diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 4a8b7b4..6eebee5 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,20 +1,45 @@
 name: Ruby
 
-on: [push,pull_request]
+on: [push, pull_request]
 
 jobs:
-  build:
+  test:
     runs-on: ubuntu-latest
+    name: "rspec — Ruby ${{ matrix.ruby }} / ${{ matrix.gemfile }}"
+    strategy:
+      fail-fast: false
+      matrix:
+        # Covers the supported range from the floor (Ruby 3.2 / Rails 6.1) to
+        # the current ceiling (Ruby 3.4 / Rails 8.1). Curated pairs avoid
+        # Ruby/Rails combinations that are not mutually supported.
+        include:
+          - { ruby: "3.2", gemfile: rails_6_1 }
+          - { ruby: "3.2", gemfile: rails_7_1 }
+          - { ruby: "3.3", gemfile: rails_7_2 }
+          - { ruby: "3.3", gemfile: rails_8_0 }
+          - { ruby: "3.4", gemfile: rails_8_0 }
+          - { ruby: "3.4", gemfile: rails_8_1 }
+    env:
+      BUNDLE_GEMFILE: gemfiles/${{ matrix.gemfile }}.gemfile
     steps:
-    - uses: actions/checkout@v4
-    - name: Set up Ruby
-      uses: ruby/setup-ruby@v1
-      with:
-        ruby-version: 3.2.2
-        bundler: 4.0.4
-    - name: Bundle gems
-      run: bundle install
-    - name: Run rspec
-      run: bundle exec rspec
-    - name: Run rubocop
-      run: bundle exec rubocop
+      - uses: actions/checkout@v4
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+      - name: Run rspec
+        run: bundle exec rspec
+
+  lint:
+    runs-on: ubuntu-latest
+    name: rubocop
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: "3.2"
+          bundler-cache: true
+      - name: Run rubocop
+        run: bundle exec rubocop
diff --git a/.gitignore b/.gitignore
index b1877d2..900724a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,3 +12,6 @@
 
 # built gem files
 *.gem
+
+# per-appraisal lockfiles (resolved fresh in CI)
+gemfiles/*.gemfile.lock
diff --git a/.rubocop.yml b/.rubocop.yml
index 62233d9..4532e5d 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,9 +1,18 @@
+# Append to (rather than replace) RuboCop's default AllCops/Exclude, so the
+# defaults such as vendor/**/* stay excluded. Without this, CI installs gems
+# into vendor/bundle (bundler-cache) and RuboCop would lint third-party gems.
+inherit_mode:
+  merge:
+    - Exclude
+
 AllCops:
   TargetRubyVersion: 3.2
   NewCops: enable
   SuggestExtensions: false
   Exclude:
     - "README.md"
+    - "vendor/**/*"
+    - "gemfiles/vendor/**/*"
 
 Style/StringLiterals:
   Enabled: true
@@ -20,24 +29,6 @@ Metrics/BlockLength:
   Exclude:
     - "spec/**/*_spec.rb"
 
-Metrics/MethodLength:
-  Exclude:
-    - "lib/rspec/json_api/compare_hash.rb"
-    - "lib/extensions/hash.rb"
-
-Metrics/AbcSize:
-  Exclude:
-    - "lib/rspec/json_api/compare_hash.rb"
-    - "lib/rspec/json_api/matchers/match_json_schema.rb"
-
-Metrics/CyclomaticComplexity:
-  Exclude:
-    - "lib/rspec/json_api/compare_hash.rb"
-
-Metrics/PerceivedComplexity:
-  Exclude:
-    - "lib/rspec/json_api/compare_hash.rb"
-
 Style/Documentation:
   Enabled: false
 
@@ -47,4 +38,4 @@ Naming/PredicatePrefix:
 
 Naming/PredicateMethod:
   Exclude:
-    - "lib/rspec/json_api/compare_hash.rb"
+    - "lib/rspec/json_api/schema_match.rb"
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ce13bd0..f6a7210 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,32 @@
 ## [Unreleased]
 
+## [1.5.0] - 2026-06-05
+
+### Added
+- CI compatibility matrix across Ruby 3.2–3.4 and Rails 6.1, 7.1, 7.2, 8.0 and 8.1 (`gemfiles/` + GitHub Actions matrix), so the advertised version support is actually tested.
+- `RSpec::JsonApi::Constraints` module encapsulating the schema `Proc` options DSL.
+- `RSpec::JsonApi::SchemaMatch` as the single comparison entry point, and `RSpec::JsonApi::Traversal` for the internal structural helpers.
+
+### Changed
+- Depend on `railties` instead of the full `rails` meta-gem; the gem only uses ActiveSupport core extensions and `Rails::Generators`. Drops the dependency graph from 87 to 65 gems. The `>= 6.1.4.1` floor is unchanged.
+- Unified array and hash comparison behind `SchemaMatch`; removed the duplicate `CompareArray` and `CompareHash` modules.
+- Stopped monkey-patching core `Hash`/`Array`; `deep_keys`, `deep_key_paths`, `deep_sort` and `sanitize!` moved into the internal `Traversal` module.
+- The failure diff is now built lazily, only when a match fails.
+- An unsupported schema `Proc` option now raises `ArgumentError` instead of being silently ignored.
+- Generators emit `# frozen_string_literal: true` and freeze the generated interface hash.
+
+### Fixed
+- Require `uri` so the built-in types load on Ruby 4.0 (previously raised `NameError` on load).
+- Anchor the `UUID` type with `\A...\z` so multiline strings no longer pass validation.
+- Rescue invalid JSON in `match_json_schema` instead of raising `JSON::ParserError`.
+- Avoid a `TypeError` when a schema expects a nested object but the actual value is a scalar.
+- Enforce key structure for interface-array elements; an element with an extra null-valued key no longer matches.
+- Reset the memoized diff at the start of `matches?` so a reused matcher reflects the current actual value.
+- Use `Regexp#match?` for regex comparison so it returns a Boolean instead of a match index.
+
+### Removed
+- Dead/broken `interface.erb` generator template.
+
 ## [1.4.0] - 2026-01-23
 
 ### Changed
diff --git a/Gemfile.lock b/Gemfile.lock
index 52cba3a..bfbf2fa 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,37 +1,15 @@
 PATH
   remote: .
   specs:
-    rspec-json_api (1.4.0)
+    rspec-json_api (1.5.0)
       activesupport (>= 6.1.4.1)
       diffy (>= 3.4.2)
-      rails (>= 6.1.4.1)
+      railties (>= 6.1.4.1)
       rspec-rails (>= 5.0.2)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    action_text-trix (2.1.16)
-      railties
-    actioncable (8.1.2)
-      actionpack (= 8.1.2)
-      activesupport (= 8.1.2)
-      nio4r (~> 2.0)
-      websocket-driver (>= 0.6.1)
-      zeitwerk (~> 2.6)
-    actionmailbox (8.1.2)
-      actionpack (= 8.1.2)
-      activejob (= 8.1.2)
-      activerecord (= 8.1.2)
-      activestorage (= 8.1.2)
-      activesupport (= 8.1.2)
-      mail (>= 2.8.0)
-    actionmailer (8.1.2)
-      actionpack (= 8.1.2)
-      actionview (= 8.1.2)
-      activejob (= 8.1.2)
-      activesupport (= 8.1.2)
-      mail (>= 2.8.0)
-      rails-dom-testing (~> 2.2)
     actionpack (8.1.2)
       actionview (= 8.1.2)
       activesupport (= 8.1.2)
@@ -42,35 +20,12 @@ GEM
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
       useragent (~> 0.16)
-    actiontext (8.1.2)
-      action_text-trix (~> 2.1.15)
-      actionpack (= 8.1.2)
-      activerecord (= 8.1.2)
-      activestorage (= 8.1.2)
-      activesupport (= 8.1.2)
-      globalid (>= 0.6.0)
-      nokogiri (>= 1.8.5)
     actionview (8.1.2)
       activesupport (= 8.1.2)
       builder (~> 3.1)
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
-    activejob (8.1.2)
-      activesupport (= 8.1.2)
-      globalid (>= 0.3.6)
-    activemodel (8.1.2)
-      activesupport (= 8.1.2)
-    activerecord (8.1.2)
-      activemodel (= 8.1.2)
-      activesupport (= 8.1.2)
-      timeout (>= 0.4.0)
-    activestorage (8.1.2)
-      actionpack (= 8.1.2)
-      activejob (= 8.1.2)
-      activerecord (= 8.1.2)
-      activesupport (= 8.1.2)
-      marcel (~> 1.0)
     activesupport (8.1.2)
       base64
       bigdecimal
@@ -97,8 +52,6 @@ GEM
     drb (2.2.3)
     erb (6.0.1)
     erubi (1.13.1)
-    globalid (1.3.0)
-      activesupport (>= 6.1)
     i18n (1.14.8)
       concurrent-ruby (~> 1.0)
     io-console (0.8.2)
@@ -113,30 +66,14 @@ GEM
     loofah (2.25.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
-    mail (2.9.0)
-      logger
-      mini_mime (>= 0.1.1)
-      net-imap
-      net-pop
-      net-smtp
-    marcel (1.1.0)
-    mini_mime (1.1.5)
     minitest (6.0.1)
       prism (~> 1.5)
-    net-imap (0.6.2)
-      date
-      net-protocol
-    net-pop (0.1.2)
-      net-protocol
-    net-protocol (0.2.2)
-      timeout
-    net-smtp (0.5.1)
-      net-protocol
-    nio4r (2.7.5)
     nokogiri (1.19.0-arm64-darwin)
       racc (~> 1.4)
     nokogiri (1.19.0-x86_64-darwin)
       racc (~> 1.4)
+    nokogiri (1.19.0-x86_64-linux-gnu)
+      racc (~> 1.4)
     parallel (1.27.0)
     parser (3.3.10.1)
       ast (~> 2.4.1)
@@ -157,20 +94,6 @@ GEM
       rack (>= 1.3)
     rackup (2.3.1)
       rack (>= 3)
-    rails (8.1.2)
-      actioncable (= 8.1.2)
-      actionmailbox (= 8.1.2)
-      actionmailer (= 8.1.2)
-      actionpack (= 8.1.2)
-      actiontext (= 8.1.2)
-      actionview (= 8.1.2)
-      activejob (= 8.1.2)
-      activemodel (= 8.1.2)
-      activerecord (= 8.1.2)
-      activestorage (= 8.1.2)
-      activesupport (= 8.1.2)
-      bundler (>= 1.15.0)
-      railties (= 8.1.2)
     rails-dom-testing (2.3.0)
       activesupport (>= 5.0.0)
       minitest
@@ -231,7 +154,6 @@ GEM
     securerandom (0.4.1)
     stringio (3.2.0)
     thor (1.5.0)
-    timeout (0.6.0)
     tsort (0.2.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
@@ -240,15 +162,13 @@ GEM
     unicode-emoji (4.2.0)
     uri (1.1.1)
     useragent (0.16.11)
-    websocket-driver (0.8.0)
-      base64
-      websocket-extensions (>= 0.1.0)
-    websocket-extensions (0.1.5)
     zeitwerk (2.7.4)
 
 PLATFORMS
   arm64-darwin-22
+  arm64-darwin-25
   x86_64-darwin-20
+  x86_64-linux
 
 DEPENDENCIES
   activesupport (>= 6.1.4.1)
diff --git a/gemfiles/rails_6_1.gemfile b/gemfiles/rails_6_1.gemfile
new file mode 100644
index 0000000..3d9827d
--- /dev/null
+++ b/gemfiles/rails_6_1.gemfile
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+# Inherits the dev dependencies from the root Gemfile and pins the Rails line
+# under test. Generated/maintained for the CI compatibility matrix.
+eval_gemfile File.expand_path("../Gemfile", __dir__)
+
+gem "rails", "~> 6.1.0"
diff --git a/gemfiles/rails_7_1.gemfile b/gemfiles/rails_7_1.gemfile
new file mode 100644
index 0000000..67c9551
--- /dev/null
+++ b/gemfiles/rails_7_1.gemfile
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+# Inherits the dev dependencies from the root Gemfile and pins the Rails line
+# under test. Generated/maintained for the CI compatibility matrix.
+eval_gemfile File.expand_path("../Gemfile", __dir__)
+
+gem "rails", "~> 7.1.0"
diff --git a/gemfiles/rails_7_2.gemfile b/gemfiles/rails_7_2.gemfile
new file mode 100644
index 0000000..7380461
--- /dev/null
+++ b/gemfiles/rails_7_2.gemfile
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+# Inherits the dev dependencies from the root Gemfile and pins the Rails line
+# under test. Generated/maintained for the CI compatibility matrix.
+eval_gemfile File.expand_path("../Gemfile", __dir__)
+
+gem "rails", "~> 7.2.0"
diff --git a/gemfiles/rails_8_0.gemfile b/gemfiles/rails_8_0.gemfile
new file mode 100644
index 0000000..bab2dbc
--- /dev/null
+++ b/gemfiles/rails_8_0.gemfile
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+# Inherits the dev dependencies from the root Gemfile and pins the Rails line
+# under test. Generated/maintained for the CI compatibility matrix.
+eval_gemfile File.expand_path("../Gemfile", __dir__)
+
+gem "rails", "~> 8.0.0"
diff --git a/gemfiles/rails_8_1.gemfile b/gemfiles/rails_8_1.gemfile
new file mode 100644
index 0000000..32dba6b
--- /dev/null
+++ b/gemfiles/rails_8_1.gemfile
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+# Inherits the dev dependencies from the root Gemfile and pins the Rails line
+# under test. Generated/maintained for the CI compatibility matrix.
+eval_gemfile File.expand_path("../Gemfile", __dir__)
+
+gem "rails", "~> 8.1.0"
diff --git a/lib/extensions/array.rb b/lib/extensions/array.rb
deleted file mode 100644
index 7cf9987..0000000
--- a/lib/extensions/array.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-# frozen_string_literal: true
-
-class Array
-  def deep_sort
-    map { |element| element.is_a?(Array) ? element.deep_sort : element }
-      .sort_by { |el| el.is_a?(Array) ? el.first.to_s : el.to_s }
-  end
-end
diff --git a/lib/extensions/hash.rb b/lib/extensions/hash.rb
deleted file mode 100644
index 1303736..0000000
--- a/lib/extensions/hash.rb
+++ /dev/null
@@ -1,36 +0,0 @@
-# frozen_string_literal: true
-
-# Extension methods for hash class
-class Hash
-  def deep_keys
-    each_with_object([]) do |(k, v), keys|
-      keys << k
-      keys << v.deep_keys if v.respond_to?(:keys)
-    end
-  end
-
-  def deep_key_paths
-    stack = map { |k, v| [[k], v] }
-    key_map = []
-
-    until stack.empty?
-      key, value = stack.pop
-
-      key_map << key unless value.is_a? Hash
-
-      next unless value.is_a? Hash
-
-      value.map do |k, v|
-        stack.push [key.dup << k, v]
-      end
-    end
-
-    key_map.reverse
-  end
-
-  def sanitize!(keys)
-    keep_if do |k, _v|
-      keys.include?(k)
-    end
-  end
-end
diff --git a/lib/generators/rspec/json_api/interface/interface_generator.rb b/lib/generators/rspec/json_api/interface/interface_generator.rb
index 726a711..56bb7b5 100644
--- a/lib/generators/rspec/json_api/interface/interface_generator.rb
+++ b/lib/generators/rspec/json_api/interface/interface_generator.rb
@@ -8,12 +8,14 @@ class InterfaceGenerator < Rails::Generators::NamedBase
 
         def copy_interface_file
           create_file "spec/rspec/json_api/interfaces/#{file_name}.rb", <<~FILE
+            # frozen_string_literal: true
+
             module RSpec
               module JsonApi
                 module Interfaces
                   #{file_name.upcase} = {
                     # name: String
-                  }
+                  }.freeze
                 end
               end
             end
diff --git a/lib/generators/rspec/json_api/interface/templates/interface.erb b/lib/generators/rspec/json_api/interface/templates/interface.erb
deleted file mode 100644
index 3e5b960..0000000
--- a/lib/generators/rspec/json_api/interface/templates/interface.erb
+++ /dev/null
@@ -1,9 +0,0 @@
-<%= module RSpec %>
-  <%= module JsonApi %>
-    <%= module Interfaces %>
-      <%= const_set(file_name, {
-
-      }.freeze) %>
-    <%= end %>
-  <%= end %>
-<%= end %>
\ No newline at end of file
diff --git a/lib/generators/rspec/json_api/type/type_generator.rb b/lib/generators/rspec/json_api/type/type_generator.rb
index e78fbd5..89acc8f 100644
--- a/lib/generators/rspec/json_api/type/type_generator.rb
+++ b/lib/generators/rspec/json_api/type/type_generator.rb
@@ -8,6 +8,8 @@ class TypeGenerator < Rails::Generators::NamedBase
 
         def copy_type_file
           create_file "spec/rspec/json_api/types/#{file_name}.rb", <<~FILE
+            # frozen_string_literal: true
+
             module RSpec
               module JsonApi
                 module Types
diff --git a/lib/rspec/json_api.rb b/lib/rspec/json_api.rb
index db874ce..9ef16f7 100644
--- a/lib/rspec/json_api.rb
+++ b/lib/rspec/json_api.rb
@@ -2,17 +2,15 @@
 
 # Load 3rd party libraries
 require "json"
+require "uri"
 require "diffy"
 require "active_support/core_ext/object/blank"
 
 # Load the json_api parts
 require "rspec/json_api/version"
-require "rspec/json_api/compare_hash"
-require "rspec/json_api/compare_array"
-
-# Load extensions
-require "extensions/hash"
-require "extensions/array"
+require "rspec/json_api/traversal"
+require "rspec/json_api/constraints"
+require "rspec/json_api/schema_match"
 
 # Load matchers
 require "rspec/json_api/matchers"
diff --git a/lib/rspec/json_api/compare_array.rb b/lib/rspec/json_api/compare_array.rb
deleted file mode 100644
index 4ea9c54..0000000
--- a/lib/rspec/json_api/compare_array.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-# frozen_string_literal: true
-
-module RSpec
-  module JsonApi
-    module CompareArray
-      extend self
-
-      def compare(actual, expected)
-        if interface?(expected)
-          actual.all? do |actual_elem|
-            return false unless actual_elem.deep_keys == expected[0].deep_keys
-
-            CompareHash.compare(actual_elem, expected[0])
-          end
-        else
-          actual.each_with_index.all? do |actual_elem, index|
-            compare_primitive_type_element(actual, expected, actual_elem, index)
-          end
-        end
-      end
-
-      private
-
-      def interface?(expected_value)
-        expected_value.size == 1 && expected_value[0].is_a?(Hash)
-      end
-
-      def compare_primitive_type_element(actual, expected, actual_elem, index)
-        if actual[index].respond_to?(:deep_keys) && expected[index].respond_to?(:deep_keys)
-          return false unless actual[index].deep_keys == expected[index].deep_keys
-
-          CompareHash.compare(actual_elem, expected[index])
-        else
-          CompareHash.compare_values(actual[index], expected[index])
-        end
-      end
-    end
-  end
-end
diff --git a/lib/rspec/json_api/compare_hash.rb b/lib/rspec/json_api/compare_hash.rb
deleted file mode 100644
index 8a033a4..0000000
--- a/lib/rspec/json_api/compare_hash.rb
+++ /dev/null
@@ -1,114 +0,0 @@
-# frozen_string_literal: true
-
-module RSpec
-  module JsonApi
-    module CompareHash
-      module_function
-
-      SUPPORTED_OPTIONS = %i[allow_blank type value min max inclusion regex lambda].freeze
-
-      def compare(actual, expected)
-        return false if actual.blank? && expected.present?
-
-        keys = expected.deep_key_paths | actual.deep_key_paths
-
-        compare_key_paths_and_values(keys, actual, expected)
-      end
-
-      def compare_key_paths_and_values(keys, actual, expected)
-        keys.all? do |key_path|
-          actual_value = actual.dig(*key_path)
-          expected_value = expected.dig(*key_path)
-
-          compare_values(actual_value, expected_value)
-        end
-      end
-
-      def compare_values(actual_value, expected_value)
-        case expected_value
-        when Class
-          compare_class(actual_value, expected_value)
-        when Regexp
-          compare_regexp(actual_value, expected_value)
-        when Proc
-          compare_proc(actual_value, expected_value)
-        when Array
-          compare_array(actual_value, expected_value)
-        else
-          compare_simple_value(actual_value, expected_value)
-        end
-      end
-
-      def compare_class(actual_value, expected_value)
-        actual_value.instance_of?(expected_value)
-      end
-
-      def compare_regexp(actual_value, expected_value)
-        actual_value.to_s =~ expected_value
-      end
-
-      def compare_proc(actual_value, expected_value)
-        payload = expected_value.call
-        payload.sanitize!(SUPPORTED_OPTIONS)
-        payload = payload.sort_by { |k, _v| k == :allow_blank ? 0 : 1 }.to_h
-
-        payload.all? do |condition_key, condition_value|
-          case condition_key
-          when :allow_blank
-            return true if actual_value.blank? && condition_value
-
-            true
-          when :type
-            compare_class(actual_value, condition_value)
-          when :value
-            compare_simple_value(actual_value, condition_value)
-          when :inclusion
-            condition_value.include?(actual_value)
-          when :min
-            return false if !condition_value.is_a?(Numeric) || !actual_value.is_a?(Numeric)
-
-            actual_value >= condition_value
-          when :max
-            return false if !condition_value.is_a?(Numeric) || !actual_value.is_a?(Numeric)
-
-            actual_value <= condition_value
-          when :regex
-            compare_regexp(actual_value, condition_value)
-          when :lambda
-            condition_value.call(actual_value)
-          end
-        end
-      end
-
-      def compare_array(actual_value, expected_value)
-        if simple_type?(expected_value)
-          type = expected_value[0]
-
-          actual_value.all? { |elem| compare_class(elem, type) }
-        elsif interface?(expected_value)
-          interface = expected_value[0]
-
-          actual_value.all? { |elem| compare(elem, interface) }
-        else
-          return false if actual_value&.size != expected_value&.size
-
-          expected_value.each_with_index.all? do |elem, index|
-            elem.is_a?(Hash) ? compare(actual_value[index], elem) : compare_simple_value(actual_value[index], elem)
-          end
-        end
-      end
-
-      def compare_simple_value(actual_value, expected_value)
-        actual_value == expected_value
-      end
-
-      def simple_type?(expected_value)
-        expected_value.size == 1 && expected_value[0].instance_of?(Class)
-      end
-
-      def interface?(expected_value)
-        expected_value.size == 1 && expected_value[0].is_a?(Hash)
-      end
-    end
-  end
-end
diff --git a/lib/rspec/json_api/constraints.rb b/lib/rspec/json_api/constraints.rb
new file mode 100644
index 0000000..eb03abe
--- /dev/null
+++ b/lib/rspec/json_api/constraints.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+module RSpec
+  module JsonApi
+    # Constraints evaluates the option hash produced by a schema Proc
+    # (e.g. `-> { { type: Integer, min: 1, max: 10, allow_blank: true } }`)
+    # against an actual value.
+    #
+    # allow_blank is a modifier, not a constraint of its own: when it is true a
+    # blank value is accepted and the remaining options are skipped; otherwise
+    # the value is checked against every other option.
+    module Constraints
+      module_function
+
+      SUPPORTED_OPTIONS = %i[allow_blank type value min max inclusion regex lambda].freeze
+
+      # @param value [Object] the actual value being matched.
+      # @param options [Hash] the option hash returned by the schema Proc.
+      # @return [Boolean] true when the value satisfies the options.
+      # @raise [ArgumentError] when an option key is not supported.
+      def match(value, options)
+        validate!(options)
+
+        return true if value.blank? && options[:allow_blank]
+
+        options.except(:allow_blank).all? do |option, condition|
+          satisfies?(value, option, condition)
+        end
+      end
+
+      def validate!(options)
+        unknown = options.keys - SUPPORTED_OPTIONS
+        return if unknown.empty?
+
+        raise ArgumentError, "Unsupported match option(s): #{unknown.join(", ")}"
+      end
+
+      def satisfies?(value, option, condition)
+        case option
+        when :type      then value.instance_of?(condition)
+        when :value     then value == condition
+        when :inclusion then condition.include?(value)
+        when :regex     then condition.match?(value.to_s)
+        when :lambda    then condition.call(value)
+        when :min, :max then within_bound?(value, option, condition)
+        end
+      end
+
+      def within_bound?(value, option, condition)
+        return false unless value.is_a?(Numeric) && condition.is_a?(Numeric)
+
+        option == :min ? value >= condition : value <= condition
+      end
+    end
+  end
+end
diff --git a/lib/rspec/json_api/matchers/match_json_schema.rb b/lib/rspec/json_api/matchers/match_json_schema.rb
index fc31c8f..51626f6 100644
--- a/lib/rspec/json_api/matchers/match_json_schema.rb
+++ b/lib/rspec/json_api/matchers/match_json_schema.rb
@@ -23,18 +23,13 @@ def initialize(expected)
         # @param actual [String] The JSON string to test against the expected schema.
         # @return [Boolean] true if the actual JSON matches the expected schema, false otherwise.
         def matches?(actual)
+          @diff = nil
           @actual = JSON.parse(actual, symbolize_names: true)
-          @diff = Diffy::Diff.new(expected, @actual, context: 5)
 
-          return false unless @actual.instance_of?(expected.class)
-
-          if expected.instance_of?(Array)
-            RSpec::JsonApi::CompareArray.compare(@actual, expected)
-          else
-            return false unless @actual.deep_keys.deep_sort == expected.deep_keys.deep_sort
-
-            RSpec::JsonApi::CompareHash.compare(@actual, expected)
-          end
+          RSpec::JsonApi::SchemaMatch.match(@actual, expected)
+        rescue JSON::ParserError
+          @actual = actual
+          false
         end
 
         # Provides a failure message for when the JSON data does not match the expected schema.
@@ -45,7 +40,7 @@ def failure_message
                  got: #{actual}
 
             Diff:
-            #{@diff}
+            #{diff}
           MSG
         end
 
@@ -55,6 +50,14 @@ def failure_message
         def failure_message_when_negated
           "expected the JSON data not to match the provided schema, but it did."
         end
+
+        private
+
+        # The diff is only needed to render a failure message, so it is built
+        # lazily and memoized rather than on every matches? call.
+        def diff
+          @diff ||= Diffy::Diff.new(expected, actual, context: 5)
+        end
       end
     end
   end
diff --git a/lib/rspec/json_api/schema_match.rb b/lib/rspec/json_api/schema_match.rb
new file mode 100644
index 0000000..4fe51b2
--- /dev/null
+++ b/lib/rspec/json_api/schema_match.rb
@@ -0,0 +1,135 @@
+# frozen_string_literal: true
+
+module RSpec
+  module JsonApi
+    # SchemaMatch compares parsed JSON (a Hash, an Array, or a scalar) against an
+    # expected schema. It is the single entry point behind the match_json_schema
+    # matcher: callers hand it the actual and expected values and it dispatches on
+    # shape internally, so the matcher does not need to know whether it is looking
+    # at an object or a collection.
+    module SchemaMatch
+      module_function
+
+      # Top-level comparison. Applies the shape guards (class equality and, for
+      # objects, key-set equality) before recursing.
+      def match(actual, expected)
+        return false unless actual.instance_of?(expected.class)
+
+        case expected
+        when Array
+          compare_array(actual, expected)
+        when Hash
+          return false unless same_key_structure?(actual, expected)
+
+          compare(actual, expected)
+        else
+          compare_simple_value(actual, expected)
+        end
+      end
+
+      def same_key_structure?(actual, expected)
+        Traversal.deep_sort(Traversal.deep_keys(actual)) ==
+          Traversal.deep_sort(Traversal.deep_keys(expected))
+      end
+
+      def compare(actual, expected)
+        return false if actual.blank? && expected.present?
+
+        keys = Traversal.deep_key_paths(expected) | Traversal.deep_key_paths(actual)
+
+        compare_key_paths_and_values(keys, actual, expected)
+      end
+
+      def compare_key_paths_and_values(keys, actual, expected)
+        keys.all? do |key_path|
+          actual_value = dig_path(actual, key_path)
+          expected_value = dig_path(expected, key_path)
+
+          compare_values(actual_value, expected_value)
+        end
+      end
+
+      # Digs a key path without raising when an intermediate value is not a Hash.
+      # Plain Hash#dig raises TypeError if it walks into a scalar (e.g. a schema
+      # expects a nested object but the actual value is a String), so a mismatch
+      # would crash instead of failing the match.
+      def dig_path(data, key_path)
+        key_path.reduce(data) do |value, key|
+          break nil unless value.is_a?(Hash)
+
+          value[key]
+        end
+      end
+
+      def compare_values(actual_value, expected_value)
+        case expected_value
+        when Class  then compare_class(actual_value, expected_value)
+        when Regexp then compare_regexp(actual_value, expected_value)
+        when Proc   then compare_proc(actual_value, expected_value)
+        when Array  then compare_array(actual_value, expected_value)
+        else             compare_simple_value(actual_value, expected_value)
+        end
+      end
+
+      def compare_class(actual_value, expected_value)
+        actual_value.instance_of?(expected_value)
+      end
+
+      def compare_regexp(actual_value, expected_value)
+        expected_value.match?(actual_value.to_s)
+      end
+
+      def compare_proc(actual_value, expected_value)
+        Constraints.match(actual_value, expected_value.call)
+      end
+
+      def compare_array(actual_value, expected_value)
+        if simple_type?(expected_value)
+          compare_typed_array(actual_value, expected_value)
+        elsif interface?(expected_value)
+          compare_interface_array(actual_value, expected_value)
+        else
+          compare_exact_array(actual_value, expected_value)
+        end
+      end
+
+      # [SomeClass] => every element must be an instance of SomeClass.
+      def compare_typed_array(actual_value, expected_value)
+        type = expected_value[0]
+
+        actual_value.all? { |elem| compare_class(elem, type) }
+      end
+
+      # [{ ...interface... }] => every element must match the single interface.
+      # Elements go through match (not compare) so each one is held to the same
+      # key-structure guard as a top-level object; otherwise an element with an
+      # extra null-valued key would slip through (nil == nil).
+      def compare_interface_array(actual_value, expected_value)
+        interface = expected_value[0]
+
+        actual_value.all? { |elem| match(elem, interface) }
+      end
+
+      # Any other array => element-by-element match, sizes must be equal.
+      def compare_exact_array(actual_value, expected_value)
+        return false if actual_value&.size != expected_value&.size
+
+        expected_value.each_with_index.all? do |elem, index|
+          elem.is_a?(Hash) ? compare(actual_value[index], elem) : compare_simple_value(actual_value[index], elem)
+        end
+      end
+
+      def compare_simple_value(actual_value, expected_value)
+        actual_value == expected_value
+      end
+
+      def simple_type?(expected_value)
+        expected_value.size == 1 && expected_value[0].instance_of?(Class)
+      end
+
+      def interface?(expected_value)
+        expected_value.size == 1 && expected_value[0].is_a?(Hash)
+      end
+    end
+  end
+end
diff --git a/lib/rspec/json_api/traversal.rb b/lib/rspec/json_api/traversal.rb
new file mode 100644
index 0000000..f326b66
--- /dev/null
+++ b/lib/rspec/json_api/traversal.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module RSpec
+  module JsonApi
+    # Traversal holds the structural helpers used to compare JSON shapes:
+    # collecting the nested key structure of a Hash and sorting it into a
+    # canonical order. These were previously monkey-patched onto core Hash and
+    # Array; keeping them here means the gem no longer mutates those classes in
+    # the host application.
+    module Traversal
+      module_function
+
+      # The nested keys of a hash, with each nested hash's keys inlined as an
+      # array, e.g. { a: 1, b: { c: 2 } } => [:a, :b, [:c]].
+      def deep_keys(hash)
+        hash.each_with_object([]) do |(key, value), keys|
+          keys << key
+          keys << deep_keys(value) if value.respond_to?(:keys)
+        end
+      end
+
+      # Every leaf key path of a hash, e.g. { a: { b: 1 }, c: 2 } => [[:a, :b], [:c]].
+      def deep_key_paths(hash)
+        stack = hash.map { |key, value| [[key], value] }
+        key_map = []
+
+        until stack.empty?
+          key, value = stack.pop
+
+          key_map << key unless value.is_a?(Hash)
+
+          next unless value.is_a?(Hash)
+
+          value.each { |k, v| stack.push([key.dup << k, v]) }
+        end
+
+        key_map.reverse
+      end
+
+      # Recursively sorts an array (and any nested arrays) into a canonical order
+      # so two key structures can be compared regardless of original order.
+      def deep_sort(array)
+        array
+          .map { |element| element.is_a?(Array) ? deep_sort(element) : element }
+          .sort_by { |element| element.is_a?(Array) ? element.first.to_s : element.to_s }
+      end
+    end
+  end
+end
diff --git a/lib/rspec/json_api/types/uuid.rb b/lib/rspec/json_api/types/uuid.rb
index 9aaf244..19489df 100644
--- a/lib/rspec/json_api/types/uuid.rb
+++ b/lib/rspec/json_api/types/uuid.rb
@@ -3,7 +3,7 @@
 module RSpec
   module JsonApi
     module Types
-      UUID = /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$/
+      UUID = /\A[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}\z/
     end
   end
 end
diff --git a/lib/rspec/json_api/version.rb b/lib/rspec/json_api/version.rb
index 36312f8..363b347 100644
--- a/lib/rspec/json_api/version.rb
+++ b/lib/rspec/json_api/version.rb
@@ -2,6 +2,6 @@
 
 module RSpec
   module JsonApi
-    VERSION = "1.4.0"
+    VERSION = "1.5.0"
   end
 end
diff --git a/rspec-json_api.gemspec b/rspec-json_api.gemspec
index 99d2a8b..ecd42cb 100644
--- a/rspec-json_api.gemspec
+++ b/rspec-json_api.gemspec
@@ -27,10 +27,14 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{\Aexe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  # Uncomment to register a new dependency of your gem
+  # Runtime dependencies. The gem only needs ActiveSupport's blank?/present?
+  # core extensions and Rails::Generators (which lives in railties); depending
+  # on the full "rails" meta-gem would force ActiveRecord, ActionCable,
+  # ActionMailer, ActionMailbox, ActiveStorage, ActionText, etc. on every
+  # consumer of a JSON-matcher gem. The >= 6.1.4.1 floor is unchanged.
   spec.add_dependency "activesupport", ">= 6.1.4.1"
   spec.add_dependency "diffy", ">= 3.4.2"
-  spec.add_dependency "rails", ">= 6.1.4.1"
+  spec.add_dependency "railties", ">= 6.1.4.1"
   spec.add_dependency "rspec-rails", ">= 5.0.2"
 
   # For more information and examples about making a new gem, checkout our
diff --git a/spec/rspec/json_api/constraints_spec.rb b/spec/rspec/json_api/constraints_spec.rb
new file mode 100644
index 0000000..b35ff85
--- /dev/null
+++ b/spec/rspec/json_api/constraints_spec.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+RSpec.describe RSpec::JsonApi::Constraints do
+  describe ".match" do
+    it "raises ArgumentError for an unsupported option" do
+      expect { described_class.match("value", bogus: 1) }
+        .to raise_error(ArgumentError, /Unsupported match option/)
+    end
+
+    it "accepts a blank value when allow_blank is true" do
+      expect(described_class.match(nil, value: "John", allow_blank: true)).to be(true)
+    end
+
+    it "rejects a blank value that fails a companion constraint when allow_blank is false" do
+      expect(described_class.match(nil, value: "John", allow_blank: false)).to be(false)
+    end
+
+    it "checks remaining constraints when the value is present" do
+      expect(described_class.match(5, type: Integer, min: 3, max: 10)).to be(true)
+      expect(described_class.match(2, type: Integer, min: 3)).to be(false)
+    end
+  end
+end
diff --git a/spec/rspec/json_api/matchers/match_json_schema_spec.rb b/spec/rspec/json_api/matchers/match_json_schema_spec.rb
index d9a0859..d189638 100644
--- a/spec/rspec/json_api/matchers/match_json_schema_spec.rb
+++ b/spec/rspec/json_api/matchers/match_json_schema_spec.rb
@@ -15,6 +15,52 @@
     end
   end
 
+  context "when actual is not valid JSON" do
+    let(:expected) do
+      { id: String }
+    end
+
+    let(:actual) do
+      "this is not json"
+    end
+
+    include_examples "incorrect-match"
+  end
+
+  context "when the schema matches" do
+    it "does not build a diff" do
+      expect(Diffy::Diff).not_to receive(:new)
+
+      expect({ id: "1" }.to_json).to match_json_schema({ id: String })
+    end
+  end
+
+  context "when a matcher instance is reused for a second match" do
+    it "reflects the latest actual value in the failure message" do
+      matcher = match_json_schema({ id: Integer })
+
+      matcher.matches?({ id: "first" }.to_json)
+      matcher.failure_message
+
+      matcher.matches?({ id: "second" }.to_json)
+
+      expect(matcher.failure_message).to include("second")
+      expect(matcher.failure_message).not_to include("first")
+    end
+  end
+
+  context "when a nested object is replaced by a scalar" do
+    let(:expected) do
+      { items: [{ meta: { id: String } }] }
+    end
+
+    let(:actual) do
+      { items: [{ meta: "not-an-object" }] }.to_json
+    end
+
+    include_examples "incorrect-match"
+  end
+
   context "when schema does not match" do
     let(:expected) do
       {
@@ -362,6 +408,14 @@
 
         include_examples "incorrect-match"
       end
+
+      context "when a valid uuid is followed by a newline and extra content" do
+        let(:actual) do
+          { uuid: "07bbf12b-df44-4c8d-9415-aa33f51c5fc2\nmalicious" }.to_json
+        end
+
+        include_examples "incorrect-match"
+      end
     end
   end
 
@@ -1031,6 +1085,18 @@
 
         include_examples "incorrect-match"
       end
+
+      context "when an element has an extra null-valued key" do
+        let(:actual) do
+          [{ id: "8eccff73-f134-42f2-aed4-751d1f4ebd4f", extra: nil }].to_json
+        end
+
+        let(:expected) do
+          [{ id: String }]
+        end
+
+        include_examples "incorrect-match"
+      end
     end
   end
 
diff --git a/spec/rspec/json_api_spec.rb b/spec/rspec/json_api_spec.rb
index 7298eec..1307511 100644
--- a/spec/rspec/json_api_spec.rb
+++ b/spec/rspec/json_api_spec.rb
@@ -4,4 +4,9 @@
   it "has a version number" do
     expect(RSpec::JsonApi::VERSION).not_to be nil
   end
+
+  it "does not monkey-patch core Hash and Array" do
+    expect({}).not_to respond_to(:deep_keys, :deep_key_paths, :sanitize!)
+    expect([]).not_to respond_to(:deep_sort)
+  end
 end