ElasticTTT: Prior-Preserving Test-Time Tuning for Video Editing

Test-Time Tuning (TTT) on pretrained diffusion models has emerged as a powerful paradigm for video editing. However, there exists a foundational mismatch between the distribution-mapping nature of generative models and the single-point optimization of standard TTT. In this paper, we demonstrate that this mismatch triggers textitPrior Collapse, a degenerate state where the model discards the text conditions and spatial latents, collapsing generations to the source video, or entangling the features of distinct regions. To resolve this, we propose ElasticTTT, a novel framework that preserves the prior generative distribution and rescues generative elasticity. Specifically, we propose textitTarget Distribution Regularization to prevent sharp memorization minima, textitContrastive CFG to guide inference away from source biases, and textitAsynchronous Noise Schedule to preserve unedited regions. Extensive evaluations, supported by theoretical analysis, demonstrate that ElasticTTT successfully preserves the generative prior of the base model, achieving state-of-the-art performance on one-shot video editing.