Hull City 2 West Ham 2: Debutants star in KC drama
Hull manager Steve Bruce thrust record signing Abel Hernandez straight into his first XI and the Uruguay international put work-permit issues behind him by crashing in a header six minutes before the break.
Ecuador forward Enner Valencia, making his first West Ham start, levelled in the 50th minute with a blistering long-range effort before Mohamed Diame - a fortnight after leaving Upton Park - restored the home side's advantage.
Diafra Sakho, like Valencia starting a West Ham match for the first time, capped a busy display with a shot that deflected home off Curtis Davies to save Sam Allardyce's men from a third loss in four league outings.
Diame joined Hernandez in making his Hull debut as Bruce reverted to a midfield diamond.
Valencia and Sakho started either side of Mauro Zarate in a three-pronged West Ham attack, while Guy Demel was preferred to Joey O'Brien at right-back.
Stewart Downing lashed past the near post from just inside the box with half an hour played and the West Ham midfielder's cross five minutes later resulted in a brilliant save by Allan McGregor from the game's first clear opening.
Valencia leapt to nod back across to Sakho, who diverted goalwards only for the Hull goalkeeper to instinctively flick out a hand to deny him.
Hernandez then thundered a shot into Adrian's arms at the other end and capped a frantic spell by opening the scoring in the 37th minute - getting in front of James Tomkins to thud home from Ahmed Elmohamady's wonderfully whipped cross.
Hull thought they had doubled their advantage a minute before the break but Nikica Jelavic was offside as Hernandez's effort cannoned back off the crossbar for him to convert.
West Ham levelled in magnificent fashion five minutes into the second period.
There appeared to be little on as Valencia checked a run inside from the left flank, but he engineered a slither of space to the left of Michael Dawson and unleashed a 25-yard thunderbolt into the top corner.
It appeared Valencia and Hernandez were locked in a bid to outdo one another when the latter displayed exquisite chest control on the edge of the box to arrow a left-footed volley that had Adrian at full-stretch.
Jelavic snatched at an opportunity from similar range with an hour played but Diame stylishly restored Hull's advantage in the 64th minute.
Aaron Cresswell's cross-field throw-in for Cheikhou Kouyate was incredibly ill-advised but Diame showed superb composure after striding forward to intercept, mesmerising Tomkins with a couple of stepovers before side-footing home.
The lead lasted just three minutes and it was Hull's turn to produce sub-standard defending, allowing Sakho space to arrow across goal and see the ball squirm through McGregor before crossing the line via the unfortunate Davies.
A wrong-footed McGregor was relieved to see Mark Noble's speculative 72nd-minute drive deflected wide and the Scotland international sharply kept out a looping Sakho header three minutes later.
Adrian kept out another rasping strike from Hull substitute Robbie Brady but City's wait for a first win since the opening day goes on - indeed, they almost departed with nothing to show for their efforts when Valencia's header from a raking Downing cross was diverted onto the crossbar by Dawson deep into stoppage time.