diff --git a/__init__.py b/__init__.py
index edad52f..9810a2e 100644
--- a/__init__.py
+++ b/__init__.py
@@ -49,10 +49,8 @@ def _get_provider_class(provider_type: ProviderType):
 
         return SearchBackend
     if provider_type == ProviderType.PLAN:
-
         return PlanBackend
     if provider_type == ProviderType.CODE:
-
         return CodeBackend
     return VanillaBackend
 
diff --git a/backends/code_backend.py b/backends/code_backend.py
index 9804cc0..455d7dc 100644
--- a/backends/code_backend.py
+++ b/backends/code_backend.py
@@ -39,7 +39,9 @@ def _schema_to_python_type(schema):
 
     if "anyOf" in schema or "oneOf" in schema:
         variants = schema.get("anyOf") or schema.get("oneOf", [])
-        mapped = [_schema_to_python_type(v) for v in variants if v.get("type") != "null"]
+        mapped = [
+            _schema_to_python_type(v) for v in variants if v.get("type") != "null"
+        ]
         has_null = any(v.get("type") == "null" for v in variants)
         if not mapped:
             return "None" if has_null else "Any"
@@ -81,13 +83,19 @@ def _build_stub(tool):
     params = []
     for name, prop in properties.items():
         type_str = _schema_to_python_type(prop)
-        params.append(f"{name}: {type_str}" if name in required else f"{name}: {type_str} = None")
+        params.append(
+            f"{name}: {type_str}" if name in required else f"{name}: {type_str} = None"
+        )
 
     req = [p for p in params if "= None" not in p]
     opt = [p for p in params if "= None" in p]
     all_params = req + opt
 
-    sig = f"async def {tool.name}(*, {', '.join(all_params)})" if all_params else f"async def {tool.name}()"
+    sig = (
+        f"async def {tool.name}(*, {', '.join(all_params)})"
+        if all_params
+        else f"async def {tool.name}()"
+    )
     sig += " -> dict:"
 
     doc_lines = []
@@ -172,7 +180,6 @@ def _build_stub(tool):
 
 
 class CodeBackend(BaseProvider):
-
     def initialize(self, config):
         self._config = config
         self._tools = []
@@ -205,12 +212,15 @@ async def call_tool(tool_name, arguments):
         module = pytypes.ModuleType("tools")
 
         for tool in self._tools:
+
             def _make_stub(t):
                 async def stub(**kwargs):
                     return await call_tool(t.name, kwargs)
+
                 stub.__name__ = t.name
                 stub.__doc__ = t.description
                 return stub
+
             setattr(module, tool.name, _make_stub(tool))
 
         return module
@@ -240,7 +250,9 @@ def search_tools(query):
             for info in tool_index.values():
                 text = f"{info['name']} {info['description'] or ''}".lower()
                 if query_lower in text:
-                    results.append({"name": info["name"], "description": info["description"]})
+                    results.append(
+                        {"name": info["name"], "description": info["description"]}
+                    )
             return results
 
         module.list_tools = list_tools
@@ -317,24 +329,98 @@ def serve_resources(self):
         return [(resource, read_result)]
 
     async def _execute_code(self, code: str, timeout: int = 30) -> dict:
-        _safe_builtins = {k: v for k, v in __builtins__.items() if k not in (
-            "__import__", "exec", "eval", "compile", "open",
-            "breakpoint", "exit", "quit", "globals", "locals",
-            "getattr", "setattr", "delattr", "vars", "dir",
-            "memoryview", "type", "__build_class__",
-        )} if isinstance(__builtins__, dict) else {k: getattr(__builtins__, k) for k in (
-            "print", "len", "range", "enumerate", "zip", "map", "filter",
-            "sorted", "reversed", "list", "dict", "set", "tuple", "str",
-            "int", "float", "bool", "bytes", "bytearray",
-            "min", "max", "sum", "abs", "round", "pow", "divmod",
-            "any", "all", "isinstance", "issubclass", "hasattr",
-            "repr", "format", "hash", "id", "callable",
-            "iter", "next", "slice", "frozenset", "complex",
-            "chr", "ord", "hex", "oct", "bin",
-            "ValueError", "TypeError", "KeyError", "IndexError",
-            "AttributeError", "RuntimeError", "StopIteration",
-            "Exception", "BaseException", "True", "False", "None",
-        ) if hasattr(__builtins__, k)}
+        _safe_builtins = (
+            {
+                k: v
+                for k, v in __builtins__.items()
+                if k
+                not in (
+                    "__import__",
+                    "exec",
+                    "eval",
+                    "compile",
+                    "open",
+                    "breakpoint",
+                    "exit",
+                    "quit",
+                    "globals",
+                    "locals",
+                    "getattr",
+                    "setattr",
+                    "delattr",
+                    "vars",
+                    "dir",
+                    "memoryview",
+                    "type",
+                    "__build_class__",
+                )
+            }
+            if isinstance(__builtins__, dict)
+            else {
+                k: getattr(__builtins__, k)
+                for k in (
+                    "print",
+                    "len",
+                    "range",
+                    "enumerate",
+                    "zip",
+                    "map",
+                    "filter",
+                    "sorted",
+                    "reversed",
+                    "list",
+                    "dict",
+                    "set",
+                    "tuple",
+                    "str",
+                    "int",
+                    "float",
+                    "bool",
+                    "bytes",
+                    "bytearray",
+                    "min",
+                    "max",
+                    "sum",
+                    "abs",
+                    "round",
+                    "pow",
+                    "divmod",
+                    "any",
+                    "all",
+                    "isinstance",
+                    "issubclass",
+                    "hasattr",
+                    "repr",
+                    "format",
+                    "hash",
+                    "id",
+                    "callable",
+                    "iter",
+                    "next",
+                    "slice",
+                    "frozenset",
+                    "complex",
+                    "chr",
+                    "ord",
+                    "hex",
+                    "oct",
+                    "bin",
+                    "ValueError",
+                    "TypeError",
+                    "KeyError",
+                    "IndexError",
+                    "AttributeError",
+                    "RuntimeError",
+                    "StopIteration",
+                    "Exception",
+                    "BaseException",
+                    "True",
+                    "False",
+                    "None",
+                )
+                if hasattr(__builtins__, k)
+            }
+        )
         namespace = {"__builtins__": _safe_builtins}
 
         # Inject modules — user code calls tools.X(), runtime.Y()
@@ -343,7 +429,6 @@ async def _execute_code(self, code: str, timeout: int = 30) -> dict:
         namespace["tools"] = self._tools_module
         namespace["runtime"] = self._runtime_module
 
-
         indented = textwrap.indent(code, "    ")
         wrapped = f"async def __user_main__():\n{indented}\n"
 
@@ -354,8 +439,10 @@ async def _execute_code(self, code: str, timeout: int = 30) -> dict:
             compiled = compile(wrapped, "<user_code>", "exec")
             exec(compiled, namespace)
 
-            with contextlib.redirect_stdout(stdout_capture), \
-                 contextlib.redirect_stderr(stderr_capture):
+            with (
+                contextlib.redirect_stdout(stdout_capture),
+                contextlib.redirect_stderr(stderr_capture),
+            ):
                 await asyncio.wait_for(
                     namespace["__user_main__"](),
                     timeout=timeout,