diff --git a/extension/content/inject.js b/extension/content/inject.js
index b12447d..00831ea 100644
--- a/extension/content/inject.js
+++ b/extension/content/inject.js
@@ -3144,6 +3144,12 @@ function setupControllerHostTracking(videoController, wrapper, mount) {
     resizeObserver.observe(geometryMount);
   }
 
+  var mediaGeometryEvents = ["loadedmetadata", "play", "playing"];
+  mediaGeometryEvents.forEach(function(eventName) {
+    videoController.video.addEventListener(eventName, schedule, {
+      passive: true
+    });
+  });
   win.addEventListener("resize", schedule, { passive: true });
   doc.addEventListener("fullscreenchange", schedule, { passive: true });
   geometryMount.addEventListener("scroll", schedule, { passive: true });
@@ -3154,6 +3160,9 @@ function setupControllerHostTracking(videoController, wrapper, mount) {
     if (resizeObserver) resizeObserver.disconnect();
     if (frameId !== null) win.cancelAnimationFrame(frameId);
     if (geometryRetryTimer !== null) win.clearTimeout(geometryRetryTimer);
+    mediaGeometryEvents.forEach(function(eventName) {
+      videoController.video.removeEventListener(eventName, schedule);
+    });
     win.removeEventListener("resize", schedule);
     doc.removeEventListener("fullscreenchange", schedule);
     geometryMount.removeEventListener("scroll", schedule);
@@ -3329,8 +3338,15 @@ function syncControllerFullscreenMount(videoController) {
       (fullscreenElement === video ||
         isComposedDescendant(video, fullscreenElement))
   );
+  var normalGeometryMount = getControllerGeometryMount(targetMount);
+  var normalMountIsAlreadyFullscreenVisible = Boolean(
+    fullscreenElement &&
+      fullscreenElement !== video &&
+      normalGeometryMount &&
+      isComposedDescendant(normalGeometryMount, fullscreenElement)
+  );
 
-  if (ownsFullscreen) {
+  if (ownsFullscreen && !normalMountIsAlreadyFullscreenVisible) {
     targetMount = getControllerMount(video, fullscreenElement);
   } else if (!fullscreenElement && (!targetMount || !targetMount.isConnected)) {
     targetMount = getControllerMount(video);
@@ -3950,6 +3966,9 @@ function defineVideoController() {
     const speed = this.video.playbackRate.toFixed(2);
     var wrapper = doc.createElement("div");
     wrapper.classList.add("vsc-controller");
+    // Keep the host out of player layout while its shadow stylesheet loads.
+    wrapper.style.position = "absolute";
+    wrapper.style.pointerEvents = "none";
     if (!hasUsableMediaSource(this.video))
       wrapper.classList.add("vsc-nosource");
     if (tc.settings.startHidden) wrapper.classList.add("vsc-hidden");
diff --git a/extension/content/shadow.css b/extension/content/shadow.css
index ac542a0..f25f323 100644
--- a/extension/content/shadow.css
+++ b/extension/content/shadow.css
@@ -1,9 +1,5 @@
 :host {
   position: absolute !important;
-  top: 0 !important;
-  left: 0 !important;
-  width: 100% !important;
-  height: 100% !important;
   pointer-events: none !important;
   z-index: 2147483647 !important;
   white-space: normal;
@@ -15,7 +11,6 @@
    base absolute host rule. */
 :host(.vsc-fullscreen-popover) {
   position: fixed !important;
-  inset: auto !important;
   margin: 0 !important;
   padding: 0 !important;
   border: 0 !important;
diff --git a/tests/inject-lifecycle.regression.test.js b/tests/inject-lifecycle.regression.test.js
index 7b5d52d..b847272 100644
--- a/tests/inject-lifecycle.regression.test.js
+++ b/tests/inject-lifecycle.regression.test.js
@@ -2,7 +2,8 @@ const {
   createChromeMock,
   evaluateScript,
   flushAsyncWork,
-  loadHtmlString
+  loadHtmlString,
+  readWorkspaceFile
 } = require("./helpers/extension-test-utils");
 
 function bootInject(options) {
@@ -280,6 +281,45 @@ describe("inject.js media/controller lifecycle regressions", () => {
     expect(video.vsc.div.style.getPropertyValue("height")).toBe("226px");
   });
 
+  it("does not let shadow host defaults override measured geometry", () => {
+    const shadowCss = readWorkspaceFile("extension/content/shadow.css");
+    const hostRule = shadowCss.match(/:host\s*\{([^}]*)\}/)[1];
+    const fullscreenRule = shadowCss.match(
+      /:host\(\.vsc-fullscreen-popover\)\s*\{([^}]*)\}/
+    )[1];
+
+    expect(hostRule).not.toMatch(/\b(?:top|left|width|height)\s*:/);
+    expect(fullscreenRule).not.toMatch(/\binset\s*:/);
+  });
+
+  it("repositions a Shorts controller when playback moves the video on-screen", async () => {
+    vi.useFakeTimers();
+    bootInject({ url: "https://www.youtube.com/shorts/example" });
+    await settleLifecycle();
+
+    const player = document.createElement("div");
+    player.className = "html5-video-player";
+    const video = document.createElement("video");
+    const playerRect = makeRect(40, 64, 351, 624);
+    let videoRect = makeRect(40, -560, 351, 624);
+
+    setRect(player, playerRect);
+    setBoxMetrics(player, playerRect.width, playerRect.height);
+    video.getBoundingClientRect = () => videoRect;
+    video.src = "blob:https://www.youtube.com/shorts";
+    player.appendChild(video);
+    document.body.appendChild(player);
+
+    window.ensureController(video, player);
+    expect(video.vsc.div.style.getPropertyValue("top")).toBe("-624px");
+
+    videoRect = playerRect;
+    video.dispatchEvent(new Event("playing"));
+    await vi.advanceTimersByTimeAsync(0);
+
+    expect(video.vsc.div.style.getPropertyValue("top")).toBe("0px");
+  });
+
   it("targets the controller nearest the pointer unless change-all is selected", async () => {
     bootInject();
     await settleLifecycle();
@@ -638,6 +678,25 @@ describe("inject.js media/controller lifecycle regressions", () => {
     controller.controllerHostCleanup();
   });
 
+  it("keeps a visible player-local host when Firefox fullscreens the page root", async () => {
+    bootInject();
+    await settleLifecycle();
+
+    const { mount, controller, wrapper } = createControlledVideo();
+    setRect(document.documentElement, makeRect(0, 0, 0, 0));
+    Object.defineProperty(document, "fullscreenElement", {
+      configurable: true,
+      value: document.documentElement
+    });
+
+    window.syncControllerFullscreenMount(controller);
+
+    expect(wrapper.parentElement).toBe(mount);
+    expect(wrapper.classList.contains("vsc-geometry-hidden")).toBe(false);
+    expect(document.documentElement.style.position).toBe("");
+    expect(document.documentElement.style.isolation).toBe("");
+  });
+
   it("only promotes the directly-fullscreen video's controller", async () => {
     bootInject();
     await settleLifecycle();