PyroDash-4B-SFT

---

This repository hosts PyroDash-4B-SFT — the offload cold-start (Stage 2) checkpoint of PyroDash, fine-tuned from Qwen/Qwen3.5-4B.

Companion models: GRPO λ=0.05 · GRPO λ=0.6

---

We propose PyroDash, a token-level dynamic reasoning paradigm for collaborative inference between small and large language models. PyroDash enables the small model to autonomously emit the control token <|llm_offload|> during autoregressive streaming decoding; the collaboration engine then dynamically offloads the local reasoning chain to a large model based on this control signal. This approach requires neither an additional router model nor retraining of the large model, and is naturally compatible with closed-source LLM services.

During training, PyroDash follows a three-stage progressive optimization pipeline: (1) train the control-token embedding layer so the small model acquires basic offloading expressiveness; (2) cold-start the offload capability (this checkpoint) to establish a collaboration pattern between the small and large models; and (3) apply GRPO reinforcement learning that jointly optimizes the dynamic offloading policy with a task-accuracy reward and a large-model call-cost penalty, achieving an adaptive balance between reasoning quality and compute cost.

Model Details

Item	Value
Base model	Qwen/Qwen3.5-4B
Stage	(2) Offload cold-start SFT (LoRA → merged)
Control token	<|llm_offload|>
SFT dataset	EasyHard-24K
Expert LLM (eval)	GLM-5.2-FP8
Precision	bfloat16

Quick Start

1. Setup

git clone https://github.com/PyroMind-Dynamics/pyroDash.git
cd pyroDash
pip install -r requirements.txt

2. Run evaluation (evaluation/math_eval.sh)

Edit placeholders in evaluation/math_eval.sh, then:

bash evaluation/math_eval.sh

The script (1) starts a local vLLM server for the small model on port 8001, (2) runs math_eval.py, and (3) stops vLLM on exit.

Parameters

Variable / flag	Meaning	Example
MODEL	Local merged model path (vLLM serve + tokenizer)	/path/to/your/merged_model
--glm-base-url	OpenAI-compatible API for the large/relay model	http://your-glm-host:8000/v1
--glm-api-key	API key for that endpoint	your-glm-api-key
--glm-model	Served model name on the GLM side	your-glm-model
--output-dir	Per-dataset JSON output directory	./results_500
--datasets	Benchmarks (space-separated)	gsm8k minerva olympiad aime2024 aime2025

Tokenizer must include the special token <|llm_offload|>.

Results

Method	Avg. Acc. (%)	LLM Token Ratio (%)	Avg. LLM Calls	Cost ($)
Qwen3.5-4B	28.36	0.00	0.000	2.26
Qwen3.5-4B (+SFT) ← this	46.25	0.00	0.000	1.32
RouteLLM (~75% GLM-5.2-FP8)	52.74	77.37	0.808	44.62
GlimpRouter (τ=0.9)	54.20	75.11	1.20	31.61
PyroDash (λ=0.1)	55.29	8.19	0.058	4.71
PyroDash (λ=0.6)	54.55	1.90	0.012	1.78
PyroDash (λ=0.05)	64.04	95.34	0.975	39.29
GLM-5.2-FP8	57.68	100.00	1.000	49.36

Resources

Resource	Link
Project website	PyroMind-Dynamics.github.io/pyroDash
Code	github.com/PyroMind-Dynamics/pyroDash
SFT dataset (EasyHard-24K)	huggingface.co/datasets/pyromind/easyhard-24k
Hugging Face org	huggingface.co/pyromind

Citation

@misc{pyrodash2026,
  title        = {PyroDash: Cost-Efficient Token-Level Small-Large Model Collaborative Inference},
  author       = {{PyroMind Dynamics}},
  year         = {2026},
  note         = {Preprint}
}

@misc{pyromind2026easyhard24k,
  title        = {{EasyHard-24K} v0.02},
  author       = {{PyroMind Dynamics}},
  year         = {2026},
  howpublished = {\url{https://huggingface.co/datasets/pyromind/easyhard-24k}}
}

License

Apache 2.0 (derived from Qwen3.5-4B).