GLM vs. GPTNeo

GLM

GLM is Z.ai's open-weight model family for reasoning, coding, agents, and long-horizon work. GLM-5.2 is the current generation with a one-million-token context window.

The GLM family began with bilingual pretrained models and evolved through the ChatGLM and GLM-4 generations. GLM-5 scaled the mixture-of-experts architecture to 744B total parameters with 40B active parameters. GLM-5.2, released in June 2026, adds a stable one-million-token context window, stronger long-horizon coding and agent performance, adjustable reasoning effort, and efficiency improvements for sparse attention. Its weights are available under the MIT license.

Further reading

• z.ai/blog/glm-5
• z.ai/blog/glm-5.2
• huggingface.co/zai-org

GPTNeo

GPTNeo is a model released by EleutherAI to try and provide an open source model with capabilities similar to OpenAI's GPT-3 model. One of the earliest such models, GPTNeo was trained on The Pile, Eleuther's corpus of web text.