Here is backtrack from breakpoint on kill.

(gdb) bt
#​0 0x00007ffff14ce670 in kill () from /usr/lib/libc.so.6
#​1 0x00007ffff4ca44f3 in ProcessPOSIX::DoDestroy (this=0x79ecb0) at ProcessPOSIX.cpp:344
#​2 0x00007ffff3a7f4ed in lldb_private::Process::Destroy (this=0x79ecb0) at Process.cpp:3754
#​3 0x00007ffff352631d in CommandObjectProcessLaunchOrAttach::StopProcessIfNecessary (this=0x55c0c0, process=0x79ecb0, state=@0x7fffffffb4a8: lldb::eStateLaunching, result=...)
at CommandObjectProcess.cpp:93
#​4 0x00007ffff3525b80 in CommandObjectProcessLaunch::DoExecute (this=0x55c0c0, launch_args=..., result=...) at CommandObjectProcess.cpp:202
#​5 0x00007ffff375e3c0 in lldb_private::CommandObjectParsed::Execute (this=0x55c0c0, args_string=0x799dc8 "-c/bin/sh -- "hello"", result=...) at CommandObject.cpp:1031
#​6 0x00007ffff3751731 in lldb_private::CommandInterpreter::HandleCommand (this=0x564700, command_line=0x77c7c8 "run "hello"", lazy_add_to_history=lldb_private::eLazyBoolCalculate,
result=..., override_context=0x0, repeat_on_empty_command=true, no_context_switching=false) at CommandInterpreter.cpp:1858
#​7 0x00007ffff3755941 in lldb_private::CommandInterpreter::IOHandlerInputComplete (this=0x564700, io_handler=..., line=...) at CommandInterpreter.cpp:2996
#​8 0x00007ffff3755c37 in non-virtual thunk to lldb_private::CommandInterpreter::IOHandlerInputComplete(lldb_private::IOHandler&, std::string&) () at CommandInterpreter.cpp:3043
#​9 0x00007ffff35be1e2 in lldb_private::IOHandlerEditline::Run (this=0x761bb0) at IOHandler.cpp:576
#​10 0x00007ffff359c2cc in lldb_private::Debugger::ExecuteIOHanders (this=0x504ea0) at Debugger.cpp:864
#​11 0x00007ffff375604b in lldb_private::CommandInterpreter::RunCommandInterpreter (this=0x564700, auto_handle_events=true, spawn_thread=false) at CommandInterpreter.cpp:3129
#​12 0x00007ffff346453a in lldb::SBDebugger::RunCommandInterpreter (this=0x7fffffffe548, auto_handle_events=true, spawn_thread=false) at SBDebugger.cpp:961
#​13 0x0000000000408c88 in Driver::MainLoop (this=0x7fffffffe528) at Driver.cpp:967
#​14 0x00000000004090eb in main (argc=1, argv=0x7fffffffe708, envp=0x7fffffffe718) at Driver.cpp:1066

On FreeBSD the 2nd process launch hangs instead of crashing

WIP take on 2nd part of bug
Ed, could you please take a look how it works on FreeBSD? It is not really well tested, but I think it is correct. My doubt is why it is not needed gdb-remote, but I don't see how else public state could be fixed in this codepath.

works now.