With the stroke of a pen this week, Betsy DeVos, President Trump’s new education secretary, thrust the future of the government’s system for managing federal student loans into confusion.

It was a high-stakes move: Her department administers $1.3 trillion in loans on behalf of nearly 43 million student borrowers.

At issue is which companies will handle the bulk of those loans in the future, and how they will do it. Under the Obama administration, the Education Department was on the verge of selecting a single vendor to build a new system for servicing its student loans, in what was expected to be one of the largest federal contracts outside of the military.

But on Tuesday, Ms. DeVos signed an order rescinding key parts of that attempt to streamline the system — essentially hitting the reset button on the Obama-era plan.