diff --git a/astrbot/core/db/__init__.py b/astrbot/core/db/__init__.py
index bf415ffb5..cf37c4866 100644
--- a/astrbot/core/db/__init__.py
+++ b/astrbot/core/db/__init__.py
@@ -27,6 +27,7 @@ from astrbot.core.db.po import (
     UmoAlias,
     WebChatThread,
 )
+from astrbot.core.sentinels import NOT_GIVEN
 
 
 @dataclass
@@ -444,11 +445,23 @@ class BaseDatabase(abc.ABC):
         persona_id: str,
         system_prompt: str | None = None,
         begin_dialogs: list[str] | None = None,
-        tools: list[str] | None = None,
-        skills: list[str] | None = None,
-        custom_error_message: str | None = None,
+        tools: list[str] | None | object = NOT_GIVEN,
+        skills: list[str] | None | object = NOT_GIVEN,
+        custom_error_message: str | None | object = NOT_GIVEN,
     ) -> Persona | None:
-        """Update a persona's system prompt or begin dialogs."""
+        """Update a persona record.
+
+        Args:
+            persona_id: Persona ID to update.
+            system_prompt: Optional replacement system prompt.
+            begin_dialogs: Optional replacement begin dialogs.
+            tools: Tool names, None for all tools, or NOT_GIVEN to leave unchanged.
+            skills: Skill names, None for all skills, or NOT_GIVEN to leave unchanged.
+            custom_error_message: Custom fallback message, None to clear, or NOT_GIVEN to leave unchanged.
+
+        Returns:
+            Updated persona, or None when no fields were updated.
+        """
         ...
 
     @abc.abstractmethod
diff --git a/astrbot/dashboard/api/personas.py b/astrbot/dashboard/api/personas.py
index ae83e5452..00bdeba6a 100644
--- a/astrbot/dashboard/api/personas.py
+++ b/astrbot/dashboard/api/personas.py
@@ -45,7 +45,15 @@ async def _json_or_empty(request: Request) -> dict[str, Any]:
 
 
 def _model_dict(payload) -> dict[str, Any]:
-    return payload.model_dump(exclude_none=True)
+    """Serialize a request model while preserving explicit null updates.
+
+    Args:
+        payload: Pydantic request model.
+
+    Returns:
+        Request data without fields omitted by the caller.
+    """
+    return payload.model_dump(exclude_unset=True)
 
 
 def _raise_persona_error(exc: PersonaServiceError | ValueError) -> None:
diff --git a/astrbot/dashboard/services/persona_service.py b/astrbot/dashboard/services/persona_service.py
index 31c4f1084..5a319b0e2 100644
--- a/astrbot/dashboard/services/persona_service.py
+++ b/astrbot/dashboard/services/persona_service.py
@@ -40,8 +40,12 @@ class PersonaService:
 
     async def create_persona(self, data: object) -> dict:
         payload = self._payload(data)
-        persona_id = str(payload.get("persona_id", "")).strip()
-        system_prompt = str(payload.get("system_prompt", "")).strip()
+        raw_persona_id = payload.get("persona_id")
+        raw_system_prompt = payload.get("system_prompt")
+        persona_id = str(raw_persona_id).strip() if raw_persona_id is not None else ""
+        system_prompt = (
+            str(raw_system_prompt).strip() if raw_system_prompt is not None else ""
+        )
         begin_dialogs = payload.get("begin_dialogs", [])
         tools = payload.get("tools")
         skills = payload.get("skills")
diff --git a/tests/test_fastapi_v1_dashboard.py b/tests/test_fastapi_v1_dashboard.py
index 937139757..7e73869dd 100644
--- a/tests/test_fastapi_v1_dashboard.py
+++ b/tests/test_fastapi_v1_dashboard.py
@@ -473,7 +473,7 @@ class FakePersonaManager:
     async def update_persona(self, persona_id: str, **kwargs) -> None:
         persona = self.personas[persona_id]
         for key, value in kwargs.items():
-            if value is not None:
+            if key in ("tools", "skills", "custom_error_message") or value is not None:
                 setattr(persona, key, value)
 
     async def delete_persona(self, persona_id: str) -> None:
@@ -2476,6 +2476,29 @@ async def test_v1_safe_persona_routes_accept_slash_ids(
     assert persona_id not in persona_mgr.personas
 
 
+@pytest.mark.asyncio
+async def test_v1_persona_by_id_update_preserves_explicit_null_tools_and_skills(
+    asgi_client: httpx.AsyncClient,
+    fake_core_lifecycle,
+):
+    persona_id = "persona/foo"
+    headers = _jwt_headers()
+    persona = fake_core_lifecycle.persona_mgr.personas[persona_id]
+    persona.tools = ["tool-a"]
+    persona.skills = ["skill-a"]
+
+    response = await asgi_client.put(
+        "/api/v1/personas/by-id",
+        json={"persona_id": persona_id, "tools": None, "skills": None},
+        headers=headers,
+    )
+
+    assert response.status_code == 200
+    assert response.json()["data"] == {"message": "人格更新成功"}
+    assert persona.tools is None
+    assert persona.skills is None
+
+
 @pytest.mark.asyncio
 async def test_v1_im_routes_use_im_scope_and_running_platform(
     asgi_client: httpx.AsyncClient,