diff --git a/astrbot/core/knowledge_base/retrieval/manager.py b/astrbot/core/knowledge_base/retrieval/manager.py
index 5b414b171e..a49f626ef5 100644
--- a/astrbot/core/knowledge_base/retrieval/manager.py
+++ b/astrbot/core/knowledge_base/retrieval/manager.py
@@ -4,6 +4,7 @@
 """
 
 import time
+import unicodedata
 from dataclasses import dataclass
 from typing import TYPE_CHECKING
 
@@ -34,6 +35,28 @@ class RetrievalResult:
     metadata: dict
 
 
+def _strip_invisible_chars(text: str) -> str:
+    """Remove control and format characters from a retrieval query.
+
+    Control (Cc, except tab/newline/CR) and format (Cf) characters are
+    invisible payloads that some embedding providers reject with HTTP 400
+    (e.g. SiliconFlow code 20015), typically originating from sticker /
+    image-caption pipelines.
+
+    Args:
+        text: Raw query text.
+
+    Returns:
+        The query with invisible characters removed.
+
+    """
+    return "".join(
+        ch
+        for ch in text
+        if ch not in "\t\n\r" and unicodedata.category(ch) not in ("Cc", "Cf")
+    )
+
+
 class RetrievalManager:
     """检索管理器
 
@@ -87,6 +110,16 @@ async def retrieve(
             List[RetrievalResult]: 检索结果列表
 
         """
+        # Remove invisible characters and skip retrieval when nothing
+        # remains, so invalid queries never reach the embedding provider.
+        query = _strip_invisible_chars(query).strip()
+        if not query:
+            logger.debug(
+                "Knowledge base retrieval skipped: query is empty after "
+                "removing invisible characters.",
+            )
+            return []
+
         if not kb_ids:
             return []
 
@@ -229,7 +262,8 @@ async def _dense_retrieve(
                 all_results.extend(vec_results)
             except Exception as e:
                 logger.error(
-                    f"知识库 {kb_id} 稠密检索失败: {type(e).__name__}: {e}",
+                    f"知识库 {kb_id} 稠密检索失败: {type(e).__name__}: {e} "
+                    f"(query={query!r}, query_length={len(query)})",
                     exc_info=True,
                 )
                 # skip the faulty KB and continue
diff --git a/tests/test_retrieval_query_sanitize.py b/tests/test_retrieval_query_sanitize.py
new file mode 100644
index 0000000000..aeebac56c2
--- /dev/null
+++ b/tests/test_retrieval_query_sanitize.py
@@ -0,0 +1,63 @@
+from __future__ import annotations
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+# Import astrbot.api first: the kb retrieval import chain
+# (manager -> kb_helper -> provider.manager -> persona_mgr -> astrbot.api)
+# only resolves when astrbot.api is fully initialized beforehand.
+import astrbot.api  # noqa: F401
+from astrbot.core.knowledge_base.retrieval.manager import RetrievalManager
+
+
+def _make_manager() -> RetrievalManager:
+    manager = RetrievalManager(
+        sparse_retriever=MagicMock(),
+        rank_fusion=MagicMock(),
+        kb_db=MagicMock(),
+    )
+    manager.rank_fusion.fuse = AsyncMock(return_value=[])
+    manager.kb_db.get_documents_with_metadata_batch = AsyncMock(return_value={})
+    return manager
+
+
+@pytest.mark.asyncio
+async def test_invisible_only_query_skips_retrieval() -> None:
+    manager = _make_manager()
+    manager._dense_retrieve = AsyncMock(return_value=[])
+    manager.sparse_retriever.retrieve = AsyncMock(return_value=[])
+
+    results = await manager.retrieve(
+        query="\u200b\ufeff\x00",
+        kb_ids=["kb-1"],
+        kb_id_helper_map={},
+    )
+
+    assert results == []
+    manager._dense_retrieve.assert_not_awaited()
+    manager.sparse_retriever.retrieve.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_invisible_chars_are_stripped_before_retrieval() -> None:
+    manager = _make_manager()
+    manager._dense_retrieve = AsyncMock(return_value=[])
+    manager.sparse_retriever.retrieve = AsyncMock(return_value=[])
+    manager.rank_fusion.fuse = AsyncMock(return_value=[])
+
+    kb_helper = MagicMock()
+    kb_helper.kb.top_k_dense = 50
+    kb_helper.kb.top_k_sparse = 50
+    kb_helper.kb.top_m_final = 5
+    kb_helper.vec_db.rerank_provider = None
+
+    results = await manager.retrieve(
+        query="\u200bOni\u200f 恶鬼 ",
+        kb_ids=["kb-1"],
+        kb_id_helper_map={"kb-1": kb_helper},
+    )
+
+    assert results == []
+    sent_query = manager._dense_retrieve.await_args.kwargs["query"]
+    assert sent_query == "Oni 恶鬼"