diff --git a/video-gen-api/app/services/private_portrait/ark_client.py b/video-gen-api/app/services/private_portrait/ark_client.py
index fe59f17e..8b6b3a35 100644
--- a/video-gen-api/app/services/private_portrait/ark_client.py
+++ b/video-gen-api/app/services/private_portrait/ark_client.py
@@ -4,6 +4,8 @@ import asyncio
 import json
 from typing import Any
 
+from fastapi import HTTPException
+
 from app.config import settings
 from app.enums.private_portrait import (
     ARK_PRIVATE_PORTRAIT_HOST,
@@ -135,13 +137,31 @@ class ArkPrivateAssetClient:
             credentials,
             10,
             60,
+            "https",
         )
-        api_info = {action.value: ApiInfo("POST", "/", f"Action={action.value}&Version={ARK_PRIVATE_PORTRAIT_VERSION}", {}, {})}
+        # volcengine SDK 的 ApiInfo.query 必须是 dict，不能传 "Action=xxx&Version=xxx" 字符串。
+        # ServiceInfo 默认 scheme='http'，这里必须显式传 https，避免请求走 http://host:80。
+        api_info = {
+            action.value: ApiInfo(
+                "POST",
+                "/",
+                {"Action": action.value, "Version": ARK_PRIVATE_PORTRAIT_VERSION},
+                {},
+                {},
+            )
+        }
         service = Service(service_info, api_info)
+
+        # volcengine SDK 在签名阶段会对 request.body 做 hashlib.sha256(body)。
+        # Python 3 下 hashlib.sha256 只能接收 bytes/bytearray，不能接收 dict 或 str。
+        body = json.dumps(payload, ensure_ascii=False, separators=(",", ":")).encode("utf-8")
         try:
-            raw = service.json(action.value, {}, json.dumps(payload, ensure_ascii=False, separators=(",", ":")))
-        except TypeError:
-            raw = service.json(action.value, {}, payload)
+            raw = service.json(action.value, {}, body)
+        except Exception as exc:
+            message = self._exception_message(exc)
+            if "ConnectTimeout" in message or "timed out" in message or "Connection" in message:
+                raise HTTPException(status_code=502, detail=f"火山私域素材接口连接失败：{message}") from exc
+            raise ArkPrivateAssetClientError(f"{action.value} 请求火山私域素材接口异常：{message}") from exc
 
         resp = self._normalize_response(raw)
         metadata = resp.get("ResponseMetadata") if isinstance(resp, dict) else None
@@ -162,6 +182,15 @@ class ArkPrivateAssetClient:
             return resp
         return {"raw": resp, "RequestId": request_id}
 
+    @staticmethod
+    def _exception_message(exc: Exception) -> str:
+        if exc.args:
+            raw = exc.args[0]
+            if isinstance(raw, (bytes, bytearray)):
+                return raw.decode("utf-8", errors="ignore")
+            return str(raw)
+        return str(exc)
+
     @staticmethod
     def _normalize_response(raw: Any) -> dict[str, Any]:
         if raw is None: