diff --git a/bigframes/_config/bigquery_options.py b/bigframes/_config/bigquery_options.py
index ad79543cb8..0506f1841e 100644
--- a/bigframes/_config/bigquery_options.py
+++ b/bigframes/_config/bigquery_options.py
@@ -16,7 +16,8 @@
 
 from __future__ import annotations
 
-from typing import Optional
+from enum import Enum
+from typing import Literal, Optional
 import warnings
 
 import google.api_core.exceptions
@@ -26,6 +27,12 @@
 import bigframes.constants
 import bigframes.exceptions
 
+
+class OrderingMode(Enum):
+    STRICT = "strict"
+    PARTIAL = "partial"
+
+
 SESSION_STARTED_MESSAGE = (
     "Cannot change '{attribute}' once a session has started. "
     "Call bigframes.pandas.close_session() first, if you are using the bigframes.pandas API."
@@ -57,6 +64,14 @@ def _validate_location(value: Optional[str]):
         )
 
 
+def _validate_ordering_mode(value: str) -> OrderingMode:
+    if value.casefold() == OrderingMode.STRICT.value.casefold():
+        return OrderingMode.STRICT
+    if value.casefold() == OrderingMode.PARTIAL.value.casefold():
+        return OrderingMode.PARTIAL
+    raise ValueError("Ordering mode must be one of 'strict' or 'partial'.")
+
+
 class BigQueryOptions:
     """Encapsulates configuration for working with a session."""
 
@@ -71,7 +86,7 @@ def __init__(
         kms_key_name: Optional[str] = None,
         skip_bq_connection_check: bool = False,
         *,
-        _strictly_ordered: bool = True,
+        ordering_mode: Literal["strict", "partial"] = "strict",
     ):
         self._credentials = credentials
         self._project = project
@@ -82,8 +97,8 @@ def __init__(
         self._kms_key_name = kms_key_name
         self._skip_bq_connection_check = skip_bq_connection_check
         self._session_started = False
-        # Determines the ordering strictness for the session. For internal use only.
-        self._strictly_ordered_internal = _strictly_ordered
+        # Determines the ordering strictness for the session.
+        self._ordering_mode = _validate_ordering_mode(ordering_mode)
 
     @property
     def application_name(self) -> Optional[str]:
@@ -241,6 +256,10 @@ def kms_key_name(self, value: str):
         self._kms_key_name = value
 
     @property
-    def _strictly_ordered(self) -> bool:
-        """Internal use only. Controls whether total row order is always maintained for DataFrame/Series."""
-        return self._strictly_ordered_internal
+    def ordering_mode(self) -> Literal["strict", "partial"]:
+        """Controls whether total row order is always maintained for DataFrame/Series."""
+        return self._ordering_mode.value
+
+    @ordering_mode.setter
+    def ordering_mode(self, ordering_mode: Literal["strict", "partial"]) -> None:
+        self._ordering_mode = _validate_ordering_mode(ordering_mode)
diff --git a/bigframes/session/__init__.py b/bigframes/session/__init__.py
index 9c953ee594..22ca63d25b 100644
--- a/bigframes/session/__init__.py
+++ b/bigframes/session/__init__.py
@@ -297,15 +297,21 @@ def __init__(
         self._execution_count = 0
         # Whether this session treats objects as totally ordered.
         # Will expose as feature later, only False for internal testing
-        self._strictly_ordered: bool = context._strictly_ordered
+        self._strictly_ordered: bool = context.ordering_mode != "partial"
+        if not self._strictly_ordered:
+            warnings.warn(
+                "Partial ordering mode is a preview feature and is subject to change.",
+                bigframes.exceptions.PreviewWarning,
+            )
+
         # Sequential index needs total ordering to generate, so use null index with unstrict ordering.
         self._default_index_type: bigframes.enums.DefaultIndexKind = (
             bigframes.enums.DefaultIndexKind.SEQUENTIAL_INT64
-            if context._strictly_ordered
+            if self._strictly_ordered
             else bigframes.enums.DefaultIndexKind.NULL
         )
         self._compiler = bigframes.core.compile.SQLCompiler(
-            strict=context._strictly_ordered
+            strict=self._strictly_ordered
         )
 
         self._remote_function_session = bigframes_rf._RemoteFunctionSession()
diff --git a/tests/system/conftest.py b/tests/system/conftest.py
index 59439c306f..55079380f4 100644
--- a/tests/system/conftest.py
+++ b/tests/system/conftest.py
@@ -141,9 +141,7 @@ def session() -> Generator[bigframes.Session, None, None]:
 
 @pytest.fixture(scope="session", params=["ordered", "unordered"])
 def maybe_ordered_session(request) -> Generator[bigframes.Session, None, None]:
-    context = bigframes.BigQueryOptions(
-        location="US", _strictly_ordered=request.param == "ordered"
-    )
+    context = bigframes.BigQueryOptions(location="US", ordering_mode="partial")
     session = bigframes.Session(context=context)
     yield session
     session.close()  # close generated session at cleanup type
@@ -151,7 +149,7 @@ def maybe_ordered_session(request) -> Generator[bigframes.Session, None, None]:
 
 @pytest.fixture(scope="session")
 def unordered_session() -> Generator[bigframes.Session, None, None]:
-    context = bigframes.BigQueryOptions(location="US", _strictly_ordered=False)
+    context = bigframes.BigQueryOptions(location="US", ordering_mode="partial")
     session = bigframes.Session(context=context)
     yield session
     session.close()  # close generated session at cleanup type