fix: preserve nested condition structure in Flow decorators

Fixes nested boolean conditions being flattened in @listen, @start, and @router decorators. The or_() and and_() combinators now preserve their nested structure using a "conditions" key instead of flattening to a list. Added recursive evaluation logic to properly handle complex patterns like or_(and_(A, B), and_(C, D)).

src/crewai/flow/flow.py

@@ -31,7 +31,7 @@ from crewai.flow.flow_visualizer import plot_flow
 from crewai.flow.persistence.base import FlowPersistence
 from crewai.flow.types import FlowExecutionData
 from crewai.flow.utils import get_possible_return_constants
-from crewai.utilities.printer import Printer
+from crewai.utilities.printer import Printer, PrinterColor
 
 logger = logging.getLogger(__name__)
 
@@ -105,7 +105,7 @@ def start(condition: str | dict | Callable | None = None) -> Callable:
     condition : Optional[Union[str, dict, Callable]], optional
         Defines when the start method should execute. Can be:
         - str: Name of a method that triggers this start
-        - dict: Contains "type" ("AND"/"OR") and "methods" (list of triggers)
+        - dict: Result from or_() or and_(), including nested conditions
         - Callable: A method reference that triggers this start
         Default is None, meaning unconditional start.
 
@@ -140,13 +140,18 @@ def start(condition: str | dict | Callable | None = None) -> Callable:
             if isinstance(condition, str):
                 func.__trigger_methods__ = [condition]
                 func.__condition_type__ = "OR"
-            elif (
+            elif isinstance(condition, dict) and "type" in condition:
-                isinstance(condition, dict)
+                if "conditions" in condition:
-                and "type" in condition
+                    func.__trigger_condition__ = condition
-                and "methods" in condition
+                    func.__trigger_methods__ = _extract_all_methods(condition)
-            ):
+                    func.__condition_type__ = condition["type"]
-                func.__trigger_methods__ = condition["methods"]
+                elif "methods" in condition:
-                func.__condition_type__ = condition["type"]
+                    func.__trigger_methods__ = condition["methods"]
+                    func.__condition_type__ = condition["type"]
+                else:
+                    raise ValueError(
+                        "Condition dict must contain 'conditions' or 'methods'"
+                    )
             elif callable(condition) and hasattr(condition, "__name__"):
                 func.__trigger_methods__ = [condition.__name__]
                 func.__condition_type__ = "OR"
@@ -172,7 +177,7 @@ def listen(condition: str | dict | Callable) -> Callable:
     condition : Union[str, dict, Callable]
         Specifies when the listener should execute. Can be:
         - str: Name of a method that triggers this listener
-        - dict: Contains "type" ("AND"/"OR") and "methods" (list of triggers)
+        - dict: Result from or_() or and_(), including nested conditions
         - Callable: A method reference that triggers this listener
 
     Returns
@@ -200,13 +205,18 @@ def listen(condition: str | dict | Callable) -> Callable:
         if isinstance(condition, str):
             func.__trigger_methods__ = [condition]
             func.__condition_type__ = "OR"
-        elif (
+        elif isinstance(condition, dict) and "type" in condition:
-            isinstance(condition, dict)
+            if "conditions" in condition:
-            and "type" in condition
+                func.__trigger_condition__ = condition
-            and "methods" in condition
+                func.__trigger_methods__ = _extract_all_methods(condition)
-        ):
+                func.__condition_type__ = condition["type"]
-            func.__trigger_methods__ = condition["methods"]
+            elif "methods" in condition:
-            func.__condition_type__ = condition["type"]
+                func.__trigger_methods__ = condition["methods"]
+                func.__condition_type__ = condition["type"]
+            else:
+                raise ValueError(
+                    "Condition dict must contain 'conditions' or 'methods'"
+                )
         elif callable(condition) and hasattr(condition, "__name__"):
             func.__trigger_methods__ = [condition.__name__]
             func.__condition_type__ = "OR"
@@ -233,7 +243,7 @@ def router(condition: str | dict | Callable) -> Callable:
     condition : Union[str, dict, Callable]
         Specifies when the router should execute. Can be:
         - str: Name of a method that triggers this router
-        - dict: Contains "type" ("AND"/"OR") and "methods" (list of triggers)
+        - dict: Result from or_() or and_(), including nested conditions
         - Callable: A method reference that triggers this router
 
     Returns
@@ -266,13 +276,18 @@ def router(condition: str | dict | Callable) -> Callable:
         if isinstance(condition, str):
             func.__trigger_methods__ = [condition]
             func.__condition_type__ = "OR"
-        elif (
+        elif isinstance(condition, dict) and "type" in condition:
-            isinstance(condition, dict)
+            if "conditions" in condition:
-            and "type" in condition
+                func.__trigger_condition__ = condition
-            and "methods" in condition
+                func.__trigger_methods__ = _extract_all_methods(condition)
-        ):
+                func.__condition_type__ = condition["type"]
-            func.__trigger_methods__ = condition["methods"]
+            elif "methods" in condition:
-            func.__condition_type__ = condition["type"]
+                func.__trigger_methods__ = condition["methods"]
+                func.__condition_type__ = condition["type"]
+            else:
+                raise ValueError(
+                    "Condition dict must contain 'conditions' or 'methods'"
+                )
         elif callable(condition) and hasattr(condition, "__name__"):
             func.__trigger_methods__ = [condition.__name__]
             func.__condition_type__ = "OR"
@@ -298,14 +313,15 @@ def or_(*conditions: str | dict | Callable) -> dict:
     *conditions : Union[str, dict, Callable]
         Variable number of conditions that can be:
         - str: Method names
-        - dict: Existing condition dictionaries
+        - dict: Existing condition dictionaries (nested conditions)
         - Callable: Method references
 
     Returns
     -------
     dict
         A condition dictionary with format:
-        {"type": "OR", "methods": list_of_method_names}
+        {"type": "OR", "conditions": list_of_conditions}
+        where each condition can be a string (method name) or a nested dict
 
     Raises
     ------
@@ -317,18 +333,22 @@ def or_(*conditions: str | dict | Callable) -> dict:
     >>> @listen(or_("success", "timeout"))
     >>> def handle_completion(self):
     ...     pass
+
+    >>> @listen(or_(and_("step1", "step2"), "step3"))
+    >>> def handle_nested(self):
+    ...     pass
     """
-    methods = []
+    processed_conditions: list[str | dict[str, Any]] = []
     for condition in conditions:
-        if isinstance(condition, dict) and "methods" in condition:
+        if isinstance(condition, dict):
-            methods.extend(condition["methods"])
+            processed_conditions.append(condition)
         elif isinstance(condition, str):
-            methods.append(condition)
+            processed_conditions.append(condition)
         elif callable(condition):
-            methods.append(getattr(condition, "__name__", repr(condition)))
+            processed_conditions.append(getattr(condition, "__name__", repr(condition)))
         else:
             raise ValueError("Invalid condition in or_()")
-    return {"type": "OR", "methods": methods}
+    return {"type": "OR", "conditions": processed_conditions}
 
 
 def and_(*conditions: str | dict | Callable) -> dict:
@@ -344,14 +364,15 @@ def and_(*conditions: str | dict | Callable) -> dict:
     *conditions : Union[str, dict, Callable]
         Variable number of conditions that can be:
         - str: Method names
-        - dict: Existing condition dictionaries
+        - dict: Existing condition dictionaries (nested conditions)
         - Callable: Method references
 
     Returns
     -------
     dict
         A condition dictionary with format:
-        {"type": "AND", "methods": list_of_method_names}
+        {"type": "AND", "conditions": list_of_conditions}
+        where each condition can be a string (method name) or a nested dict
 
     Raises
     ------
@@ -363,18 +384,69 @@ def and_(*conditions: str | dict | Callable) -> dict:
     >>> @listen(and_("validated", "processed"))
     >>> def handle_complete_data(self):
     ...     pass
+
+    >>> @listen(and_(or_("step1", "step2"), "step3"))
+    >>> def handle_nested(self):
+    ...     pass
     """
-    methods = []
+    processed_conditions: list[str | dict[str, Any]] = []
     for condition in conditions:
-        if isinstance(condition, dict) and "methods" in condition:
+        if isinstance(condition, dict):
-            methods.extend(condition["methods"])
+            processed_conditions.append(condition)
         elif isinstance(condition, str):
-            methods.append(condition)
+            processed_conditions.append(condition)
         elif callable(condition):
-            methods.append(getattr(condition, "__name__", repr(condition)))
+            processed_conditions.append(getattr(condition, "__name__", repr(condition)))
         else:
             raise ValueError("Invalid condition in and_()")
-    return {"type": "AND", "methods": methods}
+    return {"type": "AND", "conditions": processed_conditions}
+
+
+def _normalize_condition(condition: str | dict | list) -> dict:
+    """Normalize a condition to standard format with 'conditions' key.
+
+    Args:
+        condition: Can be a string (method name), dict (condition), or list
+
+    Returns:
+        Normalized dict with 'type' and 'conditions' keys
+    """
+    if isinstance(condition, str):
+        return {"type": "OR", "conditions": [condition]}
+    if isinstance(condition, dict):
+        if "conditions" in condition:
+            return condition
+        if "methods" in condition:
+            return {"type": condition["type"], "conditions": condition["methods"]}
+        return condition
+    if isinstance(condition, list):
+        return {"type": "OR", "conditions": condition}
+    return {"type": "OR", "conditions": [condition]}
+
+
+def _extract_all_methods(condition: str | dict | list) -> list[str]:
+    """Extract all method names from a condition (including nested).
+
+    Args:
+        condition: Can be a string, dict, or list
+
+    Returns:
+        List of all method names in the condition tree
+    """
+    if isinstance(condition, str):
+        return [condition]
+    if isinstance(condition, dict):
+        normalized = _normalize_condition(condition)
+        methods = []
+        for sub_cond in normalized.get("conditions", []):
+            methods.extend(_extract_all_methods(sub_cond))
+        return methods
+    if isinstance(condition, list):
+        methods = []
+        for item in condition:
+            methods.extend(_extract_all_methods(item))
+        return methods
+    return []
 
 
 class FlowMeta(type):
@@ -402,7 +474,10 @@ class FlowMeta(type):
                 if hasattr(attr_value, "__trigger_methods__"):
                     methods = attr_value.__trigger_methods__
                     condition_type = getattr(attr_value, "__condition_type__", "OR")
-                    listeners[attr_name] = (condition_type, methods)
+                    if hasattr(attr_value, "__trigger_condition__"):
+                        listeners[attr_name] = attr_value.__trigger_condition__
+                    else:
+                        listeners[attr_name] = (condition_type, methods)
 
                     if (
                         hasattr(attr_value, "__is_router__")
@@ -822,6 +897,7 @@ class Flow(Generic[T], metaclass=FlowMeta):
                 # Clear completed methods and outputs for a fresh start
                 self._completed_methods.clear()
                 self._method_outputs.clear()
+                self._pending_and_listeners.clear()
             else:
                 # We're restoring from persistence, set the flag
                 self._is_execution_resuming = True
@@ -1086,10 +1162,16 @@ class Flow(Generic[T], metaclass=FlowMeta):
                     for method_name in self._start_methods:
                         # Check if this start method is triggered by the current trigger
                         if method_name in self._listeners:
-                            condition_type, trigger_methods = self._listeners[
+                            condition_data = self._listeners[method_name]
-                                method_name
+                            should_trigger = False
-                            ]
+                            if isinstance(condition_data, tuple):
-                            if current_trigger in trigger_methods:
+                                _, trigger_methods = condition_data
+                                should_trigger = current_trigger in trigger_methods
+                            elif isinstance(condition_data, dict):
+                                all_methods = _extract_all_methods(condition_data)
+                                should_trigger = current_trigger in all_methods
+
+                            if should_trigger:
                                 # Only execute if this is a cycle (method was already completed)
                                 if method_name in self._completed_methods:
                                     # For router-triggered start methods in cycles, temporarily clear resumption flag
@@ -1099,6 +1181,51 @@ class Flow(Generic[T], metaclass=FlowMeta):
                                     await self._execute_start_method(method_name)
                                     self._is_execution_resuming = was_resuming
 
+    def _evaluate_condition(
+        self, condition: str | dict, trigger_method: str, listener_name: str
+    ) -> bool:
+        """Recursively evaluate a condition (simple or nested).
+
+        Args:
+            condition: Can be a string (method name) or dict (nested condition)
+            trigger_method: The method that just completed
+            listener_name: Name of the listener being evaluated
+
+        Returns:
+            True if the condition is satisfied, False otherwise
+        """
+        if isinstance(condition, str):
+            return condition == trigger_method
+
+        if isinstance(condition, dict):
+            normalized = _normalize_condition(condition)
+            cond_type = normalized.get("type", "OR")
+            sub_conditions = normalized.get("conditions", [])
+
+            if cond_type == "OR":
+                return any(
+                    self._evaluate_condition(sub_cond, trigger_method, listener_name)
+                    for sub_cond in sub_conditions
+                )
+
+            if cond_type == "AND":
+                pending_key = f"{listener_name}:{id(condition)}"
+
+                if pending_key not in self._pending_and_listeners:
+                    all_methods = set(_extract_all_methods(condition))
+                    self._pending_and_listeners[pending_key] = all_methods
+
+                if trigger_method in self._pending_and_listeners[pending_key]:
+                    self._pending_and_listeners[pending_key].discard(trigger_method)
+
+                if not self._pending_and_listeners[pending_key]:
+                    self._pending_and_listeners.pop(pending_key, None)
+                    return True
+
+                return False
+
+        return False
+
     def _find_triggered_methods(
         self, trigger_method: str, router_only: bool
     ) -> list[str]:
@@ -1106,7 +1233,7 @@ class Flow(Generic[T], metaclass=FlowMeta):
         Finds all methods that should be triggered based on conditions.
 
         This internal method evaluates both OR and AND conditions to determine
-        which methods should be executed next in the flow.
+        which methods should be executed next in the flow. Supports nested conditions.
 
         Parameters
         ----------
@@ -1123,14 +1250,13 @@ class Flow(Generic[T], metaclass=FlowMeta):
 
         Notes
         -----
-        - Handles both OR and AND conditions:
+        - Handles both OR and AND conditions, including nested combinations
-          * OR: Triggers if any condition is met
-          * AND: Triggers only when all conditions are met
         - Maintains state for AND conditions using _pending_and_listeners
         - Separates router and normal listener evaluation
         """
         triggered = []
-        for listener_name, (condition_type, methods) in self._listeners.items():
+
+        for listener_name, condition_data in self._listeners.items():
             is_router = listener_name in self._routers
 
             if router_only != is_router:
@@ -1139,23 +1265,29 @@ class Flow(Generic[T], metaclass=FlowMeta):
             if not router_only and listener_name in self._start_methods:
                 continue
 
-            if condition_type == "OR":
+            if isinstance(condition_data, tuple):
-                # If the trigger_method matches any in methods, run this
+                condition_type, methods = condition_data
-                if trigger_method in methods:
-                    triggered.append(listener_name)
-            elif condition_type == "AND":
-                # Initialize pending methods for this listener if not already done
-                if listener_name not in self._pending_and_listeners:
-                    self._pending_and_listeners[listener_name] = set(methods)
-                # Remove the trigger method from pending methods
-                if trigger_method in self._pending_and_listeners[listener_name]:
-                    self._pending_and_listeners[listener_name].discard(trigger_method)
 
-                if not self._pending_and_listeners[listener_name]:
+                if condition_type == "OR":
-                    # All required methods have been executed
+                    if trigger_method in methods:
+                        triggered.append(listener_name)
+                elif condition_type == "AND":
+                    if listener_name not in self._pending_and_listeners:
+                        self._pending_and_listeners[listener_name] = set(methods)
+                    if trigger_method in self._pending_and_listeners[listener_name]:
+                        self._pending_and_listeners[listener_name].discard(
+                            trigger_method
+                        )
+
+                    if not self._pending_and_listeners[listener_name]:
+                        triggered.append(listener_name)
+                        self._pending_and_listeners.pop(listener_name, None)
+
+            elif isinstance(condition_data, dict):
+                if self._evaluate_condition(
+                    condition_data, trigger_method, listener_name
+                ):
                     triggered.append(listener_name)
-                    # Reset pending methods for this listener
-                    self._pending_and_listeners.pop(listener_name, None)
 
         return triggered
 
@@ -1218,7 +1350,7 @@ class Flow(Generic[T], metaclass=FlowMeta):
             raise
 
     def _log_flow_event(
-        self, message: str, color: str = "yellow", level: str = "info"
+        self, message: str, color: PrinterColor | None = "yellow", level: str = "info"
     ) -> None:
         """Centralized logging method for flow events.
 

tests/test_flow.py

@@ -6,15 +6,15 @@ from datetime import datetime
 import pytest
 from pydantic import BaseModel
 
-from crewai.flow.flow import Flow, and_, listen, or_, router, start
 from crewai.events.event_bus import crewai_event_bus
 from crewai.events.types.flow_events import (
     FlowFinishedEvent,
-    FlowStartedEvent,
     FlowPlotEvent,
+    FlowStartedEvent,
     MethodExecutionFinishedEvent,
     MethodExecutionStartedEvent,
 )
+from crewai.flow.flow import Flow, and_, listen, or_, router, start
 
 
 def test_simple_sequential_flow():
@@ -679,11 +679,11 @@ def test_structured_flow_event_emission():
     assert isinstance(received_events[3], MethodExecutionStartedEvent)
     assert received_events[3].method_name == "send_welcome_message"
     assert received_events[3].params == {}
-    assert getattr(received_events[3].state, "sent") is False
+    assert received_events[3].state.sent is False
 
     assert isinstance(received_events[4], MethodExecutionFinishedEvent)
     assert received_events[4].method_name == "send_welcome_message"
-    assert getattr(received_events[4].state, "sent") is True
+    assert received_events[4].state.sent is True
     assert received_events[4].result == "Welcome, Anakin!"
 
     assert isinstance(received_events[5], FlowFinishedEvent)
@@ -894,3 +894,75 @@ def test_flow_name():
 
     flow = MyFlow()
     assert flow.name == "MyFlow"
+
+
+def test_nested_and_or_conditions():
+    """Test nested conditions like or_(and_(A, B), and_(C, D)).
+
+    Reproduces bug from issue #3719 where nested conditions are flattened,
+    causing premature execution.
+    """
+    execution_order = []
+
+    class NestedConditionFlow(Flow):
+        @start()
+        def method_1(self):
+            execution_order.append("method_1")
+
+        @listen(method_1)
+        def method_2(self):
+            execution_order.append("method_2")
+
+        @router(method_2)
+        def method_3(self):
+            execution_order.append("method_3")
+            # Choose b_condition path
+            return "b_condition"
+
+        @listen("b_condition")
+        def method_5(self):
+            execution_order.append("method_5")
+
+        @listen(method_5)
+        async def method_4(self):
+            execution_order.append("method_4")
+
+        @listen(or_("a_condition", "b_condition"))
+        async def method_6(self):
+            execution_order.append("method_6")
+
+        @listen(
+            or_(
+                and_("a_condition", method_6),
+                and_(method_6, method_4),
+            )
+        )
+        def method_7(self):
+            execution_order.append("method_7")
+
+        @listen(method_7)
+        async def method_8(self):
+            execution_order.append("method_8")
+
+    flow = NestedConditionFlow()
+    flow.kickoff()
+
+    # Verify execution happened
+    assert "method_1" in execution_order
+    assert "method_2" in execution_order
+    assert "method_3" in execution_order
+    assert "method_5" in execution_order
+    assert "method_4" in execution_order
+    assert "method_6" in execution_order
+    assert "method_7" in execution_order
+    assert "method_8" in execution_order
+
+    # Critical assertion: method_7 should only execute AFTER both method_6 AND method_4
+    # Since b_condition was returned, method_6 triggers on b_condition
+    # method_7 requires: (a_condition AND method_6) OR (method_6 AND method_4)
+    # The second condition (method_6 AND method_4) should be the one that triggers
+    assert execution_order.index("method_7") > execution_order.index("method_6")
+    assert execution_order.index("method_7") > execution_order.index("method_4")
+
+    # method_8 should execute after method_7
+    assert execution_order.index("method_8") > execution_order.index("method_7")