Tier 2 Restricted open-weight
What the publisher claims: open-source, open-weight
The one-liner: Permissive licence undercut by a deployment dependency on unreleased upstream patches.
The six questions
weights downloadable, ungated
Apache 2.0
weights load only through Zyphra forks of transformers and vLLM, not upstream releases
architecture, pretraining and post-training methodology described in the technical report; corpus withheld
Limited to moderate.
Zyphra's Apache-2.0 ZAYA1 weights are public, but the transformers and vLLM patches the architecture needs live in Zyphra's own forks, and no open development process is offered beyond filing issues.
License
Apache 2.0 OSI-approved — license source ↗
What is actually released
- weights (8B MoE with 760M active)
- base checkpoint
- technical report arXiv 2605.05365
- evaluation harness
- forked transformers and vLLM branches required for the architecture
Why it matters
Shows that a standard licence does not guarantee open deployment when the runtime lives in private forks.
Sources
- https://huggingface.co/Zyphra/ZAYA1-8B
- https://www.zyphra.com/our-work/zaya1-8b
- https://huggingface.co/api/models/Zyphra/ZAYA1-8B
Derived from the openness dataset behind But Is It Open? — snapshot 2026-11-07 ↗. Scores are qualitative readings of the cited evidence, not verdicts; tier measures openness, not intelligence.