feat: add vibe workflow (#30258)

Co-authored-by: yyh <yuanyouhuilyz@gmail.com>

api/controllers/console/app/generator.py

@@ -1,9 +1,13 @@
+import logging
 from collections.abc import Sequence
 from typing import Any
 
 from flask_restx import Resource
 from pydantic import BaseModel, Field
 
+logger = logging.getLogger(__name__)
+
+
 from controllers.console import console_ns
 from controllers.console.app.error import (
     CompletionRequestError,
@@ -18,6 +22,7 @@ from core.helper.code_executor.javascript.javascript_code_provider import Javasc
 from core.helper.code_executor.python3.python3_code_provider import Python3CodeProvider
 from core.llm_generator.llm_generator import LLMGenerator
 from core.model_runtime.errors.invoke import InvokeError
+from core.workflow.generator import WorkflowGenerator
 from extensions.ext_database import db
 from libs.login import current_account_with_tenant, login_required
 from models import App
@@ -55,12 +60,28 @@ class InstructionTemplatePayload(BaseModel):
     type: str = Field(..., description="Instruction template type")
 
 
+class PreviousWorkflow(BaseModel):
+    """Previous workflow attempt for regeneration context."""
+
+    nodes: list[dict[str, Any]] = Field(default_factory=list, description="Previously generated nodes")
+    edges: list[dict[str, Any]] = Field(default_factory=list, description="Previously generated edges")
+    warnings: list[str] = Field(default_factory=list, description="Warnings from previous generation")
+
+
 class FlowchartGeneratePayload(BaseModel):
     instruction: str = Field(..., description="Workflow flowchart generation instruction")
     model_config_data: dict[str, Any] = Field(..., alias="model_config", description="Model configuration")
     available_nodes: list[dict[str, Any]] = Field(default_factory=list, description="Available node types")
     existing_nodes: list[dict[str, Any]] = Field(default_factory=list, description="Existing workflow nodes")
+    existing_edges: list[dict[str, Any]] = Field(default_factory=list, description="Existing workflow edges")
     available_tools: list[dict[str, Any]] = Field(default_factory=list, description="Available tools")
+    selected_node_ids: list[str] = Field(default_factory=list, description="IDs of selected nodes for context")
+    previous_workflow: PreviousWorkflow | None = Field(default=None, description="Previous workflow for regeneration")
+    regenerate_mode: bool = Field(default=False, description="Whether this is a regeneration request")
+    # Language preference for generated content (node titles, descriptions)
+    language: str | None = Field(default=None, description="Preferred language for generated content")
+    # Available models that user has configured (for LLM/question-classifier nodes)
+    available_models: list[dict[str, Any]] = Field(default_factory=list, description="User's configured models")
 
 
 def reg(cls: type[BaseModel]):
@@ -267,7 +288,7 @@ class InstructionGenerateApi(Resource):
 @console_ns.route("/flowchart-generate")
 class FlowchartGenerateApi(Resource):
     @console_ns.doc("generate_workflow_flowchart")
-    @console_ns.doc(description="Generate workflow flowchart using LLM")
+    @console_ns.doc(description="Generate workflow flowchart using LLM with intent classification")
     @console_ns.expect(console_ns.models[FlowchartGeneratePayload.__name__])
     @console_ns.response(200, "Flowchart generated successfully")
     @console_ns.response(400, "Invalid request parameters")
@@ -280,14 +301,24 @@ class FlowchartGenerateApi(Resource):
         _, current_tenant_id = current_account_with_tenant()
 
         try:
-            result = LLMGenerator.generate_workflow_flowchart(
+            # Convert PreviousWorkflow to dict if present
+            previous_workflow_dict = args.previous_workflow.model_dump() if args.previous_workflow else None
+
+            result = WorkflowGenerator.generate_workflow_flowchart(
                 tenant_id=current_tenant_id,
                 instruction=args.instruction,
                 model_config=args.model_config_data,
                 available_nodes=args.available_nodes,
                 existing_nodes=args.existing_nodes,
+                existing_edges=args.existing_edges,
                 available_tools=args.available_tools,
+                selected_node_ids=args.selected_node_ids,
+                previous_workflow=previous_workflow_dict,
+                regenerate_mode=args.regenerate_mode,
+                preferred_language=args.language,
+                available_models=args.available_models,
             )
+
         except ProviderTokenNotInitError as ex:
             raise ProviderNotInitializeError(ex.description)
         except QuotaExceededError:

api/core/llm_generator/llm_generator.py

@@ -1,6 +1,5 @@
 import json
 import logging
-import re
 from collections.abc import Sequence
 from typing import Protocol, cast
 
@@ -12,13 +11,10 @@ from core.llm_generator.prompts import (
     CONVERSATION_TITLE_PROMPT,
     GENERATOR_QA_PROMPT,
     JAVASCRIPT_CODE_GENERATOR_PROMPT_TEMPLATE,
-    LLM_MODIFY_CODE_SYSTEM,
-    LLM_MODIFY_PROMPT_SYSTEM,
     PYTHON_CODE_GENERATOR_PROMPT_TEMPLATE,
     SUGGESTED_QUESTIONS_MAX_TOKENS,
     SUGGESTED_QUESTIONS_TEMPERATURE,
     SYSTEM_STRUCTURED_OUTPUT_GENERATE,
-    WORKFLOW_FLOWCHART_PROMPT_TEMPLATE,
     WORKFLOW_RULE_CONFIG_PROMPT_GENERATE_TEMPLATE,
 )
 from core.model_manager import ModelManager
@@ -31,6 +27,7 @@ from core.ops.ops_trace_manager import TraceQueueManager, TraceTask
 from core.ops.utils import measure_time
 from core.prompt.utils.prompt_template_parser import PromptTemplateParser
 from core.workflow.entities.workflow_node_execution import WorkflowNodeExecutionMetadataKey
+from core.workflow.generator import WorkflowGenerator
 from extensions.ext_database import db
 from extensions.ext_storage import storage
 from models import App, Message, WorkflowNodeExecutionModel
@@ -295,52 +292,26 @@ class LLMGenerator:
         available_nodes: Sequence[dict[str, object]] | None = None,
         existing_nodes: Sequence[dict[str, object]] | None = None,
         available_tools: Sequence[dict[str, object]] | None = None,
+        selected_node_ids: Sequence[str] | None = None,
+        previous_workflow: dict[str, object] | None = None,
+        regenerate_mode: bool = False,
+        preferred_language: str | None = None,
+        available_models: Sequence[dict[str, object]] | None = None,
     ):
-        model_parameters = model_config.get("completion_params", {})
-        prompt_template = PromptTemplateParser(WORKFLOW_FLOWCHART_PROMPT_TEMPLATE)
-        prompt_generate = prompt_template.format(
-            inputs={
-                "TASK_DESCRIPTION": instruction,
-                "AVAILABLE_NODES": json.dumps(available_nodes or [], ensure_ascii=False),
-                "EXISTING_NODES": json.dumps(existing_nodes or [], ensure_ascii=False),
-                "AVAILABLE_TOOLS": json.dumps(available_tools or [], ensure_ascii=False),
-            },
-            remove_template_variables=False,
-        )
-
-        prompt_messages = [UserPromptMessage(content=prompt_generate)]
-
-        model_manager = ModelManager()
-        model_instance = model_manager.get_model_instance(
+        return WorkflowGenerator.generate_workflow_flowchart(
             tenant_id=tenant_id,
-            model_type=ModelType.LLM,
-            provider=model_config.get("provider", ""),
-            model=model_config.get("name", ""),
+            instruction=instruction,
+            model_config=model_config,
+            available_nodes=available_nodes,
+            existing_nodes=existing_nodes,
+            available_tools=available_tools,
+            selected_node_ids=selected_node_ids,
+            previous_workflow=previous_workflow,
+            regenerate_mode=regenerate_mode,
+            preferred_language=preferred_language,
+            available_models=available_models,
         )
 
-        flowchart = ""
-        error = ""
-
-        try:
-            response: LLMResult = model_instance.invoke_llm(
-                prompt_messages=list(prompt_messages),
-                model_parameters=model_parameters,
-                stream=False,
-            )
-            content = response.message.get_text_content()
-            if not isinstance(content, str):
-                raise ValueError("Flowchart response is not a string")
-
-            match = re.search(r"```(?:mermaid)?\s*([\s\S]+?)```", content, flags=re.IGNORECASE)
-            flowchart = (match.group(1) if match else content).strip()
-        except InvokeError as e:
-            error = str(e)
-        except Exception as e:
-            logger.exception("Failed to generate workflow flowchart, model: %s", model_config.get("name"))
-            error = str(e)
-
-        return {"flowchart": flowchart, "error": error}
-
     @classmethod
     def generate_code(cls, tenant_id: str, instruction: str, model_config: dict, code_language: str = "javascript"):
         if code_language == "python":

api/core/llm_generator/prompts.py

@@ -147,6 +147,8 @@ WORKFLOW_FLOWCHART_PROMPT_TEMPLATE = """
 You are an expert workflow designer. Generate a Mermaid flowchart based on the user's request.
 
 Constraints:
+- Detect the language of the user's request. Generate all node titles in the same language as the user's input.
+- If the input language cannot be determined, use {{PREFERRED_LANGUAGE}} as the fallback language.
 - Use only node types listed in <available_nodes>.
 - Use only tools listed in <available_tools>. When using a tool node, set type=tool and tool=<tool_key>.
 - Tools may include MCP providers (provider_type=mcp). Tool selection still uses tool_key.

api/core/workflow/generator/__init__.py

@@ -0,0 +1 @@
+from .runner import WorkflowGenerator

api/core/workflow/generator/config/__init__.py

@@ -0,0 +1,29 @@
+"""
+Vibe Workflow Generator Configuration Module.
+
+This module centralizes configuration for the Vibe workflow generation feature,
+including node schemas, fallback rules, and response templates.
+"""
+
+from core.workflow.generator.config.node_schemas import (
+    BUILTIN_NODE_SCHEMAS,
+    FALLBACK_RULES,
+    FIELD_NAME_CORRECTIONS,
+    NODE_TYPE_ALIASES,
+    get_builtin_node_schemas,
+    get_corrected_field_name,
+    validate_node_schemas,
+)
+from core.workflow.generator.config.responses import DEFAULT_SUGGESTIONS, OFF_TOPIC_RESPONSES
+
+__all__ = [
+    "BUILTIN_NODE_SCHEMAS",
+    "DEFAULT_SUGGESTIONS",
+    "FALLBACK_RULES",
+    "FIELD_NAME_CORRECTIONS",
+    "NODE_TYPE_ALIASES",
+    "OFF_TOPIC_RESPONSES",
+    "get_builtin_node_schemas",
+    "get_corrected_field_name",
+    "validate_node_schemas",
+]

api/core/workflow/generator/config/node_schemas.py

@@ -0,0 +1,501 @@
+"""
+Unified Node Configuration for Vibe Workflow Generation.
+
+This module centralizes all node-related configuration:
+- Node schemas (parameter definitions)
+- Fallback rules (keyword-based node type inference)
+- Node type aliases (natural language to canonical type mapping)
+- Field name corrections (LLM output normalization)
+- Validation utilities
+
+Note: These definitions are the single source of truth.
+Frontend has a mirrored copy at web/app/components/workflow/hooks/use-workflow-vibe-config.ts
+"""
+
+from typing import Any
+
+# =============================================================================
+# NODE SCHEMAS
+# =============================================================================
+
+# Built-in node schemas with parameter definitions
+# These help the model understand what config each node type requires
+_HARDCODED_SCHEMAS: dict[str, dict[str, Any]] = {
+    "http-request": {
+        "description": "Send HTTP requests to external APIs or fetch web content",
+        "required": ["url", "method"],
+        "parameters": {
+            "url": {
+                "type": "string",
+                "description": "Full URL including protocol (https://...)",
+                "example": "{{#start.url#}} or https://api.example.com/data",
+            },
+            "method": {
+                "type": "enum",
+                "options": ["GET", "POST", "PUT", "DELETE", "PATCH", "HEAD"],
+                "description": "HTTP method",
+            },
+            "headers": {
+                "type": "string",
+                "description": "HTTP headers as newline-separated 'Key: Value' pairs",
+                "example": "Content-Type: application/json\nAuthorization: Bearer {{#start.api_key#}}",
+            },
+            "params": {
+                "type": "string",
+                "description": "URL query parameters as newline-separated 'key: value' pairs",
+            },
+            "body": {
+                "type": "object",
+                "description": "Request body with type field required",
+                "example": {"type": "none", "data": []},
+            },
+            "authorization": {
+                "type": "object",
+                "description": "Authorization config",
+                "example": {"type": "no-auth"},
+            },
+            "timeout": {
+                "type": "number",
+                "description": "Request timeout in seconds",
+                "default": 60,
+            },
+        },
+        "outputs": ["body (response content)", "status_code", "headers"],
+    },
+    "code": {
+        "description": "Execute Python or JavaScript code for custom logic",
+        "required": ["code", "language"],
+        "parameters": {
+            "code": {
+                "type": "string",
+                "description": "Code to execute. Must define a main() function that returns a dict.",
+            },
+            "language": {
+                "type": "enum",
+                "options": ["python3", "javascript"],
+            },
+            "variables": {
+                "type": "array",
+                "description": "Input variables passed to the code",
+                "item_schema": {"variable": "string", "value_selector": "array"},
+            },
+            "outputs": {
+                "type": "object",
+                "description": "Output variable definitions",
+            },
+        },
+        "outputs": ["Variables defined in outputs schema"],
+    },
+    "llm": {
+        "description": "Call a large language model for text generation/processing",
+        "required": ["prompt_template"],
+        "parameters": {
+            "model": {
+                "type": "object",
+                "description": "Model configuration (provider, name, mode)",
+            },
+            "prompt_template": {
+                "type": "array",
+                "description": "Messages for the LLM",
+                "item_schema": {
+                    "role": "enum: system, user, assistant",
+                    "text": "string - message content, can include {{#node_id.field#}} references",
+                },
+            },
+            "context": {
+                "type": "object",
+                "description": "Optional context settings",
+            },
+            "memory": {
+                "type": "object",
+                "description": "Optional memory/conversation settings",
+            },
+        },
+        "outputs": ["text (generated response)"],
+    },
+    "if-else": {
+        "description": "Conditional branching based on conditions",
+        "required": ["cases"],
+        "parameters": {
+            "cases": {
+                "type": "array",
+                "description": "List of condition cases. Each case defines when 'true' branch is taken.",
+                "item_schema": {
+                    "case_id": "string - unique case identifier (e.g., 'case_1')",
+                    "logical_operator": "enum: and, or - how multiple conditions combine",
+                    "conditions": {
+                        "type": "array",
+                        "item_schema": {
+                            "variable_selector": "array of strings - path to variable, e.g. ['node_id', 'field']",
+                            "comparison_operator": (
+                                "enum: =, ≠, >, <, ≥, ≤, contains, not contains, is, is not, empty, not empty"
+                            ),
+                            "value": "string or number - value to compare against",
+                        },
+                    },
+                },
+            },
+        },
+        "outputs": ["Branches: true (first case conditions met), false (else/no case matched)"],
+    },
+    "knowledge-retrieval": {
+        "description": "Query knowledge base for relevant content",
+        "required": ["query_variable_selector", "dataset_ids"],
+        "parameters": {
+            "query_variable_selector": {
+                "type": "array",
+                "description": "Path to query variable, e.g. ['start', 'query']",
+            },
+            "dataset_ids": {
+                "type": "array",
+                "description": "List of knowledge base IDs to search",
+            },
+            "retrieval_mode": {
+                "type": "enum",
+                "options": ["single", "multiple"],
+            },
+        },
+        "outputs": ["result (retrieved documents)"],
+    },
+    "template-transform": {
+        "description": "Transform data using Jinja2 templates",
+        "required": ["template", "variables"],
+        "parameters": {
+            "template": {
+                "type": "string",
+                "description": "Jinja2 template string. Use {{ variable_name }} to reference variables.",
+            },
+            "variables": {
+                "type": "array",
+                "description": "Input variables defined for the template",
+                "item_schema": {
+                    "variable": "string - variable name to use in template",
+                    "value_selector": "array - path to source value, e.g. ['start', 'user_input']",
+                },
+            },
+        },
+        "outputs": ["output (transformed string)"],
+    },
+    "variable-aggregator": {
+        "description": "Aggregate variables from multiple branches",
+        "required": ["variables"],
+        "parameters": {
+            "variables": {
+                "type": "array",
+                "description": "List of variable selectors to aggregate",
+                "item_schema": "array of strings - path to source variable, e.g. ['node_id', 'field']",
+            },
+        },
+        "outputs": ["output (aggregated value)"],
+    },
+    "iteration": {
+        "description": "Loop over array items",
+        "required": ["iterator_selector"],
+        "parameters": {
+            "iterator_selector": {
+                "type": "array",
+                "description": "Path to array variable to iterate",
+            },
+        },
+        "outputs": ["item (current iteration item)", "index (current index)"],
+    },
+    "parameter-extractor": {
+        "description": "Extract structured parameters from user input using LLM",
+        "required": ["query", "parameters"],
+        "parameters": {
+            "model": {
+                "type": "object",
+                "description": "Model configuration (provider, name, mode)",
+            },
+            "query": {
+                "type": "array",
+                "description": "Path to input text to extract parameters from, e.g. ['start', 'user_input']",
+            },
+            "parameters": {
+                "type": "array",
+                "description": "Parameters to extract from the input",
+                "item_schema": {
+                    "name": "string - parameter name (required)",
+                    "type": (
+                        "enum: string, number, boolean, array[string], array[number], array[object], array[boolean]"
+                    ),
+                    "description": "string - description of what to extract (required)",
+                    "required": "boolean - whether this parameter is required (MUST be specified)",
+                    "options": "array of strings (optional) - for enum-like selection",
+                },
+            },
+            "instruction": {
+                "type": "string",
+                "description": "Additional instructions for extraction",
+            },
+            "reasoning_mode": {
+                "type": "enum",
+                "options": ["function_call", "prompt"],
+                "description": "How to perform extraction (defaults to function_call)",
+            },
+        },
+        "outputs": ["Extracted parameters as defined in parameters array", "__is_success", "__reason"],
+    },
+    "question-classifier": {
+        "description": "Classify user input into predefined categories using LLM",
+        "required": ["query", "classes"],
+        "parameters": {
+            "model": {
+                "type": "object",
+                "description": "Model configuration (provider, name, mode)",
+            },
+            "query": {
+                "type": "array",
+                "description": "Path to input text to classify, e.g. ['start', 'user_input']",
+            },
+            "classes": {
+                "type": "array",
+                "description": "Classification categories",
+                "item_schema": {
+                    "id": "string - unique class identifier",
+                    "name": "string - class name/label",
+                },
+            },
+            "instruction": {
+                "type": "string",
+                "description": "Additional instructions for classification",
+            },
+        },
+        "outputs": ["class_name (selected class)"],
+    },
+}
+
+
+def _get_dynamic_schemas() -> dict[str, dict[str, Any]]:
+    """
+    Dynamically load schemas from node classes.
+    Uses lazy import to avoid circular dependency.
+    """
+    from core.workflow.nodes.node_mapping import LATEST_VERSION, NODE_TYPE_CLASSES_MAPPING
+
+    schemas = {}
+    for node_type, version_map in NODE_TYPE_CLASSES_MAPPING.items():
+        # Get the latest version class
+        node_cls = version_map.get(LATEST_VERSION)
+        if not node_cls:
+            continue
+
+        # Get schema from the class
+        schema = node_cls.get_default_config_schema()
+        if schema:
+            schemas[node_type.value] = schema
+
+    return schemas
+
+
+# Cache for built-in schemas (populated on first access)
+_builtin_schemas_cache: dict[str, dict[str, Any]] | None = None
+
+
+def get_builtin_node_schemas() -> dict[str, dict[str, Any]]:
+    """
+    Get the complete set of built-in node schemas.
+    Combines hardcoded schemas with dynamically loaded ones.
+    Results are cached after first call.
+    """
+    global _builtin_schemas_cache
+    if _builtin_schemas_cache is None:
+        _builtin_schemas_cache = {**_HARDCODED_SCHEMAS, **_get_dynamic_schemas()}
+    return _builtin_schemas_cache
+
+
+# For backward compatibility - but use get_builtin_node_schemas() for lazy loading
+BUILTIN_NODE_SCHEMAS: dict[str, dict[str, Any]] = _HARDCODED_SCHEMAS.copy()
+
+
+# =============================================================================
+# FALLBACK RULES
+# =============================================================================
+
+# Keyword rules for smart fallback detection
+# Maps node type to keywords that suggest using that node type as a fallback
+FALLBACK_RULES: dict[str, list[str]] = {
+    "http-request": [
+        "http",
+        "url",
+        "web",
+        "scrape",
+        "scraper",
+        "fetch",
+        "api",
+        "request",
+        "download",
+        "upload",
+        "webhook",
+        "endpoint",
+        "rest",
+        "get",
+        "post",
+    ],
+    "code": [
+        "code",
+        "script",
+        "calculate",
+        "compute",
+        "process",
+        "transform",
+        "parse",
+        "convert",
+        "format",
+        "filter",
+        "sort",
+        "math",
+        "logic",
+    ],
+    "llm": [
+        "analyze",
+        "summarize",
+        "summary",
+        "extract",
+        "classify",
+        "translate",
+        "generate",
+        "write",
+        "rewrite",
+        "explain",
+        "answer",
+        "chat",
+    ],
+}
+
+
+# =============================================================================
+# NODE TYPE ALIASES
+# =============================================================================
+
+# Node type aliases for inference from natural language
+# Maps common terms to canonical node type names
+NODE_TYPE_ALIASES: dict[str, str] = {
+    # Start node aliases
+    "start": "start",
+    "begin": "start",
+    "input": "start",
+    # End node aliases
+    "end": "end",
+    "finish": "end",
+    "output": "end",
+    # LLM node aliases
+    "llm": "llm",
+    "ai": "llm",
+    "gpt": "llm",
+    "model": "llm",
+    "chat": "llm",
+    # Code node aliases
+    "code": "code",
+    "script": "code",
+    "python": "code",
+    "javascript": "code",
+    # HTTP request node aliases
+    "http-request": "http-request",
+    "http": "http-request",
+    "request": "http-request",
+    "api": "http-request",
+    "fetch": "http-request",
+    "webhook": "http-request",
+    # Conditional node aliases
+    "if-else": "if-else",
+    "condition": "if-else",
+    "branch": "if-else",
+    "switch": "if-else",
+    # Loop node aliases
+    "iteration": "iteration",
+    "loop": "loop",
+    "foreach": "iteration",
+    # Tool node alias
+    "tool": "tool",
+}
+
+
+# =============================================================================
+# FIELD NAME CORRECTIONS
+# =============================================================================
+
+# Field name corrections for LLM-generated node configs
+# Maps incorrect field names to correct ones for specific node types
+FIELD_NAME_CORRECTIONS: dict[str, dict[str, str]] = {
+    "http-request": {
+        "text": "body",  # LLM might use "text" instead of "body"
+        "content": "body",
+        "response": "body",
+    },
+    "code": {
+        "text": "result",  # LLM might use "text" instead of "result"
+        "output": "result",
+    },
+    "llm": {
+        "response": "text",
+        "answer": "text",
+    },
+}
+
+
+def get_corrected_field_name(node_type: str, field: str) -> str:
+    """
+    Get the corrected field name for a node type.
+
+    Args:
+        node_type: The type of the node (e.g., "http-request", "code")
+        field: The field name to correct
+
+    Returns:
+        The corrected field name, or the original if no correction needed
+    """
+    corrections = FIELD_NAME_CORRECTIONS.get(node_type, {})
+    return corrections.get(field, field)
+
+
+# =============================================================================
+# VALIDATION UTILITIES
+# =============================================================================
+
+# Node types that are internal and don't need schemas for LLM generation
+_INTERNAL_NODE_TYPES: set[str] = {
+    # Internal workflow nodes
+    "answer",  # Internal to chatflow
+    "loop",  # Uses iteration internally
+    "assigner",  # Variable assignment utility
+    "variable-assigner",  # Variable assignment utility
+    "agent",  # Agent node (complex, handled separately)
+    "document-extractor",  # Internal document processing
+    "list-operator",  # Internal list operations
+    # Iteration internal nodes
+    "iteration-start",  # Internal to iteration loop
+    "loop-start",  # Internal to loop
+    "loop-end",  # Internal to loop
+    # Trigger nodes (not user-creatable via LLM)
+    "trigger-plugin",  # Plugin trigger
+    "trigger-schedule",  # Scheduled trigger
+    "trigger-webhook",  # Webhook trigger
+    # Other internal nodes
+    "datasource",  # Data source configuration
+    "human-input",  # Human-in-the-loop node
+    "knowledge-index",  # Knowledge indexing node
+}
+
+
+def validate_node_schemas() -> list[str]:
+    """
+    Validate that all registered node types have corresponding schemas.
+
+    This function checks if BUILTIN_NODE_SCHEMAS covers all node types
+    registered in NODE_TYPE_CLASSES_MAPPING, excluding internal node types.
+
+    Returns:
+        List of warning messages for missing schemas (empty if all valid)
+    """
+    from core.workflow.nodes.node_mapping import NODE_TYPE_CLASSES_MAPPING
+
+    schemas = get_builtin_node_schemas()
+    warnings = []
+    for node_type in NODE_TYPE_CLASSES_MAPPING:
+        type_value = node_type.value
+        if type_value in _INTERNAL_NODE_TYPES:
+            continue
+        if type_value not in schemas:
+            warnings.append(f"Missing schema for node type: {type_value}")
+    return warnings

api/core/workflow/generator/config/responses.py

@@ -0,0 +1,74 @@
+"""
+Response Templates for Vibe Workflow Generation.
+
+This module defines templates for off-topic responses and default suggestions
+to guide users back to workflow-related requests.
+"""
+
+# Off-topic response templates for different categories
+# Each category has messages in multiple languages
+OFF_TOPIC_RESPONSES: dict[str, dict[str, str]] = {
+    "weather": {
+        "en": (
+            "I'm the workflow design assistant - I can't check the weather, "
+            "but I can help you build AI workflows! For example, I could help you "
+            "create a workflow that fetches weather data from an API."
+        ),
+        "zh": "我是工作流设计助手，无法查询天气。但我可以帮你创建一个从API获取天气数据的工作流！",
+    },
+    "math": {
+        "en": (
+            "I focus on workflow design rather than calculations. However, "
+            "if you need calculations in a workflow, I can help you add a Code node "
+            "that handles math operations!"
+        ),
+        "zh": "我专注于工作流设计而非计算。但如果您需要在工作流中进行计算，我可以帮您添加一个处理数学运算的代码节点！",
+    },
+    "joke": {
+        "en": (
+            "While I'd love to share a laugh, I'm specialized in workflow design. "
+            "How about we create something fun instead - like a workflow that generates jokes using AI?"
+        ),
+        "zh": "虽然我很想讲笑话，但我专门从事工作流设计。不如我们创建一个有趣的东西——比如使用AI生成笑话的工作流？",
+    },
+    "translation": {
+        "en": (
+            "I can't translate directly, but I can help you build a translation workflow! "
+            "Would you like to create one using an LLM node?"
+        ),
+        "zh": "我不能直接翻译，但我可以帮你构建一个翻译工作流！要创建一个使用LLM节点的翻译流程吗？",
+    },
+    "general_coding": {
+        "en": (
+            "I'm specialized in Dify workflow design rather than general coding help. "
+            "But if you want to add code logic to your workflow, I can help you configure a Code node!"
+        ),
+        "zh": (
+            "我专注于Dify工作流设计，而非通用编程帮助。"
+            "但如果您想在工作流中添加代码逻辑，我可以帮您配置一个代码节点！"
+        ),
+    },
+    "default": {
+        "en": (
+            "I'm the Dify workflow design assistant. I help create AI automation workflows, "
+            "but I can't help with general questions. Would you like to create a workflow instead?"
+        ),
+        "zh": "我是Dify工作流设计助手。我帮助创建AI自动化工作流，但无法回答一般性问题。您想创建一个工作流吗？",
+    },
+}
+
+# Default suggestions for off-topic requests
+# These help guide users towards valid workflow requests
+DEFAULT_SUGGESTIONS: dict[str, list[str]] = {
+    "en": [
+        "Create a chatbot workflow",
+        "Build a document summarization pipeline",
+        "Add email notification to workflow",
+    ],
+    "zh": [
+        "创建一个聊天机器人工作流",
+        "构建文档摘要处理流程",
+        "添加邮件通知到工作流",
+    ],
+}
+

api/core/workflow/generator/prompts/builder_prompts.py

@@ -0,0 +1,457 @@
+BUILDER_SYSTEM_PROMPT = """<role>
+You are a Workflow Configuration Engineer.
+Your goal is to implement the Architect's plan by generating a precise, runnable Dify Workflow JSON configuration.
+</role>
+
+<language_rules>
+- Detect the language of the user's request automatically (e.g., English, Chinese, Japanese, etc.).
+- Generate ALL node titles, descriptions, and user-facing text in the SAME language as the user's input.
+- If the input language is ambiguous or cannot be determined (e.g. code-only input),
+  use {preferred_language} as the target language.
+</language_rules>
+
+<inputs>
+<plan>
+{plan_context}
+</plan>
+
+<tool_schemas>
+{tool_schemas}
+</tool_schemas>
+
+<node_specs>
+{builtin_node_specs}
+</node_specs>
+
+<available_models>
+{available_models}
+</available_models>
+
+<workflow_context>
+  <existing_nodes>
+{existing_nodes_context}
+  </existing_nodes>
+  <existing_edges>
+{existing_edges_context}
+  </existing_edges>
+  <selected_nodes>
+{selected_nodes_context}
+  </selected_nodes>
+</workflow_context>
+</inputs>
+
+<rules>
+1. **Configuration**:
+   - You MUST fill ALL required parameters for every node.
+   - Use `{{{{#node_id.field#}}}}` syntax to reference outputs from previous nodes in text fields.
+   - For 'start' node, define all necessary user inputs.
+
+2. **Variable References**:
+   - For text fields (like prompts, queries): use string format `{{{{#node_id.field#}}}}`
+   - For 'end' node outputs: use `value_selector` array format `["node_id", "field"]`
+   - Example: to reference 'llm' node's 'text' output in end node, use `["llm", "text"]`
+
+3. **Tools**:
+   - ONLY use the tools listed in `<tool_schemas>`.
+   - If a planned tool is missing from schemas, fallback to `http-request` or `code`.
+
+4. **Model Selection** (CRITICAL):
+   - For LLM, question-classifier, and parameter-extractor nodes, you MUST include a "model" config.
+   - You MUST use ONLY models from the `<available_models>` section above.
+   - Copy the EXACT provider and name values from available_models.
+   - NEVER use openai/gpt-4o, gpt-3.5-turbo, gpt-4, or any other models unless they appear in available_models.
+   - If available_models is empty or shows "No models configured", omit the model config entirely.
+
+5. **Node Specifics**:
+   - For `if-else` comparison_operator, use literal symbols: `≥`, `≤`, `=`, `≠` (NOT `>=` or `==`).
+
+6. **Modification Mode**:
+   - If `<existing_nodes>` contains nodes, you are MODIFYING an existing workflow.
+   - Keep nodes that are NOT mentioned in the user's instruction UNCHANGED.
+   - Only modify/add/remove nodes that the user explicitly requested.
+   - Preserve node IDs for unchanged nodes to maintain connections.
+   - If user says "add X", append new nodes to existing workflow.
+   - If user says "change Y to Z", only modify that specific node.
+   - If user says "remove X", exclude that node from output.
+   
+   **Edge Modification**:
+   - Use `<existing_edges>` to understand current node connections.
+   - If user mentions "fix edge", "connect", "link", or "add connection",
+     review existing_edges and correct missing/wrong connections.
+   - For multi-branch nodes (if-else, question-classifier),
+     ensure EACH branch has proper sourceHandle (e.g., "true"/"false") and target.
+   - Common edge issues to fix:
+     * Missing edge: Two nodes should connect but don't - add the edge
+     * Wrong target: Edge points to wrong node - update the target
+     * Missing sourceHandle: if-else/classifier branches lack sourceHandle - add "true"/"false"
+     * Disconnected nodes: Node has no incoming or outgoing edges - connect it properly
+   - When modifying edges, ensure logical flow makes sense (start → middle → end).
+   - ALWAYS output complete edges array, even if only modifying one edge.
+   
+   **Validation Feedback** (Automatic Retry):
+   - If `<validation_feedback>` is present, you are RETRYING after validation errors.
+   - Focus ONLY on fixing the specific validation issues mentioned.
+   - Keep everything else from the previous attempt UNCHANGED (preserve node IDs, edges, etc).
+   - Common validation issues and fixes:
+     * "Missing required connection" → Add the missing edge
+     * "Invalid node configuration" → Fix the specific node's config section
+     * "Type mismatch in variable reference" → Correct the variable selector path
+     * "Unknown variable" → Update variable reference to existing output
+   - When fixing, make MINIMAL changes to address each specific error.
+
+7. **Output**:
+   - Return ONLY the JSON object with `nodes` and `edges`.
+   - Do NOT generate Mermaid diagrams.
+   - Do NOT generate explanations.
+</rules>
+
+<edge_rules priority="critical">
+**EDGES ARE CRITICAL** - Every node except 'end' MUST have at least one outgoing edge.
+
+1. **Linear Flow**: Simple source -> target connection
+   ```
+   {{"source": "node_a", "target": "node_b"}}
+   ```
+
+2. **question-classifier Branching**: Each class MUST have a separate edge with `sourceHandle` = class `id`
+   - If you define classes: [{{"id": "cls_refund", "name": "Refund"}}, {{"id": "cls_inquiry", "name": "Inquiry"}}]
+   - You MUST create edges:
+     - {{"source": "classifier", "sourceHandle": "cls_refund", "target": "refund_handler"}}
+     - {{"source": "classifier", "sourceHandle": "cls_inquiry", "target": "inquiry_handler"}}
+
+3. **if-else Branching**: MUST have exactly TWO edges with sourceHandle "true" and "false"
+   - {{"source": "condition", "sourceHandle": "true", "target": "true_branch"}}
+   - {{"source": "condition", "sourceHandle": "false", "target": "false_branch"}}
+
+4. **Branch Convergence**: Multiple branches can connect to same downstream node
+   - Both true_branch and false_branch can connect to the same 'end' node
+
+5. **NEVER leave orphan nodes**: Every node must be connected in the graph
+</edge_rules>
+
+<examples>
+<example name="simple_linear">
+```json
+{{
+  "nodes": [
+    {{
+      "id": "start",
+      "type": "start",
+      "title": "Start",
+      "config": {{
+        "variables": [{{"variable": "query", "label": "Query", "type": "text-input"}}]
+      }}
+    }},
+    {{
+      "id": "llm",
+      "type": "llm",
+      "title": "Generate Response",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "prompt_template": [{{"role": "user", "text": "Answer: {{{{#start.query#}}}}"}}]
+      }}
+    }},
+    {{
+      "id": "end",
+      "type": "end",
+      "title": "End",
+      "config": {{
+        "outputs": [
+          {{"variable": "result", "value_selector": ["llm", "text"]}}
+        ]
+      }}
+    }}
+  ],
+  "edges": [
+    {{"source": "start", "target": "llm"}},
+    {{"source": "llm", "target": "end"}}
+  ]
+}}
+```
+</example>
+
+<example name="question_classifier_branching" description="Customer service with intent classification">
+```json
+{{
+  "nodes": [
+    {{
+      "id": "start",
+      "type": "start",
+      "title": "Start",
+      "config": {{
+        "variables": [{{"variable": "user_input", "label": "User Message", "type": "text-input", "required": true}}]
+      }}
+    }},
+    {{
+      "id": "classifier",
+      "type": "question-classifier",
+      "title": "Classify Intent",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "query_variable_selector": ["start", "user_input"],
+        "classes": [
+          {{"id": "cls_refund", "name": "Refund Request"}},
+          {{"id": "cls_inquiry", "name": "Product Inquiry"}},
+          {{"id": "cls_complaint", "name": "Complaint"}},
+          {{"id": "cls_other", "name": "Other"}}
+        ],
+        "instruction": "Classify the user's intent"
+      }}
+    }},
+    {{
+      "id": "handle_refund",
+      "type": "llm",
+      "title": "Handle Refund",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "prompt_template": [{{"role": "user", "text": "Extract order number and respond: {{{{#start.user_input#}}}}"}}]
+      }}
+    }},
+    {{
+      "id": "handle_inquiry",
+      "type": "llm",
+      "title": "Handle Inquiry",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "prompt_template": [{{"role": "user", "text": "Answer product question: {{{{#start.user_input#}}}}"}}]
+      }}
+    }},
+    {{
+      "id": "handle_complaint",
+      "type": "llm",
+      "title": "Handle Complaint",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "prompt_template": [{{"role": "user", "text": "Respond with empathy: {{{{#start.user_input#}}}}"}}]
+      }}
+    }},
+    {{
+      "id": "handle_other",
+      "type": "llm",
+      "title": "Handle Other",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "prompt_template": [{{"role": "user", "text": "Provide general response: {{{{#start.user_input#}}}}"}}]
+      }}
+    }},
+    {{
+      "id": "end",
+      "type": "end",
+      "title": "End",
+      "config": {{
+        "outputs": [{{"variable": "response", "value_selector": ["handle_refund", "text"]}}]
+      }}
+    }}
+  ],
+  "edges": [
+    {{"source": "start", "target": "classifier"}},
+    {{"source": "classifier", "sourceHandle": "cls_refund", "target": "handle_refund"}},
+    {{"source": "classifier", "sourceHandle": "cls_inquiry", "target": "handle_inquiry"}},
+    {{"source": "classifier", "sourceHandle": "cls_complaint", "target": "handle_complaint"}},
+    {{"source": "classifier", "sourceHandle": "cls_other", "target": "handle_other"}},
+    {{"source": "handle_refund", "target": "end"}},
+    {{"source": "handle_inquiry", "target": "end"}},
+    {{"source": "handle_complaint", "target": "end"}},
+    {{"source": "handle_other", "target": "end"}}
+  ]
+}}
+```
+CRITICAL: Notice that each class id (cls_refund, cls_inquiry, etc.) becomes a sourceHandle in the edges!
+</example>
+
+<example name="if_else_branching" description="Conditional logic with if-else">
+```json
+{{
+  "nodes": [
+    {{
+      "id": "start",
+      "type": "start",
+      "title": "Start",
+      "config": {{
+        "variables": [{{"variable": "years", "label": "Years of Experience", "type": "number", "required": true}}]
+      }}
+    }},
+    {{
+      "id": "check_experience",
+      "type": "if-else",
+      "title": "Check Experience",
+      "config": {{
+        "cases": [
+          {{
+            "case_id": "case_1",
+            "logical_operator": "and",
+            "conditions": [
+              {{
+                "variable_selector": ["start", "years"],
+                "comparison_operator": "≥",
+                "value": "3"
+              }}
+            ]
+          }}
+        ]
+      }}
+    }},
+    {{
+      "id": "qualified",
+      "type": "llm",
+      "title": "Qualified Response",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "prompt_template": [{{"role": "user", "text": "Generate qualified candidate response"}}]
+      }}
+    }},
+    {{
+      "id": "not_qualified",
+      "type": "llm",
+      "title": "Not Qualified Response",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "prompt_template": [{{"role": "user", "text": "Generate rejection response"}}]
+      }}
+    }},
+    {{
+      "id": "end",
+      "type": "end",
+      "title": "End",
+      "config": {{
+        "outputs": [{{"variable": "result", "value_selector": ["qualified", "text"]}}]
+      }}
+    }}
+  ],
+  "edges": [
+    {{"source": "start", "target": "check_experience"}},
+    {{"source": "check_experience", "sourceHandle": "true", "target": "qualified"}},
+    {{"source": "check_experience", "sourceHandle": "false", "target": "not_qualified"}},
+    {{"source": "qualified", "target": "end"}},
+    {{"source": "not_qualified", "target": "end"}}
+  ]
+}}
+```
+CRITICAL: if-else MUST have exactly two edges with sourceHandle "true" and "false"!
+</example>
+
+<example name="parameter_extractor" description="Extract structured data from text">
+```json
+{{
+  "nodes": [
+    {{
+      "id": "start",
+      "type": "start",
+      "title": "Start",
+      "config": {{
+        "variables": [{{"variable": "resume", "label": "Resume Text", "type": "paragraph", "required": true}}]
+      }}
+    }},
+    {{
+      "id": "extract",
+      "type": "parameter-extractor",
+      "title": "Extract Info",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "query": ["start", "resume"],
+        "parameters": [
+          {{"name": "name", "type": "string", "description": "Candidate name", "required": true}},
+          {{"name": "years", "type": "number", "description": "Years of experience", "required": true}},
+          {{"name": "skills", "type": "array[string]", "description": "List of skills", "required": true}}
+        ],
+        "instruction": "Extract candidate information from resume"
+      }}
+    }},
+    {{
+      "id": "process",
+      "type": "llm",
+      "title": "Process Data",
+      "config": {{
+        "model": {{"provider": "openai", "name": "gpt-4o", "mode": "chat"}},
+        "prompt_template": [{{"role": "user", "text": "Name: {{{{#extract.name#}}}}, Years: {{{{#extract.years#}}}}"}}]
+      }}
+    }},
+    {{
+      "id": "end",
+      "type": "end",
+      "title": "End",
+      "config": {{
+        "outputs": [{{"variable": "result", "value_selector": ["process", "text"]}}]
+      }}
+    }}
+  ],
+  "edges": [
+    {{"source": "start", "target": "extract"}},
+    {{"source": "extract", "target": "process"}},
+    {{"source": "process", "target": "end"}}
+  ]
+}}
+```
+</example>
+</examples>
+
+<edge_checklist>
+Before finalizing, verify:
+1. [ ] Every node (except 'end') has at least one outgoing edge
+2. [ ] 'start' node has exactly one outgoing edge
+3. [ ] 'question-classifier' has one edge per class, each with sourceHandle = class id
+4. [ ] 'if-else' has exactly two edges: sourceHandle "true" and sourceHandle "false"
+5. [ ] All branches eventually connect to 'end' (directly or through other nodes)
+6. [ ] No orphan nodes exist (every node is reachable from 'start')
+</edge_checklist>
+"""
+
+BUILDER_USER_PROMPT = """<instruction>
+{instruction}
+</instruction>
+
+Generate the full workflow configuration now. Pay special attention to:
+1. Creating edges for ALL branches of question-classifier and if-else nodes
+2. Using correct sourceHandle values for branching nodes
+3. Ensuring every node is connected in the graph
+"""
+
+
+def format_existing_nodes(nodes: list[dict] | None) -> str:
+    """Format existing workflow nodes for context."""
+    if not nodes:
+        return "No existing nodes in workflow (creating from scratch)."
+
+    lines = []
+    for node in nodes:
+        node_id = node.get("id", "unknown")
+        node_type = node.get("type", "unknown")
+        title = node.get("title", "Untitled")
+        lines.append(f"- [{node_id}] {title} ({node_type})")
+    return "\n".join(lines)
+
+
+def format_selected_nodes(
+    selected_ids: list[str] | None,
+    existing_nodes: list[dict] | None,
+) -> str:
+    """Format selected nodes for modification context."""
+    if not selected_ids:
+        return "No nodes selected (generating new workflow)."
+
+    node_map = {n.get("id"): n for n in (existing_nodes or [])}
+    lines = []
+    for node_id in selected_ids:
+        if node_id in node_map:
+            node = node_map[node_id]
+            lines.append(f"- [{node_id}] {node.get('title', 'Untitled')} ({node.get('type', 'unknown')})")
+        else:
+            lines.append(f"- [{node_id}] (not found in current workflow)")
+    return "\n".join(lines)
+
+
+def format_existing_edges(edges: list[dict] | None) -> str:
+    """Format existing workflow edges to show connections."""
+    if not edges:
+        return "No existing edges (creating new workflow)."
+
+    lines = []
+    for edge in edges:
+        source = edge.get("source", "unknown")
+        target = edge.get("target", "unknown")
+        source_handle = edge.get("sourceHandle", "")
+        if source_handle:
+            lines.append(f"- {source} ({source_handle}) -> {target}")
+        else:
+            lines.append(f"- {source} -> {target}")
+    return "\n".join(lines)

api/core/workflow/generator/prompts/planner_prompts.py

@@ -0,0 +1,75 @@
+PLANNER_SYSTEM_PROMPT = """<role>
+You are an expert Workflow Architect.
+Your job is to analyze user requests and plan a high-level automation workflow.
+</role>
+
+<task>
+1. **Classify Intent**:
+   - Is the user asking to create an automation/workflow? -> Intent: "generate"
+   - Is it general chat/weather/jokes? -> Intent: "off_topic"
+
+2. **Plan Steps** (if intent is "generate"):
+   - Break down the user's goal into logical steps.
+   - For each step, identify if a specific capability/tool is needed.
+   - Select the MOST RELEVANT tools from the available_tools list.
+   - DO NOT configure parameters yet. Just identify the tool.
+
+3. **Output Format**:
+   Return a JSON object.
+</task>
+
+<available_tools>
+{tools_summary}
+</available_tools>
+
+<response_format>
+If intent is "generate":
+```json
+{{
+  "intent": "generate",
+  "plan_thought": "Brief explanation of the plan...",
+  "steps": [
+    {{ "step": 1, "description": "Fetch data from URL", "tool": "http-request" }},
+    {{ "step": 2, "description": "Summarize content", "tool": "llm" }},
+    {{ "step": 3, "description": "Search for info", "tool": "google_search" }}
+  ],
+  "required_tool_keys": ["google_search"] 
+}}
+```
+(Note: 'http-request', 'llm', 'code' are built-in, you don't need to list them in required_tool_keys,
+only external tools)
+
+If intent is "off_topic":
+```json
+{{
+  "intent": "off_topic",
+  "message": "I can only help you build workflows. Try asking me to 'Create a workflow that...'",
+  "suggestions": ["Scrape a website", "Summarize a PDF"]
+}}
+```
+</response_format>
+"""
+
+PLANNER_USER_PROMPT = """<user_request>
+{instruction}
+</user_request>
+"""
+
+
+def format_tools_for_planner(tools: list[dict]) -> str:
+    """Format tools list for planner (Lightweight: Name + Description only)."""
+    if not tools:
+        return "No external tools available."
+
+    lines = []
+    for t in tools:
+        key = t.get("tool_key") or t.get("tool_name")
+        provider = t.get("provider_id") or t.get("provider", "")
+        desc = t.get("tool_description") or t.get("description", "")
+        label = t.get("tool_label") or key
+
+        # Format: - [provider/key] Label: Description
+        full_key = f"{provider}/{key}" if provider else key
+        lines.append(f"- [{full_key}] {label}: {desc}")
+
+    return "\n".join(lines)

api/core/workflow/generator/runner.py

@@ -0,0 +1,287 @@
+import json
+import logging
+import re
+from collections.abc import Sequence
+
+import json_repair
+
+from core.model_manager import ModelManager
+from core.model_runtime.entities.message_entities import SystemPromptMessage, UserPromptMessage
+from core.model_runtime.entities.model_entities import ModelType
+from core.workflow.generator.prompts.builder_prompts import (
+    BUILDER_SYSTEM_PROMPT,
+    BUILDER_USER_PROMPT,
+    format_existing_edges,
+    format_existing_nodes,
+    format_selected_nodes,
+)
+from core.workflow.generator.prompts.planner_prompts import (
+    PLANNER_SYSTEM_PROMPT,
+    PLANNER_USER_PROMPT,
+    format_tools_for_planner,
+)
+from core.workflow.generator.prompts.vibe_prompts import (
+    format_available_models,
+    format_available_nodes,
+    format_available_tools,
+    parse_vibe_response,
+)
+from core.workflow.generator.utils.mermaid_generator import generate_mermaid
+from core.workflow.generator.utils.workflow_validator import ValidationHint, WorkflowValidator
+
+logger = logging.getLogger(__name__)
+
+
+class WorkflowGenerator:
+    """
+    Refactored Vibe Workflow Generator (Planner-Builder Architecture).
+    Extracts Vibe logic from the monolithic LLMGenerator.
+    """
+
+    @classmethod
+    def generate_workflow_flowchart(
+        cls,
+        tenant_id: str,
+        instruction: str,
+        model_config: dict,
+        available_nodes: Sequence[dict[str, object]] | None = None,
+        existing_nodes: Sequence[dict[str, object]] | None = None,
+        existing_edges: Sequence[dict[str, object]] | None = None,
+        available_tools: Sequence[dict[str, object]] | None = None,
+        selected_node_ids: Sequence[str] | None = None,
+        previous_workflow: dict[str, object] | None = None,
+        regenerate_mode: bool = False,
+        preferred_language: str | None = None,
+        available_models: Sequence[dict[str, object]] | None = None,
+    ):
+        """
+        Generates a Dify Workflow Flowchart from natural language instruction.
+
+        Pipeline:
+        1. Planner: Analyze intent & select tools.
+        2. Context Filter: Filter relevant tools (reduce tokens).
+        3. Builder: Generate node configurations.
+        4. Repair: Fix common node/edge issues (NodeRepair, EdgeRepair).
+        5. Validator: Check for errors & generate friendly hints.
+        6. Renderer: Deterministic Mermaid generation.
+        """
+        model_manager = ModelManager()
+        model_instance = model_manager.get_model_instance(
+            tenant_id=tenant_id,
+            model_type=ModelType.LLM,
+            provider=model_config.get("provider", ""),
+            model=model_config.get("name", ""),
+        )
+        model_parameters = model_config.get("completion_params", {})
+        available_tools_list = list(available_tools) if available_tools else []
+
+        # Check if this is modification mode (user is refining existing workflow)
+        has_existing_nodes = existing_nodes and len(list(existing_nodes)) > 0
+
+        # --- STEP 1: PLANNER (Skip in modification mode) ---
+        if has_existing_nodes:
+            # In modification mode, skip Planner:
+            # - User intent is clear: modify the existing workflow
+            # - Tools are already in use (from existing nodes)
+            # - No need for intent classification or tool selection
+            plan_data = {"intent": "generate", "steps": [], "required_tool_keys": []}
+            filtered_tools = available_tools_list  # Use all available tools
+        else:
+            # In creation mode, run Planner to validate intent and select tools
+            planner_tools_context = format_tools_for_planner(available_tools_list)
+            planner_system = PLANNER_SYSTEM_PROMPT.format(tools_summary=planner_tools_context)
+            planner_user = PLANNER_USER_PROMPT.format(instruction=instruction)
+
+            try:
+                response = model_instance.invoke_llm(
+                    prompt_messages=[
+                        SystemPromptMessage(content=planner_system),
+                        UserPromptMessage(content=planner_user),
+                    ],
+                    model_parameters=model_parameters,
+                    stream=False,
+                )
+                plan_content = response.message.content
+                # Reuse parse_vibe_response logic or simple load
+                plan_data = parse_vibe_response(plan_content)
+            except Exception as e:
+                logger.exception("Planner failed")
+                return {"intent": "error", "error": f"Planning failed: {str(e)}"}
+
+            if plan_data.get("intent") == "off_topic":
+                return {
+                    "intent": "off_topic",
+                    "message": plan_data.get("message", "I can only help with workflow creation."),
+                    "suggestions": plan_data.get("suggestions", []),
+                }
+
+            # --- STEP 2: CONTEXT FILTERING ---
+            required_tools = plan_data.get("required_tool_keys", [])
+
+            filtered_tools = []
+            if required_tools:
+                # Simple linear search (optimized version would use a map)
+                for tool in available_tools_list:
+                    t_key = tool.get("tool_key") or tool.get("tool_name")
+                    provider = tool.get("provider_id") or tool.get("provider")
+                    full_key = f"{provider}/{t_key}" if provider else t_key
+
+                    # Check if this tool is in required list (match either full key or short name)
+                    if t_key in required_tools or full_key in required_tools:
+                        filtered_tools.append(tool)
+            else:
+                # If logic only, no tools needed
+                filtered_tools = []
+
+        # --- STEP 3: BUILDER (with retry loop) ---
+        MAX_GLOBAL_RETRIES = 2  # Total attempts: 1 initial + 1 retry
+
+        workflow_data = None
+        mermaid_code = None
+        all_warnings = []
+        all_fixes = []
+        retry_count = 0
+        validation_hints = []
+
+        for attempt in range(MAX_GLOBAL_RETRIES):
+            retry_count = attempt
+            logger.info("Generation attempt %s/%s", attempt + 1, MAX_GLOBAL_RETRIES)
+
+            # Prepare context
+            tool_schemas = format_available_tools(filtered_tools)
+            node_specs = format_available_nodes(list(available_nodes) if available_nodes else [])
+            existing_nodes_context = format_existing_nodes(list(existing_nodes) if existing_nodes else None)
+            existing_edges_context = format_existing_edges(list(existing_edges) if existing_edges else None)
+            selected_nodes_context = format_selected_nodes(
+                list(selected_node_ids) if selected_node_ids else None, list(existing_nodes) if existing_nodes else None
+            )
+
+            # Build retry context
+            retry_context = ""
+
+            # NOTE: Manual regeneration/refinement mode removed
+            # Only handle automatic retry (validation errors)
+
+            # For automatic retry (validation errors)
+            if attempt > 0 and validation_hints:
+                severe_issues = [h for h in validation_hints if h.severity == "error"]
+                if severe_issues:
+                    retry_context = "\n<validation_feedback>\n"
+                    retry_context += "The previous generation had validation errors:\n"
+                    for idx, hint in enumerate(severe_issues[:5], 1):
+                        retry_context += f"{idx}. {hint.message}\n"
+                    retry_context += "\nPlease fix these specific issues while keeping everything else UNCHANGED.\n"
+                    retry_context += "</validation_feedback>\n"
+
+            builder_system = BUILDER_SYSTEM_PROMPT.format(
+                plan_context=json.dumps(plan_data.get("steps", []), indent=2),
+                tool_schemas=tool_schemas,
+                builtin_node_specs=node_specs,
+                available_models=format_available_models(list(available_models or [])),
+                preferred_language=preferred_language or "English",
+                existing_nodes_context=existing_nodes_context,
+                existing_edges_context=existing_edges_context,
+                selected_nodes_context=selected_nodes_context,
+            )
+            builder_user = BUILDER_USER_PROMPT.format(instruction=instruction) + retry_context
+
+            try:
+                build_res = model_instance.invoke_llm(
+                    prompt_messages=[
+                        SystemPromptMessage(content=builder_system),
+                        UserPromptMessage(content=builder_user),
+                    ],
+                    model_parameters=model_parameters,
+                    stream=False,
+                )
+                # Builder output is raw JSON nodes/edges
+                build_content = build_res.message.content
+                match = re.search(r"```(?:json)?\s*([\s\S]+?)```", build_content)
+                if match:
+                    build_content = match.group(1)
+
+                workflow_data = json_repair.loads(build_content)
+
+                if "nodes" not in workflow_data:
+                    workflow_data["nodes"] = []
+                if "edges" not in workflow_data:
+                    workflow_data["edges"] = []
+
+            except Exception as e:
+                logger.exception("Builder failed on attempt %d", attempt + 1)
+                if attempt == MAX_GLOBAL_RETRIES - 1:
+                    return {"intent": "error", "error": f"Building failed: {str(e)}"}
+                continue  # Try again
+
+            # NOTE: NodeRepair and EdgeRepair have been removed.
+            # Validation will detect structural issues, and LLM will fix them on retry.
+            # This is more accurate because LLM understands the workflow context.
+
+            # --- STEP 4: RENDERER (Generate Mermaid early for validation) ---
+            mermaid_code = generate_mermaid(workflow_data)
+
+            # --- STEP 5: VALIDATOR ---
+            is_valid, validation_hints = WorkflowValidator.validate(workflow_data, available_tools_list)
+
+            # --- STEP 6: GRAPH VALIDATION (structural checks using graph algorithms) ---
+            if attempt < MAX_GLOBAL_RETRIES - 1:
+                try:
+                    from core.workflow.generator.utils.graph_validator import GraphValidator
+
+                    graph_result = GraphValidator.validate(workflow_data)
+
+                    if not graph_result.success:
+                        # Convert graph errors to validation hints
+                        for graph_error in graph_result.errors:
+                            validation_hints.append(
+                                ValidationHint(
+                                    node_id=graph_error.node_id,
+                                    field="edges",
+                                    message=f"[Graph] {graph_error.message}",
+                                    severity="error",
+                                )
+                            )
+                        # Also add warnings (dead ends) as hints
+                        for graph_warning in graph_result.warnings:
+                            validation_hints.append(
+                                ValidationHint(
+                                    node_id=graph_warning.node_id,
+                                    field="edges",
+                                    message=f"[Graph] {graph_warning.message}",
+                                    severity="warning",
+                                )
+                            )
+                except Exception as e:
+                    logger.warning("Graph validation error: %s", e)
+            # Collect all validation warnings
+            all_warnings = [h.message for h in validation_hints]
+
+            # Check if we should retry
+            severe_issues = [h for h in validation_hints if h.severity == "error"]
+
+            if not severe_issues or attempt == MAX_GLOBAL_RETRIES - 1:
+                break
+
+            # Has severe errors and retries remaining - continue to next attempt
+
+        # Collect all validation warnings
+        all_warnings = [h.message for h in validation_hints]
+
+        # Add stability warning (as requested by user)
+        stability_warning = "The generated workflow may require debugging."
+        if preferred_language and preferred_language.startswith("zh"):
+            stability_warning = "生成的 Workflow 可能需要调试。"
+        all_warnings.append(stability_warning)
+
+        return {
+            "intent": "generate",
+            "flowchart": mermaid_code,
+            "nodes": workflow_data["nodes"],
+            "edges": workflow_data["edges"],
+            "message": plan_data.get("plan_thought", "Generated workflow based on your request."),
+            "warnings": all_warnings,
+            "tool_recommendations": [],  # Legacy field
+            "error": "",
+            "fixed_issues": all_fixes,  # Track what was auto-fixed
+            "retry_count": retry_count,  # Track how many retries were needed
+        }

api/core/workflow/generator/types.py

@@ -0,0 +1,217 @@
+"""
+Type definitions for Vibe Workflow Generator.
+
+This module provides:
+- TypedDict classes for lightweight type hints (no runtime overhead)
+- Pydantic models for runtime validation where needed
+
+Usage:
+    # For type hints only (no runtime validation):
+    from core.workflow.generator.types import WorkflowNodeDict, WorkflowEdgeDict
+
+    # For runtime validation:
+    from core.workflow.generator.types import WorkflowNode, WorkflowEdge
+"""
+
+from typing import Any, TypedDict
+
+from pydantic import BaseModel, Field
+
+# ============================================================
+# TypedDict definitions (lightweight, for type hints only)
+# ============================================================
+
+
+class WorkflowNodeDict(TypedDict, total=False):
+    """
+    Workflow node structure (TypedDict for hints).
+
+    Attributes:
+        id: Unique node identifier
+        type: Node type (e.g., "start", "end", "llm", "if-else", "http-request")
+        title: Human-readable node title
+        config: Node-specific configuration
+        data: Additional node data
+    """
+
+    id: str
+    type: str
+    title: str
+    config: dict[str, Any]
+    data: dict[str, Any]
+
+
+class WorkflowEdgeDict(TypedDict, total=False):
+    """
+    Workflow edge structure (TypedDict for hints).
+
+    Attributes:
+        source: Source node ID
+        target: Target node ID
+        sourceHandle: Branch handle for if-else/question-classifier nodes
+    """
+
+    source: str
+    target: str
+    sourceHandle: str
+
+
+class AvailableModelDict(TypedDict):
+    """
+    Available model structure.
+
+    Attributes:
+        provider: Model provider (e.g., "openai", "anthropic")
+        model: Model name (e.g., "gpt-4", "claude-3")
+    """
+
+    provider: str
+    model: str
+
+
+class ToolParameterDict(TypedDict, total=False):
+    """
+    Tool parameter structure.
+
+    Attributes:
+        name: Parameter name
+        type: Parameter type (e.g., "string", "number", "boolean")
+        required: Whether parameter is required
+        human_description: Human-readable description
+        llm_description: LLM-oriented description
+        options: Available options for enum-type parameters
+    """
+
+    name: str
+    type: str
+    required: bool
+    human_description: str | dict[str, str]
+    llm_description: str
+    options: list[Any]
+
+
+class AvailableToolDict(TypedDict, total=False):
+    """
+    Available tool structure.
+
+    Attributes:
+        provider_id: Tool provider ID
+        provider: Tool provider name (alternative to provider_id)
+        tool_key: Unique tool key
+        tool_name: Tool name (alternative to tool_key)
+        tool_description: Tool description
+        description: Alternative description field
+        is_team_authorization: Whether tool is configured/authorized
+        parameters: List of tool parameters
+    """
+
+    provider_id: str
+    provider: str
+    tool_key: str
+    tool_name: str
+    tool_description: str
+    description: str
+    is_team_authorization: bool
+    parameters: list[ToolParameterDict]
+
+
+class WorkflowDataDict(TypedDict, total=False):
+    """
+    Complete workflow data structure.
+
+    Attributes:
+        nodes: List of workflow nodes
+        edges: List of workflow edges
+        warnings: List of warning messages
+    """
+
+    nodes: list[WorkflowNodeDict]
+    edges: list[WorkflowEdgeDict]
+    warnings: list[str]
+
+
+# ============================================================
+# Pydantic models (for runtime validation)
+# ============================================================
+
+
+class WorkflowNode(BaseModel):
+    """
+    Workflow node with runtime validation.
+
+    Use this model when you need to validate node data at runtime.
+    For lightweight type hints without validation, use WorkflowNodeDict.
+    """
+
+    id: str
+    type: str
+    title: str = ""
+    config: dict[str, Any] = Field(default_factory=dict)
+    data: dict[str, Any] = Field(default_factory=dict)
+
+
+class WorkflowEdge(BaseModel):
+    """
+    Workflow edge with runtime validation.
+
+    Use this model when you need to validate edge data at runtime.
+    For lightweight type hints without validation, use WorkflowEdgeDict.
+    """
+
+    source: str
+    target: str
+    sourceHandle: str | None = None
+
+
+class AvailableModel(BaseModel):
+    """
+    Available model with runtime validation.
+
+    Use this model when you need to validate model data at runtime.
+    For lightweight type hints without validation, use AvailableModelDict.
+    """
+
+    provider: str
+    model: str
+
+
+class ToolParameter(BaseModel):
+    """Tool parameter with runtime validation."""
+
+    name: str = ""
+    type: str = "string"
+    required: bool = False
+    human_description: str | dict[str, str] = ""
+    llm_description: str = ""
+    options: list[Any] = Field(default_factory=list)
+
+
+class AvailableTool(BaseModel):
+    """
+    Available tool with runtime validation.
+
+    Use this model when you need to validate tool data at runtime.
+    For lightweight type hints without validation, use AvailableToolDict.
+    """
+
+    provider_id: str = ""
+    provider: str = ""
+    tool_key: str = ""
+    tool_name: str = ""
+    tool_description: str = ""
+    description: str = ""
+    is_team_authorization: bool = False
+    parameters: list[ToolParameter] = Field(default_factory=list)
+
+
+class WorkflowData(BaseModel):
+    """
+    Complete workflow data with runtime validation.
+
+    Use this model when you need to validate workflow data at runtime.
+    For lightweight type hints without validation, use WorkflowDataDict.
+    """
+
+    nodes: list[WorkflowNode] = Field(default_factory=list)
+    edges: list[WorkflowEdge] = Field(default_factory=list)
+    warnings: list[str] = Field(default_factory=list)

api/core/workflow/generator/utils/edge_repair.py

@@ -0,0 +1,384 @@
+"""
+Edge Repair Utility for Vibe Workflow Generation.
+
+This module provides intelligent edge repair capabilities for generated workflows.
+It can detect and fix common edge issues:
+- Missing edges between sequential nodes
+- Incomplete branches for question-classifier and if-else nodes
+- Orphaned nodes without connections
+
+The repair logic is deterministic and doesn't require LLM calls.
+"""
+
+import logging
+from dataclasses import dataclass, field
+
+from core.workflow.generator.types import WorkflowDataDict, WorkflowEdgeDict, WorkflowNodeDict
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class RepairResult:
+    """Result of edge repair operation."""
+
+    nodes: list[WorkflowNodeDict]
+    edges: list[WorkflowEdgeDict]
+    repairs_made: list[str] = field(default_factory=list)
+    warnings: list[str] = field(default_factory=list)
+
+    @property
+    def was_repaired(self) -> bool:
+        """Check if any repairs were made."""
+        return len(self.repairs_made) > 0
+
+
+class EdgeRepair:
+    """
+    Intelligent edge repair for workflow graphs.
+
+    Repairs are applied in order:
+    1. Infer linear connections from node order (if no edges exist)
+    2. Add missing branch edges for question-classifier
+    3. Add missing branch edges for if-else
+    4. Connect orphaned nodes
+    """
+
+    @classmethod
+    def repair(cls, workflow_data: WorkflowDataDict) -> RepairResult:
+        """
+        Repair edges in the workflow data.
+
+        Args:
+            workflow_data: Dict containing 'nodes' and 'edges'
+
+        Returns:
+            RepairResult with repaired nodes, edges, and repair logs
+        """
+        nodes = list(workflow_data.get("nodes", []))
+        edges = list(workflow_data.get("edges", []))
+        repairs: list[str] = []
+        warnings: list[str] = []
+
+        logger.info("[EDGE REPAIR] Starting repair process for %s nodes, %s edges", len(nodes), len(edges))
+
+        # Build node lookup
+
+        # Build node lookup
+        node_map = {n.get("id"): n for n in nodes if n.get("id")}
+        node_ids = set(node_map.keys())
+
+        # 1. If no edges at all, infer linear chain
+        if not edges and len(nodes) > 1:
+            edges, inferred_repairs = cls._infer_linear_chain(nodes)
+            repairs.extend(inferred_repairs)
+
+        # 2. Build edge index for analysis
+        outgoing_edges: dict[str, list[WorkflowEdgeDict]] = {}
+        incoming_edges: dict[str, list[WorkflowEdgeDict]] = {}
+        for edge in edges:
+            src = edge.get("source")
+            tgt = edge.get("target")
+            if src:
+                outgoing_edges.setdefault(src, []).append(edge)
+            if tgt:
+                incoming_edges.setdefault(tgt, []).append(edge)
+
+        # 3. Repair question-classifier branches
+        for node in nodes:
+            if node.get("type") == "question-classifier":
+                new_edges, branch_repairs, branch_warnings = cls._repair_classifier_branches(
+                    node, edges, outgoing_edges, node_ids
+                )
+                edges.extend(new_edges)
+                repairs.extend(branch_repairs)
+                warnings.extend(branch_warnings)
+                # Update outgoing index
+                for edge in new_edges:
+                    outgoing_edges.setdefault(edge.get("source"), []).append(edge)
+
+        # 4. Repair if-else branches
+        for node in nodes:
+            if node.get("type") == "if-else":
+                new_edges, branch_repairs, branch_warnings = cls._repair_if_else_branches(
+                    node, edges, outgoing_edges, node_ids
+                )
+                edges.extend(new_edges)
+                repairs.extend(branch_repairs)
+                warnings.extend(branch_warnings)
+                # Update outgoing index
+                for edge in new_edges:
+                    outgoing_edges.setdefault(edge.get("source"), []).append(edge)
+
+        # 5. Connect orphaned nodes (nodes with no incoming edge, except start)
+        new_edges, orphan_repairs = cls._connect_orphaned_nodes(nodes, edges, outgoing_edges, incoming_edges)
+        edges.extend(new_edges)
+        repairs.extend(orphan_repairs)
+
+        # 6. Connect nodes with no outgoing edge to 'end' (except end nodes)
+        new_edges, terminal_repairs = cls._connect_terminal_nodes(nodes, edges, outgoing_edges)
+        edges.extend(new_edges)
+        repairs.extend(terminal_repairs)
+
+        if repairs:
+            logger.info("[EDGE REPAIR] Completed with %s repairs:", len(repairs))
+            for i, repair in enumerate(repairs, 1):
+                logger.info("[EDGE REPAIR]   %s. %s", i, repair)
+        else:
+            logger.info("[EDGE REPAIR] Completed - no repairs needed")
+
+        return RepairResult(
+            nodes=nodes,
+            edges=edges,
+            repairs_made=repairs,
+            warnings=warnings,
+        )
+
+    @classmethod
+    def _infer_linear_chain(cls, nodes: list[WorkflowNodeDict]) -> tuple[list[WorkflowEdgeDict], list[str]]:
+        """
+        Infer a linear chain of edges from node order.
+
+        This is used when no edges are provided at all.
+        """
+        edges: list[WorkflowEdgeDict] = []
+        repairs: list[str] = []
+
+        # Filter to get ordered node IDs
+        node_ids = [n.get("id") for n in nodes if n.get("id")]
+
+        if len(node_ids) < 2:
+            return edges, repairs
+
+        # Create edges between consecutive nodes
+        for i in range(len(node_ids) - 1):
+            src = node_ids[i]
+            tgt = node_ids[i + 1]
+            edges.append({"source": src, "target": tgt})
+            repairs.append(f"Inferred edge: {src} -> {tgt}")
+
+        return edges, repairs
+
+    @classmethod
+    def _repair_classifier_branches(
+        cls,
+        node: WorkflowNodeDict,
+        edges: list[WorkflowEdgeDict],
+        outgoing_edges: dict[str, list[WorkflowEdgeDict]],
+        valid_node_ids: set[str],
+    ) -> tuple[list[WorkflowEdgeDict], list[str], list[str]]:
+        """
+        Repair missing branches for question-classifier nodes.
+
+        For each class that doesn't have an edge, create one pointing to 'end'.
+        """
+        new_edges: list[WorkflowEdgeDict] = []
+        repairs: list[str] = []
+        warnings: list[str] = []
+
+        node_id = node.get("id")
+        if not node_id:
+            return new_edges, repairs, warnings
+
+        config = node.get("config", {})
+        classes = config.get("classes", [])
+
+        if not classes:
+            return new_edges, repairs, warnings
+
+        # Get existing sourceHandles for this node
+        existing_handles = set()
+        for edge in outgoing_edges.get(node_id, []):
+            handle = edge.get("sourceHandle")
+            if handle:
+                existing_handles.add(handle)
+
+        # Find 'end' node as default target
+        end_node_id = "end"
+        if "end" not in valid_node_ids:
+            # Try to find an end node
+            for nid in valid_node_ids:
+                if "end" in nid.lower():
+                    end_node_id = nid
+                    break
+
+        # Add missing branches
+        for cls_def in classes:
+            if not isinstance(cls_def, dict):
+                continue
+            cls_id = cls_def.get("id")
+            cls_name = cls_def.get("name", cls_id)
+
+            if cls_id and cls_id not in existing_handles:
+                new_edge = {
+                    "source": node_id,
+                    "sourceHandle": cls_id,
+                    "target": end_node_id,
+                }
+                new_edges.append(new_edge)
+                repairs.append(f"Added missing branch edge for class '{cls_name}' -> {end_node_id}")
+                warnings.append(
+                    f"Auto-connected question-classifier branch '{cls_name}' to '{end_node_id}'. "
+                    "You may want to redirect this to a specific handler node."
+                )
+
+        return new_edges, repairs, warnings
+
+    @classmethod
+    def _repair_if_else_branches(
+        cls,
+        node: WorkflowNodeDict,
+        edges: list[WorkflowEdgeDict],
+        outgoing_edges: dict[str, list[WorkflowEdgeDict]],
+        valid_node_ids: set[str],
+    ) -> tuple[list[WorkflowEdgeDict], list[str], list[str]]:
+        """
+        Repair missing branches for if-else nodes.
+
+        If-else in Dify uses case_id as sourceHandle for each condition,
+        plus 'false' for the else branch.
+        """
+        new_edges: list[WorkflowEdgeDict] = []
+        repairs: list[str] = []
+        warnings: list[str] = []
+
+        node_id = node.get("id")
+        if not node_id:
+            return new_edges, repairs, warnings
+
+        # Get existing sourceHandles
+        existing_handles = set()
+        for edge in outgoing_edges.get(node_id, []):
+            handle = edge.get("sourceHandle")
+            if handle:
+                existing_handles.add(handle)
+
+        # Find 'end' node as default target
+        end_node_id = "end"
+        if "end" not in valid_node_ids:
+            for nid in valid_node_ids:
+                if "end" in nid.lower():
+                    end_node_id = nid
+                    break
+
+        # Get required branches from config
+        config = node.get("config", {})
+        cases = config.get("cases", [])
+
+        # Build required handles: each case_id + 'false' for else
+        required_branches = set()
+        for case in cases:
+            case_id = case.get("case_id")
+            if case_id:
+                required_branches.add(case_id)
+        required_branches.add("false")  # else branch
+
+        # Add missing branches
+        for branch in required_branches:
+            if branch not in existing_handles:
+                new_edge = {
+                    "source": node_id,
+                    "sourceHandle": branch,
+                    "target": end_node_id,
+                }
+                new_edges.append(new_edge)
+                repairs.append(f"Added missing if-else branch '{branch}' -> {end_node_id}")
+                warnings.append(
+                    f"Auto-connected if-else branch '{branch}' to '{end_node_id}'. "
+                    "You may want to redirect this to a specific handler node."
+                )
+
+        return new_edges, repairs, warnings
+
+    @classmethod
+    def _connect_orphaned_nodes(
+        cls,
+        nodes: list[WorkflowNodeDict],
+        edges: list[WorkflowEdgeDict],
+        outgoing_edges: dict[str, list[WorkflowEdgeDict]],
+        incoming_edges: dict[str, list[WorkflowEdgeDict]],
+    ) -> tuple[list[WorkflowEdgeDict], list[str]]:
+        """
+        Connect orphaned nodes to the previous node in sequence.
+
+        An orphaned node has no incoming edges and is not a 'start' node.
+        """
+        new_edges: list[WorkflowEdgeDict] = []
+        repairs: list[str] = []
+
+        node_ids = [n.get("id") for n in nodes if n.get("id")]
+        node_types = {n.get("id"): n.get("type") for n in nodes}
+
+        for i, node_id in enumerate(node_ids):
+            node_type = node_types.get(node_id)
+
+            # Skip start nodes - they don't need incoming edges
+            if node_type == "start":
+                continue
+
+            # Check if node has incoming edges
+            if node_id not in incoming_edges or not incoming_edges[node_id]:
+                # Find previous node to connect from
+                if i > 0:
+                    prev_node_id = node_ids[i - 1]
+                    new_edge = {"source": prev_node_id, "target": node_id}
+                    new_edges.append(new_edge)
+                    repairs.append(f"Connected orphaned node: {prev_node_id} -> {node_id}")
+
+                    # Update incoming_edges for subsequent checks
+                    incoming_edges.setdefault(node_id, []).append(new_edge)
+
+        return new_edges, repairs
+
+    @classmethod
+    def _connect_terminal_nodes(
+        cls,
+        nodes: list[WorkflowNodeDict],
+        edges: list[WorkflowEdgeDict],
+        outgoing_edges: dict[str, list[WorkflowEdgeDict]],
+    ) -> tuple[list[WorkflowEdgeDict], list[str]]:
+        """
+        Connect terminal nodes (no outgoing edges) to 'end'.
+
+        A terminal node has no outgoing edges and is not an 'end' node.
+        This ensures all branches eventually reach 'end'.
+        """
+        new_edges: list[WorkflowEdgeDict] = []
+        repairs: list[str] = []
+
+        # Find end node
+        end_node_id = None
+        node_ids = set()
+        for n in nodes:
+            nid = n.get("id")
+            ntype = n.get("type")
+            if nid:
+                node_ids.add(nid)
+            if ntype == "end":
+                end_node_id = nid
+
+        if not end_node_id:
+            # No end node found, can't connect
+            return new_edges, repairs
+
+        for node in nodes:
+            node_id = node.get("id")
+            node_type = node.get("type")
+
+            # Skip end nodes
+            if node_type == "end":
+                continue
+
+            # Skip nodes that already have outgoing edges
+            if outgoing_edges.get(node_id):
+                continue
+
+            # Connect to end
+            new_edge = {"source": node_id, "target": end_node_id}
+            new_edges.append(new_edge)
+            repairs.append(f"Connected terminal node to end: {node_id} -> {end_node_id}")
+
+            # Update for subsequent checks
+            outgoing_edges.setdefault(node_id, []).append(new_edge)
+
+        return new_edges, repairs

api/core/workflow/generator/utils/graph_validator.py

@@ -0,0 +1,280 @@
+"""
+Graph Validator for Workflow Generation
+
+Validates workflow graph structure using graph algorithms:
+- Reachability from start node (BFS)
+- Reachability to end node (reverse BFS)
+- Branch edge validation for if-else and classifier nodes
+"""
+
+import time
+from collections import deque
+from dataclasses import dataclass, field
+
+
+@dataclass
+class GraphError:
+    """Represents a structural error in the workflow graph."""
+
+    node_id: str
+    node_type: str
+    error_type: str  # "unreachable", "dead_end", "cycle", "missing_start", "missing_end"
+    message: str
+
+
+@dataclass
+class GraphValidationResult:
+    """Result of graph validation."""
+
+    success: bool
+    errors: list[GraphError] = field(default_factory=list)
+    warnings: list[GraphError] = field(default_factory=list)
+    execution_time: float = 0.0
+    stats: dict = field(default_factory=dict)
+
+
+class GraphValidator:
+    """
+    Validates workflow graph structure using proper graph algorithms.
+
+    Performs:
+    1. Forward reachability analysis (BFS from start)
+    2. Backward reachability analysis (reverse BFS from end)
+    3. Branch edge validation for if-else and classifier nodes
+    """
+
+    @staticmethod
+    def _build_adjacency(
+        nodes: dict[str, dict], edges: list[dict]
+    ) -> tuple[dict[str, list[str]], dict[str, list[str]]]:
+        """Build forward and reverse adjacency lists from edges."""
+        outgoing: dict[str, list[str]] = {node_id: [] for node_id in nodes}
+        incoming: dict[str, list[str]] = {node_id: [] for node_id in nodes}
+
+        for edge in edges:
+            source = edge.get("source")
+            target = edge.get("target")
+            if source in outgoing and target in incoming:
+                outgoing[source].append(target)
+                incoming[target].append(source)
+
+        return outgoing, incoming
+
+    @staticmethod
+    def _bfs_reachable(start: str, adjacency: dict[str, list[str]]) -> set[str]:
+        """BFS to find all nodes reachable from start node."""
+        if start not in adjacency:
+            return set()
+
+        visited = set()
+        queue = deque([start])
+        visited.add(start)
+
+        while queue:
+            current = queue.popleft()
+            for neighbor in adjacency.get(current, []):
+                if neighbor not in visited:
+                    visited.add(neighbor)
+                    queue.append(neighbor)
+
+        return visited
+
+    @staticmethod
+    def validate(workflow_data: dict) -> GraphValidationResult:
+        """Validate workflow graph structure."""
+        start_time = time.time()
+        errors: list[GraphError] = []
+        warnings: list[GraphError] = []
+
+        nodes_list = workflow_data.get("nodes", [])
+        edges_list = workflow_data.get("edges", [])
+        nodes = {n["id"]: n for n in nodes_list if n.get("id")}
+
+        # Find start and end nodes
+        start_node_id = None
+        end_node_ids = []
+
+        for node_id, node in nodes.items():
+            node_type = node.get("type")
+            if node_type == "start":
+                start_node_id = node_id
+            elif node_type == "end":
+                end_node_ids.append(node_id)
+
+        # Check start node exists
+        if not start_node_id:
+            errors.append(
+                GraphError(
+                    node_id="workflow",
+                    node_type="workflow",
+                    error_type="missing_start",
+                    message="Workflow has no start node",
+                )
+            )
+
+        # Check end node exists
+        if not end_node_ids:
+            errors.append(
+                GraphError(
+                    node_id="workflow",
+                    node_type="workflow",
+                    error_type="missing_end",
+                    message="Workflow has no end node",
+                )
+            )
+
+        # If missing start or end, can't do reachability analysis
+        if not start_node_id or not end_node_ids:
+            execution_time = time.time() - start_time
+            return GraphValidationResult(
+                success=False,
+                errors=errors,
+                warnings=warnings,
+                execution_time=execution_time,
+                stats={"nodes": len(nodes), "edges": len(edges_list)},
+            )
+
+        # Build adjacency lists
+        outgoing, incoming = GraphValidator._build_adjacency(nodes, edges_list)
+
+        # --- FORWARD REACHABILITY: BFS from start ---
+        reachable_from_start = GraphValidator._bfs_reachable(start_node_id, outgoing)
+
+        # Find unreachable nodes
+        unreachable_nodes = set(nodes.keys()) - reachable_from_start
+        for node_id in unreachable_nodes:
+            node = nodes[node_id]
+            errors.append(
+                GraphError(
+                    node_id=node_id,
+                    node_type=node.get("type", "unknown"),
+                    error_type="unreachable",
+                    message=f"Node '{node_id}' is not reachable from start node",
+                )
+            )
+
+        # --- BACKWARD REACHABILITY: Reverse BFS from end nodes ---
+        can_reach_end: set[str] = set()
+        for end_id in end_node_ids:
+            can_reach_end.update(GraphValidator._bfs_reachable(end_id, incoming))
+
+        # Find dead-end nodes (can't reach any end node)
+        dead_end_nodes = set(nodes.keys()) - can_reach_end
+        for node_id in dead_end_nodes:
+            if node_id in unreachable_nodes:
+                continue
+            node = nodes[node_id]
+            warnings.append(
+                GraphError(
+                    node_id=node_id,
+                    node_type=node.get("type", "unknown"),
+                    error_type="dead_end",
+                    message=f"Node '{node_id}' cannot reach any end node (dead end)",
+                )
+            )
+
+        # --- Start node has outgoing edges? ---
+        if not outgoing.get(start_node_id):
+            errors.append(
+                GraphError(
+                    node_id=start_node_id,
+                    node_type="start",
+                    error_type="disconnected",
+                    message="Start node has no outgoing connections",
+                )
+            )
+
+        # --- End nodes have incoming edges? ---
+        for end_id in end_node_ids:
+            if not incoming.get(end_id):
+                errors.append(
+                    GraphError(
+                        node_id=end_id,
+                        node_type="end",
+                        error_type="disconnected",
+                        message="End node has no incoming connections",
+                    )
+                )
+
+        # --- BRANCH EDGE VALIDATION ---
+        edge_handles: dict[str, set[str]] = {}
+        for edge in edges_list:
+            source = edge.get("source")
+            handle = edge.get("sourceHandle", "")
+            if source:
+                if source not in edge_handles:
+                    edge_handles[source] = set()
+                edge_handles[source].add(handle)
+
+        # Check if-else and question-classifier nodes
+        for node_id, node in nodes.items():
+            node_type = node.get("type")
+
+            if node_type == "if-else":
+                handles = edge_handles.get(node_id, set())
+                config = node.get("config", {})
+                cases = config.get("cases", [])
+
+                required_handles = set()
+                for case in cases:
+                    case_id = case.get("case_id")
+                    if case_id:
+                        required_handles.add(case_id)
+                required_handles.add("false")
+
+                missing = required_handles - handles
+                for handle in missing:
+                    errors.append(
+                        GraphError(
+                            node_id=node_id,
+                            node_type=node_type,
+                            error_type="missing_branch",
+                            message=f"If-else node '{node_id}' missing edge for branch '{handle}'",
+                        )
+                    )
+
+            elif node_type == "question-classifier":
+                handles = edge_handles.get(node_id, set())
+                config = node.get("config", {})
+                classes = config.get("classes", [])
+
+                required_handles = set()
+                for cls in classes:
+                    if isinstance(cls, dict):
+                        cls_id = cls.get("id")
+                        if cls_id:
+                            required_handles.add(cls_id)
+
+                missing = required_handles - handles
+                for handle in missing:
+                    cls_name = handle
+                    for cls in classes:
+                        if isinstance(cls, dict) and cls.get("id") == handle:
+                            cls_name = cls.get("name", handle)
+                            break
+                    errors.append(
+                        GraphError(
+                            node_id=node_id,
+                            node_type=node_type,
+                            error_type="missing_branch",
+                            message=f"Classifier '{node_id}' missing edge for class '{cls_name}'",
+                        )
+                    )
+
+        execution_time = time.time() - start_time
+        success = len(errors) == 0
+
+        return GraphValidationResult(
+            success=success,
+            errors=errors,
+            warnings=warnings,
+            execution_time=execution_time,
+            stats={
+                "nodes": len(nodes),
+                "edges": len(edges_list),
+                "reachable_from_start": len(reachable_from_start),
+                "can_reach_end": len(can_reach_end),
+                "unreachable": len(unreachable_nodes),
+                "dead_ends": len(dead_end_nodes - unreachable_nodes),
+            },
+        )

api/core/workflow/generator/utils/mermaid_generator.py

@@ -0,0 +1,113 @@
+import logging
+
+from core.workflow.generator.types import WorkflowDataDict
+
+logger = logging.getLogger(__name__)
+
+
+def generate_mermaid(workflow_data: WorkflowDataDict) -> str:
+    """
+    Generate a Mermaid flowchart from workflow data consisting of nodes and edges.
+
+    Args:
+        workflow_data: Dict containing 'nodes' (list) and 'edges' (list)
+
+    Returns:
+        String containing the Mermaid flowchart syntax
+    """
+    nodes = workflow_data.get("nodes", [])
+    edges = workflow_data.get("edges", [])
+
+    lines = ["flowchart TD"]
+
+    # 1. Define Nodes
+    # Format: node_id["title<br/>type"] or similar
+    # We will use the Vibe Workflow standard format: id["type=TYPE|title=TITLE"]
+    # Or specifically for tool nodes: id["type=tool|title=TITLE|tool=TOOL_KEY"]
+
+    # Map of original IDs to safe Mermaid IDs
+    id_map = {}
+
+    def get_safe_id(original_id: str) -> str:
+        if original_id == "end":
+            return "end_node"
+        if original_id == "subgraph":
+            return "subgraph_node"
+        # Mermaid IDs should be alphanumeric.
+        # If the ID has special chars, we might need to escape or hash, but Vibe usually generates simple IDs.
+        # We'll trust standard IDs but handle the reserved keyword 'end'.
+        return original_id
+
+    for node in nodes:
+        node_id = node.get("id")
+        if not node_id:
+            continue
+
+        safe_id = get_safe_id(node_id)
+        id_map[node_id] = safe_id
+
+        node_type = node.get("type", "unknown")
+        title = node.get("title", "Untitled")
+
+        # Escape quotes in title
+        safe_title = title.replace('"', "'")
+
+        if node_type == "tool":
+            config = node.get("config", {})
+            # Try multiple fields for tool reference
+            tool_ref = (
+                config.get("tool_key")
+                or config.get("tool")
+                or config.get("tool_name")
+                or node.get("tool_name")
+                or "unknown"
+            )
+            node_def = f'{safe_id}["type={node_type}|title={safe_title}|tool={tool_ref}"]'
+        else:
+            node_def = f'{safe_id}["type={node_type}|title={safe_title}"]'
+
+        lines.append(f"  {node_def}")
+
+    # 2. Define Edges
+    # Format: source --> target
+
+    # Track defined nodes to avoid edge errors
+    defined_node_ids = {n.get("id") for n in nodes if n.get("id")}
+
+    for edge in edges:
+        source = edge.get("source")
+        target = edge.get("target")
+
+        # Skip invalid edges
+        if not source or not target:
+            continue
+
+        if source not in defined_node_ids or target not in defined_node_ids:
+            continue
+
+        safe_source = id_map.get(source, source)
+        safe_target = id_map.get(target, target)
+
+        # Handle conditional branches (true/false) if present
+        # In Dify workflow, sourceHandle is often used for this
+        source_handle = edge.get("sourceHandle")
+        label = ""
+
+        if source_handle == "true":
+            label = "|true|"
+        elif source_handle == "false":
+            label = "|false|"
+        elif source_handle and source_handle != "source":
+            # For question-classifier or other multi-path nodes
+            # Clean up handle for display if needed
+            safe_handle = str(source_handle).replace('"', "'")
+            label = f"|{safe_handle}|"
+
+        edge_line = f"  {safe_source} -->{label} {safe_target}"
+        lines.append(edge_line)
+
+    # Start/End nodes are implicitly handled if they are in the 'nodes' list
+    # If not, we might need to add them, but usually the Builder should produce them.
+
+    result = "\n".join(lines)
+    return result

api/core/workflow/generator/utils/node_repair.py

@@ -0,0 +1,304 @@
+"""
+Node Repair Utility for Vibe Workflow Generation.
+
+This module provides intelligent node configuration repair capabilities.
+It can detect and fix common node configuration issues:
+- Invalid comparison operators in if-else nodes (e.g. '>=' -> '≥')
+"""
+
+import copy
+import logging
+import uuid
+from dataclasses import dataclass, field
+
+from core.workflow.generator.types import WorkflowNodeDict
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class NodeRepairResult:
+    """Result of node repair operation."""
+
+    nodes: list[WorkflowNodeDict]
+    repairs_made: list[str] = field(default_factory=list)
+    warnings: list[str] = field(default_factory=list)
+
+    @property
+    def was_repaired(self) -> bool:
+        """Check if any repairs were made."""
+        return len(self.repairs_made) > 0
+
+
+class NodeRepair:
+    """
+    Intelligent node configuration repair.
+    """
+
+    OPERATOR_MAP = {
+        ">=": "≥",
+        "<=": "≤",
+        "!=": "≠",
+        "==": "=",
+    }
+
+    TYPE_MAPPING = {
+        "json": "object",
+        "dict": "object",
+        "dictionary": "object",
+        "float": "number",
+        "int": "number",
+        "integer": "number",
+        "double": "number",
+        "str": "string",
+        "text": "string",
+        "bool": "boolean",
+        "list": "array[object]",
+        "array": "array[object]",
+    }
+
+    _REPAIR_HANDLERS = {
+        "if-else": "_repair_if_else_operators",
+        "variable-aggregator": "_repair_variable_aggregator_variables",
+        "code": "_repair_code_node_config",
+    }
+
+    @classmethod
+    def repair(
+        cls,
+        nodes: list[WorkflowNodeDict],
+        llm_callback=None,
+    ) -> NodeRepairResult:
+        """
+        Repair node configurations.
+
+        Args:
+            nodes: List of node dictionaries
+            llm_callback: Optional callback(node, issue_desc) -> fixed_config_part
+
+        Returns:
+            NodeRepairResult with repaired nodes and logs
+        """
+        # Deep copy to avoid mutating original
+        nodes = copy.deepcopy(nodes)
+        repairs: list[str] = []
+        warnings: list[str] = []
+
+        logger.info("[NODE REPAIR] Starting repair process for %s nodes", len(nodes))
+
+        for node in nodes:
+            node_type = node.get("type")
+
+            # 1. Rule-based repairs
+            handler_name = cls._REPAIR_HANDLERS.get(node_type)
+            if handler_name:
+                handler = getattr(cls, handler_name)
+                # Check if handler accepts llm_callback (inspect signature or just pass generic kwargs?)
+                # Simplest for now: handlers signature: (node, repairs, llm_callback=None)
+                try:
+                    handler(node, repairs, llm_callback=llm_callback)
+                except TypeError:
+                    # Fallback for handlers that don't accept llm_callback yet
+                    handler(node, repairs)
+
+            # Add other node type repairs here as needed
+
+        if repairs:
+            logger.info("[NODE REPAIR] Completed with %s repairs:", len(repairs))
+            for i, repair in enumerate(repairs, 1):
+                logger.info("[NODE REPAIR]   %s. %s", i, repair)
+        else:
+            logger.info("[NODE REPAIR] Completed - no repairs needed")
+
+        return NodeRepairResult(
+            nodes=nodes,
+            repairs_made=repairs,
+            warnings=warnings,
+        )
+
+    @classmethod
+    def _repair_if_else_operators(cls, node: WorkflowNodeDict, repairs: list[str], **kwargs):
+        """
+        Normalize comparison operators in if-else nodes.
+        And ensure 'id' field exists for cases and conditions (frontend requirement).
+        """
+        node_id = node.get("id", "unknown")
+        config = node.get("config", {})
+        cases = config.get("cases", [])
+
+        for case in cases:
+            # Ensure case_id
+            if "case_id" not in case:
+                case["case_id"] = str(uuid.uuid4())
+                repairs.append(f"Generated missing case_id for case in node '{node_id}'")
+
+            conditions = case.get("conditions", [])
+            for condition in conditions:
+                # Ensure condition id
+                if "id" not in condition:
+                    condition["id"] = str(uuid.uuid4())
+                    # Not logging this repair to avoid clutter, as it's a structural fix
+
+                # Ensure value type (LLM might return int/float, but we need str/bool/list)
+                val = condition.get("value")
+                if isinstance(val, (int, float)) and not isinstance(val, bool):
+                    condition["value"] = str(val)
+                    repairs.append(f"Coerced numeric value to string in node '{node_id}'")
+
+                op = condition.get("comparison_operator")
+                if op in cls.OPERATOR_MAP:
+                    new_op = cls.OPERATOR_MAP[op]
+                    condition["comparison_operator"] = new_op
+                    repairs.append(f"Normalized operator '{op}' to '{new_op}' in node '{node_id}'")
+
+    @classmethod
+    def _repair_variable_aggregator_variables(cls, node: WorkflowNodeDict, repairs: list[str]):
+        """
+        Repair variable-aggregator variables format.
+        Converts dict format to list[list[str]] format.
+        Expected: [["node_id", "field"], ["node_id2", "field2"]]
+        May receive: [{"name": "...", "value_selector": ["node_id", "field"]}, ...]
+        """
+        node_id = node.get("id", "unknown")
+        config = node.get("config", {})
+        variables = config.get("variables", [])
+
+        if not variables:
+            return
+
+        repaired = False
+        repaired_variables = []
+
+        for var in variables:
+            if isinstance(var, dict):
+                # Convert dict format to array format
+                value_selector = var.get("value_selector") or var.get("selector") or var.get("path")
+                if isinstance(value_selector, list) and len(value_selector) > 0:
+                    repaired_variables.append(value_selector)
+                    repaired = True
+                else:
+                    # Try to extract from name field - LLM may generate {"name": "node_id.field"}
+                    name = var.get("name")
+                    if isinstance(name, str) and "." in name:
+                        # Try to parse "node_id.field" format
+                        parts = name.split(".", 1)
+                        if len(parts) == 2:
+                            repaired_variables.append([parts[0], parts[1]])
+                            repaired = True
+                        else:
+                            logger.warning(
+                                "Variable aggregator node '%s' has invalid variable format: %s",
+                                node_id,
+                                var,
+                            )
+                            repaired_variables.append([])  # Empty array as fallback
+                    else:
+                        # If no valid selector or name, skip this variable
+                        logger.warning(
+                            "Variable aggregator node '%s' has invalid variable format: %s",
+                            node_id,
+                            var,
+                        )
+                        # Don't add empty array - skip invalid variables
+            elif isinstance(var, list):
+                # Already in correct format
+                repaired_variables.append(var)
+            else:
+                # Unknown format, skip
+                logger.warning("Variable aggregator node '%s' has unknown variable format: %s", node_id, var)
+                # Don't add empty array - skip invalid variables
+
+        if repaired:
+            config["variables"] = repaired_variables
+            repairs.append(f"Repaired variable-aggregator variables format in node '{node_id}'")
+
+    @classmethod
+    def _repair_code_node_config(cls, node: WorkflowNodeDict, repairs: list[str], llm_callback=None):
+        """
+        Repair code node configuration (outputs and variables).
+        1. Outputs: Converts list format to dict format AND normalizes types.
+        2. Variables: Ensures value_selector exists.
+        """
+        node_id = node.get("id", "unknown")
+        config = node.get("config", {})
+
+        if "variables" not in config:
+            config["variables"] = []
+
+        # --- Repair Variables ---
+        variables = config.get("variables")
+        if isinstance(variables, list):
+            for var in variables:
+                if isinstance(var, dict):
+                    # Ensure value_selector exists (frontend crashes if missing)
+                    if "value_selector" not in var:
+                        var["value_selector"] = []
+                        # Not logging trivial repairs
+
+        # --- Repair Outputs ---
+        outputs = config.get("outputs")
+
+        if not outputs:
+            return
+
+        # Helper to normalize type
+        def normalize_type(t: str) -> str:
+            t_lower = str(t).lower()
+            return cls.TYPE_MAPPING.get(t_lower, t)
+
+        # 1. Handle Dict format (Standard) - Check for invalid types
+        if isinstance(outputs, dict):
+            changed = False
+            for var_name, var_config in outputs.items():
+                if isinstance(var_config, dict):
+                    original_type = var_config.get("type")
+                    if original_type:
+                        new_type = normalize_type(original_type)
+                        if new_type != original_type:
+                            var_config["type"] = new_type
+                            changed = True
+                            repairs.append(
+                                f"Normalized type '{original_type}' to '{new_type}' "
+                                f"for var '{var_name}' in node '{node_id}'"
+                            )
+            return
+
+        # 2. Handle List format (Repair needed)
+        if isinstance(outputs, list):
+            new_outputs = {}
+            for item in outputs:
+                if isinstance(item, dict):
+                    var_name = item.get("variable") or item.get("name")
+                    var_type = item.get("type")
+                    if var_name and var_type:
+                        norm_type = normalize_type(var_type)
+                        new_outputs[var_name] = {"type": norm_type}
+                        if norm_type != var_type:
+                            repairs.append(
+                                f"Normalized type '{var_type}' to '{norm_type}' "
+                                f"during list conversion in node '{node_id}'"
+                            )
+
+            if new_outputs:
+                config["outputs"] = new_outputs
+                repairs.append(f"Repaired code node outputs format in node '{node_id}'")
+            else:
+                # Fallback: Try LLM if available
+                if llm_callback:
+                    try:
+                        # Attempt to fix using LLM
+                        fixed_outputs = llm_callback(
+                            node,
+                            "outputs must be a dictionary like {'var_name': {'type': 'string'}}, "
+                            "but got a list or valid conversion failed.",
+                        )
+                        if isinstance(fixed_outputs, dict) and fixed_outputs:
+                            config["outputs"] = fixed_outputs
+                            repairs.append(f"Repaired code node outputs format using LLM in node '{node_id}'")
+                            return
+                    except Exception as e:
+                        logger.warning("LLM fallback repair failed for node '%s': %s", node_id, e)
+
+                # If conversion/LLM failed, set to empty dict
+                config["outputs"] = {}
+                repairs.append(f"Reset invalid code node outputs to empty dict in node '{node_id}'")

api/core/workflow/generator/utils/workflow_validator.py

@@ -0,0 +1,101 @@
+from dataclasses import dataclass
+
+from core.workflow.generator.types import AvailableModelDict, AvailableToolDict, WorkflowDataDict
+from core.workflow.generator.validation.context import ValidationContext
+from core.workflow.generator.validation.engine import ValidationEngine
+from core.workflow.generator.validation.rules import Severity
+
+
+@dataclass
+class ValidationHint:
+    """Legacy compatibility class for validation hints."""
+
+    node_id: str
+    field: str
+    message: str
+    severity: str  # 'error', 'warning'
+    suggestion: str = None
+    node_type: str = None  # Added for test compatibility
+
+    # Alias for potential old code using 'type' instead of 'severity'
+    @property
+    def type(self) -> str:
+        return self.severity
+
+    @property
+    def element_id(self) -> str:
+        return self.node_id
+
+
+FriendlyHint = ValidationHint  # Alias for backward compatibility
+
+
+class WorkflowValidator:
+    """
+    Validates the generated workflow configuration (nodes and edges).
+    Wraps the new ValidationEngine for backward compatibility.
+    """
+
+    @classmethod
+    def validate(
+        cls,
+        workflow_data: WorkflowDataDict,
+        available_tools: list[AvailableToolDict],
+        available_models: list[AvailableModelDict] | None = None,
+    ) -> tuple[bool, list[ValidationHint]]:
+        """
+        Validate workflow data and return validity status and hints.
+
+        Args:
+            workflow_data: Dict containing 'nodes' and 'edges'
+            available_tools: List of available tool configurations
+            available_models: List of available models (added for Vibe compat)
+
+        Returns:
+            Tuple(max_severity_is_not_error, list_of_hints)
+        """
+        nodes = workflow_data.get("nodes", [])
+        edges = workflow_data.get("edges", [])
+
+        # Create context
+        context = ValidationContext(
+            nodes=nodes,
+            edges=edges,
+            available_models=available_models or [],
+            available_tools=available_tools or [],
+        )
+
+        # Run validation engine
+        engine = ValidationEngine()
+        result = engine.validate(context)
+
+        # Convert engine errors to legacy hints
+        hints: list[ValidationHint] = []
+
+        error_count = 0
+        warning_count = 0
+
+        for error in result.all_errors:
+            # Map severity
+            severity = "error" if error.severity == Severity.ERROR else "warning"
+
+            if severity == "error":
+                error_count += 1
+            else:
+                warning_count += 1
+
+            # Map field from message or details if possible (heuristic)
+            field_name = error.details.get("field", "unknown")
+
+            hints.append(
+                ValidationHint(
+                    node_id=error.node_id,
+                    field=field_name,
+                    message=error.message,
+                    severity=severity,
+                    suggestion=error.fix_hint,
+                    node_type=error.node_type,
+                )
+            )
+
+        return result.is_valid, hints

api/core/workflow/generator/validation/__init__.py

@@ -0,0 +1,45 @@
+"""
+Validation Rule Engine for Vibe Workflow Generation.
+
+This module provides a declarative, schema-based validation system for
+generated workflow nodes. It classifies errors into fixable (LLM can auto-fix)
+and user-required (needs manual intervention) categories.
+
+Usage:
+    from core.workflow.generator.validation import ValidationEngine, ValidationContext
+
+    context = ValidationContext(
+        available_models=[...],
+        available_tools=[...],
+        nodes=[...],
+        edges=[...],
+    )
+    engine = ValidationEngine()
+    result = engine.validate(context)
+
+    # Access classified errors
+    fixable_errors = result.fixable_errors
+    user_required_errors = result.user_required_errors
+"""
+
+from core.workflow.generator.validation.context import ValidationContext
+from core.workflow.generator.validation.engine import ValidationEngine, ValidationResult
+from core.workflow.generator.validation.rules import (
+    RuleCategory,
+    Severity,
+    ValidationError,
+    ValidationRule,
+)
+
+__all__ = [
+    "RuleCategory",
+    "Severity",
+    "ValidationContext",
+    "ValidationEngine",
+    "ValidationError",
+    "ValidationResult",
+    "ValidationRule",
+]
+
+
+

api/core/workflow/generator/validation/context.py

@@ -0,0 +1,115 @@
+"""
+Validation Context for the Rule Engine.
+
+The ValidationContext holds all the data needed for validation:
+- Generated nodes and edges
+- Available models, tools, and datasets
+- Node output schemas for variable reference validation
+"""
+
+from dataclasses import dataclass, field
+
+from core.workflow.generator.types import (
+    AvailableModelDict,
+    AvailableToolDict,
+    WorkflowEdgeDict,
+    WorkflowNodeDict,
+)
+
+
+@dataclass
+class ValidationContext:
+    """
+    Context object containing all data needed for validation.
+
+    This is passed to each validation rule, providing access to:
+    - The nodes being validated
+    - Edge connections between nodes
+    - Available external resources (models, tools)
+    """
+
+    # Generated workflow data
+    nodes: list[WorkflowNodeDict] = field(default_factory=list)
+    edges: list[WorkflowEdgeDict] = field(default_factory=list)
+
+    # Available external resources
+    available_models: list[AvailableModelDict] = field(default_factory=list)
+    available_tools: list[AvailableToolDict] = field(default_factory=list)
+
+    # Cached lookups (populated lazily)
+    _node_map: dict[str, WorkflowNodeDict] | None = field(default=None, repr=False)
+    _model_set: set[tuple[str, str]] | None = field(default=None, repr=False)
+    _tool_set: set[str] | None = field(default=None, repr=False)
+    _configured_tool_set: set[str] | None = field(default=None, repr=False)
+
+    @property
+    def node_map(self) -> dict[str, WorkflowNodeDict]:
+        """Get a map of node_id -> node for quick lookup."""
+        if self._node_map is None:
+            self._node_map = {node.get("id", ""): node for node in self.nodes}
+        return self._node_map
+
+    @property
+    def model_set(self) -> set[tuple[str, str]]:
+        """Get a set of (provider, model_name) tuples for quick lookup."""
+        if self._model_set is None:
+            self._model_set = {(m.get("provider", ""), m.get("model", "")) for m in self.available_models}
+        return self._model_set
+
+    @property
+    def tool_set(self) -> set[str]:
+        """Get a set of all tool keys (both configured and unconfigured)."""
+        if self._tool_set is None:
+            self._tool_set = set()
+            for tool in self.available_tools:
+                provider = tool.get("provider_id") or tool.get("provider", "")
+                tool_key = tool.get("tool_key") or tool.get("tool_name", "")
+                if provider and tool_key:
+                    self._tool_set.add(f"{provider}/{tool_key}")
+                if tool_key:
+                    self._tool_set.add(tool_key)
+        return self._tool_set
+
+    @property
+    def configured_tool_set(self) -> set[str]:
+        """Get a set of configured (authorized) tool keys."""
+        if self._configured_tool_set is None:
+            self._configured_tool_set = set()
+            for tool in self.available_tools:
+                if not tool.get("is_team_authorization", False):
+                    continue
+                provider = tool.get("provider_id") or tool.get("provider", "")
+                tool_key = tool.get("tool_key") or tool.get("tool_name", "")
+                if provider and tool_key:
+                    self._configured_tool_set.add(f"{provider}/{tool_key}")
+                if tool_key:
+                    self._configured_tool_set.add(tool_key)
+        return self._configured_tool_set
+
+    def has_model(self, provider: str, model_name: str) -> bool:
+        """Check if a model is available."""
+        return (provider, model_name) in self.model_set
+
+    def has_tool(self, tool_key: str) -> bool:
+        """Check if a tool exists (configured or not)."""
+        return tool_key in self.tool_set
+
+    def is_tool_configured(self, tool_key: str) -> bool:
+        """Check if a tool is configured and ready to use."""
+        return tool_key in self.configured_tool_set
+
+    def get_node(self, node_id: str) -> WorkflowNodeDict | None:
+        """Get a node by its ID."""
+        return self.node_map.get(node_id)
+
+    def get_node_ids(self) -> set[str]:
+        """Get all node IDs in the workflow."""
+        return set(self.node_map.keys())
+
+    def get_upstream_nodes(self, node_id: str) -> list[str]:
+        """Get IDs of nodes that connect to this node (upstream)."""
+        return [edge.get("source", "") for edge in self.edges if edge.get("target") == node_id]
+
+    def get_downstream_nodes(self, node_id: str) -> list[str]:
+        """Get IDs of nodes that this node connects to (downstream)."""
+        return [edge.get("target", "") for edge in self.edges if edge.get("source") == node_id]

api/core/workflow/generator/validation/engine.py

@@ -0,0 +1,260 @@
+"""
+Validation Engine - Core validation logic.
+
+The ValidationEngine orchestrates rule execution and aggregates results.
+It provides a clean interface for validating workflow nodes.
+"""
+
+import logging
+from dataclasses import dataclass, field
+from typing import Any
+
+from core.workflow.generator.types import (
+    AvailableModelDict,
+    AvailableToolDict,
+    WorkflowEdgeDict,
+    WorkflowNodeDict,
+)
+from core.workflow.generator.validation.context import ValidationContext
+from core.workflow.generator.validation.rules import (
+    RuleCategory,
+    Severity,
+    ValidationError,
+    get_registry,
+)
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class ValidationResult:
+    """
+    Result of validation containing all errors classified by fixability.
+
+    Attributes:
+        all_errors: All validation errors found
+        fixable_errors: Errors that LLM can automatically fix
+        user_required_errors: Errors that require user intervention
+        warnings: Non-blocking warnings
+        stats: Validation statistics
+    """
+
+    all_errors: list[ValidationError] = field(default_factory=list)
+    fixable_errors: list[ValidationError] = field(default_factory=list)
+    user_required_errors: list[ValidationError] = field(default_factory=list)
+    warnings: list[ValidationError] = field(default_factory=list)
+    stats: dict[str, int] = field(default_factory=dict)
+
+    @property
+    def has_errors(self) -> bool:
+        """Check if there are any errors (excluding warnings)."""
+        return len(self.fixable_errors) > 0 or len(self.user_required_errors) > 0
+
+    @property
+    def has_fixable_errors(self) -> bool:
+        """Check if there are fixable errors."""
+        return len(self.fixable_errors) > 0
+
+    @property
+    def is_valid(self) -> bool:
+        """Check if validation passed (no errors, warnings are OK)."""
+        return not self.has_errors
+
+    def to_dict(self) -> dict[str, Any]:
+        """Convert to dictionary for API response."""
+        return {
+            "fixable": [e.to_dict() for e in self.fixable_errors],
+            "user_required": [e.to_dict() for e in self.user_required_errors],
+            "warnings": [e.to_dict() for e in self.warnings],
+            "all_warnings": [e.message for e in self.all_errors],
+            "stats": self.stats,
+        }
+
+    def get_error_messages(self) -> list[str]:
+        """Get all error messages as strings."""
+        return [e.message for e in self.all_errors]
+
+    def get_fixable_by_node(self) -> dict[str, list[ValidationError]]:
+        """Group fixable errors by node ID."""
+        result: dict[str, list[ValidationError]] = {}
+        for error in self.fixable_errors:
+            if error.node_id not in result:
+                result[error.node_id] = []
+            result[error.node_id].append(error)
+        return result
+
+
+class ValidationEngine:
+    """
+    The main validation engine.
+
+    Usage:
+        engine = ValidationEngine()
+        context = ValidationContext(nodes=[...], available_models=[...])
+        result = engine.validate(context)
+    """
+
+    def __init__(self):
+        self._registry = get_registry()
+
+    def validate(self, context: ValidationContext) -> ValidationResult:
+        """
+        Validate all nodes in the context.
+
+        Args:
+            context: ValidationContext with nodes, edges, and available resources
+
+        Returns:
+            ValidationResult with classified errors
+        """
+        result = ValidationResult()
+        stats = {
+            "total_nodes": len(context.nodes),
+            "total_rules_checked": 0,
+            "total_errors": 0,
+            "fixable_count": 0,
+            "user_required_count": 0,
+            "warning_count": 0,
+        }
+
+        # Validate each node
+        for node in context.nodes:
+            node_type = node.get("type", "unknown")
+            node_id = node.get("id", "unknown")
+
+            # Get applicable rules for this node type
+            rules = self._registry.get_rules_for_node(node_type)
+
+            for rule in rules:
+                stats["total_rules_checked"] += 1
+
+                try:
+                    errors = rule.check(node, context)
+                    for error in errors:
+                        result.all_errors.append(error)
+                        stats["total_errors"] += 1
+
+                        # Classify by severity and fixability
+                        if error.severity == Severity.WARNING:
+                            result.warnings.append(error)
+                            stats["warning_count"] += 1
+                        elif error.is_fixable:
+                            result.fixable_errors.append(error)
+                            stats["fixable_count"] += 1
+                        else:
+                            result.user_required_errors.append(error)
+                            stats["user_required_count"] += 1
+
+                except Exception:
+                    logger.exception(
+                        "Rule '%s' failed for node '%s'",
+                        rule.id,
+                        node_id,
+                    )
+                    # Don't let a rule failure break the entire validation
+                    continue
+
+        # Validate edges separately
+        edge_errors = self._validate_edges(context)
+        for error in edge_errors:
+            result.all_errors.append(error)
+            stats["total_errors"] += 1
+            if error.is_fixable:
+                result.fixable_errors.append(error)
+                stats["fixable_count"] += 1
+            else:
+                result.user_required_errors.append(error)
+                stats["user_required_count"] += 1
+
+        result.stats = stats
+
+        return result
+
+    def _validate_edges(self, context: ValidationContext) -> list[ValidationError]:
+        """Validate edge connections."""
+        errors: list[ValidationError] = []
+        valid_node_ids = context.get_node_ids()
+
+        for edge in context.edges:
+            source = edge.get("source", "")
+            target = edge.get("target", "")
+
+            if source and source not in valid_node_ids:
+                errors.append(
+                    ValidationError(
+                        rule_id="edge.source.invalid",
+                        node_id=source,
+                        node_type="edge",
+                        category=RuleCategory.SEMANTIC,
+                        severity=Severity.ERROR,
+                        is_fixable=True,
+                        message=f"Edge source '{source}' does not exist",
+                        fix_hint="Update edge to reference existing node",
+                    )
+                )
+
+            if target and target not in valid_node_ids:
+                errors.append(
+                    ValidationError(
+                        rule_id="edge.target.invalid",
+                        node_id=target,
+                        node_type="edge",
+                        category=RuleCategory.SEMANTIC,
+                        severity=Severity.ERROR,
+                        is_fixable=True,
+                        message=f"Edge target '{target}' does not exist",
+                        fix_hint="Update edge to reference existing node",
+                    )
+                )
+
+        return errors
+
+    def validate_single_node(
+        self,
+        node: WorkflowNodeDict,
+        context: ValidationContext,
+    ) -> list[ValidationError]:
+        """
+        Validate a single node.
+
+        Useful for incremental validation when a node is added/modified.
+        """
+        node_type = node.get("type", "unknown")
+        rules = self._registry.get_rules_for_node(node_type)
+
+        errors: list[ValidationError] = []
+        for rule in rules:
+            try:
+                errors.extend(rule.check(node, context))
+            except Exception:
+                logger.exception("Rule '%s' failed", rule.id)
+
+        return errors
+
+
+def validate_nodes(
+    nodes: list[WorkflowNodeDict],
+    edges: list[WorkflowEdgeDict] | None = None,
+    available_models: list[AvailableModelDict] | None = None,
+    available_tools: list[AvailableToolDict] | None = None,
+) -> ValidationResult:
+    """
+    Convenience function to validate nodes without creating engine/context manually.
+
+    Args:
+        nodes: List of workflow nodes to validate
+        edges: Optional list of edges
+        available_models: Optional list of available models
+        available_tools: Optional list of available tools
+
+    Returns:
+        ValidationResult with classified errors
+    """
+    context = ValidationContext(
+        nodes=nodes,
+        edges=edges or [],
+        available_models=available_models or [],
+        available_tools=available_tools or [],
+    )
+    engine = ValidationEngine()
+    return engine.validate(context)

api/core/workflow/generator/validation/rules.py

@@ -0,0 +1,947 @@
+"""
+Validation Rules Definition and Registry.
+
+This module defines:
+- ValidationRule: The rule structure
+- RuleCategory: Categories of validation rules
+- Severity: Error severity levels
+- ValidationError: Error output structure
+- All built-in validation rules
+"""
+
+import re
+from collections.abc import Callable
+from dataclasses import dataclass, field
+from enum import Enum
+from typing import TYPE_CHECKING, Any
+
+from core.workflow.generator.types import WorkflowNodeDict
+
+if TYPE_CHECKING:
+    from core.workflow.generator.validation.context import ValidationContext
+
+
+class RuleCategory(Enum):
+    """Categories of validation rules."""
+
+    STRUCTURE = "structure"  # Field existence, types, formats
+    SEMANTIC = "semantic"  # Variable references, edge connections
+    REFERENCE = "reference"  # External resources (models, tools, datasets)
+
+
+class Severity(Enum):
+    """Severity levels for validation errors."""
+
+    ERROR = "error"  # Must be fixed
+    WARNING = "warning"  # Should be fixed but not blocking
+
+
+@dataclass
+class ValidationError:
+    """
+    Represents a validation error found during rule execution.
+
+    Attributes:
+        rule_id: The ID of the rule that generated this error
+        node_id: The ID of the node with the error
+        node_type: The type of the node
+        category: The rule category
+        severity: Error severity
+        is_fixable: Whether LLM can auto-fix this error
+        message: Human-readable error message
+        fix_hint: Hint for LLM to fix the error
+        details: Additional error details
+    """
+
+    rule_id: str
+    node_id: str
+    node_type: str
+    category: RuleCategory
+    severity: Severity
+    is_fixable: bool
+    message: str
+    fix_hint: str = ""
+    details: dict[str, Any] = field(default_factory=dict)
+
+    def to_dict(self) -> dict[str, Any]:
+        """Convert to dictionary for API response."""
+        return {
+            "rule_id": self.rule_id,
+            "node_id": self.node_id,
+            "node_type": self.node_type,
+            "category": self.category.value,
+            "severity": self.severity.value,
+            "is_fixable": self.is_fixable,
+            "message": self.message,
+            "fix_hint": self.fix_hint,
+            "details": self.details,
+        }
+
+
+# Type alias for rule check functions
+RuleCheckFn = Callable[
+    [WorkflowNodeDict, "ValidationContext"],
+    list[ValidationError],
+]
+
+
+@dataclass
+class ValidationRule:
+    """
+    A validation rule definition.
+
+    Attributes:
+        id: Unique rule identifier (e.g., "llm.model.required")
+        node_types: List of node types this rule applies to, or ["*"] for all
+        category: The rule category
+        severity: Default severity for errors from this rule
+        is_fixable: Whether errors from this rule can be auto-fixed by LLM
+        check: The validation function
+        description: Human-readable description of what this rule checks
+        fix_hint: Default hint for fixing errors from this rule
+    """
+
+    id: str
+    node_types: list[str]
+    category: RuleCategory
+    severity: Severity
+    is_fixable: bool
+    check: RuleCheckFn
+    description: str = ""
+    fix_hint: str = ""
+
+    def applies_to(self, node_type: str) -> bool:
+        """Check if this rule applies to a given node type."""
+        return "*" in self.node_types or node_type in self.node_types
+
+
+# =============================================================================
+# Rule Registry
+# =============================================================================
+
+
+class RuleRegistry:
+    """
+    Registry for validation rules.
+
+    Rules are registered here and can be retrieved by category or node type.
+    """
+
+    def __init__(self):
+        self._rules: list[ValidationRule] = []
+
+    def register(self, rule: ValidationRule) -> None:
+        """Register a validation rule."""
+        self._rules.append(rule)
+
+    def get_rules_for_node(self, node_type: str) -> list[ValidationRule]:
+        """Get all rules that apply to a given node type."""
+        return [r for r in self._rules if r.applies_to(node_type)]
+
+    def get_rules_by_category(self, category: RuleCategory) -> list[ValidationRule]:
+        """Get all rules in a given category."""
+        return [r for r in self._rules if r.category == category]
+
+    def get_all_rules(self) -> list[ValidationRule]:
+        """Get all registered rules."""
+        return list(self._rules)
+
+
+# Global rule registry instance
+_registry = RuleRegistry()
+
+
+def register_rule(rule: ValidationRule) -> ValidationRule:
+    """Decorator/function to register a rule with the global registry."""
+    _registry.register(rule)
+    return rule
+
+
+def get_registry() -> RuleRegistry:
+    """Get the global rule registry."""
+    return _registry
+
+
+# =============================================================================
+# Helper Functions for Rule Implementations
+# =============================================================================
+
+# Explicit placeholder value defined in prompt contract
+# See: api/core/workflow/generator/prompts/vibe_prompts.py
+PLACEHOLDER_VALUE = "__PLACEHOLDER__"
+
+# Variable reference pattern: {{#node_id.field#}}
+VARIABLE_REF_PATTERN = re.compile(r"\{\{#([^.#]+)\.([^#]+)#\}\}")
+
+
+def is_placeholder(value: Any) -> bool:
+    """Check if a value appears to be a placeholder."""
+    if not isinstance(value, str):
+        return False
+    return value == PLACEHOLDER_VALUE or PLACEHOLDER_VALUE in value
+
+
+def extract_variable_refs(text: str) -> list[tuple[str, str]]:
+    """
+    Extract variable references from text.
+
+    Returns list of (node_id, field_name) tuples.
+    """
+    return VARIABLE_REF_PATTERN.findall(text)
+
+
+def check_required_field(
+    config: dict[str, Any],
+    field_name: str,
+    node_id: str,
+    node_type: str,
+    rule_id: str,
+    fix_hint: str = "",
+) -> ValidationError | None:
+    """Helper to check if a required field exists and is non-empty."""
+    value = config.get(field_name)
+    if value is None or value == "" or (isinstance(value, list) and len(value) == 0):
+        return ValidationError(
+            rule_id=rule_id,
+            node_id=node_id,
+            node_type=node_type,
+            category=RuleCategory.STRUCTURE,
+            severity=Severity.ERROR,
+            is_fixable=True,
+            message=f"Node '{node_id}': missing required field '{field_name}'",
+            fix_hint=fix_hint or f"Add '{field_name}' to the node config",
+        )
+    return None
+
+
+# =============================================================================
+# Structure Rules - Field existence, types, formats
+# =============================================================================
+
+
+def _check_llm_prompt_template(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that LLM node has prompt_template."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    config = node.get("config", {})
+
+    err = check_required_field(
+        config,
+        "prompt_template",
+        node_id,
+        "llm",
+        "llm.prompt_template.required",
+        "Add prompt_template with system and user messages",
+    )
+    if err:
+        errors.append(err)
+
+    return errors
+
+
+def _check_http_request_url(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that http-request node has url and method."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    config = node.get("config", {})
+
+    # Check url
+    url = config.get("url", "")
+    if not url:
+        errors.append(
+            ValidationError(
+                rule_id="http.url.required",
+                node_id=node_id,
+                node_type="http-request",
+                category=RuleCategory.STRUCTURE,
+                severity=Severity.ERROR,
+                is_fixable=True,
+                message=f"Node '{node_id}': http-request missing required 'url'",
+                fix_hint="Add url - use {{#start.url#}} or a concrete URL",
+            )
+        )
+    elif is_placeholder(url):
+        errors.append(
+            ValidationError(
+                rule_id="http.url.placeholder",
+                node_id=node_id,
+                node_type="http-request",
+                category=RuleCategory.STRUCTURE,
+                severity=Severity.ERROR,
+                is_fixable=True,
+                message=f"Node '{node_id}': url contains placeholder value",
+                fix_hint="Replace placeholder with actual URL or variable reference",
+            )
+        )
+
+    # Check method
+    method = config.get("method", "")
+    if not method:
+        errors.append(
+            ValidationError(
+                rule_id="http.method.required",
+                node_id=node_id,
+                node_type="http-request",
+                category=RuleCategory.STRUCTURE,
+                severity=Severity.ERROR,
+                is_fixable=True,
+                message=f"Node '{node_id}': http-request missing 'method'",
+                fix_hint="Add method: GET, POST, PUT, DELETE, or PATCH",
+            )
+        )
+
+    return errors
+
+
+def _check_code_node(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that code node has code and language."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    config = node.get("config", {})
+
+    err = check_required_field(
+        config,
+        "code",
+        node_id,
+        "code",
+        "code.code.required",
+        "Add code with a main() function that returns a dict",
+    )
+    if err:
+        errors.append(err)
+
+    err = check_required_field(
+        config,
+        "language",
+        node_id,
+        "code",
+        "code.language.required",
+        "Add language: python3 or javascript",
+    )
+    if err:
+        errors.append(err)
+
+    return errors
+
+
+def _check_question_classifier(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that question-classifier has classes."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    config = node.get("config", {})
+
+    err = check_required_field(
+        config,
+        "classes",
+        node_id,
+        "question-classifier",
+        "classifier.classes.required",
+        "Add classes array with id and name for each classification",
+    )
+    if err:
+        errors.append(err)
+
+    return errors
+
+
+def _check_parameter_extractor(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that parameter-extractor has parameters and instruction."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    config = node.get("config", {})
+
+    err = check_required_field(
+        config,
+        "parameters",
+        node_id,
+        "parameter-extractor",
+        "extractor.parameters.required",
+        "Add parameters array with name, type, description fields",
+    )
+    if err:
+        errors.append(err)
+    else:
+        # Check individual parameters for required fields
+        parameters = config.get("parameters", [])
+        if isinstance(parameters, list):
+            for i, param in enumerate(parameters):
+                if isinstance(param, dict):
+                    # Check for 'required' field (boolean)
+                    if "required" not in param:
+                        errors.append(
+                            ValidationError(
+                                rule_id="extractor.param.required_field.missing",
+                                node_id=node_id,
+                                node_type="parameter-extractor",
+                                category=RuleCategory.STRUCTURE,
+                                severity=Severity.ERROR,
+                                is_fixable=True,
+                                message=f"Node '{node_id}': parameter[{i}] missing 'required' field",
+                                fix_hint=f"Add 'required': True to parameter '{param.get('name', 'unknown')}'",
+                                details={"param_index": i, "param_name": param.get("name")},
+                            )
+                        )
+
+    # instruction is recommended but not strictly required
+    if not config.get("instruction"):
+        errors.append(
+            ValidationError(
+                rule_id="extractor.instruction.recommended",
+                node_id=node_id,
+                node_type="parameter-extractor",
+                category=RuleCategory.STRUCTURE,
+                severity=Severity.WARNING,
+                is_fixable=True,
+                message=f"Node '{node_id}': parameter-extractor should have 'instruction'",
+                fix_hint="Add instruction describing what to extract",
+            )
+        )
+
+    return errors
+
+
+def _check_knowledge_retrieval(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that knowledge-retrieval has dataset_ids."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    config = node.get("config", {})
+
+    dataset_ids = config.get("dataset_ids", [])
+    if not dataset_ids:
+        errors.append(
+            ValidationError(
+                rule_id="knowledge.dataset.required",
+                node_id=node_id,
+                node_type="knowledge-retrieval",
+                category=RuleCategory.STRUCTURE,
+                severity=Severity.ERROR,
+                is_fixable=False,  # User must select knowledge base
+                message=f"Node '{node_id}': knowledge-retrieval missing 'dataset_ids'",
+                fix_hint="User must select knowledge bases in the UI",
+            )
+        )
+    else:
+        # Check for placeholder values
+        for ds_id in dataset_ids:
+            if is_placeholder(ds_id):
+                errors.append(
+                    ValidationError(
+                        rule_id="knowledge.dataset.placeholder",
+                        node_id=node_id,
+                        node_type="knowledge-retrieval",
+                        category=RuleCategory.STRUCTURE,
+                        severity=Severity.ERROR,
+                        is_fixable=False,
+                        message=f"Node '{node_id}': dataset_ids contains placeholder",
+                        fix_hint="User must replace placeholder with actual knowledge base ID",
+                        details={"placeholder_value": ds_id},
+                    )
+                )
+                break
+
+    return errors
+
+
+def _check_end_node(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that end node has outputs defined."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    config = node.get("config", {})
+
+    outputs = config.get("outputs", [])
+    if not outputs:
+        errors.append(
+            ValidationError(
+                rule_id="end.outputs.recommended",
+                node_id=node_id,
+                node_type="end",
+                category=RuleCategory.STRUCTURE,
+                severity=Severity.WARNING,
+                is_fixable=True,
+                message="End node should define output variables",
+                fix_hint="Add outputs array with variable and value_selector",
+            )
+        )
+
+    return errors
+
+
+# =============================================================================
+# Semantic Rules - Variable references, edge connections
+# =============================================================================
+
+
+def _check_variable_references(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that variable references point to valid nodes."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    node_type = node.get("type", "unknown")
+    config = node.get("config", {})
+
+    # Get all valid node IDs (including 'start' which is always valid)
+    valid_node_ids = ctx.get_node_ids()
+    valid_node_ids.add("start")
+    valid_node_ids.add("sys")  # System variables
+
+    def check_text_for_refs(text: str, field_path: str) -> None:
+        if not isinstance(text, str):
+            return
+        refs = extract_variable_refs(text)
+        for ref_node_id, ref_field in refs:
+            if ref_node_id not in valid_node_ids:
+                errors.append(
+                    ValidationError(
+                        rule_id="variable.ref.invalid_node",
+                        node_id=node_id,
+                        node_type=node_type,
+                        category=RuleCategory.SEMANTIC,
+                        severity=Severity.ERROR,
+                        is_fixable=True,
+                        message=f"Node '{node_id}': references non-existent node '{ref_node_id}'",
+                        fix_hint=f"Change {{{{#{ref_node_id}.{ref_field}#}}}} to reference a valid node",
+                        details={"field_path": field_path, "invalid_ref": ref_node_id},
+                    )
+                )
+
+    # Check prompt_template for LLM nodes
+    prompt_template = config.get("prompt_template", [])
+    if isinstance(prompt_template, list):
+        for i, msg in enumerate(prompt_template):
+            if isinstance(msg, dict):
+                text = msg.get("text", "")
+                check_text_for_refs(text, f"prompt_template[{i}].text")
+
+    # Check instruction field
+    instruction = config.get("instruction", "")
+    check_text_for_refs(instruction, "instruction")
+
+    # Check url for http-request
+    url = config.get("url", "")
+    check_text_for_refs(url, "url")
+
+    return errors
+
+
+# NOTE: _check_node_has_outgoing_edge removed - handled by GraphValidator
+
+
+# NOTE: _check_node_has_incoming_edge removed - handled by GraphValidator
+
+
+# NOTE: _check_question_classifier_branches removed - handled by EdgeRepair
+
+
+# NOTE: _check_if_else_branches removed - handled by EdgeRepair
+
+
+def _check_if_else_operators(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that if-else comparison operators are valid."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    node_type = node.get("type", "unknown")
+
+    if node_type != "if-else":
+        return errors
+
+    valid_operators = {
+        "contains",
+        "not contains",
+        "start with",
+        "end with",
+        "is",
+        "is not",
+        "empty",
+        "not empty",
+        "in",
+        "not in",
+        "all of",
+        "=",
+        "≠",
+        ">",
+        "<",
+        "≥",
+        "≤",
+        "null",
+        "not null",
+        "exists",
+        "not exists",
+    }
+
+    config = node.get("config", {})
+    cases = config.get("cases", [])
+
+    for case in cases:
+        conditions = case.get("conditions", [])
+        for condition in conditions:
+            op = condition.get("comparison_operator")
+            if op and op not in valid_operators:
+                errors.append(
+                    ValidationError(
+                        rule_id="ifelse.operator.invalid",
+                        node_id=node_id,
+                        node_type=node_type,
+                        category=RuleCategory.SEMANTIC,
+                        severity=Severity.ERROR,
+                        is_fixable=True,
+                        message=f"Invalid operator '{op}' in if-else node",
+                        fix_hint=f"Use one of: {', '.join(sorted(valid_operators))}",
+                        details={"invalid_operator": op, "field": "config.cases.conditions.comparison_operator"},
+                    )
+                )
+
+    return errors
+
+
+def _check_edge_targets_exist(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that edge targets reference existing nodes."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    node_type = node.get("type", "unknown")
+
+    valid_node_ids = ctx.get_node_ids()
+
+    # Check all outgoing edges from this node
+    for edge in ctx.edges:
+        if edge.get("source") == node_id:
+            target = edge.get("target")
+            if target and target not in valid_node_ids:
+                errors.append(
+                    ValidationError(
+                        rule_id="edge.target.invalid",
+                        node_id=node_id,
+                        node_type=node_type,
+                        category=RuleCategory.SEMANTIC,
+                        severity=Severity.ERROR,
+                        is_fixable=True,
+                        message=f"Edge from '{node_id}' targets non-existent node '{target}'",
+                        fix_hint=f"Change edge target from '{target}' to an existing node",
+                        details={"invalid_target": target, "field": "edges"},
+                    )
+                )
+
+    return errors
+
+
+# =============================================================================
+# Reference Rules - External resources (models, tools, datasets)
+# =============================================================================
+
+# Node types that require model configuration
+MODEL_REQUIRED_NODE_TYPES = {"llm", "question-classifier", "parameter-extractor"}
+
+
+def _check_model_config(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that model configuration is valid."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    node_type = node.get("type", "unknown")
+    config = node.get("config", {})
+
+    if node_type not in MODEL_REQUIRED_NODE_TYPES:
+        return errors
+
+    model = config.get("model")
+
+    # Check if model config exists
+    if not model:
+        if ctx.available_models:
+            errors.append(
+                ValidationError(
+                    rule_id="model.required",
+                    node_id=node_id,
+                    node_type=node_type,
+                    category=RuleCategory.REFERENCE,
+                    severity=Severity.ERROR,
+                    is_fixable=True,
+                    message=f"Node '{node_id}' ({node_type}): missing required 'model' configuration",
+                    fix_hint="Add model config using one of the available models",
+                )
+            )
+        else:
+            errors.append(
+                ValidationError(
+                    rule_id="model.no_available",
+                    node_id=node_id,
+                    node_type=node_type,
+                    category=RuleCategory.REFERENCE,
+                    severity=Severity.ERROR,
+                    is_fixable=False,
+                    message=f"Node '{node_id}' ({node_type}): needs model but no models available",
+                    fix_hint="User must configure a model provider first",
+                )
+            )
+        return errors
+
+    # Check if model config is valid
+    if isinstance(model, dict):
+        provider = model.get("provider", "")
+        name = model.get("name", "")
+
+        # Check for placeholder values
+        if is_placeholder(provider) or is_placeholder(name):
+            if ctx.available_models:
+                errors.append(
+                    ValidationError(
+                        rule_id="model.placeholder",
+                        node_id=node_id,
+                        node_type=node_type,
+                        category=RuleCategory.REFERENCE,
+                        severity=Severity.ERROR,
+                        is_fixable=True,
+                        message=f"Node '{node_id}': model config contains placeholder",
+                        fix_hint="Replace placeholder with actual model from available_models",
+                    )
+                )
+            return errors
+
+        # Check if model exists in available_models
+        if ctx.available_models and provider and name:
+            if not ctx.has_model(provider, name):
+                errors.append(
+                    ValidationError(
+                        rule_id="model.not_found",
+                        node_id=node_id,
+                        node_type=node_type,
+                        category=RuleCategory.REFERENCE,
+                        severity=Severity.ERROR,
+                        is_fixable=True,
+                        message=f"Node '{node_id}': model '{provider}/{name}' not in available models",
+                        fix_hint="Replace with a model from available_models",
+                        details={"provider": provider, "model": name},
+                    )
+                )
+
+    return errors
+
+
+def _check_tool_reference(node: WorkflowNodeDict, ctx: "ValidationContext") -> list[ValidationError]:
+    """Check that tool references are valid and configured."""
+    errors: list[ValidationError] = []
+    node_id = node.get("id", "unknown")
+    node_type = node.get("type", "unknown")
+
+    if node_type != "tool":
+        return errors
+
+    config = node.get("config", {})
+    tool_ref = (
+        config.get("tool_key")
+        or config.get("tool_name")
+        or config.get("provider_id", "") + "/" + config.get("tool_name", "")
+    )
+
+    if not tool_ref:
+        errors.append(
+            ValidationError(
+                rule_id="tool.key.required",
+                node_id=node_id,
+                node_type=node_type,
+                category=RuleCategory.REFERENCE,
+                severity=Severity.ERROR,
+                is_fixable=True,
+                message=f"Node '{node_id}': tool node missing tool_key",
+                fix_hint="Add tool_key from available_tools",
+            )
+        )
+        return errors
+
+    # Check if tool exists
+    if not ctx.has_tool(tool_ref):
+        errors.append(
+            ValidationError(
+                rule_id="tool.not_found",
+                node_id=node_id,
+                node_type=node_type,
+                category=RuleCategory.REFERENCE,
+                severity=Severity.ERROR,
+                is_fixable=True,  # Can be replaced with http-request fallback
+                message=f"Node '{node_id}': tool '{tool_ref}' not found",
+                fix_hint="Use http-request or code node as fallback",
+                details={"tool_ref": tool_ref},
+            )
+        )
+    elif not ctx.is_tool_configured(tool_ref):
+        errors.append(
+            ValidationError(
+                rule_id="tool.not_configured",
+                node_id=node_id,
+                node_type=node_type,
+                category=RuleCategory.REFERENCE,
+                severity=Severity.WARNING,
+                is_fixable=False,  # User needs to configure
+                message=f"Node '{node_id}': tool '{tool_ref}' requires configuration",
+                fix_hint="Configure the tool in Tools settings",
+                details={"tool_ref": tool_ref},
+            )
+        )
+
+    return errors
+
+
+# =============================================================================
+# Register All Rules
+# =============================================================================
+
+# Structure Rules
+register_rule(
+    ValidationRule(
+        id="llm.prompt_template.required",
+        node_types=["llm"],
+        category=RuleCategory.STRUCTURE,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_llm_prompt_template,
+        description="LLM node must have prompt_template",
+        fix_hint="Add prompt_template with system and user messages",
+    )
+)
+
+register_rule(
+    ValidationRule(
+        id="http.config.required",
+        node_types=["http-request"],
+        category=RuleCategory.STRUCTURE,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_http_request_url,
+        description="HTTP request node must have url and method",
+        fix_hint="Add url and method to config",
+    )
+)
+
+register_rule(
+    ValidationRule(
+        id="code.config.required",
+        node_types=["code"],
+        category=RuleCategory.STRUCTURE,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_code_node,
+        description="Code node must have code and language",
+        fix_hint="Add code with main() function and language",
+    )
+)
+
+register_rule(
+    ValidationRule(
+        id="classifier.classes.required",
+        node_types=["question-classifier"],
+        category=RuleCategory.STRUCTURE,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_question_classifier,
+        description="Question classifier must have classes",
+        fix_hint="Add classes array with classification options",
+    )
+)
+
+register_rule(
+    ValidationRule(
+        id="extractor.config.required",
+        node_types=["parameter-extractor"],
+        category=RuleCategory.STRUCTURE,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_parameter_extractor,
+        description="Parameter extractor must have parameters",
+        fix_hint="Add parameters array",
+    )
+)
+
+register_rule(
+    ValidationRule(
+        id="knowledge.config.required",
+        node_types=["knowledge-retrieval"],
+        category=RuleCategory.STRUCTURE,
+        severity=Severity.ERROR,
+        is_fixable=False,
+        check=_check_knowledge_retrieval,
+        description="Knowledge retrieval must have dataset_ids",
+        fix_hint="User must select knowledge base",
+    )
+)
+
+register_rule(
+    ValidationRule(
+        id="end.outputs.check",
+        node_types=["end"],
+        category=RuleCategory.STRUCTURE,
+        severity=Severity.WARNING,
+        is_fixable=True,
+        check=_check_end_node,
+        description="End node should have outputs",
+        fix_hint="Add outputs array",
+    )
+)
+
+# Semantic Rules
+register_rule(
+    ValidationRule(
+        id="variable.references.valid",
+        node_types=["*"],
+        category=RuleCategory.SEMANTIC,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_variable_references,
+        description="Variable references must point to valid nodes",
+        fix_hint="Fix variable reference to use valid node ID",
+    )
+)
+
+# Edge Validation Rules
+# NOTE: Edge connectivity and branch completeness are now handled by:
+# - GraphValidator (BFS-based reachability analysis)
+# - EdgeRepair (automatic branch edge repair)
+
+register_rule(
+    ValidationRule(
+        id="edge.targets.valid",
+        node_types=["*"],
+        category=RuleCategory.SEMANTIC,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_edge_targets_exist,
+        description="Edge targets must reference existing nodes",
+        fix_hint="Change edge target to an existing node ID",
+    )
+)
+
+# Reference Rules
+register_rule(
+    ValidationRule(
+        id="model.config.valid",
+        node_types=["llm", "question-classifier", "parameter-extractor"],
+        category=RuleCategory.REFERENCE,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_model_config,
+        description="Model configuration must be valid",
+        fix_hint="Add valid model from available_models",
+    )
+)
+
+register_rule(
+    ValidationRule(
+        id="tool.reference.valid",
+        node_types=["tool"],
+        category=RuleCategory.REFERENCE,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_tool_reference,
+        description="Tool reference must be valid and configured",
+        fix_hint="Use valid tool or fallback node",
+    )
+)
+
+register_rule(
+    ValidationRule(
+        id="ifelse.operator.valid",
+        node_types=["if-else"],
+        category=RuleCategory.SEMANTIC,
+        severity=Severity.ERROR,
+        is_fixable=True,
+        check=_check_if_else_operators,
+        description="If-else operators must be valid",
+        fix_hint="Use standard operators like ≥, ≤, =, ≠",
+    )
+)

api/core/workflow/nodes/base/node.py

@@ -197,6 +197,14 @@ class Node(Generic[NodeDataT]):
 
         return None
 
+    @classmethod
+    def get_default_config_schema(cls) -> dict[str, Any] | None:
+        """
+        Get the default configuration schema for the node.
+        Used for LLM generation.
+        """
+        return None
+
     # Global registry populated via __init_subclass__
     _registry: ClassVar[dict["NodeType", dict[str, type["Node"]]]] = {}
 

api/core/workflow/nodes/end/end_node.py

@@ -1,3 +1,5 @@
+from typing import Any
+
 from core.workflow.enums import NodeExecutionType, NodeType, WorkflowNodeExecutionStatus
 from core.workflow.node_events import NodeRunResult
 from core.workflow.nodes.base.node import Node
@@ -9,6 +11,24 @@ class EndNode(Node[EndNodeData]):
     node_type = NodeType.END
     execution_type = NodeExecutionType.RESPONSE
 
+    @classmethod
+    def get_default_config_schema(cls) -> dict[str, Any] | None:
+        return {
+            "description": "Workflow exit point - defines output variables",
+            "required": ["outputs"],
+            "parameters": {
+                "outputs": {
+                    "type": "array",
+                    "description": "Output variables to return",
+                    "item_schema": {
+                        "variable": "string - output variable name",
+                        "type": "enum: string, number, object, array",
+                        "value_selector": "array - path to source value, e.g. ['node_id', 'field']",
+                    },
+                },
+            },
+        }
+
     @classmethod
     def version(cls) -> str:
         return "1"

api/core/workflow/nodes/start/start_node.py

@@ -15,6 +15,27 @@ class StartNode(Node[StartNodeData]):
     node_type = NodeType.START
     execution_type = NodeExecutionType.ROOT
 
+    @classmethod
+    def get_default_config_schema(cls) -> dict[str, Any] | None:
+        return {
+            "description": "Workflow entry point - defines input variables",
+            "required": [],
+            "parameters": {
+                "variables": {
+                    "type": "array",
+                    "description": "Input variables for the workflow",
+                    "item_schema": {
+                        "variable": "string - variable name",
+                        "label": "string - display label",
+                        "type": "enum: text-input, paragraph, number, select, file, file-list",
+                        "required": "boolean",
+                        "max_length": "number (optional)",
+                    },
+                },
+            },
+            "outputs": ["All defined variables are available as {{#start.variable_name#}}"],
+        }
+
     @classmethod
     def version(cls) -> str:
         return "1"

api/core/workflow/nodes/tool/tool_node.py

@@ -50,6 +50,19 @@ class ToolNode(Node[ToolNodeData]):
     def version(cls) -> str:
         return "1"
 
+    @classmethod
+    def get_default_config_schema(cls) -> dict[str, Any] | None:
+        return {
+            "description": "Execute an external tool",
+            "required": ["provider_id", "tool_id", "tool_parameters"],
+            "parameters": {
+                "provider_id": {"type": "string"},
+                "provider_type": {"type": "string"},
+                "tool_id": {"type": "string"},
+                "tool_parameters": {"type": "object"},
+            },
+        }
+
     def _run(self) -> Generator[NodeEventBase, None, None]:
         """
         Run the tool node

api/tests/unit_tests/core/llm_generator/test_mermaid_generator.py

@@ -0,0 +1,288 @@
+"""
+Unit tests for the Mermaid Generator.
+
+Tests cover:
+- Basic workflow rendering
+- Reserved word handling ('end' → 'end_node')
+- Question classifier multi-branch edges
+- If-else branch labels
+- Edge validation and skipping
+- Tool node formatting
+"""
+
+
+from core.workflow.generator.utils.mermaid_generator import generate_mermaid
+
+
+class TestBasicWorkflow:
+    """Tests for basic workflow Mermaid generation."""
+
+    def test_simple_start_end_workflow(self):
+        """Test simple Start → End workflow."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "title": "Start"},
+                {"id": "end", "type": "end", "title": "End"},
+            ],
+            "edges": [{"source": "start", "target": "end"}],
+        }
+        result = generate_mermaid(workflow_data)
+
+        assert "flowchart TD" in result
+        assert 'start["type=start|title=Start"]' in result
+        assert 'end_node["type=end|title=End"]' in result
+        assert "start --> end_node" in result
+
+    def test_start_llm_end_workflow(self):
+        """Test Start → LLM → End workflow."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "title": "Start"},
+                {"id": "llm", "type": "llm", "title": "Generate"},
+                {"id": "end", "type": "end", "title": "End"},
+            ],
+            "edges": [
+                {"source": "start", "target": "llm"},
+                {"source": "llm", "target": "end"},
+            ],
+        }
+        result = generate_mermaid(workflow_data)
+
+        assert 'llm["type=llm|title=Generate"]' in result
+        assert "start --> llm" in result
+        assert "llm --> end_node" in result
+
+    def test_empty_workflow(self):
+        """Test empty workflow returns minimal output."""
+        workflow_data = {"nodes": [], "edges": []}
+        result = generate_mermaid(workflow_data)
+
+        assert result == "flowchart TD"
+
+    def test_missing_keys_handled(self):
+        """Test workflow with missing keys doesn't crash."""
+        workflow_data = {}
+        result = generate_mermaid(workflow_data)
+
+        assert "flowchart TD" in result
+
+
+class TestReservedWords:
+    """Tests for reserved word handling in node IDs."""
+
+    def test_end_node_id_is_replaced(self):
+        """Test 'end' node ID is replaced with 'end_node'."""
+        workflow_data = {
+            "nodes": [{"id": "end", "type": "end", "title": "End"}],
+            "edges": [],
+        }
+        result = generate_mermaid(workflow_data)
+
+        # Should use end_node instead of end
+        assert "end_node[" in result
+        assert '"type=end|title=End"' in result
+
+    def test_subgraph_node_id_is_replaced(self):
+        """Test 'subgraph' node ID is replaced with 'subgraph_node'."""
+        workflow_data = {
+            "nodes": [{"id": "subgraph", "type": "code", "title": "Process"}],
+            "edges": [],
+        }
+        result = generate_mermaid(workflow_data)
+
+        assert "subgraph_node[" in result
+
+    def test_edge_uses_safe_ids(self):
+        """Test edges correctly reference safe IDs after replacement."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "title": "Start"},
+                {"id": "end", "type": "end", "title": "End"},
+            ],
+            "edges": [{"source": "start", "target": "end"}],
+        }
+        result = generate_mermaid(workflow_data)
+
+        # Edge should use end_node, not end
+        assert "start --> end_node" in result
+        assert "start --> end\n" not in result
+
+
+class TestBranchEdges:
+    """Tests for branching node edge labels."""
+
+    def test_question_classifier_source_handles(self):
+        """Test question-classifier edges with sourceHandle labels."""
+        workflow_data = {
+            "nodes": [
+                {"id": "classifier", "type": "question-classifier", "title": "Classify"},
+                {"id": "refund", "type": "llm", "title": "Handle Refund"},
+                {"id": "inquiry", "type": "llm", "title": "Handle Inquiry"},
+            ],
+            "edges": [
+                {"source": "classifier", "target": "refund", "sourceHandle": "refund"},
+                {"source": "classifier", "target": "inquiry", "sourceHandle": "inquiry"},
+            ],
+        }
+        result = generate_mermaid(workflow_data)
+
+        assert "classifier -->|refund| refund" in result
+        assert "classifier -->|inquiry| inquiry" in result
+
+    def test_if_else_true_false_handles(self):
+        """Test if-else edges with true/false labels."""
+        workflow_data = {
+            "nodes": [
+                {"id": "ifelse", "type": "if-else", "title": "Check"},
+                {"id": "yes_branch", "type": "llm", "title": "Yes"},
+                {"id": "no_branch", "type": "llm", "title": "No"},
+            ],
+            "edges": [
+                {"source": "ifelse", "target": "yes_branch", "sourceHandle": "true"},
+                {"source": "ifelse", "target": "no_branch", "sourceHandle": "false"},
+            ],
+        }
+        result = generate_mermaid(workflow_data)
+
+        assert "ifelse -->|true| yes_branch" in result
+        assert "ifelse -->|false| no_branch" in result
+
+    def test_source_handle_source_is_ignored(self):
+        """Test sourceHandle='source' doesn't add label."""
+        workflow_data = {
+            "nodes": [
+                {"id": "llm1", "type": "llm", "title": "LLM 1"},
+                {"id": "llm2", "type": "llm", "title": "LLM 2"},
+            ],
+            "edges": [{"source": "llm1", "target": "llm2", "sourceHandle": "source"}],
+        }
+        result = generate_mermaid(workflow_data)
+
+        # Should be plain arrow without label
+        assert "llm1 --> llm2" in result
+        assert "llm1 -->|source|" not in result
+
+
+class TestEdgeValidation:
+    """Tests for edge validation and error handling."""
+
+    def test_edge_with_missing_source_is_skipped(self):
+        """Test edge with non-existent source node is skipped."""
+        workflow_data = {
+            "nodes": [{"id": "end", "type": "end", "title": "End"}],
+            "edges": [{"source": "nonexistent", "target": "end"}],
+        }
+        result = generate_mermaid(workflow_data)
+
+        # Should not contain the invalid edge
+        assert "nonexistent" not in result
+        assert "-->" not in result or "nonexistent" not in result
+
+    def test_edge_with_missing_target_is_skipped(self):
+        """Test edge with non-existent target node is skipped."""
+        workflow_data = {
+            "nodes": [{"id": "start", "type": "start", "title": "Start"}],
+            "edges": [{"source": "start", "target": "nonexistent"}],
+        }
+        result = generate_mermaid(workflow_data)
+
+        # Edge should be skipped
+        assert "start --> nonexistent" not in result
+
+    def test_edge_without_source_or_target_is_skipped(self):
+        """Test edge missing source or target is skipped."""
+        workflow_data = {
+            "nodes": [{"id": "start", "type": "start", "title": "Start"}],
+            "edges": [{"source": "start"}, {"target": "start"}, {}],
+        }
+        result = generate_mermaid(workflow_data)
+
+        # No edges should be rendered
+        assert result.count("-->") == 0
+
+
+class TestToolNodes:
+    """Tests for tool node formatting."""
+
+    def test_tool_node_includes_tool_key(self):
+        """Test tool node includes tool_key in label."""
+        workflow_data = {
+            "nodes": [
+                {
+                    "id": "search",
+                    "type": "tool",
+                    "title": "Search",
+                    "config": {"tool_key": "google/search"},
+                }
+            ],
+            "edges": [],
+        }
+        result = generate_mermaid(workflow_data)
+
+        assert 'search["type=tool|title=Search|tool=google/search"]' in result
+
+    def test_tool_node_with_tool_name_fallback(self):
+        """Test tool node uses tool_name as fallback."""
+        workflow_data = {
+            "nodes": [
+                {
+                    "id": "tool1",
+                    "type": "tool",
+                    "title": "My Tool",
+                    "config": {"tool_name": "my_tool"},
+                }
+            ],
+            "edges": [],
+        }
+        result = generate_mermaid(workflow_data)
+
+        assert "tool=my_tool" in result
+
+    def test_tool_node_missing_tool_key_shows_unknown(self):
+        """Test tool node without tool_key shows 'unknown'."""
+        workflow_data = {
+            "nodes": [{"id": "tool1", "type": "tool", "title": "Tool", "config": {}}],
+            "edges": [],
+        }
+        result = generate_mermaid(workflow_data)
+
+        assert "tool=unknown" in result
+
+
+class TestNodeFormatting:
+    """Tests for node label formatting."""
+
+    def test_quotes_in_title_are_escaped(self):
+        """Test double quotes in title are replaced with single quotes."""
+        workflow_data = {
+            "nodes": [{"id": "llm", "type": "llm", "title": 'Say "Hello"'}],
+            "edges": [],
+        }
+        result = generate_mermaid(workflow_data)
+
+        # Double quotes should be replaced
+        assert "Say 'Hello'" in result
+        assert 'Say "Hello"' not in result
+
+    def test_node_without_id_is_skipped(self):
+        """Test node without id is skipped."""
+        workflow_data = {
+            "nodes": [{"type": "llm", "title": "No ID"}],
+            "edges": [],
+        }
+        result = generate_mermaid(workflow_data)
+
+        # Should only have flowchart header
+        lines = [line for line in result.split("\n") if line.strip()]
+        assert len(lines) == 1
+
+    def test_node_default_values(self):
+        """Test node with missing type/title uses defaults."""
+        workflow_data = {
+            "nodes": [{"id": "node1"}],
+            "edges": [],
+        }
+        result = generate_mermaid(workflow_data)
+
+        assert "type=unknown" in result
+        assert "title=Untitled" in result

api/tests/unit_tests/core/llm_generator/test_node_repair.py

@@ -0,0 +1,81 @@
+from core.workflow.generator.utils.node_repair import NodeRepair
+
+
+class TestNodeRepair:
+    """Tests for NodeRepair utility."""
+
+    def test_repair_if_else_valid_operators(self):
+        """Test that valid operators remain unchanged."""
+        nodes = [
+            {
+                "id": "node1",
+                "type": "if-else",
+                "config": {
+                    "cases": [
+                        {
+                            "conditions": [
+                                {"comparison_operator": "≥", "value": "1"},
+                                {"comparison_operator": "=", "value": "2"},
+                            ]
+                        }
+                    ]
+                },
+            }
+        ]
+        result = NodeRepair.repair(nodes)
+        assert result.was_repaired is False
+        assert result.nodes == nodes
+
+    def test_repair_if_else_invalid_operators(self):
+        """Test that invalid operators are normalized."""
+        nodes = [
+            {
+                "id": "node1",
+                "type": "if-else",
+                "config": {
+                    "cases": [
+                        {
+                            "conditions": [
+                                {"comparison_operator": ">=", "value": "1"},
+                                {"comparison_operator": "<=", "value": "2"},
+                                {"comparison_operator": "!=", "value": "3"},
+                                {"comparison_operator": "==", "value": "4"},
+                            ]
+                        }
+                    ]
+                },
+            }
+        ]
+        result = NodeRepair.repair(nodes)
+        assert result.was_repaired is True
+        assert len(result.repairs_made) == 4
+
+        conditions = result.nodes[0]["config"]["cases"][0]["conditions"]
+        assert conditions[0]["comparison_operator"] == "≥"
+        assert conditions[1]["comparison_operator"] == "≤"
+        assert conditions[2]["comparison_operator"] == "≠"
+        assert conditions[3]["comparison_operator"] == "="
+
+    def test_repair_ignores_other_nodes(self):
+        """Test that other node types are ignored."""
+        nodes = [{"id": "node1", "type": "llm", "config": {"some_field": ">="}}]
+        result = NodeRepair.repair(nodes)
+        assert result.was_repaired is False
+        assert result.nodes[0]["config"]["some_field"] == ">="
+
+    def test_repair_handles_missing_config(self):
+        """Test robustness against missing fields."""
+        nodes = [
+            {
+                "id": "node1",
+                "type": "if-else",
+                # Missing config
+            },
+            {
+                "id": "node2",
+                "type": "if-else",
+                "config": {},  # Missing cases
+            },
+        ]
+        result = NodeRepair.repair(nodes)
+        assert result.was_repaired is False

api/tests/unit_tests/core/llm_generator/test_node_schemas_validation.py

@@ -0,0 +1,99 @@
+"""
+Tests for node schemas validation.
+
+Ensures that the node configuration stays in sync with registered node types.
+"""
+
+from core.workflow.generator.config.node_schemas import (
+    get_builtin_node_schemas,
+    validate_node_schemas,
+)
+
+
+class TestNodeSchemasValidation:
+    """Tests for node schema validation utilities."""
+
+    def test_validate_node_schemas_returns_no_warnings(self):
+        """Ensure all registered node types have corresponding schemas."""
+        warnings = validate_node_schemas()
+        # If this test fails, it means a new node type was added but
+        # no schema was defined for it in node_schemas.py
+        assert len(warnings) == 0, (
+            f"Missing schemas for node types: {warnings}. "
+            "Please add schemas for these node types in node_schemas.py "
+            "or add them to _INTERNAL_NODE_TYPES if they don't need schemas."
+        )
+
+    def test_builtin_node_schemas_not_empty(self):
+        """Ensure BUILTIN_NODE_SCHEMAS contains expected node types."""
+        # get_builtin_node_schemas() includes dynamic schemas
+        all_schemas = get_builtin_node_schemas()
+        assert len(all_schemas) > 0
+        # Core node types should always be present
+        expected_types = ["llm", "code", "http-request", "if-else"]
+        for node_type in expected_types:
+            assert node_type in all_schemas, f"Missing schema for core node type: {node_type}"
+
+    def test_schema_structure(self):
+        """Ensure each schema has required fields."""
+        all_schemas = get_builtin_node_schemas()
+        for node_type, schema in all_schemas.items():
+            assert "description" in schema, f"Missing 'description' in schema for {node_type}"
+            # 'parameters' is optional but if present should be a dict
+            if "parameters" in schema:
+                assert isinstance(schema["parameters"], dict), (
+                    f"'parameters' in schema for {node_type} should be a dict"
+                )
+
+
+class TestNodeSchemasMerged:
+    """Tests to verify the merged configuration works correctly."""
+
+    def test_fallback_rules_available(self):
+        """Ensure FALLBACK_RULES is available from node_schemas."""
+        from core.workflow.generator.config.node_schemas import FALLBACK_RULES
+
+        assert len(FALLBACK_RULES) > 0
+        assert "http-request" in FALLBACK_RULES
+        assert "code" in FALLBACK_RULES
+        assert "llm" in FALLBACK_RULES
+
+    def test_node_type_aliases_available(self):
+        """Ensure NODE_TYPE_ALIASES is available from node_schemas."""
+        from core.workflow.generator.config.node_schemas import NODE_TYPE_ALIASES
+
+        assert len(NODE_TYPE_ALIASES) > 0
+        assert NODE_TYPE_ALIASES.get("gpt") == "llm"
+        assert NODE_TYPE_ALIASES.get("api") == "http-request"
+
+    def test_field_name_corrections_available(self):
+        """Ensure FIELD_NAME_CORRECTIONS is available from node_schemas."""
+        from core.workflow.generator.config.node_schemas import (
+            FIELD_NAME_CORRECTIONS,
+            get_corrected_field_name,
+        )
+
+        assert len(FIELD_NAME_CORRECTIONS) > 0
+        # Test the helper function
+        assert get_corrected_field_name("http-request", "text") == "body"
+        assert get_corrected_field_name("llm", "response") == "text"
+        assert get_corrected_field_name("code", "unknown") == "unknown"
+
+    def test_config_init_exports(self):
+        """Ensure config __init__.py exports all needed symbols."""
+        from core.workflow.generator.config import (
+            BUILTIN_NODE_SCHEMAS,
+            FALLBACK_RULES,
+            FIELD_NAME_CORRECTIONS,
+            NODE_TYPE_ALIASES,
+            get_corrected_field_name,
+            validate_node_schemas,
+        )
+
+        # Just verify imports work
+        assert BUILTIN_NODE_SCHEMAS is not None
+        assert FALLBACK_RULES is not None
+        assert FIELD_NAME_CORRECTIONS is not None
+        assert NODE_TYPE_ALIASES is not None
+        assert callable(get_corrected_field_name)
+        assert callable(validate_node_schemas)

api/tests/unit_tests/core/llm_generator/test_planner_prompts.py

@@ -0,0 +1,173 @@
+"""
+Unit tests for the Planner Prompts.
+
+Tests cover:
+- Tool formatting for planner context
+- Edge cases with missing fields
+- Empty tool lists
+"""
+
+
+from core.workflow.generator.prompts.planner_prompts import format_tools_for_planner
+
+
+class TestFormatToolsForPlanner:
+    """Tests for format_tools_for_planner function."""
+
+    def test_empty_tools_returns_default_message(self):
+        """Test empty tools list returns default message."""
+        result = format_tools_for_planner([])
+
+        assert result == "No external tools available."
+
+    def test_none_tools_returns_default_message(self):
+        """Test None tools list returns default message."""
+        result = format_tools_for_planner(None)
+
+        assert result == "No external tools available."
+
+    def test_single_tool_formatting(self):
+        """Test single tool is formatted correctly."""
+        tools = [
+            {
+                "provider_id": "google",
+                "tool_key": "search",
+                "tool_label": "Google Search",
+                "tool_description": "Search the web using Google",
+            }
+        ]
+        result = format_tools_for_planner(tools)
+
+        assert "[google/search]" in result
+        assert "Google Search" in result
+        assert "Search the web using Google" in result
+
+    def test_multiple_tools_formatting(self):
+        """Test multiple tools are formatted correctly."""
+        tools = [
+            {
+                "provider_id": "google",
+                "tool_key": "search",
+                "tool_label": "Search",
+                "tool_description": "Web search",
+            },
+            {
+                "provider_id": "slack",
+                "tool_key": "send_message",
+                "tool_label": "Send Message",
+                "tool_description": "Send a Slack message",
+            },
+        ]
+        result = format_tools_for_planner(tools)
+
+        lines = result.strip().split("\n")
+        assert len(lines) == 2
+        assert "[google/search]" in result
+        assert "[slack/send_message]" in result
+
+    def test_tool_without_provider_uses_key_only(self):
+        """Test tool without provider_id uses tool_key only."""
+        tools = [
+            {
+                "tool_key": "my_tool",
+                "tool_label": "My Tool",
+                "tool_description": "A custom tool",
+            }
+        ]
+        result = format_tools_for_planner(tools)
+
+        # Should format as [my_tool] without provider prefix
+        assert "[my_tool]" in result
+        assert "My Tool" in result
+
+    def test_tool_with_tool_name_fallback(self):
+        """Test tool uses tool_name when tool_key is missing."""
+        tools = [
+            {
+                "tool_name": "fallback_tool",
+                "description": "Fallback description",
+            }
+        ]
+        result = format_tools_for_planner(tools)
+
+        assert "fallback_tool" in result
+        assert "Fallback description" in result
+
+    def test_tool_with_missing_description(self):
+        """Test tool with missing description doesn't crash."""
+        tools = [
+            {
+                "provider_id": "test",
+                "tool_key": "tool1",
+                "tool_label": "Tool 1",
+            }
+        ]
+        result = format_tools_for_planner(tools)
+
+        assert "[test/tool1]" in result
+        assert "Tool 1" in result
+
+    def test_tool_with_all_missing_fields(self):
+        """Test tool with all fields missing uses defaults."""
+        tools = [{}]
+        result = format_tools_for_planner(tools)
+
+        # Should not crash, may produce minimal output
+        assert isinstance(result, str)
+
+    def test_tool_uses_provider_fallback(self):
+        """Test tool uses 'provider' when 'provider_id' is missing."""
+        tools = [
+            {
+                "provider": "openai",
+                "tool_key": "dalle",
+                "tool_label": "DALL-E",
+                "tool_description": "Generate images",
+            }
+        ]
+        result = format_tools_for_planner(tools)
+
+        assert "[openai/dalle]" in result
+
+    def test_tool_label_fallback_to_key(self):
+        """Test tool_label falls back to tool_key when missing."""
+        tools = [
+            {
+                "provider_id": "test",
+                "tool_key": "my_key",
+                "tool_description": "Description here",
+            }
+        ]
+        result = format_tools_for_planner(tools)
+
+        # Label should fallback to key
+        assert "my_key" in result
+        assert "Description here" in result
+
+
+class TestPlannerPromptConstants:
+    """Tests for planner prompt constant availability."""
+
+    def test_planner_system_prompt_exists(self):
+        """Test PLANNER_SYSTEM_PROMPT is defined."""
+        from core.workflow.generator.prompts.planner_prompts import PLANNER_SYSTEM_PROMPT
+
+        assert PLANNER_SYSTEM_PROMPT is not None
+        assert len(PLANNER_SYSTEM_PROMPT) > 0
+        assert "{tools_summary}" in PLANNER_SYSTEM_PROMPT
+
+    def test_planner_user_prompt_exists(self):
+        """Test PLANNER_USER_PROMPT is defined."""
+        from core.workflow.generator.prompts.planner_prompts import PLANNER_USER_PROMPT
+
+        assert PLANNER_USER_PROMPT is not None
+        assert "{instruction}" in PLANNER_USER_PROMPT
+
+    def test_planner_system_prompt_has_required_sections(self):
+        """Test PLANNER_SYSTEM_PROMPT has required XML sections."""
+        from core.workflow.generator.prompts.planner_prompts import PLANNER_SYSTEM_PROMPT
+
+        assert "<role>" in PLANNER_SYSTEM_PROMPT
+        assert "<task>" in PLANNER_SYSTEM_PROMPT
+        assert "<available_tools>" in PLANNER_SYSTEM_PROMPT
+        assert "<response_format>" in PLANNER_SYSTEM_PROMPT

api/tests/unit_tests/core/llm_generator/test_validation_engine.py

@@ -0,0 +1,536 @@
+"""
+Unit tests for the Validation Rule Engine.
+
+Tests cover:
+- Structure rules (required fields, types, formats)
+- Semantic rules (variable references, edge connections)
+- Reference rules (model exists, tool configured, dataset valid)
+- ValidationEngine integration
+"""
+
+
+from core.workflow.generator.validation import (
+    ValidationContext,
+    ValidationEngine,
+)
+from core.workflow.generator.validation.rules import (
+    extract_variable_refs,
+    is_placeholder,
+)
+
+
+class TestPlaceholderDetection:
+    """Tests for placeholder detection utility."""
+
+    def test_detects_please_select(self):
+        assert is_placeholder("PLEASE_SELECT_YOUR_MODEL") is True
+
+    def test_detects_your_prefix(self):
+        assert is_placeholder("YOUR_API_KEY") is True
+
+    def test_detects_todo(self):
+        assert is_placeholder("TODO: fill this in") is True
+
+    def test_detects_placeholder(self):
+        assert is_placeholder("PLACEHOLDER_VALUE") is True
+
+    def test_detects_example_prefix(self):
+        assert is_placeholder("EXAMPLE_URL") is True
+
+    def test_detects_replace_prefix(self):
+        assert is_placeholder("REPLACE_WITH_ACTUAL") is True
+
+    def test_case_insensitive(self):
+        assert is_placeholder("please_select") is True
+        assert is_placeholder("Please_Select") is True
+
+    def test_valid_values_not_detected(self):
+        assert is_placeholder("https://api.example.com") is False
+        assert is_placeholder("gpt-4") is False
+        assert is_placeholder("my_variable") is False
+
+    def test_non_string_returns_false(self):
+        assert is_placeholder(123) is False
+        assert is_placeholder(None) is False
+        assert is_placeholder(["list"]) is False
+
+
+class TestVariableRefExtraction:
+    """Tests for variable reference extraction."""
+
+    def test_extracts_simple_ref(self):
+        refs = extract_variable_refs("Hello {{#start.query#}}")
+        assert refs == [("start", "query")]
+
+    def test_extracts_multiple_refs(self):
+        refs = extract_variable_refs("{{#node1.output#}} and {{#node2.text#}}")
+        assert refs == [("node1", "output"), ("node2", "text")]
+
+    def test_extracts_nested_field(self):
+        refs = extract_variable_refs("{{#http_request.body#}}")
+        assert refs == [("http_request", "body")]
+
+    def test_no_refs_returns_empty(self):
+        refs = extract_variable_refs("No references here")
+        assert refs == []
+
+    def test_handles_malformed_refs(self):
+        refs = extract_variable_refs("{{#invalid}} and {{incomplete#}}")
+        assert refs == []
+
+
+class TestValidationContext:
+    """Tests for ValidationContext."""
+
+    def test_node_map_lookup(self):
+        ctx = ValidationContext(
+            nodes=[
+                {"id": "start", "type": "start"},
+                {"id": "llm_1", "type": "llm"},
+            ]
+        )
+        assert ctx.get_node("start") == {"id": "start", "type": "start"}
+        assert ctx.get_node("nonexistent") is None
+
+    def test_model_set(self):
+        ctx = ValidationContext(
+            available_models=[
+                {"provider": "openai", "model": "gpt-4"},
+                {"provider": "anthropic", "model": "claude-3"},
+            ]
+        )
+        assert ctx.has_model("openai", "gpt-4") is True
+        assert ctx.has_model("anthropic", "claude-3") is True
+        assert ctx.has_model("openai", "gpt-3.5") is False
+
+    def test_tool_set(self):
+        ctx = ValidationContext(
+            available_tools=[
+                {"provider_id": "google", "tool_key": "search", "is_team_authorization": True},
+                {"provider_id": "slack", "tool_key": "send_message", "is_team_authorization": False},
+            ]
+        )
+        assert ctx.has_tool("google/search") is True
+        assert ctx.has_tool("search") is True
+        assert ctx.is_tool_configured("google/search") is True
+        assert ctx.is_tool_configured("slack/send_message") is False
+
+    def test_upstream_downstream_nodes(self):
+        ctx = ValidationContext(
+            nodes=[
+                {"id": "start", "type": "start"},
+                {"id": "llm", "type": "llm"},
+                {"id": "end", "type": "end"},
+            ],
+            edges=[
+                {"source": "start", "target": "llm"},
+                {"source": "llm", "target": "end"},
+            ],
+        )
+        assert ctx.get_upstream_nodes("llm") == ["start"]
+        assert ctx.get_downstream_nodes("llm") == ["end"]
+
+
+class TestStructureRules:
+    """Tests for structure validation rules."""
+
+    def test_llm_missing_prompt_template(self):
+        ctx = ValidationContext(
+            nodes=[{"id": "llm_1", "type": "llm", "config": {}}]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        assert result.has_errors
+        errors = [e for e in result.all_errors if e.rule_id == "llm.prompt_template.required"]
+        assert len(errors) == 1
+        assert errors[0].is_fixable is True
+
+    def test_llm_with_prompt_template_passes(self):
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {
+                        "prompt_template": [
+                            {"role": "system", "text": "You are helpful"},
+                            {"role": "user", "text": "Hello"},
+                        ]
+                    },
+                }
+            ]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        # No prompt_template errors
+        errors = [e for e in result.all_errors if "prompt_template" in e.rule_id]
+        assert len(errors) == 0
+
+    def test_http_request_missing_url(self):
+        ctx = ValidationContext(
+            nodes=[{"id": "http_1", "type": "http-request", "config": {}}]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if "http.url" in e.rule_id]
+        assert len(errors) == 1
+        assert errors[0].is_fixable is True
+
+    def test_http_request_placeholder_url(self):
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "http_1",
+                    "type": "http-request",
+                    "config": {"url": "PLEASE_SELECT_YOUR_URL", "method": "GET"},
+                }
+            ]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if "placeholder" in e.rule_id]
+        assert len(errors) == 1
+
+    def test_code_node_missing_fields(self):
+        ctx = ValidationContext(
+            nodes=[{"id": "code_1", "type": "code", "config": {}}]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        error_rules = {e.rule_id for e in result.all_errors}
+        assert "code.code.required" in error_rules
+        assert "code.language.required" in error_rules
+
+    def test_knowledge_retrieval_missing_dataset(self):
+        ctx = ValidationContext(
+            nodes=[{"id": "kb_1", "type": "knowledge-retrieval", "config": {}}]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if "knowledge.dataset" in e.rule_id]
+        assert len(errors) == 1
+        assert errors[0].is_fixable is False  # User must configure
+
+
+class TestSemanticRules:
+    """Tests for semantic validation rules."""
+
+    def test_valid_variable_reference(self):
+        ctx = ValidationContext(
+            nodes=[
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {
+                        "prompt_template": [
+                            {"role": "user", "text": "Process: {{#start.query#}}"}
+                        ]
+                    },
+                },
+            ]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        # No variable reference errors
+        errors = [e for e in result.all_errors if "variable.ref" in e.rule_id]
+        assert len(errors) == 0
+
+    def test_invalid_variable_reference(self):
+        ctx = ValidationContext(
+            nodes=[
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {
+                        "prompt_template": [
+                            {"role": "user", "text": "Process: {{#nonexistent.field#}}"}
+                        ]
+                    },
+                },
+            ]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if "variable.ref" in e.rule_id]
+        assert len(errors) == 1
+        assert "nonexistent" in errors[0].message
+
+    def test_edge_validation(self):
+        ctx = ValidationContext(
+            nodes=[
+                {"id": "start", "type": "start", "config": {}},
+                {"id": "end", "type": "end", "config": {}},
+            ],
+            edges=[
+                {"source": "start", "target": "end"},
+                {"source": "nonexistent", "target": "end"},
+            ],
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if "edge" in e.rule_id]
+        assert len(errors) == 1
+        assert "nonexistent" in errors[0].message
+
+
+class TestReferenceRules:
+    """Tests for reference validation rules (models, tools)."""
+
+    def test_llm_missing_model_with_available(self):
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {"prompt_template": [{"role": "user", "text": "Hi"}]},
+                }
+            ],
+            available_models=[{"provider": "openai", "model": "gpt-4"}],
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if e.rule_id == "model.required"]
+        assert len(errors) == 1
+        assert errors[0].is_fixable is True
+
+    def test_llm_missing_model_no_available(self):
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {"prompt_template": [{"role": "user", "text": "Hi"}]},
+                }
+            ],
+            available_models=[],  # No models available
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if e.rule_id == "model.no_available"]
+        assert len(errors) == 1
+        assert errors[0].is_fixable is False
+
+    def test_llm_with_valid_model(self):
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {
+                        "prompt_template": [{"role": "user", "text": "Hi"}],
+                        "model": {"provider": "openai", "name": "gpt-4"},
+                    },
+                }
+            ],
+            available_models=[{"provider": "openai", "model": "gpt-4"}],
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if "model" in e.rule_id]
+        assert len(errors) == 0
+
+    def test_llm_with_invalid_model(self):
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {
+                        "prompt_template": [{"role": "user", "text": "Hi"}],
+                        "model": {"provider": "openai", "name": "gpt-99"},
+                    },
+                }
+            ],
+            available_models=[{"provider": "openai", "model": "gpt-4"}],
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if e.rule_id == "model.not_found"]
+        assert len(errors) == 1
+        assert errors[0].is_fixable is True
+
+    def test_tool_node_not_found(self):
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "tool_1",
+                    "type": "tool",
+                    "config": {"tool_key": "nonexistent/tool"},
+                }
+            ],
+            available_tools=[],
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if e.rule_id == "tool.not_found"]
+        assert len(errors) == 1
+
+    def test_tool_node_not_configured(self):
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "tool_1",
+                    "type": "tool",
+                    "config": {"tool_key": "google/search"},
+                }
+            ],
+            available_tools=[
+                {"provider_id": "google", "tool_key": "search", "is_team_authorization": False}
+            ],
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        errors = [e for e in result.all_errors if e.rule_id == "tool.not_configured"]
+        assert len(errors) == 1
+        assert errors[0].is_fixable is False
+
+
+class TestValidationResult:
+    """Tests for ValidationResult classification."""
+
+    def test_has_errors(self):
+        ctx = ValidationContext(
+            nodes=[{"id": "llm_1", "type": "llm", "config": {}}]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        assert result.has_errors is True
+        assert result.is_valid is False
+
+    def test_has_fixable_errors(self):
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {"prompt_template": [{"role": "user", "text": "Hi"}]},
+                }
+            ],
+            available_models=[{"provider": "openai", "model": "gpt-4"}],
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        assert result.has_fixable_errors is True
+        assert len(result.fixable_errors) > 0
+
+    def test_get_fixable_by_node(self):
+        ctx = ValidationContext(
+            nodes=[
+                {"id": "llm_1", "type": "llm", "config": {}},
+                {"id": "http_1", "type": "http-request", "config": {}},
+            ]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        by_node = result.get_fixable_by_node()
+        assert "llm_1" in by_node
+        assert "http_1" in by_node
+
+    def test_to_dict(self):
+        ctx = ValidationContext(
+            nodes=[{"id": "llm_1", "type": "llm", "config": {}}]
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        d = result.to_dict()
+        assert "fixable" in d
+        assert "user_required" in d
+        assert "warnings" in d
+        assert "all_warnings" in d
+        assert "stats" in d
+
+
+class TestIntegration:
+    """Integration tests for the full validation pipeline."""
+
+    def test_complete_workflow_validation(self):
+        """Test validation of a complete workflow."""
+        ctx = ValidationContext(
+            nodes=[
+                {
+                    "id": "start",
+                    "type": "start",
+                    "config": {"variables": [{"variable": "query", "type": "text-input"}]},
+                },
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {
+                        "model": {"provider": "openai", "name": "gpt-4"},
+                        "prompt_template": [{"role": "user", "text": "{{#start.query#}}"}],
+                    },
+                },
+                {
+                    "id": "end",
+                    "type": "end",
+                    "config": {"outputs": [{"variable": "result", "value_selector": ["llm_1", "text"]}]},
+                },
+            ],
+            edges=[
+                {"source": "start", "target": "llm_1"},
+                {"source": "llm_1", "target": "end"},
+            ],
+            available_models=[{"provider": "openai", "model": "gpt-4"}],
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        # Should have no errors
+        assert result.is_valid is True
+        assert len(result.fixable_errors) == 0
+        assert len(result.user_required_errors) == 0
+
+    def test_workflow_with_multiple_errors(self):
+        """Test workflow with multiple types of errors."""
+        ctx = ValidationContext(
+            nodes=[
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "llm_1",
+                    "type": "llm",
+                    "config": {},  # Missing prompt_template and model
+                },
+                {
+                    "id": "kb_1",
+                    "type": "knowledge-retrieval",
+                    "config": {"dataset_ids": ["PLEASE_SELECT_YOUR_DATASET"]},
+                },
+                {"id": "end", "type": "end", "config": {}},
+            ],
+            available_models=[{"provider": "openai", "model": "gpt-4"}],
+        )
+        engine = ValidationEngine()
+        result = engine.validate(ctx)
+
+        # Should have multiple errors
+        assert result.has_errors is True
+        assert len(result.fixable_errors) >= 2  # model, prompt_template
+        assert len(result.user_required_errors) >= 1  # dataset placeholder
+
+        # Check stats
+        assert result.stats["total_nodes"] == 4
+        assert result.stats["total_errors"] >= 3
+
+
+

api/tests/unit_tests/core/llm_generator/test_workflow_validator_vibe.py

@@ -0,0 +1,435 @@
+"""
+Unit tests for the Vibe Workflow Validator.
+
+Tests cover:
+- Basic validation function
+- User-friendly validation hints
+- Edge cases and error handling
+"""
+
+
+from core.workflow.generator.utils.workflow_validator import ValidationHint, WorkflowValidator
+
+
+class TestValidationHint:
+    """Tests for ValidationHint dataclass."""
+
+    def test_hint_creation(self):
+        """Test creating a validation hint."""
+        hint = ValidationHint(
+            node_id="llm_1",
+            field="model",
+            message="Model is not configured",
+            severity="error",
+        )
+        assert hint.node_id == "llm_1"
+        assert hint.field == "model"
+        assert hint.message == "Model is not configured"
+        assert hint.severity == "error"
+
+    def test_hint_with_suggestion(self):
+        """Test hint with suggestion."""
+        hint = ValidationHint(
+            node_id="http_1",
+            field="url",
+            message="URL is required",
+            severity="error",
+            suggestion="Add a valid URL like https://api.example.com",
+        )
+        assert hint.suggestion is not None
+
+
+class TestWorkflowValidatorBasic:
+    """Tests for basic validation scenarios."""
+
+    def test_empty_workflow_is_valid(self):
+        """Test empty workflow passes validation."""
+        workflow_data = {"nodes": [], "edges": []}
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+
+        # Empty but valid structure
+        assert is_valid is True
+        assert len(hints) == 0
+
+    def test_minimal_valid_workflow(self):
+        """Test minimal Start → End workflow."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {}},
+                {"id": "end", "type": "end", "config": {}},
+            ],
+            "edges": [{"source": "start", "target": "end"}],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+
+        assert is_valid is True
+
+    def test_complete_workflow_with_llm(self):
+        """Test complete workflow with LLM node."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {"variables": []}},
+                {
+                    "id": "llm",
+                    "type": "llm",
+                    "config": {
+                        "model": {"provider": "openai", "name": "gpt-4"},
+                        "prompt_template": [{"role": "user", "text": "Hello"}],
+                    },
+                },
+                {"id": "end", "type": "end", "config": {"outputs": []}},
+            ],
+            "edges": [
+                {"source": "start", "target": "llm"},
+                {"source": "llm", "target": "end"},
+            ],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+
+        # Should pass with no critical errors
+        errors = [h for h in hints if h.severity == "error"]
+        assert len(errors) == 0
+
+
+class TestVariableReferenceValidation:
+    """Tests for variable reference validation."""
+
+    def test_valid_variable_reference(self):
+        """Test valid variable reference passes."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "llm",
+                    "type": "llm",
+                    "config": {"prompt_template": [{"role": "user", "text": "Query: {{#start.query#}}"}]},
+                },
+            ],
+            "edges": [{"source": "start", "target": "llm"}],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+
+        ref_errors = [h for h in hints if "reference" in h.message.lower()]
+        assert len(ref_errors) == 0
+
+    def test_invalid_variable_reference(self):
+        """Test invalid variable reference generates hint."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "llm",
+                    "type": "llm",
+                    "config": {"prompt_template": [{"role": "user", "text": "{{#nonexistent.field#}}"}]},
+                },
+            ],
+            "edges": [{"source": "start", "target": "llm"}],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+
+        # Should have a hint about invalid reference
+        ref_hints = [h for h in hints if "nonexistent" in h.message or "reference" in h.message.lower()]
+        assert len(ref_hints) >= 1
+
+
+class TestEdgeValidation:
+    """Tests for edge validation."""
+
+    def test_edge_with_invalid_source(self):
+        """Test edge with non-existent source generates hint."""
+        workflow_data = {
+            "nodes": [{"id": "end", "type": "end", "config": {}}],
+            "edges": [{"source": "nonexistent", "target": "end"}],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+
+        # Should have hint about invalid edge
+        edge_hints = [h for h in hints if "edge" in h.message.lower() or "source" in h.message.lower()]
+        assert len(edge_hints) >= 1
+
+    def test_edge_with_invalid_target(self):
+        """Test edge with non-existent target generates hint."""
+        workflow_data = {
+            "nodes": [{"id": "start", "type": "start", "config": {}}],
+            "edges": [{"source": "start", "target": "nonexistent"}],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+
+        edge_hints = [h for h in hints if "edge" in h.message.lower() or "target" in h.message.lower()]
+        assert len(edge_hints) >= 1
+
+
+class TestToolValidation:
+    """Tests for tool node validation."""
+
+    def test_tool_node_found_in_available(self):
+        """Test tool node that exists in available tools."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "tool1",
+                    "type": "tool",
+                    "config": {"tool_key": "google/search"},
+                },
+                {"id": "end", "type": "end", "config": {}},
+            ],
+            "edges": [{"source": "start", "target": "tool1"}, {"source": "tool1", "target": "end"}],
+        }
+        available_tools = [{"provider_id": "google", "tool_key": "search", "is_team_authorization": True}]
+        is_valid, hints = WorkflowValidator.validate(workflow_data, available_tools)
+
+        tool_errors = [h for h in hints if h.severity == "error" and "tool" in h.message.lower()]
+        assert len(tool_errors) == 0
+
+    def test_tool_node_not_found(self):
+        """Test tool node not in available tools generates hint."""
+        workflow_data = {
+            "nodes": [
+                {
+                    "id": "tool1",
+                    "type": "tool",
+                    "config": {"tool_key": "unknown/tool"},
+                }
+            ],
+            "edges": [],
+        }
+        available_tools = []
+        is_valid, hints = WorkflowValidator.validate(workflow_data, available_tools)
+
+        tool_hints = [h for h in hints if "tool" in h.message.lower()]
+        assert len(tool_hints) >= 1
+
+
+class TestQuestionClassifierValidation:
+    """Tests for question-classifier node validation."""
+
+    def test_question_classifier_with_classes(self):
+        """Test question-classifier with valid classes."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "classifier",
+                    "type": "question-classifier",
+                    "config": {
+                        "classes": [
+                            {"id": "class1", "name": "Class 1"},
+                            {"id": "class2", "name": "Class 2"},
+                        ],
+                        "model": {"provider": "openai", "name": "gpt-4", "mode": "chat"},
+                    },
+                },
+                {"id": "h1", "type": "llm", "config": {}},
+                {"id": "h2", "type": "llm", "config": {}},
+                {"id": "end", "type": "end", "config": {}},
+            ],
+            "edges": [
+                {"source": "start", "target": "classifier"},
+                {"source": "classifier", "sourceHandle": "class1", "target": "h1"},
+                {"source": "classifier", "sourceHandle": "class2", "target": "h2"},
+                {"source": "h1", "target": "end"},
+                {"source": "h2", "target": "end"},
+            ],
+        }
+        available_models = [{"provider": "openai", "model": "gpt-4", "mode": "chat"}]
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [], available_models=available_models)
+
+        class_errors = [h for h in hints if "class" in h.message.lower() and h.severity == "error"]
+        assert len(class_errors) == 0
+
+    def test_question_classifier_missing_classes(self):
+        """Test question-classifier without classes generates hint."""
+        workflow_data = {
+            "nodes": [
+                {
+                    "id": "classifier",
+                    "type": "question-classifier",
+                    "config": {"model": {"provider": "openai", "name": "gpt-4", "mode": "chat"}},
+                }
+            ],
+            "edges": [],
+        }
+        available_models = [{"provider": "openai", "model": "gpt-4", "mode": "chat"}]
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [], available_models=available_models)
+
+        # Should have hint about missing classes
+        class_hints = [h for h in hints if "class" in h.message.lower()]
+        assert len(class_hints) >= 1
+
+
+class TestHttpRequestValidation:
+    """Tests for HTTP request node validation."""
+
+    def test_http_request_with_url(self):
+        """Test HTTP request with valid URL."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "http",
+                    "type": "http-request",
+                    "config": {"url": "https://api.example.com", "method": "GET"},
+                },
+                {"id": "end", "type": "end", "config": {}},
+            ],
+            "edges": [{"source": "start", "target": "http"}, {"source": "http", "target": "end"}],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+
+        url_errors = [h for h in hints if "url" in h.message.lower() and h.severity == "error"]
+        assert len(url_errors) == 0
+
+    def test_http_request_missing_url(self):
+        """Test HTTP request without URL generates hint."""
+        workflow_data = {
+            "nodes": [
+                {
+                    "id": "http",
+                    "type": "http-request",
+                    "config": {"method": "GET"},
+                }
+            ],
+            "edges": [],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+
+        url_hints = [h for h in hints if "url" in h.message.lower()]
+        assert len(url_hints) >= 1
+
+
+class TestParameterExtractorValidation:
+    """Tests for parameter-extractor node validation."""
+
+    def test_parameter_extractor_valid_params(self):
+        """Test parameter-extractor with valid parameters."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "extractor",
+                    "type": "parameter-extractor",
+                    "config": {
+                        "instruction": "Extract info",
+                        "parameters": [
+                            {
+                                "name": "name",
+                                "type": "string",
+                                "description": "Name",
+                                "required": True,
+                            }
+                        ],
+                        "model": {"provider": "openai", "name": "gpt-4", "mode": "chat"},
+                    },
+                },
+                {"id": "end", "type": "end", "config": {}},
+            ],
+            "edges": [{"source": "start", "target": "extractor"}, {"source": "extractor", "target": "end"}],
+        }
+        available_models = [{"provider": "openai", "model": "gpt-4", "mode": "chat"}]
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [], available_models=available_models)
+
+        errors = [h for h in hints if h.severity == "error"]
+        assert len(errors) == 0
+
+    def test_parameter_extractor_missing_required_field(self):
+        """Test parameter-extractor missing 'required' field in parameter item."""
+        workflow_data = {
+            "nodes": [
+                {
+                    "id": "extractor",
+                    "type": "parameter-extractor",
+                    "config": {
+                        "instruction": "Extract info",
+                        "parameters": [
+                            {
+                                "name": "name",
+                                "type": "string",
+                                "description": "Name",
+                                # Missing 'required'
+                            }
+                        ],
+                        "model": {"provider": "openai", "name": "gpt-4", "mode": "chat"},
+                    },
+                }
+            ],
+            "edges": [],
+        }
+        available_models = [{"provider": "openai", "model": "gpt-4", "mode": "chat"}]
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [], available_models=available_models)
+
+        errors = [h for h in hints if "required" in h.message and h.severity == "error"]
+        assert len(errors) >= 1
+        assert "parameter-extractor" in errors[0].node_type
+
+
+class TestIfElseValidation:
+    """Tests for if-else node validation."""
+
+    def test_if_else_valid_operators(self):
+        """Test if-else with valid operators."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "ifelse",
+                    "type": "if-else",
+                    "config": {
+                        "cases": [{"case_id": "c1", "conditions": [{"comparison_operator": "≥", "value": "1"}]}]
+                    },
+                },
+                {"id": "t", "type": "llm", "config": {}},
+                {"id": "f", "type": "llm", "config": {}},
+                {"id": "end", "type": "end", "config": {}},
+            ],
+            "edges": [
+                {"source": "start", "target": "ifelse"},
+                {"source": "ifelse", "sourceHandle": "true", "target": "t"},
+                {"source": "ifelse", "sourceHandle": "false", "target": "f"},
+                {"source": "t", "target": "end"},
+                {"source": "f", "target": "end"},
+            ],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+        errors = [h for h in hints if h.severity == "error"]
+        # Filter out LLM model errors if any (available tools/models check might trigger)
+        # (actually available_models empty list might trigger model error?
+        # No, model config validation skips if model field not present? No, LLM has model config.
+        # But logic skips check if key missing? Let's check logic.
+        # _check_model_config checks if provider/name match available. If available is empty, it fails.
+        # But wait, validate default available_models is None?
+        # I should provide mock available_models or ignore model errors.
+
+        # Actually LLM node "config": {} implies missing model config. Rules check if config structure is valid?
+        # Let's filter specifically for operator errors.
+        operator_errors = [h for h in errors if "operator" in h.message]
+        assert len(operator_errors) == 0
+
+    def test_if_else_invalid_operators(self):
+        """Test if-else with invalid operators."""
+        workflow_data = {
+            "nodes": [
+                {"id": "start", "type": "start", "config": {}},
+                {
+                    "id": "ifelse",
+                    "type": "if-else",
+                    "config": {
+                        "cases": [{"case_id": "c1", "conditions": [{"comparison_operator": ">=", "value": "1"}]}]
+                    },
+                },
+                {"id": "t", "type": "llm", "config": {}},
+                {"id": "f", "type": "llm", "config": {}},
+                {"id": "end", "type": "end", "config": {}},
+            ],
+            "edges": [
+                {"source": "start", "target": "ifelse"},
+                {"source": "ifelse", "sourceHandle": "true", "target": "t"},
+                {"source": "ifelse", "sourceHandle": "false", "target": "f"},
+                {"source": "t", "target": "end"},
+                {"source": "f", "target": "end"},
+            ],
+        }
+        is_valid, hints = WorkflowValidator.validate(workflow_data, [])
+        operator_errors = [h for h in hints if "operator" in h.message and h.severity == "error"]
+        assert len(operator_errors) > 0
+        assert "≥" in operator_errors[0].suggestion

web/app/components/workflow/hooks/__tests__/use-workflow-vibe.test.ts

@@ -0,0 +1,82 @@
+
+import { describe, it, expect } from 'vitest'
+import { replaceVariableReferences } from '../use-workflow-vibe'
+import { BlockEnum } from '@/app/components/workflow/types'
+
+// Mock types needed for the test
+interface NodeData {
+    title: string
+    [key: string]: any
+}
+
+describe('use-workflow-vibe', () => {
+    describe('replaceVariableReferences', () => {
+        it('should replace variable references in strings', () => {
+            const data = {
+                title: 'Test Node',
+                prompt: 'Hello {{#old_id.query#}}',
+            }
+            const nodeIdMap = new Map<string, any>()
+            nodeIdMap.set('old_id', { id: 'new_uuid', data: { type: 'llm' } })
+
+            const result = replaceVariableReferences(data, nodeIdMap) as NodeData
+            expect(result.prompt).toBe('Hello {{#new_uuid.query#}}')
+        })
+
+        it('should handle multiple references in one string', () => {
+            const data = {
+                title: 'Test Node',
+                text: '{{#node1.out#}} and {{#node2.out#}}',
+            }
+            const nodeIdMap = new Map<string, any>()
+            nodeIdMap.set('node1', { id: 'uuid1', data: { type: 'llm' } })
+            nodeIdMap.set('node2', { id: 'uuid2', data: { type: 'llm' } })
+
+            const result = replaceVariableReferences(data, nodeIdMap) as NodeData
+            expect(result.text).toBe('{{#uuid1.out#}} and {{#uuid2.out#}}')
+        })
+
+        it('should replace variable references in value_selector arrays', () => {
+            const data = {
+                title: 'End Node',
+                outputs: [
+                    {
+                        variable: 'result',
+                        value_selector: ['old_id', 'text'],
+                    },
+                ],
+            }
+            const nodeIdMap = new Map<string, any>()
+            nodeIdMap.set('old_id', { id: 'new_uuid', data: { type: 'llm' } })
+
+            const result = replaceVariableReferences(data, nodeIdMap) as NodeData
+            expect(result.outputs[0].value_selector).toEqual(['new_uuid', 'text'])
+        })
+
+        it('should handle nested objects recursively', () => {
+            const data = {
+                config: {
+                    model: {
+                        prompt: '{{#old_id.text#}}',
+                    },
+                },
+            }
+            const nodeIdMap = new Map<string, any>()
+            nodeIdMap.set('old_id', { id: 'new_uuid', data: { type: 'llm' } })
+
+            const result = replaceVariableReferences(data, nodeIdMap) as any
+            expect(result.config.model.prompt).toBe('{{#new_uuid.text#}}')
+        })
+
+        it('should ignoring missing node mappings', () => {
+            const data = {
+                text: '{{#missing_id.text#}}',
+            }
+            const nodeIdMap = new Map<string, any>()
+            // missing_id is not in map
+
+            const result = replaceVariableReferences(data, nodeIdMap) as NodeData
+            expect(result.text).toBe('{{#missing_id.text#}}')
+        })
+    })
+})

web/app/components/workflow/hooks/index.ts

@@ -25,3 +25,4 @@ export * from './use-workflow-search'
 export * from './use-workflow-start-run'
 export * from './use-workflow-variables'
 export * from './use-workflow-vibe'
+export * from './use-workflow-vibe-config'

web/app/components/workflow/hooks/use-checklist.ts

@@ -159,7 +159,7 @@ export const useChecklist = (nodes: Node[], edges: Edge[]) => {
         }
       }
       else {
-        usedVars = getNodeUsedVars(node).filter(v => v.length > 0)
+        usedVars = getNodeUsedVars(node).filter(v => v && v.length > 0)
       }
 
       if (node.type === CUSTOM_NODE) {
@@ -355,7 +355,7 @@ export const useChecklistBeforePublish = () => {
         }
       }
       else {
-        usedVars = getNodeUsedVars(node).filter(v => v.length > 0)
+        usedVars = getNodeUsedVars(node).filter(v => v && v.length > 0)
       }
       const checkData = getCheckData(node.data, datasets)
       const { errorMessage } = nodesExtraData![node.data.type as BlockEnum].checkValid(checkData, t, moreDataForCheckValid)

web/app/components/workflow/hooks/use-workflow-vibe-config.ts

@@ -0,0 +1,99 @@
+/**
+ * Vibe Workflow Generator Configuration
+ *
+ * This module centralizes configuration for the Vibe workflow generation feature,
+ * including node type aliases and field name corrections.
+ *
+ * Note: These definitions are mirrored in the backend at:
+ * api/core/workflow/generator/config/node_schemas.py
+ * When updating these values, also update the backend file.
+ */
+
+/**
+ * Node type aliases for inference from natural language.
+ * Maps common terms to canonical node type names.
+ */
+export const NODE_TYPE_ALIASES: Record<string, string> = {
+  // Start node aliases
+  'start': 'start',
+  'begin': 'start',
+  'input': 'start',
+  // End node aliases
+  'end': 'end',
+  'finish': 'end',
+  'output': 'end',
+  // LLM node aliases
+  'llm': 'llm',
+  'ai': 'llm',
+  'gpt': 'llm',
+  'model': 'llm',
+  'chat': 'llm',
+  // Code node aliases
+  'code': 'code',
+  'script': 'code',
+  'python': 'code',
+  'javascript': 'code',
+  // HTTP request node aliases
+  'http-request': 'http-request',
+  'http': 'http-request',
+  'request': 'http-request',
+  'api': 'http-request',
+  'fetch': 'http-request',
+  'webhook': 'http-request',
+  // Conditional node aliases
+  'if-else': 'if-else',
+  'condition': 'if-else',
+  'branch': 'if-else',
+  'switch': 'if-else',
+  // Loop node aliases
+  'iteration': 'iteration',
+  'loop': 'loop',
+  'foreach': 'iteration',
+  // Tool node alias
+  'tool': 'tool',
+}
+
+/**
+ * Field name corrections for LLM-generated node configs.
+ * Maps incorrect field names to correct ones for specific node types.
+ */
+export const FIELD_NAME_CORRECTIONS: Record<string, Record<string, string>> = {
+  'http-request': {
+    text: 'body', // LLM might use "text" instead of "body"
+    content: 'body',
+    response: 'body',
+  },
+  'code': {
+    text: 'result', // LLM might use "text" instead of "result"
+    output: 'result',
+  },
+  'llm': {
+    response: 'text',
+    answer: 'text',
+  },
+}
+
+/**
+ * Correct field names based on node type.
+ * LLM sometimes generates wrong field names (e.g., "text" instead of "body" for HTTP nodes).
+ *
+ * @param field - The field name to correct
+ * @param nodeType - The type of the node
+ * @returns The corrected field name, or the original if no correction needed
+ */
+export const correctFieldName = (field: string, nodeType: string): string => {
+  const corrections = FIELD_NAME_CORRECTIONS[nodeType]
+  if (corrections && corrections[field])
+    return corrections[field]
+  return field
+}
+
+/**
+ * Get the canonical node type from an alias.
+ *
+ * @param alias - The alias to look up
+ * @returns The canonical node type, or undefined if not found
+ */
+export const getCanonicalNodeType = (alias: string): string | undefined => {
+  return NODE_TYPE_ALIASES[alias.toLowerCase()]
+}

web/app/components/workflow/hooks/use-workflow-vibe.tsx

@@ -4,6 +4,7 @@ import type { ToolDefaultValue } from '../block-selector/types'
 import type { FlowGraph } from '../store/workflow/vibe-workflow-slice'
 import type { Edge, Node, ToolWithProvider } from '../types'
 import type { Tool } from '@/app/components/tools/types'
+import type { BackendEdgeSpec, BackendNodeSpec } from '@/service/debug'
 import type { Model } from '@/types/app'
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
 import { useTranslation } from 'react-i18next'
@@ -38,10 +39,12 @@ import {
   getNodeCustomTypeByNodeDataType,
   getNodesConnectedSourceOrTargetHandleIdsMap,
 } from '../utils'
+import { initialNodes as initializeNodeData } from '../utils/workflow-init'
 import { useNodesMetaData } from './use-nodes-meta-data'
 import { useNodesSyncDraft } from './use-nodes-sync-draft'
 import { useNodesReadOnly } from './use-workflow'
 import { useWorkflowHistory, WorkflowHistoryEvent } from './use-workflow-history'
+import { correctFieldName, NODE_TYPE_ALIASES } from './use-workflow-vibe-config'
 
 type VibeCommandDetail = {
   dsl?: string
@@ -100,6 +103,79 @@ const normalizeProviderIcon = (icon?: ToolWithProvider['icon']) => {
   return icon
 }
 
+/**
+ * Replace variable references in node data using the nodeIdMap.
+ * Handles:
+ * - String templates: {{#old_id.field#}} → {{#new_id.field#}}
+ * - Value selectors: ["old_id", "field"] → ["new_id", "field"]
+ * - Mixed content objects: {type: "mixed", value: "..."} → normalized to string
+ * - Field name correction based on node type
+ */
+export const replaceVariableReferences = (
+  data: unknown,
+  nodeIdMap: Map<string, Node>,
+  parentKey?: string,
+): unknown => {
+  if (typeof data === 'string') {
+    // Replace {{#old_id.field#}} patterns and correct field names
+    return data.replace(/\{\{#([^.#]+)\.([^#]+)#\}\}/g, (match, oldId, field) => {
+      const newNode = nodeIdMap.get(oldId)
+      if (newNode) {
+        const nodeType = newNode.data?.type as string || ''
+        const correctedField = correctFieldName(field, nodeType)
+        return `{{#${newNode.id}.${correctedField}#}}`
+      }
+      return match // Keep original if no mapping found
+    })
+  }
+
+  if (Array.isArray(data)) {
+    // Check if this is a value_selector array: ["node_id", "field", ...]
+    if (data.length >= 2 && typeof data[0] === 'string' && typeof data[1] === 'string') {
+      const potentialNodeId = data[0]
+      const newNode = nodeIdMap.get(potentialNodeId)
+      // #region agent log
+      if (!newNode && !['sys', 'env', 'conversation'].includes(potentialNodeId)) {
+        console.warn(`[VIBE DEBUG] replaceVariableReferences: No mapping for "${potentialNodeId}" in selector [${data.join(', ')}]`)
+      }
+      // #endregion
+      if (newNode) {
+        const nodeType = newNode.data?.type as string || ''
+        const correctedField = correctFieldName(data[1], nodeType)
+        // Replace the node ID and correct field name in value_selector
+        return [newNode.id, correctedField, ...data.slice(2)]
+      }
+    }
+    // Recursively process array elements
+    return data.map(item => replaceVariableReferences(item, nodeIdMap))
+  }
+
+  if (data !== null && typeof data === 'object') {
+    const obj = data as Record<string, unknown>
+
+    // Handle "mixed content" objects like {type: "mixed", value: "{{#...#}}"}
+    // These should be normalized to plain strings for fields like 'url'
+    if (obj.type === 'mixed' && typeof obj.value === 'string') {
+      const processedValue = replaceVariableReferences(obj.value, nodeIdMap) as string
+      // For certain fields (url, headers, params), return just the string value
+      if (parentKey && ['url', 'headers', 'params'].includes(parentKey)) {
+        return processedValue
+      }
+      // Otherwise keep the object structure but update the value
+      return { ...obj, value: processedValue }
+    }
+
+    // Recursively process object properties
+    const result: Record<string, unknown> = {}
+    for (const [key, value] of Object.entries(obj)) {
+      result[key] = replaceVariableReferences(value, nodeIdMap, key)
+    }
+    return result
+  }
+
+  return data // Return primitives as-is
+}
+
 const parseNodeLabel = (label: string) => {
   const tokens = label.split('|').map(token => token.trim()).filter(Boolean)
   const info: Record<string, string> = {}
@@ -111,8 +187,17 @@ const parseNodeLabel = (label: string) => {
     info[rawKey.trim().toLowerCase()] = rest.join('=').trim()
   })
 
+  // Fallback: if no type= found, try to infer from label text
   if (!info.type && tokens.length === 1 && !tokens[0].includes('=')) {
-    info.type = tokens[0]
+    const labelLower = tokens[0].toLowerCase()
+    // Check if label matches a known node type alias
+    if (NODE_TYPE_ALIASES[labelLower]) {
+      info.type = NODE_TYPE_ALIASES[labelLower]
+      info.title = tokens[0] // Use original label as title
+    }
+    else {
+      info.type = tokens[0]
+    }
   }
 
   if (!info.tool && info.tool_key)
@@ -365,6 +450,28 @@ export const useVibeFlowSessionStorage = (flowId: string) => {
   }, [flowId, versions, currentIndex])
 }
 
+const buildEdge = (
+  source: Node,
+  target: Node,
+  sourceHandle = 'source',
+  targetHandle = 'target',
+): Edge => ({
+  id: `${source.id}-${sourceHandle}-${target.id}-${targetHandle}`,
+  type: CUSTOM_EDGE,
+  source: source.id,
+  sourceHandle,
+  target: target.id,
+  targetHandle,
+  data: {
+    sourceType: source.data.type,
+    targetType: target.data.type,
+    isInIteration: false,
+    isInLoop: false,
+    _connectedNodeIsSelected: false,
+  },
+  zIndex: 0,
+})
+
 export const useWorkflowVibe = () => {
   const { t } = useTranslation()
   const store = useStoreApi()
@@ -376,7 +483,7 @@ export const useWorkflowVibe = () => {
   const { handleSyncWorkflowDraft } = useNodesSyncDraft()
   const { getNodesReadOnly } = useNodesReadOnly()
   const { saveStateToHistory } = useWorkflowHistory()
-  const { defaultModel } = useModelListAndDefaultModelAndCurrentProviderAndModel(ModelTypeEnum.textGeneration)
+  const { defaultModel, modelList } = useModelListAndDefaultModelAndCurrentProviderAndModel(ModelTypeEnum.textGeneration)
 
   const { data: buildInTools } = useAllBuiltInTools()
   const { data: customTools } = useAllCustomTools()
@@ -494,14 +601,24 @@ export const useWorkflowVibe = () => {
   const toolLookup = useMemo(() => {
     const map = new Map<string, ToolDefaultValue>()
     toolOptions.forEach((tool) => {
+      // Primary key: provider_id/tool_name (e.g., "google/google_search")
       const primaryKey = normalizeKey(`${tool.provider_id}/${tool.tool_name}`)
       map.set(primaryKey, tool)
 
+      // Fallback 1: provider_name/tool_name (e.g., "Google/google_search")
       const providerNameKey = normalizeKey(`${tool.provider_name}/${tool.tool_name}`)
       map.set(providerNameKey, tool)
 
+      // Fallback 2: tool_label (display name)
       const labelKey = normalizeKey(tool.tool_label)
       map.set(labelKey, tool)
+
+      // Fallback 3: tool_name alone (for partial matching when model omits provider)
+      const toolNameKey = normalizeKey(tool.tool_name)
+      if (!map.has(toolNameKey)) {
+        // Only set if not already taken (avoid collisions between providers)
+        map.set(toolNameKey, tool)
+      }
     })
     return map
   }, [toolOptions])
@@ -520,6 +637,423 @@ export const useWorkflowVibe = () => {
     return map
   }, [nodesMetaDataMap])
 
+  const createGraphFromBackendNodes = useCallback(async (
+    backendNodes: BackendNodeSpec[],
+    backendEdges: BackendEdgeSpec[],
+  ): Promise<FlowGraph> => {
+    const { getNodes } = store.getState()
+    const nodes = getNodes()
+
+    if (!nodesMetaDataMap) {
+      Toast.notify({ type: 'error', message: t('workflow.vibe.nodesUnavailable') })
+      return { nodes: [], edges: [] }
+    }
+
+    const existingStartNode = nodes.find(node => node.data.type === BlockEnum.Start)
+    const newNodes: Node[] = []
+    const nodeIdMap = new Map<string, Node>()
+
+    for (const nodeSpec of backendNodes) {
+      // Map string type to BlockEnum
+      const typeKey = normalizeKey(nodeSpec.type)
+      const nodeType = nodeTypeLookup.get(typeKey)
+      if (!nodeType) {
+        // Skip unknown node types
+        continue
+      }
+
+      if (nodeType === BlockEnum.Start && existingStartNode) {
+        // Merge backend variables into existing Start node
+        const backendVariables = (nodeSpec.config?.variables as Array<Record<string, unknown>>) || []
+        if (backendVariables.length > 0) {
+          const existingVariables = (existingStartNode.data.variables as Array<Record<string, unknown>>) || []
+          // Add new variables that don't already exist
+          for (const backendVar of backendVariables) {
+            const varName = backendVar.variable as string
+            const exists = existingVariables.some(v => v.variable === varName)
+            if (!exists) {
+              existingVariables.push(backendVar)
+            }
+          }
+          // Note: we don't mutate existingStartNode directly here for the return value,
+          // but we should probably include it in the graph if we want it to be part of the preview?
+          // Actually, existingStartNode is already in 'nodes'.
+          // The preview usually shows ONLY new nodes + maybe start node?
+          // User's code applied changes to existingStartNode directly.
+          // For preview, we might want to clone it.
+          // For now, we just map it.
+        }
+
+        nodeIdMap.set(nodeSpec.id, existingStartNode)
+        continue
+      }
+
+      const nodeDefault = nodesMetaDataMap[nodeType]
+      if (!nodeDefault)
+        continue
+
+      const defaultValue = nodeDefault.defaultValue || {}
+      const title = nodeSpec.title?.trim() || nodeDefault.metaData.title || defaultValue.title || nodeSpec.type
+
+      // For tool nodes, try to get tool default value from config
+      let toolDefaultValue: ToolDefaultValue | undefined
+      if (nodeType === BlockEnum.Tool && nodeSpec.config) {
+        const toolName = nodeSpec.config.tool_name as string | undefined
+        const providerId = nodeSpec.config.provider_id as string | undefined
+        if (toolName && providerId) {
+          const toolKey = normalizeKey(`${providerId}/${toolName}`)
+          toolDefaultValue = toolLookup.get(toolKey) || toolLookup.get(normalizeKey(toolName))
+        }
+      }
+
+      const desc = (toolDefaultValue?.tool_description || (defaultValue as { desc?: string }).desc || '') as string
+
+      // Merge backend config into node data
+      // Backend provides: { url: "{{#start.url#}}", method: "GET", ... }
+      const backendConfig = nodeSpec.config || {}
+
+      // Deep merge for nested objects (e.g., body, authorization) to preserve required fields
+      const mergedConfig: Record<string, unknown> = { ...backendConfig }
+      const defaultValueRecord = defaultValue as Record<string, unknown>
+
+      // For http-request nodes, ensure body has all required fields
+      if (nodeType === BlockEnum.HttpRequest) {
+        const defaultBody = defaultValueRecord.body as Record<string, unknown> | undefined
+        const backendBody = backendConfig.body as Record<string, unknown> | undefined
+        if (defaultBody || backendBody) {
+          mergedConfig.body = {
+            type: 'none',
+            data: [],
+            ...(defaultBody || {}),
+            ...(backendBody || {}),
+          }
+          // Ensure data is always an array
+          if (!Array.isArray((mergedConfig.body as Record<string, unknown>).data)) {
+            (mergedConfig.body as Record<string, unknown>).data = []
+          }
+        }
+
+        // Ensure authorization has type
+        const defaultAuth = defaultValueRecord.authorization as Record<string, unknown> | undefined
+        const backendAuth = backendConfig.authorization as Record<string, unknown> | undefined
+        if (defaultAuth || backendAuth) {
+          mergedConfig.authorization = {
+            type: 'no-auth',
+            ...(defaultAuth || {}),
+            ...(backendAuth || {}),
+          }
+        }
+      }
+
+      // For End nodes, ensure outputs have value_selector format
+      // New format (preferred): {"outputs": [{"variable": "name", "value_selector": ["nodeId", "field"]}]}
+      // Legacy format (fallback): {"outputs": [{"variable": "name", "value": "{{#nodeId.field#}}"}]}
+      if (nodeType === BlockEnum.End && backendConfig.outputs) {
+        const outputs = backendConfig.outputs as Array<{ variable?: string, value?: string, value_selector?: string[] }>
+        mergedConfig.outputs = outputs.map((output) => {
+          // Preferred: value_selector array format (new LLM output format)
+          if (output.value_selector && Array.isArray(output.value_selector)) {
+            return output
+          }
+          // Parse value like "{{#nodeId.field#}}" into ["nodeId", "field"]
+          if (output.value) {
+            const match = output.value.match(/\{\{#([^.]+)\.([^#]+)#\}\}/)
+            if (match) {
+              return {
+                variable: output.variable,
+                value_selector: [match[1], match[2]],
+              }
+            }
+          }
+          // Fallback: return with empty value_selector to prevent crash
+          return {
+            variable: output.variable || 'output',
+            value_selector: [],
+          }
+        })
+      }
+
+      // For Parameter Extractor nodes, ensure each parameter has a 'required' field
+      // Backend may omit this field, but Dify's Pydantic model requires it
+      if (nodeType === BlockEnum.ParameterExtractor) {
+        // Fix: If backend returns query as null, use default empty array instead
+        if (backendConfig.query === null || backendConfig.query === undefined) {
+          mergedConfig.query = []
+        }
+        if (backendConfig.parameters) {
+          const parameters = backendConfig.parameters as Array<{ name?: string, type?: string, description?: string, required?: boolean }>
+          mergedConfig.parameters = parameters.map(param => ({
+            ...param,
+            required: param.required ?? true, // Default to required if not specified
+          }))
+        }
+      }
+
+      // For Question Classifier nodes, ensure query_variable_selector is not null
+      // Backend may return null, but Dify's Pydantic model requires an array
+      // Note: question-classifier uses 'query' field in backend config, but 'query_variable_selector' in frontend
+      if (nodeType === BlockEnum.QuestionClassifier) {
+        // Fix: If backend returns query as null, use default empty array instead
+        const backendQuery = backendConfig.query
+        if (backendQuery === null || backendQuery === undefined) {
+          mergedConfig.query_variable_selector = []
+        }
+        else if (Array.isArray(backendQuery)) {
+          // Map backend 'query' field to frontend 'query_variable_selector' field
+          mergedConfig.query_variable_selector = backendQuery
+          // Remove the 'query' field to avoid confusion
+          delete mergedConfig.query
+        }
+      }
+
+      // For Variable Aggregator nodes, ensure variables format is correct
+      // Backend expects list[list[str]], but LLM may generate dict format
+      if (nodeType === BlockEnum.VariableAggregator && backendConfig.variables) {
+        const backendVariables = backendConfig.variables as Array<any>
+        const repairedVariables: string[][] = []
+        let repaired = false
+
+        for (const varItem of backendVariables) {
+          if (Array.isArray(varItem)) {
+            // Already in correct format
+            repairedVariables.push(varItem)
+          }
+          else if (typeof varItem === 'object' && varItem !== null) {
+            // Convert dict format to array format
+            const valueSelector = varItem.value_selector || varItem.selector || varItem.path
+            if (Array.isArray(valueSelector) && valueSelector.length > 0) {
+              repairedVariables.push(valueSelector)
+              repaired = true
+            }
+            else {
+              // Try to extract from name field - LLM may generate {"name": "node_id.field"}
+              const name = varItem.name
+              if (typeof name === 'string' && name.includes('.')) {
+                const parts = name.split('.', 2)
+                if (parts.length === 2) {
+                  repairedVariables.push([parts[0], parts[1]])
+                  repaired = true
+                }
+              }
+              // If still can't parse, skip this variable (don't add empty array)
+            }
+          }
+        }
+
+        if (repaired || repairedVariables.length !== backendVariables.length) {
+          mergedConfig.variables = repairedVariables
+        }
+      }
+
+      // For any node with model config, validate against user's available models
+      // Only fallback to default if backend generated an invalid/unavailable model
+      // This prevents "Model not exist" errors while trusting valid backend model selections
+      if (backendConfig.model) {
+        const backendModel = backendConfig.model as { provider?: string, name?: string, mode?: string }
+        const backendProvider = backendModel.provider
+        const backendName = backendModel.name
+
+        // Check if backend model exists in user's available models
+        const isValidModel = backendProvider && backendName && modelList?.some(provider =>
+          provider.provider === backendProvider
+          && provider.models.some(m => m.model === backendName),
+        )
+
+        if (!isValidModel) {
+          // Backend model is invalid or not available - fallback to user's default
+          const fallbackModel = modelList?.[0]?.models?.[0]
+          const modelProvider = defaultModel?.provider?.provider || modelList?.[0]?.provider
+          const modelName = defaultModel?.model || fallbackModel?.model
+
+          if (modelProvider && modelName) {
+            mergedConfig.model = {
+              provider: modelProvider,
+              name: modelName,
+              mode: 'chat',
+            }
+          }
+        }
+        // else: backend model is valid, keep it as-is
+      }
+
+      const data = {
+        ...(defaultValue as Record<string, unknown>),
+        title,
+        desc,
+        type: nodeType,
+        selected: false,
+        ...(toolDefaultValue || {}),
+        // Apply backend-generated config (url, method, headers, etc.)
+        ...mergedConfig,
+      }
+
+      const newNode = generateNewNode({
+        id: uuid4(),
+        type: getNodeCustomTypeByNodeDataType(nodeType),
+        data,
+        position: nodeSpec.position || { x: 0, y: 0 },
+      }).newNode
+
+      newNodes.push(newNode)
+      nodeIdMap.set(nodeSpec.id, newNode)
+    }
+
+    // Replace variable references in all node configs using the nodeIdMap
+    // This converts {{#old_id.field#}} to {{#new_uuid.field#}}
+
+    for (const node of newNodes) {
+      node.data = replaceVariableReferences(node.data, nodeIdMap) as typeof node.data
+    }
+
+    // Use Dify's standard node initialization to handle all node types generically
+    // This sets up _targetBranches for question-classifier/if-else, _children for iteration/loop, etc.
+    const initializedNodes = initializeNodeData(newNodes, [])
+
+    // Update newNodes with initialized data
+    newNodes.splice(0, newNodes.length, ...initializedNodes)
+
+    if (!newNodes.length) {
+      Toast.notify({ type: 'error', message: t('workflow.vibe.invalidFlowchart') })
+      return { nodes: [], edges: [] }
+    }
+
+    const newEdges: Edge[] = []
+    for (const edgeSpec of backendEdges) {
+      const sourceNode = nodeIdMap.get(edgeSpec.source)
+      const targetNode = nodeIdMap.get(edgeSpec.target)
+
+      if (!sourceNode || !targetNode) {
+        console.warn(`[VIBE] Edge skipped: source=${edgeSpec.source} (found=${!!sourceNode}), target=${edgeSpec.target} (found=${!!targetNode})`)
+        continue
+      }
+
+      let sourceHandle = edgeSpec.sourceHandle || 'source'
+      // Handle IfElse branch handles
+      if (sourceNode.data.type === BlockEnum.IfElse && !edgeSpec.sourceHandle) {
+        sourceHandle = 'source'
+      }
+
+      newEdges.push(buildEdge(sourceNode, targetNode, sourceHandle, edgeSpec.targetHandle || 'target'))
+    }
+
+    // Layout nodes
+    const bounds = nodes.reduce(
+      (acc, node) => {
+        const width = node.width ?? NODE_WIDTH
+        acc.maxX = Math.max(acc.maxX, node.position.x + width)
+        acc.minY = Math.min(acc.minY, node.position.y)
+        return acc
+      },
+      { maxX: 0, minY: 0 },
+    )
+
+    const baseX = nodes.length ? bounds.maxX + NODE_WIDTH_X_OFFSET : 0
+    const baseY = Number.isFinite(bounds.minY) ? bounds.minY : 0
+    const branchOffset = Math.max(120, NODE_WIDTH_X_OFFSET / 2)
+
+    const layoutNodeIds = new Set(newNodes.map(node => node.id))
+    const layoutEdges = newEdges.filter(edge =>
+      layoutNodeIds.has(edge.source) && layoutNodeIds.has(edge.target),
+    )
+
+    try {
+      const layout = await getLayoutByDagre(newNodes, layoutEdges)
+      const layoutedNodes = newNodes.map((node) => {
+        const info = layout.nodes.get(node.id)
+        if (!info)
+          return node
+        return {
+          ...node,
+          position: {
+            x: baseX + info.x,
+            y: baseY + info.y,
+          },
+        }
+      })
+      newNodes.splice(0, newNodes.length, ...layoutedNodes)
+    }
+    catch {
+      newNodes.forEach((node, index) => {
+        const row = Math.floor(index / 4)
+        const col = index % 4
+        node.position = {
+          x: baseX + col * NODE_WIDTH_X_OFFSET,
+          y: baseY + row * branchOffset,
+        }
+      })
+    }
+
+    return {
+      nodes: newNodes,
+      edges: newEdges,
+    }
+  }, [
+    defaultModel,
+    modelList,
+    nodeTypeLookup,
+    nodesMetaDataMap,
+    store,
+    t,
+    toolLookup,
+  ])
+
+  // Apply backend-provided nodes directly (bypasses mermaid parsing)
+  const applyBackendNodesToWorkflow = useCallback(async (
+    backendNodes: BackendNodeSpec[],
+    backendEdges: BackendEdgeSpec[],
+  ) => {
+    const { getNodes, setNodes, edges, setEdges } = store.getState()
+    const nodes = getNodes()
+    const {
+      setShowVibePanel,
+    } = workflowStore.getState()
+
+    const { nodes: newNodes, edges: newEdges } = await createGraphFromBackendNodes(backendNodes, backendEdges)
+
+    if (newNodes.length === 0) {
+      setShowVibePanel(false)
+      return
+    }
+
+    const allNodes = [...nodes, ...newNodes]
+    const nodesConnectedMap = getNodesConnectedSourceOrTargetHandleIdsMap(
+      newEdges.map(edge => ({ type: 'add', edge })),
+      allNodes,
+    )
+
+    const updatedNodes = allNodes.map((node) => {
+      const connected = nodesConnectedMap[node.id]
+      if (!connected)
+        return node
+
+      return {
+        ...node,
+        data: {
+          ...node.data,
+          ...connected,
+          _connectedSourceHandleIds: dedupeHandles(connected._connectedSourceHandleIds),
+          _connectedTargetHandleIds: dedupeHandles(connected._connectedTargetHandleIds),
+        },
+      }
+    })
+
+    setNodes(updatedNodes)
+    setEdges([...edges, ...newEdges])
+    saveStateToHistory(WorkflowHistoryEvent.NodeAdd, { nodeId: newNodes[0].id })
+    handleSyncWorkflowDraft()
+
+    workflowStore.setState(state => ({
+      ...state,
+      showVibePanel: false,
+      vibePanelMermaidCode: '',
+    }))
+  }, [
+    createGraphFromBackendNodes,
+    handleSyncWorkflowDraft,
+    saveStateToHistory,
+    store,
+  ])
+
   const flowchartToWorkflowGraph = useCallback(async (mermaidCode: string): Promise<FlowGraph> => {
     const { getNodes } = store.getState()
     const nodes = getNodes()
@@ -603,28 +1137,6 @@ export const useWorkflowVibe = () => {
       return emptyGraph
     }
 
-    const buildEdge = (
-      source: Node,
-      target: Node,
-      sourceHandle = 'source',
-      targetHandle = 'target',
-    ): Edge => ({
-      id: `${source.id}-${sourceHandle}-${target.id}-${targetHandle}`,
-      type: CUSTOM_EDGE,
-      source: source.id,
-      sourceHandle,
-      target: target.id,
-      targetHandle,
-      data: {
-        sourceType: source.data.type,
-        targetType: target.data.type,
-        isInIteration: false,
-        isInLoop: false,
-        _connectedNodeIsSelected: false,
-      },
-      zIndex: 0,
-    })
-
     const newEdges: Edge[] = []
     for (const edgeSpec of parseResultToUse.edges) {
       const sourceNode = nodeIdMap.get(edgeSpec.sourceId)
@@ -717,7 +1229,7 @@ export const useWorkflowVibe = () => {
       nodes: updatedNodes,
       edges: newEdges,
     }
-  }, [nodeTypeLookup, toolLookup])
+  }, [nodeTypeLookup, nodesMetaDataMap, store, t, toolLookup])
 
   const applyFlowchartToWorkflow = useCallback(() => {
     const currentFlowGraph = workflowStore.getState().currentVibeFlow
@@ -743,8 +1255,6 @@ export const useWorkflowVibe = () => {
     }))
   }, [
     handleSyncWorkflowDraft,
-    nodeTypeLookup,
-    nodesMetaDataMap,
     saveStateToHistory,
     store,
     t,
@@ -752,7 +1262,11 @@ export const useWorkflowVibe = () => {
     workflowStore,
   ])
 
-  const handleVibeCommand = useCallback(async (dsl?: string, skipPanelPreview = false) => {
+  const handleVibeCommand = useCallback(async (
+    dsl?: string,
+    skipPanelPreview = false,
+    regenerateMode = false,
+  ) => {
     if (getNodesReadOnly()) {
       Toast.notify({ type: 'error', message: t('workflow.vibe.readOnly') })
       return
@@ -788,6 +1302,9 @@ export const useWorkflowVibe = () => {
       isVibeGenerating: true,
       vibePanelMermaidCode: '',
       vibePanelInstruction: trimmed,
+      vibePanelIntent: '',
+      vibePanelMessage: '',
+      vibePanelSuggestions: [],
     }))
 
     try {
@@ -795,13 +1312,12 @@ export const useWorkflowVibe = () => {
       const nodes = getNodes()
       const {
         setIsVibeGenerating,
+        vibePanelBackendNodes,
+        vibePanelBackendEdges,
       } = workflowStore.getState()
 
-      const existingNodesPayload = nodes.map(node => ({
-        id: node.id,
-        type: node.data.type,
-        title: node.data.title || '',
-      }))
+      // Refinement mode removed - always start fresh
+      const existingNodesPayload: Array<{ id: string; type: string; title: string }> = []
 
       const toolsPayload = toolOptions.map(tool => ({
         provider_id: tool.provider_id,
@@ -810,27 +1326,106 @@ export const useWorkflowVibe = () => {
         tool_name: tool.tool_name,
         tool_label: tool.tool_label,
         tool_key: `${tool.provider_id}/${tool.tool_name}`,
+        tool_description: tool.tool_description,
+        is_team_authorization: tool.is_team_authorization,
+        // Include parameter schemas so backend can inform model how to use tools
+        parameters: tool.paramSchemas,
+        output_schema: tool.output_schema,
       }))
 
+      // Refinement mode removed - always use empty edges
+      const existingEdgesPayload: Array<{ source: string; target: string; sourceHandle: string }> = []
+
       const availableNodesPayload = availableNodesList.map(node => ({
         type: node.type,
         title: node.title,
         description: node.description,
       }))
 
-      let mermaidCode = trimmed
+      let mermaidCode = ''
+      let backendNodes: BackendNodeSpec[] | undefined
+      let backendEdges: BackendEdgeSpec[] | undefined
+
       if (!isMermaidFlowchart(trimmed)) {
-        const { error, flowchart } = await generateFlowchart({
+        // Build previous workflow context if regenerating
+        const { vibePanelBackendNodes, vibePanelBackendEdges, vibePanelLastWarnings } = workflowStore.getState()
+        const previousWorkflow = regenerateMode && vibePanelBackendNodes && vibePanelBackendNodes.length > 0
+          ? {
+            nodes: vibePanelBackendNodes,
+            edges: vibePanelBackendEdges || [],
+            warnings: vibePanelLastWarnings || [],
+          }
+          : undefined
+
+        // Map language code to human-readable language name for LLM
+        const languageNameMap: Record<string, string> = {
+          en_US: 'English',
+          zh_Hans: 'Chinese',
+          zh_Hant: 'Traditional Chinese',
+          ja_JP: 'Japanese',
+          ko_KR: 'Korean',
+          pt_BR: 'Portuguese',
+          es_ES: 'Spanish',
+          fr_FR: 'French',
+          de_DE: 'German',
+          it_IT: 'Italian',
+          ru_RU: 'Russian',
+          uk_UA: 'Ukrainian',
+          vi_VN: 'Vietnamese',
+          pl_PL: 'Polish',
+          ro_RO: 'Romanian',
+          tr_TR: 'Turkish',
+          fa_IR: 'Persian',
+          hi_IN: 'Hindi',
+        }
+        const preferredLanguage = languageNameMap[language] || 'English'
+
+        // Extract available models from user's configured model providers
+        const availableModelsPayload = modelList?.flatMap(provider =>
+          provider.models.map(model => ({
+            provider: provider.provider,
+            model: model.model,
+          })),
+        ) || []
+
+        const requestPayload = {
           instruction: trimmed,
           model_config: latestModelConfig,
           available_nodes: availableNodesPayload,
           existing_nodes: existingNodesPayload,
+          existing_edges: existingEdgesPayload,
           available_tools: toolsPayload,
-        })
+          selected_node_ids: [],
+          previous_workflow: previousWorkflow,
+          regenerate_mode: regenerateMode,
+          language: preferredLanguage,
+          available_models: availableModelsPayload,
+        }
+
+        const response = await generateFlowchart(requestPayload)
+
+        const { error, flowchart, nodes, edges, intent, message, warnings, suggestions } = response
 
         if (error) {
           Toast.notify({ type: 'error', message: error })
-          setIsVibeGenerating(false)
+          workflowStore.setState(state => ({
+            ...state,
+            vibePanelMessage: `${error} ${t('workflow.vibe.regenerateReminder')}`,
+            isVibeGenerating: false,
+          }))
+          return
+        }
+
+        // Handle off_topic intent - show rejection message and suggestions
+        if (intent === 'off_topic') {
+          workflowStore.setState(state => ({
+            ...state,
+            vibePanelMermaidCode: '',
+            vibePanelMessage: message || t('workflow.vibe.offTopicDefault'),
+            vibePanelSuggestions: suggestions || [],
+            vibePanelIntent: 'off_topic',
+            isVibeGenerating: false,
+          }))
           return
         }
 
@@ -840,41 +1435,119 @@ export const useWorkflowVibe = () => {
           return
         }
 
+        // Show warnings if any (includes tool sanitization warnings)
+        const responseWarnings = warnings || []
+        if (responseWarnings.length > 0) {
+          responseWarnings.forEach((warning) => {
+            Toast.notify({ type: 'warning', message: warning })
+          })
+        }
+
         mermaidCode = flowchart
+        // Store backend nodes/edges for direct use (bypasses mermaid re-parsing)
+        backendNodes = nodes
+        backendEdges = edges
+        // Store warnings for regeneration context
+        workflowStore.setState(state => ({
+          ...state,
+          vibePanelLastWarnings: responseWarnings,
+        }))
+
+        workflowStore.setState(state => ({
+          ...state,
+          vibePanelMermaidCode: mermaidCode,
+          vibePanelBackendNodes: backendNodes,
+          vibePanelBackendEdges: backendEdges,
+          vibePanelMessage: '',
+          vibePanelSuggestions: [],
+          vibePanelIntent: 'generate',
+          isVibeGenerating: false,
+        }))
       }
 
+      setIsVibeGenerating(false)
+
+      // Add version for preview
+      if (backendNodes && backendNodes.length > 0 && backendEdges) {
+        const graph = await createGraphFromBackendNodes(backendNodes, backendEdges)
+        workflowStore.getState().addVibeFlowVersion(graph)
+      }
+      else if (mermaidCode) {
+        const graph = await flowchartToWorkflowGraph(mermaidCode)
+        workflowStore.getState().addVibeFlowVersion(graph)
+      }
+
+      if (skipPanelPreview) {
+        // Prefer backend nodes (already sanitized) over mermaid re-parsing
+        if (backendNodes && backendNodes.length > 0 && backendEdges) {
+          console.log('[VIBE] Applying backend nodes directly to workflow')
+          console.log('[VIBE] Backend nodes:', backendNodes.length)
+          console.log('[VIBE] Backend edges:', backendEdges.length)
+          await applyBackendNodesToWorkflow(backendNodes, backendEdges)
+          console.log('[VIBE] Backend nodes applied successfully')
+        }
+        else {
+          console.log('[VIBE] Applying mermaid flowchart to workflow')
+          await applyFlowchartToWorkflow()
+          console.log('[VIBE] Mermaid flowchart applied successfully')
+        }
+      }
+    }
+    catch (error: unknown) {
+      // Handle API errors (e.g., network errors, server errors)
+      const { setIsVibeGenerating } = workflowStore.getState()
+      setIsVibeGenerating(false)
+
+      // Extract error message from Response object or Error
+      let errorMessage = t('workflow.vibe.generateError')
+      if (error instanceof Response) {
+        try {
+          const errorData = await error.json()
+          errorMessage = errorData?.message || errorMessage
+        }
+        catch {
+          // If we can't parse the response, use the default error message
+        }
+      }
+      else if (error instanceof Error) {
+        errorMessage = error.message || errorMessage
+      }
+
+      Toast.notify({ type: 'error', message: errorMessage })
       workflowStore.setState(state => ({
         ...state,
-        vibePanelMermaidCode: mermaidCode,
+        vibePanelMessage: `${errorMessage} ${t('workflow.vibe.regenerateReminder')}`,
         isVibeGenerating: false,
       }))
-
-      const workflowGraph = await flowchartToWorkflowGraph(mermaidCode)
-      workflowStore.getState().addVibeFlowVersion(workflowGraph)
-
-      if (skipPanelPreview)
-        applyFlowchartToWorkflow()
     }
     finally {
       isGeneratingRef.current = false
     }
   }, [
-    availableNodesList,
+    applyBackendNodesToWorkflow,
+    applyFlowchartToWorkflow,
+    createGraphFromBackendNodes,
+    flowchartToWorkflowGraph,
+    getLatestModelConfig,
     getNodesReadOnly,
-    handleSyncWorkflowDraft,
     nodeTypeLookup,
     nodesMetaDataMap,
-    saveStateToHistory,
     store,
     t,
-    toolLookup,
     toolOptions,
-    getLatestModelConfig,
   ])
 
-  const handleAccept = useCallback(() => {
-    applyFlowchartToWorkflow()
-  }, [applyFlowchartToWorkflow])
+  const handleAccept = useCallback(async () => {
+    // Prefer backend nodes (already sanitized) over mermaid re-parsing
+    const { vibePanelBackendNodes, vibePanelBackendEdges } = workflowStore.getState()
+    if (vibePanelBackendNodes && vibePanelBackendNodes.length > 0 && vibePanelBackendEdges) {
+      await applyBackendNodesToWorkflow(vibePanelBackendNodes, vibePanelBackendEdges)
+    }
+    else {
+      // Use applyFlowchartToWorkflow which uses currentFlowGraph (populated by addVersion)
+      applyFlowchartToWorkflow()
+    }
+  }, [applyBackendNodesToWorkflow, applyFlowchartToWorkflow])
 
   useEffect(() => {
     const handler = (event: CustomEvent<VibeCommandDetail>) => {

web/app/components/workflow/nodes/_base/components/file-upload-setting.tsx

@@ -33,9 +33,9 @@ const FileUploadSetting: FC<Props> = ({
   const { t } = useTranslation()
 
   const {
-    allowed_file_upload_methods,
+    allowed_file_upload_methods = [],
     max_length,
-    allowed_file_types,
+    allowed_file_types = [],
     allowed_file_extensions,
   } = payload
   const { data: fileUploadConfigResponse } = useFileUploadConfig()

web/app/components/workflow/nodes/_base/components/variable/utils.ts

@@ -1390,9 +1390,9 @@ export const getNodeUsedVars = (node: Node): ValueSelector[] => {
         payload.url,
         payload.headers,
         payload.params,
-        typeof payload.body.data === 'string'
+        typeof payload.body?.data === 'string'
           ? payload.body.data
-          : payload.body.data.map(d => d.value).join(''),
+          : (payload.body?.data?.map(d => d.value).join('') ?? ''),
       ])
       break
     }

web/app/components/workflow/nodes/http/hooks/use-key-value-list.ts

@@ -5,6 +5,9 @@ import { useCallback, useEffect, useState } from 'react'
 
 const UNIQUE_ID_PREFIX = 'key-value-'
 const strToKeyValueList = (value: string) => {
+  if (typeof value !== 'string' || !value)
+    return []
+
   return value.split('\n').map((item) => {
     const [key, ...others] = item.split(':')
     return {
@@ -16,7 +19,7 @@ const strToKeyValueList = (value: string) => {
 }
 
 const useKeyValueList = (value: string, onChange: (value: string) => void, noFilter?: boolean) => {
-  const [list, doSetList] = useState<KeyValue[]>(() => value ? strToKeyValueList(value) : [])
+  const [list, doSetList] = useState<KeyValue[]>(() => typeof value === 'string' && value ? strToKeyValueList(value) : [])
   const setList = (l: KeyValue[]) => {
     doSetList(l.map((item) => {
       return {

web/app/components/workflow/nodes/if-else/components/condition-value.tsx

@@ -49,7 +49,7 @@ const ConditionValue = ({
     if (value === true || value === false)
       return value ? 'True' : 'False'
 
-    return value.replace(/\{\{#([^#]*)#\}\}/g, (a, b) => {
+    return String(value).replace(/\{\{#([^#]*)#\}\}/g, (a, b) => {
       const arr: string[] = b.split('.')
       if (isSystemVar(arr))
         return `{{${b}}}`

web/app/components/workflow/nodes/variable-assigner/components/node-group-item.tsx

@@ -127,23 +127,30 @@ const NodeGroupItem = ({
         !!item.variables.length && (
           <div className="space-y-0.5">
             {
-              item.variables.map((variable = [], index) => {
-                const isSystem = isSystemVar(variable)
+              item.variables
+                .map((variable = [], index) => {
+                  // Ensure variable is an array
+                  const safeVariable = Array.isArray(variable) ? variable : []
+                  if (!safeVariable.length)
+                    return null
 
-                const node = isSystem ? nodes.find(node => node.data.type === BlockEnum.Start) : nodes.find(node => node.id === variable[0])
-                const varName = isSystem ? `sys.${variable[variable.length - 1]}` : variable.slice(1).join('.')
-                const isException = isExceptionVariable(varName, node?.data.type)
+                  const isSystem = isSystemVar(safeVariable)
 
-                return (
-                  <VariableLabelInNode
-                    key={index}
-                    variables={variable}
-                    nodeType={node?.data.type}
-                    nodeTitle={node?.data.title}
-                    isExceptionVariable={isException}
-                  />
-                )
-              })
+                  const node = isSystem ? nodes.find(node => node.data.type === BlockEnum.Start) : nodes.find(node => node.id === safeVariable[0])
+                  const varName = isSystem ? `sys.${safeVariable[safeVariable.length - 1]}` : safeVariable.slice(1).join('.')
+                  const isException = isExceptionVariable(varName, node?.data.type)
+
+                  return (
+                    <VariableLabelInNode
+                      key={index}
+                      variables={safeVariable}
+                      nodeType={node?.data.type}
+                      nodeTitle={node?.data.title}
+                      isExceptionVariable={isException}
+                    />
+                  )
+                })
+                .filter(Boolean)
             }
           </div>
         )

web/app/components/workflow/panel/vibe-panel/index.tsx

@@ -3,7 +3,7 @@
 import type { FC } from 'react'
 import type { FormValue } from '@/app/components/header/account-setting/model-provider-page/declarations'
 import type { CompletionParams, Model } from '@/types/app'
-import { RiClipboardLine } from '@remixicon/react'
+import { RiClipboardLine, RiInformation2Line } from '@remixicon/react'
 import copy from 'copy-to-clipboard'
 import { useCallback, useEffect, useState } from 'react'
 import { useTranslation } from 'react-i18next'
@@ -22,13 +22,18 @@ import { ModelModeType } from '@/types/app'
 import { VIBE_APPLY_EVENT, VIBE_COMMAND_EVENT } from '../../constants'
 import { useStore, useWorkflowStore } from '../../store'
 import WorkflowPreview from '../../workflow-preview'
+import { useMemo } from 'react'
 
 const VibePanel: FC = () => {
   const { t } = useTranslation()
   const workflowStore = useWorkflowStore()
   const showVibePanel = useStore(s => s.showVibePanel)
+  const setShowVibePanel = useStore(s => s.setShowVibePanel)
   const isVibeGenerating = useStore(s => s.isVibeGenerating)
+  const setIsVibeGenerating = useStore(s => s.setIsVibeGenerating)
   const vibePanelInstruction = useStore(s => s.vibePanelInstruction)
+  const vibePanelMermaidCode = useStore(s => s.vibePanelMermaidCode)
+  const setVibePanelMermaidCode = useStore(s => s.setVibePanelMermaidCode)
   const currentFlowGraph = useStore(s => s.currentVibeFlow)
   const versions = useStore(s => s.vibeFlowVersions)
   const currentVersionIndex = useStore(s => s.vibeFlowCurrentIndex)
@@ -36,6 +41,14 @@ const VibePanel: FC = () => {
   const vibePanelPreviewNodes = currentFlowGraph?.nodes || []
   const vibePanelPreviewEdges = currentFlowGraph?.edges || []
 
+  const setVibePanelInstruction = useStore(s => s.setVibePanelInstruction)
+  const vibePanelIntent = useStore(s => s.vibePanelIntent)
+  const setVibePanelIntent = useStore(s => s.setVibePanelIntent)
+  const vibePanelMessage = useStore(s => s.vibePanelMessage)
+  const setVibePanelMessage = useStore(s => s.setVibePanelMessage)
+  const vibePanelSuggestions = useStore(s => s.vibePanelSuggestions)
+  const setVibePanelSuggestions = useStore(s => s.setVibePanelSuggestions)
+
   const localModel = localStorage.getItem('auto-gen-model')
     ? JSON.parse(localStorage.getItem('auto-gen-model') as string) as Model
     : null
@@ -93,13 +106,13 @@ const VibePanel: FC = () => {
   }, [workflowStore])
 
   const handleClose = useCallback(() => {
-    workflowStore.setState(state => ({
-      ...state,
-      showVibePanel: false,
-      vibePanelMermaidCode: '',
-      isVibeGenerating: false,
-    }))
-  }, [workflowStore])
+    setShowVibePanel(false)
+    setVibePanelMermaidCode('')
+    setIsVibeGenerating(false)
+    setVibePanelIntent('')
+    setVibePanelMessage('')
+    setVibePanelSuggestions([])
+  }, [setShowVibePanel, setVibePanelMermaidCode, setIsVibeGenerating, setVibePanelIntent, setVibePanelMessage, setVibePanelSuggestions])
 
   const handleGenerate = useCallback(() => {
     const event = new CustomEvent(VIBE_COMMAND_EVENT, {
@@ -115,16 +128,29 @@ const VibePanel: FC = () => {
   }, [handleClose])
 
   const handleCopyMermaid = useCallback(() => {
-    const { vibePanelMermaidCode } = workflowStore.getState()
     copy(vibePanelMermaidCode)
     Toast.notify({ type: 'success', message: t('common.actionMsg.copySuccessfully') })
-  }, [workflowStore, t])
+  }, [vibePanelMermaidCode, t])
+
+  const handleSuggestionClick = useCallback((suggestion: string) => {
+    setVibePanelInstruction(suggestion)
+    // Trigger generation with the suggestion
+    const event = new CustomEvent(VIBE_COMMAND_EVENT, {
+      detail: { dsl: suggestion },
+    })
+    document.dispatchEvent(event)
+  }, [setVibePanelInstruction])
 
   const handleVersionChange = useCallback((index: number) => {
     const { setVibeFlowCurrentIndex } = workflowStore.getState()
     setVibeFlowCurrentIndex(index)
   }, [workflowStore])
 
+  // Button label - always use "Generate" (refinement mode removed)
+  const generateButtonLabel = useMemo(() => {
+    return t('appDebug.generate.generate')
+  }, [t])
+
   if (!showVibePanel)
     return null
 
@@ -135,6 +161,40 @@ const VibePanel: FC = () => {
     </div>
   )
 
+  const renderOffTopic = (
+    <div className="flex h-full w-0 grow flex-col items-center justify-center bg-background-default-subtle p-6">
+      <div className="flex max-w-[400px] flex-col items-center text-center">
+        <div className="mb-4 flex h-12 w-12 items-center justify-center rounded-full bg-state-warning-hover">
+          <RiInformation2Line className="h-6 w-6 text-text-warning" />
+        </div>
+        <div className="mb-2 text-base font-semibold text-text-primary">
+          {t('workflow.vibe.offTopicTitle')}
+        </div>
+        <div className="mb-6 text-sm text-text-secondary">
+          {vibePanelMessage || t('workflow.vibe.offTopicDefault')}
+        </div>
+        {vibePanelSuggestions.length > 0 && (
+          <div className="w-full">
+            <div className="mb-3 text-xs font-medium text-text-tertiary">
+              {t('workflow.vibe.trySuggestion')}
+            </div>
+            <div className="flex flex-col gap-2">
+              {vibePanelSuggestions.map((suggestion, index) => (
+                <button
+                  key={index}
+                  onClick={() => handleSuggestionClick(suggestion)}
+                  className="w-full rounded-lg border border-divider-regular bg-components-panel-bg px-4 py-2.5 text-left text-sm text-text-secondary transition-colors hover:border-components-button-primary-border hover:bg-state-accent-hover"
+                >
+                  {suggestion}
+                </button>
+              ))}
+            </div>
+          </div>
+        )}
+      </div>
+    </div>
+  )
+
   return (
     <Modal
       isShow={showVibePanel}
@@ -180,12 +240,13 @@ const VibePanel: FC = () => {
               disabled={isVibeGenerating}
             >
               <Generator className="h-4 w-4" />
-              <span className="system-xs-semibold">{t('appDebug.generate.generate')}</span>
+              <span className="system-xs-semibold">{generateButtonLabel}</span>
             </Button>
           </div>
         </div>
 
-        {!isVibeGenerating && vibePanelPreviewNodes.length > 0 && (
+        {!isVibeGenerating && vibePanelIntent === 'off_topic' && renderOffTopic}
+        {!isVibeGenerating && vibePanelIntent !== 'off_topic' && (vibePanelPreviewNodes.length > 0 || vibePanelMermaidCode) && (
           <div className="h-full w-0 grow bg-background-default-subtle p-6 pb-0">
             <div className="flex h-full flex-col">
               <div className="mb-3 flex shrink-0 items-center justify-between">
@@ -229,7 +290,7 @@ const VibePanel: FC = () => {
           </div>
         )}
         {isVibeGenerating && renderLoading}
-        {!isVibeGenerating && vibePanelPreviewNodes.length === 0 && <ResPlaceholder />}
+        {!isVibeGenerating && vibePanelIntent !== 'off_topic' && vibePanelPreviewNodes.length === 0 && !vibePanelMermaidCode && <ResPlaceholder />}
       </div>
     </Modal>
   )

web/app/components/workflow/store/workflow/panel-slice.ts

@@ -1,5 +1,8 @@
+import type { BackendEdgeSpec, BackendNodeSpec } from '@/service/debug'
 import type { StateCreator } from 'zustand'
 
+export type VibeIntent = 'generate' | 'off_topic' | 'error' | ''
+
 export type PanelSliceShape = {
   panelWidth: number
   showFeaturesPanel: boolean
@@ -26,6 +29,24 @@ export type PanelSliceShape = {
   setInitShowLastRunTab: (initShowLastRunTab: boolean) => void
   showVibePanel: boolean
   setShowVibePanel: (showVibePanel: boolean) => void
+  vibePanelMermaidCode: string
+  setVibePanelMermaidCode: (vibePanelMermaidCode: string) => void
+  vibePanelBackendNodes?: BackendNodeSpec[]
+  setVibePanelBackendNodes: (nodes?: BackendNodeSpec[]) => void
+  vibePanelBackendEdges?: BackendEdgeSpec[]
+  setVibePanelBackendEdges: (edges?: BackendEdgeSpec[]) => void
+  isVibeGenerating: boolean
+  setIsVibeGenerating: (isVibeGenerating: boolean) => void
+  vibePanelInstruction: string
+  setVibePanelInstruction: (vibePanelInstruction: string) => void
+  vibePanelIntent: VibeIntent
+  setVibePanelIntent: (vibePanelIntent: VibeIntent) => void
+  vibePanelMessage: string
+  setVibePanelMessage: (vibePanelMessage: string) => void
+  vibePanelSuggestions: string[]
+  setVibePanelSuggestions: (vibePanelSuggestions: string[]) => void
+  vibePanelLastWarnings: string[]
+  setVibePanelLastWarnings: (vibePanelLastWarnings: string[]) => void
 }
 
 export const createPanelSlice: StateCreator<PanelSliceShape> = set => ({
@@ -48,4 +69,22 @@ export const createPanelSlice: StateCreator<PanelSliceShape> = set => ({
   setInitShowLastRunTab: initShowLastRunTab => set(() => ({ initShowLastRunTab })),
   showVibePanel: false,
   setShowVibePanel: showVibePanel => set(() => ({ showVibePanel })),
+  vibePanelMermaidCode: '',
+  setVibePanelMermaidCode: vibePanelMermaidCode => set(() => ({ vibePanelMermaidCode })),
+  vibePanelBackendNodes: undefined,
+  setVibePanelBackendNodes: vibePanelBackendNodes => set(() => ({ vibePanelBackendNodes })),
+  vibePanelBackendEdges: undefined,
+  setVibePanelBackendEdges: vibePanelBackendEdges => set(() => ({ vibePanelBackendEdges })),
+  isVibeGenerating: false,
+  setIsVibeGenerating: isVibeGenerating => set(() => ({ isVibeGenerating })),
+  vibePanelInstruction: '',
+  setVibePanelInstruction: vibePanelInstruction => set(() => ({ vibePanelInstruction })),
+  vibePanelIntent: '',
+  setVibePanelIntent: vibePanelIntent => set(() => ({ vibePanelIntent })),
+  vibePanelMessage: '',
+  setVibePanelMessage: vibePanelMessage => set(() => ({ vibePanelMessage })),
+  vibePanelSuggestions: [],
+  setVibePanelSuggestions: vibePanelSuggestions => set(() => ({ vibePanelSuggestions })),
+  vibePanelLastWarnings: [],
+  setVibePanelLastWarnings: vibePanelLastWarnings => set(() => ({ vibePanelLastWarnings })),
 })

web/app/components/workflow/utils/workflow-init.ts

@@ -113,8 +113,8 @@ export const preprocessNodesAndEdges = (nodes: Node[], edges: Edge[]) => {
     const currentNode = nodes[i] as Node<IterationNodeType | LoopNodeType>
 
     if (currentNode.data.type === BlockEnum.Iteration) {
-      if (currentNode.data.start_node_id) {
-        if (nodesMap[currentNode.data.start_node_id]?.type !== CUSTOM_ITERATION_START_NODE)
+      if (currentNode.data.start_node_id && nodesMap[currentNode.data.start_node_id]) {
+        if (nodesMap[currentNode.data.start_node_id].type !== CUSTOM_ITERATION_START_NODE)
           iterationNodesWithStartNode.push(currentNode)
       }
       else {
@@ -123,8 +123,8 @@ export const preprocessNodesAndEdges = (nodes: Node[], edges: Edge[]) => {
     }
 
     if (currentNode.data.type === BlockEnum.Loop) {
-      if (currentNode.data.start_node_id) {
-        if (nodesMap[currentNode.data.start_node_id]?.type !== CUSTOM_LOOP_START_NODE)
+      if (currentNode.data.start_node_id && nodesMap[currentNode.data.start_node_id]) {
+        if (nodesMap[currentNode.data.start_node_id].type !== CUSTOM_LOOP_START_NODE)
           loopNodesWithStartNode.push(currentNode)
       }
       else {

web/app/components/workflow/workflow-preview/components/nodes/if-else/node.tsx

@@ -65,7 +65,7 @@ const IfElseNode: FC<NodeProps<IfElseNodeType>> = (props) => {
             </div>
             <div className="space-y-0.5">
               {caseItem.conditions.map((condition, i) => (
-                <div key={condition.id} className="relative">
+                <div key={condition.id || i} className="relative">
                   {
                     checkIsConditionSet(condition)
                       ? (

web/i18n/en-US/workflow.ts

@@ -140,6 +140,11 @@ const translation = {
     regenerate: 'Regenerate',
     apply: 'Apply',
     noFlowchart: 'No flowchart provided',
+    offTopicDefault: 'I\'m the Dify workflow design assistant. I can help you create AI automation workflows, but I can\'t answer general questions. Would you like to create a workflow instead?',
+    offTopicTitle: 'Off-Topic Request',
+    trySuggestion: 'Try one of these suggestions:',
+    generateError: 'Failed to generate workflow. Please try again.',
+    regenerateReminder: 'Please verify your input and re-generate.',
   },
   publishLimit: {
     startNodeTitlePrefix: 'Upgrade to',

web/i18n/zh-Hans/workflow.ts

@@ -325,6 +325,10 @@ const translation = {
     'trigger-plugin': '插件触发器',
   },
   customWebhook: '自定义 Webhook',
+  vibe: {
+    regenerateReminder: '请检查输入并重新生成。',
+    refine: '调整',
+  },
   blocksAbout: {
     'start': '定义一个 workflow 流程启动的初始参数',
     'end': '定义一个 workflow 流程的输出和结果类型',

web/service/debug.ts

@@ -19,8 +19,45 @@ export type GenRes = {
   error?: string
 }
 
+export type ToolRecommendation = {
+  requested_capability: string
+  unconfigured_tools: Array<{
+    provider_id: string
+    tool_name: string
+    description: string
+  }>
+  configured_alternatives: Array<{
+    provider_id: string
+    tool_name: string
+    description: string
+  }>
+  recommendation: string
+}
+
+export type BackendNodeSpec = {
+  id: string
+  type: string
+  title?: string
+  config?: Record<string, any>
+  position?: { x: number; y: number }
+}
+
+export type BackendEdgeSpec = {
+  source: string
+  target: string
+  sourceHandle?: string
+  targetHandle?: string
+}
+
 export type FlowchartGenRes = {
+  intent?: 'generate' | 'off_topic' | 'error'
   flowchart: string
+  nodes?: BackendNodeSpec[]
+  edges?: BackendEdgeSpec[]
+  message?: string
+  warnings?: string[]
+  suggestions?: string[]
+  tool_recommendations?: ToolRecommendation[]
   error?: string
 }