Well nevermind… this was a small mistake but I’m leaving the post in case it happens to anyone else:
In [17]: class Mod(fx.GraphModule):
    ...:     def __init__(self):
    ...:         super().__init__(self, fx.Graph())
    ...:         def thingy(x):
    ...:             return x* 2.
    ...:         self.graph = fx.symbolic_trace(thingy).graph
    ...:         self.recompile()
    ...: 

In [18]: m = Mod()

In [19]: m(torch.ones(4))
Out[19]: tensor([2., 2., 2., 2.])

It works when I set the self.graph to symbolic_trace(...).graph.
This raises a different question: why doesn’t it throw an error when I try to assign a GraphModule to self.graph?