Is it جائز to perform السعي in a wheelchair?

Yes, it is جائز to perform السعي in a wheelchair if one is unable to walk. The general principle is that inability to perform an act in its default manner does not remove the obligation — it shifts to what is possible. الشيخ ابن عثيمين stated: 'The one who cannot walk in السعي may ride or be pushed in a wheelchair. السعي is a pillar and must be performed.' The wheelchair user still counts 7 laps between الصفا and المروة. There is no فدية required for performing السعي while seated.