End-to-End Context Compression at Scale
Authors: name: Ang Li, name: Sean McLeish, name: Haozhe Chen, name: Nimit Kalra, name: Zaiqian Chen, name: Artem Gazizov, name: Venkata Anoop Suhas Kumar Morisetty, name: Bhavya Kailkhura, name: Harshitha Menon, name: Zhuang Liu, name: Brian R. Bartoldson, name: Tom Goldstein, name: Sanae Lotfi, name: Micah Goldblum, name: Pavel Izmailov

Long-context language model inference is bottlenecked by memory, as the KV cache grows with context length. Recent techniques to compress the KV cache fall short: they either degrade model quality substantially or require considerable time and compute to compress a single long prompt. Furthermore, many methods require the input to fit within the target model's context window, and are generally incompatible with modern production inference engines. Encoder-decoder compressors, which map a long token sequence to a shorter sequence of latent embeddings consumed by a decoder, are an appealing alternative in principle. However, existing approaches are not competitive with KV cache compression on the accuracy-efficiency frontier. In this work, we revisit encoder-decoder compression and close this gap. We first perform an architecture search, pre-training many variants from scratch to determine how best to design and train encoder-decoder compressors. Guided by our findings, we continually pre-train a family of 0.6B-encoder, 4B-decoder models on over 350B tokens each, at compression ratios of 1:4, 1:8, and 1:16. We introduce Latent Context Language Models (LCLMs), a family of compressors that improve the Pareto frontier across general-task performance, compression speed, and peak memory usage. We demonstrate that LCLMs serve as efficient backbones for long-horizon agents, letting the agent skim through a compressed long context and adaptively expand relevant segments on demand.