Chinese AI Model "GLM-5.1" Released for Free, Beats Claude Opus 4.6 in Some Tests and Excels in Multi-Hour Agent Tasks

GLM-5.1 was released on April 7, 2026 by Z.ai under the MIT License.

It is reported as an open model with world-class performance.

In multiple benchmarks it outscored closed models such as GPT-5.4 and Claude Opus 4.6.

Some specific tests still favored Claude Opus 4.6 despite GLM-5.1's advantages.

It ran autonomously on long-horizon agent tasks (8 hours) and improved via 600+ and 1,200 trial iterations.