Hi, someone (kernel-help) on IRC today was having issues using an inferior kernel with their os configuration and reported that guix was "hanging". It turns out that guix was actually building the kernel in the background, but did not report anything to the user. kernel-help was kind enough to share their config, and I can confirm that guix is building the kernel, but doesn't tell anything. I was able to track this done to a call to operating-system-derivation, which is supposed to return the path to a .drv file. I did not expect it to have to build anything, since it's only computing a derivation name. Using the attached operating system declaration, defining it as "os", you can see that calling ((operating-system-derivation os) (open-connection)) "hangs" with no message, and a build user is building the kernel (unless you already have the kernel built). Note that the build process continues even if you interrupt that procedure, and only stops after you exit guix repl entirely. Going one step further, operating-system-derivation calls fold-services (which is fine), then service-value (which is also fine) and calls that value with the store, which builds the kernel without saying anything. That value comes from the root service type, system-service-type and its system-derivation procedure. With some pk, I was able to find that mapm/accumulate-builds was the culprit, but I don't know how to investigate further.