Mayor Zohran Mamdani boasted Tuesday that he plugged the city’s multibillion-dollar budget gap for the coming fiscal year — but it’s only “balanced” with gimmicks that guarantee oceans more red ink in the years ahead.

With a late assist from Gov. Kathy Hochul’s own flim-flammery, the new, $124.7 billion Mamdani spending plan relies on one-time cash infusions, postponed payments and dubious calculations of future tax windfalls and theoretical savings.

The day began with Hochul boldly announcing yet another of her trademark cave-ins: After weeks of insisting she’d given the mayor as much help as she could, the gov magically found another $4 billion for him just hours before he presented his plan.

Yet half the windfall comes down to new debt, much of the rest is pretty vaporous — and all of it amounts to just telling the spending addict he can keep on shooting up.

The mayor’s plan, warns city Comptroller Mark Levine, “relies on $2.8 billion in one-time measures” and short-term savings, without addressing “the fact that City government continues to spend more than we take in, even in a year of record revenues.”

Record revenues, but not enough for Zoh.

State Comptroller Tom DiNapoli likewise warned that the “fiscal stresses” built into this budget will “require proactive steps to achieve budget balance” in coming years.

Hochul’s $4 billion line of credit, in other words, will simply let Mamdani spend more now, and worry later about paying it off.

The hard revenues here center on the still-not-finalized pied-à-terre tax surcharge, which not only has negative side effects like depressing property values and pushing high earners to move away, but also likely won’t bring in the in $500 million a year that Hochul and Mamdani claim.

Levine, the green-eyeshades guy, pegs the take at as little as $340 million.

Hochul’s “gifts” also includes an OK to delay $2.3 billion in payments to fully fund the city pension funds.

That “gimmick,” warns Citizens Budget Commission President Andrew Rein, simply forces “future New Yorkers to pay our bills” (though he credits the gov for holding “the line on personal income and business taxes”).

One true positive in Hochul’s package: Getting the Legislature’s agreement to let the class-size law phase in more slowly, saving the city $500 million this year.

But that will still force City Hall to hire more teachers and build more schools even as enrollments keep dropping and many schools are half empty: It’s a mandate for waste, pure and simple.

Yet of all the fibs Mamdani spewed Tuesday in presenting his plan, perhaps the worst was his claim that it lays “the ground work for long-term stability and fiscal health.”

Hel-lo: The plan leaves a whopping $25 billion cumulative cash shortfall for fiscal years 2028-30, even if the economy doesn’t hit a bump.

One ironic bit of honesty: The mayor bragged about how he opposes “austerity” — Stop the presses!