Issue #19387 has been updated by osyoyu (Daisuke Aritomo). I also ran into this, so I opened an pull request document this behavior. https://github.com/ruby/ruby/pull/13278 ---------------------------------------- Bug #19387: Issue with ObjectSpace.each_objects not returning objects after starting a ractor https://bugs.ruby-lang.org/issues/19387#change-113039 * Author: luke-gru (Luke Gruber) * Status: Assigned * Assignee: ractor * ruby -v: 3.3.0 * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- ```ruby r = Ractor.new do receive # block, the problem is not the termination of the ractor but the starting end ObjectSpace.each_object(IO) { |io| p io # we get no objects } ``` -- https://bugs.ruby-lang.org/