Run the lobby on the SDK's local media and keep its tracks through the

join The lobby captured its own LiveKit tracks and the join captured again: two permission prompts, a grey tile while the camera restarted, and the background pipeline built twice. The lobby now opens the devices on the SDK's `LocalMedia`, follows the mute switches as they change (they start off until the devices are enumerated), the device choice and the processor through controls shared with the call view model, and the call joins with that media, so the tile carries the very track the lobby previewed. `useBehavior` subscribes without `useSyncExternalStore`, which left a view without a re-render for an emission React had been told about, about one time in three, when its store had switched. The LiveKit preview hook and the processor sync helpers go, with `@livekit/components-react`. Background effects run under the dev server: the node polyfill no longer rewrites MediaPipe's WASM loader. Taken from fkwp's 2fad4e08 on spec/background-effects/2-pipeline (#4282). Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
[SDK] Capture local media ahead of the join and hand it to the participation
2026-11-07 00:52:28 +00:00 · 2026-11-04 18:59:11 +01:00 · 2026-11-04 18:42:59 +01:00 · 2026-11-04 18:32:32 +01:00 · 2026-11-04 16:27:52 +01:00 · 2026-11-04 02:30:37 +00:00
84 changed files with 3317 additions and 1022 deletions
@@ -0,0 +1,135 @@
+name: Build & publish the component package for releases
+
+on:
+  release:
+    types: [published]
+  pull_request:
+    types:
+      - synchronize
+      - opened
+      - labeled
+  push:
+    branches: [main]
+
+# Each job asks for what it needs
+permissions: {}
+
+jobs:
+  versioning:
+    name: Versioning
+    runs-on: ubuntu-latest
+    outputs:
+      DRY_RUN: ${{ steps.dry_run.outputs.DRY_RUN }}
+      PREFIXED_VERSION: ${{ steps.prefixed_version.outputs.PREFIXED_VERSION }}
+      TAG: ${{ steps.tag.outputs.TAG }}
+    steps:
+      - name: Calculate VERSION
+        # Safely store dynamic values in environment variables
+        # to prevent shell injection (template-injection)
+        run: |
+          if [ "$EVENT_NAME" = "release" ]; then
+            echo "VERSION=$RELEASE_TAG" >> "$GITHUB_ENV"
+          else
+            echo "VERSION=v0.0.0-pre.0" >> "$GITHUB_ENV"
+          fi
+        env:
+          RELEASE_TAG: ${{ github.event.release.tag_name }}
+          EVENT_NAME: ${{ github.event_name }}
+      - id: dry_run
+        name: Set DRY_RUN
+        # A dry run for everything but releases, so that a broken package shows up
+        # ahead of a release
+        run: echo "DRY_RUN=${{ github.event_name != 'release' }}" >> "$GITHUB_OUTPUT"
+      - id: prefixed_version
+        name: Set PREFIXED_VERSION
+        run: echo "PREFIXED_VERSION=${VERSION}" >> "$GITHUB_OUTPUT"
+      - id: tag
+        # latest = a proper release
+        # other = anything else
+        name: Set tag
+        run: |
+          if [[ "${VERSION}" =~ ^v[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+            echo "TAG=latest" >> "$GITHUB_OUTPUT"
+          elif [[ "${VERSION}" =~ ^v[0-9]+\.[0-9]+\.[0-9]+\-rc\.[0-9]+$ ]]; then
+            echo "TAG=rc" >> "$GITHUB_OUTPUT"
+          else
+            echo "TAG=other" >> "$GITHUB_OUTPUT"
+          fi
+
+  publish_npm:
+    needs: versioning
+    name: Publish NPM
+    runs-on: ubuntu-latest
+    outputs:
+      ARTIFACT_VERSION: ${{ steps.artifact_version.outputs.ARTIFACT_VERSION }}
+    permissions:
+      contents: read
+      id-token: write # Allow npm to authenticate as a trusted publisher
+    steps:
+      - name: Checkout
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+        with:
+          persist-credentials: false
+      - name: Enable Corepack
+        run: corepack enable
+      - name: Setup node
+        uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
+        # No dependency cache: a release build must not restore one another workflow could have poisoned
+        with:
+          node-version-file: .node-version
+          registry-url: "https://registry.npmjs.org"
+      # Layered like build-element-call.yaml, so a PR paired with a matrix-js-sdk branch
+      # builds against it; a release pins the SDK, so layered.sh leaves it as locked
+      - name: Install dependencies
+        run: scripts/layered.sh --ignore-pnpmfile
+        env:
+          PR_HEAD_REPO_OWNER: ${{ github.event.pull_request.head.repo.owner.login }}
+      - name: Build component
+        run: pnpm build:component:production
+        env:
+          VITE_APP_VERSION: component-${{ needs.versioning.outputs.PREFIXED_VERSION }}
+          NODE_OPTIONS: "--max-old-space-size=4096"
+
+      # `devEngines` (pnpm only, which npm refuses) and the `prepare` build exist for
+      # git-dependency installs; the published package is already built
+      - name: Publish npm
+        working-directory: component
+        run: |
+          jq 'del(.devEngines, .scripts)' package.json > package.json.tmp && mv package.json.tmp package.json
+          npm version ${NEEDS_VERSIONING_OUTPUTS_PREFIXED_VERSION} --no-git-tag-version
+          echo "ARTIFACT_VERSION=$(jq '.version' --raw-output package.json)" >> "$GITHUB_ENV"
+          npm publish --provenance --access public --tag ${NEEDS_VERSIONING_OUTPUTS_TAG} ${{ needs.versioning.outputs.DRY_RUN == 'true' && '--dry-run' || '' }}
+        env:
+          NEEDS_VERSIONING_OUTPUTS_PREFIXED_VERSION: ${{ needs.versioning.outputs.PREFIXED_VERSION }}
+          NEEDS_VERSIONING_OUTPUTS_TAG: ${{ needs.versioning.outputs.TAG }}
+
+      - id: artifact_version
+        name: Output artifact version
+        run: echo "ARTIFACT_VERSION=${ARTIFACT_VERSION}" >> "$GITHUB_OUTPUT"
+
+  release_notes:
+    needs: [versioning, publish_npm]
+    if: ${{ needs.versioning.outputs.DRY_RUN == 'false' }}
+    name: Update release notes
+    runs-on: ubuntu-latest
+    # Shared with publish-embedded-packages.yaml, which appends to the same release: two
+    # appends at once would each write back the body without the other's section
+    concurrency:
+      group: release-notes-${{ github.event.release.tag_name || github.run_id }}
+      cancel-in-progress: false
+    permissions:
+      contents: write # to update release notes
+    steps:
+      - name: Add release notes
+        uses: softprops/action-gh-release@3bb12739c298aeb8a4eeaf626c5b8d85266b0e65 # v2
+        with:
+          append_body: true
+          body: |
+
+            ## React component (experimental)
+
+            Element Call as a React component, rendered in the host's page instead of in an iframe.
+
+            ```
+            npm install @element-hq/element-call-component@${{ needs.publish_npm.outputs.ARTIFACT_VERSION }}
+            ```
@@ -283,6 +283,11 @@ jobs:
    if: always()
    name: Update release notes
    runs-on: ubuntu-latest
+    # Shared with publish-component.yaml, which appends to the same release: two appends
+    # at once would each write back the body without the other's section
+    concurrency:
+      group: release-notes-${{ github.event.release.tag_name || github.run_id }}
+      cancel-in-progress: false
    permissions:
      contents: write # to update release notes
    steps:
@@ -289,8 +289,14 @@ callback; with one, it asks the host to unmount it instead. The
 [global JS controls](./docs/controls.md) on `window` are unchanged and remain
 page-wide, so with several instances on one page they apply to all of them.

-The package is not published yet. A host installs it as a git dependency on the
-`component` directory of this repository,
+Each release publishes the package to npm, with the same version as the release:
+
+```sh
+npm install @element-hq/element-call-component
+```
+
+To use an unreleased commit, a host can instead install it as a git dependency
+on the `component` directory of this repository,

 ```json
 "@element-hq/element-call-component": "github:element-hq/element-call#main&path:/component"
@@ -0,0 +1,661 @@
+                    GNU AFFERO GENERAL PUBLIC LICENSE
+                       Version 3, 19 November 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
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+
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+
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+
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+
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+
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+
+  9. Acceptance Not Required for Having Copies.
+
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+occurring solely as a consequence of using peer-to-peer transmission
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+
+  10. Automatic Licensing of Downstream Recipients.
+
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+
+  11. Patents.
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+
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+
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+
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+
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+
+  A patent license is "discriminatory" if it does not include within
+the scope of its coverage, prohibits the exercise of, or is
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+for and in connection with specific products or compilations that
+contain the covered work, unless you entered into that arrangement,
+or that patent license was granted, prior to 28 March 2007.
+
+  Nothing in this License shall be construed as excluding or limiting
+any implied license or other defenses to infringement that may
+otherwise be available to you under applicable patent law.
+
+  12. No Surrender of Others' Freedom.
+
+  If conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot convey a
+covered work so as to satisfy simultaneously your obligations under this
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+not convey it at all.  For example, if you agree to terms that obligate you
+to collect a royalty for further conveying from those to whom you convey
+the Program, the only way you could satisfy both those terms and this
+License would be to refrain entirely from conveying the Program.
+
+  13. Remote Network Interaction; Use with the GNU General Public License.
+
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+Program, your modified version must prominently offer all users
+interacting with it remotely through a computer network (if your version
+supports such interaction) an opportunity to receive the Corresponding
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+following paragraph.
+
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+permission to link or combine any covered work with a work licensed
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+License will continue to apply to the part which is the covered work,
+but the work with which it is combined will remain governed by version
+3 of the GNU General Public License.
+
+  14. Revised Versions of this License.
+
+  The Free Software Foundation may publish revised and/or new versions of
+the GNU Affero General Public License from time to time.  Such new versions
+will be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+  Each version is given a distinguishing version number.  If the
+Program specifies that a certain numbered version of the GNU Affero General
+Public License "or any later version" applies to it, you have the
+option of following the terms and conditions either of that numbered
+version or of any later version published by the Free Software
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+GNU Affero General Public License, you may choose any version ever published
+by the Free Software Foundation.
+
+  If the Program specifies that a proxy can decide which future
+versions of the GNU Affero General Public License can be used, that proxy's
+public statement of acceptance of a version permanently authorizes you
+to choose that version for the Program.
+
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+permissions.  However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source.  For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code.  There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+<https://www.gnu.org/licenses/>.
@@ -0,0 +1,6 @@
+Licensees holding a valid commercial license with Element may use this
+software in accordance with the terms contained in a written agreement
+between you and Element.
+
+To purchase a commercial license please contact our sales team at
+licensing@element.io
@@ -0,0 +1,7 @@
+# @element-hq/element-call-component
+
+Element Call as a React component, rendered in the host application's page
+instead of in an iframe. Experimental.
+
+See [Element Call as a component](https://github.com/element-hq/element-call#element-call-as-a-component-experimental)
+in the Element Call README for usage.
@@ -109,4 +109,12 @@ describe("scopeStylesToRoot", () => {
      ".a .b_abc12:hover { border: 0 }",
    );
  });
+
+  it("leaves an excluded stylesheet as it is", async () => {
+    const css = "body { margin: 0 } .menu { color: red }";
+    const result = await postcss([
+      scopeStylesToRoot({ exclude: [/host\.css$/] }),
+    ]).process(css, { from: "/app/host.css" });
+    expect(result.css).toBe(css);
+  });
 });
@@ -60,12 +60,18 @@ const IS_ROOT = `:where(${ROOT_SELECTOR})`;
 * tokens, the component styles, the fonts — is not in this build at all: the
 * host supplies it, unscoped, along with its copy of Compound.
 */
-export function scopeStylesToRoot(): Plugin {
+interface Options {
+  /** Stylesheets left as they are: a host's own, which it doesn't scope. */
+  exclude?: RegExp[];
+}
+
+export function scopeStylesToRoot({ exclude = [] }: Options = {}): Plugin {
  return {
    postcssPlugin: "element-call-scope-styles-to-root",
    Once(root) {
-      const isModule =
-        root.source?.input.file?.endsWith(".module.css") ?? false;
+      const file = root.source?.input.file ?? "";
+      if (exclude.some((pattern) => pattern.test(file))) return;
+      const isModule = file.endsWith(".module.css");
      root.walkRules((rule) => {
        if (isRelative(rule)) return;
        rule.selector = (isModule ? scopeBare : scopeAll).processSync(
@@ -1,8 +1,8 @@
 {
  "name": "@element-hq/element-call-component",
  "version": "0.0.0",
-  "description": "Element Call as a React component. Consumed straight from the repository as a git dependency (github:element-hq/element-call#<ref>&path:/component): the host's package manager runs `prepare`, which builds `dist/`.",
-  "license": "SEE LICENSE IN ../README.md",
+  "description": "Element Call as a React component.",
+  "license": "AGPL-3.0-only OR LicenseRef-Element-Commercial",
  "repository": {
    "type": "git",
    "url": "https://github.com/element-hq/element-call",
@@ -15,6 +15,8 @@
    }
  },
  "files": [
+    "LICENSE-AGPL-3.0",
+    "LICENSE-COMMERCIAL",
    "dist"
  ],
  "main": "./dist/element-call.js",
@@ -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:b2a5a30afb4f583a7560448b005d8332bee29672f15826e4a995b393058f0291
+    image: ghcr.io/element-hq/element-web:develop@sha256:a79801206c628a912d57fa6f355d5c5ab9c6c40c2d1b6208d4192678fb6e80c7
  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:b2a5a30afb4f583a7560448b005d8332bee29672f15826e4a995b393058f0291
+    image: ghcr.io/element-hq/element-web:develop@sha256:a79801206c628a912d57fa6f355d5c5ab9c6c40c2d1b6208d4192678fb6e80c7
@@ -9,4 +9,4 @@ android_gradle_plugin = { module = "com.android.tools.build:gradle", version.ref

 [plugins]
 android_library = { id = "com.android.library", version.ref = "android_gradle_plugin" }
-maven_publish = { id = "com.vanniktech.maven.publish", version = "0.36.0" }
+maven_publish = { id = "com.vanniktech.maven.publish", version = "0.37.0" }
@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.5-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.6-all.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
@@ -7,13 +7,13 @@
    "features": ["plural_postfix_us", "filter_untranslated"],
    "files": [
      {
-        "pattern": "locales/en/*.json",
+        "pattern": "locales/en/app.json",
        "lang": "inherited"
      },
      {
        "group": "existing",
-        "pattern": "locales/*/*.json",
-        "excludes": ["locales/en/*.json"],
+        "pattern": "locales/*/app.json",
+        "excludes": ["locales/en/app.json"],
        "lang": "${autodetectLang}"
      }
    ]
@@ -22,6 +22,7 @@
  "download": {
    "files": [
      {
+        "conditions": ["equals: ${file}, app.json"],
        "output": "locales/${langLsrDash}/${file}"
      }
    ],
@@ -57,7 +57,6 @@
    "@formatjs/intl-durationformat": "^0.10.0",
    "@formatjs/intl-segmenter": "^11.7.3",
    "@livekit/components-core": "^0.12.0",
-    "@livekit/components-react": "^2.0.0",
    "@livekit/track-processors": "^0.7.1",
    "@mediapipe/tasks-vision": "^0.10.18",
    "@playwright/test": "^1.60.0",
@@ -88,7 +87,7 @@
    "@typescript-eslint/utils": "^8.61.0",
    "@use-gesture/react": "^10.2.11",
    "@vector-im/compound-design-tokens": "^11.0.0",
-    "@vector-im/compound-web": "^10.4.0",
+    "@vector-im/compound-web": "^10.5.0",
    "@vitejs/plugin-react": "^6.0.2",
    "@vitest/browser-playwright": "^4.1.5",
    "@vitest/coverage-v8": "^4.0.18",
@@ -107,7 +106,7 @@
    "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#a9ef09fbf2f1644c8663d0aeaf6a921cd16e7b01",
    "matrix-widget-api": "^1.18.0",
    "node-stdlib-browser": "^1.3.1",
    "normalize.css": "^8.0.1",
@@ -125,25 +125,24 @@ test("leaves the host's own page unstyled", async ({ page }) => {
    timeout: 60_000,
  });

-  // Element Call's stylesheet is written for a page of its own: normalize.css
-  // gives `html` a line height, Compound gives `body` its font and feature
-  // settings, and the design tokens live on `:root`. None of that may reach the
-  // host's document — the harness sets none of these itself, so anything other
-  // than the browser's defaults here came from us.
+  // Element Call's page-wide CSS (normalize.css and the tokens in base.css)
+  // should not reach the host's page. Compound CSS that gets loaded to EW (host)
+  // on the other hand should impact the host. So probe with styles only Element Call sets:
+  // - A fresh <sub> keeps the browser's `vertical-align: sub` unless
+  //   normalize.css leaked; it turns that into `baseline`.
+  // - `--font-scale` is Element Call's own token, so `:root` must not have it.
  const host = await page.evaluate(() => {
-    const html = getComputedStyle(document.documentElement);
-    const body = getComputedStyle(document.body);
+    const sub = document.body.appendChild(document.createElement("sub"));
+    const verticalAlign = getComputedStyle(sub).verticalAlign;
+    sub.remove();
    return {
-      lineHeight: html.lineHeight,
-      fontFeatureSettings: body.fontFeatureSettings,
-      token: html.getPropertyValue("--cpd-color-text-primary"),
+      verticalAlign,
+      token: getComputedStyle(document.documentElement).getPropertyValue(
+        "--font-scale",
+      ),
    };
  });
-  expect(host).toEqual({
-    lineHeight: "normal",
-    fontFeatureSettings: "normal",
-    token: "",
-  });
+  expect(host).toEqual({ verticalAlign: "sub", token: "" });

  // While inside the container, the same rules do apply
  const root = panes.first().locator("[data-element-call-root]");
@@ -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(2);
+  await expect(page.getByTestId("videoTile")).toHaveCount(count);

  // No one should be waiting for media
  await expect(page.getByText("Waiting for media...")).not.toBeVisible({
@@ -31,7 +31,11 @@ interface Transport {
 */
 const shapes = {
  url: { type: "livekit", url: sfuUrl },
-  both: { type: "livekit", url: sfuUrl, livekit_service_url: serviceUrl },
+  "url+legacy": {
+    type: "livekit",
+    url: sfuUrl,
+    livekit_service_url: serviceUrl,
+  },
  legacy: null,
 } satisfies Record<string, Transport | null>;
 type Shape = keyof typeof shapes;
@@ -56,15 +60,15 @@ const cases: {
  {
    // Publishers keep the legacy participant identity that clients predating
    // MSC4195 expect, which only the JWT service assigns.
-    hostShape: "both",
-    guestShape: "both",
+    hostShape: "url+legacy",
+    guestShape: "url+legacy",
    hostFlows: ["service-legacy"],
    guestFlows: ["service-legacy"],
  },
  {
    // The MatrixRTC mode has no bearing on the choice.
-    hostShape: "both",
-    guestShape: "both",
+    hostShape: "url+legacy",
+    guestShape: "url+legacy",
    mode: "2_0",
    hostFlows: ["service-legacy"],
    guestFlows: ["service-legacy"],
@@ -75,6 +79,12 @@ 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) {
@@ -126,47 +136,6 @@ 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,
@@ -191,6 +160,38 @@ 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.
@@ -198,7 +199,7 @@ test("Publisher shows an error when the homeserver lacks MSC4195", async ({
 const delegationCases: { shape: Shape; via: Delegation["via"] }[] = [
  { shape: "url", via: "homeserver" },
  { shape: "legacy", via: "service" },
-  { shape: "both", via: "service" },
+  { shape: "url+legacy", via: "service" },
 ];

 for (const { shape, via } of delegationCases) {
@@ -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: "Dismiss" },
+      { title: "Back up your chats", button: "Not now" },
      { title: "Turn on key storage", button: "Dismiss" },
      { title: "Element does not support this browser", button: "Dismiss" },
    ];
@@ -178,7 +178,11 @@ export class TestHelpers {
        );

        if (toastConfig) {
-          await toast.getByRole("button", { name: toastConfig.button }).click();
+          // 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 });
        } else {
          // Unknown toast. We don't want to act on unknown toasts
          break;
@@ -11,13 +11,12 @@ 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 + livekit_service_url transport and a legacy one",
+  "Call between a url transport and a legacy one",
  async ({ addUser, browserName }) => {
    test.skip(
      browserName === "firefox",
@@ -30,12 +29,10 @@ widgetTest(
      addUser("Pevara", HOST1),
    ]);

-    // The host's homeserver has started advertising a `url` next to its JWT
-    // service; the guest's still advertises the JWT service alone.
+    // Host advertises a url transport, guest still advertises a legacy one
    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
@@ -67,7 +64,7 @@ widgetTest(
    }

    // Element Web used for Playwright does support MSC4195 for widgets.
-    expect(hostFlows).toEqual(new Set(["service-legacy", "service-default"]));
+    expect(hostFlows).toEqual(new Set(["cs-api", "service-default"]));
    expect(guestFlows).toEqual(new Set(["service-legacy", "cs-api"]));
  },
 );
@@ -40,9 +40,6 @@ importers:
      '@livekit/components-core':
        specifier: ^0.12.0
        version: 0.12.15(livekit-client@2.23.0(@types/dom-mediacapture-record@1.0.22))(tslib@2.8.1)
-      '@livekit/components-react':
-        specifier: ^2.0.0
-        version: 2.9.24(livekit-client@2.23.0(@types/dom-mediacapture-record@1.0.22))(react-dom@19.2.8(react@19.2.8))(react@19.2.8)(tslib@2.8.1)
      '@livekit/track-processors':
        specifier: ^0.7.1
        version: 0.7.2(@types/dom-mediacapture-transform@0.1.11)(livekit-client@2.23.0(@types/dom-mediacapture-record@1.0.22))
@@ -66,7 +63,7 @@ importers:
        version: 10.1.2(react-dom@19.2.8(react@19.2.8))(react@19.2.8)
      '@rolldown/plugin-babel':
        specifier: ^0.2.3
-        version: 0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.0)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))
+        version: 0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.8)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))
      '@sentry/react':
        specifier: ^8.0.0
        version: 8.55.2(react@19.2.8)
@@ -134,11 +131,11 @@ importers:
        specifier: ^11.0.0
        version: 11.3.1(@types/react@19.2.18)(react@19.2.8)
      '@vector-im/compound-web':
-        specifier: ^10.4.0
-        version: 10.4.0(@fontsource/inconsolata@5.3.0)(@fontsource/inter@5.3.0)(@types/react-dom@19.2.5(@types/react@19.2.18))(@types/react@19.2.18)(@vector-im/compound-design-tokens@11.3.1(@types/react@19.2.18)(react@19.2.8))(react-dom@19.2.8(react@19.2.8))(react@19.2.8)
+        specifier: ^10.5.0
+        version: 10.5.0(@fontsource/inconsolata@5.3.0)(@fontsource/inter@5.3.0)(@types/react-dom@19.2.5(@types/react@19.2.18))(@types/react@19.2.18)(@vector-im/compound-design-tokens@11.3.1(@types/react@19.2.18)(react@19.2.8))(react-dom@19.2.8(react@19.2.8))(react@19.2.8)
      '@vitejs/plugin-react':
        specifier: ^6.0.2
-        version: 6.1.1(@rolldown/plugin-babel@0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.0)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0)))(babel-plugin-react-compiler@1.0.0)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))
+        version: 6.1.1(@rolldown/plugin-babel@0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.8)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0)))(babel-plugin-react-compiler@1.0.0)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))
      '@vitest/browser-playwright':
        specifier: ^4.1.5
        version: 4.1.11(playwright@1.62.1)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))(vitest@4.1.11)
@@ -191,8 +188,8 @@ importers:
        specifier: ^1.9.1
        version: 1.9.2
      matrix-js-sdk:
-        specifier: github:matrix-org/matrix-js-sdk#3f05dc4d104a3dfc753c5e3549a18c74fab4b076
-        version: https://codeload.github.com/matrix-org/matrix-js-sdk/tar.gz/3f05dc4d104a3dfc753c5e3549a18c74fab4b076
+        specifier: github:matrix-org/matrix-js-sdk#a9ef09fbf2f1644c8663d0aeaf6a921cd16e7b01
+        version: https://codeload.github.com/matrix-org/matrix-js-sdk/tar.gz/a9ef09fbf2f1644c8663d0aeaf6a921cd16e7b01
      matrix-widget-api:
        specifier: ^1.18.0
        version: 1.20.0
@@ -397,8 +394,8 @@ packages:
    resolution: {integrity: sha512-Nq8OhGWiZIZGV6hLHoyAKLLcJihP/xFeBMGJoUrxTX2psI8dCifzLhZISFb+VWS3wFMRDmCGw5R+dOySCqPLhw==}
    engines: {node: '>=6.9.0'}

-  '@babel/runtime@8.0.0':
-    resolution: {integrity: sha512-sL6cvO2IfkSu/iU+zs2S/w01B7A8V7suXSIKEN4hPFFdZoiPGxrj5pAG0lCaqLWiEIrjKzdznIWuaLcxPR53qw==}
+  '@babel/runtime@8.0.8':
+    resolution: {integrity: sha512-dEu8nGlRqjsJsvviUUoSMfcRHpwomCiRlXsc2mPfJ79+ffTpDm+JtfUtTMzUrqCApHQnCsVPD3gT1ZT8RgBRCQ==}

  '@babel/template@7.29.7':
    resolution: {integrity: sha512-puq+Gf35oI24FeN11LkoUQFqv9uwNeWpxXZi/Ji3rRIoKAzKnxRaZ+Gkj0vKS9ZCiTESfng1N9LyOyXvo+m+Gg==}
@@ -408,10 +405,6 @@ packages:
    resolution: {integrity: sha512-B3lYAs2nkKskbgQ1nfy8Ma9ao9Q1rntTAQHrzzyDuj+TSO+X3le6PfWwqDvodsb+OumE10eMFfuMCTQSQ5iuIQ==}
    engines: {node: '>=6.9.0'}

-  '@babel/traverse@7.29.8':
-    resolution: {integrity: sha512-I5z7H3bf/41ktsNVLtpN0wAa336HkqIHQ5BuPLEhTkt1jVSyZpeNKIzTgEWmlxjdg81R0IgUCcaE+Ok3NvrfZg==}
-    engines: {node: '>=6.9.0'}
-
  '@babel/types@7.29.11':
    resolution: {integrity: sha512-WCsemW40Cpc6gouC1SrY6PBaZ+oLRlEVY9XBvZBI7il/HyUrb2nJ505wE1MHEFyDZNnrWDEuy4jL50WVHfTTSQ==}
    engines: {node: '>=6.9.0'}
@@ -1184,19 +1177,6 @@ packages:
      livekit-client: ^2.20.1
      tslib: ^2.6.2

-  '@livekit/components-react@2.9.24':
-    resolution: {integrity: sha512-qw5Oy1EfPg1f/xrKYrFielSrmtxY8BZ9mDt6299G5aikotQIztmldBfTNosrVS7VSNit7qeYfOFSyKaML20W6Q==}
-    engines: {node: '>=18'}
-    peerDependencies:
-      '@livekit/krisp-noise-filter': ^0.2.12 || ^0.3.0 || ^0.4.0
-      livekit-client: ^2.20.1
-      react: '>=18'
-      react-dom: '>=18'
-      tslib: ^2.6.2
-    peerDependenciesMeta:
-      '@livekit/krisp-noise-filter':
-        optional: true
-
  '@livekit/mutex@1.1.1':
    resolution: {integrity: sha512-EsshAucklmpuUAfkABPxJNhzj9v2sG7JuzFDL4ML1oJQSV14sqrpTYnsaOudMAw9yOaW53NU3QQTlUQoRs4czw==}

@@ -3314,8 +3294,8 @@ packages:
      react:
        optional: true

-  '@vector-im/compound-web@10.4.0':
-    resolution: {integrity: sha512-Tt5hsNK7ulhGdRuy9lzSm5C+T8M/4O4kLDFLkaU+Hi1kVWj6tj/5awW+U+GvtpWRh5llbHN2HRCh79+gQhek+A==}
+  '@vector-im/compound-web@10.5.0':
+    resolution: {integrity: sha512-dcxIAKtTKBLKz2Y83mNkXyYx3shtSs80KvdGKN5ryFvo6OnVOhHPEHiQNbaPQ0EDjc6xStjY9+oz2Fh4c+kniQ==}
    peerDependencies:
      '@fontsource/inconsolata': ^5
      '@fontsource/inter': ^5
@@ -3421,11 +3401,6 @@ packages:
    engines: {node: '>=0.4.0'}
    hasBin: true

-  acorn@8.18.0:
-    resolution: {integrity: sha512-lGq+9yr1/GuAWaVYIHRjvvySG5/4VfKIvC8EWxStPdcDh/Ka7FG3twP6v4d5BkravUilhIAsG4Qj83t02LWUPQ==}
-    engines: {node: '>=0.4.0'}
-    hasBin: true
-
  acorn@8.19.0:
    resolution: {integrity: sha512-oJlA3XiRm7Cyk6qFD2Jn8ak9B7jSy0qy00ADO3+8dpT0LSjFihQYv4C02LFCSYJV3Q37xYwwRy5m+IpIiUzqWw==}
    engines: {node: '>=0.4.0'}
@@ -3697,10 +3672,6 @@ packages:
  cliui@6.0.0:
    resolution: {integrity: sha512-t6wbgtoCXvAzst7QgXxJYqPt0usEfbgQdftEPbLL/cvv6HPE5VgvqCuAIDR0NgU52ds6rFwqrgakNLrHEjCbrQ==}

-  clsx@2.1.1:
-    resolution: {integrity: sha512-eYm0QWBtUrBWZWG0d386OGAw16Z995PiOVo2B7bjWSbHedGl5e0ZWaq65kOGgUSNesEIDkB9ISbTg/JK9dhCZA==}
-    engines: {node: '>=6'}
-
  color-convert@2.0.1:
    resolution: {integrity: sha512-RRECPsj7iu/xb5oKYcsFHSppFNnsj/52OVTRKb4zP5onXwVF3zVmmToNcOfGC+CRDpfK/U584fMg38ZHCaElKQ==}
    engines: {node: '>=7.0.0'}
@@ -4536,9 +4507,6 @@ packages:
  jose@6.2.13:
    resolution: {integrity: sha512-7TIg10ZE1x82YediN+lcrPNvGMKge9yFHQD+Qho/b8y2adfugU3AsvvHfxV0fzyFllT6l9xCjf4RWY9g/Z9PJQ==}

-  jose@6.2.9:
-    resolution: {integrity: sha512-XrchZOFZUl/T3vTwRe8XK+cJrGtMF4th1ARnDfwbBXFKThGhlsxEE4Zu03AD/bjJSt/9jT/mxrOCkJWOg77aPA==}
-
  js-tokens@10.0.0:
    resolution: {integrity: sha512-lM/UBzQmfJRo9ABXbPWemivdCW8V2G8FHaHdypQaIy523snUjog0W71ayWXTjiR+ixeMyVHN2XcpnTd/liPg/Q==}

@@ -4694,9 +4662,6 @@ packages:
  lodash-es@4.18.1:
    resolution: {integrity: sha512-J8xewKD/Gk22OZbhpOVSwcs60zhd95ESDwezOFuA3/099925PdHJ7OFHNTGtajL3AlZkykD32HykiMo+BIBI8A==}

-  lodash.debounce@4.0.8:
-    resolution: {integrity: sha512-FT1yDzDYEoYWhnSGnpE/4Kj1fLZkDFyqRb7fNt6FdYOSxlUWAtp42Eh6Wb0rGIv/m9Bgo7x4GhQbm5Ys4SG5ow==}
-
  lodash.merge@4.6.2:
    resolution: {integrity: sha512-0KpjqXRVvrYyCsX1swR/XTK0va6VQkQM6MNo7PqW77ByjAhoARA8EfrP1N4+KlKj8YS0ZUCtRT/YUuhyYDujIQ==}

@@ -4759,9 +4724,9 @@ packages:
  matrix-events-sdk@0.0.1:
    resolution: {integrity: sha512-1QEOsXO+bhyCroIe2/A5OwaxHvBm7EsSQ46DEDn8RBIfQwN5HWBpFvyWWR4QY0KHPPnnJdI99wgRiAl7Ad5qaA==}

-  matrix-js-sdk@https://codeload.github.com/matrix-org/matrix-js-sdk/tar.gz/3f05dc4d104a3dfc753c5e3549a18c74fab4b076:
-    resolution: {gitHosted: true, integrity: sha512-Ly8eS7fNNKDo9KmPvTkE49KvD8iMUmrVWJMNERNuxc8UksMLMG36NLz3fs8HytdwrB7AKPfyVo392VZsxILDIg==, tarball: https://codeload.github.com/matrix-org/matrix-js-sdk/tar.gz/3f05dc4d104a3dfc753c5e3549a18c74fab4b076}
-    version: 44.0.0
+  matrix-js-sdk@https://codeload.github.com/matrix-org/matrix-js-sdk/tar.gz/a9ef09fbf2f1644c8663d0aeaf6a921cd16e7b01:
+    resolution: {gitHosted: true, integrity: sha512-ZAhn/zB44MgrXqUzi9ffSFcmZY3+2nx7bEgfEJR7chYDFyT/XmlmfCJx7Ar4rOTAYZJRVnMxrEwiEHGDapUi0Q==, tarball: https://codeload.github.com/matrix-org/matrix-js-sdk/tar.gz/a9ef09fbf2f1644c8663d0aeaf6a921cd16e7b01}
+    version: 45.0.0
    engines: {node: '>=22.0.0'}

  matrix-widget-api@1.20.0:
@@ -5988,12 +5953,6 @@ packages:
    peerDependencies:
      react: ^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0

-  usehooks-ts@3.1.1:
-    resolution: {integrity: sha512-I4diPp9Cq6ieSUH2wu+fDAVQO43xwtulo+fKEidHUwZPnYImbtkTjzIJYcDcJqxgmX31GVqNFURodvcgHcW0pA==}
-    engines: {node: '>=16.15.0'}
-    peerDependencies:
-      react: ^16.8.0  || ^17 || ^18 || ^19 || ^19.0.0-rc
-
  util-deprecate@1.0.2:
    resolution: {integrity: sha512-EPD5q1uXyFxJpCrLnCc1nHnq3gOa6DZBocAIiI2TaSCA7VCJ1UJDMagCzIkXNsUYfD1daK//LTEQ8xiIbrHtcw==}

@@ -6357,10 +6316,10 @@ snapshots:
      '@babel/helper-compilation-targets': 7.29.7
      '@babel/helper-module-transforms': 7.29.7(@babel/core@7.29.7(supports-color@7.2.0))(supports-color@7.2.0)
      '@babel/helpers': 7.29.7
-      '@babel/parser': 7.29.8
+      '@babel/parser': 7.29.11
      '@babel/template': 7.29.7
-      '@babel/traverse': 7.29.8(supports-color@7.2.0)
-      '@babel/types': 7.29.8
+      '@babel/traverse': 7.29.10(supports-color@7.2.0)
+      '@babel/types': 7.29.11
      '@jridgewell/remapping': 2.3.5
      convert-source-map: 2.0.0
      debug: 4.4.3(supports-color@7.2.0)
@@ -6372,8 +6331,8 @@ snapshots:

  '@babel/generator@7.29.8':
    dependencies:
-      '@babel/parser': 7.29.8
-      '@babel/types': 7.29.8
+      '@babel/parser': 7.29.11
+      '@babel/types': 7.29.11
      '@jridgewell/gen-mapping': 0.3.13
      '@jridgewell/trace-mapping': 0.3.31
      jsesc: 3.1.0
@@ -6390,8 +6349,8 @@ snapshots:

  '@babel/helper-module-imports@7.29.7(supports-color@7.2.0)':
    dependencies:
-      '@babel/traverse': 7.29.8(supports-color@7.2.0)
-      '@babel/types': 7.29.8
+      '@babel/traverse': 7.29.10(supports-color@7.2.0)
+      '@babel/types': 7.29.11
    transitivePeerDependencies:
      - supports-color

@@ -6400,7 +6359,7 @@ snapshots:
      '@babel/core': 7.29.7(supports-color@7.2.0)
      '@babel/helper-module-imports': 7.29.7(supports-color@7.2.0)
      '@babel/helper-validator-identifier': 7.29.7
-      '@babel/traverse': 7.29.8(supports-color@7.2.0)
+      '@babel/traverse': 7.29.10(supports-color@7.2.0)
    transitivePeerDependencies:
      - supports-color

@@ -6417,7 +6376,7 @@ snapshots:
  '@babel/helpers@7.29.7':
    dependencies:
      '@babel/template': 7.29.7
-      '@babel/types': 7.29.8
+      '@babel/types': 7.29.11

  '@babel/parser@7.29.11':
    dependencies:
@@ -6433,13 +6392,13 @@ snapshots:

  '@babel/runtime@7.29.7': {}

-  '@babel/runtime@8.0.0': {}
+  '@babel/runtime@8.0.8': {}

  '@babel/template@7.29.7':
    dependencies:
      '@babel/code-frame': 7.29.7
-      '@babel/parser': 7.29.8
-      '@babel/types': 7.29.8
+      '@babel/parser': 7.29.11
+      '@babel/types': 7.29.11

  '@babel/traverse@7.29.10(supports-color@7.2.0)':
    dependencies:
@@ -6448,19 +6407,7 @@ snapshots:
      '@babel/helper-globals': 7.29.7
      '@babel/parser': 7.29.11
      '@babel/template': 7.29.7
-      '@babel/types': 7.29.8
-      debug: 4.4.3(supports-color@7.2.0)
-    transitivePeerDependencies:
-      - supports-color
-
-  '@babel/traverse@7.29.8(supports-color@7.2.0)':
-    dependencies:
-      '@babel/code-frame': 7.29.7
-      '@babel/generator': 7.29.8
-      '@babel/helper-globals': 7.29.7
-      '@babel/parser': 7.29.8
-      '@babel/template': 7.29.7
-      '@babel/types': 7.29.8
+      '@babel/types': 7.29.11
      debug: 4.4.3(supports-color@7.2.0)
    transitivePeerDependencies:
      - supports-color
@@ -7203,18 +7150,6 @@ snapshots:
      rxjs: 7.8.2
      tslib: 2.8.1

-  '@livekit/components-react@2.9.24(livekit-client@2.23.0(@types/dom-mediacapture-record@1.0.22))(react-dom@19.2.8(react@19.2.8))(react@19.2.8)(tslib@2.8.1)':
-    dependencies:
-      '@livekit/components-core': 0.12.15(livekit-client@2.23.0(@types/dom-mediacapture-record@1.0.22))(tslib@2.8.1)
-      clsx: 2.1.1
-      events: 3.3.0
-      jose: 6.2.9
-      livekit-client: 2.23.0(@types/dom-mediacapture-record@1.0.22)
-      react: 19.2.8
-      react-dom: 19.2.8(react@19.2.8)
-      tslib: 2.8.1
-      usehooks-ts: 3.1.1(react@19.2.8)
-
  '@livekit/mutex@1.1.1': {}

  '@livekit/protocol@1.52.1':
@@ -8167,13 +8102,13 @@ snapshots:
  '@rolldown/binding-win32-x64-msvc@1.2.15':
    optional: true

-  '@rolldown/plugin-babel@0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.0)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))':
+  '@rolldown/plugin-babel@0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.8)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))':
    dependencies:
      '@babel/core': 7.29.7(supports-color@7.2.0)
      picomatch: 4.0.4
      rolldown: 1.2.15
    optionalDependencies:
-      '@babel/runtime': 8.0.0
+      '@babel/runtime': 8.0.8
      vite: 8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0)

  '@rolldown/pluginutils@1.0.1': {}
@@ -8903,7 +8838,7 @@ snapshots:
      '@types/react': 19.2.18
      react: 19.2.8

-  '@vector-im/compound-web@10.4.0(@fontsource/inconsolata@5.3.0)(@fontsource/inter@5.3.0)(@types/react-dom@19.2.5(@types/react@19.2.18))(@types/react@19.2.18)(@vector-im/compound-design-tokens@11.3.1(@types/react@19.2.18)(react@19.2.8))(react-dom@19.2.8(react@19.2.8))(react@19.2.8)':
+  '@vector-im/compound-web@10.5.0(@fontsource/inconsolata@5.3.0)(@fontsource/inter@5.3.0)(@types/react-dom@19.2.5(@types/react@19.2.18))(@types/react@19.2.18)(@vector-im/compound-design-tokens@11.3.1(@types/react@19.2.18)(react@19.2.8))(react-dom@19.2.8(react@19.2.8))(react@19.2.8)':
    dependencies:
      '@floating-ui/react': 0.27.20(react-dom@19.2.8(react@19.2.8))(react@19.2.8)
      '@floating-ui/react-dom': 2.1.9(react-dom@19.2.8(react@19.2.8))(react@19.2.8)
@@ -8925,12 +8860,12 @@ snapshots:
      - '@types/react-dom'
      - react-dom

-  '@vitejs/plugin-react@6.1.1(@rolldown/plugin-babel@0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.0)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0)))(babel-plugin-react-compiler@1.0.0)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))':
+  '@vitejs/plugin-react@6.1.1(@rolldown/plugin-babel@0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.8)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0)))(babel-plugin-react-compiler@1.0.0)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))':
    dependencies:
      '@rolldown/pluginutils': 1.0.1
      vite: 8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0)
    optionalDependencies:
-      '@rolldown/plugin-babel': 0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.0)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))
+      '@rolldown/plugin-babel': 0.2.3(@babel/core@7.29.7(supports-color@7.2.0))(@babel/runtime@8.0.8)(rolldown@1.2.15)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))
      babel-plugin-react-compiler: 1.0.0

  '@vitest/browser-playwright@4.1.11(playwright@1.62.1)(vite@8.2.4(@types/node@24.13.3)(esbuild@0.28.2)(jiti@2.7.0)(sass@1.103.1)(terser@5.46.1)(yaml@2.9.0))(vitest@4.1.11)':
@@ -9055,14 +8990,12 @@ snapshots:

  '@webcontainer/env@1.1.1': {}

-  acorn-jsx@5.3.2(acorn@8.18.0):
+  acorn-jsx@5.3.2(acorn@8.19.0):
    dependencies:
-      acorn: 8.18.0
+      acorn: 8.19.0

  acorn@8.16.0: {}

-  acorn@8.18.0: {}
-
  acorn@8.19.0: {}

  agent-base@6.0.2(supports-color@7.2.0):
@@ -9354,8 +9287,6 @@ snapshots:
      strip-ansi: 6.0.1
      wrap-ansi: 6.2.0

-  clsx@2.1.1: {}
-
  color-convert@2.0.1:
    dependencies:
      color-name: 1.1.4
@@ -9733,8 +9664,8 @@ snapshots:

  espree@9.6.1:
    dependencies:
-      acorn: 8.18.0
-      acorn-jsx: 5.3.2(acorn@8.18.0)
+      acorn: 8.19.0
+      acorn-jsx: 5.3.2(acorn@8.19.0)
      eslint-visitor-keys: 3.4.3

  esprima@4.0.1: {}
@@ -10247,8 +10178,6 @@ snapshots:

  jose@6.2.13: {}

-  jose@6.2.9: {}
-
  js-tokens@10.0.0: {}

  js-tokens@4.0.0: {}
@@ -10409,8 +10338,6 @@ snapshots:

  lodash-es@4.18.1: {}

-  lodash.debounce@4.0.8: {}
-
  lodash.merge@4.6.2: {}

  log-symbols@7.0.1:
@@ -10468,9 +10395,9 @@ snapshots:

  matrix-events-sdk@0.0.1: {}

-  matrix-js-sdk@https://codeload.github.com/matrix-org/matrix-js-sdk/tar.gz/3f05dc4d104a3dfc753c5e3549a18c74fab4b076:
+  matrix-js-sdk@https://codeload.github.com/matrix-org/matrix-js-sdk/tar.gz/a9ef09fbf2f1644c8663d0aeaf6a921cd16e7b01:
    dependencies:
-      '@babel/runtime': 8.0.0
+      '@babel/runtime': 8.0.8
      '@matrix-org/matrix-sdk-crypto-wasm': 18.9.0
      another-json: 0.2.0
      bs58: 6.0.0
@@ -11701,7 +11628,7 @@ snapshots:
  terser@5.46.1:
    dependencies:
      '@jridgewell/source-map': 0.3.11
-      acorn: 8.18.0
+      acorn: 8.19.0
      commander: 2.20.3
      source-map-support: 0.5.21

@@ -11869,11 +11796,6 @@ snapshots:
    dependencies:
      react: 19.2.8

-  usehooks-ts@3.1.1(react@19.2.8):
-    dependencies:
-      lodash.debounce: 4.0.8
-      react: 19.2.8
-
  util-deprecate@1.0.2: {}

  util@0.12.5:
@@ -44,8 +44,9 @@ const TARGETS = [
  {
    config: "vite-component.config.ts",
    what: "the component build",
-    sources: ["src", "component"],
-    excluded: ["component/dev"],
+    // `sdk` too: the build resolves `@element-hq/matrixrtc-sdk` to its source
+    sources: ["src", "component", "sdk"],
+    excluded: ["component/dev", "sdk/dev"],
    mustBeExternal: [
      "react",
      "react-dom",
@@ -126,10 +126,15 @@ probe that decides whether the service that issued the token can take over the
 delayed leave, which picks the delayed leave timings the join uses. The join
 waits for the publisher to hold its token, so that the LiveKit room exists
 before a subscriber, who lacks the permission to create it, asks for a token
-of its own. Until `join()` the tracks exist but their upstream is paused: a host
-can show a preview without anyone hearing it. The upstream flows exactly while the
-membership is `joined`: a sync outage pauses it, and `leave()` pauses it for good
-and sends the leave.
+of its own. The tracks are created once the membership is `joined`, with their
+upstream paused until then. A lobby that wants them earlier captures them with
+`createLocalMedia`, on the browser's devices alone so that any backend fits, and
+hands the media to `join()` as `publish`: the tracks are moved, not shared — they
+leave the lobby's `tracks$`, their objects are finished, and the backend
+publishes the very same device tracks and the processor already running on them,
+so nothing is captured or initialised again at the join. The upstream flows
+exactly while the membership is `joined`: a sync outage pauses it, and `leave()`
+pauses it for good and sends the leave.

 ## Vocabulary

@@ -538,7 +543,7 @@ backend is handed the whole session's view and gives back media:
 type MemberMediaFields = Pick<RTCMember, "tracks$" | "encryptionError$">;

 export interface MediaBackend {
-  readonly transportType: string; // "livekit"
+  readonly transportTypes: readonly string[]; // ["m.livekit", "livekit"]
  /** Authenticate with the transport the client found; the probe for delegation runs here. */
  prepareLocalTransport(
    transport: Transport,
@@ -61,8 +61,8 @@ export {
  createLivekitBackend,
  type LivekitBackendOptions,
 } from "./src/media-backend/livekit/LivekitBackend";
-// For a host that creates LiveKit tracks itself, such as a preview before joining
-export { convertToLivekitProcessor } from "./src/media-backend/livekit/videoProcessor";
+// Tracks for a lobby, captured ahead of the join and handed to it
+export { createLocalMedia } from "./src/LocalMedia";
 // For a developer panel to check a transport before using it
 export {
  getSFUConfig as authenticateWithTransport,
@@ -0,0 +1,237 @@
+/*
+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 { beforeAll, describe, expect, it, vi } from "vitest";
+
+import { createLocalMedia, type GetUserMedia } from "./LocalMedia";
+import { type LocalVideoMediaTrack, type VideoProcessor } from "./media-api";
+
+describe("createLocalMedia", () => {
+  it("opens the microphone and the camera in one request", async () => {
+    const getUserMedia = fakeGetUserMedia();
+    const media = createLocalMedia(getUserMedia);
+
+    const tracks = await media.capture([
+      { source: "microphone", deviceId: "mic" },
+      {
+        source: "camera",
+        capture: { resolution: { width: 640, height: 480 } },
+      },
+    ]);
+
+    expect(getUserMedia).toHaveBeenCalledExactlyOnceWith({
+      audio: { deviceId: "mic" },
+      video: { width: 640, height: 480, frameRate: undefined },
+    });
+    expect(tracks.map((t) => t.source)).toEqual(["microphone", "camera"]);
+    expect(media.tracks$.value).toEqual(tracks);
+    expect(media.requests.map((r) => r.source)).toEqual([
+      "microphone",
+      "camera",
+    ]);
+  });
+
+  it("joins an identical capture still in flight rather than opening the devices again", async () => {
+    const getUserMedia = fakeGetUserMedia();
+    const media = createLocalMedia(getUserMedia);
+    const requests = [{ source: "camera" as const }];
+
+    const [first, second] = await Promise.all([
+      media.capture(requests),
+      media.capture(requests),
+    ]);
+
+    expect(getUserMedia).toHaveBeenCalledOnce();
+    expect(second).toEqual(first);
+    expect(media.tracks$.value).toEqual(first);
+  });
+
+  it("shows the processor's output, initialised once", async () => {
+    const processor = fakeProcessor();
+    const media = createLocalMedia(fakeGetUserMedia());
+    const [camera] = await media.capture([{ source: "camera", processor }]);
+    const element = document.createElement("video");
+
+    camera.attach(element);
+
+    expect(processor.init).toHaveBeenCalledOnce();
+    expect(tracksOn(element)).toEqual([processor.output]);
+  });
+
+  it("hands the tracks over as they are: no second capture, no second init", async () => {
+    const getUserMedia = fakeGetUserMedia();
+    const processor = fakeProcessor();
+    const media = createLocalMedia(getUserMedia);
+    const [microphone, camera] = await media.capture([
+      { source: "microphone" },
+      { source: "camera", processor },
+    ]);
+
+    const taken = media.takeTracks();
+
+    expect(taken.get("microphone")?.track).toBe(trackBehind(microphone));
+    expect(taken.get("camera")).toEqual({
+      track: trackBehind(camera),
+      constraints: {},
+      muted: false,
+      processor: { processor, processedTrack: processor.output },
+    });
+    expect(media.tracks$.value).toEqual([]);
+    expect(getUserMedia).toHaveBeenCalledOnce();
+    expect(processor.init).toHaveBeenCalledOnce();
+    expect(processor.destroy).not.toHaveBeenCalled();
+    media.stop();
+    expect(taken.get("camera")!.track.stop).not.toHaveBeenCalled();
+  });
+
+  it("finishes a handed-over track", async () => {
+    const media = createLocalMedia(fakeGetUserMedia());
+    const [camera] = await media.capture([{ source: "camera" }]);
+    const element = document.createElement("video");
+    camera.attach(element);
+
+    media.takeTracks();
+
+    expect(element.srcObject).toBeNull();
+    await expect(camera.setEnabled(false)).rejects.toThrow("handed over");
+    expect(() => camera.attach(element)).toThrow("handed over");
+  });
+
+  it("mutes by disabling the track and hands the mute over", async () => {
+    const media = createLocalMedia(fakeGetUserMedia());
+    const [microphone] = await media.capture([{ source: "microphone" }]);
+
+    await expect(microphone.setEnabled(false)).resolves.toBe(false);
+
+    expect(microphone.muted$.value).toBe(true);
+    expect(trackBehind(microphone).enabled).toBe(false);
+    expect(media.takeTracks().get("microphone")?.muted).toBe(true);
+  });
+
+  it("switches the device by opening it anew", async () => {
+    const getUserMedia = fakeGetUserMedia();
+    const processor = fakeProcessor();
+    const media = createLocalMedia(getUserMedia);
+    const [camera] = await media.capture([{ source: "camera", processor }]);
+    const first = trackBehind(camera);
+    const element = document.createElement("video");
+    camera.attach(element);
+
+    await camera.setDevice("other");
+
+    expect(getUserMedia).toHaveBeenLastCalledWith({
+      video: { deviceId: "other" },
+    });
+    expect(first.stop).toHaveBeenCalled();
+    expect(processor.restart).toHaveBeenCalledOnce();
+    const [restartedOn, input] = vi.mocked(processor.restart).mock.calls[0];
+    expect(restartedOn).not.toBe(first);
+    expect(input).toBe(vi.mocked(processor.init).mock.calls[0][1]);
+    expect(tracksOn(element)).toEqual([processor.output]);
+    expect(media.takeTracks().get("camera")?.constraints).toEqual({
+      deviceId: "other",
+    });
+  });
+
+  it("reports the facing mode and switches it", async () => {
+    const getUserMedia = fakeGetUserMedia({ facingMode: "user" });
+    const media = createLocalMedia(getUserMedia);
+    const [camera] = (await media.capture([{ source: "camera" }])) as [
+      LocalVideoMediaTrack,
+    ];
+    expect(camera.facingMode$.value).toBe("user");
+
+    await camera.switchFacingMode();
+
+    expect(getUserMedia).toHaveBeenLastCalledWith({
+      video: { facingMode: "environment" },
+    });
+  });
+
+  it("releases one device and stops the rest", async () => {
+    const media = createLocalMedia(fakeGetUserMedia());
+    const [microphone, camera] = await media.capture([
+      { source: "microphone" },
+      { source: "camera" },
+    ]);
+
+    media.release("camera");
+    expect(trackBehind(camera).stop).toHaveBeenCalled();
+    expect(media.tracks$.value).toEqual([microphone]);
+
+    media.stop();
+    expect(trackBehind(microphone).stop).toHaveBeenCalled();
+    expect(media.tracks$.value).toEqual([]);
+  });
+
+  it("refuses a screen share", async () => {
+    const media = createLocalMedia(fakeGetUserMedia());
+    await expect(media.capture([{ source: "screenShare" }])).rejects.toThrow(
+      "screen share",
+    );
+  });
+});
+
+class FakeMediaStream {
+  public constructor(private readonly tracks: MediaStreamTrack[]) {}
+  public getTracks(): MediaStreamTrack[] {
+    return this.tracks;
+  }
+}
+
+beforeAll(() => {
+  globalThis.MediaStream = FakeMediaStream as unknown as typeof MediaStream;
+});
+
+let nextId = 0;
+const tracksById = new Map<string, MediaStreamTrack>();
+
+function fakeTrack(
+  kind: "audio" | "video",
+  settings: MediaTrackSettings = {},
+): MediaStreamTrack {
+  const track = {
+    kind,
+    id: `${kind}-${nextId++}`,
+    enabled: true,
+    stop: vi.fn(),
+    getSettings: () => settings,
+  } as unknown as MediaStreamTrack;
+  tracksById.set(track.id, track);
+  return track;
+}
+
+function fakeGetUserMedia(videoSettings?: MediaTrackSettings): GetUserMedia {
+  return vi.fn(async (constraints: MediaStreamConstraints) => {
+    const tracks: MediaStreamTrack[] = [];
+    if (constraints.audio) tracks.push(fakeTrack("audio"));
+    if (constraints.video) tracks.push(fakeTrack("video", videoSettings));
+    return Promise.resolve(
+      new FakeMediaStream(tracks) as unknown as MediaStream,
+    );
+  });
+}
+
+function fakeProcessor(): VideoProcessor & { output: MediaStreamTrack } {
+  const output = fakeTrack("video");
+  return {
+    name: "blur",
+    output,
+    init: vi.fn(async () => Promise.resolve(output)),
+    restart: vi.fn(async () => Promise.resolve(output)),
+    destroy: vi.fn(async () => Promise.resolve()),
+  };
+}
+
+/** The device's track, which a media track was created on and keeps the id of. */
+function trackBehind(mediaTrack: { id: string }): MediaStreamTrack {
+  return tracksById.get(mediaTrack.id)!;
+}
+
+function tracksOn(element: HTMLMediaElement): MediaStreamTrack[] {
+  return (element.srcObject as unknown as FakeMediaStream).getTracks();
+}
@@ -0,0 +1,335 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { BehaviorSubject, type Observable, of } from "rxjs";
+
+import { MatrixRTCError } from "./errors";
+import {
+  type HandedOverTrack,
+  type LocalAudioMediaTrack,
+  type LocalMedia,
+  type LocalVideoMediaTrack,
+  type MediaSource,
+  type MediaStreamStats,
+  type PublishRequest,
+  type VideoProcessor,
+} from "./media-api";
+import { constant } from "./reactive/Behavior";
+import { inTurn } from "./utils/processorTurns";
+
+type Source = "microphone" | "camera";
+type Request = Extract<PublishRequest, { source: Source }>;
+export type GetUserMedia = (
+  constraints: MediaStreamConstraints,
+) => Promise<MediaStream>;
+
+/**
+ * Local media on the browser's devices alone, for a lobby ahead of a join:
+ * no backend is involved, so whichever backend joins can take the tracks
+ * over. Activity and level are not measured; stats are none.
+ */
+export function createLocalMedia(
+  getUserMedia: GetUserMedia = async (constraints) =>
+    navigator.mediaDevices.getUserMedia(constraints),
+): LocalMedia {
+  const capturedTracks = new Map<Source, CapturedTrack>();
+  const requests = new Map<Source, Request>();
+  const tracks$ = new BehaviorSubject<
+    (LocalAudioMediaTrack | LocalVideoMediaTrack)[]
+  >([]);
+  const publishCapturedTracks = (): void =>
+    tracks$.next(
+      [...capturedTracks.values()].map(({ mediaTrack }) => mediaTrack),
+    );
+
+  // A second identical capture while the first is open joins it: a host that
+  // mounts twice (React's strict mode) must not open the devices twice and
+  // replace the tracks it is already showing
+  const pending = new Map<
+    string,
+    Promise<(LocalAudioMediaTrack | LocalVideoMediaTrack)[]>
+  >();
+  const capture = async (
+    wanted: PublishRequest[],
+  ): Promise<(LocalAudioMediaTrack | LocalVideoMediaTrack)[]> => {
+    const key = JSON.stringify(
+      wanted.map((request) => ({ ...request, processor: undefined })),
+    );
+    const running = pending.get(key);
+    if (running) return running;
+    const started = captureNow(wanted).finally(() => pending.delete(key));
+    pending.set(key, started);
+    return started;
+  };
+
+  const captureNow = async (
+    wanted: PublishRequest[],
+  ): Promise<(LocalAudioMediaTrack | LocalVideoMediaTrack)[]> => {
+    const bySource = new Map<Source, Request>();
+    for (const request of wanted) {
+      if (request.source === "screenShare")
+        throw new MatrixRTCError(
+          "A screen share cannot be captured ahead of a join",
+        );
+      bySource.set(request.source, request);
+    }
+    const constraints: MediaStreamConstraints = {};
+    for (const request of bySource.values())
+      constraints[request.source === "microphone" ? "audio" : "video"] =
+        trackConstraints(request);
+    const stream = await getUserMedia(constraints);
+    const captured: CapturedTrack[] = [];
+    for (const track of stream.getTracks()) {
+      const source: Source = track.kind === "audio" ? "microphone" : "camera";
+      const request = bySource.get(source)!;
+      capturedTracks.get(source)?.stop();
+      const captured_ = new CapturedTrack(
+        source,
+        track,
+        trackConstraints(request),
+        getUserMedia,
+      );
+      capturedTracks.set(source, captured_);
+      requests.set(source, request);
+      if (request.source === "camera" && request.processor)
+        await captured_.setProcessor(request.processor);
+      captured.push(captured_);
+    }
+    publishCapturedTracks();
+    return captured.map(({ mediaTrack }) => mediaTrack);
+  };
+
+  const release = (source: MediaSource): void => {
+    if (source !== "microphone" && source !== "camera") return;
+    capturedTracks.get(source)?.stop();
+    capturedTracks.delete(source);
+    publishCapturedTracks();
+  };
+
+  const stop = (): void => {
+    for (const track of capturedTracks.values()) track.stop();
+    capturedTracks.clear();
+    publishCapturedTracks();
+  };
+
+  const takeTracks = (): Map<Source, HandedOverTrack> => {
+    const taken = new Map<Source, HandedOverTrack>();
+    for (const [source, track] of capturedTracks)
+      taken.set(source, track.handOver());
+    capturedTracks.clear();
+    publishCapturedTracks();
+    return taken;
+  };
+
+  return {
+    get requests(): PublishRequest[] {
+      return [...requests.values()];
+    },
+    tracks$,
+    capture,
+    release,
+    stop,
+    takeTracks,
+  };
+}
+
+/** The constraints a request means to the browser. */
+function trackConstraints(request: Request): MediaTrackConstraints {
+  const device = request.deviceId && { deviceId: request.deviceId };
+  if (request.source === "microphone") return { ...device, ...request.capture };
+  const resolution = request.capture?.resolution;
+  return {
+    ...device,
+    ...(resolution && {
+      width: resolution.width,
+      height: resolution.height,
+      frameRate: resolution.frameRate,
+    }),
+  };
+}
+
+/**
+ * Internal Class that is the owner of the tracks.
+ * Will get stored in `capturedTracks` of `createLocalMedia`.
+ * To the outside this class will return the `LocalMedia` interface.
+ */
+class CapturedTrack {
+  public readonly mediaTrack: LocalAudioMediaTrack | LocalVideoMediaTrack;
+  private readonly muted$ = new BehaviorSubject(false);
+  private readonly facingMode$: BehaviorSubject<
+    "user" | "environment" | undefined
+  >;
+  private readonly elements = new Set<HTMLMediaElement>();
+  private processor: HandedOverTrack["processor"];
+  /** What the processor reads frames from; a processor needs a playing element. */
+  private processorInput?: HTMLVideoElement;
+  private finished = false;
+
+  public constructor(
+    public readonly source: Source,
+    private track: MediaStreamTrack,
+    private constraints: MediaTrackConstraints,
+    private readonly getUserMedia: GetUserMedia,
+  ) {
+    this.facingMode$ = new BehaviorSubject(facingModeOf(track));
+    this.mediaTrack = this.asMediaTrack();
+  }
+
+  public handOver(): HandedOverTrack {
+    const { track, processor } = this;
+    // The device actually in use, so that a backend asked for it again
+    // recognises it rather than restarting the track
+    const { deviceId } = track.getSettings();
+    const constraints = { ...this.constraints, ...(deviceId && { deviceId }) };
+    this.finish();
+    return { track, constraints, muted: this.muted$.value, processor };
+  }
+
+  public stop(): void {
+    const { processor } = this;
+    if (processor)
+      void inTurn(processor.processor, async () =>
+        processor.processor.destroy(),
+      );
+    this.processor?.processedTrack.stop();
+    this.track.stop();
+    this.finish();
+  }
+
+  public async setProcessor(
+    processor: VideoProcessor | undefined,
+  ): Promise<void> {
+    this.live();
+    if (processor === this.processor?.processor) return;
+    const previous = this.processor?.processor;
+    if (previous) await inTurn(previous, async () => previous.destroy());
+    this.processor = processor && {
+      processor,
+      processedTrack: await inTurn(processor, async () =>
+        processor.init(this.track, this.input()),
+      ),
+    };
+    this.show();
+  }
+
+  private input(): HTMLVideoElement {
+    this.processorInput ??= document.createElement("video");
+    this.processorInput.muted = true;
+    this.processorInput.playsInline = true;
+    play(this.processorInput, this.track);
+    return this.processorInput;
+  }
+
+  private finish(): void {
+    this.finished = true;
+    for (const element of this.elements) element.srcObject = null;
+    this.elements.clear();
+  }
+
+  private live(): void {
+    if (this.finished)
+      throw new MatrixRTCError(
+        `The ${this.source} was handed over to a participation`,
+      );
+  }
+
+  private shown(): MediaStreamTrack {
+    return this.processor?.processedTrack ?? this.track;
+  }
+
+  private show(): void {
+    for (const element of this.elements) play(element, this.shown());
+  }
+
+  private async reacquire(constraints: MediaTrackConstraints): Promise<void> {
+    this.live();
+    this.constraints = { ...this.constraints, ...constraints };
+    const stream = await this.getUserMedia({
+      [this.track.kind]: this.constraints,
+    });
+    this.track.stop();
+    this.track = stream.getTracks()[0];
+    this.track.enabled = !this.muted$.value;
+    const { processor } = this;
+    if (processor)
+      processor.processedTrack = await inTurn(processor.processor, async () =>
+        processor.processor.restart(this.track, this.input()),
+      );
+    this.facingMode$.next(facingModeOf(this.track));
+    this.show();
+  }
+
+  private asMediaTrack(): LocalAudioMediaTrack | LocalVideoMediaTrack {
+    const base = {
+      source: this.source,
+      id: this.track.id,
+      muted$: this.muted$,
+      // Nothing leaves the device before the track is published, so there is
+      // nothing unencrypted to report
+      encrypted: true,
+      stats$: (): Observable<MediaStreamStats> => of(undefined),
+      attach: (element: HTMLMediaElement): void => {
+        this.live();
+        this.elements.add(element);
+        play(element, this.shown());
+      },
+      detach: (element: HTMLMediaElement): void => {
+        if (this.elements.delete(element)) element.srcObject = null;
+      },
+      setEnabled: async (enabled: boolean): Promise<boolean> => {
+        this.live();
+        this.track.enabled = enabled;
+        this.muted$.next(!enabled);
+        return Promise.resolve(enabled);
+      },
+      setDevice: async (deviceId: string): Promise<void> => {
+        if (this.track.getSettings().deviceId === deviceId) return;
+        await this.reacquire({ deviceId });
+      },
+    };
+    if (this.source === "microphone")
+      return {
+        ...base,
+        kind: "audio",
+        isActive$: constant(false),
+        audioLevel$: constant(0),
+        setAudioContext: () => {},
+        setVolume: () => {},
+      };
+    return {
+      ...base,
+      kind: "video",
+      facingMode$: this.facingMode$,
+      switchFacingMode: async () => {
+        const facingMode = this.facingMode$.value;
+        if (facingMode === undefined) return;
+        await this.reacquire({
+          facingMode: facingMode === "user" ? "environment" : "user",
+        });
+        return this.track.getSettings().deviceId;
+      },
+      setProcessor: async (processor) => this.setProcessor(processor),
+    };
+  }
+}
+
+function play(element: HTMLMediaElement, track: MediaStreamTrack): void {
+  element.srcObject = new MediaStream([track]);
+  // Autoplay is not a given for a stream set after mount; a test DOM returns
+  // nothing from play
+  const playing = element.play() as Promise<void> | undefined;
+  playing?.catch(() => undefined);
+}
+
+function facingModeOf(
+  track: MediaStreamTrack,
+): "user" | "environment" | undefined {
+  const { facingMode } = track.getSettings();
+  return facingMode === "user" || facingMode === "environment"
+    ? facingMode
+    : undefined;
+}
@@ -164,7 +164,7 @@ function setup(
    context: MediaBackendContext,
  ): MediaBackend => {
    const backend: MediaBackend = {
-      transportType: "livekit",
+      transportTypes: ["m.livekit", "livekit"],
      prepareLocalTransport: async () => fake.prepared.promise,
      delegateDelayedLeave: fake.delegateDelayedLeave,
      local: {
@@ -136,7 +136,8 @@ export function createRTCParticipation(
  // 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"
+    backend.transportTypes.includes("m.livekit") ||
+    backend.transportTypes.includes("livekit")
      ? findRemotePublishLivekitTransport({
          client,
          // A snapshot: if nobody with a usable SFU is here yet, the user has
@@ -152,7 +153,7 @@ export function createRTCParticipation(
  const preparedTransport$ = from(
    discoverLocalTransport(
      client,
-      backend.transportType,
+      backend.transportTypes,
      options,
      transportFromBackends,
      logger,
@@ -20,6 +20,7 @@ import { type Observable } from "rxjs";
 import { type Behavior } from "./reactive/Behavior";
 import {
  type LocalAudioMediaTrack,
+  type LocalMedia,
  type LocalMemberMedia,
  type LocalVideoMediaTrack,
  type MediaSource,
@@ -84,12 +85,15 @@ export interface RTCSlot {

 export interface RTCParticipationOptions {
  /**
-   * Published at the join; `publish` on the participation adds to it from then
-   * on. Kept as an option, rather than only the method, because the LiveKit
-   * backend reads the initial requests to build the room's default capture
-   * options before the first connection exists.
+   * What the local member publishes at the join: requests the SDK captures
+   * itself, or the media a lobby captured ahead of the join, which the
+   * participation takes over (its tracks leave `media.tracks$`) and publishes
+   * in place of capturing. `publish` on the participation adds to either from
+   * then on. Kept as an option, rather than only the method, because the
+   * LiveKit backend reads it to build the room's default capture options
+   * before the first connection exists.
   */
-  publish: PublishRequest[];
+  publish: PublishRequest[] | LocalMedia;
  /**
   * LEGACY
   *
@@ -230,7 +234,7 @@ export interface DataMessage {
 * backend-specific developer panel and for connection diagnostics.
 */
 export interface TransportMetadata {
-  /** `"livekit"` today. */
+  /** `"m.livekit"` or `"livekit"` today. */
  type: string;
  /** Stable key, unique per transport in the slot: the raw transport, serialised with sorted keys. */
  id: string;
@@ -48,7 +48,7 @@ describe("discoverLocalTransport", () => {
    await expect(
      discoverLocalTransport(
        c,
-        "livekit",
+        ["m.livekit", "livekit"],
        { transport: hostTransport },
        fromBackends(),
        logger,
@@ -61,7 +61,7 @@ describe("discoverLocalTransport", () => {
    await expect(
      discoverLocalTransport(
        client([homeserverTransport]),
-        "livekit",
+        ["m.livekit", "livekit"],
        { fallbackTransport: hostTransport },
        fromBackends(),
        logger,
@@ -73,7 +73,7 @@ describe("discoverLocalTransport", () => {
    await expect(
      discoverLocalTransport(
        client([{ type: "not_livekit" }]),
-        "livekit",
+        ["m.livekit", "livekit"],
        { fallbackTransport: hostTransport },
        fromBackends(),
        logger,
@@ -87,7 +87,7 @@ describe("discoverLocalTransport", () => {
    await expect(
      discoverLocalTransport(
        client([homeserverTransport]),
-        "livekit",
+        ["m.livekit", "livekit"],
        {},
        backends,
        logger,
@@ -99,7 +99,7 @@ describe("discoverLocalTransport", () => {
  it("fails naming the homeserver where there is no transport at all", async () => {
    const promise = discoverLocalTransport(
      client([]),
-      "livekit",
+      ["m.livekit", "livekit"],
      {},
      fromBackends(),
      logger,
@@ -15,14 +15,15 @@ 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.
+ * homeserver's first of the most preferred 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.
 */
 export async function discoverLocalTransport(
  client: Pick<MatrixClient, "getDomain" | "_unstable_getRTCTransports">,
-  transportType: string,
+  transportTypes: readonly string[],
  {
    transport: override,
    fallbackTransport,
@@ -34,7 +35,7 @@ export async function discoverLocalTransport(
    override ??
    (await new TransportAutoDiscovery({
      client,
-      transportType,
+      transportTypes,
      fallbackTransport,
      logger,
    }).discoverPreferredTransport()) ??
@@ -61,7 +61,7 @@ describe("TransportAutoDiscovery", () => {

      const discovery = new TransportAutoDiscovery({
        client,
-        transportType: "livekit",
+        transportTypes: ["m.livekit", "livekit"],
        fallbackTransport: configTransport,
        logger: rootLogger,
      });
@@ -75,6 +75,29 @@ describe("TransportAutoDiscovery", () => {
    },
  );

+  it("prefers a transport of an earlier type over one listed before it", async () => {
+    const mLivekit: Transport = {
+      type: "m.livekit",
+      url: "wss://sfu.example.org",
+    };
+    const client = makeClient();
+    client._unstable_getRTCTransports.mockResolvedValue([
+      backendTransport,
+      mLivekit,
+    ]);
+
+    const discovery = new TransportAutoDiscovery({
+      client,
+      transportTypes: ["m.livekit", "livekit"],
+      fallbackTransport: configTransport,
+      logger: rootLogger,
+    });
+
+    await expect(discovery.discoverPreferredTransport()).resolves.toStrictEqual(
+      mLivekit,
+    );
+  });
+
  it("Retries limit_exceeded backend transport", async () => {
    const client = makeClient();
    client._unstable_getRTCTransports
@@ -92,7 +115,7 @@ describe("TransportAutoDiscovery", () => {

    const discovery = new TransportAutoDiscovery({
      client,
-      transportType: "livekit",
+      transportTypes: ["m.livekit", "livekit"],
      fallbackTransport: configTransport,
      logger: rootLogger,
    });
@@ -116,7 +139,7 @@ describe("TransportAutoDiscovery", () => {

      const discovery = new TransportAutoDiscovery({
        client,
-        transportType: "livekit",
+        transportTypes: ["m.livekit", "livekit"],
        fallbackTransport: configTransport,
        logger: rootLogger,
      });
@@ -133,7 +156,7 @@ describe("TransportAutoDiscovery", () => {

    const discovery = new TransportAutoDiscovery({
      client,
-      transportType: "livekit",
+      transportTypes: ["m.livekit", "livekit"],
      fallbackTransport: undefined,
      logger: rootLogger,
    });
@@ -17,27 +17,27 @@ type TransportDiscoveryClient = Pick<

 export interface TransportAutoDiscoveryProps {
  client: TransportDiscoveryClient;
-  /** The transport type the media backend serves. */
-  transportType: string;
-  /** A transport to use when the homeserver advertises none of the type. */
+  /** The transport types we want to discover. Those are the ones, the local media backend supports. most preferred first. */
+  transportTypes: readonly string[];
+  /** A transport to use when the homeserver advertises none of the types. */
  fallbackTransport?: Transport;
  logger: Logger;
 }

 export class TransportAutoDiscovery {
  private readonly client: TransportDiscoveryClient;
-  private readonly transportType: string;
+  private readonly transportTypes: readonly string[];
  private readonly fallbackTransport: Transport | undefined;
  private readonly logger: Logger;

  public constructor({
    client,
-    transportType,
+    transportTypes,
    fallbackTransport,
    logger,
  }: TransportAutoDiscoveryProps) {
    this.client = client;
-    this.transportType = transportType;
+    this.transportTypes = transportTypes;
    this.fallbackTransport = fallbackTransport;
    this.logger = logger.getChild("[TransportAutoDiscovery]");
  }
@@ -64,7 +64,7 @@ export class TransportAutoDiscovery {
  }

  /**
-   * Fetches the first transport of the backend's type from the homeserver.
+   * Fetches the first transport of the backend's most preferred type from the homeserver.
   * This will not throw errors, but instead just log them and return null if the expected config is not found or malformed.
   * @private
   */
@@ -76,17 +76,16 @@ export class TransportAutoDiscovery {
      const transportList = await doNetworkOperationWithRetry(async () =>
        client._unstable_getRTCTransports(),
      );
-      const first = transportList.find(
-        (transport) => transport.type === this.transportType,
-      );
-      if (first) {
-        return first;
-      } else {
-        this.logger.info(
-          `No ${this.transportType} transport found in getRTCTransports end point`,
-          transportList,
+      for (const type of this.transportTypes) {
+        const first = transportList.find(
+          (transport) => transport.type === type,
        );
+        if (first) return first;
      }
+      this.logger.info(
+        `No ${this.transportTypes.join(" or ")} transport found in getRTCTransports end point`,
+        transportList,
+      );
    } catch (ex) {
      this.logger.info(`Failed to use getRTCTransports end point: ${ex}`);
    }
@@ -185,3 +185,45 @@ export interface MemberMedia {
 export interface LocalMemberMedia extends MemberMedia {
  tracks$: Behavior<(LocalAudioMediaTrack | LocalVideoMediaTrack)[] | null>;
 }
+
+/**
+ * Tracks captured ahead of a join, for a lobby: the same local tracks a
+ * participation hands out, on nothing but the browser's devices, so they fit
+ * whichever backend joins. Handed to `join` as `publish`, they are moved once
+ * the participation publishes them: they leave `tracks$`, their objects are
+ * finished (controls reject, elements detached), and the same devices come
+ * back under `localMember$.tracks$` as new objects. `stop` releases only what
+ * was not moved; `capture` works again afterwards.
+ */
+export interface LocalMedia {
+  /** What was captured with, one per source; a join reads its defaults from here. */
+  readonly requests: PublishRequest[];
+  tracks$: Behavior<(LocalAudioMediaTrack | LocalVideoMediaTrack)[]>;
+  /**
+   * Opens the devices, in one permission prompt where the browser asks for
+   * one. Rejects where a device cannot be opened, having opened none of them.
+   * A source captured already is replaced.
+   */
+  capture(
+    requests: PublishRequest[],
+  ): Promise<(LocalAudioMediaTrack | LocalVideoMediaTrack)[]>;
+  /** Closes the device behind a source; nothing where it was not captured. */
+  release(source: MediaSource): void;
+  /** Closes every device still held. */
+  stop(): void;
+  /**
+   * For a media backend, as it starts publishing: moves every track out,
+   * finishing its object here. Not for a host; the participation calls it.
+   */
+  takeTracks(): Map<"microphone" | "camera", HandedOverTrack>;
+}
+
+/** One track as a backend receives it: the device's own track and what runs on it. */
+export interface HandedOverTrack {
+  track: MediaStreamTrack;
+  /** What it was opened with, for a backend that restarts it. */
+  constraints: MediaTrackConstraints;
+  muted: boolean;
+  /** Where a processor runs: it and its output, to adopt rather than initialise again. */
+  processor?: { processor: VideoProcessor; processedTrack: MediaStreamTrack };
+}
@@ -20,6 +20,7 @@ import { type Observable } from "rxjs";
 import { type ResolvedTransport, type RTCMember } from "../api";
 import {
  type LocalAudioMediaTrack,
+  type LocalMedia,
  type LocalMemberMedia,
  type LocalVideoMediaTrack,
  type MediaSource,
@@ -56,8 +57,8 @@ export interface MediaBackendContext {
  /** The slot the session is in, `application#id`; a token is issued for it. */
  slotId: string;
  ownMembershipIdentity: CallMembershipIdentityParts;
-  /** What the local member publishes at the join. */
-  publish: PublishRequest[];
+  /** What the local member publishes at the join: requests, or a lobby's media. */
+  publish: PublishRequest[] | LocalMedia;
  encryptionSystem: EncryptionSystem;
  /**
   * Every media key the session knows: the current ones replayed on
@@ -113,8 +114,11 @@ export interface DataPacket {
 }

 export interface MediaBackend {
-  /** The membership transport type this backend serves: "livekit". */
-  readonly transportType: string;
+  /**
+   * The membership transport types this backend serves, ordered decreasingly
+   * by preference.
+   */
+  readonly transportTypes: readonly string[];

  /**
   * Makes `transport` usable as the one the local member publishes on. The
@@ -16,6 +16,7 @@ import {
  vi,
 } from "vitest";
 import {
+  ConnectionError,
  type LocalParticipant,
  type RemoteParticipant,
  type RemoteTrack,
@@ -41,7 +42,7 @@ import {
 } from "./Connection.ts";
 import { ObservableScope } from "../../reactive/ObservableScope";
 import { type ClientGetTokenParts, type ClientOpenIDParts } from "./auth";
-import { MatrixRTCError } from "../../errors";
+import { LivekitConnectionError, MatrixRTCError } from "../../errors";
 import { testJWTToken } from "../../utils/test-fixtures";
 import { ownMemberMock } from "../../utils/test";
 import { mockRemoteParticipant } from "./test";
@@ -57,6 +58,10 @@ let fakeLocalParticipant: MockedObject<LocalParticipant>;

 const ROOM_ID = "!roomID:example.org";
 const SLOT_ID = "m.call#ROOM";
+const FIREFOX_USER_AGENT =
+  "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:147.0) Gecko/20100101 Firefox/147.0";
+const CHROME_USER_AGENT =
+  "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36";

 const transport: UnstableLivekitTransport = {
  type: "livekit",
@@ -147,6 +152,13 @@ function setupRemoteConnection(): Connection {
  return new Connection(opts, logger);
 }

+function mockUserAgent(userAgent: string): void {
+  const spy = vi
+    .spyOn(navigator, "userAgent", "get")
+    .mockReturnValue(userAgent);
+  onTestFinished(() => spy.mockRestore());
+}
+
 afterEach(() => {
  vi.useRealTimers();
  vi.clearAllMocks();
@@ -375,6 +387,89 @@ describe("Start connection states", () => {
    expect(connection.livekitAlias).toBe("!example_room_id");
  });

+  it("retries a join that failed on the WebSocket in Firefox", async () => {
+    setupTest();
+    mockUserAgent(FIREFOX_USER_AGENT);
+    const connection = setupRemoteConnection();
+    const capturedStates: ConnectionState[] = [];
+    const s = connection.state$.subscribe((value) => {
+      capturedStates.push(value);
+    });
+    onTestFinished(() => s.unsubscribe());
+    const firstJoin = Promise.withResolvers<void>();
+    fakeLivekitRoom.connect.mockReturnValueOnce(firstJoin.promise);
+
+    const started = connection.start();
+    await vi.waitFor(() => expect(fakeLivekitRoom.connect).toHaveBeenCalled());
+    expect(fakeLivekitRoom.connect).toHaveBeenCalledTimes(1);
+    firstJoin.reject(ConnectionError.websocket("WS closed unexpectedly"));
+    await started;
+
+    expect(fakeLivekitRoom.connect).toHaveBeenCalledTimes(2);
+    expect(capturedStates.at(-1)).toEqual({
+      state: "authenticated",
+      livekitState: LivekitConnectionState.Connected,
+    });
+    expect(capturedStates.some((st) => st.state === "error")).toBe(false);
+  });
+
+  it("retries a join in Firefox only once", async () => {
+    setupTest();
+    mockUserAgent(FIREFOX_USER_AGENT);
+    const connection = setupRemoteConnection();
+    fakeLivekitRoom.connect.mockRejectedValue(
+      ConnectionError.websocket("WS closed unexpectedly"),
+    );
+
+    await expect(connection.start()).rejects.toThrow(LivekitConnectionError);
+
+    expect(fakeLivekitRoom.connect).toHaveBeenCalledTimes(2);
+  });
+
+  it("does not retry a join that failed for another reason in Firefox", async () => {
+    setupTest();
+    mockUserAgent(FIREFOX_USER_AGENT);
+    const connection = setupRemoteConnection();
+    fakeLivekitRoom.connect.mockRejectedValueOnce(
+      ConnectionError.serverUnreachable("server was not reachable"),
+    );
+
+    await expect(connection.start()).rejects.toThrow(LivekitConnectionError);
+
+    expect(fakeLivekitRoom.connect).toHaveBeenCalledTimes(1);
+  });
+
+  it("does not retry a join that failed on the WebSocket in other browsers", async () => {
+    setupTest();
+    mockUserAgent(CHROME_USER_AGENT);
+    const connection = setupRemoteConnection();
+    fakeLivekitRoom.connect.mockRejectedValueOnce(
+      ConnectionError.websocket("WS closed unexpectedly"),
+    );
+
+    await expect(connection.start()).rejects.toThrow(LivekitConnectionError);
+
+    expect(fakeLivekitRoom.connect).toHaveBeenCalledTimes(1);
+  });
+
+  it("does not retry a join in Firefox once stopped", async () => {
+    setupTest();
+    mockUserAgent(FIREFOX_USER_AGENT);
+    const connection = setupRemoteConnection();
+    const firstJoin = Promise.withResolvers<void>();
+    fakeLivekitRoom.connect.mockReturnValueOnce(firstJoin.promise);
+    fakeLivekitRoom.disconnect.mockResolvedValue(undefined);
+
+    const started = connection.start();
+    await vi.waitFor(() => expect(fakeLivekitRoom.connect).toHaveBeenCalled());
+    const stopping = connection.stop();
+    firstJoin.reject(ConnectionError.websocket("WS closed unexpectedly"));
+    await stopping;
+
+    await expect(started).resolves.toBeUndefined();
+    expect(fakeLivekitRoom.connect).toHaveBeenCalledTimes(1);
+  });
+
  it("stopping while connecting does not report an error", async () => {
    setupTest();
    const connection = setupRemoteConnection();
@@ -14,6 +14,7 @@ import {
  ConnectionError,
  ConnectionErrorReason,
  type ConnectionState as LivekitConnectionState,
+  getBrowser,
  type Participant,
  type RemoteParticipant,
  type RemoteTrackPublication,
@@ -322,7 +323,7 @@ export class Connection {

      try {
        this.logger.info(`livekitRoom.connect ${url}`);
-        await this.livekitRoom.connect(url, jwt);
+        await this.connectLivekitRoom(url, jwt);
        this.logger.info(`livekitRoom.connect SUCCESS ${url}`);
      } catch (e) {
        this.logger.info(`livekitRoom.connect FAILED ${url}`, e);
@@ -382,6 +383,23 @@ export class Connection {
    }
  }

+  private async connectLivekitRoom(url: string, jwt: string): Promise<void> {
+    try {
+      await this.livekitRoom.connect(url, jwt);
+    } catch (e) {
+      // Behind a proxy, Firefox fails the first WebSocket to a host after trying
+      // it over HTTP/2, so a join that fails on the WebSocket gets a second try.
+      // https://bugzilla.mozilla.org/show_bug.cgi?id=2015411
+      const failedOnFirefoxWebSocket =
+        getBrowser()?.name === "Firefox" &&
+        e instanceof ConnectionError &&
+        e.reason === ConnectionErrorReason.WebSocket;
+      if (this.stopped || !failedOnFirefoxWebSocket) throw e;
+      this.logger.info(`livekitRoom.connect RETRY ${url}`, e);
+      await this.livekitRoom.connect(url, jwt);
+    }
+  }
+
  protected async getSFUConfig(): Promise<SFUConfig> {
    return await getSFUConfig({
      client: this.client,
@@ -24,7 +24,7 @@ import {
 import { type ConnectionFactory } from "./ConnectionFactory.ts";
 import { type Connection } from "./Connection.ts";
 import { ownMemberMock, withTestScheduler } from "../../utils/test";
-import { type Behavior } from "../../reactive/Behavior";
+import { constant, 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 transports with a url", () => {
+  test("Keeps one connection per homeserver for url transports", () => {
    withTestScheduler(({ behavior, expectObservable }) => {
      const urlTransport: TransportLocator = {
        transport: { type: "livekit", url: "wss://sfu.example.org" },
@@ -243,6 +243,94 @@ 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$({
@@ -344,7 +432,7 @@ describe("ConnectionMap", () => {
    data.add({ ...connection } as Connection, [p("b")]);
    expect(warn).toHaveBeenCalledWith(
      expect.stringContaining(
-        'second connection to [null,"https://lk.example.org",null]: existing [a], adding [b]',
+        'second connection to ["openID","https://lk.example.org"]: existing [a], adding [b]',
      ),
    );
    expect(data.getParticipantsForTransport(TRANSPORT_1)).toHaveLength(2);
@@ -18,7 +18,11 @@ import {
  type ObservableScope,
 } from "../../reactive/ObservableScope";
 import { generateItemsWithEpoch } from "../../reactive/observable";
-import { type ConnectionRole, type TransportLocator } from "./auth";
+import {
+  chooseAuthFlow,
+  type ConnectionRole,
+  type TransportLocator,
+} from "./auth";
 import { type Connection } from "./Connection";
 import { type ConnectionFactory } from "./ConnectionFactory";

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

 /**
- * 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.
+ * Converts a {@link TransportLocator} to a key suitable for identifying it in a
+ * map of connections.
 */
 export function keyFor({
  transport,
  serverName,
 }: TransportLocator): TransportKey {
-  const hasUrl = "url" in transport;
+  // 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);
  // Serialize the fields in a consistent order
  return JSON.stringify([
-    hasUrl ? transport.url : null,
-    "livekit_service_url" in transport ? transport.livekit_service_url : null,
-    hasUrl ? serverName : null,
+    flow.kind,
+    // With the CS API flow, we additionally need to distinguish server names
+    ...(flow.kind === "csApi" ? [flow.url, serverName] : [flow.serviceUrl]),
  ]) as TransportKey;
 }

@@ -60,7 +60,10 @@ import {
 import { toMediaConnectionState } from "./connectionState";
 import { createDataChannel$ } from "./DataChannel";
 import { createKeyProvider } from "./KeyProvider";
-import { createLivekitMemberMedia } from "./LivekitMemberMedia";
+import {
+  createLivekitMemberMedia,
+  participantSourcesEqual,
+} from "./LivekitMemberMedia";
 import { createLivekitLocalMedia } from "./LocalMedia";

 export interface LivekitBackendOptions {
@@ -89,7 +92,7 @@ export function createLivekitBackend(
    roomId,
    slotId,
    ownMembershipIdentity,
-    publish,
+    publish: requestsOrMedia,
    encryptionSystem,
    mediaKeys$,
    timings,
@@ -98,6 +101,9 @@ export function createLivekitBackend(
  { client, mediaQuality }: LivekitBackendOptions,
 ): MediaBackend {
  const logger = parentLogger.getChild("[LivekitBackend]");
+  const [publish, media] = Array.isArray(requestsOrMedia)
+    ? [requestsOrMedia, undefined]
+    : [requestsOrMedia.requests, requestsOrMedia];
  const keyProvider = createKeyProvider(encryptionSystem, mediaKeys$, logger);
  const transports = createTransportRegistry(scope);
  const localTransport$ = new BehaviorSubject<TransportLocator | null>(null);
@@ -134,6 +140,7 @@ export function createLivekitBackend(
    connectionMap$,
    localTransport$,
    publish,
+    media,
    audioOutputDeviceId$,
    encryptionSystem,
    logger,
@@ -166,9 +173,8 @@ export function createLivekitBackend(
      );
      canDelegate = Promise.resolve(false);
    } else {
-      // Delegation goes through whichever service authenticates us as a
-      // publisher, so only that service's support counts
-      const flow = chooseAuthFlow(transport, "publisher");
+      // Check for support using the same auth flow that we intend to use later
+      const flow = chooseAuthFlow(transport);
      canDelegate =
        flow.kind === "openID"
          ? supportsDelegation(
@@ -234,22 +240,28 @@ export function createLivekitBackend(
          const connection = connections.getConnectionForTransport(locator);
          // A member advertising both a `url` and a `livekit_service_url` may
          // have authenticated through either flow, under either identity
-          const participant = connections
+          const participants = connections
            .getParticipantsForTransport(locator)
-            .find((p) => backendIdentities.includes(p.identity));
-          return connection && participant
-            ? { participant, room: connection.livekitRoom }
+            .filter((p) => backendIdentities.includes(p.identity));
+          return connection && participants.length
+            ? { participants, room: connection.livekitRoom }
            : null;
        }),
-        distinctUntilChanged(
-          (a, b) => a?.participant === b?.participant && a?.room === b?.room,
-        ),
+        distinctUntilChanged(participantSourcesEqual),
      ),
    );
    source$.pipe(memberScope.bind()).subscribe((source) => {
-      logger.info(
-        `${member.rtcBackendIdentity}: LiveKit participant ${source ? `matched (${source.participant.sid})` : "missing"} on ${locator$.value ? JSON.stringify(locator$.value.transport) : "no transport"}`,
-      );
+      const transportString = locator$.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 ${transportString}`,
+        );
    });
    return createLivekitMemberMedia(memberScope, source$, encryptionSystem);
  };
@@ -271,7 +283,7 @@ export function createLivekitBackend(
  });

  return {
-    transportType: "livekit",
+    transportTypes: ["m.livekit", "livekit"],
    prepareLocalTransport,
    delegateDelayedLeave: delegateLeave,
    local: localMedia_,
@@ -205,7 +205,11 @@ describe("createLivekitMediaTrack", () => {
    await expect(track.setEnabled(false)).resolves.toBe(false);
    expect(setEnabled).toHaveBeenCalledWith("microphone", false);
    await track.setDevice("mic-2");
-    expect(switchActiveDevice).toHaveBeenCalledWith("audioinput", "mic-2");
+    expect(switchActiveDevice).toHaveBeenCalledWith(
+      "audioinput",
+      "mic-2",
+      false,
+    );
  });
 });

@@ -50,7 +50,10 @@ import {
  type VideoMediaTrack,
 } from "../../media-api";
 import { MatrixRTCError } from "../../errors";
-import { convertToLivekitProcessor } from "./videoProcessor";
+import {
+  convertToLivekitProcessor,
+  type LivekitProcessor,
+} from "./videoProcessor";

 export const mediaSources: Record<Track.Source, MediaSource> = {
  [Track.Source.Microphone]: "microphone",
@@ -197,9 +200,19 @@ export function createLocalLivekitMediaTrack(
    setDevice: async (deviceId: string): Promise<void> => {
      if (base.source !== "microphone" && base.source !== "camera")
        throw new MatrixRTCError(`A ${base.source} track has no device`);
+      // LiveKit decides whether to restart by the constraints it keeps, which
+      // a browser that does not echo the device id back (Firefox) leaves
+      // without one; a track already on the device is left alone here
+      const current = publication.track;
+      if (
+        current instanceof LocalTrack &&
+        current.mediaStreamTrack.getSettings().deviceId === deviceId
+      )
+        return;
      await room.switchActiveDevice(
        base.kind === "audio" ? "audioinput" : "videoinput",
        deviceId,
+        false,
      );
    },
  };
@@ -230,9 +243,11 @@ export function createLocalLivekitMediaTrack(
      const track = videoTrack();
      // A processor cannot be built on a track that has already ended
      if (!track || track.mediaStreamTrack.readyState === "ended") return;
+      const current = track.getProcessor() as LivekitProcessor | undefined;
+      if (processor === current?.source) return;
      if (processor)
        await track.setProcessor(convertToLivekitProcessor(processor));
-      else if (track.getProcessor()) await track.stopProcessor();
+      else if (current) await track.stopProcessor();
    },
  };
 }
@@ -25,7 +25,7 @@ describe("createLivekitMemberMedia", () => {
    const { participant, publications, room, emitter } = fakes();
    const media = createLivekitMemberMedia(
      testScope(),
-      constant({ participant, room }),
+      constant({ participants: [participant], room }),
      { kind: E2eeType.NONE },
    );
    expect(media.tracks$.value).toEqual([]);
@@ -52,7 +52,7 @@ describe("createLivekitMemberMedia", () => {
    const { participant, publications, room, emitter } = fakes();
    const media = createLivekitMemberMedia(
      testScope(),
-      constant({ participant, room }),
+      constant({ participants: [participant], room }),
      { kind: E2eeType.NONE },
    );
    emitter.emit(
@@ -16,13 +16,20 @@ import {
  RoomEvent,
  type TrackPublication,
 } from "livekit-client";
-import { EMPTY, filter, map, type Observable, of, switchMap } from "rxjs";
+import {
+  EMPTY,
+  filter,
+  map,
+  type Observable,
+  of,
+  switchMap,
+  combineLatest,
+} 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,
@@ -33,13 +40,27 @@ 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> = {
-  participant: P;
+  participants: 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
@@ -99,21 +120,28 @@ function memberTracks$<P extends Participant, T>(
  ) => T,
 ): Behavior<T[] | null> {
  return scope.behavior(
-    mapScoped(scope, source$, (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),
+    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$.value, room),
+              ),
+            ),
          ),
-        ),
-      ),
-    ).pipe(switchMap((tracks$) => tracks$ ?? of(null))),
+          (...tracks) => tracks.flat(1),
+        );
+      }),
+    ),
  );
 }

@@ -133,7 +161,7 @@ function encryptionErrors$(
            filter(
              (message) =>
                encryptionSystem.kind === E2eeType.SHARED_KEY ||
-                message.includes(source.participant.identity),
+                source.participants.some((p) => message.includes(p.identity)),
            ),
            map((message): EncryptionError | undefined =>
              message.includes("MissingKey")
@@ -10,7 +10,6 @@ import {
  type LocalParticipant,
  type LocalTrackPublication,
  ParticipantEvent,
-  type Room as LivekitRoom,
 } from "livekit-client";
 import { type Logger } from "matrix-js-sdk/lib/logger";
 import {
@@ -28,6 +27,7 @@ import {

 import {
  type LocalAudioMediaTrack,
+  type LocalMedia,
  type LocalVideoMediaTrack,
  type MediaSource,
  type PublishRequest,
@@ -43,7 +43,11 @@ import { type LocalMediaBackend, MediaConnectionState } from "../api";
 import { type TransportLocator } from "./auth";
 import { type Connection } from "./Connection";
 import { type ConnectionMap } from "./ConnectionMap";
-import { createLocalLivekitMemberMedia } from "./LivekitMemberMedia";
+import {
+  createLocalLivekitMemberMedia,
+  type ParticipantSource,
+  participantSourcesEqual,
+} from "./LivekitMemberMedia";
 import { livekitSources } from "./LivekitMediaTrack";
 import { type DesiredMedia, Publisher } from "./Publisher";
 import { toMediaConnectionState } from "./connectionState";
@@ -54,6 +58,8 @@ interface Props {
  /** The transport we publish on; null until the session has found it. */
  localTransport$: Behavior<TransportLocator | null>;
  publish: PublishRequest[];
+  /** Tracks the host captured ahead of the join; the publisher takes them over. */
+  media?: LocalMedia;
  /** Read by the connection factory for the rooms it creates from now on. */
  audioOutputDeviceId$: BehaviorSubject<string | undefined>;
  encryptionSystem: EncryptionSystem;
@@ -76,6 +82,7 @@ export function createLivekitLocalMedia({
  connectionMap$,
  localTransport$,
  publish: initialRequests,
+  media,
  audioOutputDeviceId$,
  encryptionSystem,
  logger: parentLogger,
@@ -116,6 +123,7 @@ export function createLivekitLocalMedia({
      connection.livekitRoom,
      desired,
      logger.getChild(`[Publisher ${JSON.stringify(connection.transport)}]`),
+      media,
    );
    publisher$.next(publisher);
    return Promise.resolve(async (): Promise<void> => {
@@ -217,17 +225,15 @@ function participantAndRoom$(
  scope: ObservableScope,
  participant$: Behavior<LocalParticipant | null>,
  connection$: Behavior<Connection | null>,
-): Behavior<{ participant: LocalParticipant; room: LivekitRoom } | null> {
+): Behavior<ParticipantSource<LocalParticipant>> {
  return scope.behavior(
    combineLatest([participant$, connection$]).pipe(
      map(([participant, connection]) =>
        participant && connection
-          ? { participant, room: connection.livekitRoom }
+          ? { participants: [participant], room: connection.livekitRoom }
          : null,
      ),
-      distinctUntilChanged(
-        (a, b) => a?.participant === b?.participant && a?.room === b?.room,
-      ),
+      distinctUntilChanged(participantSourcesEqual),
    ),
  );
 }
@@ -11,16 +11,32 @@ import {
  LocalParticipant,
  type LocalTrack,
  type LocalTrackPublication,
+  LocalVideoTrack,
  ParticipantEvent,
  type Room as LivekitRoom,
  Track,
+  type TrackPublishOptions,
 } from "livekit-client";
 import { logger } from "matrix-js-sdk/lib/logger";
-import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import {
+  afterEach,
+  beforeAll,
+  beforeEach,
+  describe,
+  expect,
+  it,
+  vi,
+} from "vitest";

-import { type PublishRequest } from "../../media-api";
+import {
+  type HandedOverTrack,
+  type LocalMedia,
+  type PublishRequest,
+  type VideoProcessor,
+} from "../../media-api";
 import { flushPromises } from "../../utils/test";
 import { type DesiredMedia, Publisher } from "./Publisher";
+import { type LivekitProcessor } from "./videoProcessor";

 describe("Publisher", () => {
  describe("setAudioOutputDevice", () => {
@@ -327,6 +343,143 @@ function fakeRoom(
  return { room, switchActiveDevice };
 }

+// A lobby's tracks come as the device's own MediaStreamTracks; LiveKit's
+// track classes are real here so that what is published is what LiveKit will
+// restart and stop as its own
+describe("adopting a lobby's tracks", () => {
+  // LiveKit wraps every track in a MediaStream, which jsdom does not have
+  beforeAll(() => {
+    globalThis.MediaStream = class {
+      public constructor(private readonly tracks: MediaStreamTrack[]) {}
+      public getTracks(): MediaStreamTrack[] {
+        return this.tracks;
+      }
+    } as unknown as typeof MediaStream;
+  });
+
+  function setup(
+    source: "microphone" | "camera",
+    handed: HandedOverTrack,
+  ): { participant: LocalParticipant; publisher: Publisher } {
+    const participant = fakeLocalParticipant(async () => Promise.resolve());
+    const room = {
+      options: {},
+      setE2EEEnabled: () => undefined,
+      localParticipant: participant,
+    } as unknown as LivekitRoom;
+    const desired: DesiredMedia = new Map([
+      [source, { request: { source }, enabled: true }],
+    ]);
+    const media = {
+      takeTracks: () => new Map([[source, handed]]),
+    } as unknown as LocalMedia;
+    const publisher = new Publisher(room, desired, logger, media);
+    return { participant, publisher };
+  }
+
+  it("publishes the lobby's track as its own rather than capturing", async () => {
+    const handed = handedOver("video");
+    const { participant, publisher } = setup("camera", handed);
+
+    publisher.start();
+    await flushPromises();
+
+    expect(participant.createTracks).not.toHaveBeenCalled();
+    const [published, options] = vi.mocked(participant.publishTrack).mock
+      .calls[0] as [LocalVideoTrack, TrackPublishOptions];
+    expect(published).toBeInstanceOf(LocalVideoTrack);
+    expect(published.mediaStreamTrack).toBe(handed.track);
+    expect(published.isUserProvided).toBe(false);
+    expect(options.source).toBe(Track.Source.Camera);
+  });
+
+  it("adopts the processor's output without initialising it again", async () => {
+    const setProcessor = vi
+      .spyOn(LocalVideoTrack.prototype, "setProcessor")
+      .mockResolvedValue(undefined);
+    const processor = {
+      name: "blur",
+      init: vi.fn(),
+      restart: vi.fn(),
+      destroy: vi.fn(),
+    } as unknown as VideoProcessor;
+    const processedTrack = fakeMediaStreamTrack("video");
+    const handed = handedOver("video", {
+      processor: { processor, processedTrack },
+    });
+    const { publisher } = setup("camera", handed);
+
+    publisher.start();
+    await flushPromises();
+
+    const adapter = setProcessor.mock.calls[0][0] as LivekitProcessor;
+    await adapter.init({ kind: Track.Kind.Video, track: handed.track });
+    expect(adapter.processedTrack).toBe(processedTrack);
+    expect(adapter.source).toBe(processor);
+    expect(processor.init).not.toHaveBeenCalled();
+    setProcessor.mockRestore();
+  });
+
+  // A development build mounts, unmounts and mounts the call again: the first
+  // publisher must not have taken the tracks the second one needs
+  it("leaves the lobby's tracks alone until it starts", async () => {
+    const participant = fakeLocalParticipant(async () => Promise.resolve());
+    const room = {
+      options: {},
+      setE2EEEnabled: () => undefined,
+      localParticipant: participant,
+    } as unknown as LivekitRoom;
+    const takeTracks = vi.fn(() => new Map());
+    const media = { takeTracks } as unknown as LocalMedia;
+
+    const publisher = new Publisher(room, new Map(), logger, media);
+    await publisher.destroy();
+
+    expect(takeTracks).not.toHaveBeenCalled();
+  });
+
+  it("joins muted where the lobby muted", async () => {
+    const { participant, publisher } = setup(
+      "microphone",
+      handedOver("audio", { muted: true }),
+    );
+
+    publisher.start();
+    await flushPromises();
+
+    const [published] = vi.mocked(participant.publishTrack).mock.calls[0];
+    expect((published as LocalTrack).isMuted).toBe(true);
+  });
+});
+
+function fakeMediaStreamTrack(kind: "audio" | "video"): MediaStreamTrack {
+  return {
+    kind,
+    id: `${kind}-track`,
+    label: "",
+    enabled: true,
+    readyState: "live",
+    getSettings: () => ({}),
+    getConstraints: () => ({}),
+    getCapabilities: () => ({}),
+    addEventListener: vi.fn(),
+    removeEventListener: vi.fn(),
+    stop: vi.fn(),
+  } as unknown as MediaStreamTrack;
+}
+
+function handedOver(
+  kind: "audio" | "video",
+  extra: Partial<HandedOverTrack> = {},
+): HandedOverTrack {
+  return {
+    track: fakeMediaStreamTrack(kind),
+    constraints: { deviceId: "lobby" },
+    muted: false,
+    ...extra,
+  };
+}
+
 function fakeLocalTrack(source: Track.Source): LocalTrack {
  const state = { isMuted: false, isUpstreamPaused: false };
  const track = {
@@ -6,15 +6,23 @@ Please see LICENSE in the repository root for full details.
 */

 import {
+  LocalAudioTrack,
  type LocalTrackPublication,
+  LocalVideoTrack,
  ParticipantEvent,
  type Room as LivekitRoom,
  type Track,
 } from "livekit-client";
 import { type Logger } from "matrix-js-sdk/lib/logger";

-import { type MediaSource, type PublishRequest } from "../../media-api";
+import {
+  type HandedOverTrack,
+  type LocalMedia,
+  type MediaSource,
+  type PublishRequest,
+} from "../../media-api";
 import { livekitSources, mediaSources } from "./LivekitMediaTrack";
+import { convertToLivekitProcessor } from "./videoProcessor";
 import {
  audioCaptureOptions,
  screenShareCaptureOptions,
@@ -31,6 +39,9 @@ export interface DesiredPublication {

 export type DesiredMedia = Map<MediaSource, DesiredPublication>;

+/** A lobby's tracks, moved out of its media, until each is published. */
+export type HandedOverTracks = ReturnType<LocalMedia["takeTracks"]>;
+
 /**
 * Publishes the local media on one LiveKit room, following the host's
 * requests.
@@ -46,10 +57,19 @@ export class Publisher {
  public started = false;
  private readonly room: LivekitRoom;

+  /** A lobby's tracks, taken over at `start`; each leaves the map as it is published. */
+  private captured: HandedOverTracks = new Map();
+
+  /**
+   * @param media - What a lobby opened ahead of the join, published in place
+   * of capturing. Taken over only at `start`, so that a publisher torn down
+   * before it publishes leaves the tracks to the next one.
+   */
  public constructor(
    room: LivekitRoom,
    private readonly desired: DesiredMedia,
    private readonly logger: Logger,
+    private readonly media?: LocalMedia,
  ) {
    this.room = room;
    room.setE2EEEnabled(room.options.e2ee !== undefined)?.catch((e: Error) => {
@@ -79,33 +99,86 @@ export class Publisher {
  public start(): void {
    if (this.started) return;
    this.started = true;
+    this.captured = this.media?.takeTracks() ?? new Map();
+    // A track muted in the lobby joins muted
+    for (const [source, { muted }] of this.captured) {
+      const wanted = this.desired.get(source);
+      if (wanted && muted) wanted.enabled = false;
+    }
    const requests = [...this.desired.values()]
-      .filter(({ enabled }) => enabled)
+      .filter(
+        ({ request, enabled }) => enabled || this.hasCaptured(request.source),
+      )
      .map(({ request }) => request);
-    const sources = new Set(requests.map((request) => request.source));
+    const toCapture = new Set(
+      requests
+        .map((request) => request.source)
+        .filter((source) => !this.hasCaptured(source)),
+    );
    // Microphone and camera in one call so that the browser asks for
    // permission once; the room defaults carry their options. LiveKit
    // resolves these once the track is published, which may block on the
    // connection; LocalTrackPublished is what tells us a track exists.
-    if (sources.has("microphone") && sources.has("camera"))
+    const captureBoth = toCapture.has("microphone") && toCapture.has("camera");
+    if (captureBoth)
      void this.room.localParticipant.enableCameraAndMicrophone();
    for (const request of requests)
      if (
        request.source === "screenShare" ||
-        !(sources.has("microphone") && sources.has("camera"))
+        this.hasCaptured(request.source) ||
+        !captureBoth
      )
        this.publish(request).catch((e) => {
          this.logger.error(`Failed to publish the ${request.source}`, e);
        });
  }

+  private hasCaptured(source: MediaSource): boolean {
+    return (
+      (source === "microphone" || source === "camera") &&
+      this.captured.has(source)
+    );
+  }
+
+  private takeCaptured(request: PublishRequest): HandedOverTrack | undefined {
+    if (request.source === "screenShare") return undefined;
+    const track = this.captured.get(request.source);
+    this.captured.delete(request.source);
+    return track;
+  }
+
+  /** A lobby's track as if this participant had captured it: LiveKit restarts and stops it as its own. */
+  private async adopt(
+    { track, constraints, muted, processor }: HandedOverTrack,
+    request: PublishRequest,
+  ): Promise<LocalTrackPublication> {
+    const local =
+      track.kind === "audio"
+        ? new LocalAudioTrack(track, constraints, false)
+        : new LocalVideoTrack(track, constraints, false);
+    if (muted) await local.mute();
+    if (processor && local instanceof LocalVideoTrack)
+      await local.setProcessor(
+        convertToLivekitProcessor(
+          processor.processor,
+          processor.processedTrack,
+        ),
+      );
+    return this.room.localParticipant.publishTrack(local, {
+      source: livekitSources[request.source],
+      ...(request.source === "camera" && videoPublishOptions(request.capture)),
+    });
+  }
+
  /** Publishes one request and resolves with its publication once LiveKit has it. */
  public async publish(
    request: PublishRequest,
  ): Promise<LocalTrackPublication | undefined> {
    const participant = this.room.localParticipant;
    let publication: LocalTrackPublication | undefined;
-    if (request.source === "microphone")
+    const captured = this.takeCaptured(request);
+    if (captured) publication = await this.adopt(captured, request);
+    else if (request.source === "microphone")
      publication = await participant.setMicrophoneEnabled(
        true,
        audioCaptureOptions(request),
@@ -13,6 +13,7 @@ import {
 } from "matrix-js-sdk/lib/matrixrtc";
 import { type CallMembershipIdentityParts } from "matrix-js-sdk/lib/matrixrtc/EncryptionManager";

+import { serverNameOfTransport } from "../../utils/serverName";
 import { isCsApiUnavailable } from "./auth";
 import * as csApi from "./auth/csApi";
 import { decodeSFUJWTPayload } from "./auth/types";
@@ -59,7 +60,7 @@ export async function findRemotePublishLivekitTransport({
      if (!isUnstableLivekitTransport(transport) || !("url" in transport))
        continue;
      const { url } = transport;
-      const serverName = membership.getTransportServerName(transport);
+      const serverName = serverNameOfTransport(transport, membership.userId);
      const key = JSON.stringify([url, serverName]);
      if (tried.has(key)) continue;
      tried.add(key);
@@ -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 { ConnectionError, MatrixError } from "matrix-js-sdk";
+import { 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";
@@ -144,26 +144,8 @@ describe("getSFUConfig", () => {
    expect(jwtServiceCalls()).toEqual(["/get_token"]);
  });

-  it("uses CS API when subscribing with url + livekit_service_url transport", async () => {
+  it("uses OpenID 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,
@@ -175,25 +157,7 @@ describe("getSFUConfig", () => {
        livekitAlias: "via default endpoint",
      }),
    );
-    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(client._unstable_getLivekitToken).not.toHaveBeenCalled();
    expect(jwtServiceCalls()).toEqual(["/get_token"]);
  });

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

-  it("does not fall back to OpenID when publishing", async () => {
+  it("does not fall back to OpenID when publishing with url transport", async () => {
    mockJWTService();
    client._unstable_getLivekitToken.mockRejectedValueOnce(unsupportedError);
    await expect(
@@ -255,33 +219,6 @@ 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", () => {
@@ -362,46 +299,21 @@ describe("delegateDelayedLeave", () => {

 describe("chooseAuthFlow", () => {
  it.each([
-    [
-      "url",
-      "publisher",
-      urlTransport,
-      { kind: "csApi", url: urlTransport.url },
-    ],
-    [
-      "url",
-      "subscriber",
-      urlTransport,
-      { kind: "csApi", url: urlTransport.url },
-    ],
+    ["url", 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, role, transport, flow) => {
-      expect(chooseAuthFlow(transport, role)).toEqual(flow);
+    (_shape, transport, flow) => {
+      expect(chooseAuthFlow(transport)).toEqual(flow);
    },
  );
 });
@@ -65,7 +65,10 @@ export interface GetSFUConfigParams {
  logger: Logger;
 }

-/** Authenticates with a transport, through whichever flow suits it and our role. */
+/**
+ * Gets an {@link SFUConfig} appropriate for connecting to a given transport,
+ * using whichever auth flow is appropriate.
+ */
 export async function getSFUConfig({
  client,
  membership,
@@ -76,48 +79,36 @@ export async function getSFUConfig({
  role,
  logger,
 }: GetSFUConfigParams): Promise<SFUConfig> {
-  const viaOpenID = async (serviceUrl: string): Promise<SFUConfig> =>
-    await openID.getSFUConfig({
+  const flow = chooseAuthFlow(transport);
+  if (flow.kind === "openID") {
+    return await openID.getSFUConfig({
      client,
      membership,
-      serviceUrl,
+      serviceUrl: flow.serviceUrl,
      roomId,
      slotId,
      role,
      logger,
    });
-
-  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);
+  } 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;
    }
-    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;
  }
 }

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

 /**
- * 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.
+ * 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.
 */
-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 };
-  }
+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.
  return { kind: "openID", serviceUrl: transport.livekit_service_url };
 }
@@ -47,4 +47,29 @@ describe("convertToLivekitProcessor", () => {
    await adapter.destroy();
    expect(processor.destroy).toHaveBeenCalled();
  });
+
+  // A stopped track tears its processor down without waiting, while the track
+  // replacing it initialises the same one
+  it("runs a destroy and the next init on one processor in turn, across adapters", async () => {
+    const processor = fakeProcessor();
+    let finishDestroy = (): void => {};
+    vi.mocked(processor.destroy).mockImplementation(
+      async () =>
+        new Promise<void>((resolve) => {
+          finishDestroy = resolve;
+        }),
+    );
+    const previous = convertToLivekitProcessor(processor);
+    const next = convertToLivekitProcessor(processor);
+
+    const destroying = previous.destroy();
+    const initialising = next.init(options);
+    await Promise.resolve();
+    expect(processor.init).not.toHaveBeenCalled();
+
+    finishDestroy();
+    await Promise.all([destroying, initialising]);
+    expect(processor.init).toHaveBeenCalledOnce();
+    expect(next.processedTrack).toBe(processed);
+  });
 });
@@ -8,27 +8,42 @@ Please see LICENSE in the repository root for full details.
 import { type Track, type TrackProcessor } from "livekit-client";

 import { type VideoProcessor } from "../../media-api";
+import { inTurn } from "../../utils/processorTurns";
+
+export interface LivekitProcessor extends TrackProcessor<Track.Kind.Video> {
+  /** The processor this adapts, so that setting the same one again is a no-op. */
+  source: VideoProcessor;
+}

 /**
 * A `VideoProcessor` as livekit-client wants it. LiveKit reads the processed
 * track off the processor after `init` and `restart` rather than taking it as
- * their result, so the adapter keeps it there.
+ * their result, so the adapter keeps it there. A processor a lobby already
+ * runs on the track is adopted with its output, `running`, so that the join
+ * does not initialise it again. Every step takes its turn on the processor,
+ * which a stopped track tears down without waiting for the next one's init.
 */
 export function convertToLivekitProcessor(
  processor: VideoProcessor,
-): TrackProcessor<Track.Kind.Video> {
-  const adapter: TrackProcessor<Track.Kind.Video> = {
+  running?: MediaStreamTrack,
+): LivekitProcessor {
+  const adapter: LivekitProcessor = {
    name: processor.name,
-    init: async (opts) => {
-      adapter.processedTrack = await processor.init(opts.track, opts.element);
-    },
-    restart: async (opts) => {
-      adapter.processedTrack = await processor.restart(
-        opts.track,
-        opts.element,
-      );
-    },
-    destroy: async () => processor.destroy(),
+    source: processor,
+    init: async (opts) =>
+      inTurn(processor, async () => {
+        adapter.processedTrack =
+          running ?? (await processor.init(opts.track, opts.element));
+        running = undefined;
+      }),
+    restart: async (opts) =>
+      inTurn(processor, async () => {
+        adapter.processedTrack = await processor.restart(
+          opts.track,
+          opts.element,
+        );
+      }),
+    destroy: async () => inTurn(processor, async () => processor.destroy()),
  };
  return adapter;
 }
@@ -0,0 +1,16 @@
+/*
+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;
+}
@@ -0,0 +1,26 @@
+/*
+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 VideoProcessor } from "../media-api";
+
+const turns = new WeakMap<VideoProcessor, Promise<unknown>>();
+
+/**
+ * One operation at a time on a processor. A host shares one across the
+ * tracks it captures and publishes, and a second init while the first still
+ * loads its model, or a destroy while an init runs, leaves it broken: the
+ * backend's own locking is per track, and a track that is stopped tears its
+ * processor down without waiting.
+ */
+export async function inTurn<T>(
+  processor: VideoProcessor,
+  run: () => Promise<T>,
+): Promise<T> {
+  const turn = (turns.get(processor) ?? Promise.resolve()).then(run, run);
+  turns.set(processor, turn);
+  return turn;
+}
@@ -7,6 +7,7 @@
  padding-top: env(safe-area-inset-top);
  opacity: 1;
  transition: opacity 0.15s;
+  text-align: center;
 }

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

@@ -36,20 +36,15 @@ Please see LICENSE in the repository root for full details.
  }
 }

+/* The width design sets: a long device name wraps. */
 .menu {
-  display: flex;
-  flex-direction: column;
+  inline-size: 296px;
 }

-/* Only the device lists scroll, bounded by the measured call area: the menu is
-   portalled out of the root, so CSS can't size it against the call. */
+/* Its share of the measured call area: the menu is portalled out of the root,
+   so CSS can't size it against the call. */
 .deviceList {
-  overflow-y: auto;
-  min-block-size: 0;
  max-block-size: var(--device-list-max-height);
-  /* Keeps a row reached by keyboard clear of the sticky heading and meter. */
-  scroll-padding-block: var(--device-list-scroll-padding-start, 0)
-    var(--device-list-scroll-padding-end, 0);
 }

 /* Compound's heading rule heads each section; the design adds space below it. */
@@ -62,25 +57,6 @@ Please see LICENSE in the repository root for full details.
  margin-block-start: var(--cpd-space-7x);
 }

-/* Sticky within its own section. Opaque and inset a border width so it doesn't
-   paint over the menu's outline. */
-.sectionHeading {
-  position: sticky;
-  inset-block-start: 0;
-  background: var(--cpd-color-bg-canvas-default);
-  margin-inline: var(--cpd-border-width-1);
-  margin-block-start: var(--cpd-border-width-1);
-}
-
-/* Sticky at the foot of the microphone section; opaque and inset as above. */
-.stickyMeter {
-  position: sticky;
-  inset-block-end: 0;
-  background: var(--cpd-color-bg-canvas-default);
-  margin-inline: var(--cpd-border-width-1);
-  margin-block-end: var(--cpd-border-width-1);
-}
-
 /* Radix focuses whatever the pointer is over, so the browser's ring would
   follow the mouse. Replaced by one shown only for keyboard focus. */
 .menu [role^="menuitem"]:focus,
@@ -65,8 +65,10 @@ const WithACallArea: FC<{ children: ReactNode }> = ({ children }) => {
    <div
      ref={setCallArea}
      style={{
-        // A call's size: anything smaller makes a short device list scroll.
+        // A call's size: anything smaller makes a short device list scroll, and
+        // a narrower one narrows the menu.
        blockSize: 720,
+        inlineSize: 1024,
        display: "flex",
        alignItems: "flex-end",
        justifyContent: "center",
@@ -97,6 +99,10 @@ const meta = {
 export default meta;
 type Story = StoryObj<typeof meta>;

+// By place: Compound's section heading is aria-hidden, as its group carries
+// the name.
+const SECTION_HEADING = "[role='group'] > [aria-hidden]";
+
 export const Default: Story = {
  args: {
    iconsAndLabels: "audio",
@@ -219,9 +225,8 @@ export const SpeakerAndMicrophoneSections: Story = {
    await expect(
      document.body.querySelectorAll("[role='separator']"),
    ).toHaveLength(0);
-    const headings = document.body.querySelectorAll<HTMLElement>(
-      `.${styles.sectionHeading}`,
-    );
+    const headings =
+      document.body.querySelectorAll<HTMLElement>(SECTION_HEADING);
    await expect(headings).toHaveLength(2);
    const frame = menu.getBoundingClientRect();
    for (const heading of headings) {
@@ -256,6 +261,37 @@ export const SpeakerAndMicrophoneSections: Story = {
  },
 };

+/** A long name wraps rather than widening the menu, which design sets. */
+export const LongDeviceNameWraps: Story = {
+  args: {
+    ...SpeakerAndMicrophoneSections.args,
+    outputOptions: [
+      {
+        label: {
+          type: "name",
+          name: "Logitech BRIO 4K Ultra HD Pro Business Webcam Speakers (046d:085e)",
+        },
+        id: "long",
+      },
+      { label: { type: "name", name: "Headset" }, id: "spk2" },
+    ],
+    selectedOutputOption: "long",
+  },
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
+    const body = within(document.body);
+    const long = await body.findByRole("menuitemradio", { name: /Logitech/ });
+    const short = await body.findByRole("menuitemradio", { name: "Headset" });
+
+    const menu = document.body.querySelector("[role='menu']")!;
+    await expect(Math.round(menu.getBoundingClientRect().width)).toBe(296);
+    await expect(long.getBoundingClientRect().height).toBeGreaterThan(
+      short.getBoundingClientRect().height,
+    );
+  },
+};
+
 export const OutputCannotBeChosen: Story = {
  args: {
    ...Default.args,
@@ -402,14 +438,14 @@ export const ManyDevices: Story = {
    await userEvent.click(canvas.getByRole("button", { name: "Microphone" }));
    const menu = within(document.body);

-    // The sticky wrapper rather than the meter: without a fake microphone (as on
+    // The meter's box rather than its level: without a fake microphone (as on
    // WebKit) the meter shows a message instead of a level.
    const list = document.body.querySelector<HTMLElement>(
      `.${styles.deviceList}`,
    )!;
    const sticky = await waitFor(() => {
      const element = document.body.querySelector<HTMLElement>(
-        `.${styles.stickyMeter}`,
+        `.${meterStyles.meter}`,
      );
      if (element === null) throw new Error("the meter has not rendered yet");
      return element;
@@ -436,10 +472,6 @@ export const ManyDevices: Story = {
      .getBoundingClientRect();
    await expect(frame.top).toBeGreaterThanOrEqual(0);
    await expect(frame.bottom).toBeLessThanOrEqual(window.innerHeight + 1);
-
-    // The meter is the menu's one opaque part, so it must stay inside the frame.
-    await expect(pinned.left).toBeGreaterThan(frame.left);
-    await expect(pinned.right).toBeLessThan(frame.right);
  },
 };

@@ -536,7 +568,7 @@ export const KeyboardReachesEveryDevice: Story = {

    const meter = await waitFor(() => {
      const element = document.body.querySelector<HTMLElement>(
-        `.${styles.stickyMeter}`,
+        `.${meterStyles.meter}`,
      );
      if (element === null) throw new Error("the meter has not rendered yet");
      return element;
@@ -545,9 +577,7 @@ export const KeyboardReachesEveryDevice: Story = {
    // Drawn over the list: the sticky headings and the meter.
    const overlays = [
      meter,
-      ...document.body.querySelectorAll<HTMLElement>(
-        `.${styles.sectionHeading}`,
-      ),
+      ...document.body.querySelectorAll<HTMLElement>(SECTION_HEADING),
    ];
    const items = within(document.body).getAllByRole("menuitemradio");

@@ -591,10 +621,7 @@ export const HeadingsStayWhileScrolling: Story = {
      `.${styles.deviceList}`,
    )!;
    const group = await menu.findByRole("group", { name: "Microphone" });
-    // By class: the heading is aria-hidden, and its group carries the name.
-    const heading = group.querySelector<HTMLElement>(
-      `.${styles.sectionHeading}`,
-    )!;
+    const heading = group.querySelector<HTMLElement>(":scope > [aria-hidden]")!;

    // Far enough that the heading is only on screen if it is stuck there.
    list.scrollTop +=
@@ -607,13 +634,6 @@ export const HeadingsStayWhileScrolling: Story = {
    await expect(heading.getBoundingClientRect().bottom).toBeGreaterThan(
      scrollport.top,
    );
-    // Clear of the menu's frame.
-    const frame = document.body
-      .querySelector("[role='menu']")!
-      .getBoundingClientRect();
-    await expect(heading.getBoundingClientRect().left).toBeGreaterThan(
-      frame.left,
-    );
  },
 };

@@ -17,7 +17,8 @@ import {
  Button,
  Menu,
  MenuItem,
-  MenuTitle,
+  MenuScrollArea,
+  MenuScrollSection,
  RadioInput,
  ToggleMenuItem,
 } from "@vector-im/compound-web";
@@ -84,6 +85,9 @@ const LIST_SHARE_OF_CALL = 0.6;
 /** Smallest device list height in px, so a short call still shows more than one device. */
 const MIN_LIST_HEIGHT = 160;

+/** Space kept between the menu and the call area's sides. */
+const MENU_MARGIN = 16;
+
 export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
  enabled,
  busy,
@@ -157,18 +161,18 @@ export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
    return (): void => subscription.unsubscribe();
  }, [menuOpen, rootElement]);

-  // Kept clear at the list's foot, so a row reached by keyboard isn't under
-  // the meter.
-  const [meterHeight, meter] = useMeasuredHeight();
-
-  // Likewise at its head, for the sticky headings.
-  const [headingHeight, heading] = useMeasuredHeight();
-
  useEffect(() => {
    if (menuOpen) devices.requestDeviceNames(); // No-op after the first call
  }, [menuOpen, devices]);

-  const MuteButton = iconsAndLabels === "audio" ? MicButton : VideoButton;
+  const audioMeter = iconsAndLabels === "audio" && (
+    <LiveMicrophoneLevelMeter
+      deviceId={selectedOption}
+      // Only while open, so the microphone isn't held all call.
+      active={menuOpen}
+    />
+  );
+  const MuteButton = audioMeter ? MicButton : VideoButton;
  const button = (
    <MuteButton
      enabled={enabled ?? false}
@@ -179,9 +183,7 @@ export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
        e.stopPropagation();
      }}
      disabled={isBusy || onMuteClick === undefined}
-      data-testid={
-        iconsAndLabels === "audio" ? "incall_mute" : "incall_videomute"
-      }
+      data-testid={audioMeter ? "incall_mute" : "incall_videomute"}
    />
  );

@@ -326,6 +328,8 @@ export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
        open={menuOpen}
        onOpenChange={onOpenChange}
        side="top"
+        collisionBoundary={rootElement}
+        collisionPadding={MENU_MARGIN}
        trigger={
          <Button
            iconOnly
@@ -340,66 +344,41 @@ export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
          />
        }
      >
-        <div
+        <MenuScrollArea
          ref={trackFocusSource}
-          // Keeps the items the menu's own children for assistive tech.
-          role="none"
          className={styles.deviceList}
          data-testid="device-list"
          style={
            {
              "--device-list-max-height":
                listMaxHeight === undefined ? undefined : `${listMaxHeight}px`,
-              "--device-list-scroll-padding-end":
-                meterHeight === undefined ? undefined : `${meterHeight}px`,
-              "--device-list-scroll-padding-start":
-                headingHeight === undefined ? undefined : `${headingHeight}px`,
            } as CSSProperties
          }
        >
-          {iconsAndLabels === "audio" && speakerOptions && (
-            <>
-              {/* A menu may only contain items, separators and groups, so each
-                  heading is a hidden part of a named group. */}
-              <div role="group" aria-label={t("settings.devices.speaker")}>
-                <div aria-hidden className={styles.sectionHeading}>
-                  <MenuTitle title={t("settings.devices.speaker")} />
-                </div>
-                {deviceItems(
-                  "output",
-                  speakerOptions,
-                  selectedSpeaker,
-                  onSelectOutput,
-                  (n) => t("settings.devices.speaker_numbered", { n }),
-                )}
-              </div>
-            </>
-          )}
-          <div role="group" aria-label={optionsButtonLabel}>
-            <div ref={heading} aria-hidden className={styles.sectionHeading}>
-              <MenuTitle title={optionsButtonLabel} />
-            </div>
-            {/* Apart from the heading, so the sticky meter can't ride over it. */}
-            <div role="none">
+          {audioMeter && speakerOptions && (
+            <MenuScrollSection title={t("settings.devices.speaker")}>
              {deviceItems(
-                "input",
-                options,
-                selectedOption,
-                onSelect,
-                numberedLabel,
+                "output",
+                speakerOptions,
+                selectedSpeaker,
+                onSelectOutput,
+                (n) => t("settings.devices.speaker_numbered", { n }),
              )}
-              {iconsAndLabels === "audio" && (
-                <LiveMicrophoneLevelMeter
-                  ref={meter}
-                  deviceId={selectedOption}
-                  // Only while open, so the microphone isn't held all call.
-                  active={menuOpen}
-                  className={styles.stickyMeter}
-                />
-              )}
-            </div>
-          </div>
-        </div>
+            </MenuScrollSection>
+          )}
+          <MenuScrollSection
+            title={optionsButtonLabel}
+            stickyBottomItem={audioMeter}
+          >
+            {deviceItems(
+              "input",
+              options,
+              selectedOption,
+              onSelect,
+              numberedLabel,
+            )}
+          </MenuScrollSection>
+        </MenuScrollArea>
        {toggles.length > 0 && <hr />}
        {toggles.map((toggle) => (
          <ToggleMenuItem
@@ -416,25 +395,3 @@ export const MediaMuteAndSwitchButton: FC<MediaMuteAndSwitchButtonProps> = ({
    </div>
  );
 };
-
-/** Follows an element's height. */
-function useMeasuredHeight(): [
-  number | undefined,
-  (element: HTMLElement | null) => (() => void) | undefined,
-] {
-  const [height, setHeight] = useState<number>();
-  const ref = useCallback(
-    (element: HTMLElement | null): (() => void) | undefined => {
-      if (element === null) return;
-      const subscription = observeElementSize$(element)
-        .pipe(
-          map((size) => size.height),
-          distinctUntilChanged(),
-        )
-        .subscribe(setHeight);
-      return (): void => subscription.unsubscribe();
-    },
-    [],
-  );
-  return [height, ref];
-}
@@ -16,10 +16,10 @@ Please see LICENSE in the repository root for full details.
  align-items: center;
  gap: var(--cpd-space-3x);
  padding-block: var(--cpd-space-2x);
-  /* Centres the icon on the radio column: less the row's inset border and half
-     the icon's extra width. Checked in the MeterAlignsWithTheDeviceRows story. */
+  /* Centres the icon on the radio column: less half the icon's extra width.
+     Checked in the MeterAlignsWithTheDeviceRows story. */
  padding-inline-start: calc(
-    var(--cpd-space-4x) - var(--cpd-border-width-1) -
+    var(--cpd-space-4x) -
      (var(--meter-icon-size) - var(--device-control-size)) / 2
  );
  padding-inline-end: calc(var(--cpd-space-4x) * 2 + var(--cpd-space-2x));
@@ -5,17 +5,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */

-import {
-  useCallback,
-  useLayoutEffect,
-  useRef,
-  useState,
-  type FC,
-  type Ref,
-} from "react";
+import { useCallback, useLayoutEffect, useRef, useState, type FC } from "react";
 import { Text } from "@vector-im/compound-web";
 import { MicOnIcon } from "@vector-im/compound-design-tokens/assets/web/icons";
-import classNames from "classnames";
 import { useTranslation } from "react-i18next";

 import { distinctUntilChanged, map } from "rxjs";
@@ -30,8 +22,6 @@ export interface LiveMicrophoneLevelMeterProps {
  deviceId: string | undefined;
  /** Whether to hold a capture at all. */
  active: boolean;
-  className?: string;
-  ref?: Ref<HTMLDivElement>;
 }

 /**
@@ -41,24 +31,18 @@ export interface LiveMicrophoneLevelMeterProps {
 export const LiveMicrophoneLevelMeter: FC<LiveMicrophoneLevelMeterProps> = ({
  deviceId,
  active,
-  className,
-  ref,
 }) => {
  const state = useMicrophoneLevel(deviceId, active);
-  return <MicrophoneLevelMeter state={state} className={className} ref={ref} />;
+  return <MicrophoneLevelMeter state={state} />;
 };

 export interface MicrophoneLevelMeterProps {
  state: MicrophoneState;
-  className?: string;
-  ref?: Ref<HTMLDivElement>;
 }

 /** The input level of a microphone, or why there is none. */
 export const MicrophoneLevelMeter: FC<MicrophoneLevelMeterProps> = ({
  state,
-  className,
-  ref,
 }) => {
  const { t } = useTranslation();
  // Bars keep one size, so their count follows the width. Starts full so the
@@ -104,7 +88,7 @@ export const MicrophoneLevelMeter: FC<MicrophoneLevelMeterProps> = ({
  }, [state, barCount, t]);

  return (
-    <div ref={ref} className={classNames(styles.meter, className)}>
+    <div className={styles.meter}>
      <MicOnIcon className={styles.icon} aria-hidden />
      {state.type !== "level" ? (
        <Text size="sm" className={styles.message}>
@@ -5,11 +5,24 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */

-import { afterEach, describe, expect, test } from "vitest";
+import { afterEach, describe, expect, test, vi } from "vitest";
+import { act, renderHook } from "@testing-library/react";
+import { E2eeType } from "@element-hq/matrixrtc-sdk";

-import { getKeyForRoom, saveKeyForRoom } from "./sharedKeyManagement";
+import {
+  getKeyForRoom,
+  saveKeyForRoom,
+  useRoomEncryptionSystem,
+} from "./sharedKeyManagement";
+
+vi.mock("../ClientContext", () => {
+  const room = { hasEncryptionStateEvent: (): boolean => false };
+  const client = { getRoom: (): typeof room => room };
+  return { useClient: (): { client: typeof client } => ({ client }) };
+});

 const roomId = "!room:example.org";
+const otherRoomId = "!other:example.org";

 describe("getKeyForRoom", () => {
  afterEach(() => {
@@ -33,4 +46,58 @@ describe("getKeyForRoom", () => {
  test("has no key to offer for a room it has never seen", () => {
    expect(getKeyForRoom(roomId)).toBeNull();
  });
+
+  test("prefers the stored key when the parameters are for another room", () => {
+    saveKeyForRoom(roomId, "stored");
+    window.location.hash = `#?roomId=${encodeURIComponent(otherRoomId)}&password=other-room`;
+
+    expect(getKeyForRoom(roomId)).toBe("stored");
+  });
+
+  test("ignores the password in the parameters for another room", () => {
+    window.location.hash = `#?roomId=${encodeURIComponent(otherRoomId)}&password=other-room`;
+
+    expect(getKeyForRoom(roomId)).toBeNull();
+  });
+});
+
+describe("useRoomEncryptionSystem", () => {
+  afterEach(() => {
+    window.location.hash = "#";
+    localStorage.clear();
+  });
+
+  test("picks up a key saved for the room after it rendered", () => {
+    const { result } = renderHook(() => useRoomEncryptionSystem(roomId));
+    expect(result.current).toEqual({ kind: E2eeType.NONE });
+
+    act(() => saveKeyForRoom(roomId, "stored"));
+
+    expect(result.current).toEqual({
+      kind: E2eeType.SHARED_KEY,
+      secret: "stored",
+    });
+  });
+
+  test("stores a key from the parameters under the room's key only", () => {
+    window.location.hash = `#?roomId=${encodeURIComponent(roomId)}&password=from-the-link`;
+
+    renderHook(() => useRoomEncryptionSystem(roomId));
+
+    expect(Object.keys(localStorage)).toEqual([`room-shared-key-${roomId}`]);
+    expect(getKeyForRoom(roomId)).toBe("from-the-link");
+  });
+
+  test("keeps the stored key when the parameters are for another room", () => {
+    saveKeyForRoom(roomId, "stored");
+    window.location.hash = `#?roomId=${encodeURIComponent(otherRoomId)}&password=other-room`;
+
+    const { result } = renderHook(() => useRoomEncryptionSystem(roomId));
+
+    expect(result.current).toEqual({
+      kind: E2eeType.SHARED_KEY,
+      secret: "stored",
+    });
+    expect(localStorage.getItem(`room-shared-key-${roomId}`)).toBe("stored");
+  });
 });
@@ -59,22 +59,27 @@ const useRoomSharedKey = (

 /**
 * The shared key for a room, preferring one supplied in the parameters Element
- * Call was started with over whatever is in local storage.
+ * Call was started with over whatever is in local storage. If the parameters
+ * are for another room, only the stored key is used, because the password in
+ * the parameters belongs to that other room.
 */
 function keyForRoom(
  roomId: string,
  paramsRoomId: string | null,
  password: string | null,
 ): string | null {
-  if (roomId !== paramsRoomId)
+  const storedKey = localStorage.getItem(
+    getRoomSharedKeyLocalStorageKey(roomId),
+  );
+  if (roomId !== paramsRoomId) {
    logger.warn(
      "requested key for a roomId which is not the current call room id (from the URL)",
      roomId,
      paramsRoomId,
    );
-  return (
-    password ?? localStorage.getItem(getRoomSharedKeyLocalStorageKey(roomId))
-  );
+    return storedKey;
+  }
+  return password ?? storedKey;
 }

 export function getKeyForRoom(roomId: string): string | null {
@@ -89,16 +94,12 @@ export function useRoomEncryptionSystem(roomId: string): EncryptionSystem {
  const { roomId: paramsRoomId, password } = useUrlParams();

  const [storedPassword] = useRoomSharedKey(
-    // TODO: this passes an already-prefixed key where a room ID is expected, so
-    // the local storage key ends up prefixed twice and never matches what
-    // saveKeyForRoom writes. Preserved as-is here to keep this commit a pure
-    // refactor; the reactive read is effectively dead until it is fixed.
-    getRoomSharedKeyLocalStorageKey(roomId),
+    roomId,
    keyForRoom(roomId, paramsRoomId, password) ?? undefined,
  );

  const room = client?.getRoom(roomId);
-  const e2eeSystem = <EncryptionSystem>useMemo(() => {
+  const e2eeSystem = useMemo<EncryptionSystem>(() => {
    if (!room) return { kind: E2eeType.NONE };
    if (storedPassword)
      return {
@@ -72,6 +72,7 @@ import { useRootElement } from "../RootElementContext.ts";
 import { useHostBridge } from "../HostBridge.ts";
 import { useMuteStates } from "../state/useMuteStates.ts";
 import { useLeaveToHome } from "../LeaveToHomeContext.ts";
+import { useLocalMedia } from "../useLocalMedia.ts";

 /**
 * If there already are this many participants in the call, we automatically mute
@@ -273,6 +274,8 @@ const LoadedCallView: FC<LoadedProps> = ({

  const mediaDevices = useMediaDevices();
  const latestMuteStates = useLatest(muteStates);
+  // Opened by the lobby, published by the call: one capture for both
+  const media = useLocalMedia();

  const enterRTCSessionOrError = useCallback(
    async (rtcSession: MatrixRTCSession): Promise<void> => {
@@ -500,6 +503,7 @@ const LoadedCallView: FC<LoadedProps> = ({
      <LobbyView
        client={client}
        matrixInfo={matrixInfo}
+        media={media}
        muteStates={muteStates}
        onEnter={() => setJoined(true)}
        confineToRoom={confineToRoom}
@@ -529,6 +533,7 @@ const LoadedCallView: FC<LoadedProps> = ({
          rtcSession={rtcSession as MatrixRTCSession}
          matrixRoom={room}
          onLeft={onLeft}
+          media={media}
          muteStates={muteStates}
          e2eeSystem={e2eeSystem}
          //otelGroupCallMembership={otelGroupCallMembership}
@@ -227,6 +227,18 @@ describe("InCallView", () => {
  });
 });

+// Media that opened nothing: the join captures as it always did
+function fakeLocalMedia(): MatrixRTCSdk.LocalMedia {
+  return {
+    requests: [],
+    tracks$: constant([]),
+    capture: vi.fn(async () => Promise.resolve([])),
+    release: vi.fn(),
+    stop: vi.fn(),
+    takeTracks: () => new Map(),
+  };
+}
+
 describe("ActiveCall", () => {
  it("creates the view models and renders the call", async () => {
    const mediaDevices = mockMediaDevices({});
@@ -244,6 +256,7 @@ describe("ActiveCall", () => {
                matrixInfo={matrixInfo}
                onShareClick={null}
                e2eeSystem={{ kind: E2eeType.NONE }}
+                media={fakeLocalMedia()}
                onLeft={(): void => {}}
              />
            </TooltipProvider>
@@ -292,6 +305,7 @@ describe("ActiveCall", () => {
                    matrixInfo={matrixInfo}
                    onShareClick={null}
                    e2eeSystem={{ kind: E2eeType.NONE }}
+                    media={fakeLocalMedia()}
                    onLeft={(): void => {}}
                  />
                </TooltipProvider>
@@ -50,6 +50,7 @@ import { Grid, type TileProps } from "../grid/Grid";
 import { SpotlightTile } from "../tile/SpotlightTile";
 import {
  type EncryptionSystem,
+  type LocalMedia,
  type MatrixRTCMode,
 } from "@element-hq/matrixrtc-sdk";
 import { E2eeType } from "../e2ee/e2eeType";
@@ -133,6 +134,8 @@ export interface ActiveCallProps extends Omit<
  "vm" | "footerVm" | "developerSettingsVm"
 > {
  e2eeSystem: EncryptionSystem;
+  /** The tracks the lobby opened, for the join to publish. */
+  media: LocalMedia;
  // TODO refactor those reasons into an enum
  onLeft: (
    reason: "user" | "timeout" | "decline" | "allOthersLeft" | "error",
@@ -170,7 +173,11 @@ export const ActiveCall: FC<ActiveCallProps> = (props) => {
    );
    const rtcParticipation = slot.join({
      ...rtcParticipationOptions(urlParams),
-      publish: initialPublishRequests(props.muteStates, mediaDevices, capture),
+      // Without a lobby nothing was captured and the join captures itself
+      publish:
+        props.media.requests.length > 0
+          ? props.media
+          : initialPublishRequests(props.muteStates, mediaDevices, capture),
    });

    const vm = createCallViewModel$(
@@ -216,6 +223,7 @@ export const ActiveCall: FC<ActiveCallProps> = (props) => {
    mediaDevices,
    trackProcessorState$,
    props.client,
+    props.media,
    rootElement,
  ]);

@@ -10,6 +10,11 @@ import { render, screen } from "@testing-library/react";
 import userEvent from "@testing-library/user-event";
 import { TooltipProvider } from "@vector-im/compound-web";
 import { type MatrixClient, type RoomSummary } from "matrix-js-sdk";
+import {
+  type Behavior,
+  constant,
+  type LocalMedia,
+} from "@element-hq/matrixrtc-sdk";

 import { KnockLobbyView } from "./KnockLobbyView";
 import { LeaveToHomeProvider } from "../LeaveToHomeContext";
@@ -17,16 +22,29 @@ import { MediaDevicesContext } from "../MediaDevicesContext";
 import { type ProcessorState } from "../tracks/TrackProcessorContext";
 import { mockMediaDevices } from "../utils/test";

-vi.mock("@livekit/components-react", () => ({
-  usePreviewTracks: (): unknown[] => [],
+// One instance each: the lobby keys effects on them
+const stable = vi.hoisted(() => ({
+  processorState$: undefined as unknown,
+  media: undefined as unknown,
 }));
-
 vi.mock("../tracks/TrackProcessorContext", () => ({
-  useTrackProcessor: (): ProcessorState => ({
-    supported: false,
-    processor: undefined,
-  }),
-  useTrackProcessorSync: (): void => {},
+  useTrackProcessorState$: (): Behavior<ProcessorState> =>
+    (stable.processorState$ ??= constant({
+      supported: false,
+      processor: undefined,
+    })) as Behavior<ProcessorState>,
+}));
+// Media that opens no device: the view is what is under test
+vi.mock("../useLocalMedia", () => ({
+  useLocalMedia: (): LocalMedia =>
+    (stable.media ??= {
+      requests: [],
+      tracks$: constant([]),
+      capture: vi.fn(async () => Promise.resolve([])),
+      release: vi.fn(),
+      stop: vi.fn(),
+      takeTracks: () => new Map(),
+    }) as LocalMedia,
 }));

 vi.mock("react-use-measure", () => ({
@@ -13,6 +13,7 @@ import { CheckIcon } from "@vector-im/compound-design-tokens/assets/web/icons";
 import { LobbyView } from "./LobbyView";
 import { E2eeType } from "../e2ee/e2eeType";
 import { useMuteStates } from "../state/useMuteStates";
+import { useLocalMedia } from "../useLocalMedia";

 interface Props {
  client: MatrixClient;
@@ -49,6 +50,7 @@ export const KnockLobbyView: FC<Props> = ({
 }): ReactNode => {
  const { t } = useTranslation();
  const muteStates = useMuteStates();
+  const media = useLocalMedia();

  if (muteStates === null) return null;

@@ -85,6 +87,7 @@ export const KnockLobbyView: FC<Props> = ({
      confineToRoom={confineToRoom}
      hideHeader={hideHeader}
      participantCount={null}
+      media={media}
      muteStates={muteStates}
      onShareClick={null}
    />
@@ -12,6 +12,11 @@ import { of } from "rxjs";
 import { LeaveToHomeProvider } from "../LeaveToHomeContext";
 import { TooltipProvider } from "@vector-im/compound-web";
 import { type MatrixClient } from "matrix-js-sdk";
+import {
+  type Behavior,
+  constant,
+  type LocalMedia,
+} from "@element-hq/matrixrtc-sdk";
 import { axe } from "vitest-axe";
 import {
  ArrowLeftIcon,
@@ -37,17 +42,27 @@ import { AppBar } from "../AppBar";
 // Somewhere to go home to, so that the lobby offers the way back
 const leaveToHome = vi.fn();

-vi.mock("@livekit/components-react", () => ({
-  usePreviewTracks: (): unknown[] => [],
+// One instance: the view keys an effect on it
+const processorState$ = vi.hoisted(() => ({ current: undefined as unknown }));
+vi.mock("../tracks/TrackProcessorContext", () => ({
+  useTrackProcessorState$: (): Behavior<ProcessorState> =>
+    (processorState$.current ??= constant({
+      supported: false,
+      processor: undefined,
+    })) as Behavior<ProcessorState>,
 }));

-vi.mock("../tracks/TrackProcessorContext", () => ({
-  useTrackProcessor: (): ProcessorState => ({
-    supported: false,
-    processor: undefined,
-  }),
-  useTrackProcessorSync: (): void => {},
-}));
+// Media that opens no device: the view is what is under test
+function fakeLocalMedia(): LocalMedia {
+  return {
+    requests: [],
+    tracks$: constant([]),
+    capture: vi.fn(async () => Promise.resolve([])),
+    release: vi.fn(),
+    stop: vi.fn(),
+    takeTracks: () => new Map(),
+  };
+}

 vi.mock("react-use-measure", () => ({
  default: (): [() => void, object] => [(): void => {}, {}],
@@ -95,6 +110,7 @@ function renderLobbyView(
    <LobbyView
      client={mockClient}
      matrixInfo={matrixInfo}
+      media={fakeLocalMedia()}
      muteStates={muteStates}
      onEnter={() => {}}
      confineToRoom={false}
@@ -5,26 +5,18 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */

-import {
-  type FC,
-  useCallback,
-  useMemo,
-  useState,
-  type JSX,
-  useEffect,
-} from "react";
+import { type FC, useCallback, useState, type JSX, useEffect } from "react";
 import { useTranslation } from "react-i18next";
 import { type MatrixClient } from "matrix-js-sdk";
 import { Button } from "@vector-im/compound-web";
 import classNames from "classnames";
 import { logger } from "matrix-js-sdk/lib/logger";
-import { usePreviewTracks } from "@livekit/components-react";
 import {
-  type CreateLocalTracksOptions,
-  type LocalVideoTrack,
-  Track,
-} from "livekit-client";
-import { convertToLivekitProcessor } from "@element-hq/matrixrtc-sdk";
+  constant,
+  type LocalMedia,
+  type LocalVideoMediaTrack,
+} from "@element-hq/matrixrtc-sdk";
+import { map } from "rxjs";

 import inCallStyles from "./InCallView.module.css";
 import styles from "./LobbyView.module.css";
@@ -39,22 +31,26 @@ import { LeaveToHomeLink } from "../button/LeaveToHomeLink";
 import { useLeaveToHome } from "../LeaveToHomeContext";
 import { useMediaDevices } from "../MediaDevicesContext";
 import { ObservableScope } from "../state/ObservableScope";
-import { useInitial } from "../useInitial";
-import {
-  useTrackProcessor,
-  useTrackProcessorSync,
-} from "../tracks/TrackProcessorContext";
-import { getValue } from "../utils/observable";
+import { useTrackProcessorState$ } from "../tracks/TrackProcessorContext";
 import { useBehavior } from "../useBehavior";
 import { CallFooter, type FooterSnapshot } from "../components/CallFooter";
 import { useCallViewKeyboardShortcuts } from "../useCallViewKeyboardShortcuts";
 import { createLobbyFooterViewModel } from "../components/CallFooterViewModel";
 import { type ViewModel } from "../state/ViewModel";
 import { useAppBarPrimaryButtonIconKind } from "../AppBar";
+import {
+  createLobbyMediaViewModel,
+  type LobbyMediaViewModel,
+} from "../state/LobbyMediaViewModel";
+import { captureSettings } from "./InCallView";
+
+const noVideoTrack = constant<LocalVideoMediaTrack | null>(null);

 interface Props {
  client: MatrixClient;
  matrixInfo: MatrixInfo;
+  /** The media to open the devices on; the join takes it over. */
+  media: LocalMedia;
  muteStates: MuteStates;
  onEnter: () => void;
  enterLabel?: JSX.Element | string;
@@ -68,6 +64,7 @@ interface Props {
 export const LobbyView: FC<Props> = ({
  client,
  matrixInfo,
+  media,
  muteStates,
  onEnter,
  enterLabel,
@@ -87,7 +84,6 @@ export const LobbyView: FC<Props> = ({
  const { t } = useTranslation();

  useAppBarPrimaryButtonIconKind("back");
-  const audioEnabled = useBehavior(muteStates.audio.enabled$);
  const videoEnabled = useBehavior(muteStates.video.enabled$);
  const toggleAudio = useBehavior(muteStates.audio.toggle$);
  const toggleVideo = useBehavior(muteStates.video.toggle$);
@@ -126,55 +122,28 @@ export const LobbyView: FC<Props> = ({

  const devices = useMediaDevices();
  const videoInputId = useBehavior(devices.videoInput.selected$)?.id;
+  const trackProcessorState$ = useTrackProcessorState$();

-  // Capture the audio options as they were when we first mounted, because
-  // we're not doing anything with the audio anyway so we don't need to
-  // re-open the devices when they change (see below).
-  const initialAudioOptions = useInitial(
-    () =>
-      audioEnabled && {
-        deviceId: getValue(devices.audioInput.selected$)?.id,
-      },
-  );
-
-  const { processor } = useTrackProcessor();
-
-  const initialProcessor = useInitial(() => processor);
-  const localTrackOptions = useMemo<CreateLocalTracksOptions>(
-    () => ({
-      // The only reason we request audio here is to get the audio permission
-      // request over with at the same time. But changing the audio settings
-      // shouldn't cause this hook to recreate the track, which is why we
-      // reference the initial values here.
-      // We also pass in a clone because livekit mutates the object passed in,
-      // which would cause the devices to be re-opened on the next render.
-      audio: Object.assign({}, initialAudioOptions),
-      video: videoEnabled && {
-        deviceId: videoInputId,
-        processor:
-          initialProcessor && convertToLivekitProcessor(initialProcessor),
-      },
-    }),
-    [initialAudioOptions, videoEnabled, videoInputId, initialProcessor],
-  );
-
-  const onError = useCallback(
-    (error: Error) => {
-      logger.error("Error while creating preview Tracks:", error);
-      muteStates.audio.setEnabled$.value?.(false);
-      muteStates.video.setEnabled$.value?.(false);
-    },
-    [muteStates],
-  );
-
-  const tracks = usePreviewTracks(localTrackOptions, onError);
-
-  const videoTrack = useMemo(
-    () =>
-      (tracks?.find((t) => t.kind === Track.Kind.Video) ??
-        null) as LocalVideoTrack | null,
-    [tracks],
-  );
+  const [mediaVm, setMediaVm] = useState<LobbyMediaViewModel | null>(null);
+  useEffect(() => {
+    const mediaScope = new ObservableScope();
+    setMediaVm(
+      createLobbyMediaViewModel(
+        mediaScope,
+        media,
+        muteStates,
+        devices,
+        captureSettings(),
+        mediaScope.behavior(
+          trackProcessorState$.pipe(map((state) => state.processor)),
+        ),
+      ),
+    );
+    return (): void => {
+      mediaScope.end();
+    };
+  }, [media, muteStates, devices, trackProcessorState$]);
+  const videoTrack = useBehavior(mediaVm?.videoTrack$ ?? noVideoTrack);

  useEffect(() => {
    if (videoTrack && videoInputId === undefined) {
@@ -185,8 +154,6 @@ export const LobbyView: FC<Props> = ({
    }
  }, [devices, videoInputId, videoTrack]);

-  useTrackProcessorSync(videoTrack);
-
  const [footerVm, setFooterVm] = useState<ViewModel<FooterSnapshot> | null>(
    null,
  );
@@ -7,7 +7,7 @@ Please see LICENSE in the repository root for full details.

 import { useEffect, useMemo, useRef, type FC, type ReactNode } from "react";
 import useMeasure from "react-use-measure";
-import { facingModeFromLocalTrack, type LocalVideoTrack } from "livekit-client";
+import { constant, type LocalVideoMediaTrack } from "@element-hq/matrixrtc-sdk";
 import classNames from "classnames";
 import { useTranslation } from "react-i18next";

@@ -15,6 +15,9 @@ import { TileAvatar } from "../tile/TileAvatar";
 import styles from "./VideoPreview.module.css";
 import { type EncryptionSystem } from "../e2ee/sharedKeyManagement";
 import videoPlaceholder from "../graphics/video-placeholder.gif";
+import { useBehavior } from "../useBehavior";
+
+const noFacingMode = constant(undefined);

 export type MatrixInfo = {
  userId: string;
@@ -30,7 +33,7 @@ export type MatrixInfo = {
 interface Props {
  matrixInfo: MatrixInfo;
  videoEnabled: boolean;
-  videoTrack: LocalVideoTrack | null;
+  videoTrack: LocalVideoMediaTrack | null;
  children: ReactNode;
 }

@@ -46,14 +49,12 @@ export const VideoPreview: FC<Props> = ({
  const videoEl = useRef<HTMLVideoElement | null>(null);

  useEffect(() => {
-    // Effect to connect the videoTrack with the video element.
-    if (videoEl.current) {
-      videoTrack?.attach(videoEl.current);
-    }
-    return (): void => {
-      videoTrack?.detach();
-    };
+    const element = videoEl.current;
+    if (!element || !videoTrack) return;
+    videoTrack.attach(element);
+    return (): void => videoTrack.detach(element);
  }, [videoTrack]);
+  const facingMode = useBehavior(videoTrack?.facingMode$ ?? noFacingMode);

  const cameraIsStarting = useMemo(
    () => videoEnabled && !videoTrack,
@@ -63,12 +64,7 @@ export const VideoPreview: FC<Props> = ({
  return (
    <div className={classNames(styles.preview)} ref={previewRef}>
      <video
-        className={
-          videoTrack &&
-          facingModeFromLocalTrack(videoTrack).facingMode === "user"
-            ? styles.mirror
-            : undefined
-        }
+        className={facingMode === "user" ? styles.mirror : undefined}
        ref={videoEl}
        muted
        playsInline
@@ -14,7 +14,6 @@ import {
  type EncryptionSystem,
  generateItems,
  type LocalAudioMediaTrack,
-  type LocalMediaTrack,
  type LocalRTCMember,
  type LocalVideoMediaTrack,
  type RTCParticipation,
@@ -79,8 +78,14 @@ import {
  type ReactionOption,
 } from "../../reactions";
 import { shallowEquals as arrayShallowEquals } from "../../utils/array";
-import { type MediaDevice, type MediaDevices } from "../MediaDevices";
-import { type Handler, type MuteStates } from "../MuteStates";
+import { type MediaDevices } from "../MediaDevices";
+import { type MuteStates } from "../MuteStates";
+import {
+  followDevice,
+  followMuteState,
+  followProcessor,
+  type TrackSupply,
+} from "../localMediaControls";
 import { HeaderStyle, type UrlParams } from "../../UrlParams";
 import { type HostBridge, nullHostBridge } from "../../HostBridge";
 import {
@@ -503,72 +508,34 @@ export function createCallViewModel$(
    "screenShare",
  ) as Behavior<LocalVideoMediaTrack | undefined>;

-  // The mute switches drive our tracks, which report back what the device
-  // allowed, so a denied permission flips the switch back. A source is muted
-  // and unmuted while its track exists and published when it does not.
-  const followMuteState = (
-    muteState: {
-      setHandler: (handler: Handler) => void;
-      enabled$: Behavior<boolean>;
-    },
-    track$: Behavior<LocalMediaTrack | undefined>,
-    source: "microphone" | "camera",
-  ): void => {
-    // What the switch asks for, ahead of what it shows: the switch follows
-    // only once the handler has resolved
-    let desired = muteState.enabled$.value;
-    muteState.setHandler(async (enabled) => {
-      desired = enabled;
-      const track = track$.value;
-      if (track !== undefined) {
-        desired = await track.setEnabled(enabled);
-        return desired;
-      }
-      if (!enabled) return false;
-      try {
-        await rtcParticipation.publish(
-          publishRequest(source, mediaDevices, capture),
-        );
-        return true;
-      } catch (e) {
-        logger.error(`Failed to publish the ${source}`, e);
-        desired = false;
-        return false;
-      }
-    });
-    // A track that arrives after its switch was flipped off catches up with it
-    track$.pipe(scope.bind()).subscribe((track) => {
-      if (track !== undefined && !desired)
-        track.setEnabled(false).catch((e) => {
-          logger.error(`Failed to mute the ${source}`, e);
-        });
-    });
-  };
-  followMuteState(muteStates.audio, microphone$, "microphone");
-  followMuteState(muteStates.video, camera$, "camera");
-  scope.onEnd(() => {
-    muteStates.audio.unsetHandler();
-    muteStates.video.unsetHandler();
+  const supply = (source: "microphone" | "camera"): TrackSupply => ({
+    publish: async () =>
+      rtcParticipation.publish(publishRequest(source, mediaDevices, capture)),
  });
-
-  // The device the user picked follows onto the track as it is made and as the
-  // choice changes; the SDK does not watch the settings itself
-  const followDevice = (
-    track$: Behavior<LocalMediaTrack | undefined>,
-    device: MediaDevice<unknown, { id: string }>,
-    source: "microphone" | "camera",
-  ): void => {
-    combineLatest([track$, device.selected$])
-      .pipe(scope.bind())
-      .subscribe(([track, selected]) => {
-        if (track === undefined || selected === undefined) return;
-        track.setDevice(selected.id).catch((e) => {
-          logger.error(`Failed to switch the ${source} device`, e);
-        });
-      });
-  };
-  followDevice(microphone$, mediaDevices.audioInput, "microphone");
-  followDevice(camera$, mediaDevices.videoInput, "camera");
+  followMuteState(
+    scope,
+    muteStates.audio,
+    microphone$,
+    supply("microphone"),
+    "microphone",
+    logger,
+  );
+  followMuteState(
+    scope,
+    muteStates.video,
+    camera$,
+    supply("camera"),
+    "camera",
+    logger,
+  );
+  followDevice(
+    scope,
+    microphone$,
+    mediaDevices.audioInput,
+    "microphone",
+    logger,
+  );
+  followDevice(scope, camera$, mediaDevices.videoInput, "camera", logger);

  // The output device follows the selection onto the client the same way. A
  // host that routes audio itself picks the output outside the browser, so the
@@ -583,15 +550,7 @@ export function createCallViewModel$(
        });
      });

-  // Attached once the camera track exists rather than carried in the publish
-  // request, so that a new track and a change of processor take the same path
-  combineLatest([camera$, videoProcessor$])
-    .pipe(scope.bind())
-    .subscribe(([camera, processor]) => {
-      camera?.setProcessor(processor).catch((e) => {
-        logger.error("Failed to set the video processor", e);
-      });
-    });
+  followProcessor(scope, camera$, videoProcessor$, logger);

  const members$ = scope.behavior<(LocalRTCMember | RemoteRTCMember)[]>(
    combineLatest(
@@ -0,0 +1,166 @@
+/*
+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, vi } from "vitest";
+import { BehaviorSubject, of } from "rxjs";
+import {
+  constant,
+  type LocalAudioMediaTrack,
+  type LocalMedia,
+  type LocalVideoMediaTrack,
+  type PublishRequest,
+  type VideoProcessor,
+} from "@element-hq/matrixrtc-sdk";
+
+import { createLobbyMediaViewModel } from "./LobbyMediaViewModel";
+import { type MediaDevices } from "./MediaDevices";
+import { MuteStates } from "./MuteStates";
+import { nullHostBridge } from "../HostBridge";
+import { flushPromises, mockMediaDevices, testScope } from "../utils/test";
+
+describe("LobbyMediaViewModel", () => {
+  it("opens what starts enabled in one capture and follows the devices", async () => {
+    const { media, vm, mediaDevices } = setup();
+    await flushPromises();
+
+    expect(media.capture).toHaveBeenCalledExactlyOnceWith([
+      expect.objectContaining({ source: "microphone", deviceId: "mic" }),
+      expect.objectContaining({ source: "camera", deviceId: "cam" }),
+    ]);
+    const camera = vm.videoTrack$.value!;
+    expect(camera.source).toBe("camera");
+    expect(camera.setDevice).toHaveBeenCalledWith("cam");
+    expect(camera.setProcessor).toHaveBeenCalledWith(processor);
+    mediaDevices.videoInput.selected$ satisfies unknown;
+  });
+
+  it("closes the camera when its switch goes off and reopens it when on", async () => {
+    const { media, vm, muteStates } = setup();
+    await flushPromises();
+
+    muteStates.video.setEnabled$.value?.(false);
+    await flushPromises();
+    expect(media.release).toHaveBeenCalledWith("camera");
+    expect(vm.videoTrack$.value).toBeNull();
+
+    muteStates.video.setEnabled$.value?.(true);
+    await flushPromises();
+    expect(media.capture).toHaveBeenLastCalledWith([
+      expect.objectContaining({ source: "camera" }),
+    ]);
+    expect(vm.videoTrack$.value?.source).toBe("camera");
+  });
+
+  it("mutes the microphone in place", async () => {
+    const { media, muteStates } = setup();
+    await flushPromises();
+    const microphone = media.tracks$.value.find(
+      (t) => t.source === "microphone",
+    )!;
+
+    muteStates.audio.setEnabled$.value?.(false);
+    await flushPromises();
+
+    expect(microphone.setEnabled).toHaveBeenCalledWith(false);
+    expect(media.release).not.toHaveBeenCalled();
+    expect(muteStates.audio.enabled$.value).toBe(false);
+  });
+
+  it("leaves both switches off where the devices cannot be opened", async () => {
+    const { muteStates } = setup(async () =>
+      Promise.reject(new Error("NotAllowedError")),
+    );
+    await flushPromises();
+
+    expect(muteStates.audio.enabled$.value).toBe(false);
+    expect(muteStates.video.enabled$.value).toBe(false);
+  });
+});
+
+const processor = { name: "blur" } as VideoProcessor;
+
+function setup(
+  capture: (
+    requests: PublishRequest[],
+  ) => Promise<(LocalAudioMediaTrack | LocalVideoMediaTrack)[]> = async (
+    requests,
+  ) => Promise.resolve(requests.map(fakeTrack)),
+): {
+  media: LocalMedia;
+  vm: ReturnType<typeof createLobbyMediaViewModel>;
+  muteStates: MuteStates;
+  mediaDevices: MediaDevices;
+} {
+  const scope = testScope();
+  const tracks$ = new BehaviorSubject<
+    (LocalAudioMediaTrack | LocalVideoMediaTrack)[]
+  >([]);
+  const media: LocalMedia = {
+    requests: [],
+    tracks$,
+    capture: vi.fn(async (requests: PublishRequest[]) => {
+      const tracks = await capture(requests);
+      tracks$.next([
+        ...tracks$.value.filter(
+          (t) => !tracks.some((n) => n.source === t.source),
+        ),
+        ...tracks,
+      ]);
+      return tracks;
+    }),
+    release: vi.fn((source) =>
+      tracks$.next(tracks$.value.filter((t) => t.source !== source)),
+    ),
+    stop: vi.fn(),
+    takeTracks: () => new Map(),
+  };
+  const mediaDevices = mockMediaDevices({
+    audioInput: device("mic"),
+    videoInput: device("cam"),
+  } as Partial<MediaDevices>);
+  const muteStates = new MuteStates(
+    scope,
+    mediaDevices,
+    { audioEnabled: true, videoEnabled: true },
+    nullHostBridge,
+  );
+  const vm = createLobbyMediaViewModel(
+    scope,
+    media,
+    muteStates,
+    mediaDevices,
+    {},
+    constant(processor),
+  );
+  return { media, vm, muteStates, mediaDevices };
+}
+
+function device(id: string): unknown {
+  return {
+    available$: of(new Map([[id, { type: "name", name: id }]])),
+    selected$: new BehaviorSubject({ id }),
+    select: (): void => {},
+  };
+}
+
+function fakeTrack(
+  request: PublishRequest,
+): LocalAudioMediaTrack | LocalVideoMediaTrack {
+  const muted$ = new BehaviorSubject(false);
+  return {
+    source: request.source,
+    kind: request.source === "microphone" ? "audio" : "video",
+    id: request.source,
+    muted$,
+    setEnabled: vi.fn(async (enabled: boolean) => {
+      muted$.next(!enabled);
+      return Promise.resolve(enabled);
+    }),
+    setDevice: vi.fn(async () => Promise.resolve()),
+    setProcessor: vi.fn(async () => Promise.resolve()),
+  } as unknown as LocalAudioMediaTrack | LocalVideoMediaTrack;
+}
@@ -0,0 +1,113 @@
+/*
+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 Behavior,
+  type LocalAudioMediaTrack,
+  type LocalMedia,
+  type LocalVideoMediaTrack,
+  type ObservableScope,
+  type PublishRequest,
+  trackBySource$,
+  type VideoProcessor,
+} from "@element-hq/matrixrtc-sdk";
+import { logger as rootLogger } from "matrix-js-sdk/lib/logger";
+import { combineLatest, debounceTime, map } from "rxjs";
+
+import {
+  type CaptureSettings,
+  publishRequest,
+} from "./CallViewModel/CallViewModel";
+import { type MediaDevices } from "./MediaDevices";
+import { type MuteStates } from "./MuteStates";
+import { followDevice, followProcessor } from "./localMediaControls";
+
+export interface LobbyMediaViewModel {
+  /** The camera, once open, for the preview. */
+  videoTrack$: Behavior<LocalVideoMediaTrack | null>;
+}
+
+/**
+ * The local media of the lobby: the devices the mute switches ask for, opened
+ * ahead of the join on the media the join is then given, so that the call
+ * publishes the very tracks the user previewed.
+ */
+export function createLobbyMediaViewModel(
+  scope: ObservableScope,
+  media: LocalMedia,
+  muteStates: MuteStates,
+  mediaDevices: MediaDevices,
+  capture: CaptureSettings,
+  videoProcessor$: Behavior<VideoProcessor | undefined>,
+): LobbyMediaViewModel {
+  const logger = rootLogger.getChild("[LobbyMedia]");
+  const microphone$ = trackBySource$(
+    scope,
+    media.tracks$,
+    "microphone",
+  ) as Behavior<LocalAudioMediaTrack | undefined>;
+  const camera$ = trackBySource$(scope, media.tracks$, "camera") as Behavior<
+    LocalVideoMediaTrack | undefined
+  >;
+
+  // One could ask why this is not just done via followMuteStates.
+  // The main purpose why this code exists is to handle the native browser permission
+  // prompts properly.
+  // no prompt if everything is muted, shared prompt if both are requested.
+  const opening = new Set<PublishRequest["source"]>();
+  combineLatest([
+    muteStates.audio.enabled$,
+    muteStates.video.enabled$,
+    microphone$,
+    camera$,
+  ])
+    .pipe(debounceTime(0), scope.bind())
+    .subscribe(([audio, video, microphone, camera]) => {
+      const open: PublishRequest[] = [];
+      if (audio && microphone === undefined && !opening.has("microphone"))
+        open.push(publishRequest("microphone", mediaDevices, capture));
+      if (video && camera === undefined && !opening.has("camera"))
+        open.push(publishRequest("camera", mediaDevices, capture));
+      if (open.length > 0) {
+        for (const { source } of open) opening.add(source);
+        media
+          .capture(open)
+          .catch((e) => {
+            logger.error("Failed to open the devices", e);
+            // A device that cannot be opened leaves its switch off
+            for (const { source } of open)
+              (source === "microphone"
+                ? muteStates.audio
+                : muteStates.video
+              ).setEnabled$.value?.(false);
+          })
+          .finally(() => {
+            for (const { source } of open) opening.delete(source);
+          });
+      }
+      // The camera is closed rather than muted, so that its light goes off
+      if (!video && camera !== undefined) media.release("camera");
+      if (microphone !== undefined && microphone.muted$.value === audio)
+        microphone.setEnabled(audio).catch((e) => {
+          logger.error("Failed to mute the microphone", e);
+        });
+    });
+
+  followDevice(
+    scope,
+    microphone$,
+    mediaDevices.audioInput,
+    "microphone",
+    logger,
+  );
+  followDevice(scope, camera$, mediaDevices.videoInput, "camera", logger);
+  followProcessor(scope, camera$, videoProcessor$, logger);
+
+  return {
+    videoTrack$: scope.behavior(camera$.pipe(map((camera) => camera ?? null))),
+  };
+}
@@ -0,0 +1,111 @@
+/*
+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 Behavior,
+  type LocalMediaTrack,
+  type LocalVideoMediaTrack,
+  type ObservableScope,
+  type VideoProcessor,
+} from "@element-hq/matrixrtc-sdk";
+import { type Logger } from "matrix-js-sdk/lib/logger";
+import { combineLatest } from "rxjs";
+
+import { type MediaDevice } from "./MediaDevices";
+import { type Handler } from "./MuteStates";
+
+/** How a mute switch gets a track where there is none. */
+export interface TrackSupply {
+  publish: () => Promise<unknown>;
+}
+
+/**
+ * The mute switch drives the track, which reports back what the device
+ * allowed, so a denied permission flips the switch back. A source is muted
+ * and unmuted while its track exists and published when it does not.
+ */
+export function followMuteState(
+  scope: ObservableScope,
+  muteState: {
+    setHandler: (handler: Handler) => void;
+    unsetHandler: () => void;
+    enabled$: Behavior<boolean>;
+  },
+  track$: Behavior<LocalMediaTrack | undefined>,
+  supply: TrackSupply,
+  source: "microphone" | "camera",
+  logger: Logger,
+): void {
+  // What the switch asks for, ahead of what it shows: the switch follows
+  // only once the handler has resolved
+  let desired = muteState.enabled$.value;
+  muteState.setHandler(async (enabled) => {
+    desired = enabled;
+    const track = track$.value;
+    if (track !== undefined) {
+      desired = await track.setEnabled(enabled);
+      return desired;
+    }
+    if (!enabled) return false;
+    try {
+      await supply.publish();
+      return true;
+    } catch (e) {
+      logger.error(`Failed to publish the ${source}`, e);
+      desired = false;
+      return false;
+    }
+  });
+  scope.onEnd(() => muteState.unsetHandler());
+  // A track that arrives after its switch was flipped off catches up with it
+  track$.pipe(scope.bind()).subscribe((track) => {
+    if (track !== undefined && !desired)
+      track.setEnabled(false).catch((e) => {
+        logger.error(`Failed to mute the ${source}`, e);
+      });
+  });
+}
+
+/**
+ * The device the user picked follows onto the track as it is made and as the
+ * choice changes; the SDK does not watch the settings itself.
+ */
+export function followDevice(
+  scope: ObservableScope,
+  track$: Behavior<LocalMediaTrack | undefined>,
+  device: MediaDevice<unknown, { id: string }>,
+  source: "microphone" | "camera",
+  logger: Logger,
+): void {
+  combineLatest([track$, device.selected$])
+    .pipe(scope.bind())
+    .subscribe(([track, selected]) => {
+      if (track === undefined || selected === undefined) return;
+      track.setDevice(selected.id).catch((e) => {
+        logger.error(`Failed to switch the ${source} device`, e);
+      });
+    });
+}
+
+/**
+ * Attached once the camera track exists rather than carried in the publish
+ * request, so that a new track and a change of processor take the same path.
+ */
+export function followProcessor(
+  scope: ObservableScope,
+  camera$: Behavior<LocalVideoMediaTrack | undefined>,
+  videoProcessor$: Behavior<VideoProcessor | undefined>,
+  logger: Logger,
+): void {
+  combineLatest([camera$, videoProcessor$])
+    .pipe(scope.bind())
+    .subscribe(([camera, processor]) => {
+      camera?.setProcessor(processor).catch((e) => {
+        logger.error("Failed to set the video processor", e);
+      });
+    });
+}
@@ -235,22 +235,35 @@ test("audio and video follow the tracks' mute state", () => {

 test("user media polls stream stats only while the setting is on", () => {
  onTestFinished(() => showConnectionStats.setValue(false));
+
  withTestScheduler(({ cold, expectObservable, schedule }) => {
    const stats = { type: "inbound-rtp" } as RTCInboundRtpStreamStats;
    const vm = mockRemoteMedia(rtcMembership, {}, [
-      mockAudioTrack({
-        stats$: () => cold("-s", { s: stats }),
-      }),
+      mockAudioTrack({ stats$: () => cold("-s", { s: { ...stats } }) }),
    ]);
-    schedule("-a-b", {
-      a() {
-        showConnectionStats.setValue(true);
-      },
-      b() {
-        showConnectionStats.setValue(false);
-      },
+    schedule("-t-f-t", {
+      t: () => showConnectionStats.setValue(true),
+      f: () => showConnectionStats.setValue(false),
    });
-    expectObservable(vm.audioStreamStats$).toBe("u-su", {
+
+    expectObservable(vm.audioStreamStats$).toBe("u-s---s", {
+      u: undefined,
+      s: stats,
+    });
+  });
+});
+
+test("stream stats can be enabled before creating media", () => {
+  showConnectionStats.setValue(true);
+  onTestFinished(() => showConnectionStats.setValue(false));
+
+  withTestScheduler(({ cold, expectObservable }) => {
+    const stats = { type: "inbound-rtp" } as RTCInboundRtpStreamStats;
+    const vm = mockRemoteMedia(rtcMembership, {}, [
+      mockAudioTrack({ stats$: () => cold("-s", { s: stats }) }),
+    ]);
+
+    expectObservable(vm.audioStreamStats$).toBe("us", {
      u: undefined,
      s: stats,
    });
@@ -16,7 +16,9 @@ import {
  BehaviorSubject,
  combineLatest,
  map,
+  NEVER,
  of,
+  startWith,
  Subject,
  switchMap,
 } from "rxjs";
@@ -105,10 +107,9 @@ export function createBaseUserMedia(
        showConnectionStats.value$,
      ]).pipe(
        switchMap(([track, show]) =>
-          track !== undefined && show
-            ? track.stats$(statsIntervalMs)
-            : of(undefined),
+          track !== undefined && show ? track.stats$(statsIntervalMs) : NEVER,
        ),
+        startWith<MediaStreamStats>(undefined),
      ),
    );

@@ -6,94 +6,12 @@ Please see LICENSE in the repository root for full details.
 */

 import { describe, expect, it, vi } from "vitest";
-import { type LocalVideoTrack } from "livekit-client";
 import {
  type BackgroundOptions,
  type ProcessorWrapper,
 } from "@livekit/track-processors";
-import { type VideoProcessor } from "@element-hq/matrixrtc-sdk";

-import {
-  applyProcessor,
-  fromLivekitProcessor,
-  trackProcessorSync,
-} from "./TrackProcessorContext";
-import { constant } from "../state/Behavior";
-import { flushPromises, testScope } from "../utils/test";
-
-const processor = { name: "blur" } as VideoProcessor;
-
-function mockTrack(
-  readyState: MediaStreamTrackState,
-  current?: VideoProcessor,
-): LocalVideoTrack {
-  return {
-    mediaStreamTrack: { readyState },
-    getProcessor: vi.fn().mockReturnValue(current),
-    setProcessor: vi.fn().mockResolvedValue(undefined),
-    stopProcessor: vi.fn().mockResolvedValue(undefined),
-  } as unknown as LocalVideoTrack;
-}
-
-describe("applyProcessor", () => {
-  it("attaches the processor to a live track", () => {
-    const track = mockTrack("live");
-    applyProcessor(track, processor);
-    expect(track.setProcessor).toHaveBeenCalledWith(
-      expect.objectContaining({ name: "blur" }),
-    );
-  });
-
-  it("does not attach the processor to an ended track", () => {
-    const track = mockTrack("ended");
-    applyProcessor(track, processor);
-    expect(track.setProcessor).not.toHaveBeenCalled();
-  });
-
-  it("does not surface a rejected setProcessor", async () => {
-    const track = mockTrack("live");
-    vi.mocked(track.setProcessor).mockRejectedValue(
-      new TypeError("Input track cannot be ended"),
-    );
-    const unhandled = vi.fn();
-    process.on("unhandledRejection", unhandled);
-    applyProcessor(track, processor);
-    await flushPromises();
-    process.off("unhandledRejection", unhandled);
-    expect(unhandled).not.toHaveBeenCalled();
-  });
-
-  it("stops the processor when none is wanted", () => {
-    const track = mockTrack("live", processor);
-    applyProcessor(track, undefined);
-    expect(track.stopProcessor).toHaveBeenCalled();
-  });
-
-  it("does not surface a rejected stopProcessor", async () => {
-    const track = mockTrack("live", processor);
-    vi.mocked(track.stopProcessor).mockRejectedValue(new Error("nope"));
-    const unhandled = vi.fn();
-    process.on("unhandledRejection", unhandled);
-    applyProcessor(track, undefined);
-    await flushPromises();
-    process.off("unhandledRejection", unhandled);
-    expect(unhandled).not.toHaveBeenCalled();
-  });
-});
-
-describe("trackProcessorSync", () => {
-  it("applies the processor to the current track", () => {
-    const track = mockTrack("live");
-    trackProcessorSync(
-      testScope(),
-      constant(track),
-      constant({ supported: true, processor }),
-    );
-    expect(track.setProcessor).toHaveBeenCalledWith(
-      expect.objectContaining({ name: "blur" }),
-    );
-  });
-});
+import { fromLivekitProcessor } from "./TrackProcessorContext";

 describe("fromLivekitProcessor", () => {
  const captured = { id: "captured" } as MediaStreamTrack;
@@ -10,21 +10,9 @@ import {
  supportsBackgroundProcessors as supportsBackgroundProcessorsLivekitSdk,
  type BackgroundOptions,
 } from "@livekit/track-processors";
-import {
-  createContext,
-  type FC,
-  type JSX,
-  use,
-  useEffect,
-  useMemo,
-} from "react";
-import { type LocalVideoTrack, Track } from "livekit-client";
-import { logger } from "matrix-js-sdk/lib/logger";
-import { combineLatest } from "rxjs";
-import {
-  convertToLivekitProcessor,
-  type VideoProcessor,
-} from "@element-hq/matrixrtc-sdk";
+import { createContext, type FC, type JSX, use, useMemo } from "react";
+import { Track } from "livekit-client";
+import { type VideoProcessor } from "@element-hq/matrixrtc-sdk";

 import {
  backgroundBlur as backgroundBlurSettings,
@@ -32,7 +20,6 @@ import {
 } from "../settings/settings";
 import { BlurBackgroundTransformer } from "./BlurBackgroundTransformer";
 import { type Behavior } from "../state/Behavior";
-import { type ObservableScope } from "../state/ObservableScope";
 import { platform } from "../Platform";
 import { useValueBehavior } from "../useValueBehavior";

@@ -87,61 +74,6 @@ export function useTrackProcessorState$(): Behavior<ProcessorState> {
  return useValueBehavior(useTrackProcessor());
 }

-/**
- * Attaches or detaches the processor so that the track matches the desired
- * state, without throwing.
- */
-export function applyProcessor(
-  videoTrack: LocalVideoTrack,
-  processor: VideoProcessor | undefined,
-): void {
-  if (processor && !videoTrack.getProcessor()) {
-    // A MediaStreamTrackProcessor cannot be constructed on an ended track
-    // (e.g. the camera was stopped while the processor was being applied),
-    // and setProcessor rejects with a TypeError. The track is going away
-    // anyway, so there is nothing to attach to.
-    if (videoTrack.mediaStreamTrack.readyState === "ended") {
-      logger.debug("Not attaching video processor to an ended track");
-      return;
-    }
-    videoTrack.setProcessor(convertToLivekitProcessor(processor)).catch((e) => {
-      logger.warn("Failed to attach video processor", e);
-    });
-  }
-  if (!processor && videoTrack.getProcessor()) {
-    videoTrack.stopProcessor().catch((e) => {
-      logger.warn("Failed to stop video processor", e);
-    });
-  }
-}
-
-/**
- * Updates your video tracks to always use the given processor.
- */
-export const trackProcessorSync = (
-  scope: ObservableScope,
-  videoTrack$: Behavior<LocalVideoTrack | null>,
-  processor$: Behavior<ProcessorState>,
-): void => {
-  combineLatest([videoTrack$, processor$])
-    .pipe(scope.bind())
-    .subscribe(([videoTrack, processorState]) => {
-      if (!processorState) return;
-      if (!videoTrack) return;
-      applyProcessor(videoTrack, processorState.processor);
-    });
-};
-
-export const useTrackProcessorSync = (
-  videoTrack: LocalVideoTrack | null,
-): void => {
-  const { processor } = useTrackProcessor();
-  useEffect(() => {
-    if (!videoTrack) return;
-    applyProcessor(videoTrack, processor);
-  }, [processor, videoTrack]);
-};
-
 interface Props {
  children: JSX.Element;
 }
@@ -8,8 +8,55 @@ Please see LICENSE in the repository root for full details.
 import { act, renderHook } from "@testing-library/react";
 import { BehaviorSubject } from "rxjs";
 import { describe, expect, test } from "vitest";
+import { useCallback, useSyncExternalStore } from "react";

 import { useBehavior } from "./useBehavior";
+import { type Behavior } from "./state/Behavior";
+
+/**
+ * The implementation `useBehavior` replaced, kept here as proof of why. The
+ * React Compiler (on for the tests as for the app) memoizes `getValue` on
+ * `behavior.value`, not on `behavior`:
+ *
+ *     if ($[2] !== behavior.value) { t1 = () => behavior.value; ... }
+ *
+ * So when the hook switches to a behavior that holds the same value as the
+ * prev one, `getValue` still reads the old behavior. The new behavior's
+ * emissions do reach React, but the snapshot it reads is unchanged, and the
+ * view is left stale. The lobby switches from a placeholder to the view
+ * model's camera behavior, both starting on null, which hit exactly this.
+ */
+function useBehaviorExternalStore<T>(behavior: Behavior<T>): T {
+  const subscribe = useCallback(
+    (onChange: () => void) => {
+      const s = behavior.subscribe(onChange);
+      return (): void => s.unsubscribe();
+    },
+    [behavior],
+  );
+  const getValue = useCallback(() => behavior.value, [behavior]);
+  return useSyncExternalStore(subscribe, getValue);
+}
+
+/**
+ * Renders the hook on one behavior, switches it to a second one holding the
+ * same value, and then emits on the second.
+ */
+function switchToSameValue(
+  hook: (behavior: Behavior<string | null>) => string | null,
+): string | null {
+  const first$ = new BehaviorSubject<string | null>(null);
+  const second$ = new BehaviorSubject<string | null>(null);
+  const { result, rerender } = renderHook(
+    ({ value$ }: { value$: Behavior<string | null> }) => hook(value$),
+    { initialProps: { value$: first$ } },
+  );
+  expect(result.current).toBeNull();
+
+  rerender({ value$: second$ });
+  act(() => second$.next("second"));
+  return result.current;
+}

 describe("useBehavior", () => {
  test("reads the current value and follows changes", () => {
@@ -20,4 +67,29 @@ describe("useBehavior", () => {
    act(() => value$.next(2));
    expect(result.current).toBe(2);
  });
+
+  test("follows a new behavior that starts on the same value", () => {
+    expect(switchToSameValue(useBehavior)).toBe("second");
+  });
+
+  test("does not follow the behavior it switched away from", () => {
+    const first$ = new BehaviorSubject<string | null>(null);
+    const second$ = new BehaviorSubject<string | null>(null);
+    const { result, rerender } = renderHook(
+      ({ value$ }: { value$: Behavior<string | null> }) => useBehavior(value$),
+      { initialProps: { value$: first$ } },
+    );
+    rerender({ value$: second$ });
+    act(() => first$.next("first"));
+    expect(result.current).toBeNull();
+  });
+});
+
+describe("useBehaviorExternalStore", () => {
+  // This asserts the bug, not the wanted behaviour: it is the reason
+  // `useBehavior` does not use `useSyncExternalStore`. Should it ever fail,
+  // the compiler has changed and the simpler implementation can come back.
+  test("misses the emission of a new behavior that starts on the same value", () => {
+    expect(switchToSameValue(useBehaviorExternalStore)).toBeNull();
+  });
 });
@@ -5,21 +5,39 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */

-import { useCallback, useSyncExternalStore } from "react";
+import { useEffect, useState } from "react";

 import { type Behavior } from "./state/Behavior";

+interface Read<T> {
+  behavior: Behavior<T>;
+  value: T;
+}
+
 /**
 * React hook which reactively reads the value of a behavior.
+ *
+ * A plain subscription rather than `useSyncExternalStore`: the React Compiler
+ * memoizes a snapshot getter `() => behavior.value` on the value rather than
+ * the behavior, so a view switching to a behavior that starts on the same
+ * value (a view model arriving after the first render) kept reading the old
+ * one, and React saw no change in the new one's emissions.
 */
 export function useBehavior<T>(behavior: Behavior<T>): T {
-  const subscribe = useCallback(
-    (onChange: () => void) => {
-      const s = behavior.subscribe(onChange);
-      return (): void => s.unsubscribe();
-    },
-    [behavior],
-  );
-  const getValue = useCallback(() => behavior.value, [behavior]);
-  return useSyncExternalStore(subscribe, getValue);
+  const [read, setRead] = useState<Read<T>>(() => ({
+    behavior,
+    value: behavior.value,
+  }));
+  useEffect(() => {
+    const subscription = behavior.subscribe((value) => {
+      // By value alone: a behavior built during the render is new every
+      // time, and adopting it for the same value would render forever
+      setRead((current) =>
+        Object.is(current.value, value) ? current : { behavior, value },
+      );
+    });
+    return (): void => subscription.unsubscribe();
+  }, [behavior]);
+  // Until the subscription to a new behavior is in place, read it directly
+  return read.behavior === behavior ? read.value : behavior.value;
 }
@@ -0,0 +1,21 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { useEffect } from "react";
+import { createLocalMedia, type LocalMedia } from "@element-hq/matrixrtc-sdk";
+
+import { useInitial } from "./useInitial";
+
+/**
+ * Local media for the lobby to open and the join to take over, released with
+ * the component where the join never comes.
+ */
+export function useLocalMedia(): LocalMedia {
+  const media = useInitial(() => createLocalMedia());
+  useEffect(() => (): void => media.stop(), [media]);
+  return media;
+}
@@ -38,8 +38,21 @@ export default defineConfig(({ mode }) => {
    ...base,
    root: "component/dev",
    // The same scoping the library build applies, so the harness shows what a
-    // host will get — including whether its own page is left alone
-    css: { postcss: { plugins: [scopeStylesToRoot()] } },
+    // host will get — including whether its own page is left alone. The host's
+    // own stylesheets, Compound's among them, stay unscoped, as on a real host.
+    css: {
+      postcss: {
+        plugins: [
+          scopeStylesToRoot({
+            exclude: [
+              /component[\\/]dev[\\/]/,
+              /@vector-im[\\/]compound-/,
+              /@fontsource[\\/]/,
+            ],
+          }),
+        ],
+      },
+    },
    // So that the harness can read the same config.json the standalone app
    // does, if the developer has written one
    publicDir: "../../public",
@@ -89,6 +89,7 @@ export default defineConfig(({ mode }) => {
          "react-dom",
          "react-dom/client",
          "matrix-js-sdk",
+          "matrix-js-sdk/lib/@types/event",
          "matrix-js-sdk/lib/browser-index",
          "matrix-js-sdk/lib/client",
          "matrix-js-sdk/lib/crypto-api",
@@ -99,8 +100,10 @@ export default defineConfig(({ mode }) => {
          "matrix-js-sdk/lib/matrixrtc/EncryptionManager",
          "matrix-js-sdk/lib/matrixrtc/IKeyTransport",
          "matrix-js-sdk/lib/matrixrtc/IMembershipManager",
+          "matrix-js-sdk/lib/models/event",
          "matrix-js-sdk/lib/models/relations-container",
          "matrix-js-sdk/lib/models/room",
+          "matrix-js-sdk/lib/models/room-state",
          "matrix-js-sdk/lib/models/typed-event-emitter",
          "matrix-js-sdk/lib/randomstring",
          "matrix-js-sdk/lib/sync",
@@ -7,6 +7,7 @@ Please see LICENSE in the repository root for full details.

 import {
  loadEnv,
+  type Plugin,
  type PluginOption,
  searchForWorkspaceRoot,
  type ConfigEnv,
@@ -43,10 +44,12 @@ export const vitePluginsConfig = ({
    }),
    react(),
    wasm(),
-    nodePolyfills({
-      // Enables the 'events' module, which is required by the matrix-js-sdk
-      include: ["events"],
-    }),
+    exceptMediaPipeWasm(
+      nodePolyfills({
+        // Enables the 'events' module, which is required by the matrix-js-sdk
+        include: ["events"],
+      }),
+    ),
    svgrPlugin({
      svgrOptions: {
        // This enables ref forwarding on SVGR components, which is needed, for
@@ -191,3 +194,31 @@ export default ({
    },
  };
 };
+
+/**
+ * Keeps a plugin's transform off MediaPipe's WASM loader. The loader is a
+ * classic script that sets `self.ModuleFactory`; transformed into a module it
+ * sets nothing, and the segmenter fails with "ModuleFactory not set".
+ */
+function exceptMediaPipeWasm(plugins: PluginOption): PluginOption {
+  const isLoader = (id: string): boolean =>
+    id.includes("tasks-vision") && id.includes("wasm");
+  return (Array.isArray(plugins) ? plugins : [plugins]).map((plugin) => {
+    if (
+      !plugin ||
+      typeof plugin !== "object" ||
+      !("transform" in plugin) ||
+      typeof plugin.transform !== "function"
+    )
+      return plugin;
+    const transform = plugin.transform;
+    const wrapped: Plugin = {
+      ...plugin,
+      transform(code, id, options) {
+        if (isLoader(id)) return null;
+        return transform.call(this, code, id, options);
+      },
+    };
+    return wrapped;
+  });
+}
Author	SHA1	Message	Date
Timo K.andClaude Fable 5.1	69c57bd534	Run the lobby on the SDK's local media and keep its tracks through the join The lobby captured its own LiveKit tracks and the join captured again: two permission prompts, a grey tile while the camera restarted, and the background pipeline built twice. The lobby now opens the devices on the SDK's `LocalMedia`, follows the mute switches as they change (they start off until the devices are enumerated), the device choice and the processor through controls shared with the call view model, and the call joins with that media, so the tile carries the very track the lobby previewed. `useBehavior` subscribes without `useSyncExternalStore`, which left a view without a re-render for an emission React had been told about, about one time in three, when its store had switched. The LiveKit preview hook and the processor sync helpers go, with `@livekit/components-react`. Background effects run under the dev server: the node polyfill no longer rewrites MediaPipe's WASM loader. Taken from fkwp's `2fad4e08` on spec/background-effects/2-pipeline (#4282). Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>	2026-11-04 18:59:11 +01:00
Timo K.andClaude Fable 5.1	734ecbbecf	[SDK] Capture local media ahead of the join and hand it to the participation A lobby captures the microphone and the camera on the browser's devices alone, with `createLocalMedia`, so that any backend can take them over: `LocalMedia` hands out the same `LocalAudioMediaTrack` and `LocalVideoMediaTrack` a call renders, with mute, device and facing switches and the host's `VideoProcessor` run on the preview. Given to `join` as `publish`, the tracks are moved rather than shared: the publisher takes them over as it starts publishing, their lobby objects are finished, and the LiveKit backend adopts the device tracks as its own and the processor with its running output, so the join captures nothing and initialises nothing again. Also here, found on the way: a track already on the requested device is left alone (LiveKit would restart it, always on Firefox, which echoes no device id in `getConstraints()`), identical captures in flight are coalesced (React's strict mode mounts twice), and every operation on a processor takes its turn, since a stopped track tears its processor down without waiting for the next track's init. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>	2026-11-04 18:42:59 +01:00
Timo	00463c3ede	Merge pull request #4410 from element-hq/toger5/abb-back-use-behavior-impl Fix useBehavoir reading old value	2026-11-04 18:32:32 +01:00
Timo K.	1aa91bf27c	Add the old useBehavior implementation as reference	2026-11-04 16:27:52 +01:00
renovate[bot]	f930f73c40	Update ghcr.io/element-hq/element-web:develop Docker digest to a798012 (#4406 ) Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>	2026-11-04 02:30:37 +00:00
Johannes Marbach	3914aec53f	Merge pull request #4389 from element-hq/johannes/m_livekit Add support for m.livekit	2026-11-03 17:02:55 +01:00
Johannes Marbach	321340a192	Switch JS SDK to a9ef09fbf2f1644c8663d0aeaf6a921cd16e7b01	2026-11-03 16:31:49 +01:00
Timo	818906eef8	Merge pull request #4404 from element-hq/toger5/fix-storybook-docgen-parse Use a generic instead of a type assertion in useRoomEncryptionSystem	2026-11-03 16:00:58 +01:00
fkwp	60a8fa5464	Merge pull request #4281 from element-hq/spec/background-effects/1-device-menus Hold both device menus at 296px, framed in Safari too	2026-11-03 15:07:53 +01:00
Timo K.	e339098939	Merge branch 'main' into spec/background-effects/1-device-menus	2026-11-03 14:40:13 +01:00
Timo K.andClaude Opus 5.5	1dad38edd2	Use a generic instead of a type assertion in useRoomEncryptionSystem Storybook's react-docgen plugin parses .ts files with Babel's jsx plugin enabled, so the angle-bracket assertion `<EncryptionSystem>useMemo(...)` reads as an opening JSX tag and the Storybook build fails with "Unexpected token". Passing the type as useMemo's generic is equivalent and parses either way. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>	2026-11-03 14:38:42 +01:00
Johannes MarbachandTimo	517edc12ac	Extend comment Co-authored-by: Timo <16718859+toger5@users.noreply.github.com>	2026-11-03 11:44:04 +01:00
Timo K.	dff4e0f194	use compound release.	2026-11-03 10:02:07 +01:00
renovate[bot]	ba27855a43	Update ghcr.io/element-hq/element-web:develop Docker digest to fc21073 (#4402 ) Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>	2026-11-03 03:17:55 +00:00
Valere Fedronic	d46840ce81	Merge pull request #4400 from element-hq/localazy-download-only-app-json Download and upload only app.json from Localazy	2026-11-02 14:42:54 +01:00
ValereandClaude Opus 5.5	c30bb324e3	Download and upload only app.json from Localazy The Localazy project is about to hold the native iOS and Android call screens' strings in a file of their own. Without a condition, the download would copy that file into locales/, and the upload on every push to main would send a stale copy back, overwriting edits made in Localazy. Naming app.json in the upload patterns as well means a copy that arrives another way, such as a local download from an older checkout, is never sent either. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>	2026-11-02 14:10:56 +01:00
Johannes Marbach	b4a632b6d5	Merge pull request #4398 from element-hq/renovate/embedded-package-dependencies Update embedded package dependencies	2026-11-02 08:19:49 +01:00
renovate[bot]	7b6f697c84	Update ghcr.io/element-hq/element-web:develop Docker digest to 84af053 (#4399 ) Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>	2026-11-02 02:17:15 +00:00
renovate[bot]	aa9125f0a0	Update ghcr.io/element-hq/element-web:develop Docker digest to dfd40c1 (#4397 ) Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>	2026-11-01 01:23:14 +00:00
renovate[bot]	e78b4b2e05	Update embedded package dependencies	2026-11-01 01:00:42 +00:00
renovate[bot]	6cffe649e2	Update ghcr.io/element-hq/element-web:develop Docker digest to 60ff051 (#4396 ) Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>	2026-10-31 02:27:20 +00:00
Timo	844051e24c	Merge pull request #4394 from element-hq/toger5/duplicated-js-sdk-bundle Fix duplicate `matrix-js-sdk` in bundle	2026-10-30 17:16:54 +01:00
Timo	a91471b5bc	Merge pull request #4374 from element-hq/toger5/publish-component-npm Add CI to publish EC component to npm	2026-10-30 16:12:53 +01:00
Timo K.	346074ce32	zizmor proposals + review description	2026-10-30 15:38:58 +01:00
Timo K.	b9c10ac533	Add readme for component (npm page)	2026-10-30 15:36:12 +01:00
Timo K.	79bd2890a4	Install the component's dependencies with layered.sh	2026-10-30 15:32:31 +01:00
Timo K.	216bd4b911	Move component publishing into its own workflow	2026-10-30 14:53:23 +01:00
Timo K.	a6764b4e49	Keep the SDK's matrix-js-sdk imports out of the component bundl	2026-10-30 13:54:26 +01:00
renovate[bot]	35ce907e1f	Update ghcr.io/element-hq/element-web:develop Docker digest to 431f742 (#4393 ) Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>	2026-10-30 02:52:45 +00:00
Johannes Marbach	94ee13c639	Add support for m.livekit	2026-10-29 15:40:28 +01:00
Robin	8a987b4d46	Merge pull request #4388 from element-hq/robin/participant-confusion For each member, aggregate tracks from all matching participants	2026-10-29 15:39:45 +01:00
Robin	0fbd77438a	Mark the "all possible transport shapes at once" test as slow	2026-10-29 15:39:22 +01:00
Robin	1dec2b0b1e	Don't log that participants are missing when they're not	2026-10-29 15:39:22 +01:00
Robin	19efe87908	For each member, aggregate tracks from all matching participants Rather than whichever participant has won the race.	2026-10-29 15:39:22 +01:00
Robin	f331c75126	Merge pull request #4382 from element-hq/robin/auth-flow-key Share connections for transports that resolve to same auth flow	2026-10-29 15:39:18 +01:00
Robin	6658dcb677	Remove hard-coded video tile count from end-to-end tests	2026-10-29 15:38:42 +01:00
Robin	6a7f2ca603	Share connections for transports that resolve to same auth flow By keying the connections by the transport's resolved auth flow. This is important because connecting to the same SFU twice with the same participant ID will cause a 'duplicate participant ID' error that stops one of the connections.	2026-10-29 15:38:42 +01:00
Robin	b8c7f4ebfe	Merge pull request #4381 from element-hq/robin/always-openid Always use OpenID auth flow if available	2026-10-29 15:38:38 +01:00
Timo K.	287f711d07	Update publish-embedded-packages.yaml	2026-10-29 15:19:32 +01:00
Timo K.	8ef1dee256	bump compound web	2026-10-29 13:11:44 +01:00
Johannes Marbach	26b09adc64	Merge pull request #4366 from junkerderprovinz/junkerderprovinz/firefox-websocket-prime Retry the SFU connection once in Firefox when the WebSocket fails	2026-10-29 08:27:45 +01:00
Johannes Marbach	b7655417d7	Move comment inline	2026-10-29 08:05:07 +01:00
renovate[bot]	2dd000bab0	Update ghcr.io/element-hq/element-web:develop Docker digest to f4e3c42 (#4385 ) Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>	2026-10-29 03:19:17 +00:00
junkerderprovinz	d6e3fefe82	Retry the join in Firefox instead of priming the WebSocket The second connection only happens when the first one actually failed on the WebSocket. connect() rejects after its socket has failed and the engine is closed, so the retry never overlaps the failing socket.	2026-10-28 23:44:19 +01:00
Timo K.	38ef1add48	use compound web sticky patch	2026-10-28 19:29:08 +01:00
Robin	b27c11c381	Always use OpenID auth flow if available This removes the notion of an auth flow fallback for now. We will no longer try the CS API when authenticating with transports that include both a `url` and `livekit_service_url`.	2026-10-28 19:16:32 +01:00
Timo K.	cffdb58521	rop the device list's custom fade under the mete	2026-10-28 16:33:31 +01:00
Timo K.	2abe7ea02f	better docs for the sub test trick	2026-10-28 16:27:38 +01:00
Johannes Marbach	b7bc218b19	Merge pull request #4367 from RaphaelFakhri/RaphaelFakhri/shared-key-storage-key Read and write the room shared key under its single-prefixed storage key	2026-10-28 16:21:11 +01:00
Timo K.	17caded88b	clean up css calc in ts code	2026-10-28 16:11:49 +01:00
Raphael Fakhri	85424f76b1	Ignore the URL password when the parameters are for another room	2026-10-28 14:33:07 +00:00
Timo K.	c713b13994	review: audioMeter instead of `iconsAndLabels === "audio"`	2026-10-28 15:17:44 +01:00
Robin	c233ac6e70	Improve names of transport shape end-to-end tests	2026-10-28 14:51:27 +01:00
Timo K.	2e6c7d1419	add agpl to component package	2026-10-28 13:57:35 +01:00
renovate[bot]	6793a4b46e	Update ghcr.io/element-hq/element-web:develop Docker digest to ee8ce55 (#4380 ) Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>	2026-10-28 02:32:09 +00:00
Robin	619f5ac3a2	Merge pull request #4375 from element-hq/robin/stats-crash Fix crash when joining call with connection stats enabled	2026-10-27 18:08:31 +01:00
Robin	5780597b83	Fix crash when joining call with connection stats enabled As demonstrated by the test. This crashed with "Behavior failed to synchronously emit an initial value."	2026-10-27 16:17:58 +01:00
Timo K.	f2976be103	Add CI to publish to npm	2026-10-27 16:05:44 +01:00
Robin	76da59be40	Merge pull request #4301 from element-hq/floating-tile Make drag & drop of floating tiles less janky	2026-10-27 12:16:12 +01:00
RaphaelFakhri	dc1459e45e	Prefer the stored shared key when the parameters are for another room keyForRoom returned the password from the parameters even when they were for a different room, and useRoomSharedKey then saved it for this room. Use the stored key first in that case, so another room's password can't replace it.	2026-10-26 21:13:23 +00:00
Junker der Provinz	dfff8be38e	Wait for the primed WebSocket to close before connecting	2026-10-26 18:21:19 +01:00
fkwpandClaude Opus 5.5	9e6f2e89a8	Size and scroll the device menus with Compound's menu - Compound 10.3.0 bounds a menu by the space it has and scrolls what doesn't fit, within a boundary the app passes. The menus pass the call area, 16px in from its sides, rather than measuring its width. - The 296px width is the menu's own style. Compound gives that style only to the dropdown, so menuIsDrawer, which copied its phone rule, goes. - Compound draws the menu's frame over its content, so nothing that scrolls can hide it in Safari: the list, headings and meter no longer keep a border width clear of it, and the checks that they did go. - The device list is Compound's scroll area, so it fades out at the foot with Compound's chevron while there is more below. - The microphone menu's meter sticks at that foot, with rows scrolling under it as before, so the list has no fade above it: Compound's is a mask fixed to the list's edge, while a bounce at the top carries the meter with the rows. The band under the meter is filled, or rows would show there. The edge fades from where the chevron starts, so a bounce fades the meter out before it reaches the chevron. A row reached by keyboard stays above the meter. - The list's height is still its share of the call. - The component harness leaves the host's stylesheets unscoped, Compound's among them, as a host does: scoped, they never reached the menu, which is portalled out of Element Call's root. - Its specs check only Element Call's own document styles on the host page, and find the device list within Compound's scroll area. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>	2026-10-26 15:48:52 +01:00
fkwpandClaude Opus 5.5	7a48b09c4c	Hold both device menus at 296px, framed in Safari too - The camera and microphone menus were as wide as their longest device name, so a long one widened the menu over more of the call: 340px for a long speaker name. Both are now 296px, as design sets them, and a long name wraps. - Narrower only where the call area is, so the menu still fits inside it: 268px in a 300px call. Taken from the observation of the call area that already bounds the list's height. - Held only for the dropdown. On Android and iOS Compound renders the menu as a drawer as wide as the screen; menuIsDrawer follows its rule. - Once the list is long enough to scroll, Safari paints it above the outline the menu is framed with, and the frame vanished down both sides of it: 384px of it on the many-devices microphone menu, in WebKit. The list now keeps a border width clear of the frame, so the headings and the meter inside it no longer need their own. - Guarded with a long speaker name, which fails at 340px on main's sizing; a unit test run as a phone, which fails with the width held there; and the many-devices story's inset, which fails on the old stylesheet, since the stories run in Chromium, which never showed the Safari bug. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>	2026-10-26 15:48:07 +01:00
Robin	ed6a0e1341	Merge pull request #4371 from element-hq/ellipsize-title Ellipsise app bar text on mobile	2026-10-26 13:45:06 +01:00
renovate[bot]andJohannes Marbach	90ccf62d5c	Update ghcr.io/element-hq/element-web:develop Docker digest to c9ffe3e (#4356 ) * Update ghcr.io/element-hq/element-web:develop Docker digest to 79e47d8 * Adapt to new recovery popup button title --------- Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com> Co-authored-by: Johannes Marbach <n0-0ne+github@mailbox.org>	2026-10-26 12:44:39 +00:00
Robin	dde07f6d54	Ellipsise app bar text on mobile We already had text-overflow: ellipsis set on the title and subtitle elements of the app bar, but due to an annoying quirk of place-items: center, this had no effect. place-items: center stretch seems to give the text elements the right size constraints.	2026-10-26 13:25:13 +01:00
Raphael Fakhri	bda7b86c39	Read and write the room shared key under its single-prefixed storage key	2026-10-22 12:24:39 +00:00
Junker der ProvinzandMarc	ee507ab3ac	Prime the SFU WebSocket in Firefox before connecting Behind a proxy, Firefox fails the first WebSocket it opens to a host, so the first join fails. The livekit-client in the report turned this into an insufficient capacity error; current versions report a generic connection error. Opening a throwaway WebSocket first lets the real connection through. Co-authored-by: Marc <10048869+MarcWadai@users.noreply.github.com>	2026-10-22 11:28:11 +02:00