La Gazzetta dello Sport reports the contract trigger mechanism, which was written into Allegri's deal when he was re-appointed at the start of the season, as the clearest sign of the club's genuine belief in the manager despite a difficult second half of the campaign.
There is no break clause on either side, and owner Gerry Cardinale's intention is to use the salary increase as a direct statement of confidence in Allegri's centrality to the project.
AC Milan currently sit third in Serie A, level on points with Roma in fourth and two ahead of Como in fifth. A win against Cagliari would confirm a top-four finish regardless of other results. Failure to win could see them drop out of the Champions League positions entirely if Roma and Como both take maximum points from their respective fixtures.
Allegri spoke at length about the club's internal priorities after the 2-1 win at Genoa that kept Milan's fate in their own hands.
"Milan is first and foremost. The club comes above everyone and everything. We are all just passing through."
Cardinale was present at the Marassi and praised the team publicly after the match. His presence and subsequent comments were interpreted within the club as a sign that the American owner has no intention of making a managerial change, regardless of what happens to other elements of the leadership structure.
Allegri expects to be backed in the market if Champions League football is confirmed, with the club understood to be targeting at minimum two additions in central defence and one in attack ahead of the new season. He views the achievement of a top-four finish, given the circumstances of a highly competitive final stretch, as a foundation rather than a ceiling for what the squad can achieve next year.