diff --git a/lib/rubygems/commands/push_command.rb b/lib/rubygems/commands/push_command.rb
index 90d2d57b1ab0..42005315168b 100644
--- a/lib/rubygems/commands/push_command.rb
+++ b/lib/rubygems/commands/push_command.rb
@@ -170,7 +170,9 @@ def platform_matches?(spec)
   end
 
   def ruby_matches?(spec)
-    !options[:ruby_abi] || spec.ruby_abi == options[:ruby_abi]
+    return true unless options[:ruby_abi]
+
+    Gem::ContentAddress.applicable?(spec) && spec.ruby_abi == options[:ruby_abi]
   end
 
   def send_push_request(name, args)
diff --git a/lib/rubygems/source.rb b/lib/rubygems/source.rb
index bf86bef09856..90255c227032 100644
--- a/lib/rubygems/source.rb
+++ b/lib/rubygems/source.rb
@@ -406,6 +406,7 @@ def content_addressable_metadata(name, rows)
       requirements = compact_index_requirements(info_row)
       platform = required_platform_from(requirements[:platform])
       next unless platform
+      next unless requirements[:ruby]
 
       ContentAddressableInfo.new(version, suffix, ruby_abi_from(requirements[:ruby]), platform)
     end
diff --git a/spec/install/gemfile/content_addressable_spec.rb b/spec/install/gemfile/content_addressable_spec.rb
index a2a09bbe250a..c8fe3ee168fd 100644
--- a/spec/install/gemfile/content_addressable_spec.rb
+++ b/spec/install/gemfile/content_addressable_spec.rb
@@ -168,7 +168,7 @@
     end
   end
 
-  it "falls back to the pure-ruby gem when the content-addressed fat gem requires a different Ruby ABI" do
+  it "falls back to the pure-ruby gem when the content-addressed gem requires a different Ruby ABI" do
     simulate_platform "x86_64-linux" do
       build_repo2 do
         build_gem "mygem", "1.0" do |s|
@@ -242,4 +242,96 @@
       expect(the_bundle).to include_gems "mygem 2.0 not_content_addressed"
     end
   end
+
+  it "falls back to the non-content-addressed gem when all content-addressed gems require a different Ruby ABI" do
+    simulate_platform "x86_64-linux" do
+      build_repo2 do
+        build_gem "mygem", "1.0" do |s|
+          s.platform = Gem::Platform.new("x86_64-linux")
+          s.write "lib/mygem.rb", "MYGEM = '1.0 not_content_addressed'"
+        end
+      end
+
+      build_gem "mygem", "1.0", ruby_abi: mismatched_abi, path: gem_repo2("gems") do |s|
+        s.platform = Gem::Platform.new("x86_64-linux")
+        s.required_ruby_version = "~> #{mismatched_abi}.0"
+        s.write "lib/mygem.rb", "MYGEM = '1.0 content_addressed_mismatched_abi_1'"
+      end
+
+      second_mismatched_abi = "#{Gem.ruby_version.segments[0] + 2}.0"
+      build_gem "mygem", "1.0", ruby_abi: second_mismatched_abi, path: gem_repo2("gems") do |s|
+        s.platform = Gem::Platform.new("x86_64-linux")
+        s.required_ruby_version = "~> #{second_mismatched_abi}.0"
+        s.write "lib/mygem.rb", "MYGEM = '1.0 content_addressed_mismatched_abi_2'"
+      end
+
+      install_gemfile <<~G, artifice: "compact_index_v2", env: { "BUNDLER_SPEC_GEM_REPO" => gem_repo2.to_s }
+        source "https://gem.repo2"
+
+        gem "mygem"
+      G
+
+      expect(the_bundle).to include_gems "mygem 1.0 not_content_addressed"
+    end
+  end
+
+  it "installs a locked content-addressed gem in frozen mode" do
+    simulate_platform "x86_64-linux" do
+      build_repo2 do
+        build_gem "mygem", "1.0" do |s|
+          s.platform = Gem::Platform.new("x86_64-linux")
+          s.write "lib/mygem.rb", "MYGEM = '1.0 not_content_addressed'"
+        end
+      end
+
+      build_gem "mygem", "1.0", ruby_abi: current_abi, path: gem_repo2("gems") do |s|
+        s.platform = Gem::Platform.new("x86_64-linux")
+        s.required_ruby_version = "~> #{current_abi}.0"
+        s.write "lib/mygem.rb", "MYGEM = '1.0 content_addressed'"
+      end
+
+      install_gemfile <<~G, artifice: "compact_index_v2", env: { "BUNDLER_SPEC_GEM_REPO" => gem_repo2.to_s }
+        source "https://gem.repo2"
+
+        gem "mygem"
+      G
+
+      expect(the_bundle).to include_gems "mygem 1.0 content_addressed"
+
+      pristine_system_gems
+      bundle_config "frozen true"
+      bundle "install", artifice: "compact_index_v2", env: { "BUNDLER_SPEC_GEM_REPO" => gem_repo2.to_s }
+
+      expect(the_bundle).to include_gems "mygem 1.0 content_addressed"
+    end
+  end
+
+  it "fails when the downloaded content-addressed gem hash does not match the filename" do
+    simulate_platform "x86_64-linux" do
+      build_repo2 do
+        build_gem "mygem", "1.0" do |s|
+          s.platform = Gem::Platform.new("x86_64-linux")
+          s.write "lib/mygem.rb", "MYGEM = '1.0 not_content_addressed'"
+        end
+      end
+
+      build_gem "mygem", "1.0", ruby_abi: current_abi, path: gem_repo2("gems") do |s|
+        s.platform = Gem::Platform.new("x86_64-linux")
+        s.required_ruby_version = "~> #{current_abi}.0"
+        s.write "lib/mygem.rb", "MYGEM = '1.0 content_addressed'"
+      end
+
+      ca_gem = Dir[gem_repo2("gems", "mygem-1.0-[0-9a-f]*.gem")].first
+      non_ca_gem = gem_repo2("gems", "mygem-1.0-x86_64-linux.gem")
+      FileUtils.cp non_ca_gem, ca_gem
+
+      install_gemfile <<~G, artifice: "compact_index_v2", env: { "BUNDLER_SPEC_GEM_REPO" => gem_repo2.to_s }, raise_on_error: false
+        source "https://gem.repo2"
+
+        gem "mygem"
+      G
+
+      expect(err).to include("content address mismatch")
+    end
+  end
 end
diff --git a/test/rubygems/test_gem_commands_build_command.rb b/test/rubygems/test_gem_commands_build_command.rb
index 65c90e5bc76a..aef8444a5f84 100644
--- a/test/rubygems/test_gem_commands_build_command.rb
+++ b/test/rubygems/test_gem_commands_build_command.rb
@@ -28,7 +28,7 @@ def setup
     @cmd = Gem::Commands::BuildCommand.new
   end
 
-  def test_handle_options
+  def test_handle_options_force_strict_platform
     @cmd.handle_options %w[--force --strict]
 
     assert @cmd.options[:force]
@@ -120,6 +120,156 @@ def test_execute
     util_test_build_gem @gem
   end
 
+  def test_ruby_abi_rejects_invalid_format
+    gem = util_spec "platformed_gem" do |s|
+      s.license = "AGPL-3.0-only"
+      s.files = ["README.md"]
+      s.platform = "arm64-darwin"
+    end
+
+    gemspec_file = File.join(@tempdir, gem.spec_name)
+    File.open gemspec_file, "w" do |gs|
+      gs.write gem.to_ruby
+    end
+
+    ["3", "3.4.1", "abc", "3.x"].each do |invalid|
+      @cmd.handle_options [gemspec_file, "--ruby-abi", invalid]
+      error = assert_raise(ArgumentError) do
+        use_ui @ui do
+          Dir.chdir @tempdir do
+            @cmd.execute
+          end
+        end
+      end
+      assert_match(/Ruby ABI must be in X\.Y format/, error.message)
+    end
+  end
+
+  def test_ruby_abi_rejects_ruby_platform
+    gem = util_spec "some_gem" do |s|
+      s.license = "AGPL-3.0-only"
+      s.files = ["README.md"]
+    end
+
+    gemspec_file = File.join(@tempdir, gem.spec_name)
+    File.open gemspec_file, "w" do |gs|
+      gs.write gem.to_ruby
+    end
+
+    @cmd.handle_options [gemspec_file, "--ruby-abi", "3.4"]
+    error = assert_raise(ArgumentError) do
+      use_ui @ui do
+        Dir.chdir @tempdir do
+          @cmd.execute
+        end
+      end
+    end
+    assert_match(/no platform or a Ruby platform has been set/, error.message)
+  end
+
+  def test_ruby_abi_rejects_mismatched_required_ruby_version
+    gem = util_spec "platformed_gem" do |s|
+      s.license = "AGPL-3.0-only"
+      s.files = ["README.md"]
+      s.platform = "arm64-darwin"
+      s.required_ruby_version = "~> 3.3.0"
+    end
+
+    gemspec_file = File.join(@tempdir, gem.spec_name)
+    File.open gemspec_file, "w" do |gs|
+      gs.write gem.to_ruby
+    end
+
+    @cmd.handle_options [gemspec_file, "--ruby-abi", "3.4"]
+    error = assert_raise(ArgumentError) do
+      use_ui @ui do
+        Dir.chdir @tempdir do
+          @cmd.execute
+        end
+      end
+    end
+    assert_match(/Cannot build gem for Ruby ABI 3\.4 because required_ruby_version/, error.message)
+  end
+
+  def test_ruby_abi_defaults_required_ruby_version_when_unset
+    gem = util_spec "platformed_gem" do |s|
+      s.license = "AGPL-3.0-only"
+      s.files = ["README.md"]
+      s.platform = "arm64-darwin"
+    end
+
+    gemspec_file = File.join(@tempdir, gem.spec_name)
+    File.open gemspec_file, "w" do |gs|
+      gs.write gem.to_ruby
+    end
+
+    @cmd.handle_options [gemspec_file, "--ruby-abi", "3.4"]
+    use_ui @ui do
+      Dir.chdir @tempdir do
+        @cmd.execute
+      end
+    end
+
+    files = Dir[File.join(@tempdir, "platformed_gem-2-*.gem")]
+    assert_equal 1, files.size
+    spec = Gem::Package.new(files.first).spec
+    assert_equal Gem::Requirement.new("~> 3.4.0"), spec.required_ruby_version
+  end
+
+  def test_ruby_abi_produces_deterministic_content_address
+    gemspec = lambda do
+      gem = util_spec "platformed_gem" do |s|
+        s.license = "AGPL-3.0-only"
+        s.files = ["README.md"]
+        s.platform = "arm64-darwin"
+        s.required_ruby_version = "~> 3.4.0"
+      end
+
+      gemspec_file = File.join(@tempdir, gem.spec_name)
+      File.open gemspec_file, "w" do |gs|
+        gs.write gem.to_ruby
+      end
+
+      @cmd.handle_options [gemspec_file, "--ruby-abi", "3.4"]
+      use_ui @ui do
+        Dir.chdir @tempdir do
+          @cmd.execute
+        end
+      end
+
+      Dir[File.join(@tempdir, "platformed_gem-2-*.gem")].first
+    end
+
+    first_build = gemspec.call
+    second_build = gemspec.call
+
+    assert_equal File.basename(first_build), File.basename(second_build)
+  end
+
+  def test_ruby_abi_with_output_raises
+    gem = util_spec "platformed_gem" do |s|
+      s.license = "AGPL-3.0-only"
+      s.files = ["README.md"]
+      s.platform = "arm64-darwin"
+      s.required_ruby_version = "~> 3.4.0"
+    end
+
+    gemspec_file = File.join(@tempdir, gem.spec_name)
+    File.open gemspec_file, "w" do |gs|
+      gs.write gem.to_ruby
+    end
+
+    @cmd.handle_options [gemspec_file, "--ruby-abi", "3.4", "--output", "test.gem"]
+    error = assert_raise(ArgumentError) do
+      use_ui @ui do
+        Dir.chdir @tempdir do
+          @cmd.execute
+        end
+      end
+    end
+    assert_match(/Cannot specify both a Ruby ABI and an output file name/, error.message)
+  end
+
   def test_execute_platform
     gemspec_file = File.join(@tempdir, @gem.spec_name)
 
diff --git a/test/rubygems/test_gem_commands_info_command.rb b/test/rubygems/test_gem_commands_info_command.rb
index 9e2f5238bd61..4f2ee5084e36 100644
--- a/test/rubygems/test_gem_commands_info_command.rb
+++ b/test/rubygems/test_gem_commands_info_command.rb
@@ -198,6 +198,132 @@ def test_execute_remote_content_addressable_and_platform_gems_display_together
     refute_match "fedcba98", @ui.output
   end
 
+  def test_execute_remote_content_addressable_gem_displays_multiple_ruby_abis_on_same_platform
+    spec_fetcher {}
+
+    spec = util_spec "a", "1" do |s|
+      s.platform = "x86_64-linux"
+      s.summary = "this is a summary"
+      s.homepage = "http://example.com"
+      s.authors = ["A User"]
+    end
+    spec.content_address = "abcdef12"
+
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-abcdef12,1-fedcba98 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+    @fetcher.data["#{@gem_repo}info/a"] = util_compact_index_response(<<~INFO)
+      ---
+      1-abcdef12 |checksum:123,ruby:~> 3.3.0,platform:= x86_64-linux
+      1-fedcba98 |checksum:456,ruby:~> 3.4.0,platform:= x86_64-linux
+    INFO
+
+    path = "#{@gem_repo}quick/Marshal.#{Gem.marshal_version}/a-1-abcdef12.gemspec.rz"
+    @fetcher.data[path] = Zlib::Deflate.deflate(Marshal.dump(spec))
+    path = "#{@gem_repo}quick/Marshal.#{Gem.marshal_version}/a-1-fedcba98.gemspec.rz"
+    @fetcher.data[path] = Zlib::Deflate.deflate(Marshal.dump(spec))
+    Gem::SpecFetcher.fetcher = nil
+
+    @cmd.handle_options %w[a --remote]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    assert_include @ui.output, "Platforms:\n"
+    assert_include @ui.output, "x86_64-linux Ruby ABI: 3.3, 3.4\n"
+    refute_match "abcdef12", @ui.output
+    refute_match "fedcba98", @ui.output
+  end
+
+  def test_execute_remote_content_addressable_platform_and_source_gems_display_together
+    spec_fetcher {}
+
+    spec = util_spec "a", "3" do |s|
+      s.platform = "arm64-darwin"
+      s.summary = "this is a summary"
+      s.homepage = "http://example.com"
+      s.authors = ["A User"]
+    end
+    spec.content_address = "fedcba98"
+
+    spec_source = util_spec "a", "4" do |s|
+      s.summary = "this is a summary"
+      s.homepage = "http://example.com"
+      s.authors = ["A User"]
+    end
+
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-x86_64-linux,2-abcdef12,3-fedcba98,4 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+    @fetcher.data["#{@gem_repo}info/a"] = util_compact_index_response(<<~INFO)
+      ---
+      2-abcdef12 |checksum:123,ruby:~> 3.3.0,platform:= x86_64-linux
+      3-fedcba98 |checksum:456,ruby:~> 3.4.0,platform:= arm64-darwin
+    INFO
+
+    path = "#{@gem_repo}quick/Marshal.#{Gem.marshal_version}/a-3-fedcba98.gemspec.rz"
+    @fetcher.data[path] = Zlib::Deflate.deflate(Marshal.dump(spec))
+    path = "#{@gem_repo}quick/Marshal.#{Gem.marshal_version}/a-4.gemspec.rz"
+    @fetcher.data[path] = Zlib::Deflate.deflate(Marshal.dump(spec_source))
+    Gem::SpecFetcher.fetcher = nil
+
+    @cmd.handle_options %w[a --remote --all]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    assert_include @ui.output, "a (4, 3, 2, 1)"
+    assert_include @ui.output, "Platforms:\n"
+    assert_include @ui.output, "        1: x86_64-linux\n"
+    assert_include @ui.output, "        2: x86_64-linux Ruby ABI: 3.3\n"
+    assert_include @ui.output, "        3: arm64-darwin Ruby ABI: 3.4\n"
+    refute_match "        4:", @ui.output
+    refute_match "abcdef12", @ui.output
+    refute_match "fedcba98", @ui.output
+  end
+
+  def test_execute_remote_platform_gem_displays_version_once_for_multiple_platforms
+    spec_fetcher {}
+
+    spec_e1 = util_spec "e", "1" do |s|
+      s.platform = "x86_64-linux"
+      s.summary = "summary e"
+      s.homepage = "http://example.com"
+      s.authors = ["E User"]
+    end
+
+    spec_e2 = util_spec "e", "1" do |s|
+      s.platform = "arm64-darwin"
+      s.summary = "summary e"
+      s.homepage = "http://example.com"
+      s.authors = ["E User"]
+    end
+
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\ne 1-x86_64-linux,1-arm64-darwin 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+
+    path = "#{@gem_repo}quick/Marshal.#{Gem.marshal_version}/e-1-x86_64-linux.gemspec.rz"
+    @fetcher.data[path] = Zlib::Deflate.deflate(Marshal.dump(spec_e1))
+    path = "#{@gem_repo}quick/Marshal.#{Gem.marshal_version}/e-1-arm64-darwin.gemspec.rz"
+    @fetcher.data[path] = Zlib::Deflate.deflate(Marshal.dump(spec_e2))
+    Gem::SpecFetcher.fetcher = nil
+
+    @cmd.handle_options %w[e --remote]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    assert_include @ui.output, "e (1)"
+    assert_include @ui.output, "Platforms: arm64-darwin, x86_64-linux\n"
+  end
+
   def test_execute_with_version_flag
     spec_fetcher do |fetcher|
       fetcher.spec "coolgem", "1.0"
diff --git a/test/rubygems/test_gem_commands_list_command.rb b/test/rubygems/test_gem_commands_list_command.rb
index 2ee58cdf28ef..d35bc7021e2f 100644
--- a/test/rubygems/test_gem_commands_list_command.rb
+++ b/test/rubygems/test_gem_commands_list_command.rb
@@ -192,7 +192,7 @@ def test_execute_remote_content_addressable_gems_displays_multiple_versions_on_s
   def test_execute_remote_content_addressable_and_platform_gems_display_together
     spec_fetcher {}
 
-    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-x86_64-linux,2-abcdef12,3-fedcba98 0000\n"
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-x86_64-linux,2-abcdef12,3-fedcba98,4 0000\n"
     versions_response = util_compact_index_response(versions_body)
     versions_response.uri = Gem::URI("#{@gem_repo}versions")
     @fetcher.data["#{@gem_repo}versions"] = versions_response
@@ -210,7 +210,8 @@ def test_execute_remote_content_addressable_and_platform_gems_display_together
     end
 
     expected = <<~OUTPUT.chomp
-      a (3 Platform: arm64-darwin, Ruby ABI: 3.4
+      a (4
+         3 Platform: arm64-darwin, Ruby ABI: 3.4
          2 Platform: x86_64-linux, Ruby ABI: 3.3
          1 Platform: x86_64-linux)
     OUTPUT
diff --git a/test/rubygems/test_gem_commands_push_command.rb b/test/rubygems/test_gem_commands_push_command.rb
index 768edb32f373..48cff376c8b1 100644
--- a/test/rubygems/test_gem_commands_push_command.rb
+++ b/test/rubygems/test_gem_commands_push_command.rb
@@ -238,12 +238,12 @@ def test_execute_with_same_name_version_platform_selects_matching_ruby_abi
     assert_equal Gem.read_binary(ruby_34_path), @fetcher.last_request.body
   end
 
-  def test_execute_with_fat_and_skinny_candidates_selects_skinny_for_ruby_abi
-    _, fat_path = util_gem "mixed-target", "1.0.0" do |spec|
+  def test_execute_with_non_and_content_addressable_candidates_selects_content_addressable_for_ruby_abi
+    _, non_content_addressable_path = util_gem "mixed-target", "1.0.0" do |spec|
       spec.platform = "arm64-darwin"
       spec.required_ruby_version = ">= 3.1"
     end
-    _, skinny_path = util_gem "mixed-target", "1.0.0", ruby_abi: "3.4" do |spec|
+    _, content_addressable_path = util_gem "mixed-target", "1.0.0", ruby_abi: "3.4" do |spec|
       spec.files = ["lib/mixed-target.rb"]
       spec.platform = "arm64-darwin"
     end
@@ -251,18 +251,18 @@ def test_execute_with_fat_and_skinny_candidates_selects_skinny_for_ruby_abi
     @response = "Successfully registered gem: mixed-target (1.0.0)"
     @fetcher.data["#{Gem.host}/api/v1/gems"] = HTTPResponseFactory.create(body: @response, code: 200, msg: "OK")
 
-    @cmd.options[:args] = [fat_path, skinny_path]
+    @cmd.options[:args] = [non_content_addressable_path, content_addressable_path]
     @cmd.options[:platform] = "arm64-darwin"
     @cmd.options[:ruby_abi] = "3.4"
 
     @cmd.execute
 
     assert_equal Gem::Net::HTTP::Post, @fetcher.last_request.class
-    assert_equal Gem.read_binary(skinny_path), @fetcher.last_request.body
+    assert_equal Gem.read_binary(content_addressable_path), @fetcher.last_request.body
   end
 
-  def test_execute_with_ruby_abi_selector_does_not_match_broad_ruby_requirement
-    _, gem_path = util_gem "broad-ruby", "1.0.0" do |spec|
+  def test_execute_with_ruby_abi_selector_does_not_match_non_content_addressable_ruby_requirement
+    _, gem_path = util_gem "non-content-addressable-ruby", "1.0.0" do |spec|
       spec.platform = "arm64-darwin"
       spec.required_ruby_version = ">= 3.1"
     end
@@ -365,16 +365,16 @@ def test_execute_with_ruby_abi_selector_raises_when_multiple_platforms_match
   end
 
   def test_execute_with_platform_selector_suggests_exact_filename_for_gem_without_ruby_abi
-    _, fat_path = util_gem "ambiguous-fat", "1.0.0" do |spec|
+    _, non_content_addressable_path = util_gem "ambiguous-non-content-addressable", "1.0.0" do |spec|
       spec.platform = "arm64-darwin"
       spec.required_ruby_version = ">= 3.1"
     end
-    _, skinny_path = util_gem "ambiguous-fat", "1.0.0", ruby_abi: "3.4" do |spec|
-      spec.files = ["lib/ambiguous-fat.rb"]
+    _, content_addressable_path = util_gem "ambiguous-non-content-addressable", "1.0.0", ruby_abi: "3.4" do |spec|
+      spec.files = ["lib/ambiguous-non-content-addressable.rb"]
       spec.platform = "arm64-darwin"
     end
 
-    @cmd.options[:args] = [fat_path, skinny_path]
+    @cmd.options[:args] = [non_content_addressable_path, content_addressable_path]
     @cmd.options[:platform] = "arm64-darwin"
 
     error = assert_raise Gem::CommandLineError do
@@ -382,8 +382,8 @@ def test_execute_with_platform_selector_suggests_exact_filename_for_gem_without_
     end
 
     assert_match "Multiple gems matched platform arm64-darwin", error.message
-    assert_match fat_path, error.message
-    assert_match skinny_path, error.message
+    assert_match non_content_addressable_path, error.message
+    assert_match content_addressable_path, error.message
     assert_match "Specify --ruby-abi with one of: 3.4", error.message
     assert_match "To push a gem without a Ruby ABI, pass the exact filename.", error.message
   end
@@ -403,6 +403,86 @@ def test_execute_without_selectors_still_rejects_multiple_gems
     assert_match "Too many gem names", error.message
   end
 
+  def test_execute_with_both_selectors_raises_when_multiple_gems_match_without_suggestion
+    _, first_path = util_gem "dual-ambiguous-one", "1.0.0", ruby_abi: "3.4" do |spec|
+      spec.files = ["lib/dual-ambiguous-one.rb"]
+      spec.platform = "arm64-darwin"
+    end
+    _, second_path = util_gem "dual-ambiguous-two", "1.0.0", ruby_abi: "3.4" do |spec|
+      spec.files = ["lib/dual-ambiguous-two.rb"]
+      spec.platform = "arm64-darwin"
+    end
+
+    @cmd.options[:args] = [first_path, second_path]
+    @cmd.options[:platform] = "arm64-darwin"
+    @cmd.options[:ruby_abi] = "3.4"
+
+    error = assert_raise Gem::CommandLineError do
+      @cmd.execute
+    end
+
+    assert_match "Multiple gems matched platform arm64-darwin and Ruby ABI 3.4", error.message
+    assert_match first_path, error.message
+    assert_match second_path, error.message
+    refute_match(/Specify/, error.message)
+  end
+
+  def test_execute_with_both_selectors_selects_single_matching_gem
+    _, matching_path = util_gem "dual-match", "1.0.0", ruby_abi: "3.4" do |spec|
+      spec.files = ["lib/dual-match.rb"]
+      spec.platform = "arm64-darwin"
+    end
+
+    @response = "Successfully registered gem: dual-match (1.0.0)"
+    @fetcher.data["#{Gem.host}/api/v1/gems"] = HTTPResponseFactory.create(body: @response, code: 200, msg: "OK")
+
+    @cmd.options[:args] = [matching_path]
+    @cmd.options[:platform] = "arm64-darwin"
+    @cmd.options[:ruby_abi] = "3.4"
+
+    @cmd.execute
+
+    assert_equal Gem::Net::HTTP::Post, @fetcher.last_request.class
+    assert_equal Gem.read_binary(matching_path), @fetcher.last_request.body
+  end
+
+  def test_execute_with_platform_selector_selects_single_non_content_addressable_gem
+    _, non_content_addressable_path = util_gem "non-content-addressable-only", "1.0.0" do |spec|
+      spec.platform = "arm64-darwin"
+      spec.required_ruby_version = ">= 3.1"
+    end
+
+    @response = "Successfully registered gem: non-content-addressable-only (1.0.0)"
+    @fetcher.data["#{Gem.host}/api/v1/gems"] = HTTPResponseFactory.create(body: @response, code: 200, msg: "OK")
+
+    @cmd.options[:args] = [non_content_addressable_path]
+    @cmd.options[:platform] = "arm64-darwin"
+
+    @cmd.execute
+
+    assert_equal Gem::Net::HTTP::Post, @fetcher.last_request.class
+    assert_equal Gem.read_binary(non_content_addressable_path), @fetcher.last_request.body
+  end
+
+  def test_execute_with_ruby_abi_selector_rejects_source_gem
+    _, source_path = util_gem "source-ruby", "1.0.0" do |spec|
+      spec.files = ["lib/source-ruby.rb"]
+      spec.required_ruby_version = "~> 3.4.0"
+    end
+
+    @response = "Successfully registered gem: source-ruby (1.0.0)"
+    @fetcher.data["#{Gem.host}/api/v1/gems"] = HTTPResponseFactory.create(body: @response, code: 200, msg: "OK")
+
+    @cmd.options[:args] = [source_path]
+    @cmd.options[:ruby_abi] = "3.4"
+
+    error = assert_raise(Gem::CommandLineError) do
+      @cmd.execute
+    end
+
+    assert_match(/No gem matched/, error.message)
+  end
+
   def test_execute_attestation
     @response = "Successfully registered gem: freewill (1.0.0)"
     @fetcher.data["#{Gem.host}/api/v1/gems"] = HTTPResponseFactory.create(body: @response, code: 200, msg: "OK")
diff --git a/test/rubygems/test_gem_commands_search_command.rb b/test/rubygems/test_gem_commands_search_command.rb
index cb7bdbc83d40..2bbe7f4a5578 100644
--- a/test/rubygems/test_gem_commands_search_command.rb
+++ b/test/rubygems/test_gem_commands_search_command.rb
@@ -112,4 +112,142 @@ def test_execute_content_addressable_and_platform_gems_display_together
     refute_match "abcdef12", @ui.output
     refute_match "fedcba98", @ui.output
   end
+
+  def test_execute_content_addressable_gems_displays_ruby_abis_next_to_their_platforms
+    spec_fetcher {}
+
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-abcdef12,1-fedcba98 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+    @fetcher.data["#{@gem_repo}info/a"] = util_compact_index_response(<<~INFO)
+      ---
+      1-abcdef12 |checksum:123,ruby:~> 3.3.0,platform:= x86_64-linux
+      1-fedcba98 |checksum:456,ruby:~> 3.4.0,platform:= arm64-darwin
+    INFO
+    Gem::SpecFetcher.fetcher = nil
+
+    @cmd.handle_options %w[a]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    expected = <<~OUTPUT.chomp
+      a (1 Platform: arm64-darwin, Ruby ABI: 3.4
+         1 Platform: x86_64-linux, Ruby ABI: 3.3)
+    OUTPUT
+
+    assert_include @ui.output, expected
+    refute_match "abcdef12", @ui.output
+    refute_match "fedcba98", @ui.output
+  end
+
+  def test_execute_content_addressable_gems_displays_multiple_ruby_abis_on_the_same_line
+    spec_fetcher {}
+
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-abcdef12,1-fedcba98 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+    @fetcher.data["#{@gem_repo}info/a"] = util_compact_index_response(<<~INFO)
+      ---
+      1-abcdef12 |checksum:123,ruby:~> 3.3.0,platform:= x86_64-linux
+      1-fedcba98 |checksum:456,ruby:~> 3.4.0,platform:= x86_64-linux
+    INFO
+    Gem::SpecFetcher.fetcher = nil
+
+    @cmd.handle_options %w[a]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    assert_include @ui.output, "a (1 Platform: x86_64-linux, Ruby ABI: 3.3, 3.4)"
+    refute_match "abcdef12", @ui.output
+    refute_match "fedcba98", @ui.output
+  end
+
+  def test_execute_content_addressable_gems_displays_multiple_versions_on_separate_lines
+    spec_fetcher {}
+
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-abcdef12,2-fedcba98,3-12345678 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+    @fetcher.data["#{@gem_repo}info/a"] = util_compact_index_response(<<~INFO)
+      ---
+      1-abcdef12 |checksum:123,ruby:~> 3.3.0,platform:= x86_64-linux
+      2-fedcba98 |checksum:456,ruby:~> 3.4.0,platform:= x86_64-linux
+      3-12345678 |checksum:789,ruby:~> 3.4.0,platform:= arm64-darwin
+    INFO
+    Gem::SpecFetcher.fetcher = nil
+
+    @cmd.handle_options %w[a]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    expected = <<~OUTPUT.chomp
+      a (3 Platform: arm64-darwin, Ruby ABI: 3.4
+         2 Platform: x86_64-linux, Ruby ABI: 3.4
+         1 Platform: x86_64-linux, Ruby ABI: 3.3)
+    OUTPUT
+
+    assert_include @ui.output, expected
+    refute_match "abcdef12", @ui.output
+    refute_match "fedcba98", @ui.output
+    refute_match "12345678", @ui.output
+  end
+
+  def test_execute_platform_gem_displays_version_once_for_multiple_platforms
+    spec_fetcher {}
+
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\ne 1-x86_64-linux,1-arm64-darwin 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+    Gem::SpecFetcher.fetcher = nil
+
+    @cmd.handle_options %w[e]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    assert_include @ui.output, "e (1 arm64-darwin x86_64-linux)"
+  end
+
+  def test_execute_content_addressable_platform_and_source_gems_display_together
+    spec_fetcher {}
+
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-x86_64-linux,2-abcdef12,3-fedcba98,4 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+    @fetcher.data["#{@gem_repo}info/a"] = util_compact_index_response(<<~INFO)
+      ---
+      2-abcdef12 |checksum:123,ruby:~> 3.3.0,platform:= x86_64-linux
+      3-fedcba98 |checksum:456,ruby:~> 3.4.0,platform:= arm64-darwin
+    INFO
+    Gem::SpecFetcher.fetcher = nil
+
+    @cmd.handle_options %w[a --all]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    expected = <<~OUTPUT.chomp
+      a (4
+         3 Platform: arm64-darwin, Ruby ABI: 3.4
+         2 Platform: x86_64-linux, Ruby ABI: 3.3
+         1 Platform: x86_64-linux)
+    OUTPUT
+
+    assert_include @ui.output, expected
+    refute_match "abcdef12", @ui.output
+    refute_match "fedcba98", @ui.output
+  end
 end
diff --git a/test/rubygems/test_gem_commands_yank_command.rb b/test/rubygems/test_gem_commands_yank_command.rb
index ce7db6585c8a..5fbfdeeaaa3d 100644
--- a/test/rubygems/test_gem_commands_yank_command.rb
+++ b/test/rubygems/test_gem_commands_yank_command.rb
@@ -122,6 +122,33 @@ def test_execute_with_ruby_abi_without_platform_sends_ruby_abi_to_yank_api
     assert_equal [yank_uri], @fetcher.paths
   end
 
+  def test_execute_with_ruby_abi_and_platform_no_matching_gem_displays_error
+    original_platforms = Gem.platforms.dup
+    yank_uri = "http://example/api/v1/gems/yank"
+    @fetcher.data[yank_uri] = HTTPResponseFactory.create(
+      body: "The version 1.0 (x86_64-linux) (Ruby ABI 3.9) does not exist.",
+      code: 404,
+      msg: "Not Found"
+    )
+
+    @cmd.options[:args] = %w[a]
+    @cmd.options[:version] = req("= 1.0")
+    @cmd.options[:ruby_abi] = "3.9"
+    Gem.platforms = [Gem::Platform::RUBY, Gem::Platform.new("x86_64-linux")]
+    @cmd.options[:added_platform] = true
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    body = @fetcher.last_request.body.split("&").sort
+    assert_equal %w[gem_name=a platform=x86_64-linux ruby_abi=3.9 version=1.0], body
+    assert_match(/The version 1\.0 \(x86_64-linux\) \(Ruby ABI 3\.9\) does not exist/, @ui.output)
+    assert_equal [yank_uri], @fetcher.paths
+  ensure
+    Gem.platforms = original_platforms
+  end
+
   def test_execute_with_otp_success
     response_fail = "You have enabled multifactor authentication but your request doesn't have the correct OTP code. Please check it and retry."
     yank_uri = "http://example/api/v1/gems/yank"
diff --git a/test/rubygems/test_gem_content_address.rb b/test/rubygems/test_gem_content_address.rb
index 3b98d9024e88..d89355049ce4 100644
--- a/test/rubygems/test_gem_content_address.rb
+++ b/test/rubygems/test_gem_content_address.rb
@@ -5,10 +5,14 @@
 
 class TestGemContentAddress < Gem::TestCase
   def test_match
-    assert Gem::ContentAddress.match?("abcdef12")
+    assert Gem::ContentAddress.match?("78be552b")
     refute Gem::ContentAddress.match?("x86_64-linux")
     refute Gem::ContentAddress.match?(nil)
-    refute Gem::ContentAddress.match?("abc")
+    refute Gem::ContentAddress.match?("")
+    refute Gem::ContentAddress.match?(0xabcdef12)
+    refute Gem::ContentAddress.match?(:abcdef12)
+    refute Gem::ContentAddress.match?("abcdef12 ")
+    refute Gem::ContentAddress.match?(" abcdef12")
   end
 
   def test_match_boundary_lengths
@@ -63,6 +67,14 @@ def test_content_addressed_with_eligible_spec_and_no_address
     refute Gem::ContentAddress.content_addressed?(spec)
   end
 
+  def test_content_addressed_with_eligible_spec_and_invalid_address
+    spec = Gem::Specification.new "a", 1
+    spec.required_ruby_version = ">= 3.0"
+    spec.platform = "x86_64-linux"
+    spec.content_address = "x86_64-linux"
+    refute Gem::ContentAddress.content_addressed?(spec)
+  end
+
   def test_content_addressed_with_ineligible_spec_and_valid_address
     spec = Gem::Specification.new "a", 1
     spec.content_address = "abcdef12"
diff --git a/test/rubygems/test_gem_installer.rb b/test/rubygems/test_gem_installer.rb
index 83258ed4d2a2..741eed1ea1d5 100644
--- a/test/rubygems/test_gem_installer.rb
+++ b/test/rubygems/test_gem_installer.rb
@@ -1050,6 +1050,7 @@ def test_install_assigns_content_address_from_filename
     assert_equal address, spec.content_address
     assert_equal "a-2-#{address}", spec.full_name
     assert_path_exist File.join(@gemhome, "gems", "a-2-#{address}")
+    assert_path_exist File.join(@gemhome, "cache", "a-2-#{address}.gem")
     assert_path_exist File.join(@gemhome, "specifications", "a-2-#{address}.gemspec")
   end
 
@@ -1209,6 +1210,68 @@ def test_reinstalling_content_addressed_gem_is_idempotent
     assert_equal 1, Dir[File.join(@gemhome, "specifications", "a-2*.gemspec")].size
   end
 
+  def test_install_assigns_content_address_from_filename_with_full_sha
+    _, a_gem = util_gem("a", 2) do |spec|
+      spec.required_ruby_version = ">= 3.0"
+      spec.platform = "x86_64-linux"
+    end
+
+    digest = Digest::SHA256.file(a_gem).hexdigest
+    dir = File.dirname(a_gem)
+    filename = File.join(dir, "a-2-#{digest}.gem")
+    FileUtils.cp a_gem, filename
+    installer = Gem::Installer.at filename, install_dir: @gemhome, force: true
+    spec = installer.install
+
+    assert_equal digest, spec.content_address
+    assert_equal "a-2-#{digest}", spec.full_name
+    assert_path_exist File.join(@gemhome, "gems", "a-2-#{digest}")
+    assert_path_exist File.join(@gemhome, "cache", "a-2-#{digest}.gem")
+    assert_path_exist File.join(@gemhome, "specifications", "a-2-#{digest}.gemspec")
+  end
+
+  def test_two_content_addressed_gems_with_same_name_version_coexist
+    _, gem1 = util_gem("a", 2) do |spec|
+      spec.required_ruby_version = ">= 3.0"
+      spec.platform = "x86_64-linux"
+      spec.summary = "variant 1"
+    end
+    gem1_backup = File.join(@tempdir, "gem1_backup.gem")
+    FileUtils.cp gem1, gem1_backup
+
+    _, gem2 = util_gem("a", 2) do |spec|
+      spec.required_ruby_version = ">= 3.0"
+      spec.platform = "x86_64-linux"
+      spec.summary = "variant 2"
+    end
+
+    FileUtils.rm_rf File.join(@gemhome, "gems", "a-2-x86_64-linux")
+    FileUtils.rm_rf File.join(@gemhome, "specifications", "a-2-x86_64-linux.gemspec")
+    Gem::Specification.reset
+
+    dir = File.dirname(gem1)
+    digest1 = Digest::SHA256.file(gem1_backup).hexdigest
+    digest2 = Digest::SHA256.file(gem2).hexdigest
+    refute_equal digest1, digest2
+
+    address1 = digest1[0, 8]
+    address2 = digest2[0, 8]
+    file1 = File.join(dir, "a-2-#{address1}.gem")
+    file2 = File.join(dir, "a-2-#{address2}.gem")
+    FileUtils.cp gem1_backup, file1
+    FileUtils.cp gem2, file2
+
+    Gem::Installer.at(file1, install_dir: @gemhome, force: true).install
+    Gem::Installer.at(file2, install_dir: @gemhome, force: true).install
+
+    assert_path_exist File.join(@gemhome, "gems", "a-2-#{address1}")
+    assert_path_exist File.join(@gemhome, "gems", "a-2-#{address2}")
+    assert_path_exist File.join(@gemhome, "specifications", "a-2-#{address1}.gemspec")
+    assert_path_exist File.join(@gemhome, "specifications", "a-2-#{address2}.gemspec")
+    assert_equal 2, Dir[File.join(@gemhome, "gems", "a-2-*")].size
+    assert_equal 2, Dir[File.join(@gemhome, "specifications", "a-2-*.gemspec")].size
+  end
+
   def test_install
     installer = util_setup_installer
 
diff --git a/test/rubygems/test_gem_name_tuple.rb b/test/rubygems/test_gem_name_tuple.rb
index ec4d48ac98db..276a002dfb3f 100644
--- a/test/rubygems/test_gem_name_tuple.rb
+++ b/test/rubygems/test_gem_name_tuple.rb
@@ -54,7 +54,7 @@ def test_content_addressable_metadata
     assert_equal "a-1-abcdef12", n.full_name
   end
 
-  def test_fat_tuple_does_not_store_nil_content_addressable_metadata_ivars
+  def test_non_content_addressable_tuple_does_not_store_nil_content_addressable_metadata_ivars
     n = Gem::NameTuple.new "a", Gem::Version.new(1), "x86_64-linux"
 
     refute_includes n.instance_variables, :@content_address
@@ -63,11 +63,11 @@ def test_fat_tuple_does_not_store_nil_content_addressable_metadata_ivars
     assert_nil n.ruby_abi
   end
 
-  def test_sort_mixed_fat_and_content_addressable_tuples
-    fat = Gem::NameTuple.new "a", Gem::Version.new(1), "x86_64-linux"
-    skinny = Gem::NameTuple.new "a", Gem::Version.new(1), "x86_64-linux", content_address: "abcdef12", ruby_abi: "3.3"
+  def test_sort_mixed_non_content_addressable_and_content_addressable_tuples
+    non_content_addressable = Gem::NameTuple.new "a", Gem::Version.new(1), "x86_64-linux"
+    content_addressable = Gem::NameTuple.new "a", Gem::Version.new(1), "x86_64-linux", content_address: "abcdef12", ruby_abi: "3.3"
 
-    assert_equal [fat, skinny], [skinny, fat].sort
+    assert_equal [non_content_addressable, content_addressable], [content_addressable, non_content_addressable].sort
   end
 
   def test_spec_name
diff --git a/test/rubygems/test_gem_package.rb b/test/rubygems/test_gem_package.rb
index e89155aeef4b..fe5505a70afb 100644
--- a/test/rubygems/test_gem_package.rb
+++ b/test/rubygems/test_gem_package.rb
@@ -257,6 +257,52 @@ def test_ruby_abi_creates_content_addressed_file
     assert_match(/\Aplatformed-1-[0-9a-f]{8}\.gem\z/, built_file)
   end
 
+  def test_ruby_abi_built_gem_preserves_derived_metadata
+    spec = Gem::Specification.new "platformed", "1"
+    spec.summary = "platformed"
+    spec.authors = "platformed"
+    spec.files = ["lib/code.rb"]
+    spec.platform = "arm64-darwin"
+    spec.required_ruby_version = Gem::Requirement.new("~> 3.4.0")
+
+    FileUtils.mkdir "lib"
+
+    File.open "lib/code.rb", "w" do |io|
+      io.write "# lib/code.rb"
+    end
+
+    built_file = Gem::Package.build(spec, false, false, nil, "3.4")
+
+    loaded_spec = Gem::Package.new(built_file).spec
+    assert_equal "platformed", loaded_spec.name
+    assert_equal Gem::Version.new("1"), loaded_spec.version
+    assert_equal Gem::Platform.new("arm64-darwin"), loaded_spec.platform
+    assert_equal Gem::Requirement.new("~> 3.4.0"), loaded_spec.required_ruby_version
+    assert_equal "3.4", loaded_spec.ruby_abi
+  end
+
+  def test_required_ruby_version_unchanged_after_successful_matching_build
+    spec = Gem::Specification.new "platformed", "1"
+    spec.summary = "platformed"
+    spec.authors = "platformed"
+    spec.files = ["lib/code.rb"]
+    spec.platform = "arm64-darwin"
+    spec.required_ruby_version = Gem::Requirement.new("~> 3.4.0")
+
+    FileUtils.mkdir "lib"
+
+    File.open "lib/code.rb", "w" do |io|
+      io.write "# lib/code.rb"
+    end
+
+    original_rrv = spec.required_ruby_version
+
+    Gem::Package.build(spec, false, false, nil, "3.4")
+
+    assert_equal original_rrv, spec.required_ruby_version
+    assert_equal Gem::Requirement.new("~> 3.4.0"), spec.required_ruby_version
+  end
+
   def test_ruby_abi_not_passed_does_not_create_content_addressed_file
     spec = Gem::Specification.new "platformed", "1"
     spec.summary = "platformed"
diff --git a/test/rubygems/test_gem_resolver.rb b/test/rubygems/test_gem_resolver.rb
index 269869cd4c96..c251899b488e 100644
--- a/test/rubygems/test_gem_resolver.rb
+++ b/test/rubygems/test_gem_resolver.rb
@@ -336,19 +336,19 @@ def test_prefers_content_addressed_gem_for_same_platform
     assert_resolves_to [ca_spec], resolver
   end
 
-  def test_falls_back_to_fat_when_content_addressed_gem_requires_other_rubygems_version
+  def test_falls_back_to_non_content_addressable_when_content_addressed_gem_requires_other_rubygems_version
     ca_spec = util_spec "a", "1"
-    fat_spec = util_spec "a", "1"
+    non_content_addressable_spec = util_spec "a", "1"
 
     ca_spec.platform = Gem::Platform.local
     ca_spec.content_address = "abc1234567"
     ca_spec.required_rubygems_version = ">= 999"
-    fat_spec.platform = Gem::Platform.local
+    non_content_addressable_spec.platform = Gem::Platform.local
 
-    s = set(fat_spec, ca_spec)
+    s = set(non_content_addressable_spec, ca_spec)
     dependency = make_dep "a"
     resolver = Gem::Resolver.new([dependency], s)
-    assert_resolves_to [fat_spec], resolver
+    assert_resolves_to [non_content_addressable_spec], resolver
   end
 
   def test_falls_back_to_source_when_content_addressed_gem_requires_other_ruby
@@ -366,21 +366,56 @@ def test_falls_back_to_source_when_content_addressed_gem_requires_other_ruby
     assert_resolves_to [source_spec], resolver
   end
 
-  def test_falls_back_to_fat_before_source_when_content_addressed_gem_requires_other_ruby
+  def test_falls_back_to_non_content_addressable_before_source_when_content_addressed_gem_requires_other_ruby
     ca_spec = util_spec "a", "1"
-    fat_spec = util_spec "a", "1"
+    non_content_addressable_spec = util_spec "a", "1"
     source_spec = util_spec "a", "1"
 
     ca_spec.platform = Gem::Platform.local
     ca_spec.content_address = "abc1234567"
     ca_spec.required_ruby_version = ">= 999"
-    fat_spec.platform = Gem::Platform.local
+    non_content_addressable_spec.platform = Gem::Platform.local
     source_spec.platform = Gem::Platform::RUBY
 
-    s = set(source_spec, fat_spec, ca_spec)
+    s = set(source_spec, non_content_addressable_spec, ca_spec)
     dependency = make_dep "a"
     resolver = Gem::Resolver.new([dependency], s)
-    assert_resolves_to [fat_spec], resolver
+    assert_resolves_to [non_content_addressable_spec], resolver
+  end
+
+  def test_prefers_compatible_content_addressed_gem_when_multiple_abis_available
+    current_abi = "#{Gem.ruby_version.segments[0]}.#{Gem.ruby_version.segments[1]}"
+
+    ca_compatible = util_spec "a", "1"
+    ca_incompatible = util_spec "a", "1"
+
+    ca_compatible.platform = Gem::Platform.local
+    ca_compatible.content_address = "abc1234567"
+    ca_compatible.required_ruby_version = "~> #{current_abi}.0"
+    ca_incompatible.platform = Gem::Platform.local
+    ca_incompatible.content_address = "def1234567"
+    ca_incompatible.required_ruby_version = "~> 999.0.0"
+
+    s = set(ca_incompatible, ca_compatible)
+    dependency = make_dep "a"
+    resolver = Gem::Resolver.new([dependency], s)
+    assert_resolves_to [ca_compatible], resolver
+  end
+
+  def test_raises_when_only_content_addressed_gem_is_incompatible
+    ca_spec = util_spec "a", "1"
+
+    ca_spec.platform = Gem::Platform.local
+    ca_spec.content_address = "abc1234567"
+    ca_spec.required_ruby_version = "~> 999.0.0"
+
+    s = set(ca_spec)
+    dependency = make_dep "a"
+    resolver = Gem::Resolver.new([dependency], s)
+
+    assert_raise Gem::DependencyResolutionError do
+      resolver.resolve
+    end
   end
 
   def test_does_not_pick_musl_variants_on_non_musl_linux
diff --git a/test/rubygems/test_gem_source.rb b/test/rubygems/test_gem_source.rb
index 2bde66d2e771..d72bf05315a1 100644
--- a/test/rubygems/test_gem_source.rb
+++ b/test/rubygems/test_gem_source.rb
@@ -263,6 +263,38 @@ def test_decode_content_addressable_tuples_latest_groups_by_gem_name_before_plat
     assert_equal %w[aa-7.1-aaaa1111 ab-1.5-bbbb2222 ac-6.4-cccc3333 ad-1.16-dddd4444], specs.map(&:full_name).sort
   end
 
+  def test_load_specs_compact_index_decodes_mixed_content_addressable_and_platform_entries
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-abcdef12,1-x86_64-linux 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+    @fetcher.data["#{@gem_repo}info/a"] = util_compact_index_response("---\n1-abcdef12 |checksum:123,ruby:~> 3.3.0,platform:= x86_64-linux\n")
+
+    specs = @source.load_specs(:released)
+    decoded = @source.decode_content_addressable_tuples(specs)
+
+    assert_equal 2, decoded.size
+    ca_spec = decoded.find {|s| s.content_address == "abcdef12" }
+    platform_spec = decoded.find {|s| s.content_address.nil? }
+    assert_equal "a-1-abcdef12", ca_spec.full_name
+    assert_equal "x86_64-linux", ca_spec.platform
+    assert_equal "3.3", ca_spec.ruby_abi
+    assert_equal "a-1-x86_64-linux", platform_spec.full_name
+    assert_nil platform_spec.ruby_abi
+  end
+
+  def test_load_specs_compact_index_skips_content_addressable_rows_without_ruby_field
+    versions_body = +"created_at: 2026-01-01T00:00:00Z\n---\na 1-abcdef12 0000\n"
+    versions_response = util_compact_index_response(versions_body)
+    versions_response.uri = Gem::URI("#{@gem_repo}versions")
+    @fetcher.data["#{@gem_repo}versions"] = versions_response
+    @fetcher.data["#{@gem_repo}info/a"] = util_compact_index_response("---\n1-abcdef12 |checksum:123,platform:= x86_64-linux\n")
+
+    specs = @source.decode_content_addressable_tuples(@source.load_specs(:released))
+
+    assert_empty specs
+  end
+
   def test_load_specs_compact_index_latest_per_platform
     a1 = util_spec "a", "1"
     a2_java = util_spec "a", "2" do |s|
diff --git a/test/rubygems/test_gem_specification.rb b/test/rubygems/test_gem_specification.rb
index 0f2126f4c914..d0c5f1eb2466 100644
--- a/test/rubygems/test_gem_specification.rb
+++ b/test/rubygems/test_gem_specification.rb
@@ -1943,6 +1943,11 @@ def test_ruby_abi_returns_nil_for_non_pessimistic_operator
     assert_nil spec.ruby_abi
   end
 
+  def test_ruby_abi_returns_nil_for_default_required_ruby_version
+    spec = Gem::Specification.new
+    assert_nil spec.ruby_abi
+  end
+
   def test_full_name
     assert_equal "a-1", @a1.full_name