Model licences and attribution

Last updated: 27 September 2026

System1 Models hosts open-weight models made by independent authors. We are grateful for their work. We run the published weights unchanged (except for format conversion where noted on the model page) and do not claim authorship. None of the authors below endorses System1 Models, and System1 Models is not affiliated with TypeSafe AI, Google or Alibaba.

s1-fast — Plumb-4B

• Model: Plumb-4B by Christopher House, licensed under the Apache License 2.0.
• Fine-tuned from JevK5 v0.2 by the JevK5 authors (github.com/allebee, huggingface.co/alibiserikbay), Apache License 2.0,
• itself based on Qwen3.5-4B by the Qwen team (Alibaba Cloud), Apache License 2.0.
• The decision prompt and one-pass readout are adapted from SemIf by TheoLeeCJ, MIT License.

s1-pro — Winnow-12B

• Model: Winnow-12B by EldanRing, licensed under the Apache License 2.0.
• Fine-tuned from Gemma 4 12B IT by Google DeepMind, released under the Apache License 2.0.
• Gemma is a trademark of Google LLC.

s1-vision — Jev-Omni (only if listed on /models)

• Model: Jev-Omni by akhilaaa3, licensed under the Apache License 2.0 as stated by its author.
• Built on Gemma 4 12B IT by Google DeepMind, Apache License 2.0.

Notices

The full licence texts and the NOTICE files of the authors are available at /legal/NOTICE.txt and through the API at GET /v1/models (field license).

Use of all models through System1 Models is subject to our Acceptable Use Policy.

"Jev" is a trademark of TypeSafe AI. We use it only to describe compatibility with the Jev typed-decision request format. Some model names above contain "Jev"; they were chosen by their authors, and none of these models is made by, derived from or endorsed by TypeSafe AI.