GLM 5.1 is Z.ai's April 2026 open-weight assistant in the GLM-5 line—the one people reach for when they want stronger chat and writing than base GLM-5. Our tests show solid helpfulness and comprehension, with creative writing that feels more natural and playful than later coding-leaning siblings. Empathy is warm enough for everyday support, though not Claude-tier. Instruction following is reliable for multi-step plans. A strong open assistant for drafting, brainstorming, and bilingual help; escalate to GLM 5.2 when the job is a long, messy project that must stay on rails.