arXiv:2610.30734v1 Announce Type: new Abstract: Digitally mediated attachment is increasingly common, yet the mechanisms of symbolic closure in hybrid physical--digital relationships remain underexplored. We address an XR design question: how different mediated farewell formats relate to perceived symbolic closure, spatial presence, and bereavement-related emotional intensity. Using "cloud petting" as a controlled proxy of digitally mediated attachment, we compare three farewell formats: (1) lightweight social messaging, (2) a revisitable web memorial, and (3) immersive VR ritual participation. These formats differ in symbolic participation, spatial presence, and sensorimotor ritual enactment. In a mixed-methods study ($N=45$), Website and VR showed significantly higher perceived symbolic closure than Messaging, while the present sample did not detect a significant closure advantage for VR over Website. VR was also associated with significantly stronger grief-related responses on the Pet Bereavement Questionnaire, whereas negative-affect change measured by the Positive and Negative Affect Schedule did not differ significantly across modalities. This pattern motivates a preliminary, exploratory, mechanism-level Agency-Amplification account: formats supporting structured farewell participation were associated with higher perceived closure, whereas the VR format, combining technical immersion, spatial presence, and sensorimotor ritual enactment, was associated with stronger loss-oriented emotional processing. Because the formats also bundled differences in participation, revisitation, technical immersion, and spatial presence, the study provides preliminary design guidance without isolating the causal contribution of any single feature.