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Task configuration

testClusters {
  runTask {
    testDistribution = 'archive'
    numberOfNodes = 2 --> removing this line works perfectly and hits the breakpoint
  }
}

tasks.register("run", RunTask) {
  useCluster testClusters.runTask;
  description = 'Runs opensearch in the foreground'
  group = 'Verification'

  impliesSubProjects = true
}

What is "testClusters"? That is not a standard Gradle thing. Maybe you should ask the creators of whatever plugin that is?