Kev 4B lands on OpenRouter — first open System One model on a major gateway
On 25 September 2026, OpenRouter shipped Kev 4B, Jared Palmer’s open-weight System One model (announcement).
This makes Kev 4B the first open System One model available through a major LLM gateway, alongside the hosted Jev from TypeSafe.
What it means
- Model ID:
jaredpalmer/kev-4b - Pricing: $0.01/1M input tokens, output free
- API: Same as Jev — if you already call Jev on OpenRouter, switching means changing one field
{
"model": "jaredpalmer/kev-4b"
}Why this matters
Kev 4B is a LoRA adapter + pointer head on Qwen3.5-4B, trained to match the Jev contract. The weights are open on Hugging Face (jaredpalmer/kev-4b).
The OpenRouter integration validates that third-party System One adapters can run on production gateway infrastructure. Developers who want the Jev API with open weights now have a hosted option — no local server required.
Limits
Kev 4B is a prototype, not a production peer to Jev:
- JevBench v1.4.2 ranks Kev 4B at #24 (36.1 overall) vs Jev at #1 (63.0)
- Transfer gap vs Jev is ~-19pp on out-of-training data
- Not recommended for production decisions affecting people without your own labeled eval
See the Kev model page for full benchmarks and caveats.
Engagement
The announcement reached 256 likes and 22,778 views. Jared Palmer quote-tweeted with “Kev-4B is now on @OpenRouter”.