GLM-4.5 is an open foundation model family from Z.ai (formerly Zhipu AI), published as an open-source project on GitHub where it has gathered about 4,423 stars and was still actively updated in 2026. The series was designed around three capabilities at once โ agentic behavior, deep reasoning, and coding โ often summarized by the team as ARC. Built on a Mixture-of-Experts architecture, the models activate only a fraction of their total parameters per token, which keeps inference costs manageable while retaining the capacity of a much larger dense model.
GLM-4.5 targets the new generation of workloads where a model must do more than chat: it plans multi-step tasks, calls tools, writes and debugs code, and reasons through hard problems before answering. The repository provides the model release, documentation, and usage guidance so developers can download the weights, run them locally or on their own servers, and fine-tune them for domain-specific agents. A hybrid reasoning design lets the same model switch between fast direct answers and extended step-by-step thinking depending on the task.
GLM-4.5 is free as an open-source model release: the weights and code on GitHub can be downloaded and self-hosted at no license cost. Z.ai also offers hosted API access to its models as a separate commercial service for teams that prefer not to run their own GPU infrastructure.
GLM-4.5 suits developers and research teams building AI agents, coding assistants, and reasoning-heavy applications who want an open model they can inspect, fine-tune, and deploy on their own infrastructure instead of depending entirely on a closed API.