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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 ThreadStartRequest/ThreadDeathRequest define a new method to control whether thread start/end events are sent for all threads or only platform threads.

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

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• includevirtualthreads control includevirtualthreads control whether or not virtual threads are included in the list of threads returned by JDWP VirtualThread.GetAllThreads. This flag can be turned on for compatibility purposes. This flag may eventually go away and the debug agent will operate as if it was set to 'n'. Note that the debug agent will only return virtual threads that are created after the debugger attaches. If the debugger detaches, the debug agent will forget about all discovered virtual threads, and the list will once again be empty when the debugger attaches again.
• [notifyvthreads has been removed. To disable THREAD_START and THREAD_END events for vthreads, use the PlatformThreadsOnly filter as described in this section] notifyvthreads controls whether or not THREAD_START and THREAD_END events are sent for virtual threads. The default is to send them. The purpose is to allow debugger writers to use notifyvthreads=n to see how the debugger works without getting these events. This is meant as a short term convenience flag rather than having to set the PlatformThreadsOnly filter as described above. Once support for notifyvthreads=n is gone, if debuggers don't want THREAD_START and THREAD_END events for virtual threads, they will need to set the PlatformThreadsOnly filter. When using the PlatformThreadsOnly filter, the debugger can learn about virtual threads when events are delivered for them, such as a BreakpointEvent. Since no THREAD_END event will be sent for the virtual thread, the debugger will then need to figure out how to "forget" about the virtual threads it is tracking when they have terminated. This could possibly be done with a ThreadDeathRequest that filters on the virtual thread. This would need to be done for each virtual thread being tracked by the debugger. Please note that notifyvthreads=y will not override any PlatformThreadsOnly filter that is in place.

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