Remove deprecated steps kwarg from GenerationStrategy (#5142)

ax/adapter/tests/test_model_fit_metrics.py

@@ -44,7 +44,7 @@ def setUp(self) -> None:
             True
         )
         self.generation_strategy = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=NUM_SOBOL,

ax/analysis/graphviz/tests/test_generation_strategy_graph.py

@@ -34,7 +34,7 @@ def setUp(self) -> None:
 
         # Create a simple step-based generation strategy
         self.step_gs = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=5,

ax/benchmark/methods/modular_botorch.py

@@ -97,7 +97,7 @@ def get_sobol_mbm_generation_strategy(
 
     generation_strategy = GenerationStrategy(
         name=name,
-        steps=[
+        nodes=[
             GenerationStep(
                 generator=Generators.SOBOL,
                 num_trials=num_sobol_trials,

ax/benchmark/methods/sobol.py

@@ -17,7 +17,7 @@
 def get_sobol_generation_strategy() -> GenerationStrategy:
     return GenerationStrategy(
         name="Sobol",
-        steps=[
+        nodes=[
             GenerationStep(generator=Generators.SOBOL, num_trials=-1),
         ],
     )

ax/early_stopping/experiment_replay.py

@@ -95,7 +95,7 @@ def replay_experiment(
     # Setup a Orchestrator with a dummy gs to replay the historical experiment
     dummy_sobol_gs = GenerationStrategy(
         name="sobol",
-        steps=[
+        nodes=[
             GenerationStep(generator=Generators.SOBOL, num_trials=-1),
         ],
     )

ax/generation_strategy/dispatch_utils.py

@@ -541,7 +541,7 @@ def choose_generation_strategy_legacy(
         )
     else:  # `force_random_search` is True or we could not suggest BO model
         gs = GenerationStrategy(
-            steps=[
+            nodes=[
                 _make_sobol_step(
                     seed=random_seed,
                     should_deduplicate=should_deduplicate,

ax/generation_strategy/generation_strategy.py

@@ -8,10 +8,10 @@
 
 from __future__ import annotations
 
-import warnings
+from collections.abc import Sequence
 from copy import deepcopy
 from logging import Logger
-from typing import Any, TypeVar
+from typing import TypeVar
 
 from ax.adapter.base import Adapter
 from ax.core.data import Data
@@ -77,27 +77,10 @@ class GenerationStrategy(Base):
     def __init__(
         self,
         *,
-        nodes: list[GenerationNode] | None = None,
+        nodes: Sequence[GenerationNode],
         name: str | None = None,
-        **kwargs: Any,
     ) -> None:
         self._generator_runs = []
-        if not (bool(steps := kwargs.get("steps")) ^ bool(nodes)):  # Steps XOR nodes
-            raise GenerationStrategyMisconfiguredException(
-                "GenerationStrategy must contain either steps or nodes. "
-                f"Got: nodes={nodes}, steps={steps}."
-            )
-
-        if steps:
-            warnings.warn(
-                DeprecationWarning(
-                    "Specifying `steps` input is no longer supported. Please use "
-                    "`nodes`. `steps` argument will be removed in early 2026."
-                ),
-                stacklevel=2,
-            )
-            nodes = steps
-
         self._validate_and_set_node_graph(nodes=nodes)
 
         # Set name to an explicit value ahead of time to avoid
@@ -399,7 +382,6 @@ def _unset_non_persistent_state_fields(self) -> None:
             n._trials_from_node_cache = set()
             n._cached_trial_count = None
 
-    # TODO: Deprecate `steps` argument fully in Q1'26.
     def _validate_and_set_step_sequence(self, steps: list[GenerationNode]) -> None:
         """Initialize and validate the steps provided to this GenerationStrategy.
 

ax/generation_strategy/tests/test_generation_strategy.py

@@ -209,7 +209,7 @@ def test_gen_with_parameter_constraints(self) -> None:
 
         # Create generation strategy with Sobol
         gs = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=10,
@@ -308,7 +308,7 @@ def setUp(self) -> None:
         self.step_generator_kwargs = {"silently_filter_kwargs": True}
         self.hss_experiment = get_hierarchical_search_space_experiment()
         self.sobol_GS = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     Generators.SOBOL,
                     num_trials=-1,
@@ -465,7 +465,7 @@ def _get_sobol_mbm_step_gs(
     ) -> GenerationStrategy:
         return GenerationStrategy(
             name="Sobol+MBM",
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=num_sobol_trials,
@@ -502,7 +502,7 @@ def test_validation(self) -> None:
         # num_trials can be positive or -1.
         with self.assertRaises(UserInputError):
             GenerationStrategy(
-                steps=[
+                nodes=[
                     GenerationStep(generator=Generators.SOBOL, num_trials=5),
                     GenerationStep(
                         generator=Generators.BOTORCH_MODULAR, num_trials=-10
@@ -515,7 +515,7 @@ def test_validation(self) -> None:
         )
         with self.assertRaisesRegex(UserInputError, "Maximum concurrency should be"):
             GenerationStrategy(
-                steps=[
+                nodes=[
                     GenerationStep(
                         generator=Generators.SOBOL, num_trials=5, max_parallelism=-1
                     ),
@@ -527,7 +527,7 @@ def test_custom_callables_for_models(self) -> None:
         with self.assertRaises(UserInputError):
             GenerationStrategy(
                 # pyre-ignore [6]: Testing deprecated input.
-                steps=[GenerationStep(generator=get_sobol, num_trials=-1)]
+                nodes=[GenerationStep(generator=get_sobol, num_trials=-1)]
             )
 
     def test_string_representation(self) -> None:
@@ -548,7 +548,7 @@ def test_string_representation(self) -> None:
             "pausing_criteria=None)])",
         )
         gs2 = GenerationStrategy(
-            steps=[GenerationStep(generator=Generators.SOBOL, num_trials=-1)]
+            nodes=[GenerationStep(generator=Generators.SOBOL, num_trials=-1)]
         )
         self.assertEqual(
             str(gs2),
@@ -601,7 +601,7 @@ def test_min_observed(self) -> None:
         # pyre-fixme[6]: For 1st param expected `bool` but got `Experiment`.
         exp = get_branin_experiment(get_branin_experiment())
         gs = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL, num_trials=5, min_trials_observed=5
                 ),
@@ -619,7 +619,7 @@ def test_one_node_with_finite_num_trials(self) -> None:
         # pyre-fixme[6]: For 1st param expected `bool` but got `Experiment`.
         exp = get_branin_experiment(get_branin_experiment())
         gs = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(generator=Generators.SOBOL, num_trials=5),
             ]
         )
@@ -634,7 +634,7 @@ def test_do_not_enforce_min_observations(self) -> None:
         # case the previous model should be used until there is enough data.
         exp = get_branin_experiment()
         gs = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=1,
@@ -711,7 +711,7 @@ def test_sobol_MBM_strategy_keep_generating(self) -> None:
     def test_sobol_strategy(self) -> None:
         exp = get_branin_experiment()
         sobol_generation_strategy = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=5,
@@ -730,7 +730,7 @@ def test_sobol_strategy(self) -> None:
     def test_factorial_thompson_strategy(self, _: MagicMock) -> None:
         exp = get_branin_experiment()
         factorial_thompson_gs = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.FACTORIAL,
                     num_trials=1,
@@ -761,7 +761,7 @@ def test_factorial_thompson_strategy(self, _: MagicMock) -> None:
 
     def test_clone_reset(self) -> None:
         ftgs = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(generator=Generators.FACTORIAL, num_trials=1),
                 GenerationStep(generator=Generators.THOMPSON, num_trials=2),
             ]
@@ -774,7 +774,7 @@ def test_clone_reset(self) -> None:
 
     def test_kwargs_passed(self) -> None:
         gs = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=1,
@@ -817,7 +817,7 @@ def test_sobol_MBM_strategy_batches(self) -> None:
     def test_store_experiment(self) -> None:
         exp = get_branin_experiment()
         sobol_generation_strategy = GenerationStrategy(
-            steps=[GenerationStep(generator=Generators.SOBOL, num_trials=5)]
+            nodes=[GenerationStep(generator=Generators.SOBOL, num_trials=5)]
         )
         self.assertIsNone(sobol_generation_strategy._experiment)
         sobol_generation_strategy.gen_single_trial(exp)
@@ -828,7 +828,7 @@ def test_gen_single_trial_extracts_pending_observations(self) -> None:
         experiment when none are passed in."""
         exp = get_branin_experiment()
         gs = GenerationStrategy(
-            steps=[GenerationStep(generator=Generators.SOBOL, num_trials=5)]
+            nodes=[GenerationStep(generator=Generators.SOBOL, num_trials=5)]
         )
         # Create a trial and mark it as running so it becomes a pending observation.
         trial = exp.new_trial(generator_run=gs.gen_single_trial(exp))
@@ -856,7 +856,7 @@ def test_gen_single_trial_raises_error_for_multiple_trials(self) -> None:
         """Test that gen_single_trial raises AxError if gen returns multiple trials."""
         exp = get_branin_experiment()
         gs = GenerationStrategy(
-            steps=[GenerationStep(generator=Generators.SOBOL, num_trials=5)]
+            nodes=[GenerationStep(generator=Generators.SOBOL, num_trials=5)]
         )
         gr = gs.gen_single_trial(exp)
         # Mock gen to return multiple trials
@@ -869,7 +869,7 @@ def test_gen_single_trial_raises_error_for_multiple_generator_runs(self) -> None
         GeneratorRuns for a single trial."""
         exp = get_branin_experiment()
         gs = GenerationStrategy(
-            steps=[GenerationStep(generator=Generators.SOBOL, num_trials=5)]
+            nodes=[GenerationStep(generator=Generators.SOBOL, num_trials=5)]
         )
         gr = gs.gen_single_trial(exp)
         # Mock gen to return a single trial with multiple GeneratorRuns
@@ -880,7 +880,7 @@ def test_gen_single_trial_raises_error_for_multiple_generator_runs(self) -> None
     def test_max_parallelism_reached(self) -> None:
         exp = get_branin_experiment()
         sobol_generation_strategy = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL, num_trials=5, max_parallelism=1
                 )
@@ -983,7 +983,7 @@ def test_current_generator_run_limit(self) -> None:
         NUM_ROUNDS = 4
         exp = get_branin_experiment()
         sobol_gs_with_parallelism_limits = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=NUM_INIT_TRIALS,
@@ -1026,7 +1026,7 @@ def test_current_generator_run_limit_unlimited_second_step(self) -> None:
         NUM_ROUNDS = 4
         exp = get_branin_experiment()
         sobol_gs_with_parallelism_limits = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=NUM_INIT_TRIALS,
@@ -1281,7 +1281,7 @@ def test_gen_with_fixed_features(
     ) -> None:
         exp = get_branin_experiment()
         gs = GenerationStrategy(
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=1,
@@ -1377,29 +1377,6 @@ def test_gs_setup_with_nodes(self) -> None:
                     node_3,
                 ],
             )
-        # check error raised if provided both steps and nodes
-        with self.assertRaisesRegex(
-            GenerationStrategyMisconfiguredException, "contain either steps or nodes"
-        ):
-            GenerationStrategy(
-                nodes=[
-                    node_1,
-                    node_3,
-                ],
-                steps=[
-                    GenerationStep(
-                        generator=Generators.SOBOL,
-                        num_trials=5,
-                        generator_kwargs=self.step_generator_kwargs,
-                    ),
-                    GenerationStep(
-                        generator=Generators.BOTORCH_MODULAR,
-                        num_trials=-1,
-                        generator_kwargs=self.step_generator_kwargs,
-                    ),
-                ],
-            )
-
         # check error raised if two transition criterion defining a single edge have
         # differing `continue_trial_generation` settings
         with self.assertRaisesRegex(

ax/generation_strategy/tests/test_transition_criterion.py

@@ -164,7 +164,7 @@ def test_default_step_criterion_setup(self) -> None:
         experiment = get_experiment()
         gs = GenerationStrategy(
             name="SOBOL+MBM::default",
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=3,
@@ -230,7 +230,7 @@ def test_min_trials_is_met(self) -> None:
         experiment = self.branin_experiment
         gs = GenerationStrategy(
             name="SOBOL::default",
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=4,
@@ -312,7 +312,7 @@ def test_min_trials_count_only_with_data(self) -> None:
         experiment = self.branin_experiment
         gs = GenerationStrategy(
             name="SOBOL::default",
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=4,
@@ -508,7 +508,7 @@ def test_trials_from_node_empty(self) -> None:
         experiment = get_experiment()
         gs = GenerationStrategy(
             name="SOBOL::default",
-            steps=[
+            nodes=[
                 GenerationStep(
                     generator=Generators.SOBOL,
                     num_trials=4,