diff --git a/pytests/utils_test/test_bot_identity_utils.py b/pytests/utils_test/test_bot_identity_utils.py
index 55502a89..2ba8f35a 100644
--- a/pytests/utils_test/test_bot_identity_utils.py
+++ b/pytests/utils_test/test_bot_identity_utils.py
@@ -157,6 +157,14 @@ def test_unknown_platform_no_longer_falls_back_to_qq(monkeypatch):
     assert "unknown_platform" in logger.warning_messages[-1]
 
 
+def test_unknown_platform_warns_only_once(monkeypatch):
+    utils_module, logger = load_utils_module(monkeypatch, qq_account=123456, platforms=[])
+
+    assert utils_module.is_bot_self("unknown_platform", "first") is False
+    assert utils_module.is_bot_self(" unknown_platform ", "second") is False
+    assert len(logger.warning_messages) == 1
+
+
 def test_unconfigured_qq_account_disables_qq_and_webui_identity(monkeypatch):
     utils_module, _logger = load_utils_module(monkeypatch, qq_account=0, platforms=["telegram:tg_bot"])
 
@@ -185,3 +193,24 @@ def test_is_mentioned_bot_in_message_uses_platform_account(monkeypatch):
     assert is_mentioned is True
     assert is_at is True
     assert reply_probability == 1.0
+
+
+def test_is_mentioned_bot_in_message_normalizes_qq_platform(monkeypatch):
+    utils_module, _logger = load_utils_module(monkeypatch, qq_account=123456, platforms=[])
+
+    message = SimpleNamespace(
+        processed_plain_text="@<MaiBot:123456> 你好",
+        platform=" QQ ",
+        is_mentioned=False,
+        message_segment=None,
+        message_info=SimpleNamespace(
+            additional_config={},
+            user_info=SimpleNamespace(user_id="user_1"),
+        ),
+    )
+
+    is_mentioned, is_at, reply_probability = utils_module.is_mentioned_bot_in_message(message)
+
+    assert is_mentioned is True
+    assert is_at is True
+    assert reply_probability == 1.0
diff --git a/src/chat/brain_chat/PFC/message_sender.py b/src/chat/brain_chat/PFC/message_sender.py
index 483a03c8..a927c413 100644
--- a/src/chat/brain_chat/PFC/message_sender.py
+++ b/src/chat/brain_chat/PFC/message_sender.py
@@ -42,8 +42,12 @@ class DirectMessageSender:
             segments = Seg(type="seglist", data=[Seg(type="text", data=content)])
 
             # 获取麦麦的信息
+            bot_user_id = get_bot_account(chat_stream.platform)
+            if not bot_user_id:
+                logger.warning(f"[私聊][{self.private_name}]平台 {chat_stream.platform} 未配置机器人账号，发送消息时回退到 QQ 账号")
+                bot_user_id = str(getattr(global_config.bot, "qq_account", "")).strip()
             bot_user_info = UserInfo(
-                user_id=get_bot_account(chat_stream.platform),
+                user_id=bot_user_id,
                 user_nickname=global_config.bot.nickname,
             )
 
diff --git a/src/chat/replyer/group_generator.py b/src/chat/replyer/group_generator.py
index 760cb9ea..3c41ae2f 100644
--- a/src/chat/replyer/group_generator.py
+++ b/src/chat/replyer/group_generator.py
@@ -1115,6 +1115,10 @@ class DefaultReplyer:
         anchor_message: Optional[MaiMessage] = None,
     ) -> SessionMessage:
         """构建单个发送消息"""
+        bot_user_id = get_bot_account(self.chat_stream.platform)
+        if not bot_user_id:
+            logger.warning(f"平台 {self.chat_stream.platform} 未配置机器人账号，发送消息时回退到 QQ 账号")
+            bot_user_id = str(getattr(global_config.bot, "qq_account", "")).strip()
 
         maim_message = MessageBase(
             message_info=BaseMessageInfo(
@@ -1122,7 +1126,7 @@ class DefaultReplyer:
                 message_id=message_id,
                 time=thinking_start_time,
                 user_info=MaimUserInfo(
-                    user_id=get_bot_account(self.chat_stream.platform),
+                    user_id=bot_user_id,
                     user_nickname=global_config.bot.nickname,
                 ),
                 additional_config={},
diff --git a/src/chat/replyer/private_generator.py b/src/chat/replyer/private_generator.py
index 74049226..008124d4 100644
--- a/src/chat/replyer/private_generator.py
+++ b/src/chat/replyer/private_generator.py
@@ -955,6 +955,10 @@ class PrivateReplyer:
         anchor_message: Optional[MaiMessage] = None,
     ) -> SessionMessage:
         """构建单个发送消息"""
+        bot_user_id = get_bot_account(self.chat_stream.platform)
+        if not bot_user_id:
+            logger.warning(f"平台 {self.chat_stream.platform} 未配置机器人账号，发送消息时回退到 QQ 账号")
+            bot_user_id = str(getattr(global_config.bot, "qq_account", "")).strip()
 
         maim_message = MessageBase(
             message_info=BaseMessageInfo(
@@ -962,7 +966,7 @@ class PrivateReplyer:
                 message_id=message_id,
                 time=thinking_start_time,
                 user_info=MaimUserInfo(
-                    user_id=get_bot_account(self.chat_stream.platform),
+                    user_id=bot_user_id,
                     user_nickname=global_config.bot.nickname,
                 ),
                 group_info=None,
diff --git a/src/chat/utils/utils.py b/src/chat/utils/utils.py
index 947d9fc5..44eae4c0 100644
--- a/src/chat/utils/utils.py
+++ b/src/chat/utils/utils.py
@@ -1,11 +1,12 @@
+from datetime import datetime
+from typing import TYPE_CHECKING, List, Optional, Tuple
+
 import ast
 import json
 import os
 import random
 import re
 import time
-from datetime import datetime
-from typing import Optional, Tuple, List, TYPE_CHECKING
 
 import jieba
 
@@ -15,12 +16,14 @@ from src.common.logger import get_logger
 from src.config.config import global_config, model_config
 from src.llm_models.utils_model import LLMRequest
 from src.person_info.person_info import Person
+
 from .typo_generator import ChineseTypoGenerator
 
 if TYPE_CHECKING:
     from src.common.data_models.info_data_model import TargetPersonInfo
 
 logger = get_logger("chat_utils")
+_warned_unconfigured_platforms: set[str] = set()
 
 
 def is_english_letter(char: str) -> bool:
@@ -122,14 +125,16 @@ def is_bot_self(platform: str, user_id: str) -> bool:
     if bot_account:
         return user_id_str == bot_account
 
-    logger.warning(f"平台 {normalized_platform} 未配置机器人账号，无法判断用户 {user_id_str} 是否为机器人自己")
+    if normalized_platform not in _warned_unconfigured_platforms:
+        _warned_unconfigured_platforms.add(normalized_platform)
+        logger.warning(f"平台 {normalized_platform} 未配置机器人账号，无法判断用户 {user_id_str} 是否为机器人自己")
     return False
 
 
 def is_mentioned_bot_in_message(message: SessionMessage) -> tuple[bool, bool, float]:
     """检查消息是否提到了机器人（统一多平台实现）"""
     text = message.processed_plain_text or ""
-    platform = message.platform or ""
+    platform = str(message.platform or "").strip().lower()
 
     # 获取当前平台对应的账号
     current_account = get_bot_account(platform)
diff --git a/src/common/message_repository.py b/src/common/message_repository.py
index 79353a9a..81ae6360 100644
--- a/src/common/message_repository.py
+++ b/src/common/message_repository.py
@@ -7,9 +7,9 @@ import traceback
 from sqlalchemy import and_, func, not_, or_
 from sqlmodel import col, select
 
+from src.chat.message_receive.message import SessionMessage
 from src.common.database.database import get_db_session
 from src.common.database.database_model import Messages
-from src.chat.message_receive.message import SessionMessage
 from src.common.logger import get_logger
 
 logger = get_logger(__name__)
@@ -162,17 +162,26 @@ def find_messages(
             after_time=after_time,
         )
         if filter_bot:
-            from src.chat.utils.utils import get_all_bot_accounts
+            from src.chat.utils.utils import _get_configured_qq_account, get_all_bot_accounts
 
             bot_accounts = get_all_bot_accounts()
+            exclusion_conditions: list[Any] = []
             if bot_accounts:
-                bot_identity_predicate = or_(
-                    *[
-                        and_(Messages.platform == platform_name, Messages.user_id == account)
-                        for platform_name, account in bot_accounts.items()
-                    ]
+                exclusion_conditions.append(
+                    or_(
+                        *[
+                            and_(Messages.platform == platform_name, Messages.user_id == account)
+                            for platform_name, account in bot_accounts.items()
+                        ]
+                    )
                 )
-                conditions.append(not_(bot_identity_predicate))
+
+            # 兼容旧数据：历史机器人消息在所有平台上都使用 QQ 账号进行存储。
+            if qq_fallback := _get_configured_qq_account():
+                exclusion_conditions.append(Messages.user_id == qq_fallback)
+
+            if exclusion_conditions:
+                conditions.append(not_(or_(*exclusion_conditions)))
         if filter_command:
             conditions.append(Messages.is_command == False)  # noqa: E712
 
diff --git a/src/common/utils/system_utils.py b/src/common/utils/system_utils.py
index 6518db42..a5085f19 100644
--- a/src/common/utils/system_utils.py
+++ b/src/common/utils/system_utils.py
@@ -1,4 +1,5 @@
-# TODO: 这个兼容包装层后续可以删除，统一直接使用 src.chat.utils.utils.is_bot_self
+# TODO: 这个包装层后续可以删除，统一直接使用 src.chat.utils.utils.is_bot_self
+# 注意：参数顺序已从旧版 (user_id, platform) 变更为 (platform, user_id)，与统一接口一致
 def is_bot_self(platform: str, user_id: str) -> bool:
     """
     判断用户 ID 是否是机器人自己。
diff --git a/src/services/send_service.py b/src/services/send_service.py
index ee2a8993..6749adfc 100644
--- a/src/services/send_service.py
+++ b/src/services/send_service.py
@@ -83,6 +83,10 @@ async def _send_to_target(
         additional_config: dict[str, object] = {}
         if selected_expressions is not None:
             additional_config["selected_expressions"] = selected_expressions
+        bot_user_id = get_bot_account(target_stream.platform)
+        if not bot_user_id:
+            logger.warning(f"[SendService] 平台 {target_stream.platform} 未配置机器人账号，发送消息时回退到 QQ 账号")
+            bot_user_id = str(getattr(global_config.bot, "qq_account", "")).strip()
 
         maim_message = MessageBase(
             message_info=BaseMessageInfo(
@@ -90,7 +94,7 @@ async def _send_to_target(
                 message_id=message_id,
                 time=current_time,
                 user_info=MaimUserInfo(
-                    user_id=get_bot_account(target_stream.platform),
+                    user_id=bot_user_id,
                     user_nickname=global_config.bot.nickname,
                     platform=target_stream.platform,
                 ),