Cannot bring docker-compose to background with Ctrl-B

[akiross]

Describe the bug
process-compose has a feature that allows to "send the TUI in background" by pressing Ctrl-B (relevant issue). When TUI is on the foreground, Ctrl-B will apparently start a new shell (bash) and when that exists, the TUI will be back.
I can do that when running process-compose attach, but if I use devenv up, Ctrl-B will flash a terminal for an instant and then it will go back to the TUI.

To reproduce

1. devenv init in an empty with v1.2.0
2. create a simple process like while true; do sleep 1; echo "foo" ; done
3. devenv up to get into process-compose
4. press Ctrl-B to put process-compose in background
5. process-compose won't go in background

Version

devenv 1.2.0 (x86_64-linux)

devenv installed via nixpkgs. My system config is a flake.