fix(workflow): sync iteration conversation variables (#26368)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

api/core/workflow/nodes/iteration/iteration_node.py

 
 from core.variables import IntegerVariable, NoneSegment
 from core.variables.segments import ArrayAnySegment, ArraySegment
+from core.variables.variables import VariableUnion
+from core.workflow.constants import CONVERSATION_VARIABLE_NODE_ID
 from core.workflow.entities import VariablePool
 from core.workflow.enums import (
     ErrorStrategy,
                     graph_engine=graph_engine,
                 )
 
+                # Sync conversation variables after each iteration completes
+                self._sync_conversation_variables_from_snapshot(
+                    self._extract_conversation_variable_snapshot(
+                        variable_pool=graph_engine.graph_runtime_state.variable_pool
+                    )
+                )
+
                 # Update the total tokens from this iteration
                 self.graph_runtime_state.total_tokens += graph_engine.graph_runtime_state.total_tokens
                 iter_run_map[str(index)] = (datetime.now(UTC).replace(tzinfo=None) - iter_start_at).total_seconds()
 
         with ThreadPoolExecutor(max_workers=max_workers) as executor:
             # Submit all iteration tasks
-            future_to_index: dict[Future[tuple[datetime, list[GraphNodeEventBase], object | None, int]], int] = {}
+            future_to_index: dict[
+                Future[tuple[datetime, list[GraphNodeEventBase], object | None, int, dict[str, VariableUnion]]],
+                int,
+            ] = {}
             for index, item in enumerate(iterator_list_value):
                 yield IterationNextEvent(index=index)
                 future = executor.submit(
                 index = future_to_index[future]
                 try:
                     result = future.result()
-                    iter_start_at, events, output_value, tokens_used = result
+                    iter_start_at, events, output_value, tokens_used, conversation_snapshot = result
 
                     # Update outputs at the correct index
                     outputs[index] = output_value
                     self.graph_runtime_state.total_tokens += tokens_used
                     iter_run_map[str(index)] = (datetime.now(UTC).replace(tzinfo=None) - iter_start_at).total_seconds()
 
+                    # Sync conversation variables after iteration completion
+                    self._sync_conversation_variables_from_snapshot(conversation_snapshot)
+
                 except Exception as e:
                     # Handle errors based on error_handle_mode
                     match self._node_data.error_handle_mode:
         item: object,
         flask_app: Flask,
         context_vars: contextvars.Context,
-    ) -> tuple[datetime, list[GraphNodeEventBase], object | None, int]:
+    ) -> tuple[datetime, list[GraphNodeEventBase], object | None, int, dict[str, VariableUnion]]:
         """Execute a single iteration in parallel mode and return results."""
         with preserve_flask_contexts(flask_app=flask_app, context_vars=context_vars):
             iter_start_at = datetime.now(UTC).replace(tzinfo=None)
 
             # Get the output value from the temporary outputs list
             output_value = outputs_temp[0] if outputs_temp else None
+            conversation_snapshot = self._extract_conversation_variable_snapshot(
+                variable_pool=graph_engine.graph_runtime_state.variable_pool
+            )
 
-            return iter_start_at, events, output_value, graph_engine.graph_runtime_state.total_tokens
+            return (
+                iter_start_at,
+                events,
+                output_value,
+                graph_engine.graph_runtime_state.total_tokens,
+                conversation_snapshot,
+            )
 
     def _handle_iteration_success(
         self,
 
         return variable_mapping
 
+    def _extract_conversation_variable_snapshot(self, *, variable_pool: VariablePool) -> dict[str, VariableUnion]:
+        conversation_variables = variable_pool.variable_dictionary.get(CONVERSATION_VARIABLE_NODE_ID, {})
+        return {name: variable.model_copy(deep=True) for name, variable in conversation_variables.items()}
+
+    def _sync_conversation_variables_from_snapshot(self, snapshot: dict[str, VariableUnion]) -> None:
+        parent_pool = self.graph_runtime_state.variable_pool
+        parent_conversations = parent_pool.variable_dictionary.get(CONVERSATION_VARIABLE_NODE_ID, {})
+
+        current_keys = set(parent_conversations.keys())
+        snapshot_keys = set(snapshot.keys())
+
+        for removed_key in current_keys - snapshot_keys:
+            parent_pool.remove((CONVERSATION_VARIABLE_NODE_ID, removed_key))
+
+        for name, variable in snapshot.items():
+            parent_pool.add((CONVERSATION_VARIABLE_NODE_ID, name), variable)
+
     def _append_iteration_info_to_event(
         self,
         event: GraphNodeEventBase,

api/tests/fixtures/workflow/update-conversation-variable-in-iteration.yml

+app:
+  description: 'This chatflow receives a sys.query, writes it into the `answer` variable,
+    and then outputs the `answer` variable.
+
+
+    `answer` is a conversation variable with a blank default value; it will be updated
+    in an iteration node.
+
+
+    if this chatflow works correctly, it will output the `sys.query` as the same.'
+  icon: 🤖
+  icon_background: '#FFEAD5'
+  mode: advanced-chat
+  name: update-conversation-variable-in-iteration
+  use_icon_as_answer_icon: false
+dependencies: []
+kind: app
+version: 0.4.0
+workflow:
+  conversation_variables:
+  - description: ''
+    id: c30af82d-b2ec-417d-a861-4dd78584faa4
+    name: answer
+    selector:
+    - conversation
+    - answer
+    value: ''
+    value_type: string
+  environment_variables: []
+  features:
+    file_upload:
+      allowed_file_extensions:
+      - .JPG
+      - .JPEG
+      - .PNG
+      - .GIF
+      - .WEBP
+      - .SVG
+      allowed_file_types:
+      - image
+      allowed_file_upload_methods:
+      - local_file
+      - remote_url
+      enabled: false
+      fileUploadConfig:
+        audio_file_size_limit: 50
+        batch_count_limit: 5
+        file_size_limit: 15
+        image_file_size_limit: 10
+        video_file_size_limit: 100
+        workflow_file_upload_limit: 10
+      image:
+        enabled: false
+        number_limits: 3
+        transfer_methods:
+        - local_file
+        - remote_url
+      number_limits: 3
+    opening_statement: ''
+    retriever_resource:
+      enabled: true
+    sensitive_word_avoidance:
+      enabled: false
+    speech_to_text:
+      enabled: false
+    suggested_questions: []
+    suggested_questions_after_answer:
+      enabled: false
+    text_to_speech:
+      enabled: false
+      language: ''
+      voice: ''
+  graph:
+    edges:
+    - data:
+        isInIteration: false
+        isInLoop: false
+        sourceType: start
+        targetType: code
+      id: 1759032354471-source-1759032363865-target
+      source: '1759032354471'
+      sourceHandle: source
+      target: '1759032363865'
+      targetHandle: target
+      type: custom
+      zIndex: 0
+    - data:
+        isInIteration: false
+        isInLoop: false
+        sourceType: code
+        targetType: iteration
+      id: 1759032363865-source-1759032379989-target
+      source: '1759032363865'
+      sourceHandle: source
+      target: '1759032379989'
+      targetHandle: target
+      type: custom
+      zIndex: 0
+    - data:
+        isInIteration: true
+        isInLoop: false
+        iteration_id: '1759032379989'
+        sourceType: iteration-start
+        targetType: assigner
+      id: 1759032379989start-source-1759032394460-target
+      source: 1759032379989start
+      sourceHandle: source
+      target: '1759032394460'
+      targetHandle: target
+      type: custom
+      zIndex: 1002
+    - data:
+        isInIteration: false
+        isInLoop: false
+        sourceType: iteration
+        targetType: answer
+      id: 1759032379989-source-1759032410331-target
+      source: '1759032379989'
+      sourceHandle: source
+      target: '1759032410331'
+      targetHandle: target
+      type: custom
+      zIndex: 0
+    - data:
+        isInIteration: true
+        isInLoop: false
+        iteration_id: '1759032379989'
+        sourceType: assigner
+        targetType: code
+      id: 1759032394460-source-1759032476318-target
+      source: '1759032394460'
+      sourceHandle: source
+      target: '1759032476318'
+      targetHandle: target
+      type: custom
+      zIndex: 1002
+    nodes:
+    - data:
+        selected: false
+        title: Start
+        type: start
+        variables: []
+      height: 52
+      id: '1759032354471'
+      position:
+        x: 30
+        y: 302
+      positionAbsolute:
+        x: 30
+        y: 302
+      selected: false
+      sourcePosition: right
+      targetPosition: left
+      type: custom
+      width: 242
+    - data:
+        code: "\ndef main():\n    return {\n        \"result\": [1],\n    }\n"
+        code_language: python3
+        outputs:
+          result:
+            children: null
+            type: array[number]
+        selected: false
+        title: Code
+        type: code
+        variables: []
+      height: 52
+      id: '1759032363865'
+      position:
+        x: 332
+        y: 302
+      positionAbsolute:
+        x: 332
+        y: 302
+      sourcePosition: right
+      targetPosition: left
+      type: custom
+      width: 242
+    - data:
+        error_handle_mode: terminated
+        height: 204
+        is_parallel: false
+        iterator_input_type: array[number]
+        iterator_selector:
+        - '1759032363865'
+        - result
+        output_selector:
+        - '1759032476318'
+        - result
+        output_type: array[string]
+        parallel_nums: 10
+        selected: false
+        start_node_id: 1759032379989start
+        title: Iteration
+        type: iteration
+        width: 808
+      height: 204
+      id: '1759032379989'
+      position:
+        x: 634
+        y: 302
+      positionAbsolute:
+        x: 634
+        y: 302
+      selected: true
+      sourcePosition: right
+      targetPosition: left
+      type: custom
+      width: 808
+      zIndex: 1
+    - data:
+        desc: ''
+        isInIteration: true
+        selected: false
+        title: ''
+        type: iteration-start
+      draggable: false
+      height: 48
+      id: 1759032379989start
+      parentId: '1759032379989'
+      position:
+        x: 60
+        y: 78
+      positionAbsolute:
+        x: 694
+        y: 380
+      selectable: false
+      sourcePosition: right
+      targetPosition: left
+      type: custom-iteration-start
+      width: 44
+      zIndex: 1002
+    - data:
+        isInIteration: true
+        isInLoop: false
+        items:
+        - input_type: variable
+          operation: over-write
+          value:
+          - sys
+          - query
+          variable_selector:
+          - conversation
+          - answer
+          write_mode: over-write
+        iteration_id: '1759032379989'
+        selected: false
+        title: Variable Assigner
+        type: assigner
+        version: '2'
+      height: 84
+      id: '1759032394460'
+      parentId: '1759032379989'
+      position:
+        x: 204
+        y: 60
+      positionAbsolute:
+        x: 838
+        y: 362
+      sourcePosition: right
+      targetPosition: left
+      type: custom
+      width: 242
+      zIndex: 1002
+    - data:
+        answer: '{{#conversation.answer#}}'
+        selected: false
+        title: Answer
+        type: answer
+        variables: []
+      height: 104
+      id: '1759032410331'
+      position:
+        x: 1502
+        y: 302
+      positionAbsolute:
+        x: 1502
+        y: 302
+      selected: false
+      sourcePosition: right
+      targetPosition: left
+      type: custom
+      width: 242
+    - data:
+        code: "\ndef main():\n    return {\n        \"result\": '',\n    }\n"
+        code_language: python3
+        isInIteration: true
+        isInLoop: false
+        iteration_id: '1759032379989'
+        outputs:
+          result:
+            children: null
+            type: string
+        selected: false
+        title: Code 2
+        type: code
+        variables: []
+      height: 52
+      id: '1759032476318'
+      parentId: '1759032379989'
+      position:
+        x: 506
+        y: 76
+      positionAbsolute:
+        x: 1140
+        y: 378
+      sourcePosition: right
+      targetPosition: left
+      type: custom
+      width: 242
+      zIndex: 1002
+    viewport:
+      x: 120.39999999999998
+      y: 85.20000000000005
+      zoom: 0.7
+  rag_pipeline_variables: []

api/tests/unit_tests/core/workflow/graph_engine/test_update_conversation_variable_iteration.py

+"""Validate conversation variable updates inside an iteration workflow.
+
+This test uses the ``update-conversation-variable-in-iteration`` fixture, which
+routes ``sys.query`` into the conversation variable ``answer`` from within an
+iteration container. The workflow should surface that updated conversation
+variable in the final answer output.
+
+Code nodes in the fixture are mocked because their concrete outputs are not
+relevant to verifying variable propagation semantics.
+"""
+
+from .test_mock_config import MockConfigBuilder
+from .test_table_runner import TableTestRunner, WorkflowTestCase
+
+
+def test_update_conversation_variable_in_iteration():
+    fixture_name = "update-conversation-variable-in-iteration"
+    user_query = "ensure conversation variable syncs"
+
+    mock_config = (
+        MockConfigBuilder()
+        .with_node_output("1759032363865", {"result": [1]})
+        .with_node_output("1759032476318", {"result": ""})
+        .build()
+    )
+
+    case = WorkflowTestCase(
+        fixture_path=fixture_name,
+        use_auto_mock=True,
+        mock_config=mock_config,
+        query=user_query,
+        expected_outputs={"answer": user_query},
+        description="Conversation variable updated within iteration should flow to answer output.",
+    )
+
+    runner = TableTestRunner()
+    result = runner.run_test_case(case)
+
+    assert result.success, f"Workflow execution failed: {result.error}"
+    assert result.actual_outputs is not None
+    assert result.actual_outputs.get("answer") == user_query