When the Social Security Administration agreed to a five-year extension of work-from-home arrangements for tens of thousands of employees in early December, many at the agency expressed relief.

But the reprieve may be short-lived. At a news conference two weeks later, President-elect Donald J. Trump railed against the deal and said he would go to court to undo it. “If people don’t come back to work, come back into the office,” he said, “they’re going to be dismissed.”

The back-and-forth previewed what is likely to be one of the earliest points of contention of Mr. Trump’s second administration. Over the past few years, many federal workers have organized their lives around hybrid arrangements that help them juggle work and family responsibilities, and have gone so far as to demand that the Biden administration preserve the status quo. Some have rushed to join the roughly one-quarter to one-third of federal workers who are unionized, so that telework policies will be negotiable.

But to the president-elect and his allies, the work-from-home arrangements are not only a glaring example of liberal permissiveness run amok — “a gift to a union,” Mr. Trump said — but also a tantalizing opportunity to clear the federal government of obstructionist workers and to vastly shrink its reach.

In a Wall Street Journal column in November, Elon Musk and Vivek Ramaswamy, the businessmen tapped to lead Mr. Trump’s government efficiency commission, said they would welcome “a wave of voluntary terminations” triggered by forcing federal employees to work from an office five days a week.

Many private-sector employers have recently announced such policies, arguing that in-person work improves communication, mentoring and collaboration.

The looming collision has heightened the tension across Washington as Mr. Trump heads into his second term. One government employee involved in a union campaign seeking to preserve work-from-home arrangements said union officials worried that, as with the Social Security Administration, press coverage of the effort would put a target on the agency involved and inspire the Trump administration to crack down.

“We are not ready to discuss all of this publicly just yet,” said a representative of the union, the National Treasury Employees Union.

Mr. Trump will not be the first president to chafe at his employees’ attachment to working from home. The Obama administration adopted a policy making it easier for federal employees to work remotely, but it could not envision the scale that would become common during the pandemic. By 2022, President Biden was seeking to dial it back.

Mr. Biden proclaimed in that year’s State of the Union address that “the vast majority of federal workers will once again work in person,” and his administration issued memos laying out a new approach in 2023. Whatever the substantive merits, it surely wasn’t lost on Mr. Biden that Republicans had made a political issue out of “bubble bath bureaucrats” who lounged around their homes at taxpayer expense, as a news release from Senator Joni Ernst, an Iowa Republican, put it.

But change was slow to come. A study of federal buildings found that they were typically under one-third of their prepandemic occupancy in 2023. The White House chief of staff, Jeffrey D. Zients, repeatedly grumbled that “we don’t yet have the return-to-work levels that we should have,” as he said in an April 2024 interview. About 15 to 20 percent of civilian federal workers are based in the Washington area.

Overall, Washington’s weekly occupancy rates were below average for 10 large metro areas last year, outpaced by places including New York and Chicago, according to data from Kastle, the building security firm. (Average occupancy across the 10 areas is still about half the prepandemic level, according to Kastle.)

Part of the explanation may be that Washington is politically liberal, even by the standards of a major American city — Vice President Kamala Harris won more than 90 percent of the vote there against Mr. Trump in November, versus about 82 percent in Manhattan and 77 percent in Chicago. It also skews somewhat young. Polls suggest both characteristics correlate with a preference for working from home.

When the president of the Brookings Institution announced in late October that the Washington-based think tank would require most employees to work from the office at least three days a week beginning in March, younger employees expressed concern that the burden would fall disproportionately on them, since commuting and child care costs could eat up a higher portion of their relatively low salaries.

The consequences will be “felt differently across the employee base,” one research fellow warned the Brookings president, Cecilia Rouse, at a meeting with employees to discuss the change.

“We have four months,” said Dr. Rouse, a former top White House economist under Mr. Biden. “And I sincerely hope that that gives enough time for people to find a way to make that work.” Dr. Rouse noted later in the meeting that employees at the conservative American Enterprise Institute were already expected to go to the office five days a week.

Beyond age and political orientation, the attachment to working from home may reflect the unique sociology of the capital, which is filled with earnest grinders who are passionate about their work and, all things equal, prefer to spend more time on it, not less.

“If I’m mission-driven, why would I want to waste two hours in the car?” said Kenneth Baer, who was a senior official at the Office of Management and Budget under President Barack Obama.

In 2023, after the Justice Department indicated that it would soon require employees to spend two or three days in the office a week on average, up from one, a group of department lawyers wrote to their leadership saying the shift would be self-defeating.

In anonymous testimonials, more than two dozen lawyers expressed enthusiasm for their work — “I love my job” was a common sentiment — and went into exquisite detail about the productivity gains that telework had brought by sparing them long commutes and office banter.

“I can write briefs in approximately 60 percent as much time as when I am in the office,” one lawyer wrote. “The first year of maximum telework was one of the two most productive of my 12 years in the department — and that’s even though I had two children under 4 at home with no reliable child care.”

Several said they had effectively split the work-from-home dividend between themselves and the government: They did more work, but also spent more time tending to children and their mental health. The testimonials align with a survey in mid-2020 by the Stanford economist Nicholas Bloom and two colleagues, who found that the typical office worker saved about 80 minutes a day when working from home, about 40 percent of which was used to do more work. A recent Labor Department study found that industries with higher rates of remote work had larger increases in productivity.

The determination to protect these work-from-home prerogatives has led to a series of standoffs between federal employees and their overseers during the final months of the Biden administration.

Lawyers in the Justice Department divisions that focus on civil rights and the environment sought to unionize last year to help preserve their remote-work arrangements and to protect themselves in case Mr. Trump follows through on his declared intention to revive an executive order that would make it easier to fire civil servants.

The civil rights lawyers had to overcome opposition from their leadership, which initially argued that department lawyers were unable to form a union because of restrictions on workers involved in national security matters, according to Bloomberg Law. They voted last week to unionize.

The Justice Department declined to comment.

Hundreds of employees at the Federal Trade Commission voted in September to unionize, partly because they hoped to protect their work-from-home arrangements under future administrations. But after quickly recognizing the union, the agency’s chair, Lina Khan, let months pass before engaging with it, according to a labor source familiar with the negotiation. Contract negotiations began in earnest only this week, according to the source, amid pressure from labor leaders and friendly politicians.

A person briefed on Ms. Khan’s thinking said that the agency received a concrete contract proposal only in mid-December and that it had to digest the details while filing cases and making orders final before the administration ended.

Still, it is unclear how much the push by employees will help them. Mr. Trump’s choice to lead the Office of Management and Budget has said allies of the new administration hope that bureaucrats will “not want to go to work because they are increasingly viewed as the villains” and that they will be “traumatically affected.”

Donald Kettl, an emeritus professor at the University of Maryland who is an expert on the civil service, said that while federal employees’ efforts to retain their working conditions through unionizing and negotiating new contracts carried some weight in principle, he expected the Trump administration to disregard them in many cases.

“Anything that’s not enshrined in the law, I think they’ll want to challenge,” Dr. Kettl said, referring to civil service protections. “And if it is enshrined in the law, I think they’ll go after that as well.”