[SDK] Cover transport discovery, the join options and the room options

Unit tests for the pieces that had none: which transport the local
member advertises (override, homeserver, fallback, none), what the js-sdk
join is called with, how a publish request becomes LiveKit capture and
publish options, and the room options the connection factory builds from
the initial requests and the media quality settings, including what a
resolved connection reports while it is up. The backend's `mediaFor` gains
the cases from Element Call's member matching tests: a member on another
transport, a member changing transport, and a member without one.

sdk/src/media-backend/livekit/ConnectionFactory.test.ts

@@ -0,0 +1,173 @@
+/*
+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 {
+  ConnectionState as LivekitConnectionState,
+  type RoomOptions,
+} from "livekit-client";
+import { logger } from "matrix-js-sdk/lib/logger";
+import { type UnstableLivekitTransport } from "matrix-js-sdk/lib/matrixrtc";
+import { describe, expect, it, vi } from "vitest";
+
+import { type MediaQuality } from "../../config";
+import { type PublishRequest } from "../../media-api";
+import { constant } from "../../reactive/Behavior";
+import { ownMemberMock, testScope } from "../../utils/test";
+import { testJWTToken } from "../../utils/test-fixtures";
+import { type ClientGetTokenParts, type ClientOpenIDParts } from "./auth";
+import {
+  LivekitConnectionFactory,
+  type ResolvedConnection,
+} from "./ConnectionFactory";
+import { exampleTransport } from "./test";
+
+const urlTransport: UnstableLivekitTransport = {
+  type: "livekit",
+  url: "wss://sfu.example.org",
+};
+
+function client(): ClientGetTokenParts & ClientOpenIDParts {
+  return {
+    getOpenIdToken: vi.fn(),
+    _unstable_getLivekitToken: vi.fn().mockResolvedValue({ jwt: testJWTToken }),
+  };
+}
+
+/**
+ * Builds a subscriber connection and hands back the options its LiveKit room
+ * was built with. The room is a real one: it never connects, and its options
+ * are what the factory gave it, filled in with LiveKit's defaults.
+ */
+function create(
+  publish: PublishRequest[],
+  mediaQuality?: MediaQuality,
+  audioOutputDeviceId?: string,
+  transport = exampleTransport,
+): { connection: ResolvedConnection; options: RoomOptions } {
+  const factory = new LivekitConnectionFactory(
+    client(),
+    "!room:example.org",
+    "m.call#ROOM",
+    publish,
+    constant(audioOutputDeviceId),
+    undefined,
+    mediaQuality,
+  );
+  const connection = factory.createConnection(
+    testScope(),
+    "subscriber",
+    transport,
+    "example.org",
+    ownMemberMock,
+    logger,
+  ) as ResolvedConnection;
+  return { connection, options: connection.livekitRoom.options };
+}
+
+describe("LivekitConnectionFactory", () => {
+  it("builds the room on the defaults where nothing is requested", () => {
+    const { options } = create([]);
+
+    expect(options.publishDefaults).toMatchObject({ videoCodec: "vp8" });
+    expect(options.videoCaptureDefaults).toMatchObject({
+      resolution: expect.objectContaining({ height: 720 }),
+    });
+    expect(options.audioOutput).toEqual({ deviceId: undefined });
+    expect(options.e2ee).toBeUndefined();
+  });
+
+  it("makes the initial microphone request the room's audio defaults", () => {
+    const { options } = create([
+      {
+        source: "microphone",
+        deviceId: "mic-1",
+        capture: {
+          echoCancellation: false,
+          noiseSuppression: true,
+          autoGainControl: false,
+        },
+      },
+    ]);
+
+    expect(options.audioCaptureDefaults).toMatchObject({
+      deviceId: "mic-1",
+      echoCancellation: false,
+      noiseSuppression: true,
+      autoGainControl: false,
+    });
+  });
+
+  it("makes the initial camera request the room's video and publish defaults", () => {
+    const { options } = create(
+      [
+        {
+          source: "camera",
+          deviceId: "cam-1",
+          capture: {
+            resolution: { width: 1920, height: 1080, frameRate: 60 },
+            maxBitrate: 4_000_000,
+            maxFramerate: 60,
+            codec: "vp9",
+          },
+        },
+      ],
+      { video_codec: "h264" },
+    );
+
+    expect(options.videoCaptureDefaults).toMatchObject({
+      deviceId: "cam-1",
+      resolution: { width: 1920, height: 1080, frameRate: 60 },
+    });
+    // The request wins over the media quality settings
+    expect(options.publishDefaults).toMatchObject({
+      videoEncoding: { maxBitrate: 4_000_000, maxFramerate: 60 },
+      videoCodec: "vp9",
+    });
+  });
+
+  it("applies the media quality settings where the requests leave the defaults", () => {
+    const { options } = create([{ source: "camera" }], {
+      video_codec: "av1",
+      video: { max_bitrate: 900_000, max_framerate: 24 },
+    });
+
+    expect(options.publishDefaults).toMatchObject({
+      videoEncoding: { maxBitrate: 900_000, maxFramerate: 24 },
+      videoCodec: "av1",
+    });
+  });
+
+  it("plays on the output device selected when the room is built", () => {
+    const { options } = create([], undefined, "speaker");
+    expect(options.audioOutput).toEqual({ deviceId: "speaker" });
+  });
+
+  it("reports what it fetched while connected, and nothing before or after", async () => {
+    const { connection } = create([], undefined, undefined, urlTransport);
+    // The room must not reach for the network; its state is left as it is
+    vi.spyOn(connection.livekitRoom, "connect").mockResolvedValue(undefined);
+    vi.spyOn(connection.livekitRoom, "disconnect").mockResolvedValue(undefined);
+    expect(connection.resolved$.value).toBeUndefined();
+
+    await connection.start();
+
+    expect(connection.state$.value).toEqual({
+      state: "authenticated",
+      livekitState: LivekitConnectionState.Disconnected,
+    });
+    expect(connection.resolved$.value).toEqual({
+      type: "livekit",
+      url: "wss://sfu.example.org",
+      token: testJWTToken,
+      roomAlias: "!example_room_id",
+      identity: "@me:example.org:ABCDEF",
+    });
+
+    await connection.stop();
+    expect(connection.resolved$.value).toBeUndefined();
+  });
+});

sdk/src/media-backend/livekit/LivekitBackend.test.ts

@@ -390,6 +390,86 @@ describe("createLivekitBackend", () => {
       expect(media.tracks$.value).toBeNull();
     });
 
+    it("has no media for a member on another transport until it shows up there", async () => {
+      const b = await prepared();
+      const media = b.mediaFor(testScope(), bob(otherTransport, [legacyId]));
+      await flushPromises();
+      const remote = connections.find(
+        (c) => c.connection.role === "subscriber",
+      );
+      expect(remote?.connection.transport).toEqual(otherTransport);
+
+      // The same identity on our own transport is someone else's room
+      connections[0].participants$.next([
+        mockRemoteParticipant({
+          identity: legacyId,
+          trackPublications: new Map(),
+        }),
+      ]);
+      await flushPromises();
+      expect(media.tracks$.value).toBeNull();
+
+      remote!.participants$.next([
+        mockRemoteParticipant({
+          identity: legacyId,
+          trackPublications: new Map(),
+        }),
+      ]);
+      await flushPromises();
+      expect(media.tracks$.value).toEqual([]);
+    });
+
+    it("follows a member to a new transport, and drops the old connection with it", async () => {
+      const b = await prepared();
+      const transport$ = new BehaviorSubject(
+        bob(bothTransport, [legacyId]).transport$.value,
+      );
+      const media = b.mediaFor(testScope(), {
+        ...bob(bothTransport, [legacyId]),
+        transport$,
+      });
+      connections[0].participants$.next([
+        mockRemoteParticipant({
+          identity: legacyId,
+          trackPublications: new Map(),
+        }),
+      ]);
+      await flushPromises();
+      expect(media.tracks$.value).toEqual([]);
+
+      transport$.next(bob(otherTransport, [legacyId]).transport$.value);
+      await flushPromises();
+
+      expect(media.tracks$.value).toBeNull();
+      const remote = connections.find(
+        (c) => c.connection.role === "subscriber",
+      );
+      expect(remote?.connection.transport).toEqual(otherTransport);
+      expect(b.connections$.value.map(({ transport }) => transport)).toEqual([
+        bothTransport,
+        otherTransport,
+      ]);
+
+      transport$.next(bob(bothTransport, [legacyId]).transport$.value);
+      await flushPromises();
+      expect(media.tracks$.value).toEqual([]);
+      expect(b.connections$.value.map(({ transport }) => transport)).toEqual([
+        bothTransport,
+      ]);
+    });
+
+    it("has no media for a member without a transport, and opens no connection", async () => {
+      const b = await prepared();
+      const media = b.mediaFor(testScope(), {
+        ...bob(bothTransport, [legacyId]),
+        transport$: constant(undefined),
+      });
+      await flushPromises();
+
+      expect(media.tracks$.value).toBeNull();
+      expect(connections).toHaveLength(1);
+    });
+
     it("connects to a remote member's transport on the member's homeserver", async () => {
       const b = await prepared();
       const carlsTransport: UnstableLivekitTransport = {

sdk/src/media-backend/livekit/publishOptions.test.ts

@@ -0,0 +1,145 @@
+/*
+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, it } from "vitest";
+
+import {
+  audioCaptureOptions,
+  screenShareCaptureOptions,
+  screenSharePublishOptions,
+  videoCaptureOptions,
+  videoPublishOptions,
+} from "./publishOptions";
+
+describe("audioCaptureOptions", () => {
+  it("leaves a bare request to the room defaults", () => {
+    expect(audioCaptureOptions({ source: "microphone" })).toBeUndefined();
+  });
+
+  it("carries the device and the processing flags", () => {
+    expect(
+      audioCaptureOptions({
+        source: "microphone",
+        deviceId: "mic-1",
+        capture: { echoCancellation: false, noiseSuppression: true },
+      }),
+    ).toEqual({
+      deviceId: "mic-1",
+      echoCancellation: false,
+      noiseSuppression: true,
+    });
+  });
+
+  it("drops an empty device id", () => {
+    expect(
+      audioCaptureOptions({
+        source: "microphone",
+        deviceId: "",
+        capture: { autoGainControl: false },
+      }),
+    ).toEqual({ autoGainControl: false });
+  });
+});
+
+describe("videoCaptureOptions", () => {
+  it("leaves a request without device, processor or resolution to the room defaults", () => {
+    expect(
+      videoCaptureOptions({
+        source: "camera",
+        capture: { maxBitrate: 1_000_000 },
+      }),
+    ).toBeUndefined();
+  });
+
+  it("carries the device and the resolution, but not the encoding", () => {
+    expect(
+      videoCaptureOptions({
+        source: "camera",
+        deviceId: "cam-1",
+        capture: {
+          resolution: { width: 1920, height: 1080, frameRate: 60 },
+          maxBitrate: 4_000_000,
+        },
+      }),
+    ).toEqual({
+      deviceId: "cam-1",
+      resolution: { width: 1920, height: 1080, frameRate: 60 },
+    });
+  });
+});
+
+describe("videoPublishOptions", () => {
+  it("is nothing without capture settings", () => {
+    expect(videoPublishOptions(undefined)).toBeUndefined();
+  });
+
+  it("is empty for settings that only set the resolution", () => {
+    expect(
+      videoPublishOptions({ resolution: { width: 640, height: 360 } }),
+    ).toEqual({});
+  });
+
+  it("maps the bitrate, framerate and codec to the encoding", () => {
+    expect(
+      videoPublishOptions({
+        maxBitrate: 4_000_000,
+        maxFramerate: 60,
+        codec: "vp9",
+      }),
+    ).toEqual({
+      videoEncoding: { maxBitrate: 4_000_000, maxFramerate: 60 },
+      videoCodec: "vp9",
+    });
+  });
+});
+
+describe("screenShareCaptureOptions", () => {
+  it("captures the audio without processing by default", () => {
+    expect(screenShareCaptureOptions({ source: "screenShare" })).toEqual({
+      audio: {
+        autoGainControl: false,
+        noiseSuppression: false,
+        voiceIsolation: false,
+      },
+      selfBrowserSurface: "include",
+      surfaceSwitching: "include",
+      systemAudio: "include",
+    });
+  });
+
+  it("leaves the audio out on request and carries the resolution", () => {
+    expect(
+      screenShareCaptureOptions({
+        source: "screenShare",
+        audio: false,
+        capture: { resolution: { width: 1280, height: 720 } },
+      }),
+    ).toMatchObject({
+      audio: false,
+      resolution: { width: 1280, height: 720 },
+    });
+  });
+});
+
+describe("screenSharePublishOptions", () => {
+  it("is nothing without capture settings", () => {
+    expect(screenSharePublishOptions(undefined)).toBeUndefined();
+  });
+
+  it("maps the bitrate, framerate and codec to the screen share encoding", () => {
+    expect(
+      screenSharePublishOptions({
+        maxBitrate: 5_000_000,
+        maxFramerate: 15,
+        codec: "av1",
+      }),
+    ).toEqual({
+      screenShareEncoding: { maxBitrate: 5_000_000, maxFramerate: 15 },
+      videoCodec: "av1",
+    });
+  });
+});