I have a User model that resembles the following:

class User(db.Model):id = db.Column(db.BigInteger, primary_key=True)account_id = db.Column(db.BigInteger, db.ForeignKey('account.id'))account = db.relationship('Account',backref=db.backref('ref_users', cascade='delete'))...def after_user_write(mapper, connection, target):target.account.invalidate_cache()event.listen(User, 'after_insert', after_user_write)
event.listen(User, 'after_update', after_user_write)
event.listen(User, 'after_delete', after_user_write)

Upon insert after_user_write is being called, but target.account is None (which causes an error) when I expect it to be an Account model. target.account_id is set correctly, it just seems like the relationship reference isn't working as I'd expect.

Any ideas on what's causing this?

The relationship doesn't get set by SQLAlchemy automatically when manually creating objects. If you want to access account in the event callback, set it when you create the User instance:

a1 = Account()
u1 = User(account_id=a1.id)
db.session.add(u1)
db.session.commit()assert u1.account is Nonea2 = Account()
# Here: set the account object, instead of the id
u2 = User(account=a2)
db.session.add(u2)
db.session.commit()assert u2.account == a2
assert u2.account_id == a2.id