Code written in PyTorch runs on NVIDIA graphics processing units, not on Google Tensor Processing Units (TPUs), which use JAX. A researcher with the wrong machine may have to rewrite a whole repository to use a published idea.
XStack is a of real repositories on a clean TPU machine. An agent, a program powered by a large language model, gets a working PyTorch repository and must deliver a JAX version that reproduces the original result.
The best agent passed three quarters of the tasks; all others passed at most two fifths. Failures came from unverified code: agents wrote code but did not run it to check against the original. Progress is now measurable, but reliable migration is not solved.
