Compressing History into Memory: Distilling Transformers into Recurrent Transformers

Transformers are AI's workhorse but their computational cost becomes prohibitive when processing long sequences. We target long-horizon streaming vision and robotics applications, where it is particularly impractical to store and maintain a history of observations. Recurrent Transformers address this limitation by maintaining fixed-size memory but their performance lags behind that of transformers operating over the full observation history. We argue that this gap does not stem from architectural limitations, but from differences in how these models learn to compress past information. Without access to an observation history, recurrent models must explicitly decide what to retain in memory at each step, a significantly harder learning problem. In this work, we propose a distillation approach that transfers the compression strategy of a classical full-history transformer to a recurrent variant. We enable this by designing a teacher model that explicitly compresses its observation history into a fixed-size bottleneck representation and directly supervise the student's memory with this bottleneck representation, effectively aligning the two compression mechanisms. We show that this approach allows to train a recurrent latent robotic memory with linear-time complexity on the Mem-RPE task while substantially narrowing the performance gap to full-history transformers. We additionally validate the same principle on streaming visual question answering (VQA) and observe improved recurrent predictions thanks to memory distillation.