diff --git a/Gemfile.lock b/Gemfile.lock
index bed803f..249a91e 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -4,6 +4,7 @@ PATH
     flagsmith (4.3.0)
       faraday (>= 2.0.1)
       faraday-retry
+      jsonpath (~> 1.1)
       semantic
 
 GEM
@@ -21,8 +22,11 @@ GEM
       faraday (~> 2.0)
     gem-release (2.2.2)
     json (2.7.1)
+    jsonpath (1.1.5)
+      multi_json
     language_server-protocol (3.17.0.3)
     method_source (1.0.0)
+    multi_json (1.17.0)
     net-http (0.4.1)
       uri
     parallel (1.24.0)
diff --git a/flagsmith.gemspec b/flagsmith.gemspec
index a4b950d..a1e9459 100644
--- a/flagsmith.gemspec
+++ b/flagsmith.gemspec
@@ -34,6 +34,7 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency 'faraday', '>= 2.0.1'
   spec.add_dependency 'faraday-retry'
+  spec.add_dependency 'jsonpath', '~> 1.1'
   spec.add_dependency 'semantic'
   spec.metadata['rubygems_mfa_required'] = 'true'
 end
diff --git a/lib/flagsmith/engine/core.rb b/lib/flagsmith/engine/core.rb
index 530a3f4..cb872b0 100644
--- a/lib/flagsmith/engine/core.rb
+++ b/lib/flagsmith/engine/core.rb
@@ -12,6 +12,7 @@
 require_relative 'segments/models'
 require_relative 'utils/hash_func'
 require_relative 'evaluation/mappers'
+require_relative 'evaluation/core'
 
 module Flagsmith
   module Engine
diff --git a/lib/flagsmith/engine/evaluation/core.rb b/lib/flagsmith/engine/evaluation/core.rb
index 2b510cc..e0d4eb1 100644
--- a/lib/flagsmith/engine/evaluation/core.rb
+++ b/lib/flagsmith/engine/evaluation/core.rb
@@ -1,20 +1,173 @@
 # frozen_string_literal: true
 
+require_relative '../utils/hash_func'
+require_relative '../features/constants'
+require_relative '../segments/evaluator'
+
 module Flagsmith
   module Engine
     module Evaluation
+      # Core evaluation logic module
       module Core
+        extend self
+        include Flagsmith::Engine::Utils::HashFunc
+        include Flagsmith::Engine::Features::TargetingReasons
+        include Flagsmith::Engine::Segments::Evaluator
         # Get evaluation result from evaluation context
         #
         # @param evaluation_context [Hash] The evaluation context
         # @return [Hash] Evaluation result with flags and segments
-        def self.get_evaluation_result(_evaluation_context)
-          # TODO: Implement core evaluation logic
+        # returns EvaluationResultWithMetadata
+        def get_evaluation_result(evaluation_context)
+          segments, segment_overrides = evaluate_segments(evaluation_context)
+          flags = evaluate_features(evaluation_context, segment_overrides)
           {
-            flags: {},
-            segments: []
+            flags: flags,
+            segments: segments
           }
         end
+
+        # Returns { segments: EvaluationResultSegments; segmentOverrides: Record<string, SegmentOverride>; }
+        def evaluate_segments(evaluation_context)
+          return [], {} if evaluation_context[:identity].nil? || evaluation_context[:segments].nil?
+
+          identity_segments = get_identity_segments_from_context(evaluation_context)
+
+          segments = identity_segments.map do |segment|
+            result = {
+              name: segment[:name]
+            }
+
+            result[:metadata] = segment[:metadata] if segment[:metadata]
+
+            result
+          end
+
+          segment_overrides = process_segment_overrides(identity_segments)
+
+          [segments, segment_overrides]
+        end
+
+        # Returns Record<string: override.name, SegmentOverride>
+        def process_segment_overrides(identity_segments)
+          segment_overrides = {}
+
+          identity_segments.each do |segment|
+            next unless segment[:overrides]
+
+            overrides_list = segment[:overrides].is_a?(Array) ? segment[:overrides] : []
+
+            overrides_list.each do |override|
+              next unless should_apply_override(override, segment_overrides)
+
+              segment_overrides[override[:name]] = {
+                feature: override,
+                segment_name: segment[:name]
+              }
+            end
+          end
+
+          segment_overrides
+        end
+
+        # returns EvaluationResultFlags<Metadata>
+        def evaluate_features(evaluation_context, segment_overrides)
+          flags = {}
+
+          (evaluation_context[:features] || {}).each_value do |feature|
+            segment_override = segment_overrides[feature[:name]]
+            final_feature = segment_override ? segment_override[:feature] : feature
+            has_override = !segment_override.nil?
+
+            # Evaluate feature value
+            evaluated = if has_override
+                          { value: final_feature[:value], reason: nil }
+                        else
+                          evaluate_feature_value(final_feature, get_identity_key(evaluation_context))
+                        end
+
+            # Build flag result
+            flag_result = {
+              name: final_feature[:name],
+              enabled: final_feature[:enabled],
+              value: evaluated[:value]
+            }
+
+            # Add metadata if present
+            flag_result[:metadata] = final_feature[:metadata] if final_feature[:metadata]
+
+            # Set reason
+            flag_result[:reason] = evaluated[:reason] ||
+                                   get_targeting_match_reason({ type: 'SEGMENT', override: segment_override })
+
+            flags[final_feature[:name].to_sym] = flag_result
+          end
+
+          flags
+        end
+
+        # Returns {value: any; reason?: string}
+        def evaluate_feature_value(feature, identity_key = nil)
+          return get_multivariate_feature_value(feature, identity_key) if feature[:variants]&.any? && identity_key
+
+          { value: feature[:value], reason: nil }
+        end
+
+        # Returns {value: any; reason?: string}
+        def get_multivariate_feature_value(feature, identity_key)
+          percentage_value = hashed_percentage_for_object_ids([feature[:key], identity_key])
+          sorted_variants = (feature[:variants] || []).sort_by { |v| v[:priority] || Float::INFINITY }
+
+          start_percentage = 0
+          sorted_variants.each do |variant|
+            limit = start_percentage + variant[:weight]
+            if start_percentage <= percentage_value && percentage_value < limit
+              return {
+                value: variant[:value],
+                reason: get_targeting_match_reason({ type: 'SPLIT', weight: variant[:weight] })
+              }
+            end
+            start_percentage = limit
+          end
+
+          { value: feature[:value], reason: nil }
+        end
+
+        # returns boolean
+        def should_apply_override(override, existing_overrides)
+          current_override = existing_overrides[override[:name]]
+          !current_override || higher_priority?(override[:priority], current_override[:feature][:priority])
+        end
+
+        private
+
+        # Extract identity key from evaluation context
+        #
+        # @param evaluation_context [Hash] The evaluation context
+        # @return [String, nil] The identity key or nil if no identity
+        def get_identity_key(evaluation_context)
+          return nil unless evaluation_context[:identity]
+
+          evaluation_context[:identity][:key] ||
+            "#{evaluation_context[:environment][:key]}_#{evaluation_context[:identity][:identifier]}"
+        end
+
+        # returns boolean
+        def higher_priority?(priority_a, priority_b)
+          (priority_a || Float::INFINITY) < (priority_b || Float::INFINITY)
+        end
+
+        def get_targeting_match_reason(match_object)
+          type = match_object[:type]
+
+          if type == 'SEGMENT'
+            return match_object[:override] ? "#{TARGETING_REASON_TARGETING_MATCH}; segment=#{match_object[:override][:segment_name]}" : TARGETING_REASON_DEFAULT
+          end
+
+          return "#{TARGETING_REASON_SPLIT}; weight=#{match_object[:weight]}" if type == 'SPLIT'
+
+          TARGETING_REASON_DEFAULT
+        end
       end
     end
   end
diff --git a/lib/flagsmith/engine/evaluation/mappers.rb b/lib/flagsmith/engine/evaluation/mappers.rb
index 81ba85e..745e9c0 100644
--- a/lib/flagsmith/engine/evaluation/mappers.rb
+++ b/lib/flagsmith/engine/evaluation/mappers.rb
@@ -161,7 +161,7 @@ def self.map_identity_overrides_to_segments(identity_overrides)
           features_to_identifiers = {}
 
           identity_overrides.each do |identity|
-            next if identity.identity_features.nil? || !identity.identity_features.any?
+            next if identity.identity_features.nil? || identity.identity_features.none?
 
             # Sort features by name for consistent hashing
             sorted_features = identity.identity_features.to_a.sort_by { |fs| fs.feature.name }
diff --git a/lib/flagsmith/engine/features/constants.rb b/lib/flagsmith/engine/features/constants.rb
new file mode 100644
index 0000000..b3baa08
--- /dev/null
+++ b/lib/flagsmith/engine/features/constants.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module Flagsmith
+  module Engine
+    module Features
+      # Targeting reason constants for evaluation results
+      module TargetingReasons
+        TARGETING_REASON_DEFAULT = 'DEFAULT'
+        TARGETING_REASON_TARGETING_MATCH = 'TARGETING_MATCH'
+        TARGETING_REASON_SPLIT = 'SPLIT'
+      end
+    end
+  end
+end
diff --git a/lib/flagsmith/engine/segments/evaluator.rb b/lib/flagsmith/engine/segments/evaluator.rb
index cc4a2f0..d4342f8 100644
--- a/lib/flagsmith/engine/segments/evaluator.rb
+++ b/lib/flagsmith/engine/segments/evaluator.rb
@@ -1,6 +1,9 @@
 # frozen_string_literal: true
 
+require 'json'
+require 'jsonpath'
 require_relative 'constants'
+require_relative 'models'
 require_relative '../utils/hash_func'
 
 module Flagsmith
@@ -11,6 +14,24 @@ module Evaluator
         include Flagsmith::Engine::Segments::Constants
         include Flagsmith::Engine::Utils::HashFunc
 
+        module_function
+        # Context-based segment evaluation (new approach)
+        # Returns all segments that the identity belongs to based on segment rules evaluation
+        #
+        # @param context [Hash] Evaluation context containing identity and segment definitions
+        # @return [Array<Hash>] Array of segments that the identity matches
+        def get_identity_segments_from_context(context)
+          return [] unless context[:identity] && context[:segments]
+
+          context[:segments].values.select do |segment|
+            next false if segment[:rules].nil? || segment[:rules].empty?
+
+            matches = segment[:rules].all? { |rule| traits_match_segment_rule_from_context(rule, segment[:key], context) }
+            matches
+          end
+        end
+
+        # Model-based segment evaluation (existing approach)
         def get_identity_segments(environment, identity, override_traits = nil)
           environment.project.segments.select do |s|
             evaluate_identity_in_segment(identity, s, override_traits)
@@ -70,6 +91,151 @@ def traits_match_segment_condition(identity_traits, condition, segment_id, ident
           false
         end
 
+        # Context-based helper functions (new approach)
+
+        # Evaluates whether a segment rule matches using context
+        #
+        # @param rule [Hash] The rule to evaluate
+        # @param segment_key [String] The segment key (used for percentage split)
+        # @param context [Hash] The evaluation context
+        # @return [Boolean] True if the rule matches
+        def traits_match_segment_rule_from_context(rule, segment_key, context)
+          matches_conditions = evaluate_conditions_from_context(rule, segment_key, context)
+          matches_sub_rules = evaluate_sub_rules_from_context(rule, segment_key, context)
+
+          matches_conditions && matches_sub_rules
+        end
+
+        # Evaluates rule conditions based on rule type (ALL/ANY/NONE)
+        #
+        # @param rule [Hash] The rule containing conditions and type
+        # @param segment_key [String] The segment key
+        # @param context [Hash] The evaluation context
+        # @return [Boolean] True if conditions match according to rule type
+        def evaluate_conditions_from_context(rule, segment_key, context)
+          return true unless rule[:conditions]&.any?
+
+          condition_results = rule[:conditions].map do |condition|
+            traits_match_segment_condition_from_context(condition, segment_key, context)
+          end
+
+          evaluate_rule_conditions(rule[:type], condition_results)
+        end
+
+        # Evaluates nested sub-rules
+        #
+        # @param rule [Hash] The rule containing nested rules
+        # @param segment_key [String] The segment key
+        # @param context [Hash] The evaluation context
+        # @return [Boolean] True if all sub-rules match
+        def evaluate_sub_rules_from_context(rule, segment_key, context)
+          return true if rule[:rules].nil? || rule[:rules].empty?
+
+          rule[:rules].all? do |sub_rule|
+            traits_match_segment_rule_from_context(sub_rule, segment_key, context)
+          end
+        end
+
+        # Evaluates a single segment condition using context
+        #
+        # @param condition [Hash] The condition to evaluate
+        # @param segment_key [String] The segment key (used for percentage split hashing)
+        # @param context [Hash] The evaluation context
+        # @return [Boolean] True if the condition matches
+        def traits_match_segment_condition_from_context(condition, segment_key, context)
+          if condition[:operator] == PERCENTAGE_SPLIT
+            context_value_key = get_context_value(condition[:property], context) || get_identity_key_from_context(context)
+            hashed_percentage = hashed_percentage_for_object_ids([segment_key, context_value_key])
+            return hashed_percentage <= condition[:value].to_f
+          end
+
+          return false if condition[:property].nil?
+
+          trait_value = get_trait_value(condition[:property], context)
+
+          return !trait_value.nil? if condition[:operator] == IS_SET
+          return trait_value.nil? if condition[:operator] == IS_NOT_SET
+
+          unless trait_value.nil?
+            # Reuse existing Condition class logic
+            condition_obj = Flagsmith::Engine::Segments::Condition.new(
+              operator: condition[:operator],
+              value: condition[:value],
+              property: condition[:property]
+            )
+            return condition_obj.match_trait_value?(trait_value)
+          end
+
+          false
+        end
+
+        # Evaluate rule conditions based on type (ALL/ANY/NONE)
+        #
+        # @param rule_type [String] The rule type
+        # @param condition_results [Array<Boolean>] Array of condition evaluation results
+        # @return [Boolean] True if conditions match according to rule type
+        def evaluate_rule_conditions(rule_type, condition_results)
+          case rule_type
+          when 'ALL'
+            condition_results.empty? || condition_results.all?
+          when 'ANY'
+            !condition_results.empty? && condition_results.any?
+          when 'NONE'
+            condition_results.empty? || condition_results.none?
+          else
+            false
+          end
+        end
+
+        # Get trait value from context, supporting JSONPath expressions
+        #
+        # @param property [String] The property name or JSONPath
+        # @param context [Hash] The evaluation context
+        # @return [Object, nil] The trait value or nil
+        def get_trait_value(property, context)
+          if property.start_with?('$.')
+            context_value = get_context_value(property, context)
+            return context_value if !context_value.nil? && !non_primitive?(context_value)
+          end
+
+          traits = context.dig(:identity, :traits) || {}
+          traits[property] || traits[property.to_sym]
+        end
+
+        # Get value from context using JSONPath syntax
+        #
+        # @param json_path [String] JSONPath expression (e.g., '$.identity.identifier')
+        # @param context [Hash] The evaluation context
+        # @return [Object, nil] The value at the path or nil
+        def get_context_value(json_path, context)
+          return nil unless context && json_path&.start_with?('$.')
+          results = JsonPath.new(json_path, use_symbols: true).on(context)
+          results.first
+        rescue StandardError
+          nil
+        end
+
+        # Get identity key from context
+        #
+        # @param context [Hash] The evaluation context
+        # @return [String, nil] The identity key or generated composite key
+        def get_identity_key_from_context(context)
+          return nil unless context[:identity]
+
+          context[:identity][:key] ||
+            "#{context[:environment][:key]}_#{context[:identity][:identifier]}"
+        end
+
+        # Check if value is non-primitive (object or array)
+        #
+        # @param value [Object] The value to check
+        # @return [Boolean] True if value is an object or array
+        def non_primitive?(value)
+          return false if value.nil?
+
+          value.is_a?(Hash) || value.is_a?(Array)
+        end
+
         private
 
         def handle_trait_existence_conditions(matching_trait, operator)
diff --git a/lib/flagsmith/engine/segments/models.rb b/lib/flagsmith/engine/segments/models.rb
index f339112..756c905 100644
--- a/lib/flagsmith/engine/segments/models.rb
+++ b/lib/flagsmith/engine/segments/models.rb
@@ -45,7 +45,7 @@ class Condition
           CONTAINS => ->(other_value, self_value) { (other_value || false) && other_value.include?(self_value) },
 
           NOT_CONTAINS => ->(other_value, self_value) { (other_value || false) && !other_value.include?(self_value) },
-          REGEX => ->(other_value, self_value) { (other_value || false) && other_value.match?(self_value) }
+          REGEX => ->(other_value, self_value) { (other_value || false) && other_value.to_s.match?(self_value) }
         }.freeze
 
         def initialize(operator:, value:, property: nil)
@@ -55,11 +55,17 @@ def initialize(operator:, value:, property: nil)
         end
 
         def match_trait_value?(trait_value)
-          # handle some exceptions
-          trait_value = Semantic::Version.new(trait_value.gsub(/:semver$/, '')) if @value.is_a?(String) && @value.match?(/:semver$/)
+          if @value.is_a?(String) && @value.match?(/:semver$/)
+            begin
+              trait_value = Semantic::Version.new(trait_value.to_s.gsub(/:semver$/, ''))
+            rescue ArgumentError, Semantic::Version::ValidationFailed => _e
+              return false
+            end
+          end
 
           return match_in_value(trait_value) if @operator == IN
           return match_modulo_value(trait_value) if @operator == MODULO
+          return MATCHING_FUNCTIONS[REGEX]&.call(trait_value, @value) if @operator == REGEX
 
           type_as_trait_value = format_to_type_of(trait_value)
           formatted_value = type_as_trait_value ? type_as_trait_value.call(@value) : @value
@@ -72,10 +78,17 @@ def format_to_type_of(input)
           {
             'String' => ->(v) { v.to_s },
             'Semantic::Version' => ->(v) { Semantic::Version.new(v.to_s.gsub(/:semver$/, '')) },
+            # Double check this is the desired behavior between SDKs
             'TrueClass' => ->(v) { ['True', 'true', 'TRUE', true, 1, '1'].include?(v) },
-            'FalseClass' => ->(v) { !['False', 'false', 'FALSE', false, 0, '0'].include?(v) },
-            'Integer' => ->(v) { v.to_i },
-            'Float' => ->(v) { v.to_f }
+            'FalseClass' => ->(v) { !['False', 'false', 'FALSE', false].include?(v) },
+            'Integer' => lambda { |v|
+              i = v.to_i
+              i.to_s == v.to_s ? i : v
+            },
+            'Float' => lambda { |v|
+              f = v.to_f
+              f.to_s == v.to_s ? f : v
+            }
           }[input.class.to_s]
         end
         # rubocop:enable Metrics/AbcSize
@@ -88,9 +101,19 @@ def match_modulo_value(trait_value)
         end
 
         def match_in_value(trait_value)
-          return @value.split(',').include?(trait_value.to_s) if trait_value.is_a?(String) || trait_value.is_a?(Integer)
+          return false if trait_value.nil? || trait_value.is_a?(TrueClass) || trait_value.is_a?(FalseClass)
 
-          false
+          return @value.include?(trait_value.to_s) if @value.is_a?(Array)
+
+          if @value.is_a?(String)
+            begin
+              parsed = JSON.parse(@value)
+              return parsed.include?(trait_value.to_s) if parsed.is_a?(Array)
+            rescue JSON::ParserError
+            end
+          end
+
+          @value.to_s.split(',').include?(trait_value.to_s)
         end
 
         class << self
diff --git a/spec/engine-test-data b/spec/engine-test-data
index 41c2021..218757f 160000
--- a/spec/engine-test-data
+++ b/spec/engine-test-data
@@ -1 +1 @@
-Subproject commit 41c202145e375c712600e318c439456de5b221d7
+Subproject commit 218757fd23f932760be681a09c686c9d6ef55fad
diff --git a/spec/engine/e2e/engine_spec.rb b/spec/engine/e2e/engine_spec.rb
index 77c9f92..0a40dbe 100644
--- a/spec/engine/e2e/engine_spec.rb
+++ b/spec/engine/e2e/engine_spec.rb
@@ -35,11 +35,12 @@ def load_test_file(filepath)
         test_expected_result = test_case[:result]
 
         # TODO: Implement evaluation logic
-        evaluation_result = {}
+        evaluation_result = Flagsmith::Engine::Evaluation::Core.get_evaluation_result(test_evaluation_context)
 
 
         # TODO: Uncomment when evaluation is implemented
-        # expect(evaluation_result).to eq(test_expected_result)
+        expect(evaluation_result[:flags]).to eq(test_expected_result[:flags])
+        expect(evaluation_result[:segments]).to eq(test_expected_result[:segments])
       end
     end
   end