The Evolution of Large Language Model Architectures: From the Transformer to Hybrid Models (2017-2026)
Preprint, version 1.0 (September 2026) The Transformer of 2017 still sits at the core of every current large language model, yet almost everything around it has been rebuilt, some parts repeatedly. This survey traces the architectural development of text-only LLMs from 2017 to early 2026 as four epochs, each driven by...