1. Introduction

From version 2 on, BayesFlow is built on Keras3, which allows writing machine learning pipelines that run in JAX, TensorFlow and PyTorch. By using functionality provided by Keras, and extending it with backend-specific code where necessary, we aim to build BayesFlow in a backend-agnostic fashion as well.

As Keras is built upon three different backends, each with different functionality and design decisions, it comes with its own quirks and compromises. The following documents outline some of them, along with the design decisions and programming patterns we use to counter them.