Open weight models in 2026 and the releases that matter

The strongest open weight models of 2026 come from Chinese labs: Xiaomi's MiMo-V2.6-Pro, Zhipu's GLM-5.3 and Moonshot's Kimi K3 top the Artificial Analysis open weights ranking as read on 30 September 2026. The best open models trail the closed frontier by about four months on one independent tracker, and several of the largest releases no longer use MIT or Apache 2.0. This note covers releases from January to the end of September 2026. September alone is in our September 2026 model roundup.

The open weight models of 2026 at a glance

Figures below come from each model card or the lab's announcement. "Active" is the number of parameters used for each token in a mixture-of-experts (MoE) model, where only some of the network's expert blocks run at a time.

DeepSeek released the general availability version, DeepSeek-V4-Pro-0813, on 13 August 2026 under MIT; its card gives 1.7T parameters against 1.6T on the April preview card, and recommends a single node of four Nvidia GB300s for serving it. DeepSeek-V4.1-Flash activates 8B parameters per token during prefill and 16B during decode, and accepts images as well as text. Both Qwen3.8 context figures are native, extendable to about 1M. The large Qwen3.8 checkpoint is text only and its model card gives a custom licence, although some press coverage described the whole release as Apache 2.0.

How far open models trail the closed frontier

• Epoch AI found on 29 May 2026 that since January 2026 the most capable open weight models have lagged frontier closed models by an average of four months on its Epoch Capabilities Index, with an average gap of 8 points.
• The UK AI Security Institute reported on 17 July 2026 that recent open weight models lag closed models on cyber capabilities by 4 to 7 months, narrower than the 6 to 10 months it measured through 2025.
• On the Artificial Analysis leaderboard read on 30 September 2026 (Intelligence Index v4.3.2), the top proprietary entry, Claude Opus 5.5 at maximum effort, scored 58. The top open weights model, MiMo-V2.6-Pro, scored 46, followed by GLM-5.3 (max) at 45 and Kimi K3 (max) at 44.

Artificial Analysis made its tasks harder in version 4.3 on 7 September 2026, which lowered scores. Earlier scores are on a different scale and cannot be compared with these.

On 30 September 2026 the top six on the open weights page were all from Chinese labs; the best from elsewhere were K2 Horizon (Institute of Foundation Models, 31), Thinking Machines' Inkling (25) and Nemotron 3 Ultra (23).

The US and European releases

Most US and European releases are smaller and suit local use. Google's Gemma 4, released on 2 April 2026, comes in E2B and E4B sizes with 128K context, a 26B MoE with 3.8B active parameters and a 31B dense model, all under Apache 2.0.

Meta released Muse Glimmer, on 10 August 2026, a 30B dense model distilled from its proprietary Muse Spark. Meta says that at 4-bit precision the weights need under 20 GB and that it runs on a single consumer GPU. When Meta launched Muse Spark on 8 April 2026 it said it hoped to open-source future versions.

Nvidia's Nemotron 3 Ultra, released on 4 June 2026, is a hybrid Mamba-Attention MoE with 550B total and 55B active parameters, pretrained on 20 trillion tokens, according to Nvidia's developer blog. Nvidia has also agreed to buy Hugging Face, where most of these weights are published (our note on the deal).

Mistral's open releases in 2026 included Mistral Small 4 (Apache 2.0) and Mistral Medium 3.5, which its model documentation lists under a Modified MIT licence. As of 30 September 2026, Mistral Large 3 (2 December 2025, 675B total and 41B active, Apache 2.0) remained its biggest open release.

OpenAI's Hugging Face organisation, checked on 30 September 2026, lists no general purpose gpt-oss model newer than gpt-oss-120b and gpt-oss-20b from August 2025.

Security-trained models: GLM-5.3 and MiMo-V2.6

Zhipu's GLM-5.3 model card says the model uses the same base as GLM-5.2 and that every gain comes from post-training. It lists "Emergent Cyber Capability", claims state of the art on the CyberGym vulnerability discovery benchmark (84.5 in its own set-up) and says the model more than doubles GLM-5.2 on exploitation benchmarks. The Decoder reported on 14 August 2026 that Zhipu said GLM-5.3 was trained with data and environments built to find software vulnerabilities, had found 2,436 vulnerabilities across 269 projects, and that its weights would follow once security reviews were complete.

The GLM-5.3 licence reflects that caution. Where GLM-5.2 and GLM-5.3-Flash are MIT, the GLM-5.3 licence requires any licensee that runs a model-as-a-service business with more than 10 billion US dollars in revenue over 12 months to pass Z.AI's security review before use.

Xiaomi's MiMo-V2.6-Pro-RL card describes one reinforcement learning run across coding, general agents, visual tasks and cyber security, and reports a CyberGym score of 94.0. Xiaomi also published more than 7,000 training environments, including vulnerability reproduction, according to Open Source For You.

The CyberGym numbers come from each lab's own set-up and should not be ranked against each other. Defenders use them too: in a post on 16 July 2026, Hugging Face said it analysed more than 17,000 attack events with GLM-5.2 on its own servers after commercial APIs refused the requests.

Licences are the thing to read first

MIT (DeepSeek, GLM-5.2, GLM-5.3-Flash, MiMo) and Apache 2.0 (Gemma 4, Qwen3.8-27B, Muse Glimmer, most Mistral models) are standard open source licences. Kimi K3, MiniMax-M3, GLM-5.3 and the large Qwen3.8 checkpoint use the lab's own terms, and Mistral Medium 3.5 uses a modified MIT licence. Nemotron 3 Ultra uses OpenMDW-1.1, a Linux Foundation licence for model weights, according to its model card.

For a UK or EU company, the rule is to read the licence file in the repository, not the press release. Terms differ within families: GLM-5.3 against GLM-5.2, and the 2.4T Qwen3.8 against the 27B.

What to watch

Alibaba also said on 22 September 2026 that Qwen 4.5 and Qwen 5 are projected to scale to 5 to 10 trillion parameters. In our view, if those are released as weights, running the largest open models will need clusters, and teams on their own hardware will stay with the 27B to 31B class.

Sources

• Hugging Face, "DeepSeek-V4-Pro" model card, April 2026: DeepSeek-V4-Pro
• Hugging Face, "DeepSeek-V4-Pro-0813" model card, 13 August 2026: DeepSeek-V4-Pro-0813
• Hugging Face, "DeepSeek-V4.1-Flash" model card, September 2026: DeepSeek-V4.1-Flash
• Hugging Face, "Kimi K3" model card, July 2026: Kimi-K3
• Hugging Face, "GLM-5.2" model card, June 2026: GLM-5.2
• Hugging Face, "GLM-5.3" model card and licence, August 2026: GLM-5.3
• Hugging Face, "GLM-5.3-Flash" model card, August 2026: GLM-5.3-Flash
• TechNode, "Zhipu identifies Ox Alpha as GLM-5.3-Flash and releases model weights", 27 August 2026: TechNode
• The Decoder, "Zhipu AI releases GLM-5.3", 14 August 2026: The Decoder
• Hugging Face, "Qwen3.8-27B" model card, August 2026: Qwen3.8-27B
• Hugging Face, "Qwen3.8-2.4T-A95B" model card, August 2026: Qwen3.8-2.4T-A95B
• Hugging Face, "MiniMax-M3" model card, June 2026: MiniMax-M3
• Hugging Face, "MiMo-V2.6-Pro-RL" model card, September 2026: MiMo-V2.6-Pro-RL
• Open Source For You, "Xiaomi open sources MiMo-V2.6 AI models", 24 September 2026: Open Source For You
• Google, "Gemma 4", 2 April 2026: Gemma 4
• Meta, "Introducing Muse Glimmer", 10 August 2026: Muse Glimmer
• Meta, "Introducing Muse Spark", 8 April 2026: Muse Spark
• Nvidia, "GTC Taipei at Computex 2026", 4 June 2026: Nvidia blog
• Nvidia, "Nemotron 3 Ultra leads open models on accuracy and efficiency in agentic RTL coding", 26 July 2026: Nvidia developer blog
• Hugging Face, "NVIDIA-Nemotron-3-Ultra-550B-A55B-BF16" model card, June 2026: Nemotron 3 Ultra
• Mistral AI, "Introducing Mistral 3", 2 December 2025: Mistral 3
• Mistral AI, "Models" documentation, read 30 September 2026: Mistral models
• Mistral AI, "Changelogs", read 30 September 2026: Mistral changelog
• Tech Times, "Mistral AI targets frontier gap with open weight model", 6 July 2026: Tech Times
• Hugging Face, "OpenAI" organisation page, read 30 September 2026: OpenAI on Hugging Face
• Epoch AI, "Open and closed model gap", 29 May 2026: Epoch AI
• AI Security Institute, "How far behind the frontier are leading open weight models on cyber", 17 July 2026: AISI
• Artificial Analysis, "Intelligence Index v4.3", 7 September 2026: Artificial Analysis v4.3
• Artificial Analysis, "Models" and "Open source models" leaderboards, read 30 September 2026: leaderboard, open weights
• Hugging Face, "Security incident, July 2026", 16 July 2026: Hugging Face blog
• Alibaba Cloud, "Apsara Conference 2026", 22 September 2026: Alibaba Cloud blog
• Nvidia, "Nvidia to acquire Hugging Face", 3 September 2026: Nvidia blog
• Nvidia, Form 8-K on the Hugging Face agreement, 2 September 2026: SEC filing