Model licences and attribution

Since 9 October 2026, System1 Models operates under the name Decision Models (decisionmodels.io). References to System1 Models and system1models.ai in this document mean Decision Models and decisionmodels.io; nothing else changes.

Last updated: 2 October 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 — Surogate Rune 26B-A4B v3 (EU and Peer-to-Peer when available) / Winnow-12B fallback

• EU tier and Peer-to-Peer when spare capacity permits: Surogate Rune 26B-A4B v3 by Invergent (Surogate), served from the pinned weights revision c6b360d47895bb77bdf3805a13ee5a5557ab1921, licensed under the Apache License 2.0.
• Built on Gemma 4 by Google DeepMind, Apache License 2.0. Gemma is a trademark of Google LLC.
• Peer-to-Peer tier and EU overflow: Winnow-12B by EldanRing, licensed under the Apache License 2.0.
• Winnow-12B is a fine-tune of Gemma 4 12B IT by Google DeepMind, released under the Apache License 2.0.

s1-vision — Surogate Rune 26B-A4B v3 (EU and Peer-to-Peer when available) / Jev-Omni only with worldwide opt-in

• EU tier and Peer-to-Peer when spare capacity permits: Surogate Rune 26B-A4B v3 by Invergent (Surogate), as listed under s1-pro above.
• On the EU tier and on Peer-to-Peer without worldwide opt-in there is no fallback model for s1-vision; if Rune is unavailable, requests get a retryable 503.
• Peer-to-Peer keys with worldwide processing opt-in, when capacity is busy (on-demand worldwide GPUs): Jev-Omni by akhilaaa3, licensed under the Apache License 2.0 as stated by its author, served from the pinned weights revision 5addda86ddee081a68fb067477ea100c221b8917.
• Jev-Omni is 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.