ThreadMXBean.getAllThreadIds filters out JVMTI agent threads. See JVM_GetAllThreads use of ThreadsListEnumerator where include_jvmti_agent_threads=false.

On the other hand, ThreadMXBean.getThreadInfo(long) returns the thread info for a JVMTI agent thread if it has the given thread ID.

This inconsistency should be re-examined and also compared to other APIs that enumerate threads, e.g. Thread.getAllStackTraces does not enumerate JVMTI agent threads. It may be that some spec clarification is needed.