GLM-5.1

GLM-5.1 is an open-source model from Z.AI, released on April 7, 2026. It is accessible for free via API at docs.z.ai or through OpenRouter (z-ai/glm-5.1), with model weights available on Hugging Face under an MIT license. The model is optimized for agentic engineering: autonomously planning, writing code, running tests, and continuously iterating on a task for up to 8 hours without human intervention. It supports a 200K-token context window, 128K output tokens, function calling, structured outputs, thinking mode, and MCP integration. Best suited for complex SWE tasks such as full-feature development, end-to-end debugging, and CI/CD pipeline automation; it is not suited for multimodal workloads (no image/video input support).