diff --git a/astrbot/core/astr_main_agent.py b/astrbot/core/astr_main_agent.py
index 0f51a29c0..f18b49a43 100644
--- a/astrbot/core/astr_main_agent.py
+++ b/astrbot/core/astr_main_agent.py
@@ -846,6 +846,8 @@ def _apply_sandbox_tools(
 ) -> None:
     if req.func_tool is None:
         req.func_tool = ToolSet()
+    if req.system_prompt is None:
+        req.system_prompt = ""
     booter = config.sandbox_cfg.get("booter", "shipyard_neo")
     if booter == "shipyard":
         ep = config.sandbox_cfg.get("shipyard_endpoint", "")
diff --git a/astrbot/core/computer/computer_client.py b/astrbot/core/computer/computer_client.py
index 1853abf75..aa10d125e 100644
--- a/astrbot/core/computer/computer_client.py
+++ b/astrbot/core/computer/computer_client.py
@@ -1,4 +1,5 @@
 import json
+import os
 import shutil
 import uuid
 from pathlib import Path
@@ -41,8 +42,6 @@ def _discover_bay_credentials(endpoint: str) -> str:
     Returns:
         API key string, or empty string if not found.
     """
-    import os
-
     candidates: list[Path] = []
 
     # 1. BAY_DATA_DIR env var
diff --git a/tests/unit/test_astr_main_agent.py b/tests/unit/test_astr_main_agent.py
index 3ce974f41..e0682ae06 100644
--- a/tests/unit/test_astr_main_agent.py
+++ b/tests/unit/test_astr_main_agent.py
@@ -516,30 +516,6 @@ class TestEnsurePersonaAndSkills:
 
         assert "Persona Instructions" not in req.system_prompt
 
-    @pytest.mark.asyncio
-    async def test_ensure_skills(self, mock_event, mock_context):
-        """Test applying skills to request."""
-        module = ama
-        mock_skill = MagicMock()
-        mock_skill.name = "test_skill"
-        mock_skill.to_prompt.return_value = "Skill description"
-        mock_context.persona_manager.personas_v3 = []
-        mock_context.persona_manager.resolve_selected_persona = AsyncMock(
-            return_value=(None, None, None, False)
-        )
-
-        with patch("astrbot.core.astr_main_agent.SkillManager") as mock_skill_mgr_cls:
-            mock_skill_mgr = MagicMock()
-            mock_skill_mgr.list_skills.return_value = [mock_skill]
-            mock_skill_mgr_cls.return_value = mock_skill_mgr
-
-            req = ProviderRequest()
-            req.conversation = MagicMock(persona_id=None)
-
-            await module._ensure_persona_and_skills(req, {}, mock_context, mock_event)
-
-        assert "test_skill" in req.system_prompt
-
     @pytest.mark.asyncio
     async def test_ensure_tools_from_persona(self, mock_event, mock_context):
         """Test applying tools from persona."""