Support baseline-only execution in Scenario

pyrit/scenario/core/scenario.py

@@ -13,7 +13,7 @@
 import textwrap
 import uuid
 from abc import ABC, abstractmethod
-from typing import Dict, List, Optional, Sequence, Set, Type, Union
+from typing import TYPE_CHECKING, Dict, List, Optional, Sequence, Set, Tuple, Type, Union
 
 from tqdm.auto import tqdm
 
@@ -32,6 +32,10 @@
 )
 from pyrit.score import Scorer
 
+if TYPE_CHECKING:
+    from pyrit.executor.attack.core.attack_config import AttackScoringConfig
+    from pyrit.models import SeedAttackGroup
+
 logger = logging.getLogger(__name__)
 
 
@@ -228,14 +232,16 @@ async def initialize_async(
         self._memory_labels = memory_labels or {}
 
         # Prepare scenario strategies using the stored configuration
+        # Allow empty strategies when include_baseline is True (baseline-only execution)
         self._scenario_composites = self._strategy_class.prepare_scenario_strategies(
-            scenario_strategies, default_aggregate=self.get_default_strategy()
+            scenario_strategies,
+            default_aggregate=self.get_default_strategy(),
         )
 
         self._atomic_attacks = await self._get_atomic_attacks_async()
 
         if self._include_baseline:
-            baseline_attack = self._get_baseline_from_first_attack()
+            baseline_attack = self._get_baseline()
             self._atomic_attacks.insert(0, baseline_attack)
 
         # Store original objectives for each atomic attack (before any mutations during execution)
@@ -281,34 +287,21 @@ async def initialize_async(
         self._scenario_result_id = str(result.id)
         logger.info(f"Created new scenario result with ID: {self._scenario_result_id}")
 
-    def _get_baseline_from_first_attack(self) -> AtomicAttack:
+    def _get_baseline(self) -> AtomicAttack:
         """
         Get a baseline AtomicAttack, which simply sends all the objectives without any modifications.
 
+        If other atomic attacks exist, derives baseline data from the first attack.
+        Otherwise, creates a standalone baseline from the dataset configuration and scenario settings.
+
         Returns:
             AtomicAttack: The baseline AtomicAttack instance.
 
         Raises:
-            ValueError: If no atomic attacks are available to derive baseline from.
+            ValueError: If required data (seed_groups, objective_target, attack_scoring_config)
+                       is not available.
         """
-        if not self._atomic_attacks or len(self._atomic_attacks) == 0:
-            raise ValueError("No atomic attacks available to derive baseline from.")
-
-        first_attack = self._atomic_attacks[0]
-
-        # Copy seed_groups, scoring, target from the first attack
-        seed_groups = first_attack.seed_groups
-        attack_scoring_config = first_attack._attack.get_attack_scoring_config()
-        objective_target = first_attack._attack.get_objective_target()
-
-        if not seed_groups or len(seed_groups) == 0:
-            raise ValueError("First atomic attack must have seed_groups to create baseline.")
-
-        if not objective_target:
-            raise ValueError("Objective target is required to create baseline attack.")
-
-        if not attack_scoring_config:
-            raise ValueError("Attack scoring config is required to create baseline attack.")
+        seed_groups, attack_scoring_config, objective_target = self._get_baseline_data()
 
         # Create baseline attack with no converters
         attack = PromptSendingAttack(
@@ -323,6 +316,55 @@ def _get_baseline_from_first_attack(self) -> AtomicAttack:
             memory_labels=self._memory_labels,
         )
 
+    def _get_baseline_data(self) -> Tuple[List["SeedAttackGroup"], "AttackScoringConfig", PromptTarget]:
+        """
+        Get the data needed to create a baseline attack.
+
+        Returns either the first attack's data or the scenario-level data
+        depending on whether other atomic attacks exist.
+
+        Returns:
+            Tuple containing (seed_groups, attack_scoring_config, objective_target)
+
+        Raises:
+            ValueError: If required data is not available.
+        """
+        if self._atomic_attacks and len(self._atomic_attacks) > 0:
+            # Derive from first attack
+            first_attack = self._atomic_attacks[0]
+            seed_groups = first_attack.seed_groups
+            attack_scoring_config = first_attack._attack.get_attack_scoring_config()
+            objective_target = first_attack._attack.get_objective_target()
+        else:
+            # Create from scenario-level settings
+            if not self._objective_target:
+                raise ValueError("Objective target is required to create baseline attack.")
+            if not self._dataset_config:
+                raise ValueError("Dataset config is required to create baseline attack.")
+            if not self._objective_scorer:
+                raise ValueError("Objective scorer is required to create baseline attack.")
+
+            seed_groups = self._dataset_config.get_all_seed_attack_groups()
+            objective_target = self._objective_target
+
+            # Import here to avoid circular imports
+            from typing import cast
+
+            from pyrit.executor.attack.core.attack_config import AttackScoringConfig
+            from pyrit.score import TrueFalseScorer
+
+            attack_scoring_config = AttackScoringConfig(objective_scorer=cast(TrueFalseScorer, self._objective_scorer))
+
+        # Validate required data
+        if not seed_groups or len(seed_groups) == 0:
+            raise ValueError("Seed groups are required to create baseline attack.")
+        if not objective_target:
+            raise ValueError("Objective target is required to create baseline attack.")
+        if not attack_scoring_config:
+            raise ValueError("Attack scoring config is required to create baseline attack.")
+
+        return seed_groups, attack_scoring_config, objective_target
+
     def _raise_dataset_exception(self) -> None:
         error_msg = textwrap.dedent(
             f"""
@@ -650,7 +692,8 @@ async def _execute_scenario_async(self) -> ScenarioResult:
 
                 try:
                     atomic_results = await atomic_attack.run_async(
-                        max_concurrency=self._max_concurrency, return_partial_on_failure=True
+                        max_concurrency=self._max_concurrency,
+                        return_partial_on_failure=True,
                     )
 
                     # Always save completed results, even if some objectives didn't complete
@@ -677,7 +720,8 @@ async def _execute_scenario_async(self) -> ScenarioResult:
 
                         # Mark scenario as failed
                         self._memory.update_scenario_run_state(
-                            scenario_result_id=scenario_result_id, scenario_run_state="FAILED"
+                            scenario_result_id=scenario_result_id,
+                            scenario_run_state="FAILED",
                         )
 
                         # Raise exception with detailed information
@@ -703,7 +747,8 @@ async def _execute_scenario_async(self) -> ScenarioResult:
                     scenario_results = self._memory.get_scenario_results(scenario_result_ids=[scenario_result_id])
                     if scenario_results and scenario_results[0].scenario_run_state != "FAILED":
                         self._memory.update_scenario_run_state(
-                            scenario_result_id=scenario_result_id, scenario_run_state="FAILED"
+                            scenario_result_id=scenario_result_id,
+                            scenario_run_state="FAILED",
                         )
 
                     raise

pyrit/scenario/core/scenario_strategy.py

@@ -213,12 +213,14 @@ def prepare_scenario_strategies(
             strategies (Sequence[T | ScenarioCompositeStrategy] | None): The strategies to prepare.
                 Can be a mix of bare strategy enums and composite strategies.
                 If None, uses default_aggregate to determine defaults.
+                If an empty sequence, returns an empty list (useful for baseline-only execution).
             default_aggregate (T | None): The aggregate strategy to use when strategies is None.
                 Common values: MyStrategy.ALL, MyStrategy.EASY. If None when strategies is None,
                 raises ValueError.
 
         Returns:
             List[ScenarioCompositeStrategy]: Normalized list of composite strategies ready for use.
+                May be empty if an empty sequence was explicitly provided.
 
         Raises:
             ValueError: If strategies is None and default_aggregate is None, or if compositions
@@ -251,7 +253,10 @@ def prepare_scenario_strategies(
                     # For now, skip to allow flexibility
                     pass
 
+        # Allow empty list if explicitly provided (for baseline-only execution)
         if not composite_strategies:
+            if strategies is not None and len(strategies) == 0:
+                return []
             raise ValueError(
                 f"No valid {cls.__name__} strategies provided. "
                 f"Provide at least one {cls.__name__} enum or ScenarioCompositeStrategy."