Page History

...

Virtual threads are just objects in the heap, there may be millions of them. There is no API support in the debugger API for enumerating all virtual threads.

JDI VirtualThreads.allThreads() (and JDWP VirtualMachine/AllThreads) enumerates all live platform threads, virtual threads are not enumerated unless the JDWP agent is started with the includevirtualthreads option (see below).

...

Virtual threads are not members of a thread group. 

JDI ThreadGroupReference::threads (and JDWP ThreadGroupReference/Children) enumerate all live platform threads in a group, virtual threads are not enumerated.

...

JDI ThreadStartEvent/ThreadDeathEvents are sent for all threads when enabled. This may impact performance if there are a huge number of virtual threads.

JDWP EventRequest/Set defines a new PlatformThreadsOnly filter that can be used when requesting THREAD_START and THREAD_END events. This allows these events to be filtered for virtual threads so they are not sent to the front-end/debugger.

...

JDI ThreadReference defines isVirtual() to test if a thread is a virtual thread.

JDWP ThreadReference/IsVirtual is the equivalent.

Testing if target VM supports virtual threads

...