Ok, this is a valid solution. And I will probably change it in the IDE for now. That is, as long as the debugger does not debug processes launched by the debuggee (no plans for that yet).
At the moment, with poDebugProcess, fpdebug is notified on forked processes, and fpdebug releases them into the wild.
Still curious why you run into it.
It would make sense, if your IDE was 32 bits (I have not tested on my end, if it actually triggers it).
With a 32bit IDE, the included fpdebug is of course 32bit too. And a 32bit debugger can not debug a 64bit app. (So the OS would not allow a 64bit process being forked).
But if the IDE is 64 bit.....
Just to be sure that you did not accidentally rebuild the IDE. Please open the Task Manager (ctrl-shift escape on win 10), and when the IDE is running find it in the list (looking at the first tab "processes", not "details"). Make sure neither the IDE (nor its sub entries) have an appendix "(32 bit)"
Btw, by writing those steps down, I noted: I have a 32bit version of notepad++ installed. So that may be a difference there.
Maybe windows already can not tell a 64 bit debugger, that a 32 bit process launches a 64bit exe. After all, to debug 32 bits the 64bit debugger must use a special WOW64 api, which deals with 32 bits only......
Well anyway, we know how to fix it....
https://bugs.freepascal.org/view.php?id=38546