Riyad Mahrez's late penalty miss denied Manchester City a stirring comeback victory that would have all but wrapped up the Premier League title. Instead the champions had to be content with just a point-sized step closer to retaining the trophy - and the knowledge it could have been far worse.
The Algerian saw his spot-kick saved after City had recovered from the excellent Jarrod Bowen firing West Ham into a shock 2-0 lead.
A Jack Grealish reply and Vladimir Coufal's own goal wiped that out but home goalkeeper Lukasz Fabianski refused to be beaten again.
The point moved City four ahead of Liverpool, who cash in their game in hand at Southampton tomorrow. A Liverpool loss would seal the deal there and then for Pep and Co but it is likely that both sides will kick off on Sunday - City host Aston Villa, Liverpool go to Wolves - with instructions to win at all costs.
Ten years after Agueroooo, it is all go once again on the final day for City.
Guardiola, who said he would probably tune in tomorrow if he hasn't anything better to do, was clearly not expecting Saints get the better of Jurgen Klopp's quad chasers, who added the FA Cup on Saturday to the League Cup they had won earlier.
"Now there is no debate, no goal difference or anything," he said. "It is just win - and if we don't Liverpool will be champions. After many years here it is an incredible privilege to have the chance to win it in front of our people."
City appeared serenely secure until West Ham's vigorous counter-attacking twice exposed their defensive frailties before the break.
Fernando and Aymeric Laporte had passed fitness tests to form a makeshift central defensive pairing but added to Oleksandr Zinchenko on the left it resulted in carnage.
Bowen used his pace and guile to net both goals, in the 24th minute and the 45th, from moves that began with Fabianski.
The first saw Laporte play Bowen onside as he motored past Zinchenko, rounded Ederson and found the net from a tight angle.
Zinchenko was the fall guy for the second by standing and watching yet again as Bowen chased Michail Antonio's loft over the centre-backs. This time the forward, already on the fringe of the England squad, elected to lash a shot from the edge of the box that went through Fernandinho and into the far corner.
City hit back three minutes into the second period, after having received a few Pep pointers in the interval. West Ham failed to deal with a high ball in the box and Grealish lashed in a downwards drive that flicked off Craig Dawson.
The champions turned the screw straight away. Bernardo Silva was denied by a smart Fabianski block after Grealish had flicked the ball back from beyond the back post. Just like the first 20 minutes, the Hammers were finding it difficult to get out of their own half.
Fabianski was booked for time-wasting before the hour-mark had even been reached, just after Kevin de Bruyne had lashed a free-kick just over.
Another Zinchenko error let Bowen in again however, although this time he could only find the side-netting. Not long afterwards it was Fernandinho who dropped a clanger with a back pass straight to Antonio - whose chip over Ederson fell the wrong side of the post. City were attacking like champs yet still defending like chumps.
The leveller came the 69th minute from a free-kick that Coufal dived to head away but succeeded only in steering it past his own goalkeeper.
Bowen had not given up on claiming the match ball however but saw his shot bounce off Laporte and drop wide before captain and 18-year servant Mark Noble came on for a farewell appearance in front of the home fans.
The came Dawson's fateful challenge on Gabriel Jesus. Referee Anthony Taylor did not initially realise it had been man not ball but a trip to the VAR monitor confirmed otherwise - and Fabianski guessed correctly to bat away Mahrez's penalty.
West Ham face an exciting last day themselves, having to win and hope Manchester United don't to pip them for a Europa League spot. Otherwise its the Conference instead.
Thousands of Hammers stayed behind to pay tribute to Noble and applaud the achievements of a team that reached the Europa League semis. Manager David Moyes said: "I'm hoping we can build again. I wanted to challenge a lot of the top teams, which we hadn't done, and we had a pretty good go at it."
Fabianski 7; Coufal 5, Dawson 6, Zouma 7, Cresswell 6; Soucek 7, Rice 7; Bowen 8, Lanzini 5 (Noble 77, 6), Fornals 6 (Johnson 90, 3); Antonio 7 (Yarmolenko 90, 2).
Areola, Vlasic, Fredericks, Masuaku, Kral, Oko-Flex.
Ederson 5; Cancelo 7, Fernandinho 4, Laporte 5, Zinchenko 4; Silva 7, Rodri 6, De Bruyne 7; Mahrez 6, Jesus 6, Grealish 7.
Steffen, Ake, Sterling, Gundogan, Foden, Egan-Riley, Mbete, Palmer, Lavia.
Anthony Taylor 6.