diff --git a/app/application/image.py b/app/application/image.py
index bc9292273..23d2e4477 100644
--- a/app/application/image.py
+++ b/app/application/image.py
@@ -2,6 +2,7 @@ import io
 import threading
 from collections.abc import Mapping
 from dataclasses import dataclass
+from hashlib import sha256
 from pathlib import Path
 from typing import Any, Callable, List, Optional, Protocol
 
@@ -15,6 +16,8 @@ from app.runtime.log import logger
 
 WallpaperProvider = Callable[[], Optional[str]]
 WallpaperListProvider = Callable[[int], List[str]]
+_IMAGE_CACHE_PATH_PREFIX = "proxy_"
+_IMAGE_CACHE_HASH_LENGTH = 16
 
 
 @dataclass(frozen=True, slots=True)
@@ -373,9 +376,16 @@ class ImageHelper(metaclass=Singleton):
 
     @staticmethod
     def _prepare_cache_path(url: str) -> str:
-        """缓存路径"""
-        sanitized_path = SecurityUtils.sanitize_url_path(url)
-        cache_path = Path(sanitized_path)
+        """
+        根据图片 URL 生成缓存路径。
+
+        根路径或其他无有效文件名的 URL 使用完整 URL 的短哈希兜底，避免
+        `Path.with_suffix()` 对空路径抛出异常，并保证不同 URL 不共用该缓存名。
+        """
+        cache_path = Path(SecurityUtils.sanitize_url_path(url))
+        if not cache_path.name:
+            hash_value = sha256(url.encode()).hexdigest()[:_IMAGE_CACHE_HASH_LENGTH]
+            cache_path = Path(f"{_IMAGE_CACHE_PATH_PREFIX}{hash_value}")
         if not cache_path.suffix:
             cache_path = cache_path.with_suffix(".jpg")
         return cache_path.as_posix()
diff --git a/tests/test_system_image_proxy.py b/tests/test_system_image_proxy.py
index 077a5aa25..d0ab85ba6 100644
--- a/tests/test_system_image_proxy.py
+++ b/tests/test_system_image_proxy.py
@@ -1,6 +1,7 @@
 import asyncio
 import io
 from collections.abc import Iterator, Mapping
+from hashlib import sha256
 from types import SimpleNamespace
 from typing import Any, Optional
 from unittest.mock import AsyncMock, Mock, patch
@@ -238,6 +239,21 @@ def test_async_fetch_image_with_mime_type_validates_network_content_once():
     assert transport.async_calls[0][0] == "https://images.example/wallpaper.png"
 
 
+@pytest.mark.parametrize(
+    "url",
+    [
+        "https://example.com",
+        "https://example.com/",
+        "https://example.com/?param=value",
+    ],
+)
+def test_prepare_cache_path_uses_url_hash_for_urls_without_path(url: str) -> None:
+    """没有有效路径的图片 URL 应生成稳定合法的缓存文件名。"""
+    expected_hash = sha256(url.encode()).hexdigest()[:16]
+
+    assert ImageHelper._prepare_cache_path(url) == f"proxy_{expected_hash}.jpg"
+
+
 def test_image_request_uses_internal_address_port_for_proxy_decision(monkeypatch):
     """自动代理策略必须通过注入端口判断内部地址。"""
     internal_address = _FakeInternalAddress(internal=True)