I get the following error message when starting the CDK Server Adapter on MacOSX (DevStudio was started from the dock, not from CLI):

The provider 'virtualbox' that was requested to back the machine
'default' is reporting that it isn't usable on this system. The
reason is shown below:

Vagrant could not detect VirtualBox! Make sure VirtualBox is properly installed.
Vagrant uses the `VBoxManage` binary that ships with VirtualBox, and requires
this to be available on the PATH. If VirtualBox is installed, please find the
`VBoxManage` binary and add it to the PATH environmental variable.

when starting DevStudio from CLI, it inherits from the terminal PATH and then it works.

We had a similar issue in Docker tooling ('docker-machine' needs to be in the PATH, as well as 'VBoxManage' or any other VM driver) so we ended up adding some preferences to set the correct path.
That might be interesting to see how the Docker tooling, the Vagrant tooling and the CDK tooling could use the same preferences.