diff --git a/src/astrbot_sdk/decorators.py b/src/astrbot_sdk/decorators.py
index 015090763..7caf12d11 100644
--- a/src/astrbot_sdk/decorators.py
+++ b/src/astrbot_sdk/decorators.py
@@ -183,6 +183,10 @@ def _replace_filter(meta: HandlerMeta, spec: FilterSpec) -> None:
     meta.filters.append(spec)
 
 
+def _has_filter_kind(meta: HandlerMeta, kind: str) -> bool:
+    return any(getattr(item, "kind", None) == kind for item in meta.filters)
+
+
 def _set_platform_filter(
     meta: HandlerMeta,
     values: list[str],
@@ -197,6 +201,8 @@ def _set_platform_filter(
     existing = meta.decorator_sources.get("platforms")
     if existing is not None and existing != source:
         raise ValueError("platforms(...) 不能与 on_message(platforms=...) 混用")
+    if existing is None and _has_filter_kind(meta, "platform"):
+        raise ValueError("platforms(...) 不能与已有平台过滤器混用")
     meta.decorator_sources["platforms"] = source
     _replace_filter(meta, PlatformFilterSpec(platforms=normalized))
 
@@ -219,6 +225,10 @@ def _set_message_type_filter(
         raise ValueError(
             "group_only()/private_only()/message_types(...) 不能与已有消息类型约束混用"
         )
+    if existing is None and _has_filter_kind(meta, "message_type"):
+        raise ValueError(
+            "group_only()/private_only()/message_types(...) 不能与已有消息类型过滤器混用"
+        )
     meta.decorator_sources["message_types"] = source
     _replace_filter(meta, MessageTypeFilterSpec(message_types=normalized))
 
diff --git a/tests/test_decorators_filter_guards.py b/tests/test_decorators_filter_guards.py
new file mode 100644
index 000000000..08d3a8be3
--- /dev/null
+++ b/tests/test_decorators_filter_guards.py
@@ -0,0 +1,48 @@
+from __future__ import annotations
+
+import pytest
+
+from astrbot_sdk.decorators import (
+    append_filter_meta,
+    get_handler_meta,
+    message_types,
+    platforms,
+)
+from astrbot_sdk.protocol.descriptors import (
+    MessageTypeFilterSpec,
+    PlatformFilterSpec,
+)
+
+
+def test_platforms_rejects_existing_manual_platform_filter() -> None:
+    def handler() -> None:
+        return None
+
+    append_filter_meta(
+        handler,
+        specs=[PlatformFilterSpec(platforms=["qq"])],
+    )
+
+    meta = get_handler_meta(handler)
+    assert meta is not None
+    assert meta.decorator_sources == {}
+
+    with pytest.raises(ValueError, match="已有平台过滤器"):
+        platforms("wechat")(handler)
+
+
+def test_message_types_rejects_existing_manual_message_type_filter() -> None:
+    def handler() -> None:
+        return None
+
+    append_filter_meta(
+        handler,
+        specs=[MessageTypeFilterSpec(message_types=["group"])],
+    )
+
+    meta = get_handler_meta(handler)
+    assert meta is not None
+    assert meta.decorator_sources == {}
+
+    with pytest.raises(ValueError, match="已有消息类型过滤器"):
+        message_types("private")(handler)