diff --git a/backend/package/yuxi/agents/backends/__init__.py b/backend/package/yuxi/agents/backends/__init__.py
index a2a1b42f..c7e3b372 100644
--- a/backend/package/yuxi/agents/backends/__init__.py
+++ b/backend/package/yuxi/agents/backends/__init__.py
@@ -1,6 +1,7 @@
 from deepagents.backends import CompositeBackend, StateBackend
 
 from .composite import create_agent_composite_backend
+from .knowledge_base_backend import KBS_PATH, KnowledgeBaseReadonlyBackend, resolve_visible_knowledge_bases_for_context
 from .sandbox import (
     IDLE_CHECK_INTERVAL,
     LARGE_TOOL_RESULTS_DIR,
@@ -33,6 +34,8 @@ from .skills_backend import SelectedSkillsReadonlyBackend
 
 __all__ = [
     "CompositeBackend",
+    "KBS_PATH",
+    "KnowledgeBaseReadonlyBackend",
     "StateBackend",
     "SelectedSkillsReadonlyBackend",
     "create_agent_composite_backend",
@@ -47,6 +50,7 @@ __all__ = [
     "init_sandbox_provider",
     "shutdown_sandbox_provider",
     "resolve_virtual_path",
+    "resolve_visible_knowledge_bases_for_context",
     "virtual_path_for_thread_file",
     "sandbox_id_for_thread",
     "sandbox_user_data_dir",
diff --git a/backend/package/yuxi/agents/backends/composite.py b/backend/package/yuxi/agents/backends/composite.py
index 13ecc3be..013563f8 100644
--- a/backend/package/yuxi/agents/backends/composite.py
+++ b/backend/package/yuxi/agents/backends/composite.py
@@ -2,13 +2,15 @@ from __future__ import annotations
 
 from deepagents.backends.composite import (
     CompositeBackend,
-    _route_for_path,
     _remap_file_info_path,
+    _route_for_path,
     _strip_route_from_pattern,
 )
 from deepagents.backends.protocol import FileInfo
 
 from yuxi.agents.middlewares.skills_middleware import normalize_selected_skills
+
+from .knowledge_base_backend import KnowledgeBaseReadonlyBackend
 from .sandbox import ProvisionerSandboxBackend
 from .skills_backend import SelectedSkillsReadonlyBackend
 
@@ -92,12 +94,22 @@ def _extract_thread_id(runtime) -> str:
     raise ValueError("thread_id is required in runtime configurable context")
 
 
+def _get_visible_knowledge_bases_from_runtime(runtime) -> list[dict]:
+    context = getattr(runtime, "context", None)
+    selected = getattr(context, "_visible_knowledge_bases", None)
+    if isinstance(selected, list):
+        return selected
+    return []
+
+
 def create_agent_composite_backend(runtime) -> CompositeBackend:
     visible_skills = _get_visible_skills_from_runtime(runtime)
     thread_id = _extract_thread_id(runtime)
+    visible_kbs = _get_visible_knowledge_bases_from_runtime(runtime)
     return CustomCompositeBackend(
         default=ProvisionerSandboxBackend(thread_id=thread_id, visible_skills=visible_skills),
         routes={
             "/skills/": SelectedSkillsReadonlyBackend(selected_slugs=visible_skills),
+            "/home/yuxi/kbs/": KnowledgeBaseReadonlyBackend(visible_kbs=visible_kbs),
         },
     )
diff --git a/backend/package/yuxi/agents/backends/knowledge_base_backend.py b/backend/package/yuxi/agents/backends/knowledge_base_backend.py
new file mode 100644
index 00000000..d761cc72
--- /dev/null
+++ b/backend/package/yuxi/agents/backends/knowledge_base_backend.py
@@ -0,0 +1,459 @@
+from __future__ import annotations
+
+import fnmatch
+import re
+from collections import defaultdict
+from dataclasses import dataclass
+from pathlib import Path, PurePosixPath
+from typing import Any
+
+from deepagents.backends import FilesystemBackend
+from deepagents.backends.protocol import EditResult, FileDownloadResponse, FileInfo, FileUploadResponse, WriteResult
+
+from yuxi import config as conf
+from yuxi import knowledge_base
+from yuxi.knowledge.utils.kb_utils import is_minio_url, parse_minio_url
+from yuxi.storage.minio import get_minio_client
+
+KBS_PATH = "/home/yuxi/kbs"
+_INVALID_SEGMENT_RE = re.compile(r"[\\/\x00-\x1f\x7f]+")
+_WHITESPACE_RE = re.compile(r"\s+")
+
+
+@dataclass(frozen=True)
+class _MaterializedFile:
+    virtual_path: str
+    cache_path: Path
+    source_path: str
+    modified_at: str | None = None
+
+
+def _normalize_virtual_path(path: str | None) -> str:
+    raw = str(path or "").strip() or "/"
+    normalized = "/" + raw.lstrip("/")
+    pure = PurePosixPath(normalized)
+    if ".." in pure.parts:
+        raise ValueError("path traversal is not allowed")
+    return str(pure)
+
+
+def _sanitize_segment(value: str | None, fallback: str) -> str:
+    cleaned = str(value or "").strip()
+    cleaned = _INVALID_SEGMENT_RE.sub("_", cleaned)
+    cleaned = _WHITESPACE_RE.sub(" ", cleaned).strip()
+    if not cleaned or cleaned in {".", ".."}:
+        return fallback
+    return cleaned
+
+
+def _candidate_name(file_meta: dict[str, Any]) -> str:
+    filename = str(file_meta.get("filename") or "").strip()
+    if filename:
+        return filename
+
+    original = str(file_meta.get("original_filename") or "").strip()
+    if original:
+        return original
+
+    for key in ("path", "markdown_file"):
+        raw = str(file_meta.get(key) or "").strip()
+        if raw:
+            try:
+                parsed = PurePosixPath(raw)
+                name = parsed.name
+            except Exception:  # noqa: BLE001
+                name = ""
+            if name:
+                return name
+
+    return str(file_meta.get("file_id") or "")
+
+
+def _unique_name(base_name: str, *, stable_id: str, used_names: set[str]) -> str:
+    if base_name not in used_names:
+        used_names.add(base_name)
+        return base_name
+
+    suffix = f"__{stable_id[:8]}"
+    candidate = f"{base_name}{suffix}"
+    while candidate in used_names:
+        suffix = f"__{stable_id}"
+        candidate = f"{base_name}{suffix}"
+    used_names.add(candidate)
+    return candidate
+
+
+def _materialize_text_view(content: bytes, file_path: str, *, offset: int = 0, limit: int = 2000) -> str:
+    if not content:
+        return "System reminder: File exists but has empty contents"
+
+    if b"\x00" in content:
+        return f"Error: File '{file_path}' is binary and cannot be rendered as text"
+
+    try:
+        text = content.decode("utf-8")
+    except UnicodeDecodeError:
+        return f"Error: File '{file_path}' is binary and cannot be rendered as text"
+
+    lines = text.splitlines()
+    start = max(0, int(offset))
+    selected = lines[start : start + int(limit)]
+    return "\n".join(f"{start + idx + 1:6d}\t{line}" for idx, line in enumerate(selected))
+
+
+async def resolve_visible_knowledge_bases_for_context(context) -> list[dict[str, Any]]:
+    user_id = getattr(context, "user_id", None)
+    if not user_id:
+        setattr(context, "_visible_knowledge_bases", [])
+        return []
+
+    enabled_names = {str(name).strip() for name in (getattr(context, "knowledges", None) or []) if str(name).strip()}
+    if not enabled_names:
+        setattr(context, "_visible_knowledge_bases", [])
+        return []
+
+    try:
+        raw_user_id = int(user_id)
+    except (TypeError, ValueError):
+        setattr(context, "_visible_knowledge_bases", [])
+        return []
+
+    result = await knowledge_base.get_databases_by_raw_id(raw_user_id)
+    databases = [db for db in (result.get("databases") or []) if str(db.get("name") or "").strip() in enabled_names]
+    setattr(context, "_visible_knowledge_bases", databases)
+    return databases
+
+
+def _all_files_meta() -> dict[str, dict[str, Any]]:
+    aggregated: dict[str, dict[str, Any]] = {}
+    for kb_instance in getattr(knowledge_base, "kb_instances", {}).values():
+        for file_id, meta in getattr(kb_instance, "files_meta", {}).items():
+            aggregated[str(file_id)] = meta
+    return aggregated
+
+
+class KnowledgeBaseReadonlyBackend(FilesystemBackend):
+    def __init__(self, *, visible_kbs: list[dict[str, Any]] | None, cache_root: Path | str | None = None):
+        self._cache_root = Path(cache_root or (Path(conf.save_dir) / "knowledge_base_data" / "kb-cache")).resolve()
+        self._cache_root.mkdir(parents=True, exist_ok=True)
+        super().__init__(root_dir=self._cache_root, virtual_mode=True)
+        self._visible_kbs = list(visible_kbs or [])
+        self._entries_by_dir: dict[str, list[FileInfo]] = defaultdict(list)
+        self._dir_paths: set[str] = {"/"}
+        self._files: dict[str, _MaterializedFile] = {}
+        self._all_files: list[FileInfo] = []
+        self._build_virtual_tree()
+
+    def has_entries(self) -> bool:
+        return bool(self._visible_kbs)
+
+    def _build_virtual_tree(self) -> None:
+        kb_name_candidates = {
+            str(db.get("db_id") or db.get("name") or f"kb-{index}"): _sanitize_segment(
+                db.get("name"),
+                str(db.get("db_id") or f"kb-{index}"),
+            )
+            for index, db in enumerate(self._visible_kbs)
+        }
+        used_root_names: set[str] = set()
+        kb_virtual_names: dict[str, str] = {}
+        sorted_kbs = sorted(
+            self._visible_kbs,
+            key=lambda item: (str(item.get("name") or ""), str(item.get("db_id") or "")),
+        )
+        for db in sorted_kbs:
+            db_id = str(db.get("db_id") or "")
+            if not db_id:
+                continue
+            base_name = kb_name_candidates.get(db_id) or db_id
+            kb_virtual_names[db_id] = _unique_name(base_name, stable_id=db_id, used_names=used_root_names)
+
+        files_by_db: dict[str, dict[str, dict[str, Any]]] = defaultdict(dict)
+        for file_id, meta in _all_files_meta().items():
+            db_id = str(meta.get("database_id") or "")
+            if db_id in kb_virtual_names:
+                files_by_db[db_id][str(file_id)] = meta
+
+        for db_id, kb_virtual_name in kb_virtual_names.items():
+            kb_root = f"/{kb_virtual_name}"
+            self._add_entry("/", kb_root, is_dir=True)
+            records = files_by_db.get(db_id, {})
+            self._build_source_tree(db_id=db_id, kb_root=kb_root, records=records)
+            self._build_parsed_tree(db_id=db_id, kb_root=kb_root, records=records)
+
+        for path, entries in list(self._entries_by_dir.items()):
+            entries.sort(key=lambda item: str(item.get("path") or ""))
+            self._entries_by_dir[path] = entries
+        self._all_files = sorted(self._all_files, key=lambda item: str(item.get("path") or ""))
+
+    def _build_source_tree(self, *, db_id: str, kb_root: str, records: dict[str, dict[str, Any]]) -> None:
+        children_by_parent: dict[str | None, list[dict[str, Any]]] = defaultdict(list)
+        for file_id, meta in records.items():
+            parent_id = meta.get("parent_id")
+            children_by_parent[str(parent_id) if parent_id else None].append({"file_id": file_id, "meta": meta})
+
+        resolved_parent_paths: dict[str, str] = {}
+        resolved_source_names: dict[str, str] = {}
+
+        def walk(parent_id: str | None, parent_path: str) -> None:
+            siblings = children_by_parent.get(parent_id, [])
+            used_names: set[str] = set()
+            candidates: list[tuple[dict[str, Any], str]] = []
+            for item in siblings:
+                file_id = item["file_id"]
+                meta = item["meta"]
+                base_name = _sanitize_segment(_candidate_name(meta), file_id)
+                candidates.append((item, base_name))
+
+            for item, base_name in sorted(candidates, key=lambda pair: (pair[1], pair[0]["file_id"])):
+                file_id = item["file_id"]
+                meta = item["meta"]
+                unique_name = _unique_name(base_name, stable_id=file_id, used_names=used_names)
+                child_path = f"{parent_path.rstrip('/')}/{unique_name}" if parent_path != "/" else f"/{unique_name}"
+                if meta.get("is_folder"):
+                    modified_at = meta.get("updated_at") or meta.get("created_at")
+                    self._add_entry(parent_path, child_path, is_dir=True, modified_at=modified_at)
+                    walk(file_id, child_path)
+                    continue
+
+                self._add_entry(
+                    parent_path,
+                    child_path,
+                    is_dir=False,
+                    size=int(meta.get("size") or 0),
+                    modified_at=meta.get("updated_at") or meta.get("created_at"),
+                )
+                resolved_parent_paths[file_id] = parent_path
+                resolved_source_names[file_id] = unique_name
+                cache_path = self._cache_root / db_id / "source" / file_id / unique_name
+                self._files[child_path] = _MaterializedFile(
+                    virtual_path=child_path,
+                    cache_path=cache_path,
+                    source_path=str(meta.get("path") or ""),
+                    modified_at=meta.get("updated_at") or meta.get("created_at"),
+                )
+                self._all_files.append(
+                    {
+                        "path": child_path,
+                        "is_dir": False,
+                        "size": int(meta.get("size") or 0),
+                        "modified_at": str(meta.get("updated_at") or meta.get("created_at") or ""),
+                    }
+                )
+
+        walk(None, kb_root)
+        self._resolved_parent_paths = getattr(self, "_resolved_parent_paths", {})
+        self._resolved_parent_paths[db_id] = resolved_parent_paths
+        self._resolved_source_names = getattr(self, "_resolved_source_names", {})
+        self._resolved_source_names[db_id] = resolved_source_names
+
+    def _build_parsed_tree(self, *, db_id: str, kb_root: str, records: dict[str, dict[str, Any]]) -> None:
+        parsed_records = {
+            file_id: meta
+            for file_id, meta in records.items()
+            if not meta.get("is_folder") and str(meta.get("markdown_file") or "").strip()
+        }
+        if not parsed_records:
+            return
+
+        parsed_root = f"{kb_root}/parsed"
+        self._add_entry(kb_root, parsed_root, is_dir=True)
+        parent_paths = getattr(self, "_resolved_parent_paths", {}).get(db_id, {})
+        source_names = getattr(self, "_resolved_source_names", {}).get(db_id, {})
+
+        grouped: dict[str, list[tuple[str, dict[str, Any], str]]] = defaultdict(list)
+        for file_id, meta in parsed_records.items():
+            source_parent = parent_paths.get(file_id, kb_root)
+            parsed_parent = (
+                f"{parsed_root}{source_parent[len(kb_root) :]}" if source_parent.startswith(kb_root) else parsed_root
+            )
+            source_name = source_names.get(file_id) or _sanitize_segment(meta.get("filename"), file_id)
+            source_stem = PurePosixPath(source_name).stem or source_name or file_id
+            base_name = _sanitize_segment(f"{source_stem}.md", f"{file_id}.md")
+            grouped[parsed_parent].append((file_id, meta, base_name))
+
+        for parsed_parent, items in grouped.items():
+            current = PurePosixPath(parsed_parent)
+            while str(current) not in {"", "."} and str(current) != "/":
+                current_str = str(current)
+                parent_str = str(current.parent) if str(current.parent) != "." else "/"
+                if current_str not in self._dir_paths:
+                    self._add_entry(parent_str, current_str, is_dir=True)
+                current = current.parent
+
+            used_names: set[str] = set()
+            for file_id, meta, base_name in sorted(items, key=lambda item: (item[2], item[0])):
+                unique_name = _unique_name(base_name, stable_id=file_id, used_names=used_names)
+                file_path = f"{parsed_parent.rstrip('/')}/{unique_name}" if parsed_parent != "/" else f"/{unique_name}"
+                self._add_entry(
+                    parsed_parent,
+                    file_path,
+                    is_dir=False,
+                    size=0,
+                    modified_at=meta.get("updated_at") or meta.get("created_at"),
+                )
+                cache_path = self._cache_root / db_id / "parsed" / f"{file_id}.md"
+                self._files[file_path] = _MaterializedFile(
+                    virtual_path=file_path,
+                    cache_path=cache_path,
+                    source_path=str(meta.get("markdown_file") or ""),
+                    modified_at=meta.get("updated_at") or meta.get("created_at"),
+                )
+                self._all_files.append(
+                    {
+                        "path": file_path,
+                        "is_dir": False,
+                        "size": 0,
+                        "modified_at": str(meta.get("updated_at") or meta.get("created_at") or ""),
+                    }
+                )
+
+    def _add_entry(
+        self,
+        parent_path: str,
+        child_path: str,
+        *,
+        is_dir: bool,
+        size: int = 0,
+        modified_at: str | None = None,
+    ) -> None:
+        normalized_parent = _normalize_virtual_path(parent_path)
+        normalized_child = _normalize_virtual_path(child_path)
+        entry_path = f"{normalized_child}/" if is_dir else normalized_child
+        entry: FileInfo = {
+            "path": entry_path,
+            "is_dir": is_dir,
+            "size": int(size or 0),
+            "modified_at": str(modified_at or ""),
+        }
+        if entry_path not in {str(item.get("path")) for item in self._entries_by_dir[normalized_parent]}:
+            self._entries_by_dir[normalized_parent].append(entry)
+        if is_dir:
+            self._dir_paths.add(normalized_child)
+            self._entries_by_dir.setdefault(normalized_child, [])
+
+    def _ensure_local_file(self, descriptor: _MaterializedFile) -> Path:
+        if descriptor.cache_path.exists():
+            return descriptor.cache_path
+
+        source = descriptor.source_path.strip()
+        if not source:
+            raise FileNotFoundError(descriptor.virtual_path)
+        if not is_minio_url(source):
+            raise FileNotFoundError(descriptor.virtual_path)
+
+        bucket_name, object_name = parse_minio_url(source)
+        payload = get_minio_client().download_file(bucket_name, object_name)
+        descriptor.cache_path.parent.mkdir(parents=True, exist_ok=True)
+        descriptor.cache_path.write_bytes(payload)
+        return descriptor.cache_path
+
+    def ls_info(self, path: str) -> list[FileInfo]:
+        normalized_path = _normalize_virtual_path(path)
+        return list(self._entries_by_dir.get(normalized_path, []))
+
+    def read(self, file_path: str, offset: int = 0, limit: int = 2000) -> str:
+        normalized_path = _normalize_virtual_path(file_path)
+        descriptor = self._files.get(normalized_path)
+        if descriptor is None:
+            if normalized_path in self._dir_paths:
+                return f"Error: Path '{file_path}' is a directory"
+            return f"Error: File '{file_path}' not found"
+
+        try:
+            content = self._ensure_local_file(descriptor).read_bytes()
+        except FileNotFoundError:
+            return f"Error: File '{file_path}' not found"
+        except Exception as exc:  # noqa: BLE001
+            detail = str(exc).strip() or "unknown error"
+            return f"Error: Failed to read '{file_path}': {detail}"
+
+        return _materialize_text_view(content, file_path, offset=offset, limit=limit)
+
+    def glob_info(self, pattern: str, path: str = "/") -> list[FileInfo]:
+        normalized_path = _normalize_virtual_path(path)
+        if ".." in PurePosixPath(pattern).parts:
+            raise ValueError("Path traversal not allowed in glob pattern")
+        normalized_pattern = pattern.lstrip("/") or "*"
+        prefix = "/" if normalized_path == "/" else f"{normalized_path.rstrip('/')}/"
+
+        matches: list[FileInfo] = []
+        for item in self._all_files:
+            item_path = str(item.get("path") or "")
+            if normalized_path != "/" and not item_path.startswith(prefix):
+                continue
+            relative = item_path[len(prefix) :] if normalized_path != "/" else item_path.lstrip("/")
+            if fnmatch.fnmatch(relative, normalized_pattern):
+                matches.append(dict(item))
+        return matches
+
+    def grep_raw(self, pattern: str, path: str | None = None, glob: str | None = None) -> list[dict[str, Any]] | str:
+        normalized_path = _normalize_virtual_path(path or "/")
+        prefix = "/" if normalized_path == "/" else f"{normalized_path.rstrip('/')}/"
+        if normalized_path in self._files:
+            targets = [normalized_path]
+        else:
+            targets = [
+                item["path"]
+                for item in self._all_files
+                if normalized_path == "/" or str(item["path"]).startswith(prefix)
+            ]
+
+        matches: list[dict[str, Any]] = []
+        for target in targets:
+            display_target = str(target)
+            relative = display_target.lstrip("/") if normalized_path == "/" else display_target[len(prefix) :]
+            if glob and not fnmatch.fnmatch(relative, glob):
+                continue
+            descriptor = self._files.get(display_target)
+            if descriptor is None:
+                continue
+            try:
+                content = self._ensure_local_file(descriptor).read_bytes()
+                if b"\x00" in content:
+                    continue
+                text = content.decode("utf-8")
+            except Exception:  # noqa: BLE001
+                continue
+            for line_num, line in enumerate(text.splitlines(), start=1):
+                if pattern in line:
+                    matches.append({"path": display_target, "line": line_num, "text": line})
+        return matches
+
+    def write(self, file_path: str, content: str) -> WriteResult:
+        return WriteResult(error="Knowledge base path is read-only.")
+
+    def edit(self, file_path: str, old_string: str, new_string: str, replace_all: bool = False) -> EditResult:
+        return EditResult(error="Knowledge base path is read-only.")
+
+    def upload_files(self, files: list[tuple[str, bytes]]) -> list[FileUploadResponse]:
+        return [FileUploadResponse(path=path, error="permission_denied") for path, _content in files]
+
+    def download_files(self, paths: list[str]) -> list[FileDownloadResponse]:
+        responses: list[FileDownloadResponse] = []
+        for path in paths:
+            try:
+                normalized_path = _normalize_virtual_path(path)
+            except ValueError:
+                responses.append(FileDownloadResponse(path=path, content=None, error="invalid_path"))
+                continue
+
+            descriptor = self._files.get(normalized_path)
+            if descriptor is None:
+                if normalized_path in self._dir_paths:
+                    responses.append(FileDownloadResponse(path=path, content=None, error="is_directory"))
+                else:
+                    responses.append(FileDownloadResponse(path=path, content=None, error="file_not_found"))
+                continue
+
+            try:
+                content = self._ensure_local_file(descriptor).read_bytes()
+            except FileNotFoundError:
+                responses.append(FileDownloadResponse(path=path, content=None, error="file_not_found"))
+                continue
+            except ValueError:
+                responses.append(FileDownloadResponse(path=path, content=None, error="invalid_path"))
+                continue
+
+            responses.append(FileDownloadResponse(path=path, content=content, error=None))
+        return responses
diff --git a/backend/package/yuxi/agents/buildin/chatbot/graph.py b/backend/package/yuxi/agents/buildin/chatbot/graph.py
index c2e21744..6a0bfab1 100644
--- a/backend/package/yuxi/agents/buildin/chatbot/graph.py
+++ b/backend/package/yuxi/agents/buildin/chatbot/graph.py
@@ -39,7 +39,6 @@ class ChatbotAgent(BaseAgent):
             "你好，请介绍一下你自己",
             "帮我写一封商务邮件",
             "解释一下什么是机器学习",
-            "推荐几本好书",
             "创建一个冒泡排序 python 并保存结果",
         ]
     }
diff --git a/backend/package/yuxi/agents/middlewares/knowledge_base_middleware.py b/backend/package/yuxi/agents/middlewares/knowledge_base_middleware.py
index ebf63666..bd1b1ec7 100644
--- a/backend/package/yuxi/agents/middlewares/knowledge_base_middleware.py
+++ b/backend/package/yuxi/agents/middlewares/knowledge_base_middleware.py
@@ -1,7 +1,10 @@
 """知识库中间件 - 提供通用知识库工具"""
 
-from langchain.agents.middleware import AgentMiddleware
+from collections.abc import Callable
 
+from langchain.agents.middleware import AgentMiddleware, ModelRequest, ModelResponse
+
+from yuxi.agents.backends.knowledge_base_backend import resolve_visible_knowledge_bases_for_context
 from yuxi.agents.toolkits.kbs import get_common_kb_tools
 from yuxi.utils.logging_config import logger
 
@@ -21,3 +24,9 @@ class KnowledgeBaseMiddleware(AgentMiddleware):
         self.kb_tools = get_common_kb_tools()
         self.tools = self.kb_tools
         logger.debug(f"Initialized KnowledgeBaseMiddleware with {len(self.kb_tools)} tools")
+
+    async def awrap_model_call(
+        self, request: ModelRequest, handler: Callable[[ModelRequest], ModelResponse]
+    ) -> ModelResponse:
+        await resolve_visible_knowledge_bases_for_context(request.runtime.context)
+        return await handler(request)
diff --git a/backend/package/yuxi/services/filesystem_service.py b/backend/package/yuxi/services/filesystem_service.py
index c0e750b9..e80ca679 100644
--- a/backend/package/yuxi/services/filesystem_service.py
+++ b/backend/package/yuxi/services/filesystem_service.py
@@ -7,6 +7,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from yuxi.agents.backends import (
     ProvisionerSandboxBackend,
     create_agent_composite_backend,
+    resolve_visible_knowledge_bases_for_context,
 )
 from yuxi.agents.backends.sandbox.backend import _looks_like_binary
 from yuxi.agents.context import BaseContext
@@ -64,6 +65,7 @@ async def _resolve_filesystem_state(
     )
     runtime_context.thread_id = thread_id
     runtime_context.user_id = str(user.id)
+    await resolve_visible_knowledge_bases_for_context(runtime_context)
 
     sandbox_backend = ProvisionerSandboxBackend(thread_id=thread_id)
     return conversation, runtime_context, sandbox_backend
diff --git a/backend/package/yuxi/services/viewer_filesystem_service.py b/backend/package/yuxi/services/viewer_filesystem_service.py
index 748f4572..e464c53d 100644
--- a/backend/package/yuxi/services/viewer_filesystem_service.py
+++ b/backend/package/yuxi/services/viewer_filesystem_service.py
@@ -9,6 +9,7 @@ from urllib.parse import quote
 from fastapi import HTTPException
 from fastapi.responses import FileResponse, StreamingResponse
 from sqlalchemy.ext.asyncio import AsyncSession
+from yuxi.agents.backends import KBS_PATH, KnowledgeBaseReadonlyBackend, resolve_visible_knowledge_bases_for_context
 from yuxi.agents.backends.sandbox import SKILLS_PATH, USER_DATA_PATH, resolve_virtual_path
 from yuxi.agents.backends.skills_backend import SelectedSkillsReadonlyBackend
 from yuxi.agents.middlewares.skills_middleware import normalize_selected_skills
@@ -20,7 +21,7 @@ def _normalize_path(path: str | None) -> str:
     normalized = (path or "/").strip() or "/"
     if not normalized.startswith("/"):
         normalized = f"/{normalized}"
-    return normalized.rstrip("/") if normalized not in {"/", SKILLS_PATH, USER_DATA_PATH} else normalized
+    return normalized.rstrip("/") if normalized not in {"/", KBS_PATH, SKILLS_PATH, USER_DATA_PATH} else normalized
 
 
 def _is_user_data_path(path: str) -> bool:
@@ -31,16 +32,26 @@ def _is_skills_path(path: str) -> bool:
     return path == SKILLS_PATH or path.startswith(f"{SKILLS_PATH}/")
 
 
+def _is_kbs_path(path: str) -> bool:
+    return path == KBS_PATH or path.startswith(f"{KBS_PATH}/")
+
+
 def _strip_skills_prefix(path: str) -> str:
     if path == SKILLS_PATH:
         return "/"
     return path[len(SKILLS_PATH) :] or "/"
 
 
-def _remap_skills_entry(entry: dict) -> dict:
+def _strip_kbs_prefix(path: str) -> str:
+    if path == KBS_PATH:
+        return "/"
+    return path[len(KBS_PATH) :] or "/"
+
+
+def _remap_prefixed_entry(entry: dict, prefix: str) -> dict:
     raw_path = str(entry.get("path") or "")
     is_dir = bool(entry.get("is_dir", False))
-    remapped = f"{SKILLS_PATH}{raw_path}" if raw_path != "/" else f"{SKILLS_PATH}/"
+    remapped = f"{prefix}{raw_path}" if raw_path != "/" else f"{prefix}/"
     if is_dir and not remapped.endswith("/"):
         remapped = f"{remapped}/"
     return {
@@ -89,9 +100,11 @@ async def _resolve_viewer_state(
         agent_id=agent_id,
         agent_config_id=agent_config_id,
     )
+    visible_kbs = await resolve_visible_knowledge_bases_for_context(runtime_context)
     selected_skills = normalize_selected_skills(getattr(runtime_context, "skills", None) or [])
     skills_backend = SelectedSkillsReadonlyBackend(selected_slugs=selected_skills)
-    return sandbox_backend, skills_backend, selected_skills
+    kb_backend = KnowledgeBaseReadonlyBackend(visible_kbs=visible_kbs)
+    return sandbox_backend, skills_backend, kb_backend, selected_skills
 
 
 async def list_viewer_filesystem_tree(
@@ -107,7 +120,7 @@ async def list_viewer_filesystem_tree(
         raise HTTPException(status_code=422, detail="thread_id 不能为空")
 
     normalized_path = _normalize_path(path)
-    sandbox_backend, skills_backend, selected_skills = await _resolve_viewer_state(
+    sandbox_backend, skills_backend, kb_backend, selected_skills = await _resolve_viewer_state(
         thread_id=thread_id,
         agent_id=agent_id,
         agent_config_id=agent_config_id,
@@ -119,6 +132,8 @@ async def list_viewer_filesystem_tree(
         entries = [{"path": f"{USER_DATA_PATH}/", "name": "user-data", "is_dir": True, "size": 0, "modified_at": ""}]
         if selected_skills:
             entries.append({"path": f"{SKILLS_PATH}/", "name": "skills", "is_dir": True, "size": 0, "modified_at": ""})
+        if kb_backend.has_entries():
+            entries.append({"path": f"{KBS_PATH}/", "name": "kbs", "is_dir": True, "size": 0, "modified_at": ""})
         return {"entries": entries}
 
     try:
@@ -128,7 +143,10 @@ async def list_viewer_filesystem_tree(
 
         if _is_skills_path(normalized_path):
             entries = await asyncio.to_thread(skills_backend.ls_info, _strip_skills_prefix(normalized_path))
-            return {"entries": [_remap_skills_entry(entry) for entry in entries]}
+            return {"entries": [_remap_prefixed_entry(entry, SKILLS_PATH) for entry in entries]}
+        if _is_kbs_path(normalized_path):
+            entries = await asyncio.to_thread(kb_backend.ls_info, _strip_kbs_prefix(normalized_path))
+            return {"entries": [_remap_prefixed_entry(entry, KBS_PATH) for entry in entries]}
     except PermissionError as e:
         raise HTTPException(status_code=400, detail=str(e)) from e
     except ValueError as e:
@@ -150,7 +168,7 @@ async def read_viewer_file_content(
         raise HTTPException(status_code=422, detail="thread_id 不能为空")
     normalized_path = _normalize_path(path)
 
-    sandbox_backend, skills_backend, _selected_skills = await _resolve_viewer_state(
+    sandbox_backend, skills_backend, kb_backend, _selected_skills = await _resolve_viewer_state(
         thread_id=thread_id,
         agent_id=agent_id,
         agent_config_id=agent_config_id,
@@ -163,6 +181,8 @@ async def read_viewer_file_content(
             responses = await asyncio.to_thread(sandbox_backend.download_files, [normalized_path])
         elif _is_skills_path(normalized_path):
             responses = await asyncio.to_thread(skills_backend.download_files, [_strip_skills_prefix(normalized_path)])
+        elif _is_kbs_path(normalized_path):
+            responses = await asyncio.to_thread(kb_backend.download_files, [_strip_kbs_prefix(normalized_path)])
         else:
             raise HTTPException(
                 status_code=400,
@@ -199,7 +219,7 @@ async def download_viewer_file(
     db: AsyncSession,
 ) -> StreamingResponse:
     normalized_path = _normalize_path(path)
-    _sandbox_backend, skills_backend, _selected_skills = await _resolve_viewer_state(
+    _sandbox_backend, skills_backend, kb_backend, _selected_skills = await _resolve_viewer_state(
         thread_id=thread_id,
         agent_id=agent_id,
         agent_config_id=agent_config_id,
@@ -224,6 +244,8 @@ async def download_viewer_file(
 
         if _is_skills_path(normalized_path):
             responses = await asyncio.to_thread(skills_backend.download_files, [_strip_skills_prefix(normalized_path)])
+        elif _is_kbs_path(normalized_path):
+            responses = await asyncio.to_thread(kb_backend.download_files, [_strip_kbs_prefix(normalized_path)])
         else:
             raise HTTPException(
                 status_code=400,
diff --git a/backend/test/api/test_viewer_filesystem_router.py b/backend/test/api/test_viewer_filesystem_router.py
index 31a82cd0..ff713808 100644
--- a/backend/test/api/test_viewer_filesystem_router.py
+++ b/backend/test/api/test_viewer_filesystem_router.py
@@ -2,10 +2,10 @@
 
 from __future__ import annotations
 
+import importlib
 import uuid
 
 import pytest
-
 from yuxi.agents.backends.sandbox import ensure_thread_dirs, sandbox_workspace_dir, virtual_path_for_thread_file
 
 pytestmark = [pytest.mark.asyncio, pytest.mark.integration]
@@ -44,7 +44,13 @@ async def _create_thread_for_user(test_client, headers: dict[str, str]) -> str:
     return thread_id
 
 
-async def _upload_attachment_file(test_client, thread_id: str, headers: dict[str, str], file_name: str, content: str) -> str:
+async def _upload_attachment_file(
+    test_client,
+    thread_id: str,
+    headers: dict[str, str],
+    file_name: str,
+    content: str,
+) -> str:
     response = await test_client.post(
         f"/api/chat/thread/{thread_id}/attachments",
         files={"file": (file_name, content.encode("utf-8"), "text/plain")},
@@ -110,6 +116,7 @@ async def test_viewer_download_returns_attachment_response(test_client, standard
     assert "download_demo" in content_disposition
     assert "download-me" in response.text
 
+
 async def test_viewer_download_returns_full_file_for_large_user_data_content(test_client, standard_user):
     headers = standard_user["headers"]
     thread_id = await _create_thread_for_user(test_client, headers)
@@ -128,3 +135,47 @@ async def test_viewer_download_returns_full_file_for_large_user_data_content(tes
     assert response.status_code == 200, response.text
     assert response.content == large_content.encode("utf-8")
 
+
+async def test_viewer_tree_root_lists_kbs_namespace_when_visible(test_client, standard_user, monkeypatch):
+    headers = standard_user["headers"]
+    thread_id = await _create_thread_for_user(test_client, headers)
+
+    async def _fake_list_viewer_filesystem_tree(**kwargs):
+        return {
+            "entries": [
+                {"path": "/home/yuxi/user-data/", "name": "user-data", "is_dir": True, "size": 0, "modified_at": ""},
+                {"path": "/home/yuxi/kbs/", "name": "kbs", "is_dir": True, "size": 0, "modified_at": ""},
+            ]
+        }
+
+    router_module = importlib.import_module("server.routers.filesystem_router")
+    monkeypatch.setitem(
+        router_module.get_viewer_tree.__globals__,
+        "list_viewer_filesystem_tree",
+        _fake_list_viewer_filesystem_tree,
+    )
+
+    response = await test_client.get(
+        "/api/viewer/filesystem/tree",
+        params={"thread_id": thread_id, "path": "/"},
+        headers=headers,
+    )
+    assert response.status_code == 200, response.text
+
+    entries = response.json().get("entries", [])
+    paths = {entry.get("path") for entry in entries}
+    assert "/home/yuxi/kbs/" in paths
+
+
+async def test_viewer_can_list_and_read_kbs_namespace(test_client, standard_user):
+    headers = standard_user["headers"]
+    thread_id = await _create_thread_for_user(test_client, headers)
+
+    tree_response = await test_client.get(
+        "/api/viewer/filesystem/tree",
+        params={"thread_id": thread_id, "path": "/home/yuxi/kbs"},
+        headers=headers,
+    )
+    assert tree_response.status_code == 200, tree_response.text
+    entries = tree_response.json().get("entries", [])
+    assert any(str(entry.get("path", "")).startswith("/home/yuxi/kbs/") for entry in entries)
diff --git a/backend/test/test_knowledge_base_backend.py b/backend/test/test_knowledge_base_backend.py
new file mode 100644
index 00000000..7af0fe2f
--- /dev/null
+++ b/backend/test/test_knowledge_base_backend.py
@@ -0,0 +1,106 @@
+from __future__ import annotations
+
+from types import SimpleNamespace
+
+import pytest
+from yuxi.agents.backends.knowledge_base_backend import (
+    KnowledgeBaseReadonlyBackend,
+    resolve_visible_knowledge_bases_for_context,
+)
+
+
+def test_knowledge_base_backend_builds_virtual_tree_and_materializes_files(monkeypatch, tmp_path) -> None:
+    visible_kbs = [
+        {"db_id": "db-1", "name": "FAQ"},
+        {"db_id": "db-2", "name": "FAQ"},
+    ]
+    files_meta = {
+        "folder-api": {
+            "file_id": "folder-api",
+            "database_id": "db-1",
+            "parent_id": None,
+            "filename": "API",
+            "is_folder": True,
+            "created_at": "2026-03-26T00:00:00Z",
+        },
+        "file-pdf": {
+            "file_id": "file-pdf",
+            "database_id": "db-1",
+            "parent_id": "folder-api",
+            "filename": "auth-guide.pdf",
+            "path": "http://minio/kb-source/db-1/upload/auth-guide.pdf",
+            "markdown_file": "http://minio/kb-parsed/db-1/parsed/file-pdf.md",
+            "size": 12,
+            "is_folder": False,
+            "created_at": "2026-03-26T00:00:00Z",
+        },
+        "file-pdf-2": {
+            "file_id": "file-pdf-2",
+            "database_id": "db-1",
+            "parent_id": "folder-api",
+            "filename": "auth-guide.pdf",
+            "path": "http://minio/kb-source/db-1/upload/auth-guide-2.pdf",
+            "size": 7,
+            "is_folder": False,
+            "created_at": "2026-03-26T00:00:00Z",
+        },
+        "file-db2": {
+            "file_id": "file-db2",
+            "database_id": "db-2",
+            "parent_id": None,
+            "filename": "overview.txt",
+            "path": "http://minio/kb-source/db-2/upload/overview.txt",
+            "size": 5,
+            "is_folder": False,
+            "created_at": "2026-03-26T00:00:00Z",
+        },
+    }
+    monkeypatch.setattr("yuxi.agents.backends.knowledge_base_backend._all_files_meta", lambda: files_meta)
+
+    class _FakeMinio:
+        def download_file(self, bucket_name: str, object_name: str) -> bytes:
+            return f"{bucket_name}:{object_name}".encode()
+
+    monkeypatch.setattr("yuxi.agents.backends.knowledge_base_backend.get_minio_client", lambda: _FakeMinio())
+
+    backend = KnowledgeBaseReadonlyBackend(visible_kbs=visible_kbs, cache_root=tmp_path)
+
+    root_entries = {entry["path"] for entry in backend.ls_info("/")}
+    assert "/FAQ/" in root_entries
+    assert "/FAQ__db-2/" in root_entries
+
+    faq_entries = {entry["path"] for entry in backend.ls_info("/FAQ")}
+    assert "/FAQ/API/" in faq_entries
+    assert "/FAQ/parsed/" in faq_entries
+
+    api_entries = {entry["path"] for entry in backend.ls_info("/FAQ/API")}
+    assert "/FAQ/API/auth-guide.pdf" in api_entries
+    assert any(path.startswith("/FAQ/API/auth-guide.pdf__file-pdf") for path in api_entries)
+
+    parsed_entries = {entry["path"] for entry in backend.ls_info("/FAQ/parsed/API")}
+    assert "/FAQ/parsed/API/auth-guide.md" in parsed_entries
+
+    responses = backend.download_files(["/FAQ/API/auth-guide.pdf", "/FAQ/parsed/API/auth-guide.md"])
+    assert responses[0].content == b"kb-source:db-1/upload/auth-guide.pdf"
+    assert responses[1].content == b"kb-parsed:db-1/parsed/file-pdf.md"
+
+    assert "kb-source" in backend.read("/FAQ/API/auth-guide.pdf")
+    assert backend.write("/FAQ/API/new.txt", "x").error == "Knowledge base path is read-only."
+
+
+@pytest.mark.asyncio
+async def test_resolve_visible_knowledge_bases_for_context_filters_by_enabled_names(monkeypatch) -> None:
+    async def _fake_get_databases_by_raw_id(user_id: int) -> dict:
+        assert user_id == 7
+        return {"databases": [{"db_id": "db-1", "name": "Alpha"}, {"db_id": "db-2", "name": "Beta"}]}
+
+    monkeypatch.setattr(
+        "yuxi.agents.backends.knowledge_base_backend.knowledge_base.get_databases_by_raw_id",
+        _fake_get_databases_by_raw_id,
+    )
+
+    context = SimpleNamespace(user_id="7", knowledges=["Beta"])
+    visible = await resolve_visible_knowledge_bases_for_context(context)
+
+    assert visible == [{"db_id": "db-2", "name": "Beta"}]
+    assert getattr(context, "_visible_knowledge_bases") == visible
diff --git a/backend/test/test_sandbox_backends.py b/backend/test/test_sandbox_backends.py
index b19c89d7..225733c9 100644
--- a/backend/test/test_sandbox_backends.py
+++ b/backend/test/test_sandbox_backends.py
@@ -5,29 +5,36 @@ from __future__ import annotations
 from types import MethodType, SimpleNamespace
 
 import pytest
-
 from yuxi.agents.backends.composite import create_agent_composite_backend
 from yuxi.agents.backends.sandbox import resolve_virtual_path, sandbox_id_for_thread
 from yuxi.agents.backends.sandbox.backend import ProvisionerSandboxBackend
 from yuxi.agents.middlewares.skills_middleware import SkillsMiddleware
 
 
-def _runtime(*, thread_id: str | None = "thread-1", skills: list[str] | None = None):
+def _runtime(
+    *,
+    thread_id: str | None = "thread-1",
+    skills: list[str] | None = None,
+    visible_kbs: list[dict] | None = None,
+):
     configurable = {"thread_id": thread_id} if thread_id else {}
     return SimpleNamespace(
         config={"configurable": configurable},
-        context=SimpleNamespace(skills=skills or []),
+        context=SimpleNamespace(skills=skills or [], _visible_knowledge_bases=visible_kbs or []),
     )
 
 
 def test_create_agent_composite_backend_uses_provisioner_default(monkeypatch):
     monkeypatch.setattr("yuxi.agents.backends.sandbox.backend.get_sandbox_provider", lambda: object())
 
-    backend = create_agent_composite_backend(_runtime(skills=["reporter"]))
+    backend = create_agent_composite_backend(
+        _runtime(skills=["reporter"], visible_kbs=[{"db_id": "db-1", "name": "Docs"}])
+    )
 
     assert isinstance(backend.default, ProvisionerSandboxBackend)
     assert backend.default._visible_skills == ["reporter"]
     assert "/skills/" in backend.routes
+    assert "/home/yuxi/kbs/" in backend.routes
 
 
 def test_create_agent_composite_backend_requires_thread_id():
diff --git a/docs/develop-guides/roadmap.md b/docs/develop-guides/roadmap.md
index 23d861ed..5391ca21 100644
--- a/docs/develop-guides/roadmap.md
+++ b/docs/develop-guides/roadmap.md
@@ -45,6 +45,8 @@
 
 ### 修复
 
+- 为沙盒与 viewer 文件系统补齐知识库只读映射：新增 `/home/yuxi/kbs` 命名空间，按“用户可访问知识库 ∩ 当前 Agent 已启用知识库”暴露原始文件与解析后的 Markdown，并补充对应后端与 viewer 路由测试
+
 <!-- 添加到这里 -->