City were defeated in the dying minutes as a late comeback saw Cambridge United record a 2-1 victory.
Having taken the lead in the first half, the U's struck two goals in the final 10 minutes to condemn Stuart McCall's side to their first defeat in three matches.
After a bright start, it was the Bantams who struck first, in the 17th minute.
Good work from Lee Novak down the right channel saw the ball eventually fall for Jake Reeves on the edge of the area who - with the aid of a deflection - notched his first City goal.
McCall’s men continued applying pressure throughout the early stages, with efforts from Novak and Shay McCartan.
The hosts grew towards the end of the opening period, though, with both Paul Mullin and Paul Lewis drawing smart stops from Richard O’Donnell in quick succession.
The second period began another competitive battle, with United’s Leon Davies bending just over in the 53rd minute.
Cambridge piled on the pressure as the half wore on, though the Bantams again went close in the 75th minute when Lee Novak's effort was stopped by the legs of Callum Burton.
Increased U's pressure eventually told, though, in the 84th minute, when the ball fell for Harry Darling who struck in the City area to equalise.
Mark Bonner's men went closer still in the dying stages as substitute Idris El Mizuoni's spectucular effort rattled the crossbar.
The hosts then snatched all three points in added time when a goalmouth scramble led to substitute Harvey Knibbs directing an effort past Richard O'Donnell to break Bantam hearts.
CITY: Richard O’Donnell; Adam Henley, Anthony O’Connor, Ben Richards-Everton, Connor Wood; Dylan Mottley-Henry, Jake Reeves, Hope Akpan (Harry Pritchard 79', booked 90+5'), Glenn Middleton (Dylan Connolly 70'); Lee Novak, Shay McCartan (Paudie O’Connor 66'). Subs (not used): Luke McGee (GK), Chris Taylor, Zeli Ismail, Clayton Donaldson.
GOALS: Reeves (17').
CAMBRIDGE: Callum Burton; Kyle Knoyle (Idris El Mizouni 81'), Greg Taylor (c), Harry Darling, Harrison Dunk; Leon Davies, Paul Lewis, Liam O’Neil (Samir Carruthers 72'), George Maris; Paul Mullin, Victor Adeboyejo (Harvey Knibbs 72'). Subs (not used): Dimitar Mitov (GK), George Taft, Andrew Dallas, Reggie Lambe.
GOALS: Darling (84'), Knibbs (90+1').
ATTENDANCE: 4,541 (801 visitors).
REFEREE: Nicholas Kinseley (Essex).