---
base_model:
- LiquidAI/LFM2.5-350M
library_name: transformers
license: other
license_name: lfm1.0
license_link: LICENSE
pipeline_tag: text-generation
language:
- en
tags:
- synth
- synthlabs
- lfm
- lfm2
- reasoning
- text-generation
datasets:
- PleIAs/SYNTH
- mkurman/medical-reasoning-synthlabs-I
- mkurman/gsm8k-SynthLabs-reasoning
---

# LFM2.5-350M-SYNTH

A 350M-parameter **reasoning** model fine-tuned from [LiquidAI/LFM2.5-350M](https://huggingface.co/LiquidAI/LFM2.5-350M) on
synthetic reasoning data. It produces explicit chain-of-thought (`<think> … </think>`) before answering, and is small enough
to run on CPU or modest GPUs while retaining the base model's 128k context window.

## Highlights

- **Reasoning-first**: trained on SynthLabs-style traces for math, medical, and general reasoning.
- **Compact & fast**: 350M params on the hybrid **LFM2** architecture (convolution + sparse full-attention blocks), bf16.
- **Long context**: inherits the base model's 128k `max_position_embeddings`.
- **Chat + tools**: ChatML format with native tool-calling special tokens.

## Model details

```
                │                                                  │          │         │        │
────────────────┼──────────────────────────────────────────────────┼──────────┼─────────┼────────┼────
Base model      │ LiquidAI/LFM2.5-350M                             │          │         │        │
Architecture    │ `Lfm2ForCausalLM` (hybrid conv / full-attention) │          │         │        │
Parameters      │ ~350M                                            │          │         │        │
Hidden size     │ 1024                                             │          │         │        │
Layers          │ 16 (12 conv + 4 full-attention)                  │          │         │        │
Attention heads │ 16 (8 KV heads, GQA)                             │          │         │        │
Vocab size      │ 65,536                                           │          │         │        │
Context length  │ 128,000                                          │          │         │        │
Precision       │ bfloat16                                         │          │         │        │
Chat format     │ ChatML (`<                                       │ im_start │ >` / `< │ im_end │ >`)
```
## Training

Fully fine-tuned for 4,000 steps on a single A100:

- Sequence length: 2,048
- Effective batch size: 64
- Optimizer: AdamW, LR 5e-5, warmup ratio 0.03
- Precision: bf16

Datasets

- PleIAs/SYNTH (https://huggingface.co/datasets/PleIAs/SYNTH)
- mkurman/medical-reasoning-synthlabs-I (https://huggingface.co/datasets/mkurman/medical-reasoning-synthlabs-I)
- mkurman/gsm8k-SynthLabs-reasoning (https://huggingface.co/datasets/mkurman/gsm8k-SynthLabs-reasoning)

## Usage

```python
from transformers import AutoModelForCausalLM, AutoTokenizer
import torch

model_id = "mkurman/LiquidAI-LFM2.5-350M-SYNTH"
tok = AutoTokenizer.from_pretrained(model_id)
model = AutoModelForCausalLM.from_pretrained(model_id, dtype=torch.bfloat16, device_map="auto")

messages = [{"role": "user", "content": "Natalia sold 48 clips in April and half as many in May. How many in total?"}]
inputs = tok.apply_chat_template(messages, add_generation_prompt=True, return_tensors="pt").to(model.device)

out = model.generate(inputs, max_new_tokens=512, do_sample=True, temperature=0.6, top_p=0.95)
print(tok.decode(out[0][inputs.shape[-1]:], skip_special_tokens=True))
```

The model emits its reasoning inside <think> … </think> followed by the final answer.

## Evaluation

TODO

## Intended use & limitations

Research and experimentation with small reasoning models. As a 350M model trained largely on synthetic data, it can
hallucinate and make reasoning errors. Not intended for medical, legal, or other high-stakes decisions - outputs must be
independently verified.

## License

Released under the LFM Open License (lfm1.0); see LICENSE (LICENSE).

## Citation

```bibtex
@misc{kurman2025lfm25synth,
  title  = {LFM2.5-350M-SYNTH},
  author = {Kurman, Mariusz},
  year   = {2026},
  url    = {https://huggingface.co/mkurman/LiquidAI-LFM2.5-350M-SYNTH}
}
```