Laghu-Base / README.md
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---
license: apache-2.0
language: [en]
library_name: transformers
pipeline_tag: text-generation
tags: [udgamlabs, small-language-model, trained-from-scratch, research-release, base-model, gemma4]
---
![Laghu-Base · Udgam Labs](./banner.png)
**UDGAM LABS** · Language model · 152M parameters, base
# Laghu-Base
Laghu-Base is the pretrained base model behind [Laghu](https://huggingface.co/udgamlabs/Laghu): 152M parameters,
trained from scratch on 40.0B token positions of English web, educational, maths, code and synthetic text at a
2,048-token context. These are the exponential-moving-average (EMA) weights at the last step, 76,294. On text published in
September and October 2026 it scores 0.919 bits per byte, better than SmolLM2-135M (0.941, pretrained on 2T tokens) and
Falcon-H1-Tiny-90M-Base (0.979), after a $146 pretraining run. It is a text completer, not a chat model. Part of a fully
open research release: code, recipe, checkpoints, evaluations and cost are all public.
**Try it:** [the chat model](https://huggingface.co/udgamlabs/Laghu) · [code on GitHub](https://github.com/udgamlabs/laghu) · [udgamlabs.com/models/laghu](https://udgamlabs.com/models/laghu)
## Quick start
```python
from transformers import AutoTokenizer, AutoModelForCausalLM
tok = AutoTokenizer.from_pretrained("udgamlabs/Laghu-Base")
model = AutoModelForCausalLM.from_pretrained("udgamlabs/Laghu-Base")
inputs = tok("The water cycle begins when", return_tensors="pt") # the tokenizer adds <bos>
out = model.generate(**inputs, max_new_tokens=60, do_sample=True, temperature=0.8, top_p=0.95)
print(tok.decode(out[0], skip_special_tokens=True))
```
Keep prompts and outputs within 2,048 tokens: the model was trained at that length and fails at longer ones (the config
allows 8,192 positions, but recall at 4K is 0%). For long inputs use [Laghu-Base-32K](https://huggingface.co/udgamlabs/Laghu-Base-32K).
The raw (non-EMA) weights of the same step are in the `raw-final/` folder:
`AutoModelForCausalLM.from_pretrained("udgamlabs/Laghu-Base", subfolder="raw-final")`.
## Results
**Zero-shot benchmarks** (lm-eval 0.4.13, bf16, `<bos>` added, CUDA; measured by us for every model, 2026-10-19):
| Model | Params | ARC-E | ARC-C | HellaSwag | PIQA | WinoGrande | 5-task avg | MMLU | GSM8K 5-shot |
|---|---|---|---|---|---|---|---|---|---|
| **Laghu-Base** | 152M | 60.6 | 30.1 | 40.9 | 65.7 | 52.2 | **49.9** | 25.3 | 4.2 |
| GPT-X3-150M | 149M | 63.0 | 31.4 | 45.9 | 71.3 | 53.6 | 53.0 | 24.6 | 4.2 |
| SmolLM2-135M | 135M | 64.5 | 30.0 | 43.0 | 68.3 | 53.0 | 51.8 | 24.5 | 2.0 |
| Falcon-H1-Tiny-90M-Base | 91M | 54.3 | 28.5 | 37.7 | 64.8 | 50.8 | 47.2 | 32.4 | 2.7 |
| Gargi-Base (ours) | 384M | 63.0 | 32.5 | 41.5 | 66.9 | 54.5 | 51.7 | 25.3 | 5.7 |
ARC-C, HellaSwag and PIQA use length-normalised accuracy. Laghu-Base is 5th of the 19 models up to 200M parameters we
measured on 19 October on the 5-task average; the full table is in the technical report.
**Bits per byte on held-out text** (lower is better; one script and the same documents for every model):
| Model | New text (1,695 docs: Wikipedia pages created and arXiv abstracts submitted Sep-Oct 2026) | Web (580) | Reasoning (1,179) |
|---|---|---|---|
| **Laghu-Base** | **0.919** | 0.858 | 0.693 |
| SmolLM2-135M | 0.941 | 0.858 | 0.752 |
| Falcon-H1-Tiny-90M-Base | 0.979 | 0.910 | 0.769 |
| Gargi-Base (ours, 384M) | 0.914 | 0.850 | 0.686 |
| SmolLM2-360M | 0.850 | 0.788 | 0.678 |
## Where it falls short
- Below SmolLM2-135M (51.8) and GPT-X3-150M (53.0) on the commonsense average; near chance on MMLU (25.3).
- Slightly behind our 384M Gargi-Base on all three held-out text sets (the differences are significant).
- Our scaling projection before the run expected 0.900-0.912 bits per byte on new text after a 32K stretch; the measured
value was 0.921, so the run came in worse than planned.
- 2,048-token context only.
- Not instruction-tuned: it continues text and does not follow requests.
## How it was trained
- **Data:** a 52.6B-token pool from 14 public sources (DCLM-Edu and FineWeb-Edu ≈ 35%, FinePhrase ≈ 23%, Ultra-FineWeb
≈ 14.5%, FineMath ≈ 9%, SYNTH ≈ 8.5%, Wikipedia ≈ 3.4%, NVIDIA Nemotron chat and STEM ≈ 5%, permissive GitHub code ≈
1.7%), 13-gram decontaminated against 10 evaluation sets (21,427 documents removed). Shares are the builder's own token
estimates.
- **Run:** 76,294 steps × 524,288 tokens = 40.0B token positions; Muon; token bags (4 tokens per position) for the first
25% of steps, so about 70B tokens were read; cool-down data mix from 80%; learning rate warm-down over the last 65% to 5%
of peak; EMA from 90% (β 0.998); bf16.
- **Compute and cost:** 8× A100 80GB for 13.2 hours, $146.26. About 3.6 × 10¹⁹ FLOPs.
- **Architecture:** Gemma-4 text layout, 28 layers, width 640, 10 query / 2 key-value heads, 512-token sliding window with
every 4th layer global, tied embeddings, our own 32,768-token tokenizer.
Every setting, the data builder and the launch scripts: [GitHub](https://github.com/udgamlabs/laghu). The raw training
states with optimiser at steps 76,000 and 76,294 are in [Laghu-Checkpoints](https://huggingface.co/udgamlabs/Laghu-Checkpoints);
the checkpoints from steps 2,000-74,000 were deleted by a storage clean-up on 2026-10-21, our mistake.
## Intended use and limitations
A base for research: fine-tuning, continued pretraining, interpretability and training-dynamics studies. It has no
safety tuning and continues any text, including harmful or false text.
## Licence
Apache-2.0. Copyright 2026 Udgam Labs LLP. Training-data credits:
[DATA_LICENSES](https://github.com/udgamlabs/laghu/blob/main/docs/DATA_LICENSES.md).
## Citation
```bibtex
@misc{udgamlabs2026laghu,
title = {Laghu: a fully open 152M chat model trained from scratch},
author = {Prasad, Jitesh K},
year = {2026},
howpublished = {Udgam Labs},
url = {https://huggingface.co/udgamlabs/Laghu}
}
```
---
**About Udgam Labs.** Udgam Labs is an independent AI research lab. We work from first principles: before we build, we understand why things work, whether we are training a model, fine-tuning one or applying AI to a new problem. Udgam (उद्गम) is Sanskrit for origin. [udgamlabs.com](https://udgamlabs.com)