fix: detect circular task context dependencies

lib/crewai/src/crewai/crew.py

@@ -835,6 +835,47 @@ def validate_async_task_cannot_include_sequential_async_tasks_in_context(
                                 break
         return self
 
+    @model_validator(mode="after")
+    def validate_context_no_circular_dependencies(self) -> Self:
+        """Validates that task context dependencies do not contain cycles."""
+        task_ids = {id(task) for task in self.tasks}
+        visiting: set[int] = set()
+        visited: set[int] = set()
+        path: list[Task] = []
+
+        def visit(task: Task) -> None:
+            task_id = id(task)
+            if task_id in visited:
+                return
+            if task_id in visiting:
+                cycle_start = next(
+                    index
+                    for index, path_task in enumerate(path)
+                    if id(path_task) == task_id
+                )
+                cycle_tasks = [*path[cycle_start:], task]
+                cycle_descriptions = " -> ".join(
+                    cycle_task.description for cycle_task in cycle_tasks
+                )
+                raise ValueError(
+                    "Task context dependencies contain a circular dependency: "
+                    f"{cycle_descriptions}."
+                )
+
+            visiting.add(task_id)
+            path.append(task)
+            if isinstance(task.context, list):
+                for context_task in task.context:
+                    if id(context_task) in task_ids:
+                        visit(context_task)
+            path.pop()
+            visiting.remove(task_id)
+            visited.add(task_id)
+
+        for task in self.tasks:
+            visit(task)
+        return self
+
     @model_validator(mode="after")
     def validate_context_no_future_tasks(self) -> Self:
         """Validates that a task's context does not include future tasks."""

lib/crewai/tests/test_crew.py

@@ -253,6 +253,37 @@ def test_context_no_future_tasks(researcher, writer):
         Crew(tasks=[task1, task2, task3, task4], agents=[researcher, writer])
 
 
+def test_context_no_circular_dependencies(researcher, writer):
+    task1 = Task(
+        description="Task 1",
+        expected_output="output",
+        agent=researcher,
+    )
+    task2 = Task(
+        description="Task 2",
+        expected_output="output",
+        agent=researcher,
+    )
+    task3 = Task(
+        description="Task 3",
+        expected_output="output",
+        agent=researcher,
+    )
+
+    task1.context = [task2]
+    task2.context = [task3]
+    task3.context = [task1]
+
+    with pytest.raises(
+        ValueError,
+        match=re.escape(
+            "Task context dependencies contain a circular dependency: "
+            "Task 1 -> Task 2 -> Task 3 -> Task 1."
+        ),
+    ):
+        Crew(tasks=[task1, task2, task3], agents=[researcher, writer])
+
+
 def test_crew_config_with_wrong_keys():
     no_tasks_config = json.dumps(
         {