Test-time adaptation(TTA) aims to stably adapt a trained model without labels to maintain generalization performance on unseen data distributions. However, existing TTA methods are designed to trust predictions that are not guaranteed to be ground-tru...
Test-time adaptation(TTA) aims to stably adapt a trained model without labels to maintain generalization performance on unseen data distributions. However, existing TTA methods are designed to trust predictions that are not guaranteed to be ground-truth labels, accumulating errors that use the model's own misjudgments as adaptation signals. We attribute this instability to the failure to distinguish causal features from non-causal nuisance factors during adaptation. The proposed method decomposes features into content and style, adapts only content features under a causal model, and guarantees identifiability through label sufficiency, domain invariance, content-style de-correlation, and information compression. During testing, the model selectively performs Bayesian updates only to content features, while style features remain fixed. We further employ a calibration-aware control mechanism that regulates update strength to prevent model drift. Experimental results on classification and segmentation tasks show that the proposed method provides consistent improvements over existing TTA methods in terms of both predictive performance and calibration robustness. This study demonstrates that selective Bayesian adaptation via causal feature decomposition at test time enables stable and reliable model adaptation under distribution shifts.