Open-weight "AI engineer" models arrive: Qwen 3.5, GLM-5, MiniMax M2.5
A new wave of open-weight frontier models now rivals closed systems on coding and long-horizon agent tasks, making self-hosted AI engineer workflows practical for backend and data teams. Alibaba’s Qwen 3.5 ships as an open‑weights Mixture‑of‑Experts model (397B total, 17B active) with multimodal input and a 256K context, alongside a hosted Qwen3.5‑Plus variant offering 1M context and built‑in tools; details and early impressions are summarized by Simon Willison’s write‑up of the [Qwen 3.5 release](https://simonwillison.net/2026/Feb/17/qwen35/#atom-everything) and the official [Qwen blog](https://qwen.ai/blog?id=qwen3.5). Z.ai’s GLM‑5 launched open source with top open-model scores on SWE‑bench‑Verified (77.8) and Terminal Bench 2.0 (56.2), plus long‑context and RL‑driven agent training advances, with the announcement and code at [BusinessWire](https://www.businesswire.com/news/home/20260215030665/en/GLM-5-Launch-Signals-a-New-Era-in-AI-When-Models-Become-Engineers) and the [GitHub repo](https://github.com/zai-org/GLM-5). MiniMax M2.5 claims state‑of‑the‑art coding/agent performance (e.g., 80.2% SWE‑Bench Verified) and aggressive cost/speed on its [Hugging Face card](https://huggingface.co/unsloth/MiniMax-M2.5), while hands‑on videos compare real coding runs for GLM‑5 and M2.5; you can also quickly trial free models via [OpenRouter’s free router](https://openrouter.ai/openrouter/free).