Stopping children being terminated when parent process was started in a Job I can't control

I have a process (A) that I don't control that starts my own developed process (B) which in turn will start several other processes (C).

It looks like A starts B using a Job object as when A is terminated B is also terminated. I've also confirmed this with Process Explorer. The issue I am having is that the child processes of B are also being terminated, which is normal behavior for Job objects.

Is there a way for me to launch child processes from B that don't inherit the Job attributes or have a new set of attributes?

I've tried creating a new Job and assigning the child processes to that, but it seems this is just meaning the child processes belong to two jobs and are still terminated.

Has anyone come across this before?

If Process B is starting Process C via CreateProcess(), then Process B can specify the CREATE_BREAKAWAY_FROM_JOB flag:

Process Creation Flags

> | Constant/value | Description |
> | -------------- | ----------- |
> | CREATE_BREAKAWAY_FROM_JOB<br>0x01000000 | The child processes of a process associated with a job are not associated with the job.<br>If the calling process is not associated with a job, this constant has no effect. If the calling process is associated with a job, the job must set the JOB_OBJECT_LIMIT_BREAKAWAY_OK limit. |

But, as stated, this only works if the Job has the JOB_OBJECT_LIMIT_BREAKAWAY_OK limit enabled to allow child processes to "break away" from the job:

Job Objects | Managing Processes in Jobs

> After a process is associated with a job, by default any child processes it creates using CreateProcess are also associated with the job. (Child processes created using Win32_Process.Create are not associated with the job.) This default behavior can be changed by setting the extended limit JOB_OBJECT_LIMIT_BREAKAWAY_OK or JOB_OBJECT_LIMIT_SILENT_BREAKAWAY_OK for the job.
>
> - If the job has the extended limit JOB_OBJECT_LIMIT_BREAKAWAY_OK and the parent process was created with the CREATE_BREAKAWAY_FROM_JOB flag, then child processes of the parent process are not associated with the job.
>
> - If the job has the extended limit JOB_OBJECT_LIMIT_SILENT_BREAKAWAY_OK, then child processes of any parent process associated with the job are not associated with the job. It is not necessary for parent processes to be created with the CREATE_BREAKAWAY_FROM_JOB flag.

If Process A does not enable the JOB_OBJECT_LIMIT_BREAKAWAY_OK limit, then it doesn't want break aways. Process B might be able to update that, but only if it knows the name of the Job that it is running in so it can obtain a HANDLE to that Job:

IsProcessInJob function

> An application cannot obtain a handle to the job object in which it is running unless it has the name of the job object. However, an application can call the QueryInformationJobObject function with NULL to obtain information about the job object.