@@ -64,6 +64,7 @@ Set `autoplay muted` only when playback should start without a user gesture.
 | `assets-loading-ui` | `player` or `none` | `player` | `none` hides the loading-assets card; asset events still fire |
 | `low-power-idle` | boolean | false | While paused, check in once a second, not every 80 ms (many-player pages) |
 | `disable-click-to-play` | boolean | false | A click on the player no longer plays or pauses, so the page can handle it |
+| `no-load-timeout` | boolean | false | A slow load never fails at 8 s, so the page owns the deadline; script and runtime errors still fail at once |
 | `range-start` | number | — | Film second where playback starts, loops back to and parks when paused (`rangeStart`) |
 | `range-end` | number | — | Film second the range ends before: it stops or loops on the frame before it (`rangeEnd`) |
 
 
@@ -84,6 +84,7 @@ Show a static image before playback starts:
 | `assets-loading-ui`     | `player \| none`                | `player`      | `none` never shows the loading-assets card; asset events still fire         |
 | `low-power-idle`        | boolean                         | false         | While paused, check in once a second, not every 80 ms (many-player pages)   |
 | `disable-click-to-play` | boolean                         | false         | A click on the player no longer plays or pauses (host overlays own clicks)  |
+| `no-load-timeout`       | boolean                         | false         | Slow loads never fail at 8 s; the page owns the deadline. Errors still fail |
 | `range-start`           | number                          | —             | Film second where playback starts, loops back to and parks when paused      |
 | `range-end`             | number                          | —             | Film second the range ends before: it stops or loops on the frame before it |
 
 
@@ -4,7 +4,7 @@
  *
  * The probe interval polls every 200 ms until one of:
  *   - An adapter or the document resolves with a positive duration, or
- *   - 40 attempts (~8 s) expire without a result.
+ *   - 40 attempts (~8 s) expire without a result, unless the host owns the deadline.
  *
  * The `CompositionProbe` class owns the interval; the caller must call
  * `stop()` on disconnect or src change.
@@ -38,6 +38,7 @@ export interface ProbeCallbacks {
   /** Called when runtime is successfully injected (informational). */
   onRuntimeInjected?: () => void;
   resolveRuntimeUrl?: () => string;
+  hostOwnsDeadline?: () => boolean;
 }
 
 /**
@@ -121,22 +122,22 @@ export class CompositionProbe {
           };
         }
       }
+      outcome ??= this._deadlineOutcome(attempts);
       if (outcome) {
         this.stop();
         if (outcome.kind === "error") {
           this._failure = { document: this._iframe.contentDocument };
           this._callbacks.onError(outcome.message);
         } else this._callbacks.onReady(outcome.result);
-        return;
-      }
-      if (attempts >= 40) {
-        this.stop();
-        this._failure = { document: this._iframe.contentDocument };
-        this._callbacks.onError("Composition timeline not found after 8s");
       }
     }, 200);
   }
 
+  private _deadlineOutcome(attempts: number): ProbeOutcome {
+    if (attempts < 40 || this._callbacks.hostOwnsDeadline?.()) return null;
+    return { kind: "error", message: "Composition timeline not found after 8s" };
+  }
+
   private _poll(attempts: number): ProbeOutcome {
     const win = this._iframe.contentWindow;
     if (!win) return null;
 
@@ -206,6 +206,7 @@ class HyperframesPlayer extends HTMLElement {
 
     this.probe = new CompositionProbe(this.iframe, {
       resolveRuntimeUrl: () => runtimeSrcFromElement(this),
+      hostOwnsDeadline: () => this.hasAttribute("no-load-timeout"),
       onReady: (result) => this._onProbeReady(result),
       onError: (message) => this._emit(new CustomEvent("error", { detail: { message } })),
     });
 
@@ -61,6 +61,24 @@ describe("terminal probe readiness", () => {
     expectUnready(player, onReady);
   });
 
+  it("waits past 8 s for a slow runtime when the host owns the deadline", () => {
+    const { player, iframe, onError, onReady } = mountPlayer();
+    player.setAttribute("no-load-timeout", "");
+    vi.advanceTimersByTime(20_000);
+    expect(onError).not.toHaveBeenCalled();
+    Object.assign(iframe.contentWindow!, { __player: { getDuration: () => 9 } });
+    vi.advanceTimersByTime(200);
+    expectTimelineReady(player, onReady);
+  });
+
+  it("still fails an author error at once when the host owns the deadline", () => {
+    const { player, iframe, onError } = mountPlayer();
+    player.setAttribute("no-load-timeout", "");
+    Object.assign(iframe.contentWindow!, { __hfPreviewErrors: ["Uncaught Error: author failed"] });
+    vi.advanceTimersByTime(200);
+    expect(onError.mock.calls[0][0].detail.message).toBe("Uncaught Error: author failed");
+  });
+
   it("rejects the failed document while its replacement is still navigating", () => {
     const { player, iframe, onReady } = mountPlayer();
     vi.advanceTimersByTime(8000);
 
@@ -0,0 +1,63 @@
+// @vitest-environment happy-dom
+// @vitest-environment-options {"happyDOM":{"settings":{"disableIframePageLoading":true}}}
+
+import React, { act, createRef } from "react";
+import { createRoot } from "react-dom/client";
+import { afterEach, expect, it, vi } from "vitest";
+import { NLEPreview } from "./NLEPreview";
+
+globalThis.IS_REACT_ACT_ENVIRONMENT = true;
+
+afterEach(() => {
+  vi.useRealTimers();
+  document.body.innerHTML = "";
+});
+
+it("keeps a shadow reload whose runtime boots after 8 s, and its player comes ready", async () => {
+  await import("@hyperframes/player");
+  vi.useFakeTimers();
+  const onShadowError = vi.fn();
+  const host = document.createElement("div");
+  document.body.append(host);
+  const root = createRoot(host);
+  await act(async () => {
+    root.render(
+      React.createElement(NLEPreview, {
+        projectId: "p",
+        iframeRef: createRef<HTMLIFrameElement>(),
+        onIframeLoad: () => {},
+        previewSlots: [
+          { gen: 0, role: "live" },
+          { gen: 1, role: "shadow", url: "/api/projects/p/preview?_t=1" },
+        ],
+        onShadowIframeLoad: () => {},
+        onShadowReadyChange: () => {},
+        onShadowError,
+        setShadowIframeNode: () => {},
+        resetPreviewSlots: () => {},
+      }),
+    );
+  });
+
+  const shadow = host.querySelectorAll<
+    HTMLElement & { iframeElement: HTMLIFrameElement; ready: boolean }
+  >("hyperframes-player")[1];
+  const iframe = shadow.iframeElement;
+  act(() => {
+    iframe.dispatchEvent(new Event("load"));
+  });
+  act(() => {
+    vi.advanceTimersByTime(10_000);
+  });
+  expect(onShadowError).not.toHaveBeenCalled();
+
+  Object.assign(iframe.contentWindow!, { __player: { getDuration: () => 9 } });
+  act(() => {
+    vi.advanceTimersByTime(1_000);
+  });
+  expect(onShadowError).not.toHaveBeenCalled();
+  expect(shadow.ready).toBe(true);
+  // The live slot keeps the player's own 8 s deadline.
+  expect(host.querySelector("hyperframes-player")?.hasAttribute("no-load-timeout")).toBe(false);
+  act(() => root.unmount());
+});
@@ -209,8 +209,7 @@ export const NLEPreview = memo(function NLEPreview({
 
   const updateCompositionSizeFromPreview = useCallback(() => {
     const next = readPreviewCompositionSize(previewIframeRef.current);
-    // Pure updater — the parent notification happens in the effect below
-    // (updaters may run more than once under Strict Mode / concurrent React).
+    // Pure updater; the effect below notifies the parent (Strict Mode may run updaters twice).
     setCompositionSize((prev) =>
       prev?.width === next?.width && prev?.height === next?.height ? prev : next,
     );
@@ -563,6 +562,7 @@ export const NLEPreview = memo(function NLEPreview({
                   onPreviewError={(message) => onShadowError(slot.gen, message)}
                   portrait={portrait}
                   suppressLoadingOverlay
+                  noLoadTimeout
                   style={SHADOW_IFRAME_STYLE}
                 />
               ),
 
@@ -37,6 +37,7 @@ interface PlayerProps {
   portrait?: boolean;
   style?: React.CSSProperties;
   suppressLoadingOverlay?: boolean;
+  noLoadTimeout?: boolean;
 }
 
 interface HyperframesPlayerElement extends HTMLElement {
@@ -154,6 +155,7 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
       portrait,
       style,
       suppressLoadingOverlay,
+      noLoadTimeout,
     },
     ref,
   ) => {
@@ -224,6 +226,7 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
           setCompositionLoading(true);
           loadStartedAtRef.current = performance.now();
           loadIdRef.current += 1;
+          player.removeAttribute("no-load-timeout");
           player.setAttribute("src", retryUrl.pathname + retryUrl.search);
         };
         retryPreviewRef.current = retryPreview;
@@ -331,6 +334,7 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
         player.setAttribute("shader-capture-scale", "1");
         player.setAttribute("shader-loading", "player");
         player.setAttribute("low-power-idle", "");
+        player.toggleAttribute("no-load-timeout", noLoadTimeout === true);
         player.setAttribute("width", String(portrait ? 1080 : 1920));
         player.setAttribute("height", String(portrait ? 1920 : 1080));
         player.style.width = "100%";
 
@@ -49,7 +49,12 @@ function isDocumentHidden(): boolean {
 
 type UseShadowPreviewReloadParams = Omit<
   UseTimelineSyncCallbacksParams,
-  "probeIntervalRef" | "onAdapterReady" | "getAdapter" | "isCurrent" | "onLoadGiveUp"
+  | "probeIntervalRef"
+  | "onAdapterReady"
+  | "getAdapter"
+  | "isCurrent"
+  | "onLoadGiveUp"
+  | "hostOwnsDeadline"
 > & {
   getAdapter: (overrideIframe?: HTMLIFrameElement | null) => PlaybackAdapter | null;
   /** Runs right after a shadow becomes the live iframe (iframeRef already points at it). */
@@ -249,6 +254,7 @@ export function useShadowPreviewReload({
     applyPreviewAudioState: () => {},
     onAdapterReady: markAdapterReady,
     isCurrent: isCurrentShadow,
+    hostOwnsDeadline: true,
   });
   cancelPendingLoadRef.current = cancelPendingLoad;
 
 
@@ -461,6 +461,31 @@ describe("shadow reload readiness and failure", () => {
     unmount(root);
   });
 
+  it("promotes a shadow whose runtime boots after Studio's own 5 s readiness wait", () => {
+    vi.useFakeTimers();
+    const onPreviewReloadFailed = vi.fn();
+    const { getApi, gen, root } = beginReload({ onPreviewReloadFailed });
+    const { win } = makeAdapterWindow();
+    const booting: Record<string, unknown> = { ...win, __player: undefined };
+    const iframe = makeFakeIframe(booting);
+    act(() => {
+      getApi().setShadowIframeNode(iframe);
+      getApi().onShadowIframeLoad(gen);
+    });
+
+    act(() => void vi.advanceTimersByTime(10_000));
+    booting.__player = win.__player;
+    act(() => {
+      window.dispatchEvent(
+        new MessageEvent("message", { data: { source: "hf-preview", type: "state" } }),
+      );
+      getApi().onShadowReadyChange(gen, true);
+    });
+    expect(getApi().iframeRef.current).toBe(iframe);
+    expect(onPreviewReloadFailed).not.toHaveBeenCalled();
+    unmount(root);
+  });
+
   it("gives a reload that replaces a slow one its own full set of budgets", () => {
     vi.useFakeTimers();
     vi.spyOn(console, "error").mockImplementation(() => {});