diff --git a/src/state/CallViewModel/CallViewModel.ts b/src/state/CallViewModel/CallViewModel.ts
index 76675c824..ae6a54697 100644
--- a/src/state/CallViewModel/CallViewModel.ts
+++ b/src/state/CallViewModel/CallViewModel.ts
@@ -93,17 +93,16 @@ import { type HostBridge, nullHostBridge } from "../../HostBridge";
 import {
   layoutShallowEquals,
   type Alignment,
-  type GridLayoutMedia,
   type Layout,
   type LayoutMedia,
-  type OneOnOneDesktopLayoutMedia,
-  type OneOnOneMobileLayoutMedia,
-  type SpotlightExpandedLayoutMedia,
-  type SpotlightLandscapeLayoutMedia,
-  type SpotlightPortraitLayoutMedia,
   type WindowMode,
 } from "../layout-types.ts";
-import { chooseSpotlightSpeaker, computeSpotlight } from "../layoutMedia.ts";
+import {
+  chooseSpotlightSpeaker,
+  computeLayoutMedia,
+  computeSpotlight,
+  type OneOnOneMedia,
+} from "../layoutMedia.ts";
 import { ElementCallError, UnknownCallError } from "../../utils/errors.ts";
 import { type Epoch, type ObservableScope } from "../ObservableScope.ts";
 import { createHomeserverConnected$ } from "./localMember/HomeserverConnected.ts";
@@ -147,7 +146,6 @@ import {
 import { Publisher } from "./localMember/Publisher.ts";
 import { type Connection } from "./remoteMembers/Connection.ts";
 import {
-  type LayoutMode,
   type LayoutSwitchViewModel,
   createLayoutSwitchViewModel,
 } from "../LayoutSwitchViewModel.ts";
@@ -265,10 +263,6 @@ export function callViewModelOptionsFromParams(
 export const MAX_PARTICIPANT_COUNT_FOR_SOUND = 8;
 export const THROTTLE_SOUND_EFFECT_MS = 500;
 
-// This is the number of participants that we think constitutes a "small" call
-// on mobile. No spotlight tile should be shown below this threshold.
-const smallMobileCallThreshold = 3;
-
 // How long the footer should be shown for when hovering over or interacting
 // with the interface
 const showFooterMs = 4000;
@@ -1773,133 +1767,3 @@ function getE2eeKeyProvider(
     return keyProvider;
   }
 }
-
-interface OneOnOneMedia {
-  local: LocalUserMediaViewModel;
-  remote: UserMediaViewModel | RingingMediaViewModel;
-}
-
-interface LayoutMediaInputs {
-  windowMode: WindowMode;
-  /** The layout chosen with the layout switch. */
-  layoutMode: LayoutMode;
-  spotlightExpanded: boolean;
-  /** Set when the call qualifies for a one-on-one layout. */
-  oneOnOne: OneOnOneMedia | null;
-  localVideoEnabled: boolean;
-  spotlight: MediaViewModel[];
-  grid: UserMediaViewModel[];
-  pip: UserMediaViewModel | undefined;
-  desktop: boolean;
-}
-
-/**
- * Decides which layout to use and which media goes where in it.
- */
-function computeLayoutMedia({
-  windowMode,
-  layoutMode,
-  spotlightExpanded,
-  oneOnOne,
-  localVideoEnabled,
-  spotlight,
-  grid,
-  pip,
-  desktop,
-}: LayoutMediaInputs): LayoutMedia {
-  switch (windowMode) {
-    case "normal":
-      if (layoutMode === "grid")
-        return oneOnOne === null
-          ? gridLayoutMedia(spotlight, grid)
-          : oneOnOneDesktopLayoutMedia(oneOnOne);
-      return spotlightExpanded
-        ? spotlightExpandedLayoutMedia(false, spotlight, pip)
-        : spotlightLandscapeLayoutMedia(false, spotlight, grid);
-    case "narrow":
-      if (oneOnOne !== null)
-        return oneOnOneMobileLayoutMedia(oneOnOne, localVideoEnabled);
-      return grid.length > smallMobileCallThreshold || hasScreenShare(spotlight)
-        ? spotlightPortraitLayoutMedia(spotlight, grid)
-        : gridLayoutMedia(spotlight, grid);
-    case "flat":
-      if (oneOnOne !== null)
-        return oneOnOneMobileLayoutMedia(oneOnOne, localVideoEnabled);
-      // Yes, grid mode actually gets you a "spotlight" layout in this window
-      // mode.
-      return layoutMode === "grid"
-        ? spotlightLandscapeLayoutMedia(true, spotlight, grid)
-        : spotlightExpandedLayoutMedia(true, spotlight, pip);
-    case "pip":
-      return { type: "pip", edgeToEdge: !desktop, spotlight };
-  }
-}
-
-function hasScreenShare(spotlight: MediaViewModel[]): boolean {
-  return spotlight.some((vm) => vm.type === "screen share");
-}
-
-function gridLayoutMedia(
-  spotlight: MediaViewModel[],
-  grid: UserMediaViewModel[],
-): GridLayoutMedia {
-  return {
-    type: "grid",
-    edgeToEdge: false,
-    spotlight: hasScreenShare(spotlight) ? spotlight : undefined,
-    grid,
-  };
-}
-
-function oneOnOneDesktopLayoutMedia(
-  media: OneOnOneMedia,
-): OneOnOneDesktopLayoutMedia {
-  return media.remote.type === "ringing"
-    ? {
-        type: "one-on-one-desktop",
-        edgeToEdge: false,
-        spotlight: media.local,
-        pip: media.remote,
-      }
-    : {
-        type: "one-on-one-desktop",
-        edgeToEdge: false,
-        spotlight: media.remote,
-        pip: media.local,
-      };
-}
-
-function spotlightExpandedLayoutMedia(
-  edgeToEdge: boolean,
-  spotlight: MediaViewModel[],
-  pip: UserMediaViewModel | undefined,
-): SpotlightExpandedLayoutMedia {
-  return { type: "spotlight-expanded", edgeToEdge, spotlight, pip };
-}
-
-function spotlightLandscapeLayoutMedia(
-  edgeToEdge: boolean,
-  spotlight: MediaViewModel[],
-  grid: UserMediaViewModel[],
-): SpotlightLandscapeLayoutMedia {
-  return { type: "spotlight-landscape", edgeToEdge, spotlight, grid };
-}
-
-function oneOnOneMobileLayoutMedia(
-  media: OneOnOneMedia,
-  localVideoEnabled: boolean,
-): OneOnOneMobileLayoutMedia {
-  return {
-    type: "one-on-one-mobile",
-    edgeToEdge: true,
-    spotlight: media.remote,
-    pip: localVideoEnabled ? media.local : undefined,
-  };
-}
-
-function spotlightPortraitLayoutMedia(
-  spotlight: MediaViewModel[],
-  grid: UserMediaViewModel[],
-): SpotlightPortraitLayoutMedia {
-  return { type: "spotlight-portrait", edgeToEdge: false, spotlight, grid };
-}
diff --git a/src/state/layoutMedia.test.ts b/src/state/layoutMedia.test.ts
index 8e164cc9a..afa159877 100644
--- a/src/state/layoutMedia.test.ts
+++ b/src/state/layoutMedia.test.ts
@@ -7,7 +7,12 @@ Please see LICENSE in the repository root for full details.
 
 import { describe, expect, it } from "vitest";
 
-import { chooseSpotlightSpeaker, computeSpotlight } from "./layoutMedia";
+import {
+  chooseSpotlightSpeaker,
+  computeLayoutMedia,
+  computeSpotlight,
+  type LayoutMediaInputs,
+} from "./layoutMedia";
 import { type LocalUserMediaViewModel } from "./media/LocalUserMediaViewModel";
 import { type RemoteUserMediaViewModel } from "./media/RemoteUserMediaViewModel";
 import { type RingingMediaViewModel } from "./media/RingingMediaViewModel";
@@ -110,3 +115,106 @@ describe("computeSpotlight", () => {
     ).toEqual({ spotlight: [local], pip: undefined });
   });
 });
+
+describe("computeLayoutMedia", () => {
+  const base: LayoutMediaInputs = {
+    windowMode: "normal",
+    layoutMode: "grid",
+    spotlightExpanded: false,
+    oneOnOne: null,
+    localVideoEnabled: true,
+    spotlight: [alice],
+    grid: [local, alice, bob],
+    pip: local,
+    desktop: false,
+  };
+  const layout = (
+    overrides: Partial<LayoutMediaInputs>,
+  ): ReturnType<typeof computeLayoutMedia> =>
+    computeLayoutMedia({ ...base, ...overrides });
+
+  it("uses a plain grid unless a screen share needs the spotlight", () => {
+    expect(layout({})).toEqual({
+      type: "grid",
+      edgeToEdge: false,
+      spotlight: undefined,
+      grid: base.grid,
+    });
+    expect(layout({ spotlight: [screenShare] }).spotlight).toEqual([
+      screenShare,
+    ]);
+  });
+
+  it("switches between landscape and expanded spotlight", () => {
+    expect(layout({ layoutMode: "spotlight" })).toMatchObject({
+      type: "spotlight-landscape",
+      edgeToEdge: false,
+    });
+    expect(
+      layout({ layoutMode: "spotlight", spotlightExpanded: true }),
+    ).toEqual({
+      type: "spotlight-expanded",
+      edgeToEdge: false,
+      spotlight: [alice],
+      pip: local,
+    });
+  });
+
+  it("puts the remote user in the desktop one-on-one spotlight, or the local user when ringing", () => {
+    expect(layout({ oneOnOne: { local, remote: alice } })).toEqual({
+      type: "one-on-one-desktop",
+      edgeToEdge: false,
+      spotlight: alice,
+      pip: local,
+    });
+    expect(layout({ oneOnOne: { local, remote: ringing } })).toMatchObject({
+      spotlight: local,
+      pip: ringing,
+    });
+  });
+
+  it("uses a mobile one-on-one layout in narrow and flat windows, hiding the PiP without video", () => {
+    const oneOnOne = { local, remote: alice };
+    expect(layout({ windowMode: "narrow", oneOnOne })).toEqual({
+      type: "one-on-one-mobile",
+      edgeToEdge: true,
+      spotlight: alice,
+      pip: local,
+    });
+    expect(
+      layout({ windowMode: "flat", oneOnOne, localVideoEnabled: false }),
+    ).toMatchObject({ type: "one-on-one-mobile", pip: undefined });
+  });
+
+  it("uses a portrait spotlight in narrow windows for big calls or screen shares", () => {
+    expect(layout({ windowMode: "narrow" }).type).toBe("grid");
+    expect(
+      layout({ windowMode: "narrow", grid: [local, alice, bob, carol] }).type,
+    ).toBe("spotlight-portrait");
+    expect(
+      layout({ windowMode: "narrow", spotlight: [screenShare] }).type,
+    ).toBe("spotlight-portrait");
+  });
+
+  it("uses edge-to-edge spotlight layouts in flat windows", () => {
+    expect(layout({ windowMode: "flat" })).toMatchObject({
+      type: "spotlight-landscape",
+      edgeToEdge: true,
+    });
+    expect(
+      layout({ windowMode: "flat", layoutMode: "spotlight" }),
+    ).toMatchObject({
+      type: "spotlight-expanded",
+      edgeToEdge: true,
+    });
+  });
+
+  it("uses the PiP layout, edge to edge except on desktop", () => {
+    expect(layout({ windowMode: "pip" })).toEqual({
+      type: "pip",
+      edgeToEdge: true,
+      spotlight: [alice],
+    });
+    expect(layout({ windowMode: "pip", desktop: true }).edgeToEdge).toBe(false);
+  });
+});
diff --git a/src/state/layoutMedia.ts b/src/state/layoutMedia.ts
index 64365b3a8..56dec9979 100644
--- a/src/state/layoutMedia.ts
+++ b/src/state/layoutMedia.ts
@@ -5,11 +5,29 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
+import { type LayoutMode } from "./LayoutSwitchViewModel.ts";
+import {
+  type GridLayoutMedia,
+  type LayoutMedia,
+  type OneOnOneDesktopLayoutMedia,
+  type OneOnOneMobileLayoutMedia,
+  type SpotlightExpandedLayoutMedia,
+  type SpotlightLandscapeLayoutMedia,
+  type SpotlightPortraitLayoutMedia,
+  type WindowMode,
+} from "./layout-types.ts";
+import { type LocalUserMediaViewModel } from "./media/LocalUserMediaViewModel.ts";
 import { type MediaViewModel } from "./media/MediaViewModel.ts";
 import { type RingingMediaViewModel } from "./media/RingingMediaViewModel.ts";
 import { type ScreenShareViewModel } from "./media/ScreenShareViewModel.ts";
 import { type UserMediaViewModel } from "./media/UserMediaViewModel.ts";
 
+/**
+ * This is the number of participants that we think constitutes a "small" call
+ * on mobile. No spotlight tile should be shown below this threshold.
+ */
+const smallMobileCallThreshold = 3;
+
 /**
  * Picks who to spotlight based on who is speaking, preferring the previous
  * pick so that the spotlight doesn't flip eagerly between speakers.
@@ -66,3 +84,133 @@ export function computeSpotlight({
     pip: localPip === speaker ? undefined : localPip,
   };
 }
+
+export interface OneOnOneMedia {
+  local: LocalUserMediaViewModel;
+  remote: UserMediaViewModel | RingingMediaViewModel;
+}
+
+export interface LayoutMediaInputs {
+  windowMode: WindowMode;
+  /** The layout chosen with the layout switch. */
+  layoutMode: LayoutMode;
+  spotlightExpanded: boolean;
+  /** Set when the call qualifies for a one-on-one layout. */
+  oneOnOne: OneOnOneMedia | null;
+  localVideoEnabled: boolean;
+  spotlight: MediaViewModel[];
+  grid: UserMediaViewModel[];
+  pip: UserMediaViewModel | undefined;
+  desktop: boolean;
+}
+
+/**
+ * Decides which layout to use and which media goes where in it.
+ */
+export function computeLayoutMedia({
+  windowMode,
+  layoutMode,
+  spotlightExpanded,
+  oneOnOne,
+  localVideoEnabled,
+  spotlight,
+  grid,
+  pip,
+  desktop,
+}: LayoutMediaInputs): LayoutMedia {
+  switch (windowMode) {
+    case "normal":
+      if (layoutMode === "grid")
+        return oneOnOne === null
+          ? gridLayoutMedia(spotlight, grid)
+          : oneOnOneDesktopLayoutMedia(oneOnOne);
+      return spotlightExpanded
+        ? spotlightExpandedLayoutMedia(false, spotlight, pip)
+        : spotlightLandscapeLayoutMedia(false, spotlight, grid);
+    case "narrow":
+      if (oneOnOne !== null)
+        return oneOnOneMobileLayoutMedia(oneOnOne, localVideoEnabled);
+      return grid.length > smallMobileCallThreshold || hasScreenShare(spotlight)
+        ? spotlightPortraitLayoutMedia(spotlight, grid)
+        : gridLayoutMedia(spotlight, grid);
+    case "flat":
+      if (oneOnOne !== null)
+        return oneOnOneMobileLayoutMedia(oneOnOne, localVideoEnabled);
+      // Yes, grid mode actually gets you a "spotlight" layout in this window
+      // mode.
+      return layoutMode === "grid"
+        ? spotlightLandscapeLayoutMedia(true, spotlight, grid)
+        : spotlightExpandedLayoutMedia(true, spotlight, pip);
+    case "pip":
+      return { type: "pip", edgeToEdge: !desktop, spotlight };
+  }
+}
+
+function hasScreenShare(spotlight: MediaViewModel[]): boolean {
+  return spotlight.some((vm) => vm.type === "screen share");
+}
+
+function gridLayoutMedia(
+  spotlight: MediaViewModel[],
+  grid: UserMediaViewModel[],
+): GridLayoutMedia {
+  return {
+    type: "grid",
+    edgeToEdge: false,
+    spotlight: hasScreenShare(spotlight) ? spotlight : undefined,
+    grid,
+  };
+}
+
+function oneOnOneDesktopLayoutMedia(
+  media: OneOnOneMedia,
+): OneOnOneDesktopLayoutMedia {
+  return media.remote.type === "ringing"
+    ? {
+        type: "one-on-one-desktop",
+        edgeToEdge: false,
+        spotlight: media.local,
+        pip: media.remote,
+      }
+    : {
+        type: "one-on-one-desktop",
+        edgeToEdge: false,
+        spotlight: media.remote,
+        pip: media.local,
+      };
+}
+
+function spotlightExpandedLayoutMedia(
+  edgeToEdge: boolean,
+  spotlight: MediaViewModel[],
+  pip: UserMediaViewModel | undefined,
+): SpotlightExpandedLayoutMedia {
+  return { type: "spotlight-expanded", edgeToEdge, spotlight, pip };
+}
+
+function spotlightLandscapeLayoutMedia(
+  edgeToEdge: boolean,
+  spotlight: MediaViewModel[],
+  grid: UserMediaViewModel[],
+): SpotlightLandscapeLayoutMedia {
+  return { type: "spotlight-landscape", edgeToEdge, spotlight, grid };
+}
+
+function oneOnOneMobileLayoutMedia(
+  media: OneOnOneMedia,
+  localVideoEnabled: boolean,
+): OneOnOneMobileLayoutMedia {
+  return {
+    type: "one-on-one-mobile",
+    edgeToEdge: true,
+    spotlight: media.remote,
+    pip: localVideoEnabled ? media.local : undefined,
+  };
+}
+
+function spotlightPortraitLayoutMedia(
+  spotlight: MediaViewModel[],
+  grid: UserMediaViewModel[],
+): SpotlightPortraitLayoutMedia {
+  return { type: "spotlight-portrait", edgeToEdge: false, spotlight, grid };
+}