diff --git a/backend/package/yuxi/agents/toolkits/kbs/__init__.py b/backend/package/yuxi/agents/toolkits/kbs/__init__.py
index d771ed2b..dc052ee1 100644
--- a/backend/package/yuxi/agents/toolkits/kbs/__init__.py
+++ b/backend/package/yuxi/agents/toolkits/kbs/__init__.py
@@ -1,5 +1,6 @@
 from .tools import (
     get_common_kb_tools,
+    open_kb_document,
 )
 
-__all__ = ["get_common_kb_tools"]
+__all__ = ["get_common_kb_tools", "open_kb_document"]
diff --git a/backend/package/yuxi/agents/toolkits/kbs/tools.py b/backend/package/yuxi/agents/toolkits/kbs/tools.py
index e572ba4e..02ee8a46 100644
--- a/backend/package/yuxi/agents/toolkits/kbs/tools.py
+++ b/backend/package/yuxi/agents/toolkits/kbs/tools.py
@@ -161,6 +161,16 @@ class QueryKBInput(BaseModel):
     )
 
 
+class OpenKBDocumentInput(BaseModel):
+    """打开知识库文档输入模型"""
+
+    resource_id: str = Field(description="知识库资源 ID，当前对应知识库 db_id")
+    file_id: str = Field(description="要打开的文档 ID，也就是知识库文件 file_id")
+    line: int | None = Field(default=None, ge=1, description="可选，1-based 起始行号")
+    offset: int | None = Field(default=None, ge=0, description="可选，0-based 起始偏移；line 优先于 offset")
+    window_size: int = Field(default=800, ge=1, le=2000, description="读取窗口行数，默认 800 行")
+
+
 async def _resolve_visible_knowledge_bases_for_query(runtime: ToolRuntime | None) -> list[dict[str, Any]]:
     if runtime is None:
         return []
@@ -188,31 +198,54 @@ def _find_query_target(
     retrievers: dict[str, Any],
     visible_kbs: list[dict[str, Any]],
 ) -> tuple[str | None, dict[str, Any] | None, str | None]:
-    if visible_kbs:
-        matched_kbs = [db for db in visible_kbs if str(db.get("name") or "").strip() == kb_name]
-        if not matched_kbs:
-            return None, None, f"知识库 '{kb_name}' 不存在或当前会话未启用"
-        if len(matched_kbs) > 1:
-            return None, None, f"知识库 '{kb_name}' 存在重名，请先调整名称后重试"
+    if not visible_kbs:
+        return None, None, "无法获取当前会话可访问的知识库"
 
-        target_db_id = str(matched_kbs[0].get("db_id") or "")
-        target_info = retrievers.get(target_db_id)
-        if target_info is None:
-            return None, None, f"知识库 '{kb_name}' 不存在"
-        return target_db_id, target_info, None
+    matched_kbs = [db for db in visible_kbs if str(db.get("name") or "").strip() == kb_name]
+    if not matched_kbs:
+        return None, None, f"知识库 '{kb_name}' 不存在或当前会话未启用"
+    if len(matched_kbs) > 1:
+        return None, None, f"知识库 '{kb_name}' 存在重名，请先调整名称后重试"
 
-    for db_id, info in retrievers.items():
-        if info["name"] == kb_name:
-            return str(db_id), info, None
+    target_db_id = str(matched_kbs[0].get("db_id") or "")
+    target_info = retrievers.get(target_db_id)
+    if target_info is None:
+        return None, None, f"知识库 '{kb_name}' 不存在"
+    return target_db_id, target_info, None
 
-    return None, None, f"知识库 '{kb_name}' 不存在"
+
+def _normalize_retrieval_result_metadata(result: Any) -> Any:
+    if not isinstance(result, list):
+        return result
+
+    for chunk in result:
+        if not isinstance(chunk, dict):
+            continue
+
+        metadata = chunk.get("metadata")
+        if not isinstance(metadata, dict):
+            metadata = {}
+
+        file_id = metadata.get("file_id") or chunk.get("file_id") or chunk.get("full_doc_id")
+        if file_id and not metadata.get("file_id"):
+            metadata["file_id"] = str(file_id)
+
+        for key in ("chunk_id", "chunk_index"):
+            value = metadata.get(key) if metadata.get(key) is not None else chunk.get(key)
+            if value is not None and metadata.get(key) is None:
+                metadata[key] = value
+
+        chunk["metadata"] = metadata
+
+    return result
 
 
 @tool(args_schema=QueryKBInput)
 async def query_kb(kb_name: str, query_text: str, file_name: str | None = None, runtime: ToolRuntime = None) -> Any:
     """在指定知识库中检索内容
 
-    当用户需要查询具体内容时使用此工具。根据关键词在知识库中检索相关文档片段。
+    当用户需要查询具体内容时使用此工具。根据关键词在知识库中检索相关文档片段；结果中的
+    metadata.file_id 和知识库 resource_id 可用于继续调用 open_kb_document 打开原文。
 
     Args:
         kb_name: 知识库名称
@@ -254,6 +287,8 @@ async def query_kb(kb_name: str, query_text: str, file_name: str | None = None,
         else:
             result = retriever(query_text, **kwargs)
 
+        result = _normalize_retrieval_result_metadata(result)
+
         if kb_type != "milvus":
             return result
 
@@ -275,12 +310,67 @@ async def query_kb(kb_name: str, query_text: str, file_name: str | None = None,
         return f"检索失败: {str(e)}"
 
 
+@tool(args_schema=OpenKBDocumentInput)
+async def open_kb_document(
+    resource_id: str,
+    file_id: str,
+    line: int | None = None,
+    offset: int | None = None,
+    window_size: int = 800,
+    runtime: ToolRuntime = None,
+) -> dict[str, Any] | str:
+    """按行窗口打开知识库文档原文
+
+    当 query_kb 返回的片段不足以回答问题，或需要查看某个文档的上下文时使用。
+    resource_id 对应知识库 db_id，file_id 对应检索结果 metadata.file_id。
+    """
+    normalized_resource_id = str(resource_id or "").strip()
+    normalized_file_id = str(file_id or "").strip()
+    if not normalized_resource_id:
+        return "请提供 resource_id"
+    if not normalized_file_id:
+        return "请提供 file_id"
+
+    visible_kbs = await _resolve_visible_knowledge_bases_for_query(runtime)
+    if not visible_kbs:
+        return "无法获取当前会话可访问的知识库"
+
+    visible_resource_ids = {str(kb.get("db_id") or "").strip() for kb in visible_kbs}
+    if normalized_resource_id not in visible_resource_ids:
+        return f"知识库资源 '{normalized_resource_id}' 不存在或当前会话未启用"
+
+    retrievers = knowledge_base.get_retrievers()
+    target_info = retrievers.get(normalized_resource_id)
+    if target_info is None:
+        return f"知识库资源 '{normalized_resource_id}' 不存在"
+
+    metadata = target_info.get("metadata") if isinstance(target_info, dict) else None
+    kb_type = str((metadata or {}).get("kb_type") or "").strip().lower()
+    if kb_type == "dify":
+        return "Dify 知识库为外部只读检索源，当前不支持通过 Open 打开全文"
+
+    try:
+        start_offset = int(line) - 1 if line is not None else int(offset or 0)
+        window = await knowledge_base.open_file_content(
+            normalized_resource_id,
+            normalized_file_id,
+            offset=start_offset,
+            limit=window_size,
+        )
+        return {"resource_id": normalized_resource_id, "file_id": normalized_file_id, **window}
+
+    except Exception as e:
+        logger.error(f"打开知识库文档失败: {e}")
+        return f"打开知识库文档失败: {str(e)}"
+
+
 def get_common_kb_tools() -> list:
     """获取通用知识库工具列表
 
-    返回 3 个通用工具：
+    返回 4 个通用工具：
     - list_kbs: 列出用户可访问的知识库
     - get_mindmap: 获取指定知识库的思维导图
     - query_kb: 在指定知识库中检索
+    - open_kb_document: 按 file_id 分段打开知识库文档
     """
-    return [list_kbs, get_mindmap, query_kb]
+    return [list_kbs, get_mindmap, query_kb, open_kb_document]
diff --git a/backend/package/yuxi/knowledge/base.py b/backend/package/yuxi/knowledge/base.py
index 0ccbf048..193538cd 100644
--- a/backend/package/yuxi/knowledge/base.py
+++ b/backend/package/yuxi/knowledge/base.py
@@ -397,6 +397,43 @@ class KnowledgeBase(ABC):
         content_bytes = await minio_client.adownload_file(bucket_name, object_name)
         return content_bytes.decode("utf-8")
 
+    def _build_open_file_window(self, content: str, *, offset: int = 0, limit: int = 800) -> dict[str, Any]:
+        lines = content.splitlines()
+        total_lines = len(lines)
+        start = min(max(int(offset), 0), total_lines)
+        window_size = min(max(int(limit), 1), 2000)
+        selected = lines[start : start + window_size]
+        end = start + len(selected)
+
+        return {
+            "start_line": start + 1 if selected else 0,
+            "end_line": end,
+            "total_lines": total_lines,
+            "offset": start,
+            "window_size": window_size,
+            "has_more_before": start > 0,
+            "has_more_after": end < total_lines,
+            "next_offset": end if end < total_lines else None,
+            "content": "\n".join(f"{start + idx + 1:6d}\t{line}" for idx, line in enumerate(selected)),
+        }
+
+    async def open_file_content(self, db_id: str, file_id: str, offset: int = 0, limit: int = 800) -> dict:
+        """按行窗口打开文件解析后的 Markdown 内容"""
+        file_meta = self.files_meta.get(file_id)
+        if file_meta is None:
+            raise Exception(f"文件不存在: {file_id}")
+        if file_meta.get("database_id") != db_id:
+            raise Exception(f"文件 {file_id} 不属于知识库 {db_id}")
+        if file_meta.get("is_folder"):
+            raise Exception(f"文件 {file_id} 是文件夹")
+
+        markdown_file = file_meta.get("markdown_file")
+        if not markdown_file:
+            raise Exception(f"文件 {file_id} 没有解析后的 Markdown 内容")
+
+        content = await self._read_markdown_from_minio(markdown_file)
+        return self._build_open_file_window(content, offset=offset, limit=limit)
+
     @abstractmethod
     async def index_file(self, db_id: str, file_id: str, operator_id: str | None = None) -> dict:
         """
diff --git a/backend/package/yuxi/knowledge/implementations/dify.py b/backend/package/yuxi/knowledge/implementations/dify.py
index e95551c5..09fb1b22 100644
--- a/backend/package/yuxi/knowledge/implementations/dify.py
+++ b/backend/package/yuxi/knowledge/implementations/dify.py
@@ -63,6 +63,10 @@ class DifyKB(KnowledgeBase):
     async def get_file_content(self, db_id: str, file_id: str) -> dict:
         raise self._readonly_error()
 
+    async def open_file_content(self, db_id: str, file_id: str, offset: int = 0, limit: int = 800) -> dict:
+        del offset, limit
+        raise self._readonly_error()
+
     async def get_file_info(self, db_id: str, file_id: str) -> dict:
         raise self._readonly_error()
 
diff --git a/backend/package/yuxi/knowledge/implementations/lightrag.py b/backend/package/yuxi/knowledge/implementations/lightrag.py
index 9e135c0f..815968cf 100644
--- a/backend/package/yuxi/knowledge/implementations/lightrag.py
+++ b/backend/package/yuxi/knowledge/implementations/lightrag.py
@@ -528,6 +528,36 @@ class LightRagKB(KnowledgeBase):
 
             return processed_items_info
 
+    @staticmethod
+    def _attach_file_ids_to_chunks(rag: LightRAG, chunks):
+        if not isinstance(chunks, list):
+            return chunks
+
+        text_chunks = getattr(rag, "text_chunks", None)
+        chunk_store = getattr(text_chunks, "_data", None)
+        if not isinstance(chunk_store, dict):
+            return chunks
+
+        for chunk in chunks:
+            if not isinstance(chunk, dict):
+                continue
+
+            metadata = chunk.get("metadata")
+            if not isinstance(metadata, dict):
+                metadata = {}
+
+            chunk_id = metadata.get("chunk_id") or chunk.get("chunk_id") or chunk.get("id")
+            if chunk_id and not metadata.get("chunk_id"):
+                metadata["chunk_id"] = str(chunk_id)
+
+            stored_chunk = chunk_store.get(chunk_id)
+            if isinstance(stored_chunk, dict) and stored_chunk.get("full_doc_id") and not metadata.get("file_id"):
+                metadata["file_id"] = str(stored_chunk["full_doc_id"])
+
+            chunk["metadata"] = metadata
+
+        return chunks
+
     async def aquery(self, query_text: str, db_id: str, agent_call: bool = False, **kwargs) -> str:
         """异步查询知识库"""
         rag = await self._get_lightrag_instance(db_id)
@@ -579,7 +609,7 @@ class LightRagKB(KnowledgeBase):
                 data = response.get("data", {}) or {}
 
                 if scope == "chunks":
-                    return data.get("chunks", [])
+                    return self._attach_file_ids_to_chunks(rag, data.get("chunks", []))
 
                 result = {}
                 if scope in ["graph", "all"]:
@@ -594,7 +624,7 @@ class LightRagKB(KnowledgeBase):
                     result["references"] = data.get("references", [])
 
                 if scope == "all":
-                    result["chunks"] = data.get("chunks", [])
+                    result["chunks"] = self._attach_file_ids_to_chunks(rag, data.get("chunks", []))
 
                 return result
 
diff --git a/backend/package/yuxi/knowledge/manager.py b/backend/package/yuxi/knowledge/manager.py
index 23f8b3e6..3dc2b4ad 100644
--- a/backend/package/yuxi/knowledge/manager.py
+++ b/backend/package/yuxi/knowledge/manager.py
@@ -505,6 +505,11 @@ class KnowledgeBaseManager:
         kb_instance = await self._get_kb_for_database(db_id)
         return await kb_instance.get_file_content(db_id, file_id)
 
+    async def open_file_content(self, db_id: str, file_id: str, offset: int = 0, limit: int = 800) -> dict:
+        """按行窗口打开文件解析后的 Markdown 内容"""
+        kb_instance = await self._get_kb_for_database(db_id)
+        return await kb_instance.open_file_content(db_id, file_id, offset, limit)
+
     async def get_file_info(self, db_id: str, file_id: str) -> dict:
         """获取文件完整信息（基本信息+内容信息）- 保持向后兼容"""
         kb_instance = await self._get_kb_for_database(db_id)
diff --git a/backend/test/unit/knowledge/test_lightrag_chunk_mapping.py b/backend/test/unit/knowledge/test_lightrag_chunk_mapping.py
new file mode 100644
index 00000000..d907249c
--- /dev/null
+++ b/backend/test/unit/knowledge/test_lightrag_chunk_mapping.py
@@ -0,0 +1,34 @@
+from __future__ import annotations
+
+from types import SimpleNamespace
+
+from yuxi.knowledge.implementations.lightrag import LightRagKB
+
+
+def test_lightrag_attaches_file_id_to_chunks_from_chunk_store() -> None:
+    rag = SimpleNamespace(
+        text_chunks=SimpleNamespace(
+            _data={
+                "chunk-1": {"full_doc_id": "file-1"},
+                "chunk-2": {"full_doc_id": "file-2"},
+            }
+        )
+    )
+    chunks = [
+        {"chunk_id": "chunk-1", "content": "one"},
+        {"id": "chunk-2", "content": "two", "metadata": {}},
+    ]
+
+    result = LightRagKB._attach_file_ids_to_chunks(rag, chunks)
+
+    assert result[0]["metadata"] == {"chunk_id": "chunk-1", "file_id": "file-1"}
+    assert result[1]["metadata"] == {"chunk_id": "chunk-2", "file_id": "file-2"}
+
+
+def test_lightrag_keeps_existing_file_id_when_mapping_chunks() -> None:
+    rag = SimpleNamespace(text_chunks=SimpleNamespace(_data={"chunk-1": {"full_doc_id": "file-1"}}))
+    chunks = [{"metadata": {"chunk_id": "chunk-1", "file_id": "existing-file"}}]
+
+    result = LightRagKB._attach_file_ids_to_chunks(rag, chunks)
+
+    assert result[0]["metadata"] == {"chunk_id": "chunk-1", "file_id": "existing-file"}
diff --git a/backend/test/unit/toolkits/test_kbs_tools.py b/backend/test/unit/toolkits/test_kbs_tools.py
index 888c8be0..b6851063 100644
--- a/backend/test/unit/toolkits/test_kbs_tools.py
+++ b/backend/test/unit/toolkits/test_kbs_tools.py
@@ -8,26 +8,59 @@ import pytest
 from yuxi.agents.toolkits.kbs import tools
 
 
+def _tool_callable(tool):
+    callback = getattr(tool, "coroutine", None)
+    if callback is not None:
+        return callback
+
+    callback = getattr(tool, "func", None)
+    if callback is not None:
+        return callback
+
+    raise AssertionError(f"{tool.name} tool has no callable entry")
+
+
 def _query_kb_callable():
-    callback = getattr(tools.query_kb, "coroutine", None)
-    if callback is not None:
-        return callback
-
-    callback = getattr(tools.query_kb, "func", None)
-    if callback is not None:
-        return callback
-
-    raise AssertionError("query_kb tool has no callable entry")
+    return _tool_callable(tools.query_kb)
 
 
-async def _run_query_kb(**kwargs):
-    callback = _query_kb_callable()
+def _open_kb_document_callable():
+    return _tool_callable(tools.open_kb_document)
+
+
+async def _run_tool(callback, **kwargs):
     result = callback(**kwargs)
     if inspect.isawaitable(result):
         return await result
     return result
 
 
+async def _run_query_kb(**kwargs):
+    return await _run_tool(_query_kb_callable(), **kwargs)
+
+
+async def _run_open_kb_document(**kwargs):
+    return await _run_tool(_open_kb_document_callable(), **kwargs)
+
+
+def _build_test_window(content: str, offset: int = 0, limit: int = 800) -> dict:
+    lines = content.splitlines()
+    start = min(max(offset, 0), len(lines))
+    selected = lines[start : start + limit]
+    end = start + len(selected)
+    return {
+        "start_line": start + 1 if selected else 0,
+        "end_line": end,
+        "total_lines": len(lines),
+        "offset": start,
+        "window_size": limit,
+        "has_more_before": start > 0,
+        "has_more_after": end < len(lines),
+        "next_offset": end if end < len(lines) else None,
+        "content": "\n".join(f"{start + idx + 1:6d}\t{line}" for idx, line in enumerate(selected)),
+    }
+
+
 @pytest.mark.asyncio
 async def test_query_kb_injects_filepath_into_chunk_metadata(monkeypatch) -> None:
     async def _fake_retriever(query_text: str, **kwargs):
@@ -209,3 +242,175 @@ async def test_query_kb_uses_backend_filepath_injector(monkeypatch) -> None:
 
     assert result[0]["metadata"]["filepath"] == "/home/gem/kbs/FAQ/auth-guide.pdf"
     assert result[0]["metadata"]["parsed_path"] == "/home/gem/kbs/FAQ/parsed/auth-guide.pdf.md"
+
+
+@pytest.mark.asyncio
+async def test_query_kb_normalizes_file_metadata_for_open(monkeypatch) -> None:
+    async def _fake_retriever(query_text: str, **kwargs):
+        assert query_text == "auth"
+        return [
+            {
+                "content": "auth guide",
+                "full_doc_id": "file-1",
+                "chunk_id": "chunk-1",
+                "chunk_index": 3,
+            }
+        ]
+
+    monkeypatch.setattr(
+        tools.knowledge_base,
+        "get_retrievers",
+        lambda: {
+            "db-1": {
+                "name": "FAQ",
+                "retriever": _fake_retriever,
+                "metadata": {"kb_type": "lightrag"},
+            }
+        },
+    )
+
+    async def _fake_visible_kbs(runtime):
+        return [{"db_id": "db-1", "name": "FAQ"}]
+
+    monkeypatch.setattr(tools, "_resolve_visible_knowledge_bases_for_query", _fake_visible_kbs)
+
+    runtime = SimpleNamespace(context=SimpleNamespace())
+    result = await _run_query_kb(kb_name="FAQ", query_text="auth", runtime=runtime)
+
+    assert result[0]["metadata"] == {
+        "file_id": "file-1",
+        "chunk_id": "chunk-1",
+        "chunk_index": 3,
+    }
+
+
+@pytest.mark.asyncio
+async def test_open_kb_document_reads_markdown_content_by_default_window(monkeypatch) -> None:
+    lines = [f"line {index}" for index in range(1, 1001)]
+
+    monkeypatch.setattr(
+        tools.knowledge_base,
+        "get_retrievers",
+        lambda: {
+            "db-1": {
+                "name": "FAQ",
+                "retriever": object(),
+                "metadata": {"kb_type": "milvus"},
+            }
+        },
+    )
+
+    async def _fake_visible_kbs(runtime):
+        return [{"db_id": "db-1", "name": "FAQ"}]
+
+    async def _fake_open_file_content(db_id: str, file_id: str, offset: int = 0, limit: int = 800):
+        assert db_id == "db-1"
+        assert file_id == "file-1"
+        return _build_test_window("\n".join(lines), offset=offset, limit=limit)
+
+    monkeypatch.setattr(tools, "_resolve_visible_knowledge_bases_for_query", _fake_visible_kbs)
+    monkeypatch.setattr(tools.knowledge_base, "open_file_content", _fake_open_file_content)
+
+    runtime = SimpleNamespace(context=SimpleNamespace())
+    result = await _run_open_kb_document(resource_id="db-1", file_id="file-1", runtime=runtime)
+
+    assert result["resource_id"] == "db-1"
+    assert result["file_id"] == "file-1"
+    assert result["start_line"] == 1
+    assert result["end_line"] == 800
+    assert result["total_lines"] == 1000
+    assert result["window_size"] == 800
+    assert result["has_more_before"] is False
+    assert result["has_more_after"] is True
+    assert result["next_offset"] == 800
+    assert "     1\tline 1" in result["content"]
+    assert "   800\tline 800" in result["content"]
+
+
+@pytest.mark.asyncio
+async def test_open_kb_document_prefers_line_over_offset(monkeypatch) -> None:
+    lines = [f"line {index}" for index in range(1, 1001)]
+
+    monkeypatch.setattr(
+        tools.knowledge_base,
+        "get_retrievers",
+        lambda: {
+            "db-1": {
+                "name": "FAQ",
+                "retriever": object(),
+                "metadata": {"kb_type": "milvus"},
+            }
+        },
+    )
+
+    async def _fake_visible_kbs(runtime):
+        return [{"db_id": "db-1", "name": "FAQ"}]
+
+    async def _fake_open_file_content(db_id: str, file_id: str, offset: int = 0, limit: int = 800):
+        assert db_id == "db-1"
+        assert file_id == "file-1"
+        return _build_test_window("\n".join(lines), offset=offset, limit=limit)
+
+    monkeypatch.setattr(tools, "_resolve_visible_knowledge_bases_for_query", _fake_visible_kbs)
+    monkeypatch.setattr(tools.knowledge_base, "open_file_content", _fake_open_file_content)
+
+    runtime = SimpleNamespace(context=SimpleNamespace())
+    result = await _run_open_kb_document(
+        resource_id="db-1",
+        file_id="file-1",
+        line=801,
+        offset=0,
+        window_size=10,
+        runtime=runtime,
+    )
+
+    assert result["offset"] == 800
+    assert result["start_line"] == 801
+    assert result["end_line"] == 810
+    assert result["has_more_before"] is True
+    assert result["has_more_after"] is True
+    assert result["next_offset"] == 810
+    assert "   801\tline 801" in result["content"]
+
+
+@pytest.mark.asyncio
+async def test_open_kb_document_rejects_invisible_resource(monkeypatch) -> None:
+    async def _fake_visible_kbs(runtime):
+        return [{"db_id": "db-2", "name": "FAQ"}]
+
+    monkeypatch.setattr(tools, "_resolve_visible_knowledge_bases_for_query", _fake_visible_kbs)
+
+    runtime = SimpleNamespace(context=SimpleNamespace())
+    result = await _run_open_kb_document(resource_id="db-1", file_id="file-1", runtime=runtime)
+
+    assert "不存在或当前会话未启用" in result
+
+
+@pytest.mark.asyncio
+async def test_open_kb_document_requires_markdown_content(monkeypatch) -> None:
+    monkeypatch.setattr(
+        tools.knowledge_base,
+        "get_retrievers",
+        lambda: {
+            "db-1": {
+                "name": "FAQ",
+                "retriever": object(),
+                "metadata": {"kb_type": "milvus"},
+            }
+        },
+    )
+
+    async def _fake_visible_kbs(runtime):
+        return [{"db_id": "db-1", "name": "FAQ"}]
+
+    async def _fake_open_file_content(db_id: str, file_id: str, offset: int = 0, limit: int = 800):
+        del db_id, file_id, offset, limit
+        raise Exception("文件 file-1 没有解析后的 Markdown 内容")
+
+    monkeypatch.setattr(tools, "_resolve_visible_knowledge_bases_for_query", _fake_visible_kbs)
+    monkeypatch.setattr(tools.knowledge_base, "open_file_content", _fake_open_file_content)
+
+    runtime = SimpleNamespace(context=SimpleNamespace())
+    result = await _run_open_kb_document(resource_id="db-1", file_id="file-1", runtime=runtime)
+
+    assert "没有解析后的 Markdown 内容" in result