Mayor Mamdani spiked the ball Tuesday, as the city’s budget crunch seemed to go away as quickly as it had appeared.

He announced that Gov. Kathy Hochul and state lawmakers would dallop a few extra billion dollars on Gotham over the next few years to patch up the city’s suddenly balanced budget.

But the mayor’s revisionism, coupled with the slipshod manner in which the budget is being balanced, gives reason to worry that he will struggle to handle less avoidable fiscal challenges ahead.

The mayor insists he “uncovered” a massive budget deficit upon taking office, a strange term to describe something that had been warned about for the better part of a year, including by state comptroller Tom DiNapoli.

New York City is now in its fourth year of spending more than it collects, and spending has far outpaced inflation for a decade.

So instead of taking a scalpel to city agencies, the mayor took the train to Albany.

Mamdani, to his credit, accepted lawmakers’ offer to scale back or at least postpone a state edict, albeit one he supported, that’s driving some of city’s budget agita: a “class-size” mandate enacted at the teachers’ unions’ behest, despite plummeting enrollment.

Usually, cash-strapped mayors look for efficiencies by reforming or ending underperforming programs or freezing new hires. But that would be “austerity.”

But Mamdani’s still accepting the false premise that we need more teachers, and he’s counting on state taxpayers to pick up part of the cost in coming years.

If anything, the DOE needs consolidation — as our colleague Danyela Souza Egorov argued this week — rather than funding failing schools with declining enrollment.

An estimated 134 city-run schools expect to have fewer than 150 students come autumn.

About $850 million in hoped-for savings will come from claiming revenues the city is owed, managing overtime, and “improving the efficiency of public services.”

That’s easier said than done.

What happens when those collections don’t materialize, or when the city needs more police shifts?

The biggest chunk of “savings” is even less defensible.

Mamdani has reportedly gotten the governor and state lawmakers to agree to change the way New York City’s under-funded public pension plans pay off debt they incurred a generation ago by making overly rosy assumptions about how their investments would perform.

The city wants to reduce those debt payments and instead pay it off over a longer period, likely well into the 2040s — meaning tomorrow’s workers will be taxed extra to pay for city services delivered before some of their parents were born.

This is a one-time fix, if you can call it that, which the governor and the mayor are turning to outside of a recession or emergency.

Don’t forget: A chunk of the city’s budget gap disappeared in part because tax receipts, including those from Wall Street bonuses, came in higher than expected.

What Mamdani is hailing as a triumph for democratic socialism amounts to a state bailout standing on a pension gimmick wearing a trenchcoat.

Hochul has given him billions in direct funding, plus her blessing to punt costs almost a whole generation into the future.

He’s positioning the city for an even higher expense structure in later years — without a plan for paying for it.

But he’s not going to be able to lean on the governor forever.

The state’s tax revenues are even more volatile than those of the city, because its tax code is even more dependent on the fluctuating incomes of high-earners and corporations.

And the city’s ability to count on revenues from those sources could be threatened by the mayor’s affinity for making videos about them.

Pension gimmicks and temporary fixes are no substitutes for the sort of spending prioritization that comes from proper management.

Mamdani appears largely unwilling to confront what’s causing the city’s costs to spiral out of control.

If he waits until it’s too late, he won’t just have to talk about austerity — he’ll have to show it in practice.

Ken Girardin and John Ketcham are fellows at the Manhattan Institute.