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MARS-Retokenization/olmo2-7b-instruct-inv-reference-mixed-ce-exposure

sourceHugging Faceapache-2.0updated 13d agoView on Hugging Face

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invreferencemixedceexposure

Research checkpoint from a study of tokenization (reader) invariance and its effect on robustness to adversarial re-tokenization. Fine-tuned from allenai/OLMo-2-1124-7B-Instruct.

These are research artifacts, not products. Numbers below are measured on a 200-prompt AdvBench holdout that was excluded from training by construction.

Measured

metric	value
AdvTok ASR (t=1)	0.314
AdvTok canonical ASR (t=1)	0.194
AdvTok ASR (greedy)	0.17
AdvTok canonical ASR (greedy)	0.045
XSTest over-refusal (safe)	0.081
XSTest refusal (unsafe)	0.818
margin_spread	0.843
Alpaca token F1	0.418

AdvTok ASR is attack success rate under adversarial tokenization (Geh et al., arXiv:2503.02174), Llama-Guard-3-8B judged, greedy decoding. XSTest over-refusal is the refusal rate on safe prompts — the cost side.

Training configuration

field	value
`mode`	`reference`
`objective`	`ce_exposure`
`ce_weighting`	`uniform`
`ema_beta`	`None`
`harmful_mix`	`mixed`
`harmful_fraction`	`0.286`
`num_encodings`	`8`
`cvar_quantile`	`0.25`
`max_steps`	`700`
`learning_rate`	`1e-05`
`grad_accum`	`8`
`seed`	`42`
`reference_model`	`allenai/OLMo-2-1124-7B-Instruct`
`max_new_tokens`	`128`
`prefix_tokens`	`8`

Parameter drift from base (training-happened guard)

group	relative L2
attn	0.01197
embed_tokens	0.00098
lm_head	0.00928
mlp	0.01291
norm	0.00099

Caveats

—Single seed. No claim of significance across seeds.
—Evaluated on English AdvBench/XSTest/Alpaca only.
—The safety numbers are for the specific attack studied; they do not imply robustness to other jailbreaks.