diff --git a/api/core/workflow/nodes/human_input/entities.py b/api/core/workflow/nodes/human_input/entities.py
index 81b03d1958..65bf32cd61 100644
--- a/api/core/workflow/nodes/human_input/entities.py
+++ b/api/core/workflow/nodes/human_input/entities.py
@@ -259,3 +259,30 @@ class FormDefinition(BaseModel):
 
     # display_in_ui controls whether the form should be displayed in UI surfaces.
     display_in_ui: bool | None = None
+
+
+class HumanInputSubmissionValidationError(ValueError):
+    pass
+
+
+def validate_human_input_submission(
+    *,
+    inputs: Sequence[FormInput],
+    user_actions: Sequence[UserAction],
+    selected_action_id: str,
+    form_data: Mapping[str, Any],
+) -> None:
+    available_actions = {action.id for action in user_actions}
+    if selected_action_id not in available_actions:
+        raise HumanInputSubmissionValidationError(f"Invalid action: {selected_action_id}")
+
+    provided_inputs = set(form_data.keys())
+    missing_inputs = [
+        form_input.output_variable_name
+        for form_input in inputs
+        if form_input.output_variable_name not in provided_inputs
+    ]
+
+    if missing_inputs:
+        missing_list = ", ".join(missing_inputs)
+        raise HumanInputSubmissionValidationError(f"Missing required inputs: {missing_list}")
diff --git a/api/services/human_input_service.py b/api/services/human_input_service.py
index bf182fce48..d1d31a7ab6 100644
--- a/api/services/human_input_service.py
+++ b/api/services/human_input_service.py
@@ -9,7 +9,11 @@ from core.repositories.human_input_reposotiry import (
     HumanInputFormRecord,
     HumanInputFormSubmissionRepository,
 )
-from core.workflow.nodes.human_input.entities import FormDefinition
+from core.workflow.nodes.human_input.entities import (
+    FormDefinition,
+    HumanInputSubmissionValidationError,
+    validate_human_input_submission,
+)
 from core.workflow.nodes.human_input.enums import HumanInputFormStatus
 from libs.datetime_utils import naive_utc_now
 from libs.exception import BaseHTTPException
@@ -171,20 +175,15 @@ class HumanInputService:
 
     def _validate_submission(self, form: Form, selected_action_id: str, form_data: Mapping[str, Any]) -> None:
         definition = form.get_definition()
-
-        available_actions = {action.id for action in definition.user_actions}
-        if selected_action_id not in available_actions:
-            raise InvalidFormDataError(f"Invalid action: {selected_action_id}")
-
-        provided_inputs = set(form_data.keys())
-        missing_inputs = [
-            form_input.output_variable_name
-            for form_input in definition.inputs
-            if form_input.output_variable_name not in provided_inputs
-        ]
-
-        if missing_inputs:
-            raise InvalidFormDataError(f"Missing required inputs: {', '.join(missing_inputs)}")
+        try:
+            validate_human_input_submission(
+                inputs=definition.inputs,
+                user_actions=definition.user_actions,
+                selected_action_id=selected_action_id,
+                form_data=form_data,
+            )
+        except HumanInputSubmissionValidationError as exc:
+            raise InvalidFormDataError(str(exc)) from exc
 
     def _enqueue_resume(self, workflow_run_id: str) -> None:
         workflow_run_repo = DifyAPIRepositoryFactory.create_api_workflow_run_repository(self._session_factory)
diff --git a/api/services/workflow_service.py b/api/services/workflow_service.py
index 6b19cf4642..37679f89f6 100644
--- a/api/services/workflow_service.py
+++ b/api/services/workflow_service.py
@@ -24,7 +24,11 @@ from core.workflow.graph_events import GraphNodeEventBase, NodeRunFailedEvent, N
 from core.workflow.node_events import NodeRunResult
 from core.workflow.nodes import NodeType
 from core.workflow.nodes.base.node import Node
-from core.workflow.nodes.human_input.entities import DeliveryChannelConfig, HumanInputNodeData
+from core.workflow.nodes.human_input.entities import (
+    DeliveryChannelConfig,
+    HumanInputNodeData,
+    validate_human_input_submission,
+)
 from core.workflow.nodes.human_input.human_input_node import HumanInputNode
 from core.workflow.nodes.node_mapping import LATEST_VERSION, NODE_TYPE_CLASSES_MAPPING
 from core.workflow.nodes.start.entities import StartNodeData
@@ -833,21 +837,18 @@ class WorkflowService:
         )
         node_data = node.node_data
 
-        available_actions = {user_action.id for user_action in node_data.user_actions}
-        if action not in available_actions:
-            raise ValueError(f"Invalid action: {action}")
-
-        expected_inputs = {form_input.output_variable_name for form_input in node_data.inputs}
-        missing_inputs = [name for name in expected_inputs if name not in form_inputs]
-        if missing_inputs:
-            missing_list = ", ".join(sorted(missing_inputs))
-            raise ValueError(f"Missing inputs: {missing_list}")
+        validate_human_input_submission(
+            inputs=node_data.inputs,
+            user_actions=node_data.user_actions,
+            selected_action_id=action,
+            form_data=form_inputs,
+        )
 
         rendered_content = node._render_form_content_before_submission()
         outputs: dict[str, Any] = dict(form_inputs)
         outputs["__action_id"] = action
         outputs["__rendered_content"] = node._render_form_content_with_outputs(
-            node_data.form_content, outputs, node_data.outputs_field_names()
+            rendered_content, outputs, node_data.outputs_field_names()
         )
 
         enclosing_node_type_and_id = draft_workflow.get_enclosing_node_type_and_id(node_config)
diff --git a/api/tests/unit_tests/services/workflow/test_workflow_service.py b/api/tests/unit_tests/services/workflow/test_workflow_service.py
index 9700cbaf0e..9833c44543 100644
--- a/api/tests/unit_tests/services/workflow/test_workflow_service.py
+++ b/api/tests/unit_tests/services/workflow/test_workflow_service.py
@@ -1,9 +1,15 @@
+from contextlib import nullcontext
+from types import SimpleNamespace
 from unittest.mock import MagicMock
 
 import pytest
 
+from core.workflow.enums import NodeType
+from core.workflow.nodes.human_input.entities import FormInput, HumanInputNodeData, UserAction
+from core.workflow.nodes.human_input.enums import FormInputType
 from models.model import App
 from models.workflow import Workflow
+from services import workflow_service as workflow_service_module
 from services.workflow_service import WorkflowService
 
 
@@ -161,3 +167,111 @@ class TestWorkflowService:
         assert workflows == []
         assert has_more is False
         mock_session.scalars.assert_called_once()
+
+    def test_submit_human_input_form_preview_uses_rendered_content(
+        self, workflow_service: WorkflowService, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        service = workflow_service
+        node_data = HumanInputNodeData(
+            title="Human Input",
+            form_content="<p>{{#$output.name#}}</p>",
+            inputs=[FormInput(type=FormInputType.TEXT_INPUT, output_variable_name="name")],
+            user_actions=[UserAction(id="approve", title="Approve")],
+        )
+        node = MagicMock()
+        node.node_data = node_data
+        node._render_form_content_before_submission.return_value = "<p>preview</p>"
+        node._render_form_content_with_outputs.return_value = "<p>rendered</p>"
+
+        service._build_human_input_variable_pool = MagicMock(return_value=MagicMock())  # type: ignore[method-assign]
+        service._build_human_input_node = MagicMock(return_value=node)  # type: ignore[method-assign]
+
+        workflow = MagicMock()
+        workflow.get_node_config_by_id.return_value = {"id": "node-1", "data": {"type": NodeType.HUMAN_INPUT.value}}
+        workflow.get_enclosing_node_type_and_id.return_value = None
+        service.get_draft_workflow = MagicMock(return_value=workflow)  # type: ignore[method-assign]
+
+        saved_outputs: dict[str, object] = {}
+
+        class DummySession:
+            def __init__(self, *args, **kwargs):
+                self.commit = MagicMock()
+
+            def __enter__(self):
+                return self
+
+            def __exit__(self, exc_type, exc, tb):
+                return False
+
+            def begin(self):
+                return nullcontext()
+
+        class DummySaver:
+            def __init__(self, *args, **kwargs):
+                pass
+
+            def save(self, outputs, process_data):
+                saved_outputs.update(outputs)
+
+        monkeypatch.setattr(workflow_service_module, "Session", DummySession)
+        monkeypatch.setattr(workflow_service_module, "DraftVariableSaver", DummySaver)
+        monkeypatch.setattr(workflow_service_module, "db", SimpleNamespace(engine=MagicMock()))
+
+        app_model = SimpleNamespace(id="app-1", tenant_id="tenant-1")
+        account = SimpleNamespace(id="account-1")
+
+        result = service.submit_human_input_form_preview(
+            app_model=app_model,
+            account=account,
+            node_id="node-1",
+            form_inputs={"name": "Ada", "extra": "ignored"},
+            action="approve",
+        )
+
+        node._render_form_content_with_outputs.assert_called_once()
+        called_args = node._render_form_content_with_outputs.call_args.args
+        assert called_args[0] == "<p>preview</p>"
+        assert called_args[2] == node_data.outputs_field_names()
+        rendered_outputs = called_args[1]
+        assert rendered_outputs["name"] == "Ada"
+        assert rendered_outputs["extra"] == "ignored"
+        assert "extra" in saved_outputs
+        assert "extra" in result
+        assert saved_outputs["name"] == "Ada"
+        assert result["name"] == "Ada"
+        assert result["__action_id"] == "approve"
+        assert "__rendered_content" in result
+
+    def test_submit_human_input_form_preview_missing_inputs_message(self, workflow_service: WorkflowService) -> None:
+        service = workflow_service
+        node_data = HumanInputNodeData(
+            title="Human Input",
+            form_content="<p>{{#$output.name#}}</p>",
+            inputs=[FormInput(type=FormInputType.TEXT_INPUT, output_variable_name="name")],
+            user_actions=[UserAction(id="approve", title="Approve")],
+        )
+        node = MagicMock()
+        node.node_data = node_data
+        node._render_form_content_before_submission.return_value = "<p>preview</p>"
+        node._render_form_content_with_outputs.return_value = "<p>rendered</p>"
+
+        service._build_human_input_variable_pool = MagicMock(return_value=MagicMock())  # type: ignore[method-assign]
+        service._build_human_input_node = MagicMock(return_value=node)  # type: ignore[method-assign]
+
+        workflow = MagicMock()
+        workflow.get_node_config_by_id.return_value = {"id": "node-1", "data": {"type": NodeType.HUMAN_INPUT.value}}
+        service.get_draft_workflow = MagicMock(return_value=workflow)  # type: ignore[method-assign]
+
+        app_model = SimpleNamespace(id="app-1", tenant_id="tenant-1")
+        account = SimpleNamespace(id="account-1")
+
+        with pytest.raises(ValueError) as exc_info:
+            service.submit_human_input_form_preview(
+                app_model=app_model,
+                account=account,
+                node_id="node-1",
+                form_inputs={},
+                action="approve",
+            )
+
+        assert "Missing required inputs" in str(exc_info.value)