diff --git a/api/configs/feature/__init__.py b/api/configs/feature/__init__.py
index df15b92c35..963fcbedf9 100644
--- a/api/configs/feature/__init__.py
+++ b/api/configs/feature/__init__.py
@@ -237,6 +237,13 @@ class FileAccessConfig(BaseSettings):
         default="",
     )
 
+    INTERNAL_FILES_URL: str = Field(
+        description="Internal base URL for file access within Docker network,"
+        " used for plugin daemon and internal service communication."
+        " Falls back to FILES_URL if not specified.",
+        default="",
+    )
+
     FILES_ACCESS_TIMEOUT: int = Field(
         description="Expiration time in seconds for file access URLs",
         default=300,
diff --git a/api/core/file/helpers.py b/api/core/file/helpers.py
index 73fabdb11b..335ad2266a 100644
--- a/api/core/file/helpers.py
+++ b/api/core/file/helpers.py
@@ -21,7 +21,9 @@ def get_signed_file_url(upload_file_id: str) -> str:
 
 
 def get_signed_file_url_for_plugin(filename: str, mimetype: str, tenant_id: str, user_id: str) -> str:
-    url = f"{dify_config.FILES_URL}/files/upload/for-plugin"
+    # Plugin access should use internal URL for Docker network communication
+    base_url = dify_config.INTERNAL_FILES_URL or dify_config.FILES_URL
+    url = f"{base_url}/files/upload/for-plugin"
 
     if user_id is None:
         user_id = "DEFAULT-USER"
diff --git a/api/core/tools/signature.py b/api/core/tools/signature.py
index e80005d7bf..f46e669a68 100644
--- a/api/core/tools/signature.py
+++ b/api/core/tools/signature.py
@@ -5,13 +5,12 @@ import os
 import time
 
 from configs import dify_config
-
-
 def sign_tool_file(tool_file_id: str, extension: str) -> str:
     """
-    sign file to get a temporary url
+    sign file to get a temporary url for plugin access
     """
-    base_url = dify_config.FILES_URL
+    # Use internal URL for plugin/tool file access in Docker environments
+    base_url = dify_config.INTERNAL_FILES_URL or dify_config.FILES_URL
     file_preview_url = f"{base_url}/files/tools/{tool_file_id}{extension}"
 
     timestamp = str(int(time.time()))
diff --git a/api/core/tools/tool_file_manager.py b/api/core/tools/tool_file_manager.py
index b849f51064..47b66b9fe8 100644
--- a/api/core/tools/tool_file_manager.py
+++ b/api/core/tools/tool_file_manager.py
@@ -19,6 +19,7 @@ from extensions.ext_storage import storage
 from models.model import MessageFile
 from models.tools import ToolFile
 
+
 logger = logging.getLogger(__name__)
 
 from sqlalchemy.engine import Engine
@@ -35,9 +36,10 @@ class ToolFileManager:
     @staticmethod
     def sign_file(tool_file_id: str, extension: str) -> str:
         """
-        sign file to get a temporary url
+        sign file to get a temporary url for plugin access
         """
-        base_url = dify_config.FILES_URL
+        # Use internal URL for plugin/tool file access in Docker environments
+        base_url = dify_config.INTERNAL_FILES_URL or dify_config.FILES_URL
         file_preview_url = f"{base_url}/files/tools/{tool_file_id}{extension}"
 
         timestamp = str(int(time.time()))