Any schema that has a circular reference causes the response to pass every time. The circular reference is not in the required list so it is a valid schema. Even if the schema has a circular reference in the required list, the response validation should fail on the missing reference at some level.
Any schema that has a circular reference causes the response to pass every time. The circular reference is not in the required list so it is a valid schema. Even if the schema has a circular reference in the required list, the response validation should fail on the missing reference at some level.
There is an example of recursive references in this OAI/OpenAPI-Specification issue https://github.com/OAI/OpenAPI-Specification/issues/822.