We switched from Hibernate 5 to 6 and observed a strange behaviour:

hibernate 6.1.7
hibernate-jcache 6.1.7
ehcache 3.10.8

Model with a circular reference:
Child(id=c1) -> Parent (id=p1) -> Child(id=c1)

When using an EntityManager to find the Child with id=c1, everything is fine.
Child result = entityManager.find(Child.class, "c1");
The returned result is the same object as the one in result.getParent().getChild().

However, when using a simple query like:
Child result = entityManager.createQuery("SELECT child from Child child WHERE child.objectId = 'c1'", Child.class).getSingleResult();
The returned result is a different Java Object than the one in result.getParent().getChild()

This leads to huge problems.

Please find a testcase here: https://github.com/haarli/hibernate-orm-6
(However, in this test case environment it is not even possible to execute the Query, although it's correct.)

If you set "hibernate.cache.use_second_level_cache" to false, everything works fine

Thank you for any help.