yev2-35b-a3b

An open System One decision model on Qwen/Qwen3.6-35B-A3B (Apache-2.0), a mixture-of-experts model with about 35B parameters, of which about 3B are active per token. Give it a state, a question and 2โ€“10 options; it returns a calibrated probability per option from one forward pass, read from the logits of the option letters Aโ€“J. Merged bf16 weights are at the repo root; the LoRA adapter is in adapter/.

yev2 is yev1's training recipe and data on a larger base: same training rows, same hyper-parameters, only the base model changed. For a 48 GB GPU use the FP8 checkpoint, choyiny/yev2-35b-a3b-fp8.

Hardware

Checkpoint Weights Fits on
yev2-35b-a3b (bf16, this repo) 65 GB one 80 GB GPU (A100 80 GB, H100, RTX PRO 6000)
yev2-35b-a3b-fp8 34 GB one 48 GB GPU (L40S, RTX 6000 Ada)

All 35B parameters must be in GPU memory; compute per token is that of a ~3B model.

How to serve

vLLM (recommended). Start the engine, then put yev serve in front of it for the prompt format, letter readout and calibration:

hf download choyiny/yev2-35b-a3b --local-dir yev2-35b-a3b

vllm serve ./yev2-35b-a3b --host 127.0.0.1 --port 8100 --served-model-name yev --dtype bfloat16 \
  --max-model-len 16385 --enable-prefix-caching --generation-config vllm \
  --logprobs-mode processed_logprobs --max-logprobs 26 --max-num-seqs 64 \
  --gpu-memory-utilization 0.85 --trust-remote-code

pip install torch 'yev[serve,train] @ git+https://github.com/xyspacedev/yev'
yev serve --backend vllm --model yev2-35b-a3b --calibration yev2-35b-a3b/calibration.json --model-name yev2-35b-a3b

--max-num-seqs 64 is required: the model's linear-attention layers keep one recurrent-state block per sequence, and vLLM's default of 1,024 sequences does not fit.

transformers: yev serve --model yev2-35b-a3b --calibration yev2-35b-a3b/calibration.json (no sidecar), or run python inference_example.py for a self-contained script (--adapter loads the base + LoRA).

curl -s localhost:8000/v1/systemone -H 'content-type: application/json' -d '{
  "state": "I was charged twice. Please help.",
  "questions": {"billing": {"instructions": "Is this message about billing?", "type": "noul"}}}'

yev serve also exposes an OpenAI-compatible /v1/chat/completions.

Benchmarks

Benchmark yev1-4b yev2-35b-a3b yev2-35b-a3b-fp8
DecideBench v2.0 test (450), accuracy 79.3 88.0 87.6
DecideBench v2.0 test, pair accuracy 62.7 78.2 77.3
DecideBench v2.0 test, ECE 0.078 0.058 0.059
JevBench public (231), accuracy 82.7 90.5 89.2
JevBench public, hard tier (111) 67.6 81.1 78.4

DecideBench v2.0 test was never inspected or used for training or model selection. The 95 % interval on yev2's DecideBench v2 accuracy is 84.9โ€“90.9. On the DecideBench v2 leaderboard it places 5th of 27 decision models, and 2nd among those that run on your own hardware. Its weakest family is release-gating decisions (52 %), which every decision model on the leaderboard finds hard.

Development set (3,963 rows, held out from training): accuracy 97.0 (yev1: 95.2), group accuracy 93.4 (89.1), ECE 0.017 (0.021). With options reordered, the answer stays the same on 98.9 % of rows (yev1: 98.4 %).

Speed and cost

DecideBench v2, one NVIDIA RTX PRO 6000 Blackwell (96 GB), vLLM 0.31.0, yev serve, 4 requests in flight.

p50 p95 Throughput Cost per 1M decisions
yev2-35b-a3b (bf16) 0.38 s 0.72 s 9.7 req/s $95
yev2-35b-a3b-fp8 (45 GiB cap) 0.30 s 0.54 s 11.3 req/s $78
yev1-4b (bf16) 0.28 s 0.60 s $71

Cost is wall-clock GPU time at $3.36 per hour (AWS g7e.2xlarge on-demand) divided by decisions; DecideBench prompts average about 3,300 tokens.

Training

LoRA r 64, ฮฑ 128, dropout 0.05 on the attention, linear-attention and shared-expert projections; routed experts frozen. 1 epoch, learning rate 1e-4, 80,730 rows (101.5M tokens), 3,955 steps, 7.9 h on one RTX PRO 6000. Per-type temperatures in calibration.json were fitted on 3,368 held-out rows. Python 3.12, torch 2.14.1+cu130, transformers 5.22, peft 0.21.2, flash-linear-attention 0.6.0, causal-conv1d 1.7.0. Training code: xyspacedev/yev, configs/yev2/yev2-qwen36-35b-a3b.json.

Licence

Weights: Apache-2.0. Training-data credits are in NOTICE and ATTRIBUTION.json. Recipe after Together's "How to train your own Jev".

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