Adds Kubernetes sandbox provisioner support (#35)

* Adds Kubernetes sandbox provisioner support

* Improves Docker dev setup by standardizing host paths

Replaces hardcoded host paths with a configurable root directory,
making the development environment more portable and easier to use
across different machines. Automatically sets the root path if not
already defined, reducing manual setup steps.

backend/src/sandbox/__init__.py

@@ -1,7 +1,10 @@
+from .consts import THREAD_DATA_BASE_DIR, VIRTUAL_PATH_PREFIX
 from .sandbox import Sandbox
 from .sandbox_provider import SandboxProvider, get_sandbox_provider
 
 __all__ = [
+    "THREAD_DATA_BASE_DIR",
+    "VIRTUAL_PATH_PREFIX",
     "Sandbox",
     "SandboxProvider",
     "get_sandbox_provider",

backend/src/sandbox/consts.py

@@ -0,0 +1,4 @@
+# Base directory for thread data (relative to backend/)
+THREAD_DATA_BASE_DIR = ".deer-flow/threads"
+# Virtual path prefix used in sandbox environments
+VIRTUAL_PATH_PREFIX = "/mnt/user-data"

backend/src/sandbox/local/local_sandbox.py

@@ -173,3 +173,11 @@ class LocalSandbox(Sandbox):
         mode = "a" if append else "w"
         with open(resolved_path, mode) as f:
             f.write(content)
+
+    def update_file(self, path: str, content: bytes) -> None:
+        resolved_path = self._resolve_path(path)
+        dir_path = os.path.dirname(resolved_path)
+        if dir_path:
+            os.makedirs(dir_path, exist_ok=True)
+        with open(resolved_path, "wb") as f:
+            f.write(content)

backend/src/sandbox/sandbox.py

@@ -60,3 +60,13 @@ class Sandbox(ABC):
             append: Whether to append the content to the file. If False, the file will be created or overwritten.
         """
         pass
+
+    @abstractmethod
+    def update_file(self, path: str, content: bytes) -> None:
+        """Update a file with binary content.
+
+        Args:
+            path: The absolute path of the file to update.
+            content: The binary content to write to the file.
+        """
+        pass

backend/src/sandbox/tools.py

@@ -4,6 +4,7 @@ from langchain.tools import ToolRuntime, tool
 from langgraph.typing import ContextT
 
 from src.agents.thread_state import ThreadDataState, ThreadState
+from src.sandbox.consts import VIRTUAL_PATH_PREFIX
 from src.sandbox.exceptions import (
     SandboxError,
     SandboxNotFoundError,
@@ -12,9 +13,6 @@ from src.sandbox.exceptions import (
 from src.sandbox.sandbox import Sandbox
 from src.sandbox.sandbox_provider import get_sandbox_provider
 
-# Virtual path prefix used in sandbox environments
-VIRTUAL_PATH_PREFIX = "/mnt/user-data"
-
 
 def replace_virtual_path(path: str, thread_data: ThreadDataState | None) -> str:
     """Replace virtual /mnt/user-data paths with actual thread data paths.