Cover the subscriber token path, widget fallback and server names

src/livekit/auth/openID.test.ts

@@ -169,6 +169,36 @@ describe("getSFUConfig", () => {
     });
   });
 
+  it("should use the default endpoint when subscribing", async () => {
+    fetchMock.post("https://sfu.example.org/get_token", (url, opts) => {
+      const body = JSON.parse(opts.body as string);
+      expect(body).toMatchObject({
+        room_id: "!example_room_id",
+        slot_id: "m.call#ROOM",
+        member: {
+          id: ownMemberMock.memberId,
+          claimed_user_id: ownMemberMock.userId,
+          claimed_device_id: ownMemberMock.deviceId,
+        },
+      });
+      return { status: 200, body: { url: serviceUrl, jwt: testJWTToken } };
+    });
+    const config = await getSFUConfig({ ...params, role: "subscriber" });
+    expect(config.jwt).toBe(testJWTToken);
+    expect(fetchMock.called("https://sfu.example.org/sfu/get")).toBe(false);
+  });
+
+  it("should fail when subscribing if the default endpoint is missing", async () => {
+    // Nothing but the catch-all 404 answers the default endpoint. Subscribers
+    // must not fall back to the legacy endpoint, which would hand them a
+    // legacy identity.
+    await expect(
+      getSFUConfig({ ...params, role: "subscriber" }),
+    ).rejects.toThrow(FailToGetOpenIdToken);
+    expect(fetchMock.called("https://sfu.example.org/get_token")).toBe(true);
+    expect(fetchMock.called("https://sfu.example.org/sfu/get")).toBe(false);
+  });
+
   it("should retry fetching the openid token", async () => {
     let count = 0;
     matrixClient.getOpenIdToken.mockImplementation(async () => {

src/state/SessionBehaviors.test.ts

@@ -1,16 +1,25 @@
 /*
-Copyright 2025 Element Creations Ltd.
+Copyright 2025, 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, vi } from "vitest";
-import { MatrixRTCSessionEvent } from "matrix-js-sdk/lib/matrixrtc";
+import {
+  MatrixRTCSessionEvent,
+  type Transport,
+  type UnstableLivekitTransport,
+} from "matrix-js-sdk/lib/matrixrtc";
 import { EventEmitter } from "events";
 
-import { createKeyRotationSuppressed$ } from "./SessionBehaviors";
-import { testScope } from "../utils/test";
+import {
+  createKeyRotationSuppressed$,
+  membershipsAndTransports$,
+} from "./SessionBehaviors";
+import { Epoch } from "./ObservableScope";
+import { constant } from "./Behavior";
+import { mockRtcMembership, testScope } from "../utils/test";
 
 describe("SessionBehaviors", () => {
   describe("createKeyRotationSuppressed$", () => {
@@ -38,4 +47,54 @@ describe("SessionBehaviors", () => {
       expect(keyRotationSuppressed$.value).toBe(false);
     });
   });
+
+  describe("membershipsAndTransports$", () => {
+    const serviceTransport: UnstableLivekitTransport = {
+      type: "livekit",
+      livekit_service_url: "https://lk.example.org",
+    };
+    const urlTransport: UnstableLivekitTransport = {
+      type: "livekit",
+      url: "wss://sfu.sample.com",
+    };
+
+    it("locates each member's transport on the member's homeserver", () => {
+      const bob = mockRtcMembership("@bob:example.org", "DEV000", {
+        fociPreferred: [serviceTransport],
+      });
+      const carl = mockRtcMembership("@carl:sample.com", "DEV111", {
+        fociPreferred: [urlTransport],
+      });
+
+      const { membershipsWithTransport$, transports$ } =
+        membershipsAndTransports$(
+          testScope(),
+          constant(new Epoch([bob, carl])),
+        );
+
+      expect(transports$.value.value).toEqual([
+        { transport: serviceTransport, serverName: "example.org" },
+        { transport: urlTransport, serverName: "sample.com" },
+      ]);
+      expect(
+        membershipsWithTransport$.value.value.map(
+          (m) => m.transport?.serverName,
+        ),
+      ).toEqual(["example.org", "sample.com"]);
+    });
+
+    it("leaves out members without a LiveKit transport", () => {
+      const dave = mockRtcMembership("@dave:example.org", "DEV222", {
+        fociPreferred: [{ type: "something-else" } as Transport],
+      });
+
+      const { membershipsWithTransport$, transports$ } =
+        membershipsAndTransports$(testScope(), constant(new Epoch([dave])));
+
+      expect(transports$.value.value).toEqual([]);
+      expect(membershipsWithTransport$.value.value).toEqual([
+        { membership: dave, transport: undefined },
+      ]);
+    });
+  });
 });