Contrastive Language Model (CLM) is a new class of System One model trained with a contrastive learning objective that connects states and actions. CLM-8B consists of two small projection heads (a state head and an action head) on top of a frozen Qwen3-8B encoder trained with a bidirectional InfoNCE loss.
- Training: pre-trained on ~60M Nemotron Q&A pairs, mid-trained on ~30M synthetic hard negatives, post-trained on ~1M agentic trajectories.
- Zero-shot: on par with Jev on computer-use, gaming and tool-calling tasks, with up to 9× lower latency.
- Fine-tuned as a verifier: SOTA on DeepSWE (81.6%) and Terminal-Bench 2.1 (87.6%), 4–6× faster than Jev.
- State & Action Caching: states and actions are encoded separately, so action embeddings can be reused. With ~1k candidates, CLM is 13× faster than Jev.
Usage
With the contrastive-lm package
pip install contrastive-lm
# 1. encoder (Qwen3-8B embeddings)
vllm serve Qwen/Qwen3-8B --served-model-name qwen3-8b --runner pooling --max-model-len 2048 --port 8090 &
# 2. API + playground at http://localhost:8700/ (fetches CLM_v0.1-8B.pt into ~/.cache/clm/)
clm-serve
Ask typed questions about a state:
from clm import CLMClient, Choice, Noul, Score
client = CLMClient() # http://127.0.0.1:8700 by default
r = client.system_one(
state="Customer: my invoice was charged twice and nobody answers the phone!",
questions={
"urgency": Noul(instructions="Is this urgent?"),
"department": Choice(instructions="Which team should handle this?",
criteria={"billing": "Charges, invoices, refunds",
"technical": "Bugs and outages"}),
"frustration": Score(instructions="How frustrated is the customer?",
criteria=["Calm", "Frustrated", "Very angry"]),
},
)
print(r.answers["department"].choice) # billing
print(r.answers["department"].probabilities) # {'billing': 0.93878, 'technical': 0.06122}
Or rank free-form candidates (best-of-N solutions, tool names, next moves):
from clm import Engine
engine = Engine(emb_url="http://127.0.0.1:8090/v1/embeddings")
engine.rank("What causes tides on Earth?",
["The Moon's gravitational pull.", "Photosynthesis in plants.", "Because the Earth is round."])
# [{'rank': 1, 'candidate': "The Moon's gravitational pull.", 'prob': 0.993}, ...]
Fine-tuning
Only the heads are trained, so fine-tuning is cheap. This checkpoint is the starting point for the DeepSWE and Terminal-Bench heads.
git clone https://github.com/Contrastive-LM/CLM.git && cd CLM && pip install -e .
hf download Contrastive-LM/deepswe-clm-heads-8k heldout_tasks.json --local-dir heads/deepswe
python train/finetune.py --task clm --init-ckpt "$(clm-download)" --out-dir runs/deepswe \
--holdout-tasks heads/deepswe/heldout_tasks.json --batch 512
See the fine-tuning guide.
Playground
clm-serve also serves a web playground at http://localhost:8700/.
Limitations
- Encoder-locked: the heads require Qwen3-8B last-token-pooled embeddings.
- No generation: CLM only scores the candidates you give it, and its probabilities are relative to that set.
- Verifier results need fine-tuning: the SOTA agentic-benchmark numbers come from fine-tuned heads, not this checkpoint zero-shot.
- Generalization: CLM-8B is one rung of our scaling ladder. A multimodal CLM-35B, trained with more data, compute and parameters for stronger generalization, is coming in early October.
Citation
@misc{kwok2026contrastivelanguagemodels,
title={Contrastive Language Models: A System One Model for Fast and Generalizable Decision-Making},
author={Jacky Kwok and Hangoo Kang and Tarun Suresh and Jon Saad-Falcon and Marco Pavone and Christopher Ré and Azalia Mirhoseini},
year={2026},
note={Notion Blog},
url={https://contrastive-lm.notion.site}
}
License
The CLM-8B weights are released under the Apache 2.0 License. The base encoder Qwen3-8B is also Apache 2.0.