diff --git a/modal/_container_io_manager.py b/modal/_container_io_manager.py
index 4cd83d052..034f109bb 100644
--- a/modal/_container_io_manager.py
+++ b/modal/_container_io_manager.py
@@ -442,6 +442,7 @@ async def get_app_objects(self) -> RunningApp:
             environment_name=self._environment_name,
             tag_to_object_id=tag_to_object_id,
             object_handle_metadata=object_handle_metadata,
+            client=self._client,
         )
 
     async def get_serialized_function(self) -> Tuple[Optional[Any], Optional[Callable[..., Any]]]:
diff --git a/modal/app.py b/modal/app.py
index 057911675..7f3d754fa 100644
--- a/modal/app.py
+++ b/modal/app.py
@@ -124,6 +124,7 @@ def foo():
     """
 
     _all_apps: ClassVar[Dict[Optional[str], List["_App"]]] = {}
+    _container_app: ClassVar[Optional[RunningApp]] = None
 
     _name: Optional[str]
     _description: Optional[str]
@@ -429,6 +430,8 @@ def _init_container(self, client: _Client, running_app: RunningApp):
         self._running_app = running_app
         self._client = client
 
+        _App._container_app = running_app
+
         # Hydrate objects on app
         for tag, object_id in running_app.tag_to_object_id.items():
             if tag in self._indexed_objects:
diff --git a/modal/runner.py b/modal/runner.py
index 23fcf4c89..69ad01d15 100644
--- a/modal/runner.py
+++ b/modal/runner.py
@@ -57,7 +57,7 @@ async def _init_local_app_existing(client: _Client, existing_app_id: str) -> Run
     obj_resp = await retry_transient_errors(client.stub.AppGetObjects, obj_req)
     app_page_url = f"https://modal.com/apps/{existing_app_id}"  # TODO (elias): this should come from the backend
     object_ids = {item.tag: item.object.object_id for item in obj_resp.items}
-    return RunningApp(existing_app_id, app_page_url=app_page_url, tag_to_object_id=object_ids)
+    return RunningApp(existing_app_id, app_page_url=app_page_url, tag_to_object_id=object_ids, client=client)
 
 
 async def _init_local_app_new(
@@ -76,6 +76,7 @@ async def _init_local_app_new(
     logger.debug(f"Created new app with id {app_resp.app_id}")
     return RunningApp(
         app_resp.app_id,
+        client=client,
         app_page_url=app_resp.app_page_url,
         app_logs_url=app_resp.app_logs_url,
         environment_name=environment_name,
diff --git a/modal/running_app.py b/modal/running_app.py
index 22f76d9ed..7bbb46e34 100644
--- a/modal/running_app.py
+++ b/modal/running_app.py
@@ -4,6 +4,8 @@
 
 from google.protobuf.message import Message
 
+from .client import _Client
+
 
 @dataclass
 class RunningApp:
@@ -14,3 +16,4 @@ class RunningApp:
     tag_to_object_id: Dict[str, str] = field(default_factory=dict)
     object_handle_metadata: Dict[str, Optional[Message]] = field(default_factory=dict)
     interactive: bool = False
+    client: Optional[_Client] = None
diff --git a/modal/sandbox.py b/modal/sandbox.py
index 87591b81a..7590463bd 100644
--- a/modal/sandbox.py
+++ b/modal/sandbox.py
@@ -183,6 +183,8 @@ async def create(
         client: Optional[_Client] = None,
         _experimental_gpus: Sequence[GPU_T] = [],
     ) -> "_Sandbox":
+        from .app import _App
+
         if environment_name is None:
             environment_name = config.get("environment")
 
@@ -208,12 +210,19 @@ async def create(
             _experimental_scheduler_placement=_experimental_scheduler_placement,
             _experimental_gpus=_experimental_gpus,
         )
-        if client is None:
-            if app and app._client:
-                client = app._client
-            else:
-                client = await _Client.from_env()
-        app_id: Optional[str] = app.app_id if app else None
+
+        app_id: Optional[str] = None
+        app_client: Optional[_Client] = None
+
+        if app is not None:
+            app_id = app.app_id
+            app_client = app._client
+        elif _App._container_app is not None:
+            app_id = _App._container_app.app_id
+            app_client = _App._container_app.client
+
+        client = client or app_client or await _Client.from_env()
+
         resolver = Resolver(client, environment_name=environment_name, app_id=app_id)
         await resolver.load(obj)
         return obj
diff --git a/test/conftest.py b/test/conftest.py
index cd7e8f4fc..3761fccfe 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -192,6 +192,7 @@ def __init__(self, blob_host, blobs):
         self.volume_reloads: Dict[str, int] = defaultdict(lambda: 0)
 
         self.sandbox_defs = []
+        self.sandbox_app_id = None
         self.sandbox: asyncio.subprocess.Process = None
         self.sandbox_result: Optional[api_pb2.GenericResult] = None
 
@@ -1181,6 +1182,7 @@ async def SandboxCreate(self, stream):
             stdin=asyncio.subprocess.PIPE,
         )
 
+        self.sandbox_app_id = request.app_id
         self.sandbox_defs.append(request.definition)
 
         await stream.send_message(api_pb2.SandboxCreateResponse(sandbox_id="sb-123"))
diff --git a/test/container_test.py b/test/container_test.py
index b0571c2a1..ae905f99e 100644
--- a/test/container_test.py
+++ b/test/container_test.py
@@ -2065,3 +2065,9 @@ def test_max_concurrency(servicer):
 
     outputs = [deserialize(item.result.data, ret.client) for item in ret.items]
     assert n_inputs in outputs
+
+
+@skip_github_non_linux
+def test_sandbox_infers_app(servicer, event_loop):
+    _run_container(servicer, "test.supports.sandbox", "spawn_sandbox")
+    assert servicer.sandbox_app_id == "ap-1"
diff --git a/test/supports/sandbox.py b/test/supports/sandbox.py
new file mode 100644
index 000000000..0318d24d0
--- /dev/null
+++ b/test/supports/sandbox.py
@@ -0,0 +1,9 @@
+# Copyright Modal Labs 2024
+import modal
+
+app = modal.App()
+
+
+@app.function()
+def spawn_sandbox(x):
+    modal.Sandbox.create("bash", "-c", "echo bar")