There were seven protests in the men's 4x400 semis.
The meet referee determined Zambia, which passed outside the zone, affected both Team USA and Kenya. So they have decided to do a runoff, likely on Sunday morning Tokyo time, between the USA and Kenya. The winner will go to the final (all eight previously qualified teams will also make it).
Teams will have to use the same legs in the same order. USATF communications has said they even have to run in the same lanes as the semi.
Wild situation.