  Topology provides an essential concept for achieving unchanged (or protected)
quantum properties in the presence of perturbations. A challenge facing
realistic applications is that the level of protection displayed in real
systems is subject to substantial variations. Some key differences stem from
mechanisms influencing the reconstruction behaviors of extended dissipationless
modes. Despite various insightful results on potential causes of
backscattering, the edge-state-based approach is limited because the bulk
states, as shown by breakdown tests, contribute indispensably. This study
investigates the influence of bulk reconstruction where dissipationless modes
are global objects instead of being restricted to the sample edge. An integer
quantum Hall effect (IQHE) hosted in a Corbino sample geometry is adopted and
brought continuously to the verge of a breakdown. A detection technique is
developed to include two independent setups capable of simultaneously capturing
the onset of dissipation in both longitudinal and transverse directions. The
real-time correspondence between orthogonal results confirms two facts. 1.
Dissipationless charge modes undergo frequent reconstruction in response to
electrochemical potential changes, causing dissipationless current paths to
expand transversely into the bulk while preserving chirality. A breakdown only
occurs when a backscattering emerges between reconfigured dissipationless
current paths bridging opposite edge contacts. 2. Impurity screening is vital
in enhancing protection, and topological protection is subject to an intriguing
interplay of disorder, electron-electron interaction, and topology. The
proposed reconstruction mechanism qualitatively explains the robustness
variations, beneficial for developing means for optimization.
