diff --git a/src/config/__init__.py b/src/config/__init__.py
index 54bf87c..104a580 100644
--- a/src/config/__init__.py
+++ b/src/config/__init__.py
@@ -1,6 +1,7 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
+from .loader import load_yaml_config
 from .tools import SELECTED_SEARCH_ENGINE, SearchEngine
 from .questions import BUILT_IN_QUESTIONS, BUILT_IN_QUESTIONS_ZH_CN
 
@@ -45,4 +46,5 @@ __all__ = [
     "SearchEngine",
     "BUILT_IN_QUESTIONS",
     "BUILT_IN_QUESTIONS_ZH_CN",
+    load_yaml_config,
 ]
diff --git a/src/crawler/crawler.py b/src/crawler/crawler.py
index 9f3632d..01a2a6e 100644
--- a/src/crawler/crawler.py
+++ b/src/crawler/crawler.py
@@ -1,7 +1,6 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import sys
 
 from .article import Article
 from .jina_client import JinaClient
diff --git a/src/llms/llm.py b/src/llms/llm.py
index 15ba13b..aa78961 100644
--- a/src/llms/llm.py
+++ b/src/llms/llm.py
@@ -4,7 +4,6 @@
 from pathlib import Path
 from typing import Any, Dict
 import os
-import ssl
 import httpx
 
 from langchain_openai import ChatOpenAI
diff --git a/src/prompt_enhancer/graph/enhancer_node.py b/src/prompt_enhancer/graph/enhancer_node.py
index de7da03..8261d38 100644
--- a/src/prompt_enhancer/graph/enhancer_node.py
+++ b/src/prompt_enhancer/graph/enhancer_node.py
@@ -3,11 +3,11 @@
 
 import logging
 
-from langchain.schema import HumanMessage, SystemMessage
+from langchain.schema import HumanMessage
 
 from src.config.agents import AGENT_LLM_MAP
 from src.llms.llm import get_llm_by_type
-from src.prompts.template import env, apply_prompt_template
+from src.prompts.template import apply_prompt_template
 from src.prompt_enhancer.graph.state import PromptEnhancerState
 
 logger = logging.getLogger(__name__)
diff --git a/src/rag/vikingdb_knowledge_base.py b/src/rag/vikingdb_knowledge_base.py
index 4f2672f..9c235e7 100644
--- a/src/rag/vikingdb_knowledge_base.py
+++ b/src/rag/vikingdb_knowledge_base.py
@@ -48,12 +48,12 @@ class VikingDBKnowledgeBaseProvider(Retriever):
         if params:
             for key in params:
                 if (
-                    type(params[key]) == int
-                    or type(params[key]) == float
-                    or type(params[key]) == bool
+                    type(params[key]) is int
+                    or type(params[key]) is float
+                    or type(params[key]) is bool
                 ):
                     params[key] = str(params[key])
-                elif type(params[key]) == list:
+                elif type(params[key]) is list:
                     if not doseq:
                         params[key] = ",".join(params[key])
 
diff --git a/src/tools/search.py b/src/tools/search.py
index 3f9f2bf..8852ea0 100644
--- a/src/tools/search.py
+++ b/src/tools/search.py
@@ -1,7 +1,6 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import json
 import logging
 import os
 from typing import List, Optional
diff --git a/tests/integration/test_nodes.py b/tests/integration/test_nodes.py
index 8f95e89..2eb3b71 100644
--- a/tests/integration/test_nodes.py
+++ b/tests/integration/test_nodes.py
@@ -1,9 +1,7 @@
 from collections import namedtuple
 import json
 import pytest
-import asyncio
-import types
-from unittest.mock import patch, MagicMock, AsyncMock
+from unittest.mock import patch, MagicMock
 from src.graph.nodes import planner_node
 from src.graph.nodes import human_feedback_node
 from src.graph.nodes import coordinator_node
@@ -39,7 +37,7 @@ def mock_state():
 @pytest.fixture
 def mock_configurable():
     mock = MagicMock()
-    mock.max_search_results = 5
+    mock.max_search_results = 7
     return mock
 
 
@@ -668,8 +666,6 @@ def test_coordinator_node_tool_calls_exception_handling(
     patch_handoff_to_planner,
     patch_logger,
 ):
-    # tool_calls raises exception in processing
-    tool_calls = [{"name": "handoff_to_planner", "args": None}]
     with (
         patch("src.graph.nodes.AGENT_LLM_MAP", {"coordinator": "basic"}),
         patch("src.graph.nodes.get_llm_by_type") as mock_get_llm,
@@ -1037,24 +1033,6 @@ async def test_execute_agent_step_recursion_limit_env_negative(
         )
 
 
-@pytest.fixture
-def mock_state_with_steps(mock_step, mock_completed_step):
-    # Simulate a plan with one completed and one unexecuted step
-    Plan = MagicMock()
-    Plan.steps = [mock_completed_step, mock_step]
-    return {
-        "current_plan": Plan,
-        "observations": ["obs1"],
-        "locale": "en-US",
-        "resources": [],
-    }
-
-
-@pytest.fixture
-def mock_config():
-    return MagicMock()
-
-
 @pytest.fixture
 def mock_configurable_with_mcp():
     mock = MagicMock()
@@ -1297,27 +1275,6 @@ def mock_state_without_resources():
     return {"other": "value"}
 
 
-@pytest.fixture
-def mock_config():
-    return MagicMock()
-
-
-@pytest.fixture
-def mock_configurable():
-    mock = MagicMock()
-    mock.max_search_results = 7
-    return mock
-
-
-@pytest.fixture
-def patch_config_from_runnable_config(mock_configurable):
-    with patch(
-        "src.graph.nodes.Configuration.from_runnable_config",
-        return_value=mock_configurable,
-    ):
-        yield
-
-
 @pytest.fixture
 def patch_get_web_search_tool():
     with patch("src.graph.nodes.get_web_search_tool") as mock:
diff --git a/tests/test_state.py b/tests/test_state.py
index c25b77b..598ba1c 100644
--- a/tests/test_state.py
+++ b/tests/test_state.py
@@ -1,7 +1,6 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import pytest
 import sys
 import os
 from typing import Annotated
diff --git a/tests/unit/config/test_configuration.py b/tests/unit/config/test_configuration.py
index a70aa79..b499b57 100644
--- a/tests/unit/config/test_configuration.py
+++ b/tests/unit/config/test_configuration.py
@@ -1,13 +1,8 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import os
-import pytest
 import sys
 import types
-from pathlib import Path
-import builtins
-import importlib
 from src.config.configuration import Configuration
 
 # Patch sys.path so relative import works
diff --git a/tests/unit/config/test_loader.py b/tests/unit/config/test_loader.py
index aaf75af..3d5538d 100644
--- a/tests/unit/config/test_loader.py
+++ b/tests/unit/config/test_loader.py
@@ -3,8 +3,6 @@
 
 import os
 import tempfile
-import yaml
-import pytest
 from src.config.loader import load_yaml_config, process_dict, replace_env_vars
 
 
diff --git a/tests/unit/crawler/test_article.py b/tests/unit/crawler/test_article.py
index b2aa918..d9bd384 100644
--- a/tests/unit/crawler/test_article.py
+++ b/tests/unit/crawler/test_article.py
@@ -1,6 +1,5 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
-import pytest
 from src.crawler.article import Article
 
 
diff --git a/tests/unit/crawler/test_crawler_class.py b/tests/unit/crawler/test_crawler_class.py
index eba2148..6f6429a 100644
--- a/tests/unit/crawler/test_crawler_class.py
+++ b/tests/unit/crawler/test_crawler_class.py
@@ -1,9 +1,7 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import pytest
 import src.crawler as crawler_module
-from src.crawler import Crawler
 
 
 def test_crawler_sets_article_url(monkeypatch):
diff --git a/tests/unit/llms/test_llm.py b/tests/unit/llms/test_llm.py
index 2587080..dcdbc2f 100644
--- a/tests/unit/llms/test_llm.py
+++ b/tests/unit/llms/test_llm.py
@@ -1,8 +1,6 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import os
-import types
 import pytest
 from src.llms import llm
 
diff --git a/tests/unit/prompt_enhancer/graph/test_builder.py b/tests/unit/prompt_enhancer/graph/test_builder.py
index 575c270..f661f8b 100644
--- a/tests/unit/prompt_enhancer/graph/test_builder.py
+++ b/tests/unit/prompt_enhancer/graph/test_builder.py
@@ -6,7 +6,6 @@ from unittest.mock import patch, MagicMock
 
 from src.prompt_enhancer.graph.builder import build_graph
 from src.prompt_enhancer.graph.state import PromptEnhancerState
-from src.config.report_style import ReportStyle
 
 
 class TestBuildGraph:
@@ -48,7 +47,7 @@ class TestBuildGraph:
         mock_state_graph.return_value = mock_builder
         mock_builder.compile.return_value = mock_compiled_graph
 
-        result = build_graph()
+        build_graph()
 
         # Verify the correct node function was added
         mock_builder.add_node.assert_called_once_with("enhancer", mock_enhancer_node)
diff --git a/tests/unit/prompt_enhancer/graph/test_state.py b/tests/unit/prompt_enhancer/graph/test_state.py
index 8501882..3006b78 100644
--- a/tests/unit/prompt_enhancer/graph/test_state.py
+++ b/tests/unit/prompt_enhancer/graph/test_state.py
@@ -1,7 +1,6 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import pytest
 from src.prompt_enhancer.graph.state import PromptEnhancerState
 from src.config.report_style import ReportStyle
 
diff --git a/tests/unit/rag/test_ragflow.py b/tests/unit/rag/test_ragflow.py
index 202cb5b..b5310ad 100644
--- a/tests/unit/rag/test_ragflow.py
+++ b/tests/unit/rag/test_ragflow.py
@@ -1,9 +1,7 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import os
 import pytest
-import requests
 from unittest.mock import patch, MagicMock
 from src.rag.ragflow import RAGFlowProvider, parse_uri
 
@@ -144,30 +142,6 @@ def test_list_resources_success(mock_get, monkeypatch):
     assert resources[1].description == "desc2"
 
 
-@patch("src.rag.ragflow.requests.get")
-def test_list_resources_success(mock_get, monkeypatch):
-    monkeypatch.setenv("RAGFLOW_API_URL", "http://api")
-    monkeypatch.setenv("RAGFLOW_API_KEY", "key")
-    provider = RAGFlowProvider()
-    mock_response = MagicMock()
-    mock_response.status_code = 200
-    mock_response.json.return_value = {
-        "data": [
-            {"id": "123", "name": "Dataset1", "description": "desc1"},
-            {"id": "456", "name": "Dataset2", "description": "desc2"},
-        ]
-    }
-    mock_get.return_value = mock_response
-    resources = provider.list_resources()
-    assert len(resources) == 2
-    assert resources[0].uri == "rag://dataset/123"
-    assert resources[0].title == "Dataset1"
-    assert resources[0].description == "desc1"
-    assert resources[1].uri == "rag://dataset/456"
-    assert resources[1].title == "Dataset2"
-    assert resources[1].description == "desc2"
-
-
 @patch("src.rag.ragflow.requests.get")
 def test_list_resources_error(mock_get, monkeypatch):
     monkeypatch.setenv("RAGFLOW_API_URL", "http://api")
diff --git a/tests/unit/rag/test_vikingdb_knowledge_base.py b/tests/unit/rag/test_vikingdb_knowledge_base.py
index 22203e7..dbbea11 100644
--- a/tests/unit/rag/test_vikingdb_knowledge_base.py
+++ b/tests/unit/rag/test_vikingdb_knowledge_base.py
@@ -173,8 +173,8 @@ class TestVikingDBKnowledgeBaseProviderPrepareRequest:
         """Test basic request preparation"""
         with (
             patch("src.rag.vikingdb_knowledge_base.Request") as mock_request,
-            patch("src.rag.vikingdb_knowledge_base.Credentials") as mock_credentials,
-            patch("src.rag.vikingdb_knowledge_base.SignerV4.sign") as mock_sign,
+            patch("src.rag.vikingdb_knowledge_base.Credentials") as _mock_credentials,
+            patch("src.rag.vikingdb_knowledge_base.SignerV4.sign") as _mock_sign,
         ):
 
             mock_req_instance = MagicMock()
diff --git a/tests/unit/server/test_app.py b/tests/unit/server/test_app.py
index 0016b50..f6eb503 100644
--- a/tests/unit/server/test_app.py
+++ b/tests/unit/server/test_app.py
@@ -2,31 +2,17 @@
 # SPDX-License-Identifier: MIT
 
 import base64
-import json
 import os
-from unittest.mock import AsyncMock, MagicMock, patch, mock_open
-from uuid import uuid4
-from fastapi.responses import JSONResponse, StreamingResponse
+from unittest.mock import MagicMock, patch, mock_open
 import pytest
 from fastapi.testclient import TestClient
-from fastapi import HTTPException, logger
+from fastapi import HTTPException
 from src.server.app import app, _make_event, _astream_workflow_generator
-from src.server.mcp_request import MCPServerMetadataRequest
-from src.server.rag_request import RAGResourceRequest
 from src.config.report_style import ReportStyle
 from langgraph.types import Command
 from langchain_core.messages import ToolMessage
 from langchain_core.messages import AIMessageChunk
 
-from src.server.chat_request import (
-    ChatRequest,
-    TTSRequest,
-    GeneratePodcastRequest,
-    GeneratePPTRequest,
-    GenerateProseRequest,
-    EnhancePromptRequest,
-)
-
 
 @pytest.fixture
 def client():
diff --git a/tests/unit/server/test_chat_request.py b/tests/unit/server/test_chat_request.py
index 0556a7c..d3f5363 100644
--- a/tests/unit/server/test_chat_request.py
+++ b/tests/unit/server/test_chat_request.py
@@ -1,7 +1,6 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import asyncio  # Ensure asyncio is imported
 import pytest
 from pydantic import ValidationError
 from src.config.report_style import ReportStyle
diff --git a/tests/unit/tools/test_crawl.py b/tests/unit/tools/test_crawl.py
index 405c44f..cdbe4cf 100644
--- a/tests/unit/tools/test_crawl.py
+++ b/tests/unit/tools/test_crawl.py
@@ -1,4 +1,3 @@
-import pytest
 from unittest.mock import Mock, patch
 from src.tools.crawl import crawl_tool
 
diff --git a/tests/unit/tools/test_decorators.py b/tests/unit/tools/test_decorators.py
index 4dbc2b5..5864dcb 100644
--- a/tests/unit/tools/test_decorators.py
+++ b/tests/unit/tools/test_decorators.py
@@ -1,10 +1,8 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import pytest
-import logging
-from unittest.mock import Mock, call, patch, MagicMock
-from src.tools.decorators import LoggedToolMixin, create_logged_tool
+from unittest.mock import Mock, call, patch
+from src.tools.decorators import create_logged_tool
 
 
 class MockBaseTool:
@@ -58,7 +56,7 @@ class TestLoggedToolMixin:
         tool = LoggedTool()
 
         with patch("src.tools.decorators.logger.debug") as mock_debug:
-            result = tool._run("test_arg")
+            tool._run("test_arg")
 
             # Verify debug log was called with correct message
             mock_debug.assert_has_calls(
diff --git a/tests/unit/tools/test_python_repl.py b/tests/unit/tools/test_python_repl.py
index 963744e..728b544 100644
--- a/tests/unit/tools/test_python_repl.py
+++ b/tests/unit/tools/test_python_repl.py
@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: MIT
 
 import pytest
-from unittest.mock import Mock, patch, MagicMock
+from unittest.mock import patch
 from src.tools.python_repl import python_repl_tool
 
 
diff --git a/tests/unit/tools/test_search.py b/tests/unit/tools/test_search.py
index cc914a2..1fb5c20 100644
--- a/tests/unit/tools/test_search.py
+++ b/tests/unit/tools/test_search.py
@@ -3,7 +3,7 @@
 
 import os
 import pytest
-from unittest.mock import patch, MagicMock
+from unittest.mock import patch
 from src.tools.search import get_web_search_tool
 from src.config import SearchEngine
 
diff --git a/tests/unit/tools/test_tavily_search_api_wrapper.py b/tests/unit/tools/test_tavily_search_api_wrapper.py
index 37d6242..eb60316 100644
--- a/tests/unit/tools/test_tavily_search_api_wrapper.py
+++ b/tests/unit/tools/test_tavily_search_api_wrapper.py
@@ -3,7 +3,6 @@
 import json
 import pytest
 from unittest.mock import Mock, patch, AsyncMock, MagicMock
-import aiohttp
 import requests
 from src.tools.tavily_search.tavily_search_api_wrapper import (
     EnhancedTavilySearchAPIWrapper,
diff --git a/tests/unit/tools/test_tavily_search_results_with_images.py b/tests/unit/tools/test_tavily_search_results_with_images.py
index 963dbf1..4db69ee 100644
--- a/tests/unit/tools/test_tavily_search_results_with_images.py
+++ b/tests/unit/tools/test_tavily_search_results_with_images.py
@@ -4,7 +4,6 @@
 import json
 import pytest
 from unittest.mock import Mock, patch, AsyncMock
-from typing import Dict, Any
 from src.tools.tavily_search.tavily_search_results_with_images import (
     TavilySearchResultsWithImages,
 )
diff --git a/tests/unit/tools/test_tools_retriever.py b/tests/unit/tools/test_tools_retriever.py
index fa73b68..052504a 100644
--- a/tests/unit/tools/test_tools_retriever.py
+++ b/tests/unit/tools/test_tools_retriever.py
@@ -1,7 +1,7 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-from unittest.mock import Mock, patch, MagicMock
+from unittest.mock import Mock, patch
 from langchain_core.callbacks import (
     CallbackManagerForToolRun,
     AsyncCallbackManagerForToolRun,
diff --git a/tests/unit/utils/test_json_utils.py b/tests/unit/utils/test_json_utils.py
index 35f3de1..f90707a 100644
--- a/tests/unit/utils/test_json_utils.py
+++ b/tests/unit/utils/test_json_utils.py
@@ -1,9 +1,7 @@
 # Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
 # SPDX-License-Identifier: MIT
 
-import pytest
 import json
-from unittest.mock import patch
 from src.utils.json_utils import repair_json_output