steps

Method 1

1. Go into an sbt 1.7.1 project directory
2. Set Global / onChangedBuildSource := ReloadOnSourceChanges
3. run sbt ~compile
4. Edit build.sbt

Method 2 (simpler)

1. Run sbt ~compile in an sbt 1.7.1 project directory
2. When you see Press <enter> to interrupt or '?' for more options., hit the L key

problem

SBT dutifully restarts, but it doesn't go back into ~compile. Instead it quits to the system shell.

expectation

In sbt 1.6.x it would run ~compile again

Note: it's not specific to compile, the same thing seems to happen with any command.