diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index ab97a81..ab6f8e4 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -15,9 +15,8 @@ jobs:
     - name: Set up Ruby
       uses: ruby/setup-ruby@4c56a21280b36d862b5fc31348f463d60bdc55d5 # ruby/setup-ruby@v1 see https://github.com/ruby/setup-ruby/tree/v1
       with:
-        ruby-version: 3.0
+        ruby-version: 4.0
     - name: Install dependencies
       run: bundle install
     - name: Run RuboCop against BASE..HEAD changes
       run: bundle exec rake rubocop:diff origin/${GITHUB_BASE_REF#*/}
-
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 34b2639..c12ac70 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -8,35 +8,20 @@ jobs:
       fail-fast: false
       matrix:
         ruby-version:
-          - '3.0'
-          - '3.1'
           - '3.2'
           - '3.3'
           - '3.4'
+          - '4.0'
         gemfile:
-          - gemfiles/Gemfile.rails61
-          - gemfiles/Gemfile.rails70
           - gemfiles/Gemfile.rails71
           - gemfiles/Gemfile.rails72
           - gemfiles/Gemfile.rails80
+          - gemfiles/Gemfile.rails81
         exclude:
-          # rails 6.1 requires ruby < 3.4
-          - ruby-version: '3.4'
-            gemfile: 'gemfiles/Gemfile.rails61'
-          # rails 7.0 requires ruby >= 2.7, < 3.4
+          # rails 8.1 requires ruby >= 3.2
           # https://www.fastruby.io/blog/ruby/rails/versions/compatibility-table.html
-          - ruby-version: '3.4'
-            gemfile: 'gemfiles/Gemfile.rails70'
-          # rails 7.2 requires ruby >= 3.1
-          # https://www.fastruby.io/blog/ruby/rails/versions/compatibility-table.html
-          - ruby-version: '3.0'
-            gemfile: 'gemfiles/Gemfile.rails72'
-          # rails 8.0 requires ruby >= 3.2
-          # https://www.fastruby.io/blog/ruby/rails/versions/compatibility-table.html
-          - ruby-version: '3.0'
-            gemfile: 'gemfiles/Gemfile.rails80'
           - ruby-version: '3.1'
-            gemfile: 'gemfiles/Gemfile.rails80'
+            gemfile: 'gemfiles/Gemfile.rails81'
 
     name: Ruby ${{ matrix.ruby-version }} / Bundle ${{ matrix.gemfile }}
 
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 3ab9213..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,24 +0,0 @@
-language: ruby
-gemfile:
-- gemfiles/Gemfile.rails52
-- gemfiles/Gemfile.rails60
-rvm:
-- 2.5
-- 2.6
-- 2.7
-- 3.0
-jobs:
-  exclude:
-  - rvm: 3.0
-    gemfile: gemfiles/Gemfile.rails52
-sudo: false
-cache: bundler
-before_install:
-- gem update --system
-- gem install bundler
-script:
-- bundle exec rake test
-notifications:
-  slack:
-    rooms:
-      secure: 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
diff --git a/CHANGELOG.md b/CHANGELOG.md
index a1bad18..311f24e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## [Unreleased]
-* no unreleased changes *
+### Fixed
+* Support Rails 8.1, Ruby 4.0
 
 ## 5.0.4 / 2025-10-22
 ### Fixed
diff --git a/gemfiles/Gemfile.rails61 b/gemfiles/Gemfile.rails61
deleted file mode 100644
index 8fdb206..0000000
--- a/gemfiles/Gemfile.rails61
+++ /dev/null
@@ -1,12 +0,0 @@
-source 'https://rubygems.org'
-
-gemspec path: '..'
-
-gem 'rails', '~> 6.1.0'
-
-# Rails 6.1 does not support sqlite3 2.x; it specifies gem "sqlite3", "~> 1.4"
-# in lib/active_record/connection_adapters/sqlite3_adapter.rb
-gem 'sqlite3', '~> 1.7'
-
-# Latest concurrent-ruby breaks Rails < 7.1. See https://github.com/rails/rails/issues/54260
-gem 'concurrent-ruby', '1.3.4'
diff --git a/gemfiles/Gemfile.rails70 b/gemfiles/Gemfile.rails70
deleted file mode 100644
index a35c58c..0000000
--- a/gemfiles/Gemfile.rails70
+++ /dev/null
@@ -1,12 +0,0 @@
-source 'https://rubygems.org'
-
-gemspec path: '..'
-
-gem 'rails',  '~> 7.0.0'
-
-# Rails 7.0 does not support sqlite3 2.x; it specifies gem "sqlite3", "~> 1.4"
-# in lib/active_record/connection_adapters/sqlite3_adapter.rb
-gem 'sqlite3', '~> 1.7'
-
-# Latest concurrent-ruby breaks Rails < 7.1. See https://github.com/rails/rails/issues/54260
-gem 'concurrent-ruby', '1.3.4'
diff --git a/gemfiles/Gemfile.rails81 b/gemfiles/Gemfile.rails81
new file mode 100644
index 0000000..c268b54
--- /dev/null
+++ b/gemfiles/Gemfile.rails81
@@ -0,0 +1,5 @@
+source 'https://rubygems.org'
+
+gemspec path: '..'
+
+gem 'rails',  '~> 8.1.0'
diff --git a/ndr_ui.gemspec b/ndr_ui.gemspec
index 004b4a3..20dd2c2 100644
--- a/ndr_ui.gemspec
+++ b/ndr_ui.gemspec
@@ -1,11 +1,6 @@
 $LOAD_PATH.push File.expand_path('lib', __dir__)
 require 'ndr_ui/version'
 
-unless Gem::Version.new(Gem::VERSION) >= Gem::Version.new('3.0.2')
-  # See https://github.com/rubygems/rubygems/pull/2516 for details
-  raise 'Please update RubyGems to at least 3.0.2 - lower versions build a broken ndr_ui.gem!'
-end
-
 # We list development dependencies for all Rails versions here.
 # Rails version-specific dependencies can go in the relevant Gemfile.
 # rubocop:disable Gemspec/DevelopmentDependencies
@@ -21,14 +16,14 @@ Gem::Specification.new do |spec|
   spec.license       = 'MIT'
 
   spec.files = Dir['{app,config,lib,vendor}/**/*', 'CHANGELOG.md', 'CODE_OF_CONDUCT.md',
-                   'LICENSE.txt', 'Rakefile', 'README.md'] - ['.travis.yml']
+                   'LICENSE.txt', 'Rakefile', 'README.md']
 
-  spec.required_ruby_version = '>= 3.0.0'
+  spec.required_ruby_version = '>= 3.2.0'
 
   spec.add_dependency 'bootstrap', '~> 5.3.3'
   spec.add_dependency 'dartsass-sprockets'
   spec.add_dependency 'jquery-rails', '~> 4.6'
-  spec.add_dependency 'rails', '>= 6.1', '< 8.1'
+  spec.add_dependency 'rails', '>= 7.1', '< 8.2'
   spec.add_dependency 'sprockets', '>= 4.0'
   spec.add_dependency 'sprockets-rails', '>= 3.0.0'
 
@@ -37,21 +32,8 @@ Gem::Specification.new do |spec|
   # cf. gemfiles/Gemfile.rails70
   spec.add_development_dependency 'sqlite3'
 
-  # Workaround build issue on GitHub Actions with ruby <= 3.1 when installing sass-embedded
-  # gem version 1.81.0: NoMethodError: undefined method `parse' for #<Psych::Parser...>
-  # https://bugs.ruby-lang.org/issues/19371
-  spec.add_development_dependency 'psych', '< 5'
-
-  # Workaround build issue on GitHub Actions with ruby <= 3.1 when installing sass-embedded
-  # Versions 1.77.0 and above require ruby >= 3.2 for packaged x86_64-linux binaries
-  # but say they're compatible with ruby 3.1.
-  # 1.76.0 has a bug that was fixed in 1.77.1, which we can't use yet.
-  # https://github.com/sass/dart-sass/issues/2239
-  spec.add_development_dependency 'sass-embedded', '~> 1.75.0' if RUBY_VERSION.start_with?('3.1') # rubocop:disable Gemspec/RubyVersionGlobalsUsage
-
-  spec.add_development_dependency 'mocha', '~> 2.0'
+  spec.add_development_dependency 'mocha', '~> 3.0'
   spec.add_development_dependency 'ndr_dev_support', '>= 6.0'
-  spec.add_development_dependency 'net-smtp'
   spec.add_development_dependency 'pry'
   spec.add_development_dependency 'puma'
   spec.add_development_dependency 'rake'
diff --git a/test/test_helper.rb b/test/test_helper.rb
index fe8b739..ea7b975 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -15,11 +15,11 @@
 Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each { |f| require f }
 
 # Load fixtures from the engine
-if ActiveSupport::TestCase.respond_to?(:fixture_path=)
-  ActiveSupport::TestCase.fixture_path = File.expand_path('../fixtures', __FILE__)
-  ActionDispatch::IntegrationTest.fixture_path = ActiveSupport::TestCase.fixture_path
-  ActiveSupport::TestCase.fixtures :all
-end
+fixtures_dir = File.expand_path('fixtures', __dir__)
+ActiveSupport::TestCase.fixture_paths << fixtures_dir # Rails >= 7.1
+ActionDispatch::IntegrationTest.fixture_paths << fixtures_dir
+ActiveSupport::TestCase.file_fixture_path = "#{fixtures_dir}/files"
+ActiveSupport::TestCase.fixtures :all
 
 # Include all capybara + poltergeist config
 ENV['INTEGRATION_DRIVER'] ||= 'chrome_headless'