diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index 266855f86..2b28b2a67 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['3.0', '3.1', '3.2']
+        ruby-version: ['3.2', '3.3']
 
     steps:
     - uses: actions/checkout@v2
diff --git a/.rubocop.yml b/.rubocop.yml
index 871542bba..67922eed2 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -27,6 +27,8 @@ Style/HashTransformKeys:
   Enabled: true
 Style/HashTransformValues:
   Enabled: true
+Style/AccessModifierDeclarations:
+  Enabled: false
 Style/ModuleFunction:
   Enabled: false
 Style/SymbolArray:
diff --git a/.ruby-version b/.ruby-version
index ef538c281..9c25013db 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.1.2
+3.3.6
diff --git a/.tool-versions b/.tool-versions
index 0b2d85878..5aa8e0c30 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1 +1 @@
-ruby 3.1.2
+ruby 3.3.6
diff --git a/Gemfile b/Gemfile
index 9bd327ec2..7365d7d0b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,6 +5,8 @@ gemspec
 
 group :development, :test do
   gem 'debug'
+  gem 'parallel', '1.26.3'
   gem 'pry'
   gem 'pry-byebug'
+  gem 'rubocop', '~> 1.86', require: false
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index 4e3a94e63..a38c868a6 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -5,34 +5,39 @@ PATH
       bcp47 (>= 0.3)
       date_time_precision (>= 0.8)
       mime-types (>= 3.0)
-      nokogiri (>= 1.11.4)
+      nokogiri (>= 1.19.1)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    ast (2.4.2)
+    ast (2.4.3)
     bcp47 (0.3.3)
       i18n
-    byebug (11.1.3)
+    byebug (13.0.0)
+      reline (>= 0.6.0)
     coderay (1.1.3)
-    concurrent-ruby (1.3.1)
+    concurrent-ruby (1.3.6)
     coolline (0.5.0)
       unicode_utils (~> 1.4)
+    date (3.5.1)
     date_time_precision (0.8.1)
-    debug (1.9.2)
+    debug (1.11.1)
       irb (~> 1.10)
       reline (>= 0.3.8)
-    diff-lcs (1.4.4)
-    docile (1.3.2)
-    ffi (1.13.1)
-    formatador (0.2.5)
-    guard (2.16.2)
+    diff-lcs (1.6.2)
+    docile (1.4.1)
+    erb (6.0.3)
+    ffi (1.17.4)
+    formatador (1.2.3)
+      reline
+    guard (2.20.1)
       formatador (>= 0.2.4)
       listen (>= 2.7, < 4.0)
+      logger (~> 1.6)
       lumberjack (>= 1.0.12, < 2.0)
       nenv (~> 0.1)
       notiffany (~> 0.0)
-      pry (>= 0.9.12)
+      pry (>= 0.13.0)
       shellany (~> 0.0)
       thor (>= 0.18.1)
     guard-compat (1.2.1)
@@ -43,84 +48,101 @@ GEM
     guard-test (2.0.8)
       guard-compat (~> 1.2)
       test-unit (~> 3.0)
-    i18n (1.14.5)
+    i18n (1.14.8)
       concurrent-ruby (~> 1.0)
-    io-console (0.7.2)
-    irb (1.13.2)
+    io-console (0.8.2)
+    irb (1.17.0)
+      pp (>= 0.6.0)
+      prism (>= 1.3.0)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
-    json (2.3.1)
-    listen (3.3.1)
+    json (2.19.4)
+    language_server-protocol (3.17.0.5)
+    lint_roller (1.1.0)
+    listen (3.10.0)
+      logger
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
-    lumberjack (1.2.8)
-    method_source (1.0.0)
-    mime-types (3.5.2)
-      mime-types-data (~> 3.2015)
-    mime-types-data (3.2024.0702)
-    mini_portile2 (2.8.6)
+    logger (1.7.0)
+    lumberjack (1.4.2)
+    method_source (1.1.0)
+    mime-types (3.7.0)
+      logger
+      mime-types-data (~> 3.2025, >= 3.2025.0507)
+    mime-types-data (3.2026.0414)
+    mini_portile2 (2.8.9)
     nenv (0.3.0)
-    nokogiri (1.16.5)
+    nokogiri (1.19.2)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
-    nokogiri-diff (0.2.0)
+    nokogiri-diff (0.3.0)
       nokogiri (~> 1.5)
-      tdiff (~> 0.3, >= 0.3.2)
+      tdiff (~> 0.4)
     notiffany (0.1.3)
       nenv (~> 0.1)
       shellany (~> 0.0)
-    parallel (1.23.0)
-    parser (3.2.2.4)
+    parallel (1.26.3)
+    parser (3.3.11.1)
       ast (~> 2.4.1)
       racc
-    power_assert (1.2.0)
-    pry (0.14.2)
+    power_assert (3.0.1)
+    pp (0.6.3)
+      prettyprint
+    prettyprint (0.2.0)
+    prism (1.9.0)
+    pry (0.16.0)
       coderay (~> 1.1)
       method_source (~> 1.0)
-    pry-byebug (3.10.1)
-      byebug (~> 11.0)
-      pry (>= 0.13, < 0.15)
-    pry-coolline (0.2.5)
+      reline (>= 0.6.0)
+    pry-byebug (3.12.0)
+      byebug (~> 13.0)
+      pry (>= 0.13, < 0.17)
+    pry-coolline (0.2.6)
       coolline (~> 0.5)
-    psych (5.1.2)
+      pry (~> 0.13)
+    psych (5.3.1)
+      date
       stringio
-    racc (1.8.0)
+    racc (1.8.1)
     rainbow (3.1.1)
-    rake (13.0.1)
-    rb-fsevent (0.10.4)
-    rb-inotify (0.10.1)
+    rake (13.4.2)
+    rb-fsevent (0.11.2)
+    rb-inotify (0.11.1)
       ffi (~> 1.0)
-    rdoc (6.7.0)
+    rdoc (7.2.0)
+      erb
       psych (>= 4.0.0)
-    regexp_parser (2.8.2)
-    reline (0.5.9)
+      tsort
+    regexp_parser (2.12.0)
+    reline (0.6.3)
       io-console (~> 0.5)
-    rexml (3.2.8)
-      strscan (>= 3.0.9)
-    rspec (3.10.0)
-      rspec-core (~> 3.10.0)
-      rspec-expectations (~> 3.10.0)
-      rspec-mocks (~> 3.10.0)
-    rspec-core (3.10.0)
-      rspec-support (~> 3.10.0)
-    rspec-expectations (3.10.0)
+    rspec (3.13.2)
+      rspec-core (~> 3.13.0)
+      rspec-expectations (~> 3.13.0)
+      rspec-mocks (~> 3.13.0)
+    rspec-core (3.13.6)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.5)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.10.0)
-    rspec-mocks (3.10.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.8)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.10.0)
-    rspec-support (3.10.0)
-    rubocop (1.23.0)
-      parallel (~> 1.10)
-      parser (>= 3.0.0.0)
+      rspec-support (~> 3.13.0)
+    rspec-support (3.13.7)
+    rubocop (1.86.1)
+      json (~> 2.3)
+      language_server-protocol (~> 3.17.0.2)
+      lint_roller (~> 1.1.0)
+      parallel (>= 1.10)
+      parser (>= 3.3.0.2)
       rainbow (>= 2.2.2, < 4.0)
-      regexp_parser (>= 1.8, < 3.0)
-      rexml
-      rubocop-ast (>= 1.12.0, < 2.0)
+      regexp_parser (>= 2.9.3, < 3.0)
+      rubocop-ast (>= 1.49.0, < 2.0)
       ruby-progressbar (~> 1.7)
-      unicode-display_width (>= 1.4.0, < 3.0)
-    rubocop-ast (1.30.0)
-      parser (>= 3.2.1.0)
+      unicode-display_width (>= 2.4.0, < 4.0)
+    rubocop-ast (1.49.1)
+      parser (>= 3.3.7.2)
+      prism (~> 1.7)
     ruby-progressbar (1.13.0)
     shellany (0.0.1)
     simplecov (0.17.1)
@@ -128,13 +150,15 @@ GEM
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    stringio (3.1.1)
-    strscan (3.1.0)
-    tdiff (0.3.4)
-    test-unit (3.3.6)
+    stringio (3.2.0)
+    tdiff (0.4.0)
+    test-unit (3.7.7)
       power_assert
-    thor (1.0.1)
-    unicode-display_width (2.5.0)
+    thor (1.5.0)
+    tsort (0.2.0)
+    unicode-display_width (3.2.0)
+      unicode-emoji (~> 4.1)
+    unicode-emoji (4.2.0)
     unicode_utils (1.4.0)
 
 PLATFORMS
@@ -147,17 +171,18 @@ DEPENDENCIES
   guard-rspec
   guard-test
   nokogiri-diff
+  parallel (= 1.26.3)
   pry
   pry-byebug
   pry-coolline
   rake
   rspec
-  rubocop (= 1.23.0)
+  rubocop (~> 1.86)
   simplecov (~> 0.17.0)
   test-unit
 
 RUBY VERSION
-   ruby 3.1.2p20
+   ruby 3.3.6p108
 
 BUNDLED WITH
-   2.2.21
+   2.3.7
diff --git a/fhir_models.gemspec b/fhir_models.gemspec
index 0ac4f527c..a24861123 100644
--- a/fhir_models.gemspec
+++ b/fhir_models.gemspec
@@ -22,7 +22,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.required_ruby_version = '>= 3.0.0'
-  spec.add_dependency 'nokogiri', '>= 1.11.4'
+  spec.add_dependency 'nokogiri', '>= 1.19.1'
   spec.add_dependency 'date_time_precision', '>= 0.8'
   spec.add_dependency 'bcp47', '>= 0.3'
   spec.add_dependency 'mime-types', '>= 3.0'
@@ -35,7 +35,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rspec'
   spec.add_development_dependency 'simplecov', '~> 0.17.0'
   spec.add_development_dependency 'nokogiri-diff'
-  spec.add_development_dependency 'rubocop', '1.23.0'
   spec.add_development_dependency 'guard-rspec'
   spec.add_development_dependency 'guard-test'
 end
diff --git a/lib/fhir_models/bootstrap/model.rb b/lib/fhir_models/bootstrap/model.rb
index 3ed4ebec3..2e6cc80bd 100644
--- a/lib/fhir_models/bootstrap/model.rb
+++ b/lib/fhir_models/bootstrap/model.rb
@@ -163,7 +163,7 @@ def validate_profile(metadata, contained = nil)
           errors.delete(typename) unless present.include?(typename)
         end
       end
-      errors.keep_if { |_k, v| (v && !v.empty?) }
+      errors.keep_if { |_k, v| v && !v.empty? }
     end
 
     # ----- validate a field -----
@@ -232,7 +232,7 @@ def validate_field(field, value, contained_here, meta, errors)
         end
         has_valid_code = false
         if meta['valid_codes']
-          meta['valid_codes'].each do |_key, codes|
+          meta['valid_codes'].each_value do |codes|
             has_valid_code = true unless (codes & the_codes).empty?
             break if has_valid_code
           end
@@ -287,7 +287,7 @@ def primitive?(datatype, value)
     def check_binding_uri(uri, value)
       valid = false
       # Strip off the |4.0.0 or |4.0.1 or |2014-03-26 or similar from the ends of URLs
-      uri&.gsub!(/\|[A-Za-z0-9.\-]*/, '')
+      uri&.gsub!(/\|[A-Za-z0-9.-]*/, '')
       valueset = versioned_fhir_module::Definitions.get_codes(uri)
 
       if ['http://hl7.org/fhir/ValueSet/mimetypes', 'http://www.rfc-editor.org/bcp/bcp13.txt'].include?(uri)
@@ -332,7 +332,7 @@ def find_extension(extension_source, method_name)
       extension_source.select do |extension|
         name = extension.url.tr('-', '_').split('/').last
         anchor = name.split('#').last
-        (method_name.to_s == name || method_name.to_s == anchor)
+        [name, anchor].include?(method_name.to_s)
       end
     end
 
diff --git a/lib/fhir_models/bootstrap/preprocess.rb b/lib/fhir_models/bootstrap/preprocess.rb
index 273e0fc6e..af960288a 100644
--- a/lib/fhir_models/bootstrap/preprocess.rb
+++ b/lib/fhir_models/bootstrap/preprocess.rb
@@ -92,7 +92,7 @@ def self.pre_process_searchparam(hash)
 
       def self.remove_fhir_comments(hash)
         hash.delete('fhir_comments')
-        hash.each do |_key, value|
+        hash.each_value do |value|
           case value
           when Hash
             remove_fhir_comments(value)
diff --git a/lib/fhir_models/fhir.rb b/lib/fhir_models/fhir.rb
index 230f19ce6..0f8dcb75b 100644
--- a/lib/fhir_models/fhir.rb
+++ b/lib/fhir_models/fhir.rb
@@ -74,7 +74,7 @@ def self.primitive?(datatype:, value:)
       !(value.to_s =~ /\A[A-Za-z0-9\-.]{1,64}\Z/).nil?
     when 'xhtml'
       fragment = Nokogiri::HTML::DocumentFragment.parse(value)
-      value.is_a?(String) && fragment.errors.size.zero?
+      value.is_a?(String) && fragment.errors.empty?
     when 'unsignedint'
       !(value.to_s =~ /\A(0|([1-9][0-9]*))\Z/).nil?
     when 'positiveint'
diff --git a/lib/fhir_models/fhir_ext/common_structure_definition.rb b/lib/fhir_models/fhir_ext/common_structure_definition.rb
index 42e8c0e1e..dc607d32b 100644
--- a/lib/fhir_models/fhir_ext/common_structure_definition.rb
+++ b/lib/fhir_models/fhir_ext/common_structure_definition.rb
@@ -78,7 +78,7 @@ def valid_json?(json)
         verify_element(element, json)
       end
 
-      @errors.size.zero?
+      @errors.empty?
     end
     deprecate :is_valid_json?, :valid_json?
 
@@ -410,7 +410,7 @@ def check_binding_element(element, value)
       if ['http://hl7.org/fhir/ValueSet/mimetypes', 'http://www.rfc-editor.org/bcp/bcp13.txt'].include?(vs_uri)
         matches = MIME::Types[value]
         known_weird = ['text/cql', 'application/cql+text', 'application/hl7-v2'].include?(value)
-        if (matches.nil? || matches.size.zero? || known_weird) && !some_type_of_xml_or_json?(value)
+        if (matches.nil? || matches.empty? || known_weird) && !some_type_of_xml_or_json?(value)
           @errors << "#{element.path} has invalid mime-type: '#{value}'"
           matching_type -= 1 if element.binding.strength == 'required'
         end
diff --git a/lib/fhir_models/fhir_ext/common_structure_definition_compare.rb b/lib/fhir_models/fhir_ext/common_structure_definition_compare.rb
index 3599c4fd6..bd7aa1b35 100644
--- a/lib/fhir_models/fhir_ext/common_structure_definition_compare.rb
+++ b/lib/fhir_models/fhir_ext/common_structure_definition_compare.rb
@@ -140,7 +140,7 @@ def compatible?(another_definition)
       end
       @errors.flatten!
       @warnings.flatten!
-      @errors.size.zero?
+      @errors.empty?
     end
     deprecate :is_compatible?, :compatible?
 
@@ -225,7 +225,7 @@ def compare_extension_definition(x, y, another_definition)
       x_only = x_profiles - y_profiles
       shared = x_profiles - x_only
 
-      if !shared.nil? && shared.size.zero?
+      if !shared.nil? && shared.empty?
         # same name, but different profiles
         # maybe the profiles are the same, just with different URLs...
         # ... so we have to compare them, if we can.
@@ -269,7 +269,7 @@ def compare_element_definitions(x, y, another_definition)
       y_only = y_types - x_types
       shared = x_types - x_only
 
-      if !shared.nil? && shared.size.zero? && !x_types.empty? && !y_types.empty? && !x.constraint.empty? && !y.constraint.empty?
+      if !shared.nil? && shared.empty? && !x_types.empty? && !y_types.empty? && !x.constraint.empty? && !y.constraint.empty?
         @errors << @finding.error(x.path.to_s, 'type.code', 'Incompatible data types', x_types.to_s, y_types.to_s)
       end
       if !x_only.nil? && !x_only.empty?
@@ -359,7 +359,7 @@ def compare_element_definitions(x, y, another_definition)
       y_only = y_constraints - x_constraints
       shared = x_constraints - x_only
 
-      if !shared.nil? && shared.size.zero? && !x.constraint.empty? && !y.constraint.empty?
+      if !shared.nil? && shared.empty? && !x.constraint.empty? && !y.constraint.empty?
         @errors << @finding.error(x.path.to_s, 'constraint.xpath', 'Incompatible constraints', x_constraints.map { |z| z.tr(',', ';') }.join(' && ').to_s, y_constraints.map { |z| z.tr(',', ';') }.join(' && ').to_s)
       end
       if !x_only.nil? && !x_only.empty?
diff --git a/lib/fhir_models/fhirpath/parse.rb b/lib/fhir_models/fhirpath/parse.rb
index 676946a70..6b93a449d 100644
--- a/lib/fhir_models/fhirpath/parse.rb
+++ b/lib/fhir_models/fhirpath/parse.rb
@@ -36,7 +36,7 @@ def self.tokenize(expression)
     end
     # we may need to reassemble quoted strings again
     reassemble_strings(tokens)
-    tokens.delete_if { |token| (token.length.zero? || (token.is_a?(String) && token.match(/\S/).nil?)) }
+    tokens.delete_if { |token| token.empty? || (token.is_a?(String) && token.match(/\S/).nil?) }
     FHIR.logger.debug "TOKENS: #{tokens}"
     tokens
   end
diff --git a/lib/fhir_models/generator/class_generator.rb b/lib/fhir_models/generator/class_generator.rb
index fe0c016ba..2a8b7fe75 100644
--- a/lib/fhir_models/generator/class_generator.rb
+++ b/lib/fhir_models/generator/class_generator.rb
@@ -96,7 +96,7 @@ def generate_class(hierarchy, structure_def, top_level: false)
           if !element['type'].nil?
             # profiles contains a list of profiles if the datatype is Reference or Extension
             profiles = []
-            element['type'].select { |t| t['code'] == 'Reference' || t['code'] == 'Extension' }.each do |data_type|
+            element['type'].select { |t| ['Reference', 'Extension'].include?(t['code']) }.each do |data_type|
               profiles << data_type['targetProfile']
             end
             profiles.reject!(&:nil?)
diff --git a/lib/fhir_models/generator/ig_resources.rb b/lib/fhir_models/generator/ig_resources.rb
index 3e644374f..c193ffea8 100644
--- a/lib/fhir_models/generator/ig_resources.rb
+++ b/lib/fhir_models/generator/ig_resources.rb
@@ -124,7 +124,7 @@ def get_codes(url)
               end
             end
           end
-          transformed_expansion[url].each { |_system, codes| codes.uniq! }
+          transformed_expansion[url].each_value(&:uniq!)
         end
         transformed_expansion[url]
       end
diff --git a/test/unit/profile_validation_test.rb b/test/unit/profile_validation_test.rb
index 4dd7dadfd..404c7bf8a 100644
--- a/test/unit/profile_validation_test.rb
+++ b/test/unit/profile_validation_test.rb
@@ -1,4 +1,5 @@
 require_relative '../test_helper'
+require 'ostruct'
 
 class ProfileValidationTest < Test::Unit::TestCase
   ERROR_DIR = File.join('tmp', 'errors', 'ProfileValidationTest')