Cartridges: Lightweight and general-purpose long context representations
  via self-study
Authors: name: Sabri Eyuboglu; name: Ryan Ehrlich; name: Simran Arora; name: Neel Guha; name: Dylan Zinsley; name: Emily Liu; name: Will Tennien; name: Atri Rudra; name: James Zou; name: Azalia Mirhoseini; name: Christopher Re
Published: 2025-06-06 17:48:23

Abstract: Large language models are often used to answer queries grounded in large text
corpora (e.g. codebases, legal documents, or chat histories) by placing the
entire corpus in the context window and leveraging in-context learning (ICL).
Although current models support contexts of 100K-1M tokens, this setup is
costly to serve because the memory consumption of the KV cache scales with
input length. We explore an alternative: training a smaller KV cache offline on
each corpus. At inference time, we load this trained KV cache, which we call a
Cartridge, and decode a response. Critically, the cost of training a Cartridge
can be amortized across all the queries referencing the same corpus. However,
we find that the naive approach of training the Cartridge with next-token
prediction on the corpus is not competitive with ICL. Instead, we propose
self-study, a training recipe in which we generate synthetic conversations
about the corpus and train the Cartridge with a context-distillation objective.
We find that Cartridges trained with self-study replicate the functionality of
ICL, while being significantly cheaper to serve. On challenging long-context
benchmarks, Cartridges trained with self-study match ICL performance while
using 38.6x less memory and enabling 26.4x higher throughput. Self-study also
extends the model's effective context length (e.g. from 128k to 484k tokens on
MTOB) and surprisingly, leads to Cartridges that can be composed at inference
time without retraining.