GLM 5.2 Has a 1M Token Context Window. Here's What That Does to Your API Bill.

Z.ai dropped GLM 5.2 on June 13, 2026, and the benchmarks are hard to ignore.

It's a 744B-parameter Mixture-of-Experts model with roughly 40B active parameters per token, a 1M-token context window, and MIT-licensed weights. It currently ranks #4 out of 124 models on BenchLM's provisional leaderboard with an overall score of 91/100.

For open-source AI, this is a landmark moment. Across three long-horizon coding benchmarks — FrontierSWE, PostTrainBench, and SWE-Marathon — GLM-5.2 is the highest-ranked open-source model, and the only open-weight model that ranks alongside Claude Opus 4.8 and GPT-5.5 on that class of work.

But there's a catch nobody is talking about: a 1M token context window is also a 1M token cost center.

What makes GLM 5.2 different