diff --git a/ax/core/runner.py b/ax/core/runner.py
index 39d71ed99f8..89f2bdbed86 100644
--- a/ax/core/runner.py
+++ b/ax/core/runner.py
@@ -10,7 +10,8 @@
 
 from abc import ABC, abstractmethod
 from collections.abc import Iterable
-from typing import Any, Self, TYPE_CHECKING
+from dataclasses import dataclass
+from typing import Any, ClassVar, Self, TYPE_CHECKING
 
 from ax.utils.common.base import Base
 from ax.utils.common.serialization import SerializationMixin
@@ -21,9 +22,27 @@
     from ax import core  # noqa F401
 
 
+class RunnerConfig:
+    @dataclass(frozen=True)
+    class SearchSpaceUpdateArguments:
+        """Base arguments for search space updates. Override in RunnerConfig
+        subclasses to add runner-specific fields."""
+
+        pass
+
+    @dataclass(frozen=True)
+    class RunnerUpdateArguments:
+        """Base arguments for general runner updates. Override in RunnerConfig
+        subclasses to add runner-specific fields."""
+
+        pass
+
+
 class Runner(Base, SerializationMixin, ABC):
     """Abstract base class for custom runner classes"""
 
+    config_type: ClassVar[type[RunnerConfig]] = RunnerConfig
+
     @property
     def staging_required(self) -> bool:
         """Whether the trial goes to staged or running state once deployed."""
diff --git a/ax/utils/common/sentinel.py b/ax/utils/common/sentinel.py
new file mode 100644
index 00000000000..2b8a7ca3f39
--- /dev/null
+++ b/ax/utils/common/sentinel.py
@@ -0,0 +1,22 @@
+#!/usr/bin/env python3
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+# pyre-strict
+
+
+class Unset:
+    """Sentinel type for distinguishing "not provided" from an explicit ``None``.
+
+    Use the module-level ``UNSET`` instance as the default value for
+    optional fields where ``None`` is a valid, meaningful value and a
+    separate "not set" state is needed.
+    """
+
+    def __repr__(self) -> str:
+        return "UNSET"
+
+
+UNSET: Unset = Unset()