          );
-          return true;
-        }),
-      });
-    });
-  });
-
-  test("Shares connection between remote livekit_service_url transport and remote url + livekit_service_url transport", () => {
-    withTestScheduler(({ behavior, expectObservable, scope }) => {
-      const serviceUrlTransport: TransportLocator = {
-        transport: {
-          type: "livekit",
-          livekit_service_url: "https://jwt.example.org",
-        },
-        serverName: "example.org",
-      };
-      const urlAndServiceUrlTransport: TransportLocator = {
-        transport: {
-          type: "livekit",
-          livekit_service_url: "https://jwt.example.org",
-          url: "wss://sfu.elsewhere.org",
-        },
-        // Should pass even if local server != remote server
-        serverName: "elsewhere.org",
-      };
-      const connectionMap$ = createConnectionMap$({
-        scope,
-        connectionFactory: fakeConnectionFactory,
-        localTransport: TRANSPORT_2,
-        remoteTransports$: constant(
-          new Epoch([serviceUrlTransport, urlAndServiceUrlTransport]),
-        ),
-        logger,
-        ownMembershipIdentity: ownMemberMock,
-      });
-
-      expectObservable(
-        connectionMap$.pipe(mapEpoch((d) => d.getConnections())),
-      ).toBe("a", {
-        a: expect.toSatisfy(({ value: cs }: Epoch<Connection[]>) => {
-          // Two connections total: a local connection and a shared remote connection
-          expect(cs.length).toBe(2);
-          expect(findConnection(serviceUrlTransport, cs)).toBeDefined();
-          expect(findConnection(serviceUrlTransport, cs)).toBe(
-            findConnection(urlAndServiceUrlTransport, cs),
-          );
-          return true;
-        }),
-      });
-    });
-  });
-
  test("Should start connection only once", () => {
    withTestScheduler(({ behavior, expectObservable }) => {
      const connectionMap$ = createConnectionMap$({
@@ -432,7 +344,7 @@ describe("ConnectionMap", () => {
    data.add({ ...connection } as Connection, [p("b")]);
    expect(warn).toHaveBeenCalledWith(
      expect.stringContaining(
-        'second connection to ["openID","https://lk.example.org"]: existing [a], adding [b]',
+        'second connection to [null,"https://lk.example.org",null]: existing [a], adding [b]',
      ),
    );
    expect(data.getParticipantsForTransport(TRANSPORT_1)).toHaveLength(2);
@@ -18,11 +18,7 @@ import {
  type ObservableScope,
 } from "../../reactive/ObservableScope";
 import { generateItemsWithEpoch } from "../../reactive/observable";
-import {
-  chooseAuthFlow,
-  type ConnectionRole,
-  type TransportLocator,
-} from "./auth";
+import { type ConnectionRole, type TransportLocator } from "./auth";
 import { type Connection } from "./Connection";
 import { type ConnectionFactory } from "./ConnectionFactory";

@@ -30,25 +26,22 @@ import { type ConnectionFactory } from "./ConnectionFactory";
 export type TransportKey = string & { __transportKey: true };

 /**
- * Converts a {@link TransportLocator} to a key suitable for identifying it in a
- * map of connections.
+ * The key a locator is identified by in a map or set. Locators with the same
+ * key share a connection: the server name only takes part in authentication
+ * for a transport with a `url`, where our homeserver asks that server for the
+ * token. A JWT service is reached directly, so members of several homeservers
+ * advertising the same one share a connection rather than each get their own.
 */
 export function keyFor({
  transport,
  serverName,
 }: TransportLocator): TransportKey {
-  // Base the key on the auth flow we would use, so that we never create two
-  // connections that share the same auth details. (That would be bad, as we
-  // might then try to connect to the same SFU twice with the same participant
-  // ID, resulting in only one working connection.)
-  // TODO: This strategy will not work once `chooseAuthFlow` begins allowing for
-  // falling back from the CS API flow to the OpenID flow.
-  const flow = chooseAuthFlow(transport);
+  const hasUrl = "url" in transport;
  // Serialize the fields in a consistent order
  return JSON.stringify([
-    flow.kind,
-    // With the CS API flow, we additionally need to distinguish server names
-    ...(flow.kind === "csApi" ? [flow.url, serverName] : [flow.serviceUrl]),
+    hasUrl ? transport.url : null,
+    "livekit_service_url" in transport ? transport.livekit_service_url : null,
+    hasUrl ? serverName : null,
  ]) as TransportKey;
 }

@@ -258,23 +258,6 @@ describe("createLivekitBackend", () => {
    },
  );

-  it("prepares a remote SFU's transport on its homeserver, where delegation is not possible", async () => {
-    // Our own homeserver would delegate, so only the SFU being remote can
-    // explain delegation being skipped
-    fetchMock.post(homeserverEndpoint, 401);
-    const remoteTransport: UnstableLivekitTransport = {
-      type: "livekit",
-      url: "wss://sfu.sample.com",
-      server_name: "sample.com",
-    };
-
-    const capabilities = await backend().prepareLocalTransport(remoteTransport);
-
-    expect(capabilities).toEqual({ canDelegateDelayedLeave: false });
-    expect(connections[0].connection.role).toBe("publisher");
-    expect(connections[0].connection.serverName).toBe("sample.com");
-  });
-
  it("waits for the publisher connection to hold its token before the join", async () => {
    fetchMock.post(homeserverEndpoint, 404);
    fetchMock.post(`${exampleServiceUrl}/delegate_delayed_leave`, 404);
@@ -505,27 +488,6 @@ describe("createLivekitBackend", () => {
      expect(remote?.connection.transport).toEqual(carlsTransport);
      expect(remote?.connection.serverName).toBe("sample.com");
    });
-
-    it("connects to a remote publisher's transport on the SFU's homeserver", async () => {
-      const b = await prepared();
-      // Dave has no SFU of his own and publishes on sample.com's
-      const remoteTransport: UnstableLivekitTransport = {
-        type: "livekit",
-        url: "wss://sfu.sample.com",
-        server_name: "sample.com",
-      };
-      b.mediaFor(testScope(), {
-        ...bob(remoteTransport, ["dave-hashed"]),
-        userId: "@dave:example.org",
-      });
-      await flushPromises();
-
-      const remote = connections.find(
-        (c) => c.connection.role === "subscriber",
-      );
-      expect(remote?.connection.transport).toEqual(remoteTransport);
-      expect(remote?.connection.serverName).toBe("sample.com");
-    });
  });
 });

@@ -34,7 +34,7 @@ import {
  trackEpoch,
 } from "../../reactive/ObservableScope";
 import { mapScoped } from "../../utils/mapScoped";
-import { serverNameOf, serverNameOfTransport } from "../../utils/serverName";
+import { serverNameOf } from "../../utils/serverName";
 import {
  type BackendConnection,
  type MediaBackend,
@@ -60,10 +60,7 @@ import {
 import { toMediaConnectionState } from "./connectionState";
 import { createDataChannel$ } from "./DataChannel";
 import { createKeyProvider } from "./KeyProvider";
-import {
-  createLivekitMemberMedia,
-  participantSourcesEqual,
-} from "./LivekitMemberMedia";
+import { createLivekitMemberMedia } from "./LivekitMemberMedia";
 import { createLivekitLocalMedia } from "./LocalMedia";

 export interface LivekitBackendOptions {
@@ -149,37 +146,26 @@ export function createLivekitBackend(
    logger,
  );

-  const ownServerName = serverNameOf(ownMembershipIdentity.userId);
-
  const prepareLocalTransport = async (
    transport: Transport,
  ): Promise<TransportCapabilities> => {
    if (!isUnstableLivekitTransport(transport))
      throw new MatrixRTCError(`Not a LiveKit transport: ${transport.type}`);
-    const serverName = serverNameOfTransport(
+    const locator: TransportLocator = {
      transport,
-      ownMembershipIdentity.userId,
-    );
-    const locator: TransportLocator = { transport, serverName };
-    let canDelegate: Promise<boolean>;
-    if (serverName !== ownServerName) {
-      // Our homeserver only takes over leaves for its own SFUs
-      logger.info(
-        `Publishing on a remote SFU of ${serverName}, delegation is not possible`,
-      );
-      canDelegate = Promise.resolve(false);
-    } else {
-      // Check for support using the same auth flow that we intend to use later
-      const flow = chooseAuthFlow(transport);
-      canDelegate =
-        flow.kind === "openID"
-          ? supportsDelegation(
-              `${flow.serviceUrl}/delegate_delayed_leave`,
-              `transport ${flow.serviceUrl}`,
-              logger,
-            )
-          : homeserverSupportsDelegation;
-    }
+      serverName: serverNameOf(ownMembershipIdentity.userId),
+    };
+    // Delegation goes through whichever service authenticates us as a
+    // publisher, so only that service's support counts
+    const flow = chooseAuthFlow(transport, "publisher");
+    const canDelegate =
+      flow.kind === "openID"
+        ? supportsDelegation(
+            `${flow.serviceUrl}/delegate_delayed_leave`,
+            `transport ${flow.serviceUrl}`,
+            logger,
+          )
+        : homeserverSupportsDelegation;
    localTransport$.next(locator);
    // The membership is only sent once the publisher connection holds its
    // token, so that the LiveKit room exists before anyone subscribes to it:
@@ -218,10 +204,7 @@ export function createLivekitBackend(
        map((transport): TransportLocator | undefined => {
          const raw = transport?.raw;
          return isUnstableLivekitTransport(raw)
-            ? {
-                transport: raw,
-                serverName: serverNameOfTransport(raw, member.userId),
-              }
+            ? { transport: raw, serverName: serverNameOf(member.userId) }
            : undefined;
        }),
        distinctUntilChanged((a, b) => (a && keyFor(a)) === (b && keyFor(b))),
@@ -236,28 +219,22 @@ export function createLivekitBackend(
          const connection = connections.getConnectionForTransport(locator);
          // A member advertising both a `url` and a `livekit_service_url` may
          // have authenticated through either flow, under either identity
-          const participants = connections
+          const participant = connections
            .getParticipantsForTransport(locator)
-            .filter((p) => backendIdentities.includes(p.identity));
-          return connection && participants.length
-            ? { participants, room: connection.livekitRoom }
+            .find((p) => backendIdentities.includes(p.identity));
+          return connection && participant
+            ? { participant, room: connection.livekitRoom }
            : null;
        }),
-        distinctUntilChanged(participantSourcesEqual),
+        distinctUntilChanged(
+          (a, b) => a?.participant === b?.participant && a?.room === b?.room,
+        ),
      ),
    );
    source$.pipe(memberScope.bind()).subscribe((source) => {
-      const transportString = locator$.value
-        ? JSON.stringify(locator$.value.transport)
-        : "no transport";
-      if (source)
-        logger.info(
-          `${member.rtcBackendIdentity}: ${source.participants.length} LiveKit participant(s) matched (${source.participants.map((p) => p.sid).join(", ")}) on ${transportString}`,
-        );
-      else
-        logger.info(
-          `${member.rtcBackendIdentity}: LiveKit participant missing on ${transportString}`,
-        );
+      logger.info(
+        `${member.rtcBackendIdentity}: LiveKit participant ${source ? `matched (${source.participant.sid})` : "missing"} on ${locator$.value ? JSON.stringify(locator$.value.transport) : "no transport"}`,
+      );
    });
    return createLivekitMemberMedia(memberScope, source$, encryptionSystem);
  };
@@ -25,7 +25,7 @@ describe("createLivekitMemberMedia", () => {
    const { participant, publications, room, emitter } = fakes();
    const media = createLivekitMemberMedia(
      testScope(),
-      constant({ participants: [participant], room }),
+      constant({ participant, room }),
      { kind: E2eeType.NONE },
    );
    expect(media.tracks$.value).toEqual([]);
@@ -52,7 +52,7 @@ describe("createLivekitMemberMedia", () => {
    const { participant, publications, room, emitter } = fakes();
    const media = createLivekitMemberMedia(
      testScope(),
-      constant({ participants: [participant], room }),
+      constant({ participant, room }),
      { kind: E2eeType.NONE },
    );
    emitter.emit(
@@ -16,20 +16,13 @@ import {
  RoomEvent,
  type TrackPublication,
 } from "livekit-client";
-import {
-  EMPTY,
-  filter,
-  map,
-  type Observable,
-  of,
-  switchMap,
-  combineLatest,
-} from "rxjs";
+import { EMPTY, filter, map, type Observable, of, switchMap } from "rxjs";

 import { type ObservableScope } from "../../reactive/ObservableScope";
 import { generateItems } from "../../reactive/observable";
 import { E2eeType, type EncryptionSystem } from "../../encryption";
 import { type Behavior } from "../../reactive/Behavior";
+import { mapScoped } from "../../utils/mapScoped";
 import {
  type EncryptionError,
  type LocalMemberMedia,
@@ -40,27 +33,13 @@ import {
  createLivekitMediaTrack,
  createLocalLivekitMediaTrack,
 } from "./LivekitMediaTrack";
-import { shallowEquals as arrayShallowEquals } from "../../utils/array";

 /** Where a member's media comes from: its participant on a room, null while it has none. */
 export type ParticipantSource<P extends Participant = Participant> = {
-  participants: P[];
+  participant: P;
  room: LivekitRoom;
 } | null;

-export function participantSourcesEqual<P extends Participant = Participant>(
-  a: ParticipantSource<P>,
-  b: ParticipantSource<P>,
-): boolean {
-  return (
-    a === b ||
-    (a !== null &&
-      b !== null &&
-      arrayShallowEquals(a.participants, b.participants) &&
-      a.room === b.room)
-  );
-}
-
 /**
 * A member's media from its participant. The only place, with
 * `LivekitMediaTrack`, that reads a LiveKit participant; everything above
@@ -120,28 +99,21 @@ function memberTracks$<P extends Participant, T>(
  ) => T,
 ): Behavior<T[] | null> {
  return scope.behavior(
-    source$.pipe(
-      switchMap((source) => {
-        if (source === null) return of(null);
-        const { participants, room } = source;
-        return combineLatest(
-          participants.map((participant) =>
-            observeParticipantMedia(participant).pipe(
-              generateItems(
-                `${participant.identity} tracks$`,
-                function* () {
-                  for (const publication of participant.trackPublications.values())
-                    yield { keys: [publication.trackSid], data: publication };
-                },
-                (trackScope, publication$) =>
-                  factory(trackScope, participant, publication$.value, room),
-              ),
-            ),
+    mapScoped(scope, source$, (participantScope, { participant, room }) =>
+      participantScope.behavior(
+        observeParticipantMedia(participant).pipe(
+          generateItems(
+            `${participant.identity} tracks$`,
+            function* () {
+              for (const publication of participant.trackPublications.values())
+                yield { keys: [publication.trackSid], data: publication };
+            },
+            (trackScope, publication$) =>
+              factory(trackScope, participant, publication$.value, room),
          ),
-          (...tracks) => tracks.flat(1),
-        );
-      }),
-    ),
+        ),
+      ),
+    ).pipe(switchMap((tracks$) => tracks$ ?? of(null))),
  );
 }

@@ -161,7 +133,7 @@ function encryptionErrors$(
            filter(
              (message) =>
                encryptionSystem.kind === E2eeType.SHARED_KEY ||
-                source.participants.some((p) => message.includes(p.identity)),
+                message.includes(source.participant.identity),
            ),
            map((message): EncryptionError | undefined =>
              message.includes("MissingKey")
@@ -10,6 +10,7 @@ import {
  type LocalParticipant,
  type LocalTrackPublication,
  ParticipantEvent,
+  type Room as LivekitRoom,
 } from "livekit-client";
 import { type Logger } from "matrix-js-sdk/lib/logger";
 import {
@@ -42,11 +43,7 @@ import { type LocalMediaBackend, MediaConnectionState } from "../api";
 import { type TransportLocator } from "./auth";
 import { type Connection } from "./Connection";
 import { type ConnectionMap } from "./ConnectionMap";
-import {
-  createLocalLivekitMemberMedia,
-  type ParticipantSource,
-  participantSourcesEqual,
-} from "./LivekitMemberMedia";
+import { createLocalLivekitMemberMedia } from "./LivekitMemberMedia";
 import { livekitSources } from "./LivekitMediaTrack";
 import { type DesiredMedia, Publisher } from "./Publisher";
 import { toMediaConnectionState } from "./connectionState";
@@ -220,15 +217,17 @@ function participantAndRoom$(
  scope: ObservableScope,
  participant$: Behavior<LocalParticipant | null>,
  connection$: Behavior<Connection | null>,
-): Behavior<ParticipantSource<LocalParticipant>> {
+): Behavior<{ participant: LocalParticipant; room: LivekitRoom } | null> {
  return scope.behavior(
    combineLatest([participant$, connection$]).pipe(
      map(([participant, connection]) =>
        participant && connection
-          ? { participants: [participant], room: connection.livekitRoom }
+          ? { participant, room: connection.livekitRoom }
          : null,
      ),
-      distinctUntilChanged(participantSourcesEqual),
+      distinctUntilChanged(
+        (a, b) => a?.participant === b?.participant && a?.room === b?.room,
+      ),
    ),
  );
 }
@@ -1,172 +0,0 @@
-/*
-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 { MatrixError } from "matrix-js-sdk";
-import { logger } from "matrix-js-sdk/lib/logger";
-import { type CallMembership } from "matrix-js-sdk/lib/matrixrtc";
-import { beforeEach, describe, expect, it, type Mocked, vi } from "vitest";
-
-import { mockRtcMembership, ownMemberMock } from "../../utils/test";
-import { type ClientGetTokenParts } from "./auth/csApi";
-import { findRemotePublishLivekitTransport } from "./RemotePublishTransport";
-
-/** A JWT whose payload states whether the issuing server lets us publish. */
-function jwtWithPublishGrant(canPublish: boolean): string {
-  return [
-    {}, // header
-    { sub: "identity", video: { room: "room", canPublish } }, // payload
-    {}, // signature
-  ]
-    .map((d) => global.btoa(JSON.stringify(d)))
-    .join(".");
-}
-
-const bobSfu = { type: "livekit", url: "wss://sfu.bob.com" };
-const carolSfu = { type: "livekit", url: "wss://sfu.carol.com" };
-const bobsTransport = { ...bobSfu, server_name: "bob.com" };
-const carolsTransport = { ...carolSfu, server_name: "carol.com" };
-
-// Bob is the oldest member, Carol joined after him
-const bob = mockRtcMembership("@bob:bob.com", "BOB", {
-  fociPreferred: [bobSfu],
-  membership: { created_ts: 100 },
-});
-const carol = mockRtcMembership("@carol:carol.com", "CAROL", {
-  fociPreferred: [carolSfu],
-  membership: { created_ts: 200 },
-});
-// Bob's other device, and Dave who publishes on Bob's SFU remotely
-const bobsLaptop = mockRtcMembership("@bob:bob.com", "LAPTOP", {
-  fociPreferred: [bobSfu],
-  membership: { created_ts: 150 },
-});
-const dave = mockRtcMembership("@dave:dave.com", "DAVE", {
-  fociPreferred: [bobsTransport],
-  membership: { created_ts: 160 },
-});
-const legacyErin = mockRtcMembership("@erin:erin.com", "ERIN", {
-  fociPreferred: [
-    { type: "livekit", livekit_service_url: "https://jwt.erin.com" },
-  ],
-  membership: { created_ts: 50 },
-});
-const ourselves = mockRtcMembership(
-  ownMemberMock.userId,
-  ownMemberMock.deviceId,
-  {
-    fociPreferred: [{ type: "livekit", url: "wss://sfu.example.org" }],
-    membership: { created_ts: 10 },
-  },
-);
-
-const csApiMissing = new MatrixError(
-  { errcode: "M_UNRECOGNIZED", error: "" },
-  404,
-);
-
-describe("findRemotePublishLivekitTransport", () => {
-  let client: Mocked<ClientGetTokenParts>;
-  const find = async (
-    memberships: CallMembership[],
-  ): ReturnType<typeof findRemotePublishLivekitTransport> =>
-    findRemotePublishLivekitTransport({
-      client,
-      memberships,
-      ownMembershipIdentity: ownMemberMock,
-      roomId: "!room:example.org",
-      slotId: "m.call#ROOM",
-      logger,
-    });
-
-  beforeEach(() => {
-    client = {
-      _unstable_getLivekitToken: vi
-        .fn()
-        .mockResolvedValue({ jwt: jwtWithPublishGrant(true) }),
-    };
-  });
-
-  it("publishes on the oldest member's SFU with its server_name", async () => {
-    await expect(find([carol, bob])).resolves.toEqual(bobsTransport);
-    expect(client._unstable_getLivekitToken).toHaveBeenCalledTimes(1);
-    expect(client._unstable_getLivekitToken).toHaveBeenCalledWith({
-      url: "wss://sfu.bob.com",
-      server_name: "bob.com",
-      room_id: "!room:example.org",
-      slot_id: "m.call#ROOM",
-      member_id: ownMemberMock.memberId,
-    });
-  });
-
-  it("asks about an SFU once however many members are on it", async () => {
-    client._unstable_getLivekitToken.mockResolvedValue({
-      jwt: jwtWithPublishGrant(false),
-    });
-
-    await expect(find([dave, bobsLaptop, bob])).resolves.toBeNull();
-    expect(client._unstable_getLivekitToken).toHaveBeenCalledTimes(1);
-  });
-
-  it("skips our own membership", async () => {
-    await expect(find([ourselves, bob])).resolves.toEqual(bobsTransport);
-    expect(client._unstable_getLivekitToken).toHaveBeenCalledTimes(1);
-  });
-
-  it("ignores members publishing through a legacy JWT service", async () => {
-    await expect(find([legacyErin, bob])).resolves.toEqual(bobsTransport);
-    expect(client._unstable_getLivekitToken).toHaveBeenCalledTimes(1);
-  });
-
-  it("moves on when a homeserver does not let us publish", async () => {
-    client._unstable_getLivekitToken.mockImplementation(
-      async ({ server_name }) =>
-        Promise.resolve({
-          jwt: jwtWithPublishGrant(server_name === "carol.com"),
-        }),
-    );
-
-    await expect(find([bob, carol])).resolves.toEqual(carolsTransport);
-    expect(client._unstable_getLivekitToken).toHaveBeenCalledTimes(2);
-  });
-
-  it("moves on when a homeserver refuses to issue a token", async () => {
-    client._unstable_getLivekitToken.mockImplementation(
-      async ({ server_name }) =>
-        server_name === "bob.com"
-          ? Promise.reject(
-              new MatrixError(
-                { errcode: "M_FORBIDDEN", error: "Not joined" },
-                403,
-              ),
-            )
-          : Promise.resolve({ jwt: jwtWithPublishGrant(true) }),
-    );
-
-    await expect(find([bob, carol])).resolves.toEqual(carolsTransport);
-  });
-
-  it("finds nothing once all candidates are exhausted", async () => {
-    client._unstable_getLivekitToken.mockResolvedValue({
-      jwt: jwtWithPublishGrant(false),
-    });
-
-    await expect(find([bob, carol])).resolves.toBeNull();
-    expect(client._unstable_getLivekitToken).toHaveBeenCalledTimes(2);
-  });
-
-  it("gives up immediately if our homeserver lacks the CS API", async () => {
-    client._unstable_getLivekitToken.mockRejectedValue(csApiMissing);
-
-    await expect(find([bob, carol])).resolves.toBeNull();
-    expect(client._unstable_getLivekitToken).toHaveBeenCalledTimes(1);
-  });
-
-  it("finds nothing where there are no other members", async () => {
-    await expect(find([ourselves])).resolves.toBeNull();
-    expect(client._unstable_getLivekitToken).not.toHaveBeenCalled();
-  });
-});
@@ -1,105 +0,0 @@
-/*
-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 Logger } from "matrix-js-sdk/lib/logger";
-import {
-  type CallMembership,
-  isUnstableLivekitTransport,
-  type Transport,
-} from "matrix-js-sdk/lib/matrixrtc";
-import { type CallMembershipIdentityParts } from "matrix-js-sdk/lib/matrixrtc/EncryptionManager";
-
-import { isCsApiUnavailable } from "./auth";
-import * as csApi from "./auth/csApi";
-import { decodeSFUJWTPayload } from "./auth/types";
-
-export interface RemotePublishTransportParams {
-  client: csApi.ClientGetTokenParts;
-  /** The members whose SFUs are the candidates. */
-  memberships: CallMembership[];
-  ownMembershipIdentity: CallMembershipIdentityParts;
-  roomId: string;
-  slotId: string;
-  logger: Logger;
-}
-
-/**
- * The SFU of another member that its homeserver lets us publish on, as the
- * transport to advertise, or null where none does. Candidates are tried
- * oldest membership first, each SFU once, and each is checked by asking for a
- * publisher token through our homeserver (MSC4195): a homeserver may restrict
- * remote publishers, which shows as a token without the publish grant.
- */
-export async function findRemotePublishLivekitTransport({
-  client,
-  memberships,
-  ownMembershipIdentity: own,
-  roomId,
-  slotId,
-  logger,
-}: RemotePublishTransportParams): Promise<Transport | null> {
-  logger.info(
-    "No local transport available, looking for another member's SFU to publish on",
-  );
-  const tried = new Set<string>();
-  const byAge = [...memberships].sort((a, b) => a.createdTs() - b.createdTs());
-  for (const membership of byAge) {
-    if (
-      membership.userId === own.userId &&
-      membership.deviceId === own.deviceId
-    )
-      continue;
-    for (const transport of membership.transports) {
-      // Publishing remotely goes through the client-server API, which a JWT
-      // service cannot stand in for, so only a `url` qualifies
-      if (!isUnstableLivekitTransport(transport) || !("url" in transport))
-        continue;
-      const { url } = transport;
-      const serverName = membership.getTransportServerName(transport);
-      const key = JSON.stringify([url, serverName]);
-      if (tried.has(key)) continue;
-      tried.add(key);
-      try {
-        const { jwt } = await csApi.getSFUConfig({
-          client,
-          membership: own,
-          url,
-          serverName,
-          roomId,
-          slotId,
-        });
-        try {
-          // The SFU treats an absent canPublish grant as publishing allowed.
-          if (decodeSFUJWTPayload(jwt).video.canPublish !== false) {
-            logger.info(`Publishing on remote SFU ${url} of ${serverName}`);
-            return { type: "livekit", url, server_name: serverName };
-          }
-          logger.info(
-            `${serverName} does not let us publish on ${url}, skipping`,
-          );
-          continue;
-        } catch (e) {
-          logger.info(
-            `${serverName}: failed to decode SFUJWT payload: ${e}, skipping`,
-          );
-          continue;
-        }
-      } catch (e) {
-        if (isCsApiUnavailable(e)) {
-          // Without the endpoint no further candidate can work
-          logger.warn(
-            `Cannot use the MSC4195 get_token endpoint (${e}), so no remote SFU can be used`,
-          );
-          return null;
-        }
-        logger.warn(`Failed to get a token for ${url} of ${serverName}:`, e);
-        continue;
-      }
-    }
-  }
-  return null;
-}
@@ -7,7 +7,7 @@ Please see LICENSE in the repository root for full details.

 import { afterEach, describe, expect, it, type Mocked, vi } from "vitest";
 import fetchMock from "fetch-mock";
-import { MatrixError } from "matrix-js-sdk";
+import { ConnectionError, MatrixError } from "matrix-js-sdk";
 import { logger } from "matrix-js-sdk/lib/logger";
 import { type UnstableLivekitTransport } from "matrix-js-sdk/lib/matrixrtc";
 import { type CallMembershipIdentityParts } from "matrix-js-sdk/lib/matrixrtc/EncryptionManager";
@@ -144,8 +144,26 @@ describe("getSFUConfig", () => {
    expect(jwtServiceCalls()).toEqual(["/get_token"]);
  });

-  it("uses OpenID when subscribing with url + livekit_service_url transport", async () => {
+  it("uses CS API when subscribing with url + livekit_service_url transport", async () => {
    mockJWTService();
+    expect(
+      await getSFUConfig({
+        ...defaultParams,
+        transport: urlAndServiceUrlTransport,
+      }),
+    ).toEqual(
+      expect.objectContaining({
+        jwt: csApiJWTToken,
+        livekitAlias: "via CS API",
+      }),
+    );
+    expect(client._unstable_getLivekitToken).toHaveBeenCalled();
+    expect(jwtServiceCalls()).toEqual([]);
+  });
+
+  it("falls back to OpenID with url + livekit_service_url transport", async () => {
+    mockJWTService();
+    client._unstable_getLivekitToken.mockRejectedValueOnce(unsupportedError);
    expect(
      await getSFUConfig({
        ...defaultParams,
@@ -157,7 +175,25 @@ describe("getSFUConfig", () => {
        livekitAlias: "via default endpoint",
      }),
    );
-    expect(client._unstable_getLivekitToken).not.toHaveBeenCalled();
+    expect(client._unstable_getLivekitToken).toHaveBeenCalled();
+    expect(jwtServiceCalls()).toEqual(["/get_token"]);
+  });
+
+  it("falls back to OpenID when the widget host refuses the CS API", async () => {
+    mockJWTService();
+    // In widget mode a host without MSC4533 rejects the request before it
+    // reaches the homeserver, with a plain error rather than a Matrix error
+    client._unstable_getLivekitToken.mockRejectedValueOnce(
+      new Error(
+        "The rtc_livekit_get_token action is not supported by the client.",
+      ),
+    );
+    expect(
+      await getSFUConfig({
+        ...defaultParams,
+        transport: urlAndServiceUrlTransport,
+      }),
+    ).toEqual(expect.objectContaining({ jwt: defaultJWTToken }));
    expect(jwtServiceCalls()).toEqual(["/get_token"]);
  });

@@ -186,7 +222,7 @@ describe("getSFUConfig", () => {
    expect(jwtServiceCalls()).toEqual([]);
  });

-  it("does not fall back to OpenID when publishing with url transport", async () => {
+  it("does not fall back to OpenID when publishing", async () => {
    mockJWTService();
    client._unstable_getLivekitToken.mockRejectedValueOnce(unsupportedError);
    await expect(
@@ -219,6 +255,33 @@ describe("getSFUConfig", () => {
    expect(client._unstable_getLivekitToken).not.toHaveBeenCalled();
    expect(jwtServiceCalls()).toEqual(["/sfu/get"]);
  });
+
+  it("does not fall back to OpenID on connection error", async () => {
+    vi.useFakeTimers();
+    try {
+      mockJWTService();
+      const client_ = {
+        ...client,
+        _unstable_getLivekitToken: vi
+          .fn()
+          .mockRejectedValue(new ConnectionError("No connection")),
+      };
+      await Promise.all([
+        expect(
+          getSFUConfig({
+            ...defaultParams,
+            client: client_,
+            transport: urlAndServiceUrlTransport,
+          }),
+        ).rejects.toThrow(expect.any(ConnectionError)),
+        vi.runAllTimersAsync(), // Allow request to be retried
+      ]);
+      expect(client_._unstable_getLivekitToken).toHaveBeenCalled();
+      expect(jwtServiceCalls()).toEqual([]);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
 });

 describe("delegateDelayedLeave", () => {
@@ -299,21 +362,46 @@ describe("delegateDelayedLeave", () => {

 describe("chooseAuthFlow", () => {
  it.each([
-    ["url", urlTransport, { kind: "csApi", url: urlTransport.url }],
+    [
+      "url",
+      "publisher",
+      urlTransport,
+      { kind: "csApi", url: urlTransport.url },
+    ],
+    [
+      "url",
+      "subscriber",
+      urlTransport,
+      { kind: "csApi", url: urlTransport.url },
+    ],
    [
      "livekit_service_url",
+      "publisher",
+      serviceUrlTransport,
+      { kind: "openID", serviceUrl },
+    ],
+    [
+      "livekit_service_url",
+      "subscriber",
      serviceUrlTransport,
      { kind: "openID", serviceUrl },
    ],
    [
      "url + livekit_service_url",
+      "publisher",
      urlAndServiceUrlTransport,
      { kind: "openID", serviceUrl },
    ],
+    [
+      "url + livekit_service_url",
+      "subscriber",
+      urlAndServiceUrlTransport,
+      { kind: "csApi", url: urlTransport.url },
+    ],
  ] as const)(
    "chooses the flow for a %s transport as %s",
-    (_shape, transport, flow) => {
-      expect(chooseAuthFlow(transport)).toEqual(flow);
+    (_shape, role, transport, flow) => {
+      expect(chooseAuthFlow(transport, role)).toEqual(flow);
    },
  );
 });
@@ -48,7 +48,7 @@ function isEndpointUnsupported(e: unknown): boolean {
 * (MSC4533), which the widget API reports as a plain error. A connection
 * error is neither: the endpoint may well exist.
 */
-export function isCsApiUnavailable(e: unknown): boolean {
+function isCsApiUnavailable(e: unknown): boolean {
  if (isEndpointUnsupported(e)) return true;
  return !(e instanceof MatrixError) && !(e instanceof ConnectionError);
 }
@@ -65,10 +65,7 @@ export interface GetSFUConfigParams {
  logger: Logger;
 }

-/**
- * Gets an {@link SFUConfig} appropriate for connecting to a given transport,
- * using whichever auth flow is appropriate.
- */
+/** Authenticates with a transport, through whichever flow suits it and our role. */
 export async function getSFUConfig({
  client,
  membership,
@@ -79,36 +76,48 @@ export async function getSFUConfig({
  role,
  logger,
 }: GetSFUConfigParams): Promise<SFUConfig> {
-  const flow = chooseAuthFlow(transport);
-  if (flow.kind === "openID") {
-    return await openID.getSFUConfig({
+  const viaOpenID = async (serviceUrl: string): Promise<SFUConfig> =>
+    await openID.getSFUConfig({
      client,
      membership,
-      serviceUrl: flow.serviceUrl,
+      serviceUrl,
      roomId,
      slotId,
      role,
      logger,
    });
-  } else {
-    try {
-      return await csApi.getSFUConfig({
-        client,
-        membership,
-        url: flow.url,
-        serverName,
-        roomId,
-        slotId,
-      });
-    } catch (e) {
-      if (isEndpointUnsupported(e)) {
-        logger.error(
-          `Homeserver does not support the MSC4195 get_token endpoint, cannot get token for transport ${flow.url}`,
-        );
-        throw new NoMatrix2AuthorizationService(e as Error);
-      }
-      throw e;
+
+  const flow = chooseAuthFlow(transport, role);
+  if (flow.kind === "openID") return await viaOpenID(flow.serviceUrl);
+
+  try {
+    return await csApi.getSFUConfig({
+      client,
+      membership,
+      url: flow.url,
+      serverName,
+      roomId,
+      slotId,
+    });
+  } catch (e) {
+    // A publisher never falls back: a homeserver that advertises a `url` but
+    // does not implement MSC4195 is misconfigured, and the admin should hear
+    // about it before `livekit_service_url` is deprecated
+    const mayFallBack =
+      role === "subscriber" && "livekit_service_url" in transport;
+    if (mayFallBack && isCsApiUnavailable(e)) {
+      logger.warn(
+        `Cannot use the MSC4195 get_token endpoint (${e}), falling back to the OpenID flow with service ${transport.livekit_service_url}`,
+      );
+      return await viaOpenID(transport.livekit_service_url);
    }
+    if (isEndpointUnsupported(e)) {
+      logger.error(
+        `Homeserver does not support the MSC4195 get_token endpoint, cannot get token for transport ${flow.url}`,
+      );
+      throw new NoMatrix2AuthorizationService(e as Error);
+    }
+    throw e;
  }
 }

@@ -140,7 +149,7 @@ export async function delegateDelayedLeave({
  delayTimeoutMs,
  logger,
 }: DelegateDelayedLeaveParams): Promise<void> {
-  const flow = chooseAuthFlow(transport);
+  const flow = chooseAuthFlow(transport, "publisher");
  if (flow.kind === "csApi") {
    try {
      await csApi.delegateDelayedLeave({
@@ -181,18 +190,23 @@ export type AuthFlow =
  | { kind: "openID"; serviceUrl: string };

 /**
- * Chooses which auth flow to use for a given transport. For now this returns a
- * single auth flow, with no provision for a fallback behavior.
+ * Chooses between the MSC4195 client-server API and the OpenID flow against
+ * the transport's JWT service.
+ *
+ * Only the JWT service's `/sfu/get` endpoint assigns the legacy participant
+ * identity that clients predating MSC4195 expect from anyone advertising a
+ * membership, so a publisher keeps using the JWT service wherever the
+ * transport still offers one, even next to a `url`. A subscriber may use the
+ * client-server API regardless, as nobody matches its identity.
 */
-export function chooseAuthFlow(transport: UnstableLivekitTransport): AuthFlow {
-  if ("url" in transport && !("livekit_service_url" in transport))
-    return { kind: "csApi", url: transport.url };
-  // All other transports use the OpenID flow, even if they contain a `url`.
-  // This is necessary since the auth flow determines the participant identity
-  // format, and we still have older clients out in the wild which would not yet
-  // know to look for a hashed participant identity in case `url` is present in
-  // someone else's transport.
-  // TODO: Once users have updated their clients, choose the CS API flow if
-  // available, keeping OpenID as a fallback.
+export function chooseAuthFlow(
+  transport: UnstableLivekitTransport,
+  role: ConnectionRole,
+): AuthFlow {
+  if ("url" in transport) {
+    const useCsApi =
+      !("livekit_service_url" in transport) || role === "subscriber";
+    if (useCsApi) return { kind: "csApi", url: transport.url };
+  }
  return { kind: "openID", serviceUrl: transport.livekit_service_url };
 }
@@ -34,13 +34,11 @@ export interface SFUConfig {
 }

 /** The parts of the JWT payload the backend reads. */
-export interface SFUJWTPayload {
+interface SFUJWTPayload {
  /** The subject: the participant identity the token carries. */
  sub: string;
  video: {
    room: string;
-    /** Whether the token lets us publish; a homeserver may deny this to remote publishers. */
-    canPublish?: boolean;
  };
 }

@@ -49,7 +47,8 @@ export function extractFullConfigFromToken(sfuConfig: {
  url: string;
  jwt: string;
 }): SFUConfig {
-  const payload = decodeSFUJWTPayload(sfuConfig.jwt);
+  const [, payloadStr] = sfuConfig.jwt.split(".");
+  const payload = JSON.parse(global.atob(payloadStr)) as SFUJWTPayload;
  return {
    jwt: sfuConfig.jwt,
    url: sfuConfig.url,
@@ -57,9 +56,3 @@ export function extractFullConfigFromToken(sfuConfig: {
    livekitIdentity: payload.sub,
  };
 }
-
-/** Decodes the payload of an SFU JWT, without verifying its signature. */
-export function decodeSFUJWTPayload(jwt: string): SFUJWTPayload {
-  const [, payloadStr] = jwt.split(".");
-  return JSON.parse(global.atob(payloadStr)) as SFUJWTPayload;
-}
@@ -1,16 +0,0 @@
-/*
-Copyright 2024 New Vector Ltd.
-
-SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
-Please see LICENSE in the repository root for full details.
-*/
-
-/**
- * Determine whether two arrays are equal by shallow comparison.
- */
-export function shallowEquals<A>(first: A[], second: A[]): boolean {
-  if (first.length !== second.length) return false;
-  for (let i = 0; i < first.length; i++)
-    if (first[i] !== second[i]) return false;
-  return true;
-}
@@ -5,23 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */

-import { type Transport } from "matrix-js-sdk/lib/matrixrtc";
-
 /** The homeserver a Matrix user id belongs to: everything after the first colon. */
 export function serverNameOf(userId: string): string {
  return userId.replace(/^.*?:/, "");
 }
-
-/**
- * The homeserver that operates a transport: the one the transport names, else
- * the one of the member advertising it. A member publishing on another
- * homeserver's SFU (MSC4195) names that homeserver in `server_name`.
- */
-export function serverNameOfTransport(
-  transport: Transport,
-  userId: string,
-): string {
-  return typeof transport.server_name === "string"
-    ? transport.server_name
-    : serverNameOf(userId);
-}
@@ -7,7 +7,6 @@
  padding-top: env(safe-area-inset-top);
  opacity: 1;
  transition: opacity 0.15s;
-  text-align: center;
 }

 /* Pseudo-element for the gradient background */
@@ -53,7 +52,7 @@
    ". . ."
    "primaryButton title secondaryButton"
    ". . .";
-  place-items: center stretch;
+  place-items: center;
  column-gap: var(--cpd-space-2x);
 }

@@ -1228,7 +1228,7 @@ exports[`should have a close button when the host can dismiss us 1`] = `
            Call is not supported
          </h1>
          <p>
-            The server is not configured to work with Element Call and no other call participant provides a usable transport. Please contact your server admin (Domain: example.com, Error Code: MISSING_MATRIX_RTC_TRANSPORT).
+            The server is not configured to work with Element Call. Please contact your server admin (Domain: example.com, Error Code: MISSING_MATRIX_RTC_TRANSPORT).
          </p>
          <button
            class="_button_1nw83_8"
@@ -1381,7 +1381,7 @@ exports[`should render the error page with link back to home 1`] = `
            Call is not supported
          </h1>
          <p>
-            The server is not configured to work with Element Call and no other call participant provides a usable transport. Please contact your server admin (Domain: example.com, Error Code: MISSING_MATRIX_RTC_TRANSPORT).
+            The server is not configured to work with Element Call. Please contact your server admin (Domain: example.com, Error Code: MISSING_MATRIX_RTC_TRANSPORT).
          </p>
          <button
            class="_button_1nw83_8"
@@ -1534,7 +1534,7 @@ exports[`should report correct error for 'Call is not supported' 1`] = `
            Call is not supported
          </h1>
          <p>
-            The server is not configured to work with Element Call and no other call participant provides a usable transport. Please contact your server admin (Domain: example.com, Error Code: MISSING_MATRIX_RTC_TRANSPORT).
+            The server is not configured to work with Element Call. Please contact your server admin (Domain: example.com, Error Code: MISSING_MATRIX_RTC_TRANSPORT).
          </p>
          <button
            class="_button_1nw83_8"
@@ -30,6 +30,9 @@ import {
 } from "@element-hq/matrixrtc-sdk";
 import type * as MatrixRTCSdk from "@element-hq/matrixrtc-sdk";
 import { exampleTransport, mockConfig } from "../utils/test";
+import { GroupCallErrorBoundary } from "../room/GroupCallErrorBoundary";
+import { LeaveToHomeProvider } from "../LeaveToHomeContext";
+import { ElementCallError, ErrorCode } from "../utils/errors";

 // Mock url params hook to avoid environment-dependent snapshot churn.
 vi.mock("../UrlParams", () => ({
@@ -493,4 +496,38 @@ describe("DeveloperSettingsTab", () => {
      );
    });
  });
+  describe("throw test error", () => {
+    it("throws an ElementCallError that the error boundary shows", async () => {
+      const user = userEvent.setup();
+      const client = createMockMatrixClient();
+      const onError = vi.fn();
+
+      render(
+        <LeaveToHomeProvider value={vi.fn()}>
+          <GroupCallErrorBoundary
+            onError={onError}
+            recoveryActionHandler={vi.fn()}
+          >
+            <TooltipProvider>
+              <DeveloperSettingsTab
+                client={client}
+                env={{} as unknown as ImportMetaEnv}
+                vm={outOfCallDeveloperSettingsTabViewModel}
+              />
+            </TooltipProvider>
+          </GroupCallErrorBoundary>
+        </LeaveToHomeProvider>,
+      );
+
+      await user.click(
+        screen.getByRole("button", { name: "Throw test error" }),
+      );
+
+      expect(await screen.findByText("Something went wrong")).toBeVisible();
+      expect(onError).toHaveBeenCalledOnce();
+      const error = onError.mock.calls[0][0] as unknown;
+      expect(error).toBeInstanceOf(ElementCallError);
+      expect((error as ElementCallError).code).toBe(ErrorCode.UNKNOWN_ERROR);
+    });
+  });
 });
@@ -22,6 +22,7 @@ import {
 import { logger } from "matrix-js-sdk/lib/logger";
 import { type UnstableLivekitTransport } from "matrix-js-sdk/lib/matrixrtc";
 import {
+  Button,
  EditInPlace,
  ErrorMessage,
  Root as Form,
@@ -72,6 +73,7 @@ import {
 } from "@element-hq/matrixrtc-sdk";
 import { useBehavior } from "../useBehavior";
 import { type ViewModel } from "../state/ViewModel.ts";
+import { type ElementCallError, UnknownCallError } from "../utils/errors.ts";

 /**
 * The state of MatrixRTC's media key rotation.
@@ -189,6 +191,22 @@ export const DeveloperSettingsTab: FC<Props> = ({

  const urlParams = useUrlParams();

+  // An error thrown from a click handler never reaches an error boundary, so
+  // the button only records it and the next render throws it instead.
+  const [errorToThrow, setErrorToThrow] = useState<ElementCallError | null>(
+    null,
+  );
+  const throwTestError = useCallback(
+    () =>
+      setErrorToThrow(
+        new UnknownCallError(
+          new Error("Test error thrown from the developer settings"),
+        ),
+      ),
+    [],
+  );
+  if (errorToThrow !== null) throw errorToThrow;
+
  const MediaQualitySettings: React.FC<{
    id: string;
    header: string;
@@ -517,7 +535,7 @@ export const DeveloperSettingsTab: FC<Props> = ({
                client,
                membership: { userId, deviceId, memberId: "" },
                transport,
-                serverName: transport.server_name ?? serverName,
+                serverName,
                roomId,
                slotId: "org.example.fake-slot#room",
                role: "publisher",
@@ -649,6 +667,10 @@ export const DeveloperSettingsTab: FC<Props> = ({
      <Separator />
      <AudioProcessingSettings />
      <Separator />
+      <Button kind="secondary" destructive onClick={throwTestError}>
+        {t("developer_mode.throw_error_button")}
+      </Button>
+      <Separator />
      <p>{t("developer_mode.environment_variables")}</p>
      <pre className={styles.pre}>{JSON.stringify(env, null, 2)}</pre>
      <p>{t("developer_mode.url_params")}</p>
@@ -635,6 +635,21 @@ exports[`DeveloperSettingsTab > renders and matches snapshot 1`] = `
    data-orientation="horizontal"
    role="separator"
  />
+  <button
+    class="_button_1nw83_8 _destructive_1nw83_110"
+    data-kind="secondary"
+    data-size="lg"
+    role="button"
+    tabindex="0"
+  >
+    Throw test error
+  </button>
+  <div
+    class="_separator_13qwf_8"
+    data-kind="primary"
+    data-orientation="horizontal"
+    role="separator"
+  />
  <p>
    Environment variables
  </p>
@@ -111,8 +111,6 @@ describe("widget", () => {
      receiveToDevice: sendRecvToDevice,
      turnServers: false,
      rtcTransports: true,
-      rtcLivekitGetToken: true,
-      rtcLivekitDelegateDelayedLeave: true,
      sendDelayedEvents: true,
      updateDelayedEvents: true,
      sendSticky: true,
@@ -175,8 +175,6 @@ export const initializeWidget = (
          receiveToDevice: sendRecvToDevice,
          turnServers: false,
          rtcTransports: true,
-          rtcLivekitGetToken: true,
-          rtcLivekitDelegateDelayedLeave: true,
          sendDelayedEvents: true,
          updateDelayedEvents: true,
          sendSticky: true,
Author	SHA1	Message	Date
Timo K.	5597ef2249	Add playwright test to check EW error screen dismiss on room switch	2026-10-14 12:45:49 +02:00
Timo K.	f60a63e20c	Add a devtool button to mock an error	2026-10-14 11:36:54 +02:00