From 72b2e47376ba30103e9eeec3c732dcab4debb4eb Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Mon, 14 Sep 2026 18:45:09 +0900
Subject: [PATCH 01/10] Keep the Ruby::Box experimental warning out of test
 subprocess output

Under RUBY_BOX=1 every spawned ruby prints an experimental warning to stderr, which breaks assertions on subprocess output in both suites. The Bundler specs filter the captured stderr instead of adding -W:no-experimental to RUBYOPT, because several of them assert the exact RUBYOPT propagated to subprocesses.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 spec/support/command_execution.rb | 15 ++++++++++++++-
 test/rubygems/helper.rb           | 11 +++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/spec/support/command_execution.rb b/spec/support/command_execution.rb
index e2915b996d9d..14da54dca4da 100644
--- a/spec/support/command_execution.rb
+++ b/spec/support/command_execution.rb
@@ -2,6 +2,13 @@
 
 module Spec
   class CommandExecution
+    # Under RUBY_BOX, every spawned ruby prints an experimental warning to
+    # stderr, breaking specs that assert clean stderr.
+    RUBY_BOX_WARNING = Regexp.union(
+      /^[^\n]*: warning: Ruby::Box is experimental, and the behavior may change in the future!\n?/,
+      %r{^See https://docs\.ruby-lang\.org/\S+ for known issues, etc\.\n?}
+    )
+
     def initialize(command, timeout:)
       @command = command
       @timeout = timeout
@@ -72,7 +79,13 @@ def failure?
     attr_reader :failure_reason
 
     def normalize(string)
-      string.dup.force_encoding(Encoding::UTF_8).scrub.strip.gsub("\r\n", "\n")
+      string = string.dup.force_encoding(Encoding::UTF_8).scrub.gsub("\r\n", "\n")
+      string = string.gsub(RUBY_BOX_WARNING, "") if ruby_box_enabled?
+      string.strip
+    end
+
+    def ruby_box_enabled?
+      defined?(Ruby::Box) && Ruby::Box.enabled?
     end
   end
 end
diff --git a/test/rubygems/helper.rb b/test/rubygems/helper.rb
index 09b7f427ebbf..f2203675c957 100644
--- a/test/rubygems/helper.rb
+++ b/test/rubygems/helper.rb
@@ -404,6 +404,10 @@ def setup
     ENV["BUNDLE_COOLDOWN"] = nil
     ENV["RUBYGEMS_PREVENT_UPDATE_SUGGESTION"] = "true"
 
+    # Child ruby processes inherit RUBY_BOX and print an experimental
+    # warning on startup, breaking assertions on subprocess stderr.
+    ENV["RUBYOPT"] = [ENV["RUBYOPT"], "-W:no-experimental"].compact.join(" ") if ruby_box_enabled?
+
     @current_dir = Dir.pwd
     @fetcher     = nil
 
@@ -1440,6 +1444,13 @@ def ruby_repo?
     !ENV["GEM_COMMAND"].nil?
   end
 
+  ##
+  # Is this test running under Ruby::Box (RUBY_BOX=1)?
+
+  def ruby_box_enabled?
+    defined?(Ruby::Box) && Ruby::Box.enabled?
+  end
+
   ##
   # Returns the make command for the current platform. For versions of Ruby
   # built on MS Windows with VC++ or Borland it will return 'nmake'. On all

From 67147d48a1e9c3b62a385cc8950c4a6a3b92f1bc Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Mon, 14 Sep 2026 18:45:31 +0900
Subject: [PATCH 02/10] Use Process.last_status instead of $?

Ruby::Box leaves $? uninitialized, so status checks read success after a failing command. Under RUBY_BOX=1 this made Gem::Source::Git#rev_parse swallow rev-parse failures and the release tool carry on with empty output.

https://bugs.ruby-lang.org/issues/22280

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 lib/bundler/gem_helper.rb                   |  2 +-
 lib/rubygems/source/git.rb                  |  4 +++-
 spec/runtime/env_helpers_spec.rb            | 12 ++++++------
 test/rubygems/test_exit.rb                  |  3 ++-
 test/rubygems/test_gem_ext_builder.rb       |  2 +-
 test/rubygems/test_gem_ext_cargo_builder.rb |  2 +-
 test/rubygems/test_require.rb               |  4 ++--
 test/rubygems/test_rubygems.rb              |  4 ++--
 tool/release.rb                             |  8 ++++----
 9 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/lib/bundler/gem_helper.rb b/lib/bundler/gem_helper.rb
index e3af1b957f35..ea02e7e7712b 100644
--- a/lib/bundler/gem_helper.rb
+++ b/lib/bundler/gem_helper.rb
@@ -216,7 +216,7 @@ def sh_with_status(cmd, &block)
       Bundler.ui.debug(cmd)
       SharedHelpers.chdir(base) do
         outbuf = IO.popen(cmd, err: [:child, :out], &:read)
-        status = $?
+        status = Process.last_status
         block&.call(outbuf) if status.success?
         [outbuf, status]
       end
diff --git a/lib/rubygems/source/git.rb b/lib/rubygems/source/git.rb
index baf2f9dd4c09..0ceb67b382f5 100644
--- a/lib/rubygems/source/git.rb
+++ b/lib/rubygems/source/git.rb
@@ -188,9 +188,11 @@ def rev_parse # :nodoc:
       hash = Gem::Util.popen(git_command, "rev-parse", @reference).strip
     end
 
+    # Process.last_status instead of $?, which Ruby::Box leaves uninitialized
+    # (https://bugs.ruby-lang.org/issues/22280)
     raise Gem::Exception,
           "unable to find reference #{@reference} in #{@repository}" unless
-            $?.success?
+            Process.last_status.success?
 
     hash
   end
diff --git a/spec/runtime/env_helpers_spec.rb b/spec/runtime/env_helpers_spec.rb
index 38f501e7cde6..0ebf86f29606 100644
--- a/spec/runtime/env_helpers_spec.rb
+++ b/spec/runtime/env_helpers_spec.rb
@@ -167,13 +167,13 @@ def run_bundler_script(env, script)
       create_file("source.rb", <<-'RUBY')
         Bundler.original_system("ruby", "-e", "exit(42) if ENV['BUNDLE_FOO'] == 'bar'")
 
-        exit $?.exitstatus
+        exit Process.last_status.exitstatus
       RUBY
     end
 
     it "runs system inside with_original_env" do
       run_bundler_script({ "BUNDLE_FOO" => "bar" }, bundled_app("source.rb"))
-      expect($?.exitstatus).to eq(42)
+      expect(Process.last_status.exitstatus).to eq(42)
     end
   end
 
@@ -182,13 +182,13 @@ def run_bundler_script(env, script)
       create_file("source.rb", <<-'RUBY')
         Bundler.unbundled_system("ruby", "-e", "exit(42) unless ENV['BUNDLE_FOO'] == 'bar'")
 
-        exit $?.exitstatus
+        exit Process.last_status.exitstatus
       RUBY
     end
 
     it "runs system inside with_unbundled_env" do
       run_bundler_script({ "BUNDLE_FOO" => "bar" }, bundled_app("source.rb"))
-      expect($?.exitstatus).to eq(42)
+      expect(Process.last_status.exitstatus).to eq(42)
     end
   end
 
@@ -209,7 +209,7 @@ def run_bundler_script(env, script)
       skip "Fork not implemented" if Gem.win_platform?
 
       run_bundler_script({ "BUNDLE_FOO" => "bar" }, bundled_app("source.rb"))
-      expect($?.exitstatus).to eq(0)
+      expect(Process.last_status.exitstatus).to eq(0)
     end
   end
 
@@ -230,7 +230,7 @@ def run_bundler_script(env, script)
       skip "Fork not implemented" if Gem.win_platform?
 
       run_bundler_script({ "BUNDLE_FOO" => "bar" }, bundled_app("source.rb"))
-      expect($?.exitstatus).to eq(1)
+      expect(Process.last_status.exitstatus).to eq(1)
     end
   end
 end
diff --git a/test/rubygems/test_exit.rb b/test/rubygems/test_exit.rb
index 396837edadfa..c339c39a67af 100644
--- a/test/rubygems/test_exit.rb
+++ b/test/rubygems/test_exit.rb
@@ -6,7 +6,8 @@
 class TestGemExit < Gem::TestCase
   def test_exit
     system(*ruby_with_rubygems_in_load_path, "-e", "raise Gem::SystemExitException.new(2)")
-    assert_equal 2, $?.exitstatus
+    # Process.last_status instead of $?, which Ruby::Box leaves uninitialized
+    assert_equal 2, Process.last_status.exitstatus
   end
 
   def test_status
diff --git a/test/rubygems/test_gem_ext_builder.rb b/test/rubygems/test_gem_ext_builder.rb
index 6b4eed2cf211..f5ad791ec1c9 100644
--- a/test/rubygems/test_gem_ext_builder.rb
+++ b/test/rubygems/test_gem_ext_builder.rb
@@ -700,7 +700,7 @@ def self.expand(val, config = CONFIG); val; end
       system(Gem.ruby, "-rmkmf", "-e", "exit MakeMakefile::RbConfig::CONFIG['host_os'] == 'fake_os'",
              "--", "--target-rbconfig=#{fake_rbconfig}")
     end
-    unless $?.success?
+    unless Process.last_status.success?
       assert_include(stderr, "uninitialized constant MakeMakefile::RbConfig")
       pend "This version of mkmf does not support --target-rbconfig"
     end
diff --git a/test/rubygems/test_gem_ext_cargo_builder.rb b/test/rubygems/test_gem_ext_cargo_builder.rb
index b970e442c250..94673a478c4e 100644
--- a/test/rubygems/test_gem_ext_cargo_builder.rb
+++ b/test/rubygems/test_gem_ext_cargo_builder.rb
@@ -199,7 +199,7 @@ def skip_unsupported_platforms!
     pend "jruby not supported" if Gem.java_platform?
     pend "truffleruby not supported (yet)" if RUBY_ENGINE == "truffleruby"
     system(@rust_envs, "cargo", "-V", out: IO::NULL, err: [:child, :out])
-    pend "cargo not present" unless $?.success?
+    pend "cargo not present" unless Process.last_status.success?
     pend "ruby.h is not provided by ruby repo" if ruby_repo?
     pend "rust toolchain of mingw is broken" if mingw_windows?
   end
diff --git a/test/rubygems/test_require.rb b/test/rubygems/test_require.rb
index db86a3090565..6816e42bfe13 100644
--- a/test/rubygems/test_require.rb
+++ b/test/rubygems/test_require.rb
@@ -484,7 +484,7 @@ def test_realworld_default_gem
       puts Gem.loaded_specs["json"]
     RUBY
     output = Gem::Util.popen(*ruby_with_rubygems_in_load_path, "-e", cmd).strip
-    assert $?.success?
+    assert Process.last_status.success?
     refute_empty output
   end
 
@@ -508,7 +508,7 @@ def test_realworld_upgraded_default_gem
     assert_equal "999.99.9", output.lines[0].chomp
     # Make sure only files from the newer json gem are loaded, and no files from the default json gem
     assert_equal ["#{@gemhome}/gems/json-999.99.9/lib/json.rb"], output.lines.grep(%r{/gems/json-}).map(&:chomp)
-    assert $?.success?
+    assert Process.last_status.success?
   end
 
   def test_default_gem_and_normal_gem
diff --git a/test/rubygems/test_rubygems.rb b/test/rubygems/test_rubygems.rb
index 6566b5981e69..02393c57fcae 100644
--- a/test/rubygems/test_rubygems.rb
+++ b/test/rubygems/test_rubygems.rb
@@ -5,7 +5,7 @@
 class GemTest < Gem::TestCase
   def test_rubygems_normal_behaviour
     _ = Gem::Util.popen(*ruby_with_rubygems_in_load_path, "-e", "'require \"rubygems\"'", { err: [:child, :out] }).strip
-    assert $?.success?
+    assert Process.last_status.success?
   end
 
   def test_operating_system_other_exceptions
@@ -17,7 +17,7 @@ def test_operating_system_other_exceptions
     RUBY
 
     output = Gem::Util.popen(*ruby_with_rubygems_and_fake_operating_system_in_load_path(path), "-e", "'require \"rubygems\"'", { err: [:child, :out] }).strip
-    assert !$?.success?
+    assert !Process.last_status.success?
     assert_match(/undefined local variable or method [`']intentionally_not_implemented_method'/, output)
     assert_includes output, "Loading the #{operating_system_rb_at(path)} file caused an error. " \
     "This file is owned by your OS, not by rubygems upstream. " \
diff --git a/tool/release.rb b/tool/release.rb
index 7585136b6c4f..2324b2d0f95f 100644
--- a/tool/release.rb
+++ b/tool/release.rb
@@ -442,7 +442,7 @@ def add_commit_authors!(pulls)
       ids = batch.flat_map {|pull| ["-F", "ids[]=#{pull.node_id}"] }
 
       json = IO.popen(["gh", "api", "graphql", "-f", "query=#{COMMIT_AUTHORS_QUERY}", *ids], &:read)
-      raise "Failed to list the commits of #{batch.map(&:number).join(", ")}" unless $?.success?
+      raise "Failed to list the commits of #{batch.map(&:number).join(", ")}" unless Process.last_status.success?
 
       credit_commit_authors(batch, JSON.parse(json).dig("data", "nodes"))
     end
@@ -501,7 +501,7 @@ def git_quietly(*args)
 
   def pull_requests_merged_into(base, from, to)
     commits = git_quietly("rev-list", "#{from}..#{to}")
-    raise "Failed to list the commits in #{from}..#{to}" unless $?.success?
+    raise "Failed to list the commits in #{from}..#{to}" unless Process.last_status.success?
 
     reachable = Set.new(commits.split("\n"))
 
@@ -511,12 +511,12 @@ def pull_requests_merged_into(base, from, to)
   # The date bound is deliberately loose. It bounds the query, not the result.
   def merged_pull_requests(base, since_ref)
     committed_at = git_quietly("log", "-1", "--format=%cI", since_ref).strip
-    raise "Failed to resolve #{since_ref}" unless $?.success?
+    raise "Failed to resolve #{since_ref}" unless Process.last_status.success?
 
     since = (Time.iso8601(committed_at) - 86_400).utc.strftime("%Y-%m-%d")
 
     json = `gh pr list --repo ruby/rubygems --state merged --base #{base} --search 'merged:>=#{since}' --limit #{MERGED_PULL_REQUEST_LIMIT} --json number,id,title,labels,mergeCommit,mergedAt,author,url`
-    raise "Failed to list pull requests merged into #{base} since #{since}" unless $?.success?
+    raise "Failed to list pull requests merged into #{base} since #{since}" unless Process.last_status.success?
 
     pull_requests_from(json, "#{base} since #{since}")
   end

From ec8b8db347cf6b8af0bc5e249c013ad0ac675b0d Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Mon, 14 Sep 2026 18:45:59 +0900
Subject: [PATCH 03/10] Pend tests that capture stdio under Ruby::Box

Each box gets detached copies of the stdio globals, so reassigning $stdout or $stderr cannot capture output written by Kernel#warn, Kernel#puts or subprocesses.

https://bugs.ruby-lang.org/issues/21867

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 spec/bundler/plugin_spec.rb                            |  6 ++++++
 test/rubygems/helper.rb                                | 10 ++++++++++
 test/rubygems/test_deprecate.rb                        |  3 +++
 test/rubygems/test_gem.rb                              |  2 ++
 test/rubygems/test_gem_commands_build_command.rb       |  1 +
 test/rubygems/test_gem_commands_open_command.rb        |  1 +
 test/rubygems/test_gem_config_file.rb                  |  1 +
 test/rubygems/test_gem_doctor.rb                       |  2 ++
 test/rubygems/test_gem_package.rb                      |  2 ++
 test/rubygems/test_gem_request_set.rb                  |  2 ++
 .../test_gem_request_set_gem_dependency_api.rb         |  3 +++
 test/rubygems/test_gem_specification.rb                |  5 +++++
 test/rubygems/test_gem_stub_specification.rb           |  1 +
 test/rubygems/test_require.rb                          |  4 ++++
 14 files changed, 43 insertions(+)

diff --git a/spec/bundler/plugin_spec.rb b/spec/bundler/plugin_spec.rb
index 1e10036b63c2..5f5054b68425 100644
--- a/spec/bundler/plugin_spec.rb
+++ b/spec/bundler/plugin_spec.rb
@@ -318,6 +318,8 @@
     end
 
     it "executes the hook" do
+      skip "Ruby::Box ignores $stdout reassignment (https://bugs.ruby-lang.org/issues/21867)" if defined?(Ruby::Box) && Ruby::Box.enabled?
+
       expect do
         Plugin.hook(Bundler::Plugin::Events::EVENT1)
       end.to output("hook for event 1\n").to_stdout
@@ -331,6 +333,8 @@
       RUBY
 
       it "evals plugins.rb once" do
+        skip "Ruby::Box ignores $stdout reassignment (https://bugs.ruby-lang.org/issues/21867)" if defined?(Ruby::Box) && Ruby::Box.enabled?
+
         expect do
           Plugin.hook(Bundler::Plugin::Events::EVENT1)
           Plugin.hook(Bundler::Plugin::Events::EVENT2)
@@ -344,6 +348,8 @@
       RUBY
 
       it "is passed to the hook" do
+        skip "Ruby::Box ignores $stdout reassignment (https://bugs.ruby-lang.org/issues/21867)" if defined?(Ruby::Box) && Ruby::Box.enabled?
+
         expect do
           Plugin.hook(Bundler::Plugin::Events::EVENT1) { puts "win" }
         end.to output("win\n").to_stdout
diff --git a/test/rubygems/helper.rb b/test/rubygems/helper.rb
index f2203675c957..38ac67be3add 100644
--- a/test/rubygems/helper.rb
+++ b/test/rubygems/helper.rb
@@ -1451,6 +1451,16 @@ def ruby_box_enabled?
     defined?(Ruby::Box) && Ruby::Box.enabled?
   end
 
+  ##
+  # Ruby::Box gives each box detached copies of the stdio globals, so
+  # reassigning $stdout/$stderr cannot capture output written by Kernel#warn,
+  # Kernel#puts or subprocesses. Pends until the ruby-core fix for
+  # https://bugs.ruby-lang.org/issues/21867 lands.
+
+  def pend_for_ruby_box_stdio_capture
+    pend "Ruby::Box breaks $stdout/$stderr capture (https://bugs.ruby-lang.org/issues/21867)" if ruby_box_enabled?
+  end
+
   ##
   # Returns the make command for the current platform. For versions of Ruby
   # built on MS Windows with VC++ or Borland it will return 'nmake'. On all
diff --git a/test/rubygems/test_deprecate.rb b/test/rubygems/test_deprecate.rb
index bb6a0b5ceaaf..5700d356e756 100644
--- a/test/rubygems/test_deprecate.rb
+++ b/test/rubygems/test_deprecate.rb
@@ -132,6 +132,7 @@ def test_deprecated_method_calls_the_old_method
   end
 
   def test_deprecated_method_outputs_a_warning
+    pend_for_ruby_box_stdio_capture
     out, err = capture_output do
       thing = Thing.new
       thing.foo
@@ -165,6 +166,7 @@ def execute
   end
 
   def test_deprecated_method_outputs_a_warning_old_way
+    pend_for_ruby_box_stdio_capture
     out, err = capture_output do
       thing = OtherThing.new
       thing.foo
@@ -180,6 +182,7 @@ def test_deprecated_method_outputs_a_warning_old_way
   end
 
   def test_deprecated_method_when_class_overrides_format
+    pend_for_ruby_box_stdio_capture
     out, err = capture_output do
       thing = ThingWithFormat.new
       thing.foo
diff --git a/test/rubygems/test_gem.rb b/test/rubygems/test_gem.rb
index 88b461a2a0a7..36067549c863 100644
--- a/test/rubygems/test_gem.rb
+++ b/test/rubygems/test_gem.rb
@@ -1297,6 +1297,7 @@ def test_self_try_activate_missing_prerelease
   end
 
   def test_self_try_activate_missing_extensions
+    pend_for_ruby_box_stdio_capture
     spec = util_spec "ext", "1" do |s|
       s.extensions = %w[ext/extconf.rb]
       s.installed_by_version = v("2.2")
@@ -1352,6 +1353,7 @@ def test_setting_paths_does_not_mutate_parameter_object
   end
 
   def test_deprecated_paths=
+    pend_for_ruby_box_stdio_capture
     stdout, stderr = capture_output do
       Gem.paths = { "GEM_HOME" => Gem.paths.home,
                     "GEM_PATH" => [Gem.paths.home, "foo"] }
diff --git a/test/rubygems/test_gem_commands_build_command.rb b/test/rubygems/test_gem_commands_build_command.rb
index 771eb07dbc9c..5bbb7c3b3e35 100644
--- a/test/rubygems/test_gem_commands_build_command.rb
+++ b/test/rubygems/test_gem_commands_build_command.rb
@@ -383,6 +383,7 @@ def test_execute_strict_with_warnings
   end
 
   def test_execute_bad_spec
+    pend_for_ruby_box_stdio_capture
     @gem.date = "2010-11-08"
 
     gemspec_file = File.join(@tempdir, @gem.spec_name)
diff --git a/test/rubygems/test_gem_commands_open_command.rb b/test/rubygems/test_gem_commands_open_command.rb
index 3a774a9343c0..c30117a58ecc 100644
--- a/test/rubygems/test_gem_commands_open_command.rb
+++ b/test/rubygems/test_gem_commands_open_command.rb
@@ -21,6 +21,7 @@ def gem(name, version = "1.0")
   end
 
   def test_execute
+    pend_for_ruby_box_stdio_capture
     omit "JRuby on Windows spawns the editor with a different cwd" if Gem.win_platform? && Gem.java_platform?
 
     @cmd.options[:args] = %w[foo]
diff --git a/test/rubygems/test_gem_config_file.rb b/test/rubygems/test_gem_config_file.rb
index 2c33192a4b3a..7120c49e327a 100644
--- a/test/rubygems/test_gem_config_file.rb
+++ b/test/rubygems/test_gem_config_file.rb
@@ -314,6 +314,7 @@ def test_handle_arguments_backtrace
   end
 
   def test_handle_arguments_debug
+    pend_for_ruby_box_stdio_capture
     assert_equal false, $DEBUG
 
     args = %w[--debug]
diff --git a/test/rubygems/test_gem_doctor.rb b/test/rubygems/test_gem_doctor.rb
index 1554e7af128d..da625000ff90 100644
--- a/test/rubygems/test_gem_doctor.rb
+++ b/test/rubygems/test_gem_doctor.rb
@@ -240,6 +240,7 @@ def test_doctor_preserves_valid_abi_scoped_gemspec
   end
 
   def test_doctor_removes_corrupt_abi_scoped_gemspec
+    pend_for_ruby_box_stdio_capture
     install_specs util_spec "regular_gem"
 
     spec = util_ca_spec "ca_gem", "1", "aabbccdd",
@@ -286,6 +287,7 @@ def test_doctor_preserves_other_abi_dir
   end
 
   def test_doctor_does_not_recurse_into_abi_symlink
+    pend_for_ruby_box_stdio_capture
     pend "symlinks not supported" unless symlink_supported?
 
     install_specs util_spec "regular_gem"
diff --git a/test/rubygems/test_gem_package.rb b/test/rubygems/test_gem_package.rb
index b0935693d1c7..4e83b3a69b46 100644
--- a/test/rubygems/test_gem_package.rb
+++ b/test/rubygems/test_gem_package.rb
@@ -1538,6 +1538,7 @@ def test_verify_corrupt
   end
 
   def test_verify_corrupt_tar_metadata_entry
+    pend_for_ruby_box_stdio_capture
     gem = tar_file_header("metadata.gz", "", 0, 999, Time.now)
 
     File.open "corrupt.gem", "wb" do |io|
@@ -1574,6 +1575,7 @@ def test_verify_corrupt_tar_checksums_entry
   end
 
   def test_verify_corrupt_tar_data_entry
+    pend_for_ruby_box_stdio_capture
     gem = tar_file_header("data.tar.gz", "", 0, 100, Time.now)
 
     File.open "corrupt.gem", "wb" do |io|
diff --git a/test/rubygems/test_gem_request_set.rb b/test/rubygems/test_gem_request_set.rb
index 8c8be04fb9f9..60ff8724aef4 100644
--- a/test/rubygems/test_gem_request_set.rb
+++ b/test/rubygems/test_gem_request_set.rb
@@ -71,6 +71,7 @@ def test_install_from_gemdeps
   end
 
   def test_install_from_gemdeps_explain
+    pend_for_ruby_box_stdio_capture
     spec_fetcher do |fetcher|
       fetcher.gem "a", 2
     end
@@ -94,6 +95,7 @@ def test_install_from_gemdeps_explain
   end
 
   def test_install_from_gemdeps_explain_verbose
+    pend_for_ruby_box_stdio_capture
     spec_fetcher do |fetcher|
       fetcher.gem "a", 2
     end
diff --git a/test/rubygems/test_gem_request_set_gem_dependency_api.rb b/test/rubygems/test_gem_request_set_gem_dependency_api.rb
index 4b5eaa38eda8..d8f4e7f6e92b 100644
--- a/test/rubygems/test_gem_request_set_gem_dependency_api.rb
+++ b/test/rubygems/test_gem_request_set_gem_dependency_api.rb
@@ -78,6 +78,7 @@ def test_gem
   end
 
   def test_gem_duplicate
+    pend_for_ruby_box_stdio_capture
     @gda.gem "a"
 
     _, err = capture_output do
@@ -128,6 +129,7 @@ def test_gem_bitbucket_expand_path
   end
 
   def test_gem_git_branch
+    pend_for_ruby_box_stdio_capture
     _, err = capture_output do
       @gda.gem "a", git: "git/a", branch: "other", tag: "v1"
     end
@@ -149,6 +151,7 @@ def test_gem_git_gist
   end
 
   def test_gem_git_ref
+    pend_for_ruby_box_stdio_capture
     _, err = capture_output do
       @gda.gem "a", git: "git/a", ref: "abcd123", branch: "other"
     end
diff --git a/test/rubygems/test_gem_specification.rb b/test/rubygems/test_gem_specification.rb
index dc32a6290786..0f107d12529a 100644
--- a/test/rubygems/test_gem_specification.rb
+++ b/test/rubygems/test_gem_specification.rb
@@ -1576,6 +1576,7 @@ def test_contains_requirable_file_eh
   end
 
   def test_contains_requirable_file_eh_extension
+    pend_for_ruby_box_stdio_capture
     ext_spec
 
     _, err = capture_output do
@@ -3386,6 +3387,7 @@ def test_validate_files
   end
 
   def test_unresolved_specs
+    pend_for_ruby_box_stdio_capture
     specification = Gem::Specification.clone
 
     set_orig specification
@@ -3412,6 +3414,7 @@ def test_unresolved_specs
   end
 
   def test_unresolved_specs_with_versions
+    pend_for_ruby_box_stdio_capture
     specification = Gem::Specification.clone
 
     set_orig specification
@@ -3444,6 +3447,7 @@ def test_unresolved_specs_with_versions
   end
 
   def test_unresolved_specs_with_duplicated_versions
+    pend_for_ruby_box_stdio_capture
     specification = Gem::Specification.clone
 
     set_orig specification
@@ -3497,6 +3501,7 @@ def test_unresolved_specs_with_unrestricted_deps_on_default_gems
   end
 
   def test_duplicate_runtime_dependency
+    pend_for_ruby_box_stdio_capture
     expected = "WARNING: duplicated b dependency [\"~> 3.0\", \"~> 3.0\"]\n"
     out, err = capture_output do
       @a1.add_dependency "b", "~> 3.0", "~> 3.0"
diff --git a/test/rubygems/test_gem_stub_specification.rb b/test/rubygems/test_gem_stub_specification.rb
index 1aa3b6532436..66bdd3d3fbbb 100644
--- a/test/rubygems/test_gem_stub_specification.rb
+++ b/test/rubygems/test_gem_stub_specification.rb
@@ -94,6 +94,7 @@ def test_contains_requirable_file_eh
   end
 
   def test_contains_requirable_file_eh_extension
+    pend_for_ruby_box_stdio_capture
     stub_with_extension do |stub|
       _, err = capture_output do
         if RUBY_ENGINE == "jruby"
diff --git a/test/rubygems/test_require.rb b/test/rubygems/test_require.rb
index 6816e42bfe13..ef1bb2e465a2 100644
--- a/test/rubygems/test_require.rb
+++ b/test/rubygems/test_require.rb
@@ -718,6 +718,7 @@ def test_require_bundler
 
   ["", "Kernel."].each do |prefix|
     define_method "test_no_kernel_require_in_#{prefix.tr(".", "_")}warn_with_uplevel" do
+      pend_for_ruby_box_stdio_capture
       Dir.mktmpdir("warn_test") do |dir|
         File.write(dir + "/sub.rb", "#{prefix}warn 'uplevel', 'test', uplevel: 1\n")
         File.write(dir + "/main.rb", "require 'sub'\n")
@@ -733,6 +734,7 @@ def test_require_bundler
     end
 
     define_method "test_no_other_behavioral_changes_with_#{prefix.tr(".", "_")}warn" do
+      pend_for_ruby_box_stdio_capture
       Dir.mktmpdir("warn_test") do |dir|
         File.write(dir + "/main.rb", "#{prefix}warn({x:1}, {y:2}, [])\n")
         _, err = capture_subprocess_io do
@@ -748,6 +750,7 @@ def test_require_bundler
   end
 
   def test_no_crash_when_overriding_warn_with_warning_module
+    pend_for_ruby_box_stdio_capture
     Dir.mktmpdir("warn_test") do |dir|
       File.write(dir + "/main.rb", "module Warning; def warn(str); super; end; end; warn 'Foo Bar'")
       _, err = capture_subprocess_io do
@@ -762,6 +765,7 @@ def test_no_crash_when_overriding_warn_with_warning_module
   end
 
   def test_expected_backtrace_location_when_inheriting_from_basic_object_and_including_kernel
+    pend_for_ruby_box_stdio_capture
     Dir.mktmpdir("warn_test") do |dir|
       File.write(dir + "/main.rb", "\nrequire 'sub'\n")
       File.write(dir + "/sub.rb", <<-'RUBY')

From 90bdecc0dcd745b595be4c4a57c3f1ae72d2d771 Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Mon, 14 Sep 2026 18:46:09 +0900
Subject: [PATCH 04/10] Pend the Ractor tar header tests under Ruby::Box

Ruby::Box ignores $VERBOSE=, so assert_ractor cannot keep the Ractor experimental warning out of the child stderr.

https://bugs.ruby-lang.org/issues/22282

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 test/rubygems/test_gem_package_tar_header_ractor.rb | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/test/rubygems/test_gem_package_tar_header_ractor.rb b/test/rubygems/test_gem_package_tar_header_ractor.rb
index 57140648052e..d2fc0f69b1e9 100644
--- a/test/rubygems/test_gem_package_tar_header_ractor.rb
+++ b/test/rubygems/test_gem_package_tar_header_ractor.rb
@@ -8,6 +8,11 @@
 end
 
 class TestGemPackageTarHeaderRactor < Gem::Package::TarTestCase
+  def setup
+    super
+    pend "Ruby::Box ignores $VERBOSE=, so assert_ractor cannot keep the Ractor experimental warning out of the child stderr (https://bugs.ruby-lang.org/issues/22282)" if ruby_box_enabled?
+  end
+
   SETUP = <<~RUBY
     header = {
       name: "x",

From c94b20043319de83cb1b4c010fc4549319f9efa2 Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Mon, 14 Sep 2026 18:46:37 +0900
Subject: [PATCH 05/10] Run the suites on a ruby-core master build with and
 without RUBY_BOX=1

The setup-ruby head build lags ruby/ruby by up to a day, so Ruby::Box fixes that have already landed would stay out of a head lane.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 .github/workflows/ruby-core.yml | 56 +++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/.github/workflows/ruby-core.yml b/.github/workflows/ruby-core.yml
index 68a5171b13be..3ff91a5d72e4 100644
--- a/.github/workflows/ruby-core.yml
+++ b/.github/workflows/ruby-core.yml
@@ -92,6 +92,61 @@ jobs:
         working-directory: ruby/ruby
         if: matrix.target == 'Bundler'
 
+  ruby_core_master:
+    name: ${{ matrix.suite.name }} on a ruby-core master build${{ matrix.box && ' (RUBY_BOX=1)' || '' }}
+    runs-on: ubuntu-24.04
+    strategy:
+      fail-fast: false
+      matrix:
+        suite:
+          - { name: Rubygems, deps: setup, task: test:parallel }
+          - { name: Bundler, deps: spec:deps, task: spec:regular, rubyopt: --disable-gems }
+        box: [false, true]
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          repository: ruby/ruby
+          path: ruby/ruby
+          ref: master
+          persist-credentials: false
+      - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
+        with:
+          ruby-version: 3.4
+          bundler: none
+      - name: Install libraries
+        run: |
+          set -x
+          sudo apt-get update -q || :
+          sudo apt-get install --no-install-recommends -q -y build-essential libssl-dev libyaml-dev libreadline6-dev zlib1g-dev libncurses5-dev libffi-dev libgdbm-dev bison autoconf
+      - name: Build and install Ruby
+        run: |
+          export GNUMAKEFLAGS="-j$((1 + $(nproc)))"
+          ./autogen.sh
+          ./configure -C --disable-install-doc --prefix="$RUNNER_TEMP/ruby"
+          make
+          make install
+          echo "$RUNNER_TEMP/ruby/bin" >> "$GITHUB_PATH"
+        working-directory: ruby/ruby
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          path: rubygems
+          persist-credentials: false
+      - name: Install dependencies
+        run: |
+          ruby -v
+          bin/rake ${{ matrix.suite.deps }}
+        env:
+          RUBYOPT: ${{ matrix.suite.rubyopt }}
+        working-directory: rubygems
+      - name: Run Test
+        run: bin/rake ${{ matrix.suite.task }}
+        env:
+          RUBYOPT: ${{ matrix.suite.rubyopt }}
+          RUBY_BOX: ${{ matrix.box && '1' || '' }}
+        working-directory: rubygems
+
+    timeout-minutes: 90
+
   all-pass:
     name: All ruby-core jobs pass
 
@@ -99,6 +154,7 @@ jobs:
 
     needs:
       - ruby_core
+      - ruby_core_master
 
     runs-on: ubuntu-latest
 

From 430ec00de6a7314b66593068b08a8facc3dce1c1 Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Mon, 14 Sep 2026 18:46:51 +0900
Subject: [PATCH 06/10] Avoid -r for gems that need activation under Ruby::Box

A command line or RUBYOPT -r bypasses the RubyGems Kernel#require override under RUBY_BOX=1, so the gem is never activated. The cargo tests require inside -e instead, and the BUNDLE_CLEAN native extension example, which needs RUBYOPT -r, is skipped.

https://bugs.ruby-lang.org/issues/22295

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 spec/commands/install_spec.rb               | 4 ++++
 test/rubygems/test_gem_ext_cargo_builder.rb | 6 ++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/spec/commands/install_spec.rb b/spec/commands/install_spec.rb
index d4b88902e21e..b5e4a9aa76c7 100644
--- a/spec/commands/install_spec.rb
+++ b/spec/commands/install_spec.rb
@@ -2065,6 +2065,10 @@ def gem_make_out
   end
 
   it "preserves bundled native extensions when BUNDLE_CLEAN removes another gem" do
+    # The command-line/RUBYOPT -r bypasses gem activation under RUBY_BOX=1
+    # (https://bugs.ruby-lang.org/issues/22295)
+    skip "-r cannot activate gems under Ruby::Box" if defined?(Ruby::Box) && Ruby::Box.enabled?
+
     build_repo4 do
       build_gem "native_child", "1.0", &:add_c_extension
       build_gem "native_parent", "1.0" do |s|
diff --git a/test/rubygems/test_gem_ext_cargo_builder.rb b/test/rubygems/test_gem_ext_cargo_builder.rb
index 94673a478c4e..bf442125f275 100644
--- a/test/rubygems/test_gem_ext_cargo_builder.rb
+++ b/test/rubygems/test_gem_ext_cargo_builder.rb
@@ -111,7 +111,9 @@ def test_full_integration
         Open3.capture2e(*gem, "build", "rust_ruby_example.gemspec", "--output", built_gem)
         Open3.capture2e(*gem, "install", "--verbose", "--local", built_gem, *ARGV)
 
-        stdout_and_stderr_str, status = Open3.capture2e(env_for_subprocess, *ruby_with_rubygems_in_load_path, "-rrust_ruby_example", "-e", "puts 'Result: ' + RustRubyExample.reverse('hello world')")
+        # Require inside -e because -r bypasses gem activation under RUBY_BOX=1
+        # (https://bugs.ruby-lang.org/issues/22295)
+        stdout_and_stderr_str, status = Open3.capture2e(env_for_subprocess, *ruby_with_rubygems_in_load_path, "-e", "require 'rust_ruby_example'; puts 'Result: ' + RustRubyExample.reverse('hello world')")
         assert status.success?, stdout_and_stderr_str
         assert_match "Result: #{"hello world".reverse}", stdout_and_stderr_str
       end
@@ -134,7 +136,7 @@ def test_custom_name
         Open3.capture2e(*gem, "install", "--verbose", "--local", built_gem, *ARGV)
       end
 
-      stdout_and_stderr_str, status = Open3.capture2e(env_for_subprocess, *ruby_with_rubygems_in_load_path, "-rcustom_name", "-e", "puts 'Result: ' + CustomName.say_hello")
+      stdout_and_stderr_str, status = Open3.capture2e(env_for_subprocess, *ruby_with_rubygems_in_load_path, "-e", "require 'custom_name'; puts 'Result: ' + CustomName.say_hello")
 
       assert status.success?, stdout_and_stderr_str
       assert_match "Result: Hello world!", stdout_and_stderr_str

From ca3a38f6032a1c15d07efb3523b899118460f172 Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Mon, 14 Sep 2026 18:47:02 +0900
Subject: [PATCH 07/10] Scope the File.expand_path stub in shared_helpers_spec

A blanket stub also caught the path lookups of a lazy require of rubygems/yaml_serializer, which crashed with Errno::ENOENT under RUBY_BOX=1 with the parallel workers. These examples only need bundler/setup faked.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 spec/bundler/shared_helpers_spec.rb | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/spec/bundler/shared_helpers_spec.rb b/spec/bundler/shared_helpers_spec.rb
index 1619b0a14a59..232da4143a24 100644
--- a/spec/bundler/shared_helpers_spec.rb
+++ b/spec/bundler/shared_helpers_spec.rb
@@ -387,7 +387,11 @@
 
       before do
         ENV["RUBYOPT"] = "-r#{install_path}/bundler/setup"
-        allow(File).to receive(:expand_path).and_return("#{install_path}/bundler/setup")
+        # Only fake the resolution of bundler/setup itself. A blanket stub
+        # breaks unrelated RubyGems path lookups triggered lazily inside the
+        # example, see #set_rubyopt.
+        allow(File).to receive(:expand_path).and_call_original
+        allow(File).to receive(:expand_path).with("setup", anything).and_return("#{install_path}/bundler/setup")
         allow(Gem).to  receive(:bin_path).and_return("#{install_path}/bundler/setup")
       end
 
@@ -403,7 +407,8 @@
       let(:install_path) { "/opt/ruby with space/lib" }
 
       before do
-        allow(File).to receive(:expand_path).and_return("#{install_path}/bundler/setup")
+        allow(File).to receive(:expand_path).and_call_original
+        allow(File).to receive(:expand_path).with("setup", anything).and_return("#{install_path}/bundler/setup")
         allow(Gem).to receive(:bin_path).and_return("#{install_path}/bundler/setup")
       end
 

From c0d86f643666b6825df793940f0f78b5de9f52e9 Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Mon, 14 Sep 2026 18:47:11 +0900
Subject: [PATCH 08/10] Correct the Ruby::Box note on the extension build
 subprocess

The recursion is not in RbConfig.expand. Inside a box defined?($gvar) does not see assignments made in that box, so mkmf have_devel? never sees its own memo.

https://bugs.ruby-lang.org/issues/22283

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 lib/rubygems/ext/builder.rb | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/rubygems/ext/builder.rb b/lib/rubygems/ext/builder.rb
index b7e80d6b06bb..691bc2825da0 100644
--- a/lib/rubygems/ext/builder.rb
+++ b/lib/rubygems/ext/builder.rb
@@ -101,7 +101,9 @@ def self.run(command, results, command_name = nil, dir = Dir.pwd, env = {})
 
       require "open3"
       # Set $SOURCE_DATE_EPOCH for the subprocess.
-      # Under Ruby::Box mkmf makes RbConfig.expand recurse until SystemStackError.
+      # Under Ruby::Box defined?($gvar) does not see assignments made inside the
+      # box, so mkmf have_devel? never memoizes and recurses until SystemStackError
+      # (https://bugs.ruby-lang.org/issues/22283).
       # Drop $RUBY_BOX last so no caller can restore it.
       build_env = { "SOURCE_DATE_EPOCH" => Gem.source_date_epoch_string }.merge(env).merge("RUBY_BOX" => nil)
       # A single-element command would be parsed as a shell command line,

From f780cbd7649962e557b1eea938ed01aa9730a34d Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Mon, 14 Sep 2026 18:47:22 +0900
Subject: [PATCH 09/10] Skip the content-addressed ABI pin example on
 prerelease Ruby

Content-addressed gems pin required_ruby_version to ~> X.Y.0, which a prerelease Ruby such as 4.1.0.dev does not satisfy, so the gem is never resolved on ruby-head.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 spec/install/gemfile/content_addressable_spec.rb | 1 +
 1 file changed, 1 insertion(+)

diff --git a/spec/install/gemfile/content_addressable_spec.rb b/spec/install/gemfile/content_addressable_spec.rb
index 8493c89cc203..8b0a472413fc 100644
--- a/spec/install/gemfile/content_addressable_spec.rb
+++ b/spec/install/gemfile/content_addressable_spec.rb
@@ -509,6 +509,7 @@
 RSpec.describe "bundle install with content-addressable gems invisible to pre-4.1 RubyGems clients", :compact_index, rubygems: ">= 4.1.0.a" do
   before do
     skip "Gem::ContentAddress not available" if ruby_core?
+    skip "A prerelease Ruby does not satisfy the ~> X.Y.0 ABI pin of content-addressed gems" if Gem.ruby_version.prerelease?
   end
 
   let(:current_abi) { "#{Gem.ruby_version.segments[0]}.#{Gem.ruby_version.segments[1]}" }

From ec7b4fb3a5a5063297a525dec2d2c0a831c73d45 Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Tue, 15 Sep 2026 13:30:27 +0900
Subject: [PATCH 10/10] Skip ruby-core tests when ruby/ruby fails to build

A broken ruby/ruby build is not something this repository can fix, so it should not fail the required check for every pull request.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 .github/workflows/ruby-core.yml | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ruby-core.yml b/.github/workflows/ruby-core.yml
index 3ff91a5d72e4..59a72ba11d65 100644
--- a/.github/workflows/ruby-core.yml
+++ b/.github/workflows/ruby-core.yml
@@ -40,12 +40,19 @@ jobs:
           sudo apt-get update -q || :
           sudo apt-get install --no-install-recommends -q -y build-essential libssl-dev libyaml-dev libreadline6-dev zlib1g-dev libncurses5-dev libffi-dev libgdbm-dev bison autoconf
       - name: Build Ruby
+        id: build
         run: |
           export GNUMAKEFLAGS="-j$((1 + $(nproc)))"
           ./autogen.sh
           ./configure -C --disable-install-doc
           make
         working-directory: ruby/ruby
+        continue-on-error: true
+      - name: Skip tests when ruby/ruby does not build
+        run: echo "::warning::ruby/ruby ${BRANCH} failed to build, so the tests were skipped"
+        env:
+          BRANCH: ${{ matrix.branch }}
+        if: steps.build.outcome == 'failure'
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           path: rubygems/rubygems
@@ -84,13 +91,13 @@ jobs:
       - name: Test RubyGems
         run: make -s test-all TESTS="--no-retry -j$((1 + $(nproc)))"
         working-directory: ruby/ruby
-        if: matrix.target == 'Rubygems'
+        if: steps.build.outcome == 'success' && matrix.target == 'Rubygems'
       - name: Test Bundler
         run: |
           git add .
           make test-bundler-parallel
         working-directory: ruby/ruby
-        if: matrix.target == 'Bundler'
+        if: steps.build.outcome == 'success' && matrix.target == 'Bundler'
 
   ruby_core_master:
     name: ${{ matrix.suite.name }} on a ruby-core master build${{ matrix.box && ' (RUBY_BOX=1)' || '' }}
@@ -119,6 +126,7 @@ jobs:
           sudo apt-get update -q || :
           sudo apt-get install --no-install-recommends -q -y build-essential libssl-dev libyaml-dev libreadline6-dev zlib1g-dev libncurses5-dev libffi-dev libgdbm-dev bison autoconf
       - name: Build and install Ruby
+        id: build
         run: |
           export GNUMAKEFLAGS="-j$((1 + $(nproc)))"
           ./autogen.sh
@@ -127,6 +135,10 @@ jobs:
           make install
           echo "$RUNNER_TEMP/ruby/bin" >> "$GITHUB_PATH"
         working-directory: ruby/ruby
+        continue-on-error: true
+      - name: Skip tests when ruby/ruby does not build
+        run: echo "::warning::ruby/ruby master failed to build, so the tests were skipped"
+        if: steps.build.outcome == 'failure'
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           path: rubygems
@@ -138,12 +150,14 @@ jobs:
         env:
           RUBYOPT: ${{ matrix.suite.rubyopt }}
         working-directory: rubygems
+        if: steps.build.outcome == 'success'
       - name: Run Test
         run: bin/rake ${{ matrix.suite.task }}
         env:
           RUBYOPT: ${{ matrix.suite.rubyopt }}
           RUBY_BOX: ${{ matrix.box && '1' || '' }}
         working-directory: rubygems
+        if: steps.build.outcome == 'success'
 
     timeout-minutes: 90