diff --git a/backend/app/services/video_renderer.py b/backend/app/services/video_renderer.py
index 83d518a..48dc3d2 100644
--- a/backend/app/services/video_renderer.py
+++ b/backend/app/services/video_renderer.py
@@ -55,7 +55,7 @@ class VideoRendererService:
         self.duck_level = getattr(settings, 'accessible_video_duck_level', 0.3)
         self.duck_fade_ms = getattr(settings, 'accessible_video_duck_fade_ms', 200)
         # Cloud Run support
-        self._http_client: httpx.Client | None = None
+        self._http_client: httpx.AsyncClient | None = None
         self._gcs_client: storage.Client | None = None
         # Source video caching for Cloud Run (uploaded once, reused across operations)
         self._cached_source_gcs_uri: str | None = None
@@ -65,11 +65,11 @@ class VideoRendererService:
         """Check if Cloud Run FFmpeg service is configured."""
         return bool(settings.ffmpeg_service_url)
 
-    def _get_http_client(self) -> httpx.Client:
-        """Get or create HTTP client for Cloud Run calls."""
+    def _get_http_client(self) -> httpx.AsyncClient:
+        """Get or create async HTTP client for Cloud Run calls."""
         if self._http_client is None:
             # 10-minute timeout for long FFmpeg operations
-            self._http_client = httpx.Client(timeout=600.0)
+            self._http_client = httpx.AsyncClient(timeout=600.0)
         return self._http_client
 
     def _get_gcs_client(self) -> storage.Client:
@@ -158,7 +158,7 @@ class VideoRendererService:
             # Log but don't fail on cleanup errors
             logger.warning(f"Failed to delete GCS temp file {gcs_uri}: {e}")
 
-    def _call_cloud_run_probe(self, gcs_uri: str) -> dict[str, Any]:
+    async def _call_cloud_run_probe(self, gcs_uri: str) -> dict[str, Any]:
         """
         Call Cloud Run FFmpeg service /probe endpoint.
 
@@ -172,7 +172,7 @@ class VideoRendererService:
         service_url = settings.ffmpeg_service_url.rstrip("/")
         auth_token = _get_cloud_run_id_token(service_url)
 
-        response = client.post(
+        response = await client.post(
             f"{service_url}/probe",
             json={"gcs_uri": gcs_uri},  # Matches ProbeRequest model
             headers={"Authorization": f"Bearer {auth_token}"}
@@ -180,7 +180,7 @@ class VideoRendererService:
         response.raise_for_status()
         return response.json()
 
-    def _call_cloud_run_endpoint(
+    async def _call_cloud_run_endpoint(
         self,
         endpoint: str,
         payload: dict[str, Any],
@@ -202,7 +202,7 @@ class VideoRendererService:
         auth_token = _get_cloud_run_id_token(service_url)
 
         try:
-            response = client.post(
+            response = await client.post(
                 f"{service_url}{endpoint}",
                 json=payload,
                 headers={"Authorization": f"Bearer {auth_token}"}
@@ -715,7 +715,7 @@ class VideoRendererService:
             gcs_uri = self._upload_to_gcs_temp(video_path, "probe")
 
         try:
-            result = self._call_cloud_run_probe(gcs_uri)
+            result = await self._call_cloud_run_probe(gcs_uri)
             return result["duration"]
         finally:
             # Clean up if we uploaded specifically for this call
@@ -781,7 +781,7 @@ class VideoRendererService:
             gcs_uri = self._upload_to_gcs_temp(video_path, "probe")
 
         try:
-            result = self._call_cloud_run_probe(gcs_uri)
+            result = await self._call_cloud_run_probe(gcs_uri)
 
             # Defaults
             props = {
@@ -910,7 +910,7 @@ class VideoRendererService:
         output_gcs_uri = f"gs://{settings.gcs_bucket}/temp/ffmpeg/segment/{uuid4().hex}/segment.mp4"
 
         try:
-            self._call_cloud_run_endpoint(
+            await self._call_cloud_run_endpoint(
                 "/encode-segment",
                 {
                     "source_gcs_uri": self._cached_source_gcs_uri,
@@ -968,7 +968,7 @@ class VideoRendererService:
         output_gcs_uri = f"gs://{settings.gcs_bucket}/temp/ffmpeg/frame/{uuid4().hex}/frame.png"
 
         try:
-            self._call_cloud_run_endpoint(
+            await self._call_cloud_run_endpoint(
                 "/extract-frame",
                 {
                     "source_gcs_uri": self._cached_source_gcs_uri,
@@ -1116,7 +1116,7 @@ class VideoRendererService:
         output_gcs_uri = f"gs://{settings.gcs_bucket}/temp/ffmpeg/freeze/{uuid4().hex}/freeze.mp4"
 
         try:
-            self._call_cloud_run_endpoint(
+            await self._call_cloud_run_endpoint(
                 "/create-freeze-segment",
                 {
                     "frame_gcs_uri": frame_gcs_uri,
@@ -1292,7 +1292,7 @@ class VideoRendererService:
                 "{output}"
             ])
 
-            self._call_cloud_run_endpoint(
+            await self._call_cloud_run_endpoint(
                 "/run-ffmpeg",
                 {
                     "input_gcs_uris": audio_gcs_uris,
@@ -1366,7 +1366,7 @@ class VideoRendererService:
 
         try:
             channel_layout = "stereo" if props["channels"] == "2" else "mono"
-            self._call_cloud_run_endpoint(
+            await self._call_cloud_run_endpoint(
                 "/run-ffmpeg",
                 {
                     "input_gcs_uris": [],  # No input files, using lavfi
@@ -1442,7 +1442,7 @@ class VideoRendererService:
         output_gcs_uri = f"gs://{settings.gcs_bucket}/temp/ffmpeg/concat/{uuid4().hex}/final.mp4"
 
         try:
-            self._call_cloud_run_endpoint(
+            await self._call_cloud_run_endpoint(
                 "/concatenate",
                 {
                     "segment_gcs_uris": segment_gcs_uris,