City came from 2-0 down to snatch a point on a breathless afternoon in BS3.
Visitors Milton Keynes Dons took the lead through Shaun Williams’ 16th minute opener having survived an early flurry of City chances.
Then Ben Reeves doubled the lead with a neat finish, leaving the Robins with a daunting half-time deficit.
But Dons old boy Sam Baldock, guilty of three first-half misses, had the last laugh with a clinical finish and a scruffy one to salvage a draw.
On another day it might have finished 7-7.
Steve Cotterill handed a City debut to former Brighton & Hove Albion defender Adam El-Abd, while Simon Gillett returned in midfield.
Scott Wagstaff and Greg Cunningham were recalled in the wing-back positions at the expense of Brendan Moloney and Joe Bryan, who started the midweek FA Cup defeat at Watford.
Just like at Vicarage Road, it would take just two minutes for City to create a first clear chance, as Wagstaff latched on to a ball over the top only to run into the advancing Dons keeper David Martin.
When the ball broke kindly for 18-goal striker Jay Emmanuel-Thomas the opening goal looked inevitable, but his tame shot was cleared by covering defender Antony Kay with relative ease.
It was to trigger a whirlwind start from the hosts, who could feasibly have led 3-0 by the six minute mark, as Baldock squandered two further opportunities to break the deadlock.
First Wagstaff ran into space down the right flank and produced a perfect cross on to the head of the former Dons marksman, but with Martin stranded Baldock somehow put the chance wide of the near post, venting his frustration on the advertising board in front of the East End.
Then the City skipper beat the offside trap to bear down on goal but saw his shot saved by the right foot of Martin.
It was hard not to fear the curse of spurned opportunities, and ten minutes later the visitors smelled blood and duly snatched a goal completely against the run of play.
Ben Reeves’ diagonal clip into the box caught out El-Abd, allowing defender Williams to ghost in, take the ball on his chest and tuck it neatly past Elliott Parish.
The response was swift but not rewarded, as Emmanuel-Thomas fed the marauding Cunningham, who burst into the box but shot against the legs of Martin.
City were relentless. Another Emmanuel-Thomas through pass had a red shirt running into yards of space with only Martin to beat, but this time the hapless Baldock opted for power and drove the ball straight at his former team-mate.
How the Dons’ clean sheet remained intact was anybody’s guess, but the visitors were not about to try and tighten up defensively – they sensed further goals at the other end.
They were right to. Kay was rolled in by lively winger Samir Carruthers but denied by the legs of the sprawling Parish, who made a very good save to force a corner.
From the resulting kick, captain Dean Lewington was left completely unopposed on the six-yard line and contrived to send his header over the top. It was a remarkable chance.
But the Dons kept coming and proved more clinical than their generous hosts, as another precise Carruthers pass released Reeves, who calmly beat Parish with a chipped finish just inside the near post.
Eventually respite prevailed in the form of the half-time whistle, prompting Cotterill to sacrifice Karleigh Osborne and bring on Derrick Williams in a bid to add balance to the back three of right footers who started the game.
But having finished the first period the stronger, the Dons remained a threat. Striker Chris Long easily turned Aden Flint and raced clear on goal. Parish, who was having a decent game, stood firm to repel the danger.
However, City were thrown a lifeline thanks to a slice of luck out of nothing. What seemed a regulation clearance from the visitors caused them a problem when it struck the back of another white shirt, sending Baldock through again.
As Martin inexplicably opted to stay back, the striker waited for the ball to drop and slammed a half-volley high into the net. It was the most difficult chance he had been presented with all afternoon.
City were pressing for the equaliser but without the same level of goalmouth action as in evidence before the break.
At the other end, Reeves’ inventive cross with the outside of his boot looked to have carved out an opening for substitute Dean Bowditch, who could only shoot over the crossbar at the second attempt.
Then Bobby Reid’s deep cross was headed down and back across goal by Cunningham but well cleared by Kay.
With 15 minutes left Cotterill threw his last hand, bringing on attacking duo Tyrone Barnett and Wes Burns for Emmanuel-Thomas and Reid.
It was a move which paid immediate dividends, as Marlon Pack’s corner was met by Barnett, whose first touch was a glancing header for Baldock to smuggle the ball over the line from close range.
City were in no mood for settle for a point, but their gung-ho approach was in danger of costing them at the other end.
Long beat Flint and squeezed a shot beyond Parish from the tightest of angles, but Williams was sweeping up in just the right spot.
Then Flint connected with a header towards his own goal which only just eluded the crossbar before Bowditch found space only to slice his shot wide as the ball sat up to be hit.
It was breathless stuff. Baldock could not make a strong enough connection on Burns’ cutback to complete a dramatic hat-trick, while Parish somehow got enough behind a Williams piledriver to preserve parity.