Town went down to a first defeat of the season in a thriller at Portman Road.
Brighton were two goals up inside the first 12 minutes through Kazenga LuaLua and Dale Stephens.
Blues rallied after the break and Freddie Sears and David McGoldrick - from the penalty spot - chalked up their third goal of the season each to level things up but Tomer Hemed’s header won it for the Seagulls to take them to the top of the Championship table.
New signing Piotr Malarczyk started on the bench for Town after the paperwork was completed on a two year deal.
Josh Emmanuel retained the right-back spot, with Brett Pitman partnering Sears in attack.
Dean Gerken had to be alert to deny LuaLua putting Brighton ahead on five minutes, but the Town ‘keeper couldn’t prevent the winger finding the net soon after with an excellent finish from Gaetan Bong’s incisive pass.
Blues were rocked again on 12 minutes, Stephens’ free-kick from 35 yards evading everyone and going into the corner of the net.
Uwe Hunemeier managed to block Pitman’s pass as he looked to get Sears through on goal, former Town loanee Liam Rosenior dragging his shot wide at the other end as Blues failed to clear.
Pitman was inches away from getting on the end of Sears’ cross as Town looked to get a foothold in the game.
Brighton should have been three up though midway through the half, Bong again the provider with a deft ball over the top to send Sam Baldock in but he poked his shot wide of the far post.
Sears did well to backtrack and rob LuaLua as Brighton continued to look dangerous on the counter, the Town striker then firing just wide from a well worked free-kick after Hunemeier fouled Ryan Fraser, the Seagulls defender perhaps fortunate not to pick up a second yellow card for the challenge.
Pitman couldn’t get his head on Fraser’s free-kick, Bruno failing to hit the target from the edge of the box as the visitors went into the break two goals to the good.
Mick McCarthy made a double change at the break with Malarczyk and McGoldrick on for Emmanuel and Ainsley Maitland-Niles, while Lewis Dunk replaced Hunemeier for Brighton.
Sears’ driving run saw the Seagulls flustered and McGoldrick’s shot from the angle was deflected wide but it was Brighton who were a coat of paint away from adding to the scoreline, Stephens hitting the post from the edge of the box.
Town had a strong claim for a penalty when Dunk appeared to handle the ball in the box, then Malarczyk put the ball in the net but not before the offside flag was raised.
Blues got the rewards the early second-half play threatened nine minutes after the break, Pitman’s shot hitting the inside of the post and bouncing back to Sears who made no mistake from a few yards out.
Baldock fired wide as the Seagulls looked to re-establish their advantage, Jonas Knudsen doing superbly to block Stephens’ effort, Rosenior curling a left footer wide.
Berem Kayal fizzed a 25 yarder over, then Town were awarded a penalty just past the hour, Bruno judged to have fouled Fraser and McGoldrick sent his spot-kick into the bottom corner.
Luke Chambers produced a brilliant tackle to stop Hemed putting Brighton in front but the striker did just that four minutes after Town had levelled, getting his head on LuaLua’s cross.
Giles Coke replaced Cole Skuse in Town’s final change, former Town loanee David Stockdale beating out Pitman’s cross at full stretch as both sides continued to look likely to add to the scoreline.
Stephens, a real danger for Brighton from a midfield, saw another shot deflected for a corner, Tommy Smith in the right place to clear off the line from Hemed’s header.
Bobby Zamora replaced Hemed for the last 15 minutes, Coke sending a long ranger over the bar, Fraser’s right footer a yard wide.
Gerken saved from Rosenior after another Seagulls’ counter, then Stockdale held firm from Sears’ wicked cross as Chris Hughton’s side held on to replace Blues at the top of the table.