Limits of Convergence-Rate Control for Open-Weight Safety

Fuente: arXiv
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Auteurs principaux: Rosati, Domenic, Zeng, Xijie, Huang, Hong, Dionicio, Sebastian, Majumdar, Subhabrata, Rudzicz, Frank, Sajjad, Hassan
Format: Preprint
Publié: 2026
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author Rosati, Domenic
Zeng, Xijie
Huang, Hong
Dionicio, Sebastian
Majumdar, Subhabrata
Rudzicz, Frank
Sajjad, Hassan
author_facet Rosati, Domenic
Zeng, Xijie
Huang, Hong
Dionicio, Sebastian
Majumdar, Subhabrata
Rudzicz, Frank
Sajjad, Hassan
contents Open-weight foundation models can be fine-tuned for harmful purposes after release, yet no existing training resistance methods provide theoretical guarantees. Treating these interventions as convergence-rate control problems allows us to connect optimization speed to the spectral structure of model weights. We leverage this insight to develop a novel understanding of convergence rate control through spectral reparameterization and derive an algorithm, SpecDef, that can both provably and empirically slow first- and second-order optimization in non-adversarial settings. In adversarial settings, we establish a fundamental limit on a broad class of convergence rate control methods including our own: an attacker with sufficient knowledge can restore fast convergence at a linear increase in model size. In order to overcome this limitation, future works will need to investigate methods that are not equivalent to controlling convergence rate.
format Preprint
id arxiv_https___arxiv_org_abs_2602_18868
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Limits of Convergence-Rate Control for Open-Weight Safety
Rosati, Domenic
Zeng, Xijie
Huang, Hong
Dionicio, Sebastian
Majumdar, Subhabrata
Rudzicz, Frank
Sajjad, Hassan
Optimization and Control
Machine Learning
Open-weight foundation models can be fine-tuned for harmful purposes after release, yet no existing training resistance methods provide theoretical guarantees. Treating these interventions as convergence-rate control problems allows us to connect optimization speed to the spectral structure of model weights. We leverage this insight to develop a novel understanding of convergence rate control through spectral reparameterization and derive an algorithm, SpecDef, that can both provably and empirically slow first- and second-order optimization in non-adversarial settings. In adversarial settings, we establish a fundamental limit on a broad class of convergence rate control methods including our own: an attacker with sufficient knowledge can restore fast convergence at a linear increase in model size. In order to overcome this limitation, future works will need to investigate methods that are not equivalent to controlling convergence rate.
title Limits of Convergence-Rate Control for Open-Weight Safety
topic Optimization and Control
Machine Learning
url https://arxiv.org/abs/2602.18868