diff --git a/backend/api/assets_serving.py b/backend/api/assets_serving.py
index 69a1e4e8..b9ad6037 100644
--- a/backend/api/assets_serving.py
+++ b/backend/api/assets_serving.py
@@ -3,6 +3,8 @@ Assets Serving Router
 
 Serves user-uploaded assets (avatars, voice samples) from workspace storage.
 Uses authenticated or query-token access for security.
+Audio MIME types are set correctly based on file extension so browsers
+can play voice clone previews without NotSupportedError.
 """
 
 import os
@@ -12,13 +14,12 @@ from fastapi.responses import FileResponse
 from loguru import logger
 from typing import Dict, Any
 
-from middleware.auth_middleware import get_current_user_with_query_token, get_current_user
+from middleware.auth_middleware import get_current_user_with_query_token
 from api.story_writer.utils.auth import require_authenticated_user
-from utils.storage_paths import get_repo_root
+from utils.storage_paths import get_repo_root, sanitize_user_id
 
 router = APIRouter(prefix="/api/assets", tags=["Assets Serving"])
 
-# MIME type map for common audio/image formats (by file extension)
 MIME_MAP = {
     ".wav": "audio/wav",
     ".mp3": "audio/mpeg",
@@ -38,34 +39,21 @@ MIME_MAP = {
 
 
 def _resolve_asset_path(user_id: str, category: str, filename: str) -> Path:
-    """Resolve an asset file path in the user's workspace.
-
-    Args:
-        user_id: Clerk user ID (already validated)
-        category: Subdirectory under assets/ (e.g. 'avatars', 'voice_samples')
-        filename: The file name (already sanitized)
-
-    Returns:
-        Resolved absolute Path to the asset file.
-    """
-    from utils.storage_paths import sanitize_user_id
-
+    """Resolve asset path in user workspace with path-traversal protection."""
     safe_user_id = sanitize_user_id(user_id)
     repo_root = get_repo_root()
 
-    # Primary path: workspace/workspace_{user_id}/assets/{category}/{filename}
-    primary = (repo_root / "workspace" / f"workspace_{safe_user_id}" / "assets" / category / filename).resolve()
+    file_path = (repo_root / "workspace" / f"workspace_{safe_user_id}" / "assets" / category / filename).resolve()
 
-    # Security: ensure resolved path doesn't escape the workspace
     workspace_dir = (repo_root / "workspace" / f"workspace_{safe_user_id}").resolve()
-    if not str(primary).startswith(str(workspace_dir)):
+    if not str(file_path).startswith(str(workspace_dir)):
         raise HTTPException(status_code=403, detail="Access denied")
 
-    return primary
+    return file_path
 
 
 def _get_media_type(filename: str) -> str:
-    """Determine MIME type from file extension, with a default fallback."""
+    """Determine MIME type from file extension, with fallback."""
     ext = Path(filename).suffix.lower()
     return MIME_MAP.get(ext, "application/octet-stream")
 
@@ -76,14 +64,13 @@ async def serve_avatar(
     filename: str,
     current_user: Dict[str, Any] = Depends(get_current_user_with_query_token),
 ):
-    """Serve avatar images. Supports auth via header or query token for <img> elements."""
+    """Serve avatar images. Supports auth via Authorization header or ?token= query param."""
     require_authenticated_user(current_user)
 
     safe_filename = os.path.basename(filename)
     file_path = _resolve_asset_path(user_id, "avatars", safe_filename)
 
     if not file_path.exists():
-        logger.debug(f"[Assets] Avatar not found: {file_path}")
         raise HTTPException(status_code=404, detail="Asset not found")
 
     media_type = _get_media_type(safe_filename)
@@ -96,16 +83,21 @@ async def serve_voice_sample(
     filename: str,
     current_user: Dict[str, Any] = Depends(get_current_user_with_query_token),
 ):
-    """Serve voice sample audio files. Supports auth via header or query token for <audio> elements."""
+    """Serve voice sample audio files.
+
+    Supports auth via Authorization header or ?token= query param.
+    The ?token= param is essential for <audio> elements and new Audio()
+    which cannot send Authorization headers.
+    """
     require_authenticated_user(current_user)
 
     safe_filename = os.path.basename(filename)
     file_path = _resolve_asset_path(user_id, "voice_samples", safe_filename)
 
     if not file_path.exists():
-        logger.debug(f"[Assets] Voice sample not found: {file_path}")
+        logger.info(f"[Assets] Voice sample not found: {file_path}")
         raise HTTPException(status_code=404, detail="Asset not found")
 
     media_type = _get_media_type(safe_filename)
-    logger.debug(f"[Assets] Serving voice sample: {file_path} ({media_type}, {file_path.stat().st_size} bytes)")
+    logger.info(f"[Assets] Serving voice sample: {safe_filename} ({media_type}, {file_path.stat().st_size} bytes)")
     return FileResponse(file_path, media_type=media_type)
\ No newline at end of file
diff --git a/frontend/src/components/OnboardingWizard/PersonalizationStep/components/TestPersonaModal.tsx b/frontend/src/components/OnboardingWizard/PersonalizationStep/components/TestPersonaModal.tsx
index b7efc9a2..e9d65f0b 100644
--- a/frontend/src/components/OnboardingWizard/PersonalizationStep/components/TestPersonaModal.tsx
+++ b/frontend/src/components/OnboardingWizard/PersonalizationStep/components/TestPersonaModal.tsx
@@ -10,6 +10,7 @@ import {
 import { createAvatarVideoAsync } from '../../../../api/videoStudioApi';
 import { useVideoGenerationPolling } from '../../../../hooks/usePolling';
 import { fetchMediaBlobUrl } from '../../../../utils/fetchMediaBlobUrl';
+import { getAuthTokenGetter } from '../../../../api/client';
 import { VideoCameraFront, SkipNext, PlayArrow, InfoOutlined, Close as CloseIcon, HelpOutline, Refresh, RestartAlt, Undo } from '@mui/icons-material';
 import { VideoGenerationLoader } from '../../../shared/VideoGenerationLoader';
 import { OperationButton } from '../../../shared/OperationButton';
@@ -31,8 +32,33 @@ export const TestPersonaModal: React.FC<TestPersonaModalProps> = ({
   const [model, setModel] = useState<'infinitetalk' | 'hunyuan-avatar'>('infinitetalk');
   const [showCapabilities, setShowCapabilities] = useState(false);
   const [avatarBlobUrl, setAvatarBlobUrl] = useState<string | null>(null);
+  const [authenticatedVoiceUrl, setAuthenticatedVoiceUrl] = useState<string | null>(null);
   const STORAGE_KEY = 'test_persona_video_url';
   const STORAGE_BACKUP_KEY = 'test_persona_video_url_backup';
+
+  // Append auth token to /api/ asset URLs so <audio> can access them
+  useEffect(() => {
+    if (!voiceUrl || !voiceUrl.includes('/api/')) {
+      setAuthenticatedVoiceUrl(voiceUrl || null);
+      return;
+    }
+    let cancelled = false;
+    (async () => {
+      try {
+        const tokenGetter = getAuthTokenGetter();
+        if (tokenGetter) {
+          const token = await tokenGetter();
+          if (token && !cancelled) {
+            const sep = voiceUrl.includes('?') ? '&' : '?';
+            setAuthenticatedVoiceUrl(`${voiceUrl}${sep}token=${encodeURIComponent(token)}`);
+            return;
+          }
+        }
+      } catch { /* fallback */ }
+      if (!cancelled) setAuthenticatedVoiceUrl(voiceUrl);
+    })();
+    return () => { cancelled = true; };
+  }, [voiceUrl]);
   
   const [generatedVideoUrl, setGeneratedVideoUrl] = useState<string | null>(() => {
     try {
@@ -527,7 +553,7 @@ export const TestPersonaModal: React.FC<TestPersonaModalProps> = ({
                         <Typography variant="caption" fontWeight="bold" sx={{ mb: 1, display: 'block', color: '#64748b' }}>
                             Voice Preview
                         </Typography>
-                        <audio controls src={voiceUrl} style={{ width: '100%', height: 36 }} />
+                        <audio controls src={authenticatedVoiceUrl || undefined} style={{ width: '100%', height: 36 }} />
                     </Box>
                 </Stack>
     
diff --git a/frontend/src/components/OnboardingWizard/PersonalizationStep/components/VoiceAvatarPlaceholder.tsx b/frontend/src/components/OnboardingWizard/PersonalizationStep/components/VoiceAvatarPlaceholder.tsx
index ff09cc9a..ee200dfd 100644
--- a/frontend/src/components/OnboardingWizard/PersonalizationStep/components/VoiceAvatarPlaceholder.tsx
+++ b/frontend/src/components/OnboardingWizard/PersonalizationStep/components/VoiceAvatarPlaceholder.tsx
@@ -1,8 +1,9 @@
-import React, { useMemo, useRef, useState, useEffect } from 'react';
+import React, { useMemo, useRef, useState, useEffect, useCallback } from 'react';
 import { Box, Typography, Paper, Stack, Button, Alert, TextField, CircularProgress, Slider, FormControlLabel, Checkbox, MenuItem, Tooltip, Chip, Divider, Grid, IconButton, Modal, Fade, Backdrop, LinearProgress } from '@mui/material';
 import { keyframes } from '@mui/system';
 import { Mic, GraphicEq, Timer, CloudUpload, Stop, PlayArrow, InfoOutlined, TextFields, HelpOutline, AutoAwesome, Campaign, MicNone, Podcasts, RestartAlt, Undo, Headphones, Article, VideoLibrary, TrendingUp, CheckCircle, RecordVoiceOver, Settings } from '@mui/icons-material';
 import { createVoiceClone, createVoiceDesign, getLatestVoiceClone, setBrandVoice } from '../../../../api/brandAssets';
+import { getAuthTokenGetter } from '../../../../api/client';
 import { OperationButton } from '../../../shared/OperationButton';
 
 const pulse = keyframes`
@@ -95,6 +96,32 @@ export const VoiceAvatarPlaceholder: React.FC<{ domainName?: string; onVoiceSet?
     } catch { return null; }
   });
 
+  // Append auth token to /api/ asset URLs so <audio> elements can access them
+  const [authenticatedAudioUrl, setAuthenticatedAudioUrl] = useState<string | null>(null);
+
+  useEffect(() => {
+    if (!resultAudioUrl || !resultAudioUrl.includes('/api/')) {
+      setAuthenticatedAudioUrl(resultAudioUrl);
+      return;
+    }
+    let cancelled = false;
+    (async () => {
+      try {
+        const tokenGetter = getAuthTokenGetter();
+        if (tokenGetter) {
+          const token = await tokenGetter();
+          if (token && !cancelled) {
+            const sep = resultAudioUrl.includes('?') ? '&' : '?';
+            setAuthenticatedAudioUrl(`${resultAudioUrl}${sep}token=${encodeURIComponent(token)}`);
+            return;
+          }
+        }
+      } catch { /* fallback to unauthenticated */ }
+      if (!cancelled) setAuthenticatedAudioUrl(resultAudioUrl);
+    })();
+    return () => { cancelled = true; };
+  }, [resultAudioUrl]);
+
   const [archivedResultAudioUrl, setArchivedResultAudioUrl] = useState<string | null>(() => {
     try {
       const saved = localStorage.getItem(STORAGE_BACKUP_KEY);
@@ -1090,7 +1117,7 @@ export const VoiceAvatarPlaceholder: React.FC<{ domainName?: string; onVoiceSet?
                         <Typography variant="caption" fontWeight="800" sx={{ color: '#EC4899', textTransform: 'uppercase', mb: 0.25, display: 'block', fontSize: '0.65rem' }}>
                           Generated AI Voice Preview
                         </Typography>
-                        <audio controls src={resultAudioUrl} style={{ width: '100%', height: '28px' }} />
+                        <audio controls src={authenticatedAudioUrl || undefined} style={{ width: '100%', height: '28px' }} />
                         <Stack direction="row" spacing={1} sx={{ mt: 1 }}>
                           <Button
                             variant="outlined"
diff --git a/frontend/src/components/shared/VoiceSelector.tsx b/frontend/src/components/shared/VoiceSelector.tsx
index d8d03949..03332b23 100644
--- a/frontend/src/components/shared/VoiceSelector.tsx
+++ b/frontend/src/components/shared/VoiceSelector.tsx
@@ -43,6 +43,7 @@ import {
   Category,
 } from "@mui/icons-material";
 import { getLatestVoiceClone, VoiceCloneResponse } from "../../api/brandAssets";
+import { getAuthTokenGetter } from "../../api/client";
 import { VoiceAvatarPlaceholder } from "../OnboardingWizard/PersonalizationStep/components/VoiceAvatarPlaceholder";
 
 export type VoiceOption = {
@@ -235,7 +236,7 @@ export const VoiceSelector: React.FC<VoiceSelectorProps> = ({
     }
   }, []);
 
-  const handlePreview = useCallback((voice: VoiceOption) => {
+  const handlePreview = useCallback(async (voice: VoiceOption) => {
     if (!voice.previewUrl) return;
 
     if (playingPreview === voice.id) {
@@ -247,7 +248,22 @@ export const VoiceSelector: React.FC<VoiceSelectorProps> = ({
     stopCurrentAudio();
     setPlayingPreview(voice.id);
 
-    const audio = new Audio(voice.previewUrl);
+    // Append auth token for endpoints that require it (e.g. /api/assets/)
+    let previewUrl = voice.previewUrl;
+    try {
+      const tokenGetter = getAuthTokenGetter();
+      if (tokenGetter) {
+        const token = await tokenGetter();
+        if (token && previewUrl.includes('/api/')) {
+          const separator = previewUrl.includes('?') ? '&' : '?';
+          previewUrl = `${previewUrl}${separator}token=${encodeURIComponent(token)}`;
+        }
+      }
+    } catch (e) {
+      // Token retrieval failed — try URL without token
+    }
+
+    const audio = new Audio(previewUrl);
     audioRef.current = audio;
 
     audio.onerror = () => {