diff --git a/Gemfile b/Gemfile
index c824482d..cbabc137 100644
--- a/Gemfile
+++ b/Gemfile
@@ -79,7 +79,7 @@ gem 'good_job', '~> 4.0'
 gem 'rotp'
 
 gem 'grpc', '~> 1.67'
-gem 'tucana', '0.0.52'
+gem 'tucana', '0.0.53'
 
 gem 'code0-identities', '~> 0.0.3'
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 19349ef4..ccac940f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -377,7 +377,7 @@ GEM
     thor (1.4.0)
     timeout (0.6.0)
     tsort (0.2.0)
-    tucana (0.0.52)
+    tucana (0.0.53)
       grpc (~> 1.64)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
@@ -431,7 +431,7 @@ DEPENDENCIES
   simplecov (~> 0.22.0)
   simplecov-cobertura (~> 3.0)
   test-prof (~> 1.0)
-  tucana (= 0.0.52)
+  tucana (= 0.0.53)
   tzinfo-data
 
 RUBY VERSION
diff --git a/app/graphql/types/input/reference_value_input_type.rb b/app/graphql/types/input/reference_value_input_type.rb
index 22242959..ef0fcaac 100644
--- a/app/graphql/types/input/reference_value_input_type.rb
+++ b/app/graphql/types/input/reference_value_input_type.rb
@@ -6,9 +6,20 @@ class ReferenceValueInputType < Types::BaseInputObject
       description 'Input type for reference value'
 
       argument :reference_path, [Types::Input::ReferencePathInputType],
-               required: true, description: 'The paths associated with this reference value'
+               required: true,
+               description: 'The paths associated with this reference value'
 
-      argument :node_function_id, GlobalIdType[::NodeFunction], required: true, description: 'The referenced value'
+      argument :node_function_id, GlobalIdType[::NodeFunction],
+               required: false,
+               description: 'The referenced value unless referencing the flow input'
+
+      argument :parameter_index, GraphQL::Types::Int,
+               required: false,
+               description: 'The index of the referenced parameter'
+
+      argument :input_index, GraphQL::Types::Int,
+               required: false,
+               description: 'The index of the referenced input'
     end
   end
 end
diff --git a/app/graphql/types/reference_value_type.rb b/app/graphql/types/reference_value_type.rb
index bcc66f79..89ad4376 100644
--- a/app/graphql/types/reference_value_type.rb
+++ b/app/graphql/types/reference_value_type.rb
@@ -4,18 +4,28 @@ module Types
   class ReferenceValueType < Types::BaseObject
     description 'Represents a reference value in the system.'
 
-    field :node_function_id, GlobalIdType[::NodeFunction], null: false, description: 'The referenced value.'
+    field :node_function_id, GlobalIdType[::NodeFunction],
+          null: true,
+          description: 'The referenced value unless referencing the flow input.'
 
     field :reference_path, [Types::ReferencePathType],
           null: false,
           description: 'The paths associated with this reference value.',
           method: :reference_paths
 
+    field :parameter_index, GraphQL::Types::Int,
+          null: true,
+          description: 'The index of the referenced parameter'
+
+    field :input_index, GraphQL::Types::Int,
+          null: true,
+          description: 'The index of the referenced input'
+
     id_field ReferenceValue
     timestamps
 
     def node_function_id
-      object.node_function.to_global_id
+      object.node_function&.to_global_id
     end
   end
 end
diff --git a/app/models/flow.rb b/app/models/flow.rb
index d979fb2f..89f748d2 100644
--- a/app/models/flow.rb
+++ b/app/models/flow.rb
@@ -21,8 +21,8 @@ def to_grpc
       project_slug: project.slug,
       type: flow_type.identifier,
       data_types: [], # TODO: when data types are creatable
-      input_type_identifier: input_type&.identifier,
-      return_type_identifier: return_type&.identifier,
+      input_type: Tucana::Shared::DataTypeIdentifier.from_hash({ data_type_identifier: input_type&.identifier }),
+      return_type: Tucana::Shared::DataTypeIdentifier.from_hash({ data_type_identifier: return_type&.identifier }),
       settings: flow_settings.map(&:to_grpc),
       starting_node_id: starting_node.id,
       node_functions: node_functions.map(&:to_grpc)
diff --git a/app/models/reference_value.rb b/app/models/reference_value.rb
index c1a9dbb9..5a9d0327 100644
--- a/app/models/reference_value.rb
+++ b/app/models/reference_value.rb
@@ -1,14 +1,37 @@
 # frozen_string_literal: true
 
 class ReferenceValue < ApplicationRecord
-  belongs_to :node_function # real value association
+  belongs_to :node_function, optional: true # real value association
   has_many :reference_paths, inverse_of: :reference_value, autosave: true, dependent: :destroy
   has_many :node_parameters, inverse_of: :reference_value
 
+  validate :validate_indexes
+
+  def validate_indexes
+    return if parameter_index.nil? && input_index.nil?
+
+    errors.add(:node_function, :blank) if node_function.nil?
+    errors.add(:input_index, :blank) if parameter_index.present? && input_index.nil?
+    errors.add(:parameter_index, :blank) if input_index.present? && parameter_index.nil?
+  end
+
   def to_grpc
-    Tucana::Shared::ReferenceValue.new(
-      node_id: node_function.id,
+    reference_value = Tucana::Shared::ReferenceValue.new(
       paths: reference_paths.map(&:to_grpc)
     )
+
+    if node_function.nil?
+      reference_value.flow_input = Tucana::Shared::FlowInput.new
+    elsif parameter_index.present? && input_index.present?
+      reference_value.input_type = Tucana::Shared::InputType.new(
+        node_id: node_function.id,
+        parameter_index: parameter_index,
+        input_index: input_index
+      )
+    else
+      reference_value.node_id = node_function.id
+    end
+
+    reference_value
   end
 end
diff --git a/app/services/namespaces/projects/flows/update_service.rb b/app/services/namespaces/projects/flows/update_service.rb
index 50e5631a..141a9495 100644
--- a/app/services/namespaces/projects/flows/update_service.rb
+++ b/app/services/namespaces/projects/flows/update_service.rb
@@ -202,15 +202,19 @@ def update_node_parameters(t, current_node, current_node_input, all_nodes)
             end
 
             if parameter.value.reference_value.present?
-              referenced_node = all_nodes.find do |n|
-                n[:input].id == parameter.value.reference_value.node_function_id
-              end
-
-              if referenced_node.nil?
-                t.rollback_and_return! ServiceResponse.error(
-                  message: 'Referenced node function not found',
-                  error_code: :referenced_value_not_found
-                )
+              if parameter.value.reference_value.node_function_id.present?
+                referenced_node = all_nodes.find do |n|
+                  n[:input].id == parameter.value.reference_value.node_function_id
+                end
+
+                if referenced_node.nil?
+                  t.rollback_and_return! ServiceResponse.error(
+                    message: 'Referenced node function not found',
+                    error_code: :referenced_value_not_found
+                  )
+                end
+              else
+                referenced_node = { node: nil }
               end
 
               db_parameters[index].reference_value ||= ReferenceValue.new
@@ -225,7 +229,9 @@ def update_node_parameters(t, current_node, current_node_input, all_nodes)
 
               reference_value.assign_attributes(
                 node_function: referenced_node[:node],
-                reference_paths: reference_paths
+                reference_paths: reference_paths,
+                parameter_index: parameter.value.reference_value.parameter_index,
+                input_index: parameter.value.reference_value.input_index
               )
             else
               db_parameters[index].reference_value&.destroy
diff --git a/db/migrate/20260222154501_add_input_type_fields_to_reference_value.rb b/db/migrate/20260222154501_add_input_type_fields_to_reference_value.rb
new file mode 100644
index 00000000..40802362
--- /dev/null
+++ b/db/migrate/20260222154501_add_input_type_fields_to_reference_value.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class AddInputTypeFieldsToReferenceValue < Code0::ZeroTrack::Database::Migration[1.0]
+  def change
+    add_column :reference_values, :parameter_index, :int
+    add_column :reference_values, :input_index, :int
+
+    add_check_constraint :reference_values, 'num_nonnulls(parameter_index, input_index) IN (0, 2)',
+                         name: check_constraint_name(:reference_values, :indexes, :none_or_both)
+
+    change_column_null :reference_values, :node_function_id, true
+  end
+end
diff --git a/db/schema_migrations/20260222154501 b/db/schema_migrations/20260222154501
new file mode 100644
index 00000000..1ffa3866
--- /dev/null
+++ b/db/schema_migrations/20260222154501
@@ -0,0 +1 @@
+12fbf843d279b87a5a6da04d17a2ccb718a18979fe6eaeb53ed76e7ad131fb17
\ No newline at end of file
diff --git a/db/structure.sql b/db/structure.sql
index 14cb22f0..07280afb 100644
--- a/db/structure.sql
+++ b/db/structure.sql
@@ -668,7 +668,10 @@ CREATE TABLE reference_values (
     id bigint NOT NULL,
     created_at timestamp with time zone NOT NULL,
     updated_at timestamp with time zone NOT NULL,
-    node_function_id bigint NOT NULL
+    node_function_id bigint,
+    parameter_index integer,
+    input_index integer,
+    CONSTRAINT check_a2e3734389 CHECK ((num_nonnulls(parameter_index, input_index) = ANY (ARRAY[0, 2])))
 );
 
 CREATE SEQUENCE reference_values_id_seq
diff --git a/docs/graphql/input_object/referencevalueinput.md b/docs/graphql/input_object/referencevalueinput.md
index 842913f3..ed532bd2 100644
--- a/docs/graphql/input_object/referencevalueinput.md
+++ b/docs/graphql/input_object/referencevalueinput.md
@@ -8,5 +8,7 @@ Input type for reference value
 
 | Name | Type | Description |
 |------|------|-------------|
-| `nodeFunctionId` | [`NodeFunctionID!`](../scalar/nodefunctionid.md) | The referenced value |
+| `inputIndex` | [`Int`](../scalar/int.md) | The index of the referenced input |
+| `nodeFunctionId` | [`NodeFunctionID`](../scalar/nodefunctionid.md) | The referenced value unless referencing the flow input |
+| `parameterIndex` | [`Int`](../scalar/int.md) | The index of the referenced parameter |
 | `referencePath` | [`[ReferencePathInput!]!`](../input_object/referencepathinput.md) | The paths associated with this reference value |
diff --git a/docs/graphql/object/referencevalue.md b/docs/graphql/object/referencevalue.md
index b50d76ed..24b8b549 100644
--- a/docs/graphql/object/referencevalue.md
+++ b/docs/graphql/object/referencevalue.md
@@ -10,7 +10,9 @@ Represents a reference value in the system.
 |------|------|-------------|
 | `createdAt` | [`Time!`](../scalar/time.md) | Time when this ReferenceValue was created |
 | `id` | [`ReferenceValueID!`](../scalar/referencevalueid.md) | Global ID of this ReferenceValue |
-| `nodeFunctionId` | [`NodeFunctionID!`](../scalar/nodefunctionid.md) | The referenced value. |
+| `inputIndex` | [`Int`](../scalar/int.md) | The index of the referenced input |
+| `nodeFunctionId` | [`NodeFunctionID`](../scalar/nodefunctionid.md) | The referenced value unless referencing the flow input. |
+| `parameterIndex` | [`Int`](../scalar/int.md) | The index of the referenced parameter |
 | `referencePath` | [`[ReferencePath!]!`](../object/referencepath.md) | The paths associated with this reference value. |
 | `updatedAt` | [`Time!`](../scalar/time.md) | Time when this ReferenceValue was last updated |
 
diff --git a/spec/factories/reference_values.rb b/spec/factories/reference_values.rb
index 9bdc12f0..5b42a9e8 100644
--- a/spec/factories/reference_values.rb
+++ b/spec/factories/reference_values.rb
@@ -3,5 +3,7 @@
 FactoryBot.define do
   factory :reference_value do
     node_function
+    parameter_index { nil }
+    input_index { nil }
   end
 end
diff --git a/spec/models/flow_spec.rb b/spec/models/flow_spec.rb
index d57efd3a..37ee710f 100644
--- a/spec/models/flow_spec.rb
+++ b/spec/models/flow_spec.rb
@@ -69,6 +69,8 @@
           project_id: flow.project.id,
           project_slug: flow.project.slug,
           type: flow.flow_type.identifier,
+          input_type: {},
+          return_type: {},
           node_functions: [
             {
               database_id: starting_node.id,
diff --git a/spec/models/reference_value_spec.rb b/spec/models/reference_value_spec.rb
index f4cd8c16..576ebecb 100644
--- a/spec/models/reference_value_spec.rb
+++ b/spec/models/reference_value_spec.rb
@@ -3,12 +3,36 @@
 require 'rails_helper'
 
 RSpec.describe ReferenceValue do
-  subject do
+  subject(:reference_value) do
     create(:reference_value, node_function: create(:node_function))
   end
 
   describe 'associations' do
-    it { is_expected.to belong_to(:node_function) }
+    it { is_expected.to belong_to(:node_function).optional }
     it { is_expected.to have_many(:reference_paths) }
   end
+
+  describe 'validations' do
+    describe 'validate_indexes' do
+      it do
+        reference_value.parameter_index = 1
+        is_expected.not_to be_valid
+      end
+
+      it do
+        reference_value.input_index = 1
+        is_expected.not_to be_valid
+      end
+
+      it do
+        reference_value.parameter_index = 1
+        reference_value.input_index = 1
+        is_expected.to be_valid
+      end
+
+      it do
+        is_expected.to be_valid
+      end
+    end
+  end
 end
diff --git a/spec/requests/graphql/mutation/namespace/projects/flows/update_mutation_spec.rb b/spec/requests/graphql/mutation/namespace/projects/flows/update_mutation_spec.rb
index f14f5e83..c31b35f6 100644
--- a/spec/requests/graphql/mutation/namespace/projects/flows/update_mutation_spec.rb
+++ b/spec/requests/graphql/mutation/namespace/projects/flows/update_mutation_spec.rb
@@ -37,6 +37,8 @@
                           id
                           path
                         }
+                        parameterIndex
+                        inputIndex
                         updatedAt
                       }
                     }
@@ -125,16 +127,33 @@
             id: 'gid://sagittarius/NodeFunction/1001',
             functionDefinitionId: function_definition.to_global_id.to_s,
             parameters: [
-              parameterDefinitionId: function_definition.parameter_definitions.first.to_global_id.to_s,
-              value: {
-                referenceValue: {
-                  referencePath: [
-                    {
-                      arrayIndex: 0,
-                      path: 'some.path',
-                    }
-                  ],
-                  nodeFunctionId: 'gid://sagittarius/NodeFunction/2000',
+              {
+                parameterDefinitionId: function_definition.parameter_definitions.first.to_global_id.to_s,
+                value: {
+                  referenceValue: {
+                    referencePath: [
+                      {
+                        arrayIndex: 0,
+                        path: 'some.path',
+                      }
+                    ],
+                    nodeFunctionId: 'gid://sagittarius/NodeFunction/2000',
+                    parameterIndex: 1,
+                    inputIndex: 1,
+                  },
+                },
+              },
+              {
+                parameterDefinitionId: function_definition.parameter_definitions.first.to_global_id.to_s,
+                value: {
+                  referenceValue: {
+                    referencePath: [
+                      {
+                        arrayIndex: 1,
+                        path: 'some.path',
+                      }
+                    ],
+                  },
                 },
               }
             ],
@@ -181,9 +200,26 @@
         :nodes,
         :value
       )
-      expect(parameter_values).to include(a_hash_including('value' => 100))
       expect(parameter_values).to include(
-        a_hash_including('referencePath' => [a_hash_including('arrayIndex' => 0, 'path' => 'some.path')])
+        a_hash_including(
+          '__typename' => 'LiteralValue',
+          'value' => 100
+        )
+      )
+      expect(parameter_values).to include(
+        a_hash_including(
+          '__typename' => 'ReferenceValue',
+          'nodeFunctionId' => a_string_matching(%r{gid://sagittarius/NodeFunction/\d+}),
+          'referencePath' => [a_hash_including('arrayIndex' => 0, 'path' => 'some.path')],
+          'parameterIndex' => 1,
+          'inputIndex' => 1
+        )
+      )
+      expect(parameter_values).to include(
+        a_hash_including(
+          '__typename' => 'ReferenceValue',
+          'referencePath' => [a_hash_including('arrayIndex' => 1, 'path' => 'some.path')]
+        )
       )
 
       is_expected.to create_audit_event(