diff --git a/.github/workflows/pull_request.yaml b/.github/workflows/pull_request.yaml
index ed95b9d..9880607 100644
--- a/.github/workflows/pull_request.yaml
+++ b/.github/workflows/pull_request.yaml
@@ -14,9 +14,6 @@ on:
       - synchronize
       - reopened
       - ready_for_review
-    branches:
-      - main
-      - release/**
 
   push:
     branches:
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.rb b/lib/flagsmith.rb
index 6e0464e..51ae62a 100644
--- a/lib/flagsmith.rb
+++ b/lib/flagsmith.rb
@@ -69,7 +69,6 @@ def initialize(config)
       api_client
       analytics_processor
       environment_data_polling_manager
-      engine
       load_offline_handler
     end
 
@@ -99,10 +98,6 @@ def realtime_client
       @realtime_client ||= Flagsmith::RealtimeClient.new(@config)
     end
 
-    def engine
-      @engine ||= Flagsmith::Engine::Engine.new
-    end
-
     def analytics_processor
       return nil unless @config.enable_analytics?
 
@@ -211,21 +206,33 @@ def get_value_for_identity(feature_name, user_id = nil, default: nil)
     end
 
     def get_identity_segments(identifier, traits = {})
-      unless environment
-        raise Flagsmith::ClientError,
-              'Local evaluation or offline handler is required to obtain identity segments.'
-      end
+      raise Flagsmith::ClientError, 'Local evaluation or offline handler is required to obtain identity segments.' unless environment
 
       identity_model = get_identity_model(identifier, traits)
-      segment_models = engine.get_identity_segments(environment, identity_model)
-      segment_models.map { |sm| Flagsmith::Segments::Segment.new(id: sm.id, name: sm.name) }.compact
+      context = Flagsmith::Engine::Mappers.get_evaluation_context(environment, identity_model)
+      raise Flagsmith::ClientError, 'Local evaluation required to obtain identity segments' unless context
+
+      evaluation_result = Flagsmith::Engine.get_evaluation_result(context)
+      evaluation_result[:segments].filter_map do |segment_result|
+        id = segment_result.dig(:metadata, :id)
+        Flagsmith::Segments::Segment.new(id: id, name: segment_result[:name]) if id
+      end
     end
 
     private
 
-    def environment_flags_from_document
-      Flagsmith::Flags::Collection.from_feature_state_models(
-        engine.get_environment_feature_states(environment),
+    def environment_flags_from_document # rubocop:disable Metrics/MethodLength
+      context = Flagsmith::Engine::Mappers.get_evaluation_context(environment)
+
+      unless context
+        raise Flagsmith::ClientError,
+              'Unable to get flags. No environment present.'
+      end
+
+      evaluation_result = Flagsmith::Engine.get_evaluation_result(context)
+
+      Flagsmith::Flags::Collection.from_evaluation_result(
+        evaluation_result,
         analytics_processor: analytics_processor,
         default_flag_handler: default_flag_handler,
         offline_handler: offline_handler
@@ -234,12 +241,13 @@ def environment_flags_from_document
 
     def get_identity_flags_from_document(identifier, traits = {})
       identity_model = get_identity_model(identifier, traits)
+      context = Flagsmith::Engine::Mappers.get_evaluation_context(environment, identity_model)
+      raise Flagsmith::ClientError, 'Unable to get flags. No environment present.' unless context
 
-      Flagsmith::Flags::Collection.from_feature_state_models(
-        engine.get_identity_feature_states(environment, identity_model),
-        identity_id: identity_model.composite_key,
-        analytics_processor: analytics_processor,
-        default_flag_handler: default_flag_handler,
+      evaluation_result = Flagsmith::Engine.get_evaluation_result(context)
+      Flagsmith::Flags::Collection.from_evaluation_result(
+        evaluation_result,
+        analytics_processor: analytics_processor, default_flag_handler: default_flag_handler,
         offline_handler: offline_handler
       )
     end
diff --git a/lib/flagsmith/engine/core.rb b/lib/flagsmith/engine/core.rb
index 3e64f1c..dded5a5 100644
--- a/lib/flagsmith/engine/core.rb
+++ b/lib/flagsmith/engine/core.rb
@@ -5,6 +5,7 @@
 
 require_relative 'environments/models'
 require_relative 'features/models'
+require_relative 'features/constants'
 require_relative 'identities/models'
 require_relative 'organisations/models'
 require_relative 'projects/models'
@@ -12,79 +13,135 @@
 require_relative 'segments/models'
 require_relative 'utils/hash_func'
 require_relative 'mappers'
-require_relative 'evaluation/core'
 
 module Flagsmith
+  # Core evaluation logic for feature flags
   module Engine
-    # Flags engine methods
-    class Engine
-      include Flagsmith::Engine::Segments::Evaluator
-
-      def get_identity_feature_state(environment, identity, feature_name, override_traits = nil)
-        feature_states = get_identity_feature_states_dict(environment, identity, override_traits).values
+    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 get_evaluation_result(evaluation_context)
+      evaluation_context = get_enriched_context(evaluation_context)
+      segments, segment_overrides = evaluate_segments(evaluation_context)
+      flags = evaluate_features(evaluation_context, segment_overrides)
+      {
+        flags: flags,
+        segments: segments
+      }
+    end
 
-        feature_state = feature_states.find { |f| f.feature.name == feature_name }
+    # Returns { segments: EvaluationResultSegments; segmentOverrides: Record<string, SegmentOverride>; }
+    def evaluate_segments(evaluation_context)
+      return [], {} if evaluation_context[:segments].nil?
 
-        raise Flagsmith::FeatureStateNotFound, 'Feature State Not Found' if feature_state.nil?
+      identity_segments = get_segments_from_context(evaluation_context)
 
-        feature_state
+      segments = identity_segments.map do |segment|
+        { name: segment[:name], metadata: segment[:metadata] }.compact
       end
 
-      def get_identity_feature_states(environment, identity, override_traits = nil)
-        feature_states = get_identity_feature_states_dict(environment, identity, override_traits).values
+      segment_overrides = process_segment_overrides(identity_segments)
+
+      [segments, segment_overrides]
+    end
 
-        return feature_states.select(&:enabled?) if environment.project.hide_disabled_flags
+    # Returns Record<string: override.name, SegmentOverride>
+    def process_segment_overrides(identity_segments) # rubocop:disable Metrics/MethodLength
+      segment_overrides = {}
 
-        feature_states
+      identity_segments.each do |segment|
+        Array(segment[:overrides]).each do |override|
+          next unless should_apply_override(override, segment_overrides)
+
+          segment_overrides[override[:name]] = {
+            feature: override,
+            segment_name: segment[:name]
+          }
+        end
       end
 
-      def get_environment_feature_state(environment, feature_name)
-        features_state = environment.feature_states.find { |f| f.feature.name == feature_name }
+      segment_overrides
+    end
 
-        raise Flagsmith::FeatureStateNotFound, 'Feature State Not Found' if features_state.nil?
+    def evaluate_features(evaluation_context, segment_overrides)
+      identity_key = get_identity_key(evaluation_context)
 
-        features_state
+      (evaluation_context[:features] || {}).each_with_object({}) do |(_, feature), flags|
+        segment_override = segment_overrides[feature[:name]]
+        final_feature = segment_override ? segment_override[:feature] : feature
+
+        flag_result = build_flag_result(final_feature, identity_key, segment_override)
+        flags[final_feature[:name].to_sym] = flag_result
       end
+    end
 
-      def get_environment_feature_states(environment)
-        return environment.feature_states.select(&:enabled?) if environment.project.hide_disabled_flags
+    # 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
 
-        environment.feature_states
-      end
+      { value: feature[:value], reason: nil }
+    end
 
-      private
+    # 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] || WEAKEST_PRIORITY }
 
-      def get_identity_feature_states_dict(environment, identity, override_traits = nil)
-        # Get feature states from the environment
-        feature_states = {}
-        override = ->(fs) { feature_states[fs.feature.id] = fs }
-        environment.feature_states.each(&override)
+      variant = find_matching_variant(sorted_variants, percentage_value)
+      variant || { value: feature[:value], reason: nil }
+    end
 
-        override_by_matching_segments(environment, identity, override_traits) do |fs|
-          override.call(fs) unless higher_segment_priority?(feature_states, fs)
-        end
+    def find_matching_variant(sorted_variants, percentage_value)
+      start_percentage = 0
+      sorted_variants.each do |variant|
+        limit = start_percentage + variant[:weight]
+        return { value: variant[:value], reason: "#{TARGETING_REASON_SPLIT}; weight=#{variant[:weight]}" } if start_percentage <= percentage_value && percentage_value < limit
 
-        # Override with any feature states defined directly the identity
-        identity.identity_features.each(&override)
-        feature_states
+        start_percentage = limit
       end
+      nil
+    end
 
-      # Override with any feature states defined by matching segments
-      def override_by_matching_segments(environment, identity, override_traits)
-        identity_segments = get_identity_segments(environment, identity, override_traits)
-        identity_segments.each do |matching_segment|
-          matching_segment.feature_states.each do |feature_state|
-            yield feature_state if block_given?
-          end
-        end
-      end
+    # returns boolean
+    def should_apply_override(override, existing_overrides)
+      current_override = existing_overrides[override[:name]]
+      !current_override || stronger_priority?(override[:priority], current_override[:feature][:priority])
+    end
 
-      def higher_segment_priority?(collection, feature_state)
-        collection.key?(feature_state.feature.id) &&
-          collection[feature_state.feature.id].higher_segment_priority?(
-            feature_state
-          )
-      end
+    private
+
+    def build_flag_result(feature, identity_key, segment_override)
+      evaluated = evaluate_feature_value(feature, identity_key)
+
+      flag_result = {
+        name: feature[:name],
+        enabled: feature[:enabled],
+        value: evaluated[:value],
+        reason: evaluated[:reason] || (segment_override ? "#{TARGETING_REASON_TARGETING_MATCH}; segment=#{segment_override[:segment_name]}" : TARGETING_REASON_DEFAULT)
+      }
+
+      flag_result[:metadata] = feature[:metadata] if feature[:metadata]
+      flag_result
+    end
+
+    # 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]
+    end
+
+    def stronger_priority?(priority_a, priority_b)
+      (priority_a || WEAKEST_PRIORITY) < (priority_b || WEAKEST_PRIORITY)
     end
   end
 end
diff --git a/lib/flagsmith/engine/evaluation/core.rb b/lib/flagsmith/engine/evaluation/core.rb
index 0ddc342..5a7fe58 100644
--- a/lib/flagsmith/engine/evaluation/core.rb
+++ b/lib/flagsmith/engine/evaluation/core.rb
@@ -1,20 +1,140 @@
 # 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 for feature flags
       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
+        def get_evaluation_result(evaluation_context)
+          evaluation_context = get_enriched_context(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[:segments].nil?
+
+          identity_segments = get_segments_from_context(evaluation_context)
+
+          segments = identity_segments.map do |segment|
+            { name: segment[:name], metadata: segment[:metadata] }.compact
+          end
+
+          segment_overrides = process_segment_overrides(identity_segments)
+
+          [segments, segment_overrides]
+        end
+
+        # Returns Record<string: override.name, SegmentOverride>
+        def process_segment_overrides(identity_segments) # rubocop:disable Metrics/MethodLength
+          segment_overrides = {}
+
+          identity_segments.each do |segment|
+            Array(segment[:overrides]).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
+
+        def evaluate_features(evaluation_context, segment_overrides)
+          identity_key = get_identity_key(evaluation_context)
+
+          (evaluation_context[:features] || {}).each_with_object({}) do |(_, feature), flags|
+            segment_override = segment_overrides[feature[:name]]
+            final_feature = segment_override ? segment_override[:feature] : feature
+
+            flag_result = build_flag_result(final_feature, identity_key, segment_override)
+            flags[final_feature[:name].to_sym] = flag_result
+          end
+        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] || WEAKEST_PRIORITY }
+
+          variant = find_matching_variant(sorted_variants, percentage_value)
+          variant || { value: feature[:value], reason: nil }
+        end
+
+        def find_matching_variant(sorted_variants, percentage_value)
+          start_percentage = 0
+          sorted_variants.each do |variant|
+            limit = start_percentage + variant[:weight]
+            return { value: variant[:value], reason: "#{TARGETING_REASON_SPLIT}; weight=#{variant[:weight]}" } if start_percentage <= percentage_value && percentage_value < limit
+
+            start_percentage = limit
+          end
+          nil
+        end
+
+        # returns boolean
+        def should_apply_override(override, existing_overrides)
+          current_override = existing_overrides[override[:name]]
+          !current_override || stronger_priority?(override[:priority], current_override[:feature][:priority])
+        end
+
+        private
+
+        def build_flag_result(feature, identity_key, segment_override)
+          evaluated = evaluate_feature_value(feature, identity_key)
+
+          flag_result = {
+            name: feature[:name],
+            enabled: feature[:enabled],
+            value: evaluated[:value],
+            reason: evaluated[:reason] || (segment_override ? "#{TARGETING_REASON_TARGETING_MATCH}; segment=#{segment_override[:segment_name]}" : TARGETING_REASON_DEFAULT)
           }
+
+          flag_result[:metadata] = feature[:metadata] if feature[:metadata]
+          flag_result
+        end
+
+        # 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 stronger_priority?(priority_a, priority_b)
+          (priority_a || WEAKEST_PRIORITY) < (priority_b || WEAKEST_PRIORITY)
         end
       end
     end
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/features/models.rb b/lib/flagsmith/engine/features/models.rb
index d6d0ff2..de7ae0f 100644
--- a/lib/flagsmith/engine/features/models.rb
+++ b/lib/flagsmith/engine/features/models.rb
@@ -58,7 +58,7 @@ def multivariate_value(identity_id)
       #        but `self` does.
       #     2. `other` have a feature segment with high priority
       def higher_segment_priority?(other)
-        feature_segment.priority.to_i < (other&.feature_segment&.priority || Float::INFINITY)
+        feature_segment.priority.to_i < (other&.feature_segment&.priority || WEAKEST_PRIORITY)
       rescue TypeError, NoMethodError
         false
       end
diff --git a/lib/flagsmith/engine/mappers/environment.rb b/lib/flagsmith/engine/mappers/environment.rb
index 75539f6..4931ace 100644
--- a/lib/flagsmith/engine/mappers/environment.rb
+++ b/lib/flagsmith/engine/mappers/environment.rb
@@ -26,7 +26,7 @@ def self.build_feature_hash(feature_state)
             name: feature_state.feature.name,
             enabled: feature_state.enabled,
             value: feature_state.get_value,
-            metadata: { flagsmith_id: feature_state.feature.id }
+            metadata: { id: feature_state.feature.id }
           }
           add_variants_to_feature(feature_hash, feature_state)
           add_priority_to_feature(feature_hash, feature_state)
diff --git a/lib/flagsmith/engine/mappers/identity.rb b/lib/flagsmith/engine/mappers/identity.rb
index 84c278c..45dc374 100644
--- a/lib/flagsmith/engine/mappers/identity.rb
+++ b/lib/flagsmith/engine/mappers/identity.rb
@@ -52,7 +52,7 @@ def self.build_overrides_key(identity_features)
               enabled: feature_state.enabled,
               value: feature_state.get_value,
               priority: Mappers::STRONGEST_PRIORITY,
-              metadata: { flagsmith_id: feature_state.feature.id }
+              metadata: { id: feature_state.feature.id }
             }
           end
         end
diff --git a/lib/flagsmith/engine/mappers/segments.rb b/lib/flagsmith/engine/mappers/segments.rb
index 7020be1..f842e6f 100644
--- a/lib/flagsmith/engine/mappers/segments.rb
+++ b/lib/flagsmith/engine/mappers/segments.rb
@@ -21,7 +21,7 @@ def self.build_segment_hash(segment)
             overrides: build_overrides(segment.feature_states),
             metadata: {
               source: 'API',
-              flagsmith_id: segment.id
+              id: segment.id
             }
           }
         end
@@ -33,7 +33,7 @@ def self.build_overrides(feature_states) # rubocop:disable Metrics/MethodLength
               name: feature_state.feature.name,
               enabled: feature_state.enabled,
               value: feature_state.get_value,
-              metadata: { flagsmith_id: feature_state.feature.id }
+              metadata: { id: feature_state.feature.id }
             }
             add_priority_to_override(override_hash, feature_state)
             override_hash
diff --git a/lib/flagsmith/engine/segments/evaluator.rb b/lib/flagsmith/engine/segments/evaluator.rb
index cc4a2f0..c5d55cb 100644
--- a/lib/flagsmith/engine/segments/evaluator.rb
+++ b/lib/flagsmith/engine/segments/evaluator.rb
@@ -1,22 +1,65 @@
 # frozen_string_literal: true
 
+require 'json'
+require 'jsonpath'
 require_relative 'constants'
+require_relative 'models'
 require_relative '../utils/hash_func'
 
 module Flagsmith
   module Engine
     module Segments
       # Evaluator methods
-      module Evaluator
+      module Evaluator # rubocop:disable Metrics/ModuleLength
         include Flagsmith::Engine::Segments::Constants
         include Flagsmith::Engine::Utils::HashFunc
 
-        def get_identity_segments(environment, identity, override_traits = nil)
-          environment.project.segments.select do |s|
-            evaluate_identity_in_segment(identity, s, override_traits)
+        module_function
+
+        def get_enriched_context(context)
+          identity_context = context[:identity]
+          return context unless identity_context
+          return context if identity_context[:key]
+
+          enriched_context = context.dup
+          enriched_context[:identity] = identity_context.merge(
+            key: "#{context[:environment][:key]}_#{identity_context[:identifier]}"
+          )
+          enriched_context
+        end
+
+        # Context-based segment evaluation
+        # 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_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
 
+        def traits_match_segment_condition(identity_traits, condition, segment_id, identity_id)
+          if condition.operator == PERCENTAGE_SPLIT
+            return hashed_percentage_for_object_ids([segment_id,
+                                                     identity_id]) <= condition.value.to_f
+          end
+
+          trait = identity_traits.find { |t| t.key.to_s == condition.property }
+
+          return handle_trait_existence_conditions(trait, condition.operator) if [IS_SET,
+                                                                                  IS_NOT_SET].include?(condition.operator)
+
+          return condition.match_trait_value?(trait.trait_value) if trait
+
+          false
+        end
+
         # Evaluates whether a given identity is in the provided segment.
         #
         # :param identity: identity model object to evaluate
@@ -54,28 +97,149 @@ def traits_match_segment_rule(identity_traits, rule, segment_id, identity_id)
         end
         # rubocop:enable Metrics/MethodLength
 
-        def traits_match_segment_condition(identity_traits, condition, segment_id, identity_id)
-          if condition.operator == PERCENTAGE_SPLIT
-            return hashed_percentage_for_object_ids([segment_id,
-                                                     identity_id]) <= condition.value.to_f
+        # Context-based helper functions
+
+        # 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
 
-          trait = identity_traits.find { |t| t.key.to_s == condition.property }
+          evaluate_rule_conditions(rule[:type], condition_results)
+        end
 
-          return handle_trait_existence_conditions(trait, condition.operator) if [IS_SET,
-                                                                                  IS_NOT_SET].include?(condition.operator)
+        # 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?
 
-          return condition.match_trait_value?(trait.trait_value) if trait
+          rule[:rules].all? do |sub_rule|
+            traits_match_segment_rule_from_context(sub_rule, segment_key, context)
+          end
+        end
 
-          false
+        # 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)
+          return handle_percentage_split(condition, segment_key, context) if condition[:operator] == PERCENTAGE_SPLIT
+          return false if condition[:property].nil?
+
+          trait_value = get_trait_value(condition[:property], context)
+          evaluate_trait_condition(condition, trait_value)
+        end
+
+        def handle_percentage_split(condition, segment_key, context)
+          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])
+          hashed_percentage <= condition[:value].to_f
         end
 
-        private
+        def evaluate_trait_condition(condition, trait_value)
+          return !trait_value.nil? if condition[:operator] == IS_SET
+          return trait_value.nil? if condition[:operator] == IS_NOT_SET
+          return false if trait_value.nil?
 
-        def handle_trait_existence_conditions(matching_trait, operator)
-          return operator == IS_NOT_SET if matching_trait.nil?
+          condition_obj = Flagsmith::Engine::Segments::Condition.new(
+            operator: condition[:operator],
+            value: condition[:value],
+            property: condition[:property]
+          )
+          condition_obj.match_trait_value?(trait_value)
+        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?('$.')
+            context_value = get_context_value(property, context)
+            return context_value if !context_value.nil? && primitive?(context_value)
+          end
+
+          traits = context.dig(:identity, :traits) || {}
+          traits[property] || traits[property.to_sym]
+        end
+
+        # Get value from context using JSONPath syntax
+        #
+        # @param json_path [String] JSONPath expression (e.g., '$.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]
+        end
+
+        # Check if value is primitive (not an object or array)
+        #
+        # @param value [Object] The value to check
+        # @return [Boolean] True if value is primitive (not an object or array)
+        def primitive?(value)
+          return true if value.nil?
 
-          operator == IS_SET
+          !(value.is_a?(Hash) || value.is_a?(Array))
         end
       end
     end
diff --git a/lib/flagsmith/engine/segments/models.rb b/lib/flagsmith/engine/segments/models.rb
index f339112..70a6d03 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)
@@ -55,30 +55,48 @@ 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$/, '')) if @value.is_a?(String) && @value.match?(/:semver$/)
+          trait_value = parse_semver_trait_value(trait_value)
+          return false if trait_value.nil?
 
           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
 
+          match_with_type_conversion(trait_value)
+        end
+
+        def parse_semver_trait_value(trait_value)
+          return trait_value unless @value.is_a?(String) && @value.match?(/:semver$/)
+
+          Semantic::Version.new(trait_value.to_s.gsub(/:semver$/, ''))
+        rescue ArgumentError, Semantic::Version::ValidationFailed
+          nil
+        end
+
+        def match_with_type_conversion(trait_value)
           type_as_trait_value = format_to_type_of(trait_value)
           formatted_value = type_as_trait_value ? type_as_trait_value.call(@value) : @value
-
           MATCHING_FUNCTIONS[operator]&.call(trait_value, formatted_value)
         end
 
-        # rubocop:disable Metrics/AbcSize
+        TYPE_CONVERTERS = {
+          'String' => ->(v) { v.to_s },
+          'Semantic::Version' => ->(v) { Semantic::Version.new(v.to_s.gsub(/:semver$/, '')) },
+          'TrueClass' => ->(v) { ['True', 'true', 'TRUE', true, 1, '1'].include?(v) },
+          'FalseClass' => ->(v) { !['False', 'false', 'FALSE', false].include?(v) },
+          'Integer' => lambda { |v|
+            i = v.to_i
+            i.to_s == v.to_s ? i : v
+          },
+          'Float' => lambda { |v|
+            f = v.to_f
+            f.to_s == v.to_s ? f : v
+          }
+        }.freeze
+
         def format_to_type_of(input)
-          {
-            'String' => ->(v) { v.to_s },
-            'Semantic::Version' => ->(v) { Semantic::Version.new(v.to_s.gsub(/:semver$/, '')) },
-            '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 }
-          }[input.class.to_s]
+          TYPE_CONVERTERS[input.class.to_s]
         end
-        # rubocop:enable Metrics/AbcSize
 
         def match_modulo_value(trait_value)
           divisor, remainder = @value.split('|')
@@ -88,9 +106,25 @@ 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 invalid_in_value?(trait_value)
+          return @value.include?(trait_value.to_s) if @value.is_a?(Array)
 
-          false
+          parse_and_match_string_value(trait_value)
+        end
+
+        def invalid_in_value?(trait_value)
+          trait_value.nil? || [TrueClass, FalseClass].any? { |klass| trait_value.is_a?(klass) }
+        end
+
+        def parse_and_match_string_value(trait_value) # rubocop:disable Metrics/AbcSize
+          return @value.to_s.split(',').include?(trait_value.to_s) unless @value.is_a?(String)
+
+          parsed = JSON.parse(@value)
+          return parsed.include?(trait_value.to_s) if parsed.is_a?(Array)
+
+          @value.to_s.split(',').include?(trait_value.to_s)
+        rescue JSON::ParserError
+          @value.to_s.split(',').include?(trait_value.to_s)
         end
 
         class << self
diff --git a/lib/flagsmith/sdk/models/flags.rb b/lib/flagsmith/sdk/models/flags.rb
index d851c98..59cea07 100644
--- a/lib/flagsmith/sdk/models/flags.rb
+++ b/lib/flagsmith/sdk/models/flags.rb
@@ -32,12 +32,13 @@ def initialize(enabled:, value:)
 
     # 'live' Flag class as returned by API or local evaluation
     class Flag < BaseFlag
-      attr_reader :feature_name, :feature_id
+      attr_reader :feature_name, :feature_id, :reason
 
-      def initialize(feature_name:, enabled:, value:, feature_id:)
+      def initialize(feature_name:, enabled:, value:, feature_id:, reason: nil)
         super(enabled: enabled, value: value, default: false)
         @feature_name = feature_name
         @feature_id = feature_id
+        @reason = reason
       end
 
       def <=>(other)
@@ -54,7 +55,8 @@ def to_h
           feature_name: feature_name,
           value: value,
           enabled: enabled,
-          default: default
+          default: default,
+          reason: reason
         }
       end
 
@@ -172,15 +174,27 @@ def from_api(json_data, **args)
           )
         end
 
-        def from_feature_state_models(feature_states, identity_id: nil, **args)
-          to_flag_object = lambda { |feature_state, acc|
-            acc[normalize_key(feature_state.feature.name)] =
-              Flagsmith::Flags::Flag.from_feature_state_model(feature_state, identity_id)
+        def from_evaluation_result(evaluation_result, **args)
+          to_flag_object = lambda { |flag_result, acc|
+            id = flag_result.dig(:metadata, :id)
+            if id.nil?
+              raise Flagsmith::ClientError,
+                    "FlagResult metadata.id is missing for feature \"#{flag_result[:name]}\". This indicates a bug in the SDK, please report it."
+            end
+
+            acc[flag_result[:name]] = Collection.map_evaluated_flag_to_flag_result(flag_result, id)
           }
 
-          new(
-            feature_states.each_with_object({}, &to_flag_object),
-            **args
+          new(evaluation_result[:flags].each_value.each_with_object({}, &to_flag_object), **args)
+        end
+
+        def map_evaluated_flag_to_flag_result(flag_result, id)
+          Flagsmith::Flags::Flag.new(
+            feature_name: flag_result[:name],
+            enabled: flag_result[:enabled],
+            value: flag_result[:value],
+            feature_id: id,
+            reason: flag_result[:reason]
           )
         end
 
diff --git a/spec/engine/e2e/engine_spec.rb b/spec/engine/e2e/engine_spec.rb
index 77c9f92..8fe8703 100644
--- a/spec/engine/e2e/engine_spec.rb
+++ b/spec/engine/e2e/engine_spec.rb
@@ -8,8 +8,6 @@ def get_test_files
 end
 
 def parse_jsonc(content)
-  # Simple JSONC parser: remove single-line comments
-  # JSON.parse will handle the rest
   cleaned = content.lines.reject { |line| line.strip.start_with?('//') }.join
   JSON.parse(cleaned, symbolize_names: true)
 end
@@ -34,12 +32,10 @@ def load_test_file(filepath)
         test_evaluation_context = test_case[:context]
         test_expected_result = test_case[:result]
 
-        # TODO: Implement evaluation logic
-        evaluation_result = {}
+        evaluation_result = Flagsmith::Engine.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
diff --git a/spec/engine/unit/core_spec.rb b/spec/engine/unit/core_spec.rb
deleted file mode 100644
index ad94a63..0000000
--- a/spec/engine/unit/core_spec.rb
+++ /dev/null
@@ -1,114 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-RSpec.describe Flagsmith::Engine, type: :model do
-  subject { Flagsmith::Engine::Engine.new }
-
-  it 'test_identity_get_feature_state_without_any_override' do
-    feature_state = subject.get_identity_feature_state(
-      environment, identity, feature1.name
-    )
-
-    expect(feature_state.feature).to eq(feature1)
-  end
-
-  it 'test_identity_get_feature_state_without_any_override_no_fs' do
-    expect {
-      subject.get_identity_feature_state(environment, identity, 'nonExistentName')
-    }.to raise_error(Flagsmith::FeatureStateNotFound)
-  end
-
-  it 'test_identity_get_all_feature_states_no_segments' do
-    env = environment
-    ident = identity
-    overridden_feature = Flagsmith::Engine::Feature.new(
-      id: 3, name: 'overridden_feature', type: 'STANDARD'
-    )
-
-    env.feature_states << Flagsmith::Engine::FeatureState.new(
-      feature: overridden_feature, enabled: false, django_id: 3
-    )
-
-    ident.identity_features << Flagsmith::Engine::FeatureState.new(
-      feature: overridden_feature, enabled: true, id: 4
-    )
-
-    feature_states = subject.get_identity_feature_states(env, ident)
-
-    expect(feature_states.length).to eq(3)
-
-    feature_states.each do |feature_state|
-      environment_feature_state = get_environment_feature_state_for_feature(
-        env, feature_state.feature
-      )
-      expected =
-        if environment_feature_state&.feature == overridden_feature then true
-        else environment_feature_state&.enabled
-        end
-        expect(feature_state.enabled?).to eq(expected)
-    end
-  end
-
-  it 'test_identity_get_all_feature_states_with_traits' do
-    trait_models = [Flagsmith::Engine::Identities::Trait.new(
-      trait_key: Engine::Builders::SEGMENT_CONDITION_PROPERTY,
-      trait_value: Engine::Builders::SEGMENT_CONDITION_STRING_VALUE
-    )]
-
-    feature_states = subject.get_identity_feature_states(
-      environment_with_segment_override, identity_in_segment, trait_models
-    )
-
-    expect(feature_states.first.get_value).to eq(Engine::Builders::SEGMENT_OVERRIDE_FEATURE_STATE_VALUE)
-  end
-
-  it 'test_identity_get_all_feature_states_with_traits_hideDisabledFlags' do
-    trait_models = [Flagsmith::Engine::Identities::Trait.new(
-      trait_key: Engine::Builders::SEGMENT_CONDITION_PROPERTY,
-      trait_value: Engine::Builders::SEGMENT_CONDITION_STRING_VALUE
-    )]
-
-    env = environment_with_segment_override
-    env.project.hide_disabled_flags = true
-
-    feature_states = subject.get_identity_feature_states(
-      env, identity_in_segment, trait_models
-    )
-    expect(feature_states.length).to eq(0)
-  end
-
-  it 'test_environment_get_all_feature_states' do
-    env = environment
-    feature_states = subject.get_environment_feature_states(env)
-
-    expect(feature_states).to eq(env.feature_states)
-  end
-
-  it 'test_environment_get_feature_states_hides_disabled_flags_if_enabled' do
-    env = environment
-
-    env.project.hide_disabled_flags = true
-
-    feature_states = subject.get_environment_feature_states(env)
-
-    expect(feature_states).to_not eq(env.feature_states)
-    feature_states.each do |fs|
-      expect(fs.enabled).to be_truthy
-    end
-  end
-
-  it 'test_environment_get_feature_state' do
-    env = environment
-    feature = feature1
-    feature_state = subject.get_environment_feature_state(env, feature.name)
-
-    expect(feature_state.feature).to eq(feature)
-  end
-
-  it 'test_environment_get_feature_state_raises_feature_state_not_found' do
-      expect {
-        subject.get_environment_feature_state(environment, 'not_a_feature_name')
-      }.to raise_error(Flagsmith::FeatureStateNotFound)
-  end
-end
diff --git a/spec/engine/unit/evaluation_context_mappers_spec.rb b/spec/engine/unit/evaluation_context_mappers_spec.rb
index 0af9686..ce422b7 100644
--- a/spec/engine/unit/evaluation_context_mappers_spec.rb
+++ b/spec/engine/unit/evaluation_context_mappers_spec.rb
@@ -33,7 +33,7 @@
       expect(segment[:rules].length).to eq(1)
       expect(segment[:overrides]).to be_empty.or be_an(Array)
       expect(segment[:metadata][:source]).to eq('API')
-      expect(segment[:metadata][:flagsmith_id]).to eq(1)
+      expect(segment[:metadata][:id]).to eq(1)
 
       # Verify segment rules
       expect(segment[:rules][0][:type]).to eq('ALL')
@@ -72,7 +72,7 @@
       expect(override[:enabled]).to be false
       expect(override[:value]).to eq('some-overridden-value')
       expect(override[:priority]).to eq(Flagsmith::Engine::Mappers::STRONGEST_PRIORITY)
-      expect(override[:metadata][:flagsmith_id]).to eq(1)
+      expect(override[:metadata][:id]).to eq(1)
 
       # Verify features
       expect(context[:features]).to be_a(Hash)
@@ -83,7 +83,7 @@
       expect(some_feature[:enabled]).to be true
       expect(some_feature[:value]).to eq('some-value')
       expect(some_feature[:priority]).to be_nil
-      expect(some_feature[:metadata][:flagsmith_id]).to eq(1)
+      expect(some_feature[:metadata][:id]).to eq(1)
 
       # Verify multivariate feature
       expect(context[:features]).to have_key('test_mv')
diff --git a/spec/engine/unit/segments/evaluator_spec.rb b/spec/engine/unit/segments/evaluator_spec.rb
deleted file mode 100644
index d89106b..0000000
--- a/spec/engine/unit/segments/evaluator_spec.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-# list of test cases containing: operator, property, value, traits (list of dicts), expected_result
-TEST_CASES = [
-    ['IS_SET', 'foo', nil, {}, false],
-    ['IS_SET', 'foo', nil, {'foo': 'bar'}, true],
-    ['IS_NOT_SET', 'foo', nil, {}, true],
-    ['IS_NOT_SET', 'foo', nil, {'foo': 'bar'}, false],
-]
-
-RSpec.describe Flagsmith::Engine::Segments::Evaluator do
-  subject { Class.new { extend Flagsmith::Engine::Segments::Evaluator } }
-
-  TEST_CASES.each do |(operator, property, value, traits, expected_result)|
-    it "traits: #{traits} #traits_match_segment_condition(#{operator}, #{property}, #{value || 'No value'}) should be #{expected_result}" do
-      condition = Flagsmith::Engine::Segments::Condition.new(
-        operator: operator, property: property, value: value
-      )
-      trait_models = traits.map { 
-        |k,v| Flagsmith::Engine::Identities::Trait.new(trait_key: k, trait_value: v) 
-      }
-
-      expect(subject.traits_match_segment_condition(
-        trait_models, condition, 1, 1)).to eq(expected_result)
-    end
-  end
-end
diff --git a/spec/engine/unit/segments/models_spec.rb b/spec/engine/unit/segments/models_spec.rb
index 517657a..1c50637 100644
--- a/spec/engine/unit/segments/models_spec.rb
+++ b/spec/engine/unit/segments/models_spec.rb
@@ -94,9 +94,7 @@
   ['IN', 1, '1,2,3,4', true],
   ['IN', 1, '', false],
   ['IN', 1, '1', true],
-  # Flagsmith's engine does not evaluate `IN` condition for floats/doubles and booleans
-  # due to ambiguous serialization across supported platforms.
-  ['IN', 1.5, '1.5', false],
+  ['IN', 1.5, '1.5', true],
   ['IN', false, 'false', false],
 ].freeze