diff --git a/src/frontend/src/features/rooms/livekit/components/DocumentPiPPortal.tsx b/src/frontend/src/features/rooms/livekit/components/DocumentPiPPortal.tsx
index 9dfbc1ff..561c62c5 100644
--- a/src/frontend/src/features/rooms/livekit/components/DocumentPiPPortal.tsx
+++ b/src/frontend/src/features/rooms/livekit/components/DocumentPiPPortal.tsx
@@ -36,25 +36,63 @@ const syncThemeAttribute = (source: Document, target: Document) => {
   }
 }
 
+const cssVarNameCacheByElement = new WeakMap<HTMLElement, string[]>()
+const cssVarNameCacheByUri = new Map<string, string[]>()
+
 const syncCssVariables = (source: Document, target: Document) => {
   const sourceView = source.defaultView
   if (!sourceView) return
 
-  const applyVarsFrom = (element: HTMLElement | null) => {
-    if (!element) return
-    const styles = sourceView.getComputedStyle(element)
-    for (let i = 0; i < styles.length; i += 1) {
-      const property = styles[i]
-      if (!property.startsWith('--')) continue
-      const value = styles.getPropertyValue(property)
-      if (value) {
-        target.documentElement.style.setProperty(property, value)
+  const getCachedVarNames = () => {
+    const docEl = source.documentElement
+    if (!docEl) return []
+
+    const cachedByElement = cssVarNameCacheByElement.get(docEl)
+    if (cachedByElement) return cachedByElement
+
+    const cachedByUri = source.baseURI
+      ? cssVarNameCacheByUri.get(source.baseURI)
+      : undefined
+    if (cachedByUri) return cachedByUri
+
+    const varNames = new Set<string>()
+    const collectVarsFrom = (element: HTMLElement | null) => {
+      if (!element) return
+      const styles = sourceView.getComputedStyle(element)
+      for (let i = 0; i < styles.length; i += 1) {
+        const property = styles[i]
+        if (property.startsWith('--')) {
+          varNames.add(property)
+        }
       }
     }
+
+    collectVarsFrom(source.documentElement)
+    collectVarsFrom(source.body)
+
+    const result = Array.from(varNames)
+    cssVarNameCacheByElement.set(docEl, result)
+    if (source.baseURI) {
+      cssVarNameCacheByUri.set(source.baseURI, result)
+    }
+    return result
   }
 
-  applyVarsFrom(source.documentElement)
-  applyVarsFrom(source.body)
+  const varNames = getCachedVarNames()
+  if (!varNames.length) return
+
+  const rootStyles = sourceView.getComputedStyle(source.documentElement)
+  const bodyStyles = source.body
+    ? sourceView.getComputedStyle(source.body)
+    : null
+
+  varNames.forEach((property) => {
+    const bodyValue = bodyStyles?.getPropertyValue(property)
+    const value = bodyValue || rootStyles.getPropertyValue(property)
+    if (value) {
+      target.documentElement.style.setProperty(property, value)
+    }
+  })
 }
 
 /**
diff --git a/src/frontend/src/features/rooms/livekit/hooks/useDocumentPiP.ts b/src/frontend/src/features/rooms/livekit/hooks/useDocumentPiP.ts
index 1b4315de..1632ccd8 100644
--- a/src/frontend/src/features/rooms/livekit/hooks/useDocumentPiP.ts
+++ b/src/frontend/src/features/rooms/livekit/hooks/useDocumentPiP.ts
@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useMemo, useState } from 'react'
+import { useCallback, useEffect, useRef, useState } from 'react'
 
 type DocumentPictureInPicture = {
   requestWindow: (options?: {
@@ -19,24 +19,44 @@ export const useDocumentPiP = ({
   height?: number
 } = {}) => {
   const [pipWindow, setPipWindow] = useState<Window | null>(null)
+  const pipWindowRef = useRef<Window | null>(null)
+  const pendingPiPRef = useRef<Promise<Window | null> | null>(null)
 
-  const isSupported = useMemo(() => {
+  const [isSupported] = useState(() => {
     if (typeof window === 'undefined') return false
     return 'documentPictureInPicture' in window
-  }, [])
+  })
 
   const openPiP = useCallback(async () => {
     if (!isSupported) return null
-    if (pipWindow && !pipWindow.closed) return pipWindow
+    const existingWindow = pipWindowRef.current
+    if (existingWindow && !existingWindow.closed) return existingWindow
+
+    if (pendingPiPRef.current) return pendingPiPRef.current
 
     // Request a new PiP window from the browser API.
     const pip = (window as WindowWithDocumentPiP).documentPictureInPicture
     if (!pip) return null
 
-    const win = await pip.requestWindow({ width, height })
-    setPipWindow(win)
-    return win
-  }, [height, isSupported, pipWindow, width])
+    const requestPromise = (async () => {
+      try {
+        const win = await pip.requestWindow({ width, height })
+        const currentWindow = pipWindowRef.current
+        if (currentWindow && !currentWindow.closed) return currentWindow
+        setPipWindow(win)
+        return win
+      } catch (error) {
+        // Avoid unhandled rejections if the user blocks or closes the request.
+        console.error('Failed to open Picture-in-Picture window', error)
+        return null
+      } finally {
+        pendingPiPRef.current = null
+      }
+    })()
+
+    pendingPiPRef.current = requestPromise
+    return requestPromise
+  }, [height, isSupported, width])
 
   const closePiP = useCallback(() => {
     if (!pipWindow) return
@@ -46,6 +66,10 @@ export const useDocumentPiP = ({
     setPipWindow(null)
   }, [pipWindow])
 
+  useEffect(() => {
+    pipWindowRef.current = pipWindow
+  }, [pipWindow])
+
   useEffect(() => {
     if (!pipWindow) return
 
diff --git a/src/frontend/src/primitives/useOverlayPortalContainer.tsx b/src/frontend/src/primitives/useOverlayPortalContainer.tsx
index e8e93032..58e5f5d6 100644
--- a/src/frontend/src/primitives/useOverlayPortalContainer.tsx
+++ b/src/frontend/src/primitives/useOverlayPortalContainer.tsx
@@ -17,8 +17,5 @@ export const useOverlayPortalContainer = () => {
  */
 export const useOverlayBoundaryElement = () => {
   const portalContainer = useOverlayPortalContainer()
-  return useMemo(() => {
-    if (portalContainer) return portalContainer
-    return undefined
-  }, [portalContainer])
+  return portalContainer
 }