diff --git a/packages/react-cosmos-core/src/renderer/rendererConnect.ts b/packages/react-cosmos-core/src/renderer/rendererConnect.ts
index 20585da931..1ced1e1df2 100644
--- a/packages/react-cosmos-core/src/renderer/rendererConnect.ts
+++ b/packages/react-cosmos-core/src/renderer/rendererConnect.ts
@@ -1,9 +1,5 @@
 import { FixtureState } from '../fixtureState/types.js';
-import {
-  FixtureId,
-  FixtureList,
-  FixtureListItem,
-} from '../userModules/fixtureTypes.js';
+import { FixtureId, FixtureList } from '../userModules/fixtureTypes.js';
 
 // FYI: Renderer ids are self assigned in remote environments, so uniqueness
 // cannot be established by consensus
@@ -77,15 +73,6 @@ export type FixtureListUpdateResponse = {
   };
 };
 
-export type FixtureListItemUpdateResponse = {
-  type: 'fixtureListItemUpdate';
-  payload: {
-    rendererId: RendererId;
-    fixturePath: string;
-    fixtureItem: FixtureListItem;
-  };
-};
-
 // Caused by an organic state change inside the renderer. Also dispatched
 // after a fixtureSelect request, when rendering stateful components, as their
 // initial state is read.
@@ -112,7 +99,6 @@ export type RendererResponse =
   | RendererReadyResponse
   | RendererErrorResponse
   | FixtureListUpdateResponse
-  | FixtureListItemUpdateResponse
   | FixtureStateChangeResponse
   | PlaygroundCommandResponse;
 
diff --git a/packages/react-cosmos-dom/src/DomRendererProvider.tsx b/packages/react-cosmos-dom/src/DomRendererProvider.tsx
index d0728e55e9..e81d80ab74 100644
--- a/packages/react-cosmos-dom/src/DomRendererProvider.tsx
+++ b/packages/react-cosmos-dom/src/DomRendererProvider.tsx
@@ -15,7 +15,7 @@ import {
 } from 'react-cosmos-renderer';
 import {
   RendererContext,
-  RendererContextValue,
+  RendererProvider,
 } from 'react-cosmos-renderer/client';
 import { getDomRendererId } from './domRendererId.js';
 
@@ -31,33 +31,48 @@ export function DomRendererProvider({
   searchParams,
   setSearchParams,
 }: Props) {
-  const value = React.useMemo<RendererContextValue>(() => {
-    return {
-      rendererId: getDomRendererId(),
-      rendererConnect: createDomRendererConnect(rendererConfig.playgroundUrl),
-      searchParams: decodeRendererSearchParams(searchParams),
-      setSearchParams: (nextParams: RendererSearchParams) => {
-        // Implementing setSearchParams is optional. It is required for server
-        // fixture loaders that cannot listen to client-side 'selectFixture'
-        // requests from the Cosmos UI.
-        if (setSearchParams) {
-          setSearchParams(encodeRendererSearchParams(nextParams));
-        }
-      },
-      reloadRenderer: () => {
-        window.location.reload();
-      },
-    };
-  }, [setSearchParams, rendererConfig, searchParams]);
+  const rendererId = React.useMemo(() => getDomRendererId(), []);
+
+  const rendererConnect = React.useMemo(
+    () => createDomRendererConnect(rendererConfig.playgroundUrl),
+    [rendererConfig.playgroundUrl]
+  );
+
+  const decodedParams = React.useMemo(
+    () => decodeRendererSearchParams(searchParams),
+    [searchParams]
+  );
+
+  const setDecodedParams = React.useCallback(
+    (nextParams: RendererSearchParams) => {
+      // Implementing setSearchParams is optional. It is required for server
+      // fixture loaders that cannot listen to client-side 'selectFixture'
+      // requests from the Cosmos UI.
+      if (setSearchParams) {
+        setSearchParams(encodeRendererSearchParams(nextParams));
+      }
+    },
+    [setSearchParams]
+  );
 
   return (
-    <RendererContext.Provider value={value}>
+    <RendererProvider
+      rendererId={rendererId}
+      rendererConnect={rendererConnect}
+      searchParams={decodedParams}
+      setSearchParams={setDecodedParams}
+      reloadRenderer={reloadRenderer}
+    >
       {children}
       {typeof window !== 'undefined' && <GlobalErrorHandler />}
-    </RendererContext.Provider>
+    </RendererProvider>
   );
 }
 
+function reloadRenderer() {
+  window.location.reload();
+}
+
 function GlobalErrorHandler() {
   const { rendererId, rendererConnect } = React.useContext(RendererContext);
 
diff --git a/packages/react-cosmos-native/src/NativeRendererProvider.tsx b/packages/react-cosmos-native/src/NativeRendererProvider.tsx
index cfb960664f..2f413c780c 100644
--- a/packages/react-cosmos-native/src/NativeRendererProvider.tsx
+++ b/packages/react-cosmos-native/src/NativeRendererProvider.tsx
@@ -1,10 +1,7 @@
 import React from 'react';
 import { FixtureId, RendererConfig } from 'react-cosmos-core';
 import { createWebSocketsConnect } from 'react-cosmos-renderer';
-import {
-  RendererContext,
-  RendererContextValue,
-} from 'react-cosmos-renderer/client';
+import { RendererProvider } from 'react-cosmos-renderer/client';
 import { DevSettings } from 'react-native';
 import { getSocketUrl } from './getSocketUrl.js';
 
@@ -18,23 +15,32 @@ export function NativeRendererProvider({
   rendererConfig,
   initialFixtureId,
 }: Props) {
-  const value = React.useMemo<RendererContextValue>(() => {
-    const socketUrl = getSocketUrl(rendererConfig.playgroundUrl);
-    return {
-      // TODO: Generate unique ID per device
-      rendererId: 'native-renderer',
-      rendererConnect: createWebSocketsConnect(socketUrl),
-      searchParams: { fixtureId: initialFixtureId },
-      setSearchParams: () => {},
-      reloadRenderer: () => {
-        DevSettings.reload();
-      },
-    };
-  }, [initialFixtureId, rendererConfig]);
+  const rendererConnect = React.useMemo(
+    () => createWebSocketsConnect(getSocketUrl(rendererConfig.playgroundUrl)),
+    [rendererConfig.playgroundUrl]
+  );
+
+  const searchParams = React.useMemo(
+    () => ({ fixtureId: initialFixtureId }),
+    [initialFixtureId]
+  );
 
   return (
-    <RendererContext.Provider value={value}>
+    <RendererProvider
+      // TODO: Generate unique ID per device
+      rendererId="native-renderer"
+      rendererConnect={rendererConnect}
+      searchParams={searchParams}
+      setSearchParams={noop}
+      reloadRenderer={reloadRenderer}
+    >
       {children}
-    </RendererContext.Provider>
+    </RendererProvider>
   );
 }
+
+function reloadRenderer() {
+  DevSettings.reload();
+}
+
+function noop() {}
diff --git a/packages/react-cosmos-renderer/src/__tests__/fixtureInitialSelectLazy.ts b/packages/react-cosmos-renderer/src/__tests__/fixtureInitialSelectLazy.ts
index 0f6c7e4fb4..41de0e4157 100644
--- a/packages/react-cosmos-renderer/src/__tests__/fixtureInitialSelectLazy.ts
+++ b/packages/react-cosmos-renderer/src/__tests__/fixtureInitialSelectLazy.ts
@@ -36,14 +36,14 @@ testRenderer(
 );
 
 testRenderer(
-  'posts lazy fixture list item update on initially selected fixture',
+  'posts lazy fixture list with item names on initially selected fixture',
   {
     rendererId,
     searchParams: { fixtureId: { path: 'first' } },
     fixtures,
     lazy: true,
   },
-  async ({ rendererReady, fixtureListUpdate, fixtureListItemUpdate }) => {
+  async ({ rendererReady, fixtureListUpdate }) => {
     await rendererReady({
       rendererId,
       selectedFixtureId: { path: 'first' },
@@ -51,14 +51,9 @@ testRenderer(
     await fixtureListUpdate({
       rendererId,
       fixtures: {
-        first: { type: 'single' },
+        first: { type: 'multi', fixtureNames: ['one'] },
         second: { type: 'single' },
       },
     });
-    await fixtureListItemUpdate({
-      rendererId,
-      fixturePath: 'first',
-      fixtureItem: { type: 'multi', fixtureNames: ['one'] },
-    });
   }
 );
diff --git a/packages/react-cosmos-renderer/src/__tests__/fixtureListMulti.ts b/packages/react-cosmos-renderer/src/__tests__/fixtureListMulti.ts
index 26d52e3149..b2f7351a51 100644
--- a/packages/react-cosmos-renderer/src/__tests__/fixtureListMulti.ts
+++ b/packages/react-cosmos-renderer/src/__tests__/fixtureListMulti.ts
@@ -9,7 +9,7 @@ const fixtures = wrapDefaultExport({
 });
 
 testRenderer(
-  'posts fixture list with names',
+  'posts fixture list with item names',
   { rendererId, fixtures },
   async ({ fixtureListUpdate }) => {
     await fixtureListUpdate({
diff --git a/packages/react-cosmos-renderer/src/__tests__/fixtureListMultiLazy.ts b/packages/react-cosmos-renderer/src/__tests__/fixtureListMultiLazy.ts
index fdc8f151d0..319a4b070e 100644
--- a/packages/react-cosmos-renderer/src/__tests__/fixtureListMultiLazy.ts
+++ b/packages/react-cosmos-renderer/src/__tests__/fixtureListMultiLazy.ts
@@ -9,9 +9,9 @@ const fixtures = wrapDefaultExport({
 });
 
 testRenderer(
-  'posts lazy fixture list item update on fixture select',
+  'posts lazy fixture list with item names on fixture select',
   { rendererId, fixtures, lazy: true },
-  async ({ selectFixture, fixtureListUpdate, fixtureListItemUpdate }) => {
+  async ({ selectFixture, fixtureListUpdate }) => {
     await fixtureListUpdate({
       rendererId,
       fixtures: {
@@ -24,10 +24,12 @@ testRenderer(
       fixtureId: { path: 'first' },
       fixtureState: {},
     });
-    await fixtureListItemUpdate({
+    await fixtureListUpdate({
       rendererId,
-      fixturePath: 'first',
-      fixtureItem: { type: 'multi', fixtureNames: ['a', 'b', 'c'] },
+      fixtures: {
+        first: { type: 'multi', fixtureNames: ['a', 'b', 'c'] },
+        second: { type: 'single' },
+      },
     });
   }
 );
diff --git a/packages/react-cosmos-renderer/src/client.ts b/packages/react-cosmos-renderer/src/client.ts
index 8843238428..5cbc672f58 100644
--- a/packages/react-cosmos-renderer/src/client.ts
+++ b/packages/react-cosmos-renderer/src/client.ts
@@ -5,3 +5,4 @@ export * from './fixture/useSelect/index.js';
 export * from './fixture/useValue/index.js';
 export * from './fixtureLoaders/ClientFixtureLoader.js';
 export * from './rendererConnect/RendererContext.js';
+export * from './rendererConnect/RendererProvider.js';
diff --git a/packages/react-cosmos-renderer/src/fixtureLoaders/RendererSync.tsx b/packages/react-cosmos-renderer/src/fixtureLoaders/RendererSync.tsx
index f0b4426f2a..f05d79e7b4 100644
--- a/packages/react-cosmos-renderer/src/fixtureLoaders/RendererSync.tsx
+++ b/packages/react-cosmos-renderer/src/fixtureLoaders/RendererSync.tsx
@@ -8,8 +8,13 @@ type Props = {
   fixtures: FixtureList;
 };
 export function RendererSync({ children, fixtures }: Props) {
-  const { searchParams, rendererId, rendererConnect, reloadRenderer } =
-    React.useContext(RendererContext);
+  const {
+    searchParams,
+    rendererId,
+    rendererConnect,
+    reloadRenderer,
+    lazyItems,
+  } = React.useContext(RendererContext);
 
   const { fixtureId: selectedFixtureId } = searchParams;
 
@@ -32,10 +37,10 @@ export function RendererSync({ children, fixtures }: Props) {
       type: 'fixtureListUpdate',
       payload: {
         rendererId,
-        fixtures,
+        fixtures: { ...fixtures, ...lazyItems },
       },
     });
-  }, [fixtures, rendererConnect, rendererId]);
+  }, [fixtures, lazyItems, rendererConnect, rendererId]);
 
   React.useEffect(
     () =>
diff --git a/packages/react-cosmos-renderer/src/fixtureModule/FixtureProvider.tsx b/packages/react-cosmos-renderer/src/fixtureModule/FixtureProvider.tsx
index 82ca0512f7..fe8130f0a7 100644
--- a/packages/react-cosmos-renderer/src/fixtureModule/FixtureProvider.tsx
+++ b/packages/react-cosmos-renderer/src/fixtureModule/FixtureProvider.tsx
@@ -29,29 +29,21 @@ export function FixtureProvider(props: Props) {
     syncedFixtureState: {},
   });
 
-  const { rendererId, rendererConnect } = React.useContext(RendererContext);
+  const { rendererId, rendererConnect, setLazyItems } =
+    React.useContext(RendererContext);
 
   React.useEffect(() => {
     // Only multi fixtures have extra info that isn't already available in the
     // fixture list provided to the Cosmos UI (fixture names, which in lazy mode
     // are revealed after importing a fixture module).
-    if (props.lazy && props.fixtureItem.type === 'multi') {
-      rendererConnect.postMessage({
-        type: 'fixtureListItemUpdate',
-        payload: {
-          rendererId,
-          fixturePath: props.fixtureId.path,
-          fixtureItem: props.fixtureItem,
-        },
-      });
+    if (props.lazy) {
+      setLazyItems(
+        props.fixtureItem.type === 'multi'
+          ? { [props.fixtureId.path]: props.fixtureItem }
+          : noLazyItem
+      );
     }
-  }, [
-    props.fixtureId.path,
-    props.fixtureItem,
-    props.lazy,
-    rendererConnect,
-    rendererId,
-  ]);
+  }, [props.fixtureId.path, props.fixtureItem, props.lazy, setLazyItems]);
 
   React.useEffect(() => {
     if (!isEqual(state.fixtureState, state.syncedFixtureState)) {
@@ -116,3 +108,5 @@ export function FixtureProvider(props: Props) {
     </FixtureContext.Provider>
   );
 }
+
+const noLazyItem = {};
diff --git a/packages/react-cosmos-renderer/src/rendererConnect/RendererContext.ts b/packages/react-cosmos-renderer/src/rendererConnect/RendererContext.ts
index 8d810151ad..30daaab0be 100644
--- a/packages/react-cosmos-renderer/src/rendererConnect/RendererContext.ts
+++ b/packages/react-cosmos-renderer/src/rendererConnect/RendererContext.ts
@@ -1,5 +1,9 @@
 import React from 'react';
-import { RendererConnect, RendererSearchParams } from 'react-cosmos-core';
+import {
+  FixtureList,
+  RendererConnect,
+  RendererSearchParams,
+} from 'react-cosmos-core';
 
 export type RendererContextValue = {
   rendererId: string;
@@ -7,6 +11,8 @@ export type RendererContextValue = {
   searchParams: RendererSearchParams;
   setSearchParams(nextParams: RendererSearchParams): void;
   reloadRenderer(): void;
+  lazyItems: FixtureList;
+  setLazyItems: React.Dispatch<React.SetStateAction<FixtureList>>;
 };
 
 export const RendererContext = React.createContext<RendererContextValue>({
@@ -18,4 +24,6 @@ export const RendererContext = React.createContext<RendererContextValue>({
   searchParams: {},
   setSearchParams: () => {},
   reloadRenderer: () => {},
+  lazyItems: {},
+  setLazyItems: () => {},
 });
diff --git a/packages/react-cosmos-renderer/src/rendererConnect/RendererProvider.tsx b/packages/react-cosmos-renderer/src/rendererConnect/RendererProvider.tsx
new file mode 100644
index 0000000000..4be358f900
--- /dev/null
+++ b/packages/react-cosmos-renderer/src/rendererConnect/RendererProvider.tsx
@@ -0,0 +1,45 @@
+'use client';
+import React from 'react';
+import {
+  FixtureList,
+  RendererConnect,
+  RendererSearchParams,
+} from 'react-cosmos-core';
+import { RendererContext } from './RendererContext.js';
+
+export type Props = {
+  children: React.ReactNode;
+  rendererId: string;
+  rendererConnect: RendererConnect;
+  searchParams: RendererSearchParams;
+  setSearchParams(nextParams: RendererSearchParams): void;
+  reloadRenderer(): void;
+};
+export function RendererProvider(props: Props) {
+  const [lazyItems, setLazyItems] = React.useState<FixtureList>({});
+
+  const value = React.useMemo(() => {
+    return {
+      rendererId: props.rendererId,
+      rendererConnect: props.rendererConnect,
+      searchParams: props.searchParams,
+      setSearchParams: props.setSearchParams,
+      reloadRenderer: props.reloadRenderer,
+      lazyItems,
+      setLazyItems,
+    };
+  }, [
+    lazyItems,
+    props.reloadRenderer,
+    props.rendererConnect,
+    props.rendererId,
+    props.searchParams,
+    props.setSearchParams,
+  ]);
+
+  return (
+    <RendererContext.Provider value={value}>
+      {props.children}
+    </RendererContext.Provider>
+  );
+}
diff --git a/packages/react-cosmos-renderer/src/testHelpers/createRendererConnectTestApi.ts b/packages/react-cosmos-renderer/src/testHelpers/createRendererConnectTestApi.ts
index 9b639f52fb..d5b4d42ff9 100644
--- a/packages/react-cosmos-renderer/src/testHelpers/createRendererConnectTestApi.ts
+++ b/packages/react-cosmos-renderer/src/testHelpers/createRendererConnectTestApi.ts
@@ -1,7 +1,6 @@
 import until from 'async-until';
 import { findLast } from 'lodash-es';
 import {
-  FixtureListItemUpdateResponse,
   FixtureListUpdateResponse,
   FixtureState,
   FixtureStateChangeResponse,
@@ -24,9 +23,6 @@ export type RendererConnectTestApi = {
   fixtureListUpdate: (
     payload: FixtureListUpdateResponse['payload']
   ) => Promise<void>;
-  fixtureListItemUpdate: (
-    payload: FixtureListItemUpdateResponse['payload']
-  ) => Promise<void>;
   fixtureStateChange: (
     payload: FixtureStateChangeResponse['payload']
   ) => Promise<void>;
@@ -47,7 +43,6 @@ export function createRendererConnectTestApi(args: {
     setFixtureState,
     rendererReady,
     fixtureListUpdate,
-    fixtureListItemUpdate,
     fixtureStateChange,
     getLastFixtureState,
     clearResponses: args.clearResponses,
@@ -103,15 +98,6 @@ export function createRendererConnectTestApi(args: {
     });
   }
 
-  async function fixtureListItemUpdate(
-    payload: FixtureListItemUpdateResponse['payload']
-  ) {
-    await untilResponse({
-      type: 'fixtureListItemUpdate',
-      payload,
-    });
-  }
-
   async function fixtureStateChange(
     payload: FixtureStateChangeResponse['payload']
   ) {
diff --git a/packages/react-cosmos-renderer/src/testHelpers/mountTestRenderer.tsx b/packages/react-cosmos-renderer/src/testHelpers/mountTestRenderer.tsx
index 4263fffd86..603b65d16c 100644
--- a/packages/react-cosmos-renderer/src/testHelpers/mountTestRenderer.tsx
+++ b/packages/react-cosmos-renderer/src/testHelpers/mountTestRenderer.tsx
@@ -13,10 +13,7 @@ import {
 } from 'react-cosmos-core';
 import { ReactTestRenderer, act, create } from 'react-test-renderer';
 import { ClientFixtureLoader } from '../fixtureLoaders/ClientFixtureLoader.js';
-import {
-  RendererContext,
-  RendererContextValue,
-} from '../rendererConnect/RendererContext.js';
+import { RendererProvider } from '../rendererConnect/RendererProvider.js';
 import {
   RendererConnectTestApi,
   createRendererConnectTestApi,
@@ -91,19 +88,19 @@ function getElement(rendererConnect: RendererConnect, args: RendererTestArgs) {
     decorators = {},
     lazy = false,
   } = args;
-  const contextValue: RendererContextValue = {
-    rendererId,
-    rendererConnect,
-    searchParams,
-    setSearchParams,
-    reloadRenderer,
-  };
+
   return (
-    <RendererContext.Provider value={contextValue}>
+    <RendererProvider
+      rendererId={rendererId}
+      rendererConnect={rendererConnect}
+      searchParams={searchParams}
+      setSearchParams={setSearchParams}
+      reloadRenderer={reloadRenderer}
+    >
       <ClientFixtureLoader
         moduleWrappers={createModuleWrappers(fixtures, decorators, lazy)}
       />
-    </RendererContext.Provider>
+    </RendererProvider>
   );
 }
 
diff --git a/packages/react-cosmos-ui/src/plugins/RemoteRenderer/RemoteButton/index.tsx b/packages/react-cosmos-ui/src/plugins/RemoteRenderer/RemoteButton/index.tsx
index e492de4c7d..a737ca4652 100644
--- a/packages/react-cosmos-ui/src/plugins/RemoteRenderer/RemoteButton/index.tsx
+++ b/packages/react-cosmos-ui/src/plugins/RemoteRenderer/RemoteButton/index.tsx
@@ -52,5 +52,5 @@ function getFullUrl(rendererUrl: string) {
   // Renderer URL can be absolute or relative, depending on whether the renderer
   // is running on the same host/port as the playground
   if (rendererUrl.startsWith('http')) return rendererUrl;
-  return `${location.origin}${rendererUrl}`;
+  return new URL(rendererUrl, location.origin).toString();
 }
diff --git a/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/__tests__/fixtureListItemUpdate.ts b/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/__tests__/fixtureListItemUpdate.ts
deleted file mode 100644
index 2f40c1f595..0000000000
--- a/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/__tests__/fixtureListItemUpdate.ts
+++ /dev/null
@@ -1,56 +0,0 @@
-import { waitFor } from '@testing-library/dom';
-import { FixtureList } from 'react-cosmos-core';
-import { loadPlugins, resetPlugins } from 'react-plugin';
-import {
-  getRendererCoreMethods,
-  mockNotifications,
-  mockRouter,
-} from '../../../../testHelpers/pluginMocks.js';
-import { register } from '../../index.js';
-import {
-  mockFixtureListItemUpdate,
-  mockFixtureListUpdate,
-  mockRendererReady,
-} from '../../testHelpers/index.js';
-
-beforeEach(register);
-
-afterEach(resetPlugins);
-
-const fixtures: FixtureList = {
-  'ein.js': { type: 'single' },
-  'zwei.js': { type: 'single' },
-  'drei.js': { type: 'single' },
-};
-
-function registerTestPlugins() {
-  mockRouter({
-    getSelectedFixtureId: () => null,
-  });
-  mockNotifications();
-}
-
-function loadTestPlugins() {
-  loadPlugins();
-  mockRendererReady('mockRendererId1');
-  mockFixtureListUpdate('mockRendererId1', fixtures);
-}
-
-it('updates fixture item in renderer state', async () => {
-  registerTestPlugins();
-  loadTestPlugins();
-  mockFixtureListItemUpdate('mockRendererId1', 'drei.js', {
-    type: 'multi',
-    fixtureNames: ['a', 'b', 'c'],
-  });
-
-  await waitFor(() =>
-    expect(getRendererCoreMethods().getFixtures()).toEqual({
-      ...fixtures,
-      'drei.js': {
-        type: 'multi',
-        fixtureNames: ['a', 'b', 'c'],
-      },
-    })
-  );
-});
diff --git a/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/fixtureListItemUpdate.ts b/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/fixtureListItemUpdate.ts
deleted file mode 100644
index 273ead95aa..0000000000
--- a/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/fixtureListItemUpdate.ts
+++ /dev/null
@@ -1,21 +0,0 @@
-import { FixtureListItemUpdateResponse } from 'react-cosmos-core';
-import { RendererCoreContext } from '../shared/index.js';
-
-export function receiveFixtureListItemUpdateResponse(
-  context: RendererCoreContext,
-  { payload }: FixtureListItemUpdateResponse
-) {
-  const { rendererId, fixturePath, fixtureItem } = payload;
-  const { primaryRendererId } = context.getState();
-
-  // Discard updates from secondary renderers
-  if (rendererId === primaryRendererId) {
-    context.setState(prevState => ({
-      ...prevState,
-      fixtures: {
-        ...prevState.fixtures,
-        [fixturePath]: fixtureItem,
-      },
-    }));
-  }
-}
diff --git a/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/index.ts b/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/index.ts
index e5ed0dde0e..28cbb1918e 100644
--- a/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/index.ts
+++ b/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/index.ts
@@ -1,6 +1,5 @@
 import { MessageType, RendererResponse } from 'react-cosmos-core';
 import { RendererCoreContext } from '../shared/index.js';
-import { receiveFixtureListItemUpdateResponse } from './fixtureListItemUpdate.js';
 import { receiveFixtureListUpdateResponse } from './fixtureListUpdate.js';
 import { receiveFixtureStateChangeResponse } from './fixtureStateChange.js';
 import { receivePlaygroundCommandResponse } from './playgroundCommand.js';
@@ -18,8 +17,6 @@ export function receiveResponse(
       return receiveRendererReadyResponse(context, rendererResponse);
     case 'fixtureListUpdate':
       return receiveFixtureListUpdateResponse(context, rendererResponse);
-    case 'fixtureListItemUpdate':
-      return receiveFixtureListItemUpdateResponse(context, rendererResponse);
     case 'fixtureStateChange':
       return receiveFixtureStateChangeResponse(context, rendererResponse);
     case 'playgroundCommand':
diff --git a/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/rendererReady.ts b/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/rendererReady.ts
index b1aecd520e..4a78fa7a1c 100644
--- a/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/rendererReady.ts
+++ b/packages/react-cosmos-ui/src/plugins/RendererCore/receiveResponse/rendererReady.ts
@@ -52,7 +52,9 @@ function selectInitialFixture(
   fixtureId: FixtureId
 ) {
   const router = getMethodsOf<RouterSpec>('router');
-  router.selectFixture(fixtureId);
+  if (!router.getSelectedFixtureId()) {
+    router.selectFixture(fixtureId);
+  }
 }
 
 function selectFixtureFromUrlParams(
diff --git a/packages/react-cosmos-ui/src/plugins/RendererCore/testHelpers/index.ts b/packages/react-cosmos-ui/src/plugins/RendererCore/testHelpers/index.ts
index 7124c98628..acee8bdc79 100644
--- a/packages/react-cosmos-ui/src/plugins/RendererCore/testHelpers/index.ts
+++ b/packages/react-cosmos-ui/src/plugins/RendererCore/testHelpers/index.ts
@@ -1,8 +1,6 @@
 import {
   FixtureId,
   FixtureList,
-  FixtureListItem,
-  FixtureListItemUpdateResponse,
   FixtureListUpdateResponse,
   FixtureState,
   FixtureStateChangeResponse,
@@ -37,21 +35,6 @@ export function createFixtureListUpdateResponse(
   };
 }
 
-export function createFixtureListItemUpdateResponse(
-  rendererId: RendererId,
-  fixturePath: string,
-  fixtureItem: FixtureListItem
-): FixtureListItemUpdateResponse {
-  return {
-    type: 'fixtureListItemUpdate',
-    payload: {
-      rendererId,
-      fixturePath,
-      fixtureItem,
-    },
-  };
-}
-
 export function createFixtureStateChangeResponse(
   rendererId: RendererId,
   fixtureId: FixtureId,
@@ -85,16 +68,6 @@ export function mockFixtureListUpdate(
   );
 }
 
-export function mockFixtureListItemUpdate(
-  rendererId: RendererId,
-  fixturePath: string,
-  fixtureItem: FixtureListItem
-) {
-  return getRendererCoreMethods().receiveResponse(
-    createFixtureListItemUpdateResponse(rendererId, fixturePath, fixtureItem)
-  );
-}
-
 export function mockFixtureStateChange(
   rendererId: RendererId,
   fixtureId: FixtureId,