Qwen 3.5 9B - SWE-smith

This is a model trained using DPPO on top of Qwen 3.5 9B for use as a terminal-agent. This model was trained as an ablation on the swe-smith dataset.

This model is part of a collection of terminal agents in various sizes.

Additionally, we provide model checkpoints as branches of the repository. The main model checkpoint is step 20 as this performed best on TBLite.

Evaluation Results

Model	TB Lite	TB 2.1
Qwen 3.5 9B	41.9 +/- 2.7	16.1 +/- 3.7
Qwen 3.5 9B Endless	52.6 ± 1.4	25.5 ± 1.4
Qwen 3.5 9B CLI Gym	50.7 ± 5.9	25.1 ± 1.4
Qwen 3.5 9B TermiGen	49.4 ± 1.5	25.1 ± 1.9
Qwen 3.5 9B Swe-Smith (this model)	47.2 ± 2.2	21.0 ± 0.5
Qwen 3.5 9B Terminal-Traj	45.8 ± 2.7	18.0 ± 0.0
Qwen 3.5 9B Open-thoughts	53.0 ± 0.7	25.1 ± 3.7
Tmax 9B	57.2 ± 2.5	28.8 ± 3.7

For details on evaluation methodology please check our paper. In general, we used a podman (docker) backend with default timeouts and custom harness similar to mini-swe-agent.

Model Details

Model Description

Developed by: Ai2
Language(s) (NLP): English
License: Apache 2.0
Finetuned from model: Qwen 3.5 9B
Dataset: SWE-Smith

Hyperparameters

This model was trained using DPPO with the following hyperparameters:

base model: hamishivi/Qwen3.5-9B
Max prompt tokens: 2048
Max per-turn tokens: 16384
Max overall tokens: 65536
Pack length: 67584
Per-device train batch size: 1
Unique prompts per rollout: 8
Samples per prompt rollout: 32
Async steps: 4
Max steps: 64
Learning rate: 1e-6
LR scheduler: constant
Total training steps: 500 steps (this checkpoint is from 200 steps of training, which performed best on TBLite)
Sampling Temperature: 1.0
KL Beta: 0.0
Loss fn: DPPO
Divergence: binary TV
TV threshold: 0.1
Advantage normalization: centered (no division by stdev)
FP32 LM head: true

For more details on training, please see our codebase.

License

This model is licensed under Apache 2.0. It is intended for research and educational use in accordance with Ai2's Responsible Use Guidelines.

Citation

If you use our model or data, please cite our paper:

@misc{ivison2026tmaxsimplerecipeterminal,
      title={Tmax: A simple recipe for terminal agents}, 
      author={Hamish Ivison and Junjie Oscar Yin and Rulin Shao and Teng Xiao and Nathan Lambert and Hannaneh Hajishirzi},
      year={2026},
      eprint={2606.23321},
      archivePrefix={arXiv},
      primaryClass={cs.CL},
      url={https://arxiv.org/abs/2606.23321}, 
}