fix(studio): improve preview loading reliability

packages/studio/src/components/nle/NLEContext.tsx

@@ -32,7 +32,7 @@ export interface NLEContextValue {
   togglePlay: () => void;
   seek: (time: number, options?: { keepPlaying?: boolean }) => boolean;
   refreshPlayer: () => void;
-  onIframeLoad: () => void;
+  onIframeLoad: (reportError?: (message: string) => void) => void;
   // composition stack (from useCompositionStack)
   compositionStack: CompositionLevel[];
   updateCompositionStack: React.Dispatch<React.SetStateAction<CompositionLevel[]>>;
@@ -122,14 +122,17 @@ export function NLEProvider({
     refreshPlayer();
   }, [refreshKey, refreshPlayer]);
 
-  const onIframeLoad = useCallback(() => {
-    baseOnIframeLoad();
-    // Pre-load + register MotionPathPlugin once so adding a motion path in the
-    // studio doesn't take the async plugin-load flash path on the first soft
-    // reload (the comp may not ship the plugin until it actually uses one).
-    ensureMotionPathPluginLoaded(iframeRef.current);
-    onIframeRef?.(iframeRef.current);
-  }, [baseOnIframeLoad, iframeRef, onIframeRef]);
+  const onIframeLoad = useCallback(
+    (reportError?: (message: string) => void) => {
+      baseOnIframeLoad(reportError);
+      // Pre-load + register MotionPathPlugin once so adding a motion path in the
+      // studio doesn't take the async plugin-load flash path on the first soft
+      // reload (the comp may not ship the plugin until it actually uses one).
+      ensureMotionPathPluginLoaded(iframeRef.current);
+      onIframeRef?.(iframeRef.current);
+    },
+    [baseOnIframeLoad, iframeRef, onIframeRef],
+  );
 
   const {
     compositionStack,

packages/studio/src/components/nle/NLEPreview.tsx

@@ -15,7 +15,7 @@ import { readStudioUiPreferences, writeStudioUiPreferences } from "../../utils/s
 interface NLEPreviewProps {
   projectId: string;
   iframeRef: RefObject<HTMLIFrameElement | null>;
-  onIframeLoad: () => void;
+  onIframeLoad: (reportError?: (message: string) => void) => void;
   onCompositionLoadingChange?: (loading: boolean) => void;
   portrait?: boolean;
   directUrl?: string;
@@ -491,9 +491,9 @@ export const NLEPreview = memo(function NLEPreview({
               ref={setPreviewIframeRef}
               projectId={directUrl ? undefined : projectId}
               directUrl={directUrl}
-              onLoad={() => {
+              onLoad={(reportError) => {
                 updateCompositionSizeFromPreview();
-                onIframeLoad();
+                onIframeLoad(reportError);
                 applyInitialZoom();
               }}
               onCompositionLoadingChange={onCompositionLoadingChange}

packages/studio/src/components/sidebar/CompositionsTab.drag.test.tsx

@@ -40,6 +40,33 @@ function mount(onSelect = vi.fn(), onAddToTimeline = vi.fn()) {
 }
 
 describe("composition card drag", () => {
+  it("uses a cached image instead of eagerly mounting a live preview iframe", () => {
+    const { host } = mount();
+    expect(host.querySelector('img[src*="/thumbnail/"]')).not.toBeNull();
+    expect(host.querySelector("iframe")).toBeNull();
+  });
+
+  it("mounts one live preview only after sustained hover and removes it on leave", () => {
+    vi.useFakeTimers();
+    const consoleError = vi.spyOn(console, "error").mockImplementation(() => {});
+    try {
+      const { host, card } = mount();
+      act(() => {
+        card.dispatchEvent(new Event("pointerover", { bubbles: true }));
+        vi.advanceTimersByTime(300);
+      });
+      expect(host.querySelectorAll("iframe")).toHaveLength(1);
+
+      act(() => {
+        card.dispatchEvent(new Event("pointerout", { bubbles: true }));
+      });
+      expect(host.querySelector("iframe")).toBeNull();
+    } finally {
+      consoleError.mockRestore();
+      vi.useRealTimers();
+    }
+  });
+
   it("keeps ordinary click navigation", () => {
     const { card, onSelect } = mount();
     act(() => card.click());

packages/studio/src/components/sidebar/CompositionsTab.tsx

@@ -1,5 +1,6 @@
 import { memo, useCallback, useEffect, useRef, useState } from "react";
 import { setPreviewMediaMuted } from "../../player/lib/timelineIframeHelpers";
+import { buildCompositionThumbnailUrl } from "../../player/components/CompositionThumbnail";
 import { TIMELINE_COMPOSITION_MIME } from "../../utils/timelineCompositionDrop";
 
 interface CompositionsTabProps {
@@ -130,6 +131,7 @@ function CompCard({
 }) {
   const [hovered, setHovered] = useState(false);
   const [stageSize, setStageSize] = useState(DEFAULT_PREVIEW_STAGE);
+  const [livePreviewLoaded, setLivePreviewLoaded] = useState(false);
   const iframeRef = useRef<HTMLIFrameElement | null>(null);
   const hoverTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
   const syncTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
@@ -159,9 +161,16 @@ function CompCard({
       hoverTimer.current = null;
     }
     setHovered(false);
+    setLivePreviewLoaded(false);
   };
   const name = comp.replace(/^compositions\//, "").replace(/\.html$/, "");
   const previewUrl = `/api/projects/${projectId}/preview/comp/${comp}`;
+  const thumbnailUrl = buildCompositionThumbnailUrl({
+    previewUrl,
+    seekTime: 0,
+    duration: THUMBNAIL_SEEK_TIME_SECONDS * 2,
+    origin: window.location.origin,
+  });
   const previewScale = resolveCompositionPreviewScale({
     cardWidth: CARD_W,
     cardHeight: CARD_H,
@@ -172,7 +181,7 @@ function CompCard({
   const thumbnailOffsetY = (CARD_H - stageSize.height * previewScale) / 2;
 
   useEffect(() => {
-    requestIframePlaybackSync(hovered);
+    if (hovered) requestIframePlaybackSync(true);
   }, [hovered, requestIframePlaybackSync]);
 
   useEffect(() => {
@@ -216,36 +225,49 @@ function CompCard({
       }`}
     >
       <div className="w-20 h-[45px] rounded overflow-hidden bg-neutral-900 flex-shrink-0 relative">
-        <iframe
-          ref={iframeRef}
-          src={previewUrl}
-          sandbox="allow-scripts allow-same-origin"
+        <img
+          src={thumbnailUrl}
+          alt=""
+          draggable={false}
           loading="lazy"
-          className="absolute border-none pointer-events-none"
-          style={{
-            transformOrigin: "0 0",
-            width: stageSize.width,
-            height: stageSize.height,
-            left: thumbnailOffsetX,
-            top: thumbnailOffsetY,
-            transform: `scale(${previewScale})`,
-          }}
-          onLoad={(e) => {
-            try {
-              const iframe = e.currentTarget;
-              const root = iframe.contentDocument?.querySelector("[data-composition-id]");
-              const width = Number(root?.getAttribute("data-width")) || DEFAULT_PREVIEW_STAGE.width;
-              const height =
-                Number(root?.getAttribute("data-height")) || DEFAULT_PREVIEW_STAGE.height;
-              setStageSize({ width, height });
-              requestIframePlaybackSync(hovered);
-            } catch {
-              setStageSize(DEFAULT_PREVIEW_STAGE);
-            }
-          }}
-          title={`${name} preview`}
-          tabIndex={-1}
+          decoding="async"
+          className={`absolute inset-0 h-full w-full object-contain transition-opacity ${
+            livePreviewLoaded ? "opacity-0" : "opacity-100"
+          }`}
         />
+        {hovered && (
+          <iframe
+            ref={iframeRef}
+            src={previewUrl}
+            sandbox="allow-scripts allow-same-origin"
+            className="absolute border-none pointer-events-none"
+            style={{
+              transformOrigin: "0 0",
+              width: stageSize.width,
+              height: stageSize.height,
+              left: thumbnailOffsetX,
+              top: thumbnailOffsetY,
+              transform: `scale(${previewScale})`,
+            }}
+            onLoad={(e) => {
+              try {
+                const iframe = e.currentTarget;
+                const root = iframe.contentDocument?.querySelector("[data-composition-id]");
+                const width =
+                  Number(root?.getAttribute("data-width")) || DEFAULT_PREVIEW_STAGE.width;
+                const height =
+                  Number(root?.getAttribute("data-height")) || DEFAULT_PREVIEW_STAGE.height;
+                setStageSize({ width, height });
+                setLivePreviewLoaded(true);
+                requestIframePlaybackSync(true);
+              } catch {
+                setStageSize(DEFAULT_PREVIEW_STAGE);
+              }
+            }}
+            title={`${name} preview`}
+            tabIndex={-1}
+          />
+        )}
       </div>
       <div
         className="min-w-0 flex-1"

packages/studio/src/player/components/Player.test.ts

@@ -1,7 +1,29 @@
 // @vitest-environment happy-dom
 
 import { describe, expect, it } from "vitest";
-import { hasUnloadedAssets, shouldShowCompositionLoadingOverlay } from "./Player";
+import {
+  hasUnloadedAssets,
+  readPreviewErrorMessage,
+  shouldShowCompositionLoadingOverlay,
+} from "./Player";
+
+describe("preview errors", () => {
+  it("reads the player probe error for the visible retry state", () => {
+    expect(
+      readPreviewErrorMessage(
+        new CustomEvent("error", {
+          detail: { message: "Composition timeline not found after 8s" },
+        }),
+      ),
+    ).toBe("Composition timeline not found after 8s");
+  });
+
+  it("falls back when the player emits an unstructured error", () => {
+    expect(readPreviewErrorMessage(new Event("error"))).toBe(
+      "The composition preview did not become ready.",
+    );
+  });
+});
 
 describe("composition loading overlay", () => {
   it("shows while the composition is loading", () => {

packages/studio/src/player/components/Player.tsx

@@ -10,7 +10,7 @@ import { HyperframesLoader } from "../../components/ui";
 interface PlayerProps {
   projectId?: string;
   directUrl?: string;
-  onLoad: () => void;
+  onLoad: (reportError: (message: string) => void) => void;
   onCompositionLoadingChange?: (loading: boolean) => void;
   portrait?: boolean;
   style?: React.CSSProperties;
@@ -38,11 +38,19 @@ function getShaderTransitionLoading(event: Event): boolean | null {
 }
 
 const COMPOSITION_LOADING_OVERLAY_DELAY_MS = 400;
+const DEFAULT_PREVIEW_ERROR = "The composition preview did not become ready.";
 
 export function shouldShowCompositionLoadingOverlay(compositionLoading: boolean): boolean {
   return compositionLoading;
 }
 
+export function readPreviewErrorMessage(event: Event): string {
+  if (!(event instanceof CustomEvent) || !isRecord(event.detail)) return DEFAULT_PREVIEW_ERROR;
+  return typeof event.detail.message === "string" && event.detail.message.trim()
+    ? event.detail.message
+    : DEFAULT_PREVIEW_ERROR;
+}
+
 function enableInteractiveIframe(player: HyperframesPlayerElement): void {
   const root = player.shadowRoot;
   if (!root) return;
@@ -122,12 +130,15 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
     const loadCountRef = useRef(0);
     const assetPollRef = useRef<ReturnType<typeof setInterval> | null>(null);
     const assetFadeRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+    const retryPreviewRef = useRef<(() => void) | null>(null);
+    const retryCountRef = useRef(0);
     const [assetsLoading, setAssetsLoading] = useState(false);
     const [assetOverlayVisible, setAssetOverlayVisible] = useState(false);
     const [assetOverlayFading, setAssetOverlayFading] = useState(false);
     const [shaderTransitionLoading, setShaderTransitionLoading] = useState(false);
     const [compositionLoading, setCompositionLoading] = useState(true);
     const [compositionOverlayDeferred, setCompositionOverlayDeferred] = useState(true);
+    const [previewError, setPreviewError] = useState<string | null>(null);
 
     // eslint-disable-next-line no-restricted-syntax
     useEffect(() => {
@@ -161,62 +172,32 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
         );
         applyPreviewVariablesToUrl(srcUrl);
         const src = srcUrl.pathname + srcUrl.search;
-        player.setAttribute("shader-capture-scale", "1");
-        player.setAttribute("shader-loading", "player");
-        player.setAttribute("src", src);
-        player.setAttribute("width", String(portrait ? 1080 : 1920));
-        player.setAttribute("height", String(portrait ? 1920 : 1080));
-        player.style.width = "100%";
-        player.style.height = "100%";
-        player.style.display = "block";
-        player.style.background = "transparent";
-        container.appendChild(player);
-
-        // Inject pasteboard shadow: let the shadow around the canvas bleed
-        // into the surrounding pasteboard area (overflow: visible on the container)
-        // and add a subtle outline + drop-shadow so the canvas boundary reads
-        // against the gray pasteboard, consistent with professional editors.
-        if (player.shadowRoot) {
-          const pasteboardStyle = document.createElement("style");
-          pasteboardStyle.textContent =
-            ".hfp-container{overflow:visible}" +
-            ".hfp-iframe{box-shadow:0 0 0 1px rgba(255,255,255,0.08),0 4px 32px rgba(0,0,0,.7)}";
-          player.shadowRoot.appendChild(pasteboardStyle);
-        }
-
-        enableInteractiveIframe(player);
-
-        // Bridge the inner iframe to the forwarded ref for useTimelinePlayer.
+        const retryPreview = () => {
+          retryCountRef.current += 1;
+          const retryUrl = new URL(src, window.location.origin);
+          retryUrl.searchParams.set("_hfStudioRetry", String(retryCountRef.current));
+          setPreviewError(null);
+          setCompositionLoading(true);
+          player.setAttribute("src", retryUrl.pathname + retryUrl.search);
+        };
+        retryPreviewRef.current = retryPreview;
         const iframe = player.iframeElement;
-        if (typeof ref === "function") {
-          ref(iframe);
-        } else if (ref) {
-          (ref as React.MutableRefObject<HTMLIFrameElement | null>).current = iframe;
-        }
-
-        // Prevent the web component's built-in click-to-toggle behavior.
-        // The studio manages playback exclusively via useTimelinePlayer.
         const preventToggle = (e: Event) => e.stopImmediatePropagation();
-        player.addEventListener("click", preventToggle, { capture: true });
-
         const handleShaderTransitionState = (event: Event) => {
           const loading = getShaderTransitionLoading(event);
           if (loading !== null) setShaderTransitionLoading(loading);
         };
-        player.addEventListener("shadertransitionstate", handleShaderTransitionState);
-
         const handleReady = () => {
+          setPreviewError(null);
           setCompositionLoading(false);
         };
-        const handleError = () => {
+        const handleError = (event: Event) => {
+          setPreviewError(readPreviewErrorMessage(event));
           setCompositionLoading(false);
         };
-        player.addEventListener("ready", handleReady);
-        player.addEventListener("error", handleError);
-
-        // Forward the iframe's native load event to the studio's onIframeLoad.
         const handleLoad = () => {
           loadCountRef.current++;
+          setPreviewError(null);
           setShaderTransitionLoading(false);
           setCompositionLoading(true);
           // Reveal animation on reload (hot-reload, composition switch)
@@ -227,7 +208,10 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
             const onEnd = () => container.classList.remove("preview-revealing");
             container.addEventListener("animationend", onEnd, { once: true });
           }
-          onLoad();
+          onLoad((message) => {
+            setPreviewError(message);
+            setCompositionLoading(false);
+          });
 
           // Show a loading overlay until every `<video>`/`<audio>` and Lottie
           // asset is ready. Without this users can click play before audio has
@@ -264,7 +248,47 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
             setAssetsLoading(false);
           }
         };
+
+        // Attach lifecycle listeners before assigning src or connecting the
+        // custom element. A warm local iframe can otherwise finish before
+        // Studio observes its load and never initialize the timeline.
         iframe.addEventListener("load", handleLoad);
+        player.addEventListener("click", preventToggle, { capture: true });
+        player.addEventListener("shadertransitionstate", handleShaderTransitionState);
+        player.addEventListener("ready", handleReady);
+        player.addEventListener("error", handleError);
+
+        // Bridge the inner iframe to the forwarded ref for useTimelinePlayer.
+        if (typeof ref === "function") {
+          ref(iframe);
+        } else if (ref) {
+          (ref as React.MutableRefObject<HTMLIFrameElement | null>).current = iframe;
+        }
+
+        player.setAttribute("shader-capture-scale", "1");
+        player.setAttribute("shader-loading", "player");
+        player.setAttribute("width", String(portrait ? 1080 : 1920));
+        player.setAttribute("height", String(portrait ? 1920 : 1080));
+        player.style.width = "100%";
+        player.style.height = "100%";
+        player.style.display = "block";
+        player.style.background = "transparent";
+        player.setAttribute("src", src);
+        container.appendChild(player);
+
+        // Inject pasteboard shadow: let the shadow around the canvas bleed
+        // into the surrounding pasteboard area (overflow: visible on the container)
+        // and add a subtle outline + drop-shadow so the canvas boundary reads
+        // against the gray pasteboard, consistent with professional editors.
+        if (player.shadowRoot) {
+          const pasteboardStyle = document.createElement("style");
+          pasteboardStyle.textContent =
+            ".hfp-container{overflow:visible}" +
+            ".hfp-iframe{box-shadow:0 0 0 1px rgba(255,255,255,0.08),0 4px 32px rgba(0,0,0,.7)}";
+          player.shadowRoot.appendChild(pasteboardStyle);
+        }
+
+        enableInteractiveIframe(player);
 
         cleanup = () => {
           iframe.removeEventListener("load", handleLoad);
@@ -275,6 +299,7 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
           if (assetPollRef.current) clearInterval(assetPollRef.current);
           assetPollRef.current = null;
           container.removeChild(player);
+          if (retryPreviewRef.current === retryPreview) retryPreviewRef.current = null;
           // Clear the forwarded ref only if it still points to THIS iframe.
           // During crossfade refreshes the retiring Player unmounts after the
           // new Player has already assigned its iframe to the same ref — blindly
@@ -381,6 +406,25 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
             />
           </div>
         )}
+        {previewError && (
+          <div
+            className="absolute inset-0 z-40 flex items-center justify-center bg-black/90 px-6 text-center"
+            data-hyperframes-ignore=""
+            data-testid="composition-preview-error"
+          >
+            <div className="max-w-sm">
+              <p className="text-sm font-semibold text-white">Preview failed to load</p>
+              <p className="mt-1 text-xs text-neutral-400">{previewError}</p>
+              <button
+                type="button"
+                className="mt-4 rounded-md bg-white px-3 py-1.5 text-xs font-semibold text-black transition-colors hover:bg-neutral-200"
+                onClick={() => retryPreviewRef.current?.()}
+              >
+                Retry preview
+              </button>
+            </div>
+          </div>
+        )}
       </div>
     );
   },

packages/studio/src/player/hooks/useTimelinePlayer.seek.test.ts

@@ -129,6 +129,39 @@ function expectStorePlaybackState(
 }
 
 describe("useTimelinePlayer seek hydration", () => {
+  it("reports when Studio cannot initialize a timeline after iframe load", () => {
+    vi.useFakeTimers();
+    const { api, root } = renderTimelinePlayerHarness();
+    const iframe = document.createElement("iframe");
+    const iframeWindow = {
+      postMessage: vi.fn(),
+      scrollTo: vi.fn(),
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+    };
+    Object.defineProperty(iframe, "contentWindow", {
+      value: iframeWindow,
+      configurable: true,
+    });
+    Object.defineProperty(iframe, "contentDocument", {
+      value: document.implementation.createHTMLDocument("preview"),
+      configurable: true,
+    });
+    const reportError = vi.fn();
+
+    act(() => {
+      api.iframeRef.current = iframe;
+      api.onIframeLoad(reportError);
+      vi.advanceTimersByTime(5000);
+    });
+
+    expect(reportError).toHaveBeenCalledWith(
+      "Studio could not initialize the composition timeline.",
+    );
+    unmountWithAct(root);
+    vi.useRealTimers();
+  });
+
   it("keeps an external seek request until the iframe adapter is ready", () => {
     const observedTimes: number[] = [];
     const unsubscribe = liveTime.subscribe((time) => {

packages/studio/src/player/hooks/useTimelineSyncCallbacks.ts

@@ -399,51 +399,60 @@ export function useTimelineSyncCallbacks({
     pendingSeekRef,
   ]);
 
-  const onIframeLoad = useCallback(() => {
-    applyPreviewAudioState();
-    if (probeIntervalRef.current) clearInterval(probeIntervalRef.current);
+  const onIframeLoad = useCallback(
+    (reportError?: (message: string) => void) => {
+      applyPreviewAudioState();
+      if (probeIntervalRef.current) clearInterval(probeIntervalRef.current);
 
-    // Fast path: adapter already available (in-place reloads, cached compositions)
-    if (initializeAdapter()) return;
+      // Fast path: adapter already available (in-place reloads, cached compositions)
+      if (initializeAdapter()) return;
 
-    // The runtime posts "state" or "timeline" messages once ready.
-    // Listen for those instead of polling.
-    const iframe = iframeRef.current;
-    let settled = false;
+      // The runtime posts "state" or "timeline" messages once ready.
+      // Listen for those instead of polling.
+      const iframe = iframeRef.current;
+      let settled = false;
 
-    const trySettle = () => {
-      if (settled) return;
-      if (initializeAdapter()) {
-        settled = true;
+      const trySettle = () => {
+        if (settled) return;
+        if (initializeAdapter()) {
+          settled = true;
+          window.removeEventListener("message", onMessage);
+          if (probeIntervalRef.current) clearInterval(probeIntervalRef.current);
+        }
+      };
+
+      const onMessage = (e: MessageEvent) => {
+        if (e.source && iframe && e.source !== iframe.contentWindow) return;
+        const data = e.data;
+        if (
+          data?.source === "hf-preview" &&
+          (data?.type === "state" || data?.type === "timeline")
+        ) {
+          // The main message handler owns protocol-error diagnostics. This readiness-only
+          // listener mirrors its acceptance gate without dispatching a duplicate event:
+          // an unsupported runtime must not make the iframe appear successfully settled.
+          if (inspectStudioRuntimeMessage(data).status === "unsupported") return;
+          trySettle();
+        }
+      };
+      window.addEventListener("message", onMessage);
+
+      // Safety net: if no message arrives within 5s, try one last time then give up.
+      probeIntervalRef.current = setTimeout(() => {
+        if (!settled) {
+          trySettle();
+          if (!settled) {
+            reportError?.("Studio could not initialize the composition timeline.");
+          }
+        }
         window.removeEventListener("message", onMessage);
-        if (probeIntervalRef.current) clearInterval(probeIntervalRef.current);
-      }
-    };
-
-    const onMessage = (e: MessageEvent) => {
-      if (e.source && iframe && e.source !== iframe.contentWindow) return;
-      const data = e.data;
-      if (data?.source === "hf-preview" && (data?.type === "state" || data?.type === "timeline")) {
-        // The main message handler owns protocol-error diagnostics. This readiness-only
-        // listener mirrors its acceptance gate without dispatching a duplicate event:
-        // an unsupported runtime must not make the iframe appear successfully settled.
-        if (inspectStudioRuntimeMessage(data).status === "unsupported") return;
-        trySettle();
-      }
-    };
-    window.addEventListener("message", onMessage);
-
-    // Safety net: if no message arrives within 5s, try one last time then give up.
-    probeIntervalRef.current = setTimeout(() => {
-      if (!settled) {
-        trySettle();
-      }
-      window.removeEventListener("message", onMessage);
-      // Never leave the preview stuck invisible if the runtime never settled
-      // (initializeAdapter reveals on success; this covers the give-up case).
-      revealIframe(iframeRef.current);
-    }, 5000) as unknown as ReturnType<typeof setInterval>;
-  }, [initializeAdapter, iframeRef, probeIntervalRef, applyPreviewAudioState]);
+        // Never leave the preview stuck invisible if the runtime never settled
+        // (initializeAdapter reveals on success; this covers the give-up case).
+        revealIframe(iframeRef.current);
+      }, 5000) as unknown as ReturnType<typeof setInterval>;
+    },
+    [initializeAdapter, iframeRef, probeIntervalRef, applyPreviewAudioState],
+  );
 
   // Stable refs so mount-effect closures always call the latest version
   const processTimelineMessageRef = { current: processTimelineMessage };