diff --git a/packages/core/src/runtime/adapters/seek-dispatch.test.ts b/packages/core/src/runtime/adapters/seek-dispatch.test.ts
new file mode 100644
index 000000000..34a70ebf9
--- /dev/null
+++ b/packages/core/src/runtime/adapters/seek-dispatch.test.ts
@@ -0,0 +1,45 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { dispatchSeekEvent, forceDispatchSeekEvent, resetSeekDispatchState } from "./seek-dispatch";
+
+describe("seek-dispatch", () => {
+  beforeEach(() => {
+    resetSeekDispatchState();
+  });
+
+  it("dispatchSeekEvent fires an hf-seek event with the time", () => {
+    const handler = vi.fn();
+    window.addEventListener("hf-seek", handler);
+    dispatchSeekEvent(2.5);
+    window.removeEventListener("hf-seek", handler);
+    expect(handler).toHaveBeenCalledTimes(1);
+    expect((handler.mock.calls[0][0] as CustomEvent).detail.time).toBe(2.5);
+  });
+
+  it("dispatchSeekEvent dedups consecutive same-time dispatches", () => {
+    const handler = vi.fn();
+    window.addEventListener("hf-seek", handler);
+    dispatchSeekEvent(4);
+    dispatchSeekEvent(4);
+    window.removeEventListener("hf-seek", handler);
+    expect(handler).toHaveBeenCalledTimes(1);
+  });
+
+  it("forceDispatchSeekEvent re-fires even at the same time (post-injection re-render)", () => {
+    const handler = vi.fn();
+    window.addEventListener("hf-seek", handler);
+    dispatchSeekEvent(6); // GPU adapters' first render at t=6
+    forceDispatchSeekEvent(6); // engine re-render after video injection, same t
+    window.removeEventListener("hf-seek", handler);
+    expect(handler).toHaveBeenCalledTimes(2);
+    expect((handler.mock.calls[1][0] as CustomEvent).detail.time).toBe(6);
+  });
+
+  it("after a force dispatch, the same time still dedups on the normal path", () => {
+    const handler = vi.fn();
+    window.addEventListener("hf-seek", handler);
+    forceDispatchSeekEvent(8);
+    dispatchSeekEvent(8); // deduped — force already recorded t=8
+    window.removeEventListener("hf-seek", handler);
+    expect(handler).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/packages/core/src/runtime/adapters/seek-dispatch.ts b/packages/core/src/runtime/adapters/seek-dispatch.ts
index 6261cc5a2..ad9f0dad8 100644
--- a/packages/core/src/runtime/adapters/seek-dispatch.ts
+++ b/packages/core/src/runtime/adapters/seek-dispatch.ts
@@ -30,6 +30,25 @@ export function dispatchSeekEvent(time: number): void {
   }
 }
 
+/**
+ * Force-dispatch a `"hf-seek"` event even if `time` equals the last dispatched
+ * time, bypassing the dedup guard.
+ *
+ * Needed for the post-video-injection GPU re-render: the engine seeks to time
+ * T (GPU adapters render once, before video frames are injected), then injects
+ * the decoded `__render_frame__` images, then must re-render GPU compositions
+ * at the *same* T so they re-upload textures from the now-present frames. The
+ * normal dedup would swallow that second dispatch.
+ */
+export function forceDispatchSeekEvent(time: number): void {
+  _lastDispatchedTime = time;
+  try {
+    window.dispatchEvent(new CustomEvent("hf-seek", { detail: { time } }));
+  } catch (err) {
+    swallow("runtime.adapters.seek-dispatch.force", err);
+  }
+}
+
 /** Reset internal state — used in tests to prevent cross-test contamination. */
 export function resetSeekDispatchState(): void {
   _lastDispatchedTime = -1;
diff --git a/packages/core/src/runtime/adapters/video-texture-compat.test.ts b/packages/core/src/runtime/adapters/video-texture-compat.test.ts
new file mode 100644
index 000000000..43dfe3690
--- /dev/null
+++ b/packages/core/src/runtime/adapters/video-texture-compat.test.ts
@@ -0,0 +1,110 @@
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import { patchWebGLVideoTextureCompat } from "./video-texture-compat";
+
+// Minimal fake WebGL2 context that records the source passed to texImage2D /
+// texSubImage2D, so we can assert the patch substitutes the injected frame.
+class FakeGL2 {
+  lastImageArgs: unknown[] | null = null;
+  lastSubArgs: unknown[] | null = null;
+  texImage2D(...args: unknown[]) {
+    this.lastImageArgs = args;
+  }
+  texSubImage2D(...args: unknown[]) {
+    this.lastSubArgs = args;
+  }
+}
+
+function makeInjectedImage(): HTMLImageElement {
+  const img = document.createElement("img");
+  img.classList.add("__render_frame__");
+  Object.defineProperty(img, "complete", { value: true, configurable: true });
+  Object.defineProperty(img, "naturalWidth", { value: 16, configurable: true });
+  return img;
+}
+
+describe("patchWebGLVideoTextureCompat", () => {
+  let originalGL2: unknown;
+
+  beforeEach(() => {
+    originalGL2 = (globalThis as Record<string, unknown>).WebGL2RenderingContext;
+    (globalThis as Record<string, unknown>).WebGL2RenderingContext = FakeGL2;
+    document.body.innerHTML = "";
+  });
+
+  afterEach(() => {
+    (globalThis as Record<string, unknown>).WebGL2RenderingContext = originalGL2;
+    document.body.innerHTML = "";
+  });
+
+  it("substitutes the decoded __render_frame__ image when uploading a <video>", () => {
+    patchWebGLVideoTextureCompat();
+
+    const video = document.createElement("video");
+    const img = makeInjectedImage();
+    document.body.append(video, img); // img is video.nextElementSibling
+
+    const gl = new FakeGL2();
+    gl.texImage2D(0x0de1, 0, 0x1908, 0x1908, 0x1401, video);
+
+    // Last argument (the source) must be swapped to the injected image.
+    expect(gl.lastImageArgs?.[gl.lastImageArgs.length - 1]).toBe(img);
+  });
+
+  it("leaves the <video> source untouched when no render frame is present (preview)", () => {
+    patchWebGLVideoTextureCompat();
+
+    const video = document.createElement("video");
+    document.body.append(video);
+
+    const gl = new FakeGL2();
+    gl.texImage2D(0x0de1, 0, 0x1908, 0x1908, 0x1401, video);
+
+    expect(gl.lastImageArgs?.[gl.lastImageArgs.length - 1]).toBe(video);
+  });
+
+  it("ignores a render-frame image that is not yet decoded", () => {
+    patchWebGLVideoTextureCompat();
+
+    const video = document.createElement("video");
+    const img = document.createElement("img");
+    img.classList.add("__render_frame__");
+    Object.defineProperty(img, "complete", { value: false, configurable: true });
+    Object.defineProperty(img, "naturalWidth", { value: 0, configurable: true });
+    document.body.append(video, img);
+
+    const gl = new FakeGL2();
+    gl.texImage2D(0x0de1, 0, 0x1908, 0x1908, 0x1401, video);
+
+    expect(gl.lastImageArgs?.[gl.lastImageArgs.length - 1]).toBe(video);
+  });
+
+  it("also patches texSubImage2D", () => {
+    patchWebGLVideoTextureCompat();
+
+    const video = document.createElement("video");
+    const img = makeInjectedImage();
+    document.body.append(video, img);
+
+    const gl = new FakeGL2();
+    gl.texSubImage2D(0x0de1, 0, 0, 0, 0x1908, 0x1401, video);
+
+    expect(gl.lastSubArgs?.[gl.lastSubArgs.length - 1]).toBe(img);
+  });
+
+  it("does not touch numeric/pixel-data overloads (no video source)", () => {
+    patchWebGLVideoTextureCompat();
+
+    const pixels = new Uint8Array([1, 2, 3, 4]);
+    const gl = new FakeGL2();
+    gl.texImage2D(0x0de1, 0, 0x1908, 1, 1, 0, 0x1908, 0x1401, pixels);
+
+    expect(gl.lastImageArgs?.[gl.lastImageArgs.length - 1]).toBe(pixels);
+  });
+
+  it("is idempotent — patching twice does not double-wrap", () => {
+    patchWebGLVideoTextureCompat();
+    const once = FakeGL2.prototype.texImage2D;
+    patchWebGLVideoTextureCompat();
+    expect(FakeGL2.prototype.texImage2D).toBe(once);
+  });
+});
diff --git a/packages/core/src/runtime/adapters/video-texture-compat.ts b/packages/core/src/runtime/adapters/video-texture-compat.ts
index 17bc0b716..2fdb8f058 100644
--- a/packages/core/src/runtime/adapters/video-texture-compat.ts
+++ b/packages/core/src/runtime/adapters/video-texture-compat.ts
@@ -1,18 +1,47 @@
 /**
- * Patches `GPUQueue.copyExternalImageToTexture` so that video-backed WebGPU
- * effects work in both preview and render mode.
+ * Patches GPU texture-upload paths so that video-backed effects work in both
+ * preview and render mode — for WebGPU (`GPUQueue.copyExternalImageToTexture`)
+ * and WebGL (`texImage2D` / `texSubImage2D`).
  *
  * During render, the engine's video-frame injector replaces each `<video>`
  * with a pre-decoded `<img class="__render_frame__">` sibling. Chrome's
  * headless compositor can't supply decoded frames from the native `<video>`
- * element to WebGPU, so `copyExternalImageToTexture({ source: video })`
- * fails with "Browser fails extracting valid resource from external image."
+ * element to the GPU, so uploading a `<video>` directly fails (WebGPU throws
+ * "Browser fails extracting valid resource from external image"; WebGL uploads
+ * a black/stale frame). These patches transparently substitute the decoded
+ * render-frame `<img>` as the upload source. In preview mode (no render-frame
+ * sibling), the original `<video>` path is used unchanged.
+ */
+
+/**
+ * Resolve the decoded render-frame `<img>` for a source `<video>`, if the
+ * engine has injected one and it has decoded pixels. Returns null in preview
+ * mode or before the frame is decoded, so callers fall back to the video.
  *
- * This patch checks whether a render-frame `<img>` exists next to the
- * source `<video>`. If it does and has decoded pixels, the patch
- * transparently substitutes it as the copy source. In preview mode (no
- * render-frame sibling), the original video path is used unchanged.
+ * The injector inserts the `<img>` as the video's immediate next sibling and
+ * also gives it the id `__render_frame_<videoId>__`; we check the sibling
+ * first (cheap) and fall back to an id lookup in case a node was inserted
+ * between them.
  */
+function resolveRenderFrameImage(video: HTMLVideoElement): HTMLImageElement | null {
+  const sibling = video.nextElementSibling;
+  if (
+    sibling instanceof HTMLImageElement &&
+    sibling.classList.contains("__render_frame__") &&
+    sibling.complete &&
+    sibling.naturalWidth > 0
+  ) {
+    return sibling;
+  }
+  if (video.id) {
+    const byId = document.getElementById(`__render_frame_${video.id}__`);
+    if (byId instanceof HTMLImageElement && byId.complete && byId.naturalWidth > 0) {
+      return byId;
+    }
+  }
+  return null;
+}
+
 export function patchVideoTextureCompat(): void {
   const GPUQueueCtor = (globalThis as Record<string, unknown>).GPUQueue as
     | { prototype: Record<string, unknown> }
@@ -32,16 +61,51 @@ export function patchVideoTextureCompat(): void {
     copySize: unknown,
   ) {
     if (source?.source instanceof HTMLVideoElement) {
-      const sibling = source.source.nextElementSibling;
-      if (
-        sibling instanceof HTMLImageElement &&
-        sibling.classList.contains("__render_frame__") &&
-        sibling.complete &&
-        sibling.naturalWidth > 0
-      ) {
-        return orig.call(this, { ...source, source: sibling }, destination, copySize);
+      const img = resolveRenderFrameImage(source.source);
+      if (img) {
+        return orig.call(this, { ...source, source: img }, destination, copySize);
       }
     }
     return orig.call(this, source, destination, copySize);
   };
 }
+
+/**
+ * WebGL analog of {@link patchVideoTextureCompat}. Patches `texImage2D` and
+ * `texSubImage2D` on both `WebGL2RenderingContext` and `WebGLRenderingContext`
+ * so that when a `<video>` is passed as the texture source (the last argument
+ * in the DOM-source overloads), the decoded render-frame `<img>` is uploaded
+ * instead during render. Numeric/`ArrayBufferView` overloads are untouched —
+ * only a trailing `HTMLVideoElement` argument is substituted.
+ */
+export function patchWebGLVideoTextureCompat(): void {
+  const ctors = [
+    (globalThis as Record<string, unknown>).WebGL2RenderingContext,
+    (globalThis as Record<string, unknown>).WebGLRenderingContext,
+  ] as Array<{ prototype: Record<string, unknown> } | undefined>;
+
+  const methods = ["texImage2D", "texSubImage2D"] as const;
+
+  for (const ctor of ctors) {
+    const proto = ctor?.prototype;
+    if (!proto) continue;
+    for (const method of methods) {
+      const orig = proto[method] as ((...args: unknown[]) => unknown) & {
+        __hfVideoPatched?: boolean;
+      };
+      if (typeof orig !== "function" || orig.__hfVideoPatched) continue;
+
+      const patched = function (this: unknown, ...args: unknown[]) {
+        const lastIndex = args.length - 1;
+        const last = args[lastIndex];
+        if (last instanceof HTMLVideoElement) {
+          const img = resolveRenderFrameImage(last);
+          if (img) args[lastIndex] = img;
+        }
+        return orig.apply(this, args);
+      } as ((...args: unknown[]) => unknown) & { __hfVideoPatched?: boolean };
+      patched.__hfVideoPatched = true;
+      proto[method] = patched;
+    }
+  }
+}
diff --git a/packages/core/src/runtime/init.ts b/packages/core/src/runtime/init.ts
index 5c2ab1bd3..0dc1ee7da 100644
--- a/packages/core/src/runtime/init.ts
+++ b/packages/core/src/runtime/init.ts
@@ -7,7 +7,11 @@ import { createAnimeJsAdapter } from "./adapters/animejs";
 import { createLottieAdapter } from "./adapters/lottie";
 import { createThreeAdapter } from "./adapters/three";
 import { createTypegpuAdapter } from "./adapters/typegpu";
-import { patchVideoTextureCompat } from "./adapters/video-texture-compat";
+import {
+  patchVideoTextureCompat,
+  patchWebGLVideoTextureCompat,
+} from "./adapters/video-texture-compat";
+import { forceDispatchSeekEvent } from "./adapters/seek-dispatch";
 import { createWaapiAdapter } from "./adapters/waapi";
 import { refreshRuntimeMediaCache, syncRuntimeMedia } from "./media";
 import { probeAndCacheElementVolume, type VolumeKeyframe } from "./mediaVolumeEnvelope.js";
@@ -1746,6 +1750,15 @@ export function initSandboxRuntimeModular(): void {
     createGsapAdapter({ getTimeline: () => state.capturedTimeline }),
   ] as RuntimeDeterministicAdapter[];
   patchVideoTextureCompat();
+  patchWebGLVideoTextureCompat();
+  // Lets the engine re-render GPU compositions after it injects decoded video
+  // frames, so video-textured WebGL/WebGPU scenes sample the correct frame.
+  window.__hfReseekGpu = (time: number) => {
+    const t = Math.max(0, Number(time) || 0);
+    window.__hfThreeTime = t;
+    window.__hfTypegpuTime = t;
+    forceDispatchSeekEvent(t);
+  };
   installRuntimeErrorDiagnostics();
   bindMediaMetadataListeners();
   runAdapters("discover");
diff --git a/packages/core/src/runtime/window.d.ts b/packages/core/src/runtime/window.d.ts
index fdd920ec1..439f9c906 100644
--- a/packages/core/src/runtime/window.d.ts
+++ b/packages/core/src/runtime/window.d.ts
@@ -45,6 +45,13 @@ declare global {
      * imperative push signal: `window.addEventListener("hf-seek", e => render(e.detail.time))`.
      */
     __hfTypegpuTime?: number;
+    /**
+     * Re-render GPU adapters (Three.js / WebGPU) at the given time, bypassing
+     * the `"hf-seek"` dedup. Called by the engine after injecting decoded
+     * video frames so GPU compositions re-upload their video textures from the
+     * freshly-injected `__render_frame__` images. See `forceDispatchSeekEvent`.
+     */
+    __hfReseekGpu?: (time: number) => void;
     __HF_PICKER_API?: HyperframePickerApi;
     gsap?: {
       timeline: (params?: { paused?: boolean }) => RuntimeTimelineLike;
diff --git a/packages/engine/src/services/videoFrameInjector.test.ts b/packages/engine/src/services/videoFrameInjector.test.ts
index 5a1c793b1..11caff59b 100644
--- a/packages/engine/src/services/videoFrameInjector.test.ts
+++ b/packages/engine/src/services/videoFrameInjector.test.ts
@@ -202,7 +202,9 @@ describe("createVideoFrameInjector cache hygiene against page-side skips", () =>
     // Pin the contract: when the page returns `[]` (no ids actually
     // injected), the cache must not record those frameIndexes, so a follow-
     // up call at the same frameIndex still issues an inject.
-    const fakePage = {} as Page;
+    // The injector calls page.evaluate after injecting frames (GPU reseek);
+    // stub it so these cache-hygiene cases exercise the real code path.
+    const fakePage = { evaluate: async () => undefined } as unknown as Page;
     const hook = createVideoFrameInjector(
       fakeTable({ videoId: "pip", framePath: "/p", frameIndex: 5 }),
       {
@@ -235,7 +237,9 @@ describe("createVideoFrameInjector cache hygiene against page-side skips", () =>
     // record it and a second call at the same frameIndex must short-circuit.
     // This pins the happy path so a future refactor can't trade the skip
     // bug for a never-cache regression.
-    const fakePage = {} as Page;
+    // The injector calls page.evaluate after injecting frames (GPU reseek);
+    // stub it so these cache-hygiene cases exercise the real code path.
+    const fakePage = { evaluate: async () => undefined } as unknown as Page;
     const hook = createVideoFrameInjector(
       fakeTable({ videoId: "pip", framePath: "/p", frameIndex: 5 }),
       {
@@ -251,4 +255,47 @@ describe("createVideoFrameInjector cache hygiene against page-side skips", () =>
     // Cache hit — no second inject for the same frameIndex.
     expect(injectVideoFramesBatchMock).toHaveBeenCalledTimes(1);
   });
+
+  // Regression: WebGL/WebGPU compositions that sample a <video> as a texture
+  // render on `hf-seek` BEFORE frames are injected. After injecting the
+  // decoded frames, the hook must re-render the GPU adapters at the same time
+  // (window.__hfReseekGpu) so they re-upload their textures from the fresh
+  // frames — otherwise the facet flickers / goes black non-deterministically.
+  it("re-renders GPU adapters after injecting frames (post-injection reseek)", async () => {
+    const evaluate = vi.fn(async () => undefined);
+    const page = { evaluate } as unknown as Page;
+    const hook = createVideoFrameInjector(
+      fakeTable({ videoId: "facet", framePath: "/f", frameIndex: 3 }),
+      { frameSrcResolver: inlineResolver },
+    );
+
+    injectVideoFramesBatchMock.mockResolvedValueOnce(["facet"]);
+    await hook!(page, 1.5);
+
+    expect(evaluate).toHaveBeenCalledTimes(1);
+    // Re-render is requested at the same time as the seek.
+    expect(evaluate.mock.calls[0]![1]).toBe(1.5);
+    // The evaluated page function invokes window.__hfReseekGpu(time).
+    const pageFn = evaluate.mock.calls[0]![0] as (t: number) => void;
+    const reseek = vi.fn();
+    (globalThis as unknown as { window?: unknown }).window = { __hfReseekGpu: reseek };
+    pageFn(1.5);
+    delete (globalThis as unknown as { window?: unknown }).window;
+    expect(reseek).toHaveBeenCalledWith(1.5);
+  });
+
+  it("does not reseek GPU when the page injected no frames", async () => {
+    const evaluate = vi.fn(async () => undefined);
+    const page = { evaluate } as unknown as Page;
+    const hook = createVideoFrameInjector(
+      fakeTable({ videoId: "facet", framePath: "/f", frameIndex: 3 }),
+      { frameSrcResolver: inlineResolver },
+    );
+
+    // Page dropped the video (e.g. hidden host) → nothing injected → no reseek.
+    injectVideoFramesBatchMock.mockResolvedValueOnce([]);
+    await hook!(page, 1.5);
+
+    expect(evaluate).not.toHaveBeenCalled();
+  });
 });
diff --git a/packages/engine/src/services/videoFrameInjector.ts b/packages/engine/src/services/videoFrameInjector.ts
index d8b9e0e56..d13c1b6b2 100644
--- a/packages/engine/src/services/videoFrameInjector.ts
+++ b/packages/engine/src/services/videoFrameInjector.ts
@@ -214,6 +214,17 @@ export function createVideoFrameInjector(
           lastInjectedFrameByVideo.set(update.videoId, update.frameIndex);
         }
       }
+      if (injectedIds.size > 0) {
+        // GPU compositions (WebGL / WebGPU) that sample these videos as
+        // textures already rendered once on the pre-injection seek, reading a
+        // stale/black frame. Now that the decoded `__render_frame__` images are
+        // in the DOM, re-render the GPU adapters at the same time so they
+        // re-upload their video textures from the correct frame. No-op in
+        // compositions without a GPU adapter.
+        await page.evaluate((t: number) => {
+          (window as unknown as { __hfReseekGpu?: (n: number) => void }).__hfReseekGpu?.(t);
+        }, time);
+      }
     }
   };
 }
diff --git a/packages/producer/tests/webgl-video-texture-render-compat/meta.json b/packages/producer/tests/webgl-video-texture-render-compat/meta.json
new file mode 100644
index 000000000..11dcfd2e4
--- /dev/null
+++ b/packages/producer/tests/webgl-video-texture-render-compat/meta.json
@@ -0,0 +1,13 @@
+{
+  "name": "webgl-video-texture-render-compat",
+  "description": "Regression guard for deterministic WebGL video textures. A WebGL2 canvas samples a <video> as a texture every hf-seek. In headless render, Chrome's compositor can't feed decoded <video> frames to WebGL, so the engine injects a decoded __render_frame__ <img> sibling and the core texImage2D video-texture patch + post-injection GPU reseek must supply the correct frame. Without that fix the rendered facets are black/stale while the preview snapshot shows the video, so render-vs-snapshot PSNR collapses. This fixture fails without the fix and passes with it.",
+  "tags": ["regression", "render-compat", "adapter"],
+  "minPsnr": 30,
+  "maxFrameFailures": 0,
+  "minAudioCorrelation": 0,
+  "maxAudioLagWindows": 1,
+  "renderConfig": {
+    "fps": 30,
+    "workers": 1
+  }
+}
diff --git a/packages/producer/tests/webgl-video-texture-render-compat/output/compiled.html b/packages/producer/tests/webgl-video-texture-render-compat/output/compiled.html
new file mode 100644
index 000000000..e2d424c51
--- /dev/null
+++ b/packages/producer/tests/webgl-video-texture-render-compat/output/compiled.html
@@ -0,0 +1,106 @@
+<!DOCTYPE html>
+<html>
+  <head><style data-hyperframes-text-rendering="true">html,body,*{text-rendering:geometricPrecision}</style>
+    <style>
+      body {
+        margin: 0;
+        background: #000;
+      }
+      [data-composition-id="webgl-video-texture-test"] {
+        position: relative;
+        overflow: hidden;
+      }
+      #gl {
+        position: absolute;
+        top: 0;
+        left: 0;
+        width: 1280px;
+        height: 720px;
+      }
+      /* Texture-source video: sampled into WebGL only, parked off-canvas. */
+      #vid {
+        position: absolute;
+        top: 0;
+        left: 0;
+        width: 4px;
+        height: 4px;
+        opacity: 0;
+        z-index: -1;
+      }
+    </style>
+  </head>
+  <body>
+    <div id="root" data-composition-id="webgl-video-texture-test" data-width="1280" data-height="720" data-start="0" data-duration="2">
+      <video id="vid" class="clip" data-start="0" data-duration="2" data-track-index="0" src="clip.mp4" muted playsinline data-end="2" data-has-audio="false"></video>
+      <canvas id="gl"></canvas>
+
+      
+    </div>
+  <script>// WebGL2 textured fullscreen triangle sampling the source video element.
+        // The handler uploads that video as a texture on every hf-seek — the
+        // natural author pattern. In headless render, Chrome can't supply decoded
+        // video frames to WebGL, so the core video-texture patch substitutes the
+        // engine's injected, decoded render-frame image, and the post-injection
+        // GPU reseek re-runs this handler. With the fix, render reproduces the
+        // preview snapshot (PSNR high); without it the canvas is black (PSNR
+        // collapses). NB: avoid writing literal tag syntax in comments here — the
+        // compiler's media-attribute injection scans the raw HTML for it.
+        (function () {
+          var canvas = document.getElementById("gl");
+          canvas.width = 1280;
+          canvas.height = 720;
+          var gl = canvas.getContext("webgl2", { preserveDrawingBuffer: true });
+          if (!gl) return;
+
+          var VS =
+            "#version 300 es\n" +
+            "in vec2 p; out vec2 uv;\n" +
+            "void main(){ uv = vec2(p.x*0.5+0.5, 0.5-p.y*0.5); gl_Position = vec4(p,0.0,1.0); }";
+          var FS =
+            "#version 300 es\n" +
+            "precision highp float; in vec2 uv; uniform sampler2D tex; out vec4 c;\n" +
+            "void main(){ c = texture(tex, uv); }";
+
+          function sh(type, src) {
+            var s = gl.createShader(type);
+            gl.shaderSource(s, src);
+            gl.compileShader(s);
+            return s;
+          }
+          var prog = gl.createProgram();
+          gl.attachShader(prog, sh(gl.VERTEX_SHADER, VS));
+          gl.attachShader(prog, sh(gl.FRAGMENT_SHADER, FS));
+          gl.linkProgram(prog);
+          gl.useProgram(prog);
+
+          var buf = gl.createBuffer();
+          gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+          gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1, -1, 3, -1, -1, 3]), gl.STATIC_DRAW);
+          var loc = gl.getAttribLocation(prog, "p");
+          gl.enableVertexAttribArray(loc);
+          gl.vertexAttribPointer(loc, 2, gl.FLOAT, false, 0, 0);
+
+          var tex = gl.createTexture();
+          gl.bindTexture(gl.TEXTURE_2D, tex);
+          gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+          gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+          gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+
+          var video = document.getElementById("vid");
+
+          function render() {
+            if (video && video.readyState >= 2) {
+              gl.bindTexture(gl.TEXTURE_2D, tex);
+              gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, video);
+            }
+            gl.clearColor(0, 0, 0, 1);
+            gl.clear(gl.COLOR_BUFFER_BIT);
+            gl.drawArrays(gl.TRIANGLES, 0, 3);
+          }
+
+          window.addEventListener("hf-seek", function () {
+            render();
+          });
+          render();
+        })();</script></body>
+</html>
diff --git a/packages/producer/tests/webgl-video-texture-render-compat/output/output.mp4 b/packages/producer/tests/webgl-video-texture-render-compat/output/output.mp4
new file mode 100644
index 000000000..c83b966b6
--- /dev/null
+++ b/packages/producer/tests/webgl-video-texture-render-compat/output/output.mp4
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:b42f669f775a304b8bd9b5bd09c508a61fa354c950e0fb3081fecc86ff749e06
+size 1075677
diff --git a/packages/producer/tests/webgl-video-texture-render-compat/src/clip.mp4 b/packages/producer/tests/webgl-video-texture-render-compat/src/clip.mp4
new file mode 100644
index 000000000..b401d9965
--- /dev/null
+++ b/packages/producer/tests/webgl-video-texture-render-compat/src/clip.mp4
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:c8571357061d144053774be928e226faf65a35626587c27459a25421d0941ac8
+size 133576
diff --git a/packages/producer/tests/webgl-video-texture-render-compat/src/index.html b/packages/producer/tests/webgl-video-texture-render-compat/src/index.html
new file mode 100644
index 000000000..8c8edcaba
--- /dev/null
+++ b/packages/producer/tests/webgl-video-texture-render-compat/src/index.html
@@ -0,0 +1,124 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <style>
+      body {
+        margin: 0;
+        background: #000;
+      }
+      [data-composition-id="webgl-video-texture-test"] {
+        position: relative;
+        overflow: hidden;
+      }
+      #gl {
+        position: absolute;
+        top: 0;
+        left: 0;
+        width: 1280px;
+        height: 720px;
+      }
+      /* Texture-source video: sampled into WebGL only, parked off-canvas. */
+      #vid {
+        position: absolute;
+        top: 0;
+        left: 0;
+        width: 4px;
+        height: 4px;
+        opacity: 0;
+        z-index: -1;
+      }
+    </style>
+  </head>
+  <body>
+    <div
+      id="root"
+      data-composition-id="webgl-video-texture-test"
+      data-width="1280"
+      data-height="720"
+      data-start="0"
+      data-duration="2"
+    >
+      <video
+        id="vid"
+        class="clip"
+        data-start="0"
+        data-duration="2"
+        data-track-index="0"
+        src="clip.mp4"
+        muted
+        playsinline
+      ></video>
+      <canvas id="gl"></canvas>
+
+      <script>
+        // WebGL2 textured fullscreen triangle sampling the source video element.
+        // The handler uploads that video as a texture on every hf-seek — the
+        // natural author pattern. In headless render, Chrome can't supply decoded
+        // video frames to WebGL, so the core video-texture patch substitutes the
+        // engine's injected, decoded render-frame image, and the post-injection
+        // GPU reseek re-runs this handler. With the fix, render reproduces the
+        // preview snapshot (PSNR high); without it the canvas is black (PSNR
+        // collapses). NB: avoid writing literal tag syntax in comments here — the
+        // compiler's media-attribute injection scans the raw HTML for it.
+        (function () {
+          var canvas = document.getElementById("gl");
+          canvas.width = 1280;
+          canvas.height = 720;
+          var gl = canvas.getContext("webgl2", { preserveDrawingBuffer: true });
+          if (!gl) return;
+
+          var VS =
+            "#version 300 es\n" +
+            "in vec2 p; out vec2 uv;\n" +
+            "void main(){ uv = vec2(p.x*0.5+0.5, 0.5-p.y*0.5); gl_Position = vec4(p,0.0,1.0); }";
+          var FS =
+            "#version 300 es\n" +
+            "precision highp float; in vec2 uv; uniform sampler2D tex; out vec4 c;\n" +
+            "void main(){ c = texture(tex, uv); }";
+
+          function sh(type, src) {
+            var s = gl.createShader(type);
+            gl.shaderSource(s, src);
+            gl.compileShader(s);
+            return s;
+          }
+          var prog = gl.createProgram();
+          gl.attachShader(prog, sh(gl.VERTEX_SHADER, VS));
+          gl.attachShader(prog, sh(gl.FRAGMENT_SHADER, FS));
+          gl.linkProgram(prog);
+          gl.useProgram(prog);
+
+          var buf = gl.createBuffer();
+          gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+          gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1, -1, 3, -1, -1, 3]), gl.STATIC_DRAW);
+          var loc = gl.getAttribLocation(prog, "p");
+          gl.enableVertexAttribArray(loc);
+          gl.vertexAttribPointer(loc, 2, gl.FLOAT, false, 0, 0);
+
+          var tex = gl.createTexture();
+          gl.bindTexture(gl.TEXTURE_2D, tex);
+          gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+          gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+          gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+
+          var video = document.getElementById("vid");
+
+          function render() {
+            if (video && video.readyState >= 2) {
+              gl.bindTexture(gl.TEXTURE_2D, tex);
+              gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, video);
+            }
+            gl.clearColor(0, 0, 0, 1);
+            gl.clear(gl.COLOR_BUFFER_BIT);
+            gl.drawArrays(gl.TRIANGLES, 0, 3);
+          }
+
+          window.addEventListener("hf-seek", function () {
+            render();
+          });
+          render();
+        })();
+      </script>
+    </div>
+  </body>
+</html>