Even as the Trump administration continues to slash federal jobs, a number of federal agencies have begun to reverse course — reinstating some workers and pausing plans to dismiss others, sometimes within days of the firings.

The Office of Personnel Management on Tuesday revised earlier guidance calling for probationary workers to be terminated, adding a disclaimer that agencies would have the final authority over personnel actions. It is unclear how many more workers could be reinstated as a result.

Here’s a look at some of the back-and-forths so far:

Rehiring Some Essential Workers

Trump-appointed officials fired, then scrambled to rehire some employees in critical jobs in health and national security.

Workers reviewing food safety and medical devices

Around Feb. 15 The Food and Drug Administration fired about 700 probationary employees, many of whom were not paid through taxpayer money.

Workers involved in bird flu response

Around Feb. 14 The Department of Agriculture continued plans to fire thousands of employees, including hundreds in a plant and animal inspection program.

Days later The agency said it was trying to reverse the firings of some employees involved in responding to the nation’s growing bird flu outbreak.

Workers who maintain the U.S. nuclear arsenal

Feb. 13 The Energy Department began laying off 1,000 of its probationary employees, including more than 300 who worked at the National Nuclear Security Administration, which maintains and secures the country’s nuclear warheads. A spokesperson for the Energy Department disputed that number, saying fewer than 50 at the N.N.S.A. were fired.

Rehired After Political Pushback

Public opposition from both Democrats and Republicans has also resulted in some fired workers getting called back.

Workers managing a 9/11 survivors’ health program

Around Feb. 15 The Centers for Disease Control and Prevention cut hundreds of employees, including 16 probationary workers who manage the World Trade Central Health Program, which administers aid to people who were exposed to hazards from the terrorist attacks on Sept. 11, 2001.

Several days later After bipartisan pushback, the Trump administration said that fired employees would return to their jobs.

Scientific researchers, including military veterans

Feb. 18 The National Science Foundation fired 168 employees, or roughly 10 percent of its work force.

Less than two weeks later The foundation began reversing dismissals of 84 probationary employees, in response to a ruling by a federal judge and guidance from the Office of Personnel Management to retain the employment of military veterans and military spouses.

Temporary Reinstatements and Pauses on Firings

The firing spree has prompted a slew of lawsuits, which in some cases have resulted in temporary reversals.

Employees at a federal financial watchdog

Feb. 11 Officials fired almost 200 employees at the Consumer Financial Protection Bureau, a financial industry watchdog, and ordered the rest to stop their work.

Employees at an international aid department

A day later A federal judge ordered the Trump administration to temporarily halt the layoffs.

Two weeks later The judge ruled that the administration could proceed with plans to lay off or put on paid leave many agency employees. U.S.A.I.D. moved to fire around 2,000 U.S.-based workers and put up to thousands of foreign service officers and others on paid leave.

Workers from multiple agencies have also filed complaints with the office of a government watchdog lawyer who himself has been targeted by Mr. Trump for termination. In response to requests from that office, an independent federal worker board has considered some of the claims and temporarily reinstated some workers.

Workers at the Agriculture Department

Feb. 13 The Agriculture Department began cutting thousands of jobs, including around 3,400 in the Forest Service.

Three weeks later The Merit Systems Protection Board issued a stay ordering the department to reinstate fired workers while an investigation continued.

Six workers from six federal agencies

Feb. 14 The Office of Personnel Management sent an email ordering federal agencies to fire tens of thousands of probationary employees.

Less than two weeks later The Merit Systems Protection Board temporarily reinstated six fired federal workers from the Departments of Agriculture, Education, Energy, Housing and Urban Development and Veterans Affairs, and the Office of Personnel Management.

The back-and-forth and lack of transparency surrounding the administration’s cost-cutting moves have deepened the confusion and alarm of workers across the federal government at large, many of whom also have to interpret confusing email guidance and gauge the veracity of various circulating rumors.

“The layoffs and then rehires undermine the productivity and confidence not only of the people who left and came back but of the people who stayed,” said Stephen Goldsmith, an urban policy professor at Harvard’s Kennedy School and a former mayor of Indianapolis.