We investigate a many-body extended Aubry-André-Harper model and find that the many-body critical phase becomes ergodic when the boundary condition is changed from open to periodic in finite systems. The resulting ergodic phase satisfies the eigenstate thermalization hypothesis and loses memory of initial states after long-time evolution. By independently tuning boundary hoppings and interactions, we identify the hopping suppression as the key microscopic mechanism underlying this behavior. More importantly, we find that when multiple zero-amplitude hoppings remain effectively operative, the many-body critical phase persists even as the interaction strength increases. In contrast, disrupting these zero-amplitude hoppings strongly destabilizes criticality and promotes thermalization. These results establish zero-amplitude hoppings as an important microscopic ingredient governing the stability of many-body criticality.

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• Anderson localization
• Critical phenomena
• Many-body localization
• Exact diagonalization