GLM-5.1

GLM-5.1 is the first open-weight model to claim the #1 position on SWE-Bench Pro, scoring 58.4 — ahead of GPT-5.4 (57.7) and Claude Opus 4.6 (57.3). Released April 7, 2026 by Z.AI under an MIT license, it costs $1.40/M input tokens versus Claude Opus 4.7’s $5.00/M, making it the most cost-effective frontier-class coding model available today. What Is GLM-5.1? The Open-Source Frontier Model from Z.AI GLM-5.1 is a 754B-parameter Mixture-of-Experts language model developed by Z.AI (formerly Zhipu AI) and released on April 7, 2026, under the MIT license. It activates only 40B parameters per forward pass via its sparse MoE routing, which delivers frontier-tier reasoning at significantly lower inference cost than dense models of comparable quality. The architecture combines DeepSeek Sparse Attention (DSA) for efficient long-context processing, a 203K-token context window, and asynchronous reinforcement learning via Z.AI’s proprietary “slime” training framework. In independent benchmarking by BenchLM, GLM-5.1 ranks 14th out of 115 models with an overall composite score of 83/100. What sets it apart is the combination of open weights, commercial-use permissive licensing, and a demonstrated capability peak at software engineering tasks that no prior open-weight model has matched. Teams can access it via the Z.AI API, self-host via Hugging Face and Ollama, or integrate it as a drop-in replacement for the OpenAI SDK through vLLM’s OpenAI-compatible endpoint. ...

GLM-5.1 is the first open-weight model to top SWE-Bench Pro, scoring 58.4 against GPT-5.4 (57.7) and Claude Opus 4.6 (57.3) — at API prices 5–10x lower than Anthropic’s flagship. It is not a universal winner, but for coding and agentic tasks, it has genuinely closed the gap with frontier closed models. What Is GLM-5.1? The Open-Weight Model That Shocked the Leaderboard GLM-5.1 is an open-weight large language model released by Zhipu AI (Z.ai) in April 2026, built on a 754-billion-parameter Mixture-of-Experts (MoE) architecture that activates only 40 billion parameters per token — the same efficiency design used by Mixtral and DeepSeek-V3. On April 7, 2026, GLM-5.1 became the first open-source model to claim the global #1 position on Scale AI’s SWE-Bench Pro leaderboard, scoring 58.4% against GPT-5.4 at 57.7% and Claude Opus 4.6 at 57.3%. That ranking held for 9 days before Claude Opus 4.7 reclaimed the top spot at 64.3%. The model ships under an MIT license, runs on vLLM and SGLang, supports a 200K-token context window with up to 128K output tokens, and was trained entirely on Huawei Ascend 910B chips — zero Nvidia GPU involvement. As of May 2026, it sits at #18 overall on Chatbot Arena and holds the #1 open-source model slot. For teams doing high-volume code generation or autonomous agent workflows, GLM-5.1 is the first open-weight option worth taking seriously against paid frontier APIs. ...