---
license: mit
tags:
  - chess
  - transformer
  - recurrent
  - policy
  - opening
  - pytorch
library_name: pytorch
---

# 99M opening specialist (squares64)

Same **99M** squares64 architecture as
[`avewright/chess-transformer-100m-squares64`](https://huggingface.co/avewright/chess-transformer-100m-squares64),
finetuned on `≥26`-piece positions (one-hot best first move) from
[`Lichess/chess-position-evaluations`](https://huggingface.co/datasets/Lichess/chess-position-evaluations)
via [`avewright/lichess-opening-bestline`](https://huggingface.co/datasets/avewright/lichess-opening-bestline).

This file is **`latest.pt` at opening-FT step 8000** (2026-09-14 14:42 UTC).
Train loss ~1.7585. Frozen holdout hard CE ~1.4045.

Not the generalist incumbent, the puzzle expert, the Syzygy expert, or the endgame expert.

## Training

- Warm start: public 99M `latest.pt` (weights only), then full resume.
- Split: position-hash 80/20 (seed 277). Frozen piece-stratified val 8192.
- One-hot PV1 (`soft_alpha=0`). Pieces 26–32.
- Polar-NorMuon, bs=528. Best disk ckpt at upload: step 8000.

## Files

- `latest.pt`
- `step_008000.pt`
- `model_config.json`
- `train.log`
- `pack.json`