Z.ai: GLM 5.1

GLM 5.1 from Z.ai is a text-in, text-out model with a 202,752-token context window, tool use, and reasoning support. Structured output support is unconfirmed. The large context window makes it practical for long-document tasks, and the reasoning capability positions it for multi-step problem solving, though it accepts no image or audio input. On benchmarks, GLM 5.1 scores 75.3 blended across only four benchmarks, so the picture is narrow rather than comprehensive. Its coding score of 92.0 is a standout, while its agentic score of 49.3 is notably weaker, making it a poor fit for autonomous workflow tasks. At $0.98 per million input tokens and $3.08 output, it sits in the mid-range price tier. Developers prioritizing coding assistance who want a long context window at a moderate cost have reason to shortlist it, but teams needing strong agentic performance or verified structured output should look elsewhere.