SPP-T0-MT β€” Base (3B)

Type: base (pretrained) model. Not instruction-tuned and ships no chat template.

Trained with SPP from token zero, followed by an additional reflection-focused midtraining stage resumed from the SPP-T0 checkpoint (replacing the final learning-rate cooldown).

Synthetic Persona Pretraining (SPP)

Synthetic Persona Pretraining (SPP) installs a target value persona during pretraining rather than only during alignment. Value-laden, first-person reflections, generated against a constitution, are appended to a subset of pretraining documents after a special <assistant> token. Attention masking and RoPE position aliasing keep the reflection from changing the continuation of the original document. This model is trained with SPP.

Instruction-tuned counterpart: dlab-spp/t0-mt-3b-instruct.

Model details

  • Architecture: Llama-3.2-3B-shaped, trained from scratch.
  • Tokenizer: the SmolLM2 tokenizer extended with an <assistant> marker and constitution tokens (vocabulary 49280).
  • Pretraining: ~500B tokens on a subset of the Olmo 3 Dolma 3 mixture, with SPP reflections inserted into the safety-annotated documents within it, followed by a reflection-focused midtraining stage on those annotated documents.

Training checkpoints

Intermediate checkpoints are published as git revisions on this repo, so any point in the trajectory can be loaded by passing revision=:

from transformers import AutoModelForCausalLM, AutoTokenizer
import torch

repo = "dlab-spp/t0-mt-3b-base"
tok = AutoTokenizer.from_pretrained(repo)          # identical at every revision
model = AutoModelForCausalLM.from_pretrained(
    repo, revision="step-225000", dtype=torch.bfloat16, device_map="auto"
)
Revision Stage Tokens seen Midtraining step LR phase
step-25000 pretraining ~49.2B β€” stable
step-50000 pretraining ~98.3B β€” stable
step-75000 pretraining ~147B β€” stable
step-100000 pretraining ~197B β€” stable
step-125000 pretraining ~246B β€” stable
step-150000 pretraining ~295B β€” stable
step-175000 pretraining ~344B β€” stable
step-200000 pretraining ~393B β€” stable
step-225000 midtraining start ~442B 0 / 72,895 β€”
step-250000 midtraining β€” 25,000 / 72,895 linear decay
step-275000 midtraining β€” 50,000 / 72,895 linear decay
step-297895 midtraining β€” 72,895 / 72,895 linear decay β€” same weights as main

main always holds the finished model (step 297,895). Only model weights are published β€” optimizer and RNG state are not included, so these revisions support evaluation, probing, and fine-tuning, but not exact resumption of the original run.

Revisions are named by global training step. Up to step-225000 this is the pretraining run of dlab-spp/t0-3b-base, and those revisions have the same weights as the revisions of the same name there. Midtraining started from dlab-spp/t0-3b-base step-225000 and ran 72,895 more steps, replacing the final learning-rate cooldown. The cooldown revisions of dlab-spp/t0-3b-base (step-240000, step-254313) are not part of this model's training history.

Intended use

Research on alignment and safety. As a base model it is meant for continuation, probing, or further fine-tuning; it is not instruction-tuned and can produce incorrect or unsafe content.

Links

Citation

@misc{minder2026syntheticpersonapretrainingalignment,
      title={Synthetic Persona Pretraining: Alignment from Token Zero},
      author={Julian Minder and Viktor Moskvoretskii and Raghav Singhal and Difan Jiao and Andy Arditi and Shaobo Cui and Yiderigun Borjigin and Kartik Bali and Stefan Krsteski and Harsh Raj and Huu Nguyen and Jannik Brinkmann and Ashton Anderson and Roland Aydin and Robert West},
      year={2026},
      eprint={2608.13482},
      archivePrefix={arXiv},
      primaryClass={cs.LG},
      url={https://arxiv.org/abs/2608.13482},
}

License: to be finalised.

Downloads last month
164
Safetensors
Model size
3B params
Tensor type
BF16
Β·
Inference Providers NEW
This model isn't deployed by any Inference Provider. πŸ™‹ Ask for provider support

Model tree for dlab-spp/t0-mt-3b-base

Adapters
1 model

Collection including dlab-spp/t0-mt-3b-base

Paper for dlab-spp/t0-mt-3b-base