diff --git a/packages/producer/src/services/htmlCompiler.test.ts b/packages/producer/src/services/htmlCompiler.test.ts
index edfb63a8b0..95b49a8d56 100644
--- a/packages/producer/src/services/htmlCompiler.test.ts
+++ b/packages/producer/src/services/htmlCompiler.test.ts
@@ -1224,17 +1224,19 @@ describe("template-wrapped sub-composition media offsets", () => {
 
     const compiled = await compileForRender(projectDir, indexPath, projectDir);
 
+    // The 4s clip closes with its 2s host (data-start 2 + data-duration 2),
+    // not at its own authored end.
     expect(compiled.videos).toHaveLength(1);
     expect(compiled.videos[0]).toMatchObject({
       id: "scene-video",
       start: 2,
-      end: 6,
+      end: 4,
     });
     expect(compiled.audios).toHaveLength(1);
     expect(compiled.audios[0]).toMatchObject({
       id: "scene-video-audio",
       start: 2,
-      end: 6,
+      end: 4,
     });
   });
 
diff --git a/packages/producer/src/services/renderMediaCollector.test.ts b/packages/producer/src/services/renderMediaCollector.test.ts
index 67e52049fe..f06a269c59 100644
--- a/packages/producer/src/services/renderMediaCollector.test.ts
+++ b/packages/producer/src/services/renderMediaCollector.test.ts
@@ -17,6 +17,25 @@ describe("collectRenderMedia host windows", () => {
     expect(videos.find((v) => v.id === "blue")).toMatchObject({ start: 2, end: 4 });
   });
 
+  it("closes a host authored with data-duration but no data-end", () => {
+    // A slot shortened to 2s over a 4s scene file: the runtime hides the
+    // scene's descendants past 2s, so the planner must stop its media there.
+    const html =
+      `<div data-composition-file="hook.html" data-composition-id="hook" data-start="0" data-duration="2">` +
+      `<audio ${MEDIA_RENDER_ID_ATTR}="hook-sound" id="hook-sound" src="hook.m4a" data-start="0" data-duration="4" data-end="4"></audio>` +
+      `<video ${MEDIA_RENDER_ID_ATTR}="late" id="late" src="late.mp4" data-start="2.5" data-duration="1" data-end="3.5"></video>` +
+      `</div>` +
+      `<div data-composition-file="body.html" data-composition-id="body" data-start="hook" data-duration="2">` +
+      `<audio ${MEDIA_RENDER_ID_ATTR}="body-sound" id="body-sound" src="body.m4a" data-start="0" data-duration="4" data-end="4"></audio>` +
+      `</div>`;
+
+    const { videos, audios } = collectRenderMedia(html);
+    expect(audios.find((a) => a.id === "hook-sound")).toMatchObject({ start: 0, end: 2 });
+    expect(videos.find((v) => v.id === "late")).toBeUndefined();
+    // A host whose start is an id-ref is bounded at resolved start + duration.
+    expect(audios.find((a) => a.id === "body-sound")).toMatchObject({ start: 2, end: 4 });
+  });
+
   it("preserves an explicitly marked legacy-global media window", () => {
     const html =
       `<div data-composition-file="scene.html" data-composition-id="scene" data-start="2" data-duration="6">` +
@@ -27,7 +46,8 @@ describe("collectRenderMedia host windows", () => {
     const { videos, audios } = collectRenderMedia(html);
     expect(videos.find((video) => video.id === "local")).toMatchObject({ start: 4, end: 6 });
     expect(videos.find((video) => video.id === "global")).toMatchObject({ start: 2, end: 4 });
-    expect(audios.find((audio) => audio.id === "local-audio")).toMatchObject({ start: 4, end: 0 });
-    expect(audios.find((audio) => audio.id === "global-audio")).toMatchObject({ start: 2, end: 0 });
+    // Open-ended audio tracks close with the host (data-start 2 + data-duration 6).
+    expect(audios.find((audio) => audio.id === "local-audio")).toMatchObject({ start: 4, end: 8 });
+    expect(audios.find((audio) => audio.id === "global-audio")).toMatchObject({ start: 2, end: 8 });
   });
 });
diff --git a/packages/producer/src/services/renderMediaCollector.ts b/packages/producer/src/services/renderMediaCollector.ts
index db890615ce..ec7c2c2c20 100644
--- a/packages/producer/src/services/renderMediaCollector.ts
+++ b/packages/producer/src/services/renderMediaCollector.ts
@@ -41,6 +41,19 @@ import {
  */
 const COMPOSITION_HOST_ATTR = "data-composition-file";
 
+/**
+ * Where a composition host closes, in its parent's time. `data-end` wins; a
+ * host authored with only `data-duration` closes at start + duration — the
+ * same window the runtime uses to hide the host's descendants, so nested
+ * media stops with the scene instead of running to the scene file's end.
+ */
+function resolveHostEnd(host: Element, hostStart: number): number | null {
+  const end = parseNumeric(host.getAttribute("data-end"));
+  if (end != null) return end;
+  const duration = parseNumeric(host.getAttribute("data-duration"));
+  return duration == null ? null : hostStart + duration;
+}
+
 interface HostWindow {
   /** Seconds to add to a descendant's authored, scene-relative start. */
   offset: number;
@@ -84,7 +97,7 @@ function resolveHostWindow(
   // parentElement walks leaf → root; the offsets accumulate root → leaf.
   for (const host of hosts.reverse()) {
     const hostStart = resolveReferencedStart(document, host, startCache, visiting);
-    const hostEnd = parseNumeric(host.getAttribute("data-end"));
+    const hostEnd = resolveHostEnd(host, hostStart);
     if (hostEnd != null) limit = Math.min(limit, offset + hostEnd);
     offset += hostStart;
   }