feat: model fallback chain (#2017) (#2018)

src/langbot/pkg/core/app.py

@@ -9,6 +9,7 @@ from ..platform import botmgr as im_mgr
 from ..platform.webhook_pusher import WebhookPusher
 from ..provider.session import sessionmgr as llm_session_mgr
 from ..provider.modelmgr import modelmgr as llm_model_mgr
+
 from langbot.pkg.provider.tools import toolmgr as llm_tool_mgr
 from ..config import manager as config_mgr
 from ..command import cmdmgr
@@ -30,6 +31,7 @@ from ..api.http.service import mcp as mcp_service
 from ..api.http.service import apikey as apikey_service
 from ..api.http.service import webhook as webhook_service
 from ..api.http.service import monitoring as monitoring_service
+
 from ..discover import engine as discover_engine
 from ..storage import mgr as storagemgr
 from ..utils import logcache

src/langbot/pkg/persistence/migrations/dbm023_model_fallback_config.py

@@ -0,0 +1,102 @@
+from .. import migration
+
+import sqlalchemy
+import json
+
+
+@migration.migration_class(23)
+class DBMigrateModelFallbackConfig(migration.DBMigration):
+    """Convert model field from plain UUID string to object with primary/fallbacks"""
+
+    async def upgrade(self):
+        """Upgrade"""
+        result = await self.ap.persistence_mgr.execute_async(
+            sqlalchemy.text('SELECT uuid, config FROM legacy_pipelines')
+        )
+        pipelines = result.fetchall()
+
+        current_version = self.ap.ver_mgr.get_current_version()
+
+        for pipeline_row in pipelines:
+            uuid = pipeline_row[0]
+            config = json.loads(pipeline_row[1]) if isinstance(pipeline_row[1], str) else pipeline_row[1]
+
+            if 'ai' not in config or 'local-agent' not in config['ai']:
+                continue
+
+            local_agent = config['ai']['local-agent']
+            changed = False
+
+            # Convert model from string to object
+            model_value = local_agent.get('model', '')
+            if isinstance(model_value, str):
+                local_agent['model'] = {
+                    'primary': model_value,
+                    'fallbacks': [],
+                }
+                changed = True
+
+            # Remove leftover fallback-models field if present
+            if 'fallback-models' in local_agent:
+                del local_agent['fallback-models']
+                changed = True
+
+            if not changed:
+                continue
+
+            # Update using raw SQL with compatibility for both SQLite and PostgreSQL
+            if self.ap.persistence_mgr.db.name == 'postgresql':
+                await self.ap.persistence_mgr.execute_async(
+                    sqlalchemy.text(
+                        'UPDATE legacy_pipelines SET config = :config::jsonb, for_version = :for_version WHERE uuid = :uuid'
+                    ),
+                    {'config': json.dumps(config), 'for_version': current_version, 'uuid': uuid},
+                )
+            else:
+                await self.ap.persistence_mgr.execute_async(
+                    sqlalchemy.text(
+                        'UPDATE legacy_pipelines SET config = :config, for_version = :for_version WHERE uuid = :uuid'
+                    ),
+                    {'config': json.dumps(config), 'for_version': current_version, 'uuid': uuid},
+                )
+
+    async def downgrade(self):
+        """Downgrade"""
+        result = await self.ap.persistence_mgr.execute_async(
+            sqlalchemy.text('SELECT uuid, config FROM legacy_pipelines')
+        )
+        pipelines = result.fetchall()
+
+        current_version = self.ap.ver_mgr.get_current_version()
+
+        for pipeline_row in pipelines:
+            uuid = pipeline_row[0]
+            config = json.loads(pipeline_row[1]) if isinstance(pipeline_row[1], str) else pipeline_row[1]
+
+            if 'ai' not in config or 'local-agent' not in config['ai']:
+                continue
+
+            local_agent = config['ai']['local-agent']
+
+            # Convert model from object back to string
+            model_value = local_agent.get('model', '')
+            if isinstance(model_value, dict):
+                local_agent['model'] = model_value.get('primary', '')
+            else:
+                continue
+
+            # Update using raw SQL with compatibility for both SQLite and PostgreSQL
+            if self.ap.persistence_mgr.db.name == 'postgresql':
+                await self.ap.persistence_mgr.execute_async(
+                    sqlalchemy.text(
+                        'UPDATE legacy_pipelines SET config = :config::jsonb, for_version = :for_version WHERE uuid = :uuid'
+                    ),
+                    {'config': json.dumps(config), 'for_version': current_version, 'uuid': uuid},
+                )
+            else:
+                await self.ap.persistence_mgr.execute_async(
+                    sqlalchemy.text(
+                        'UPDATE legacy_pipelines SET config = :config, for_version = :for_version WHERE uuid = :uuid'
+                    ),
+                    {'config': json.dumps(config), 'for_version': current_version, 'uuid': uuid},
+                )

src/langbot/pkg/pipeline/preproc/preproc.py

@@ -36,17 +36,36 @@ class PreProcessor(stage.PipelineStage):
         session = await self.ap.sess_mgr.get_session(query)
 
         # When not local-agent, llm_model is None
-        try:
+        llm_model = None
-            llm_model = (
+        if selected_runner == 'local-agent':
-                await self.ap.model_mgr.get_model_by_uuid(query.pipeline_config['ai']['local-agent']['model'])
+            # Read model config — new format is { primary: str, fallbacks: [str] },
-                if selected_runner == 'local-agent'
+            # but handle legacy plain string for backward compatibility
-                else None
+            model_config = query.pipeline_config['ai']['local-agent'].get('model', {})
-            )
+            if isinstance(model_config, str):
-        except ValueError:
+                # Legacy format: plain UUID string
-            self.ap.logger.warning(
+                primary_uuid = model_config
-                f'LLM model {query.pipeline_config["ai"]["local-agent"]["model"] + " "}not found or not configured'
+                fallback_uuids = []
-            )
+            else:
-            llm_model = None
+                primary_uuid = model_config.get('primary', '')
+                fallback_uuids = model_config.get('fallbacks', [])
+
+            if primary_uuid:
+                try:
+                    llm_model = await self.ap.model_mgr.get_model_by_uuid(primary_uuid)
+                except ValueError:
+                    self.ap.logger.warning(f'LLM model {primary_uuid} not found or not configured')
+
+            # Resolve fallback model UUIDs
+            if fallback_uuids:
+                valid_fallbacks = []
+                for fb_uuid in fallback_uuids:
+                    try:
+                        await self.ap.model_mgr.get_model_by_uuid(fb_uuid)
+                        valid_fallbacks.append(fb_uuid)
+                    except ValueError:
+                        self.ap.logger.warning(f'Fallback model {fb_uuid} not found, skipping')
+                if valid_fallbacks:
+                    query.variables['_fallback_model_uuids'] = valid_fallbacks
 
         conversation = await self.ap.sess_mgr.get_conversation(
             query,
@@ -61,20 +80,28 @@ class PreProcessor(stage.PipelineStage):
         query.prompt = conversation.prompt.copy()
         query.messages = conversation.messages.copy()
 
-        if selected_runner == 'local-agent' and llm_model:
+        if selected_runner == 'local-agent':
             query.use_funcs = []
-            query.use_llm_model_uuid = llm_model.model_entity.uuid
+            if llm_model:
+                query.use_llm_model_uuid = llm_model.model_entity.uuid
 
-            if llm_model.model_entity.abilities.__contains__('func_call'):
+                if llm_model.model_entity.abilities.__contains__('func_call'):
-                # Get bound plugins and MCP servers for filtering tools
+                    # Get bound plugins and MCP servers for filtering tools
+                    bound_plugins = query.variables.get('_pipeline_bound_plugins', None)
+                    bound_mcp_servers = query.variables.get('_pipeline_bound_mcp_servers', None)
+                    query.use_funcs = await self.ap.tool_mgr.get_all_tools(bound_plugins, bound_mcp_servers)
+
+                    self.ap.logger.debug(f'Bound plugins: {bound_plugins}')
+                    self.ap.logger.debug(f'Bound MCP servers: {bound_mcp_servers}')
+                    self.ap.logger.debug(f'Use funcs: {query.use_funcs}')
+
+            # If primary model doesn't support func_call but fallback models exist,
+            # load tools anyway since fallback models may support them
+            if not query.use_funcs and query.variables.get('_fallback_model_uuids'):
                 bound_plugins = query.variables.get('_pipeline_bound_plugins', None)
                 bound_mcp_servers = query.variables.get('_pipeline_bound_mcp_servers', None)
                 query.use_funcs = await self.ap.tool_mgr.get_all_tools(bound_plugins, bound_mcp_servers)
 
-                self.ap.logger.debug(f'Bound plugins: {bound_plugins}')
-                self.ap.logger.debug(f'Bound MCP servers: {bound_mcp_servers}')
-                self.ap.logger.debug(f'Use funcs: {query.use_funcs}')
-
         sender_name = ''
 
         if isinstance(query.message_event, platform_events.GroupMessage):

src/langbot/pkg/provider/runners/localagent.py

@@ -4,6 +4,7 @@ import json
 import copy
 import typing
 from .. import runner
+from ..modelmgr import requester as modelmgr_requester
 import langbot_plugin.api.entities.builtin.pipeline.query as pipeline_query
 import langbot_plugin.api.entities.builtin.provider.message as provider_message
 import langbot_plugin.api.entities.builtin.rag.context as rag_context
@@ -26,19 +27,109 @@ Respond in the same language as the user's input.
 
 @runner.runner_class('local-agent')
 class LocalAgentRunner(runner.RequestRunner):
-    """本地Agent请求运行器"""
+    """Local agent request runner"""
 
-    class ToolCallTracker:
+    async def _get_model_candidates(
-        """工具调用追踪器"""
+        self,
+        query: pipeline_query.Query,
+    ) -> list[modelmgr_requester.RuntimeLLMModel]:
+        """Build ordered list of models to try: primary model + fallback models."""
+        candidates = []
 
-        def __init__(self):
+        # Primary model
-            self.active_calls: dict[str, dict] = {}
+        if query.use_llm_model_uuid:
-            self.completed_calls: list[provider_message.ToolCall] = []
+            try:
+                primary = await self.ap.model_mgr.get_model_by_uuid(query.use_llm_model_uuid)
+                candidates.append(primary)
+            except ValueError:
+                self.ap.logger.warning(f'Primary model {query.use_llm_model_uuid} not found')
+
+        # Fallback models
+        fallback_uuids = (query.variables or {}).get('_fallback_model_uuids', [])
+        for fb_uuid in fallback_uuids:
+            try:
+                fb_model = await self.ap.model_mgr.get_model_by_uuid(fb_uuid)
+                candidates.append(fb_model)
+            except ValueError:
+                self.ap.logger.warning(f'Fallback model {fb_uuid} not found, skipping')
+
+        return candidates
+
+    async def _invoke_with_fallback(
+        self,
+        query: pipeline_query.Query,
+        candidates: list[modelmgr_requester.RuntimeLLMModel],
+        messages: list,
+        funcs: list,
+        remove_think: bool,
+    ) -> tuple[provider_message.Message, modelmgr_requester.RuntimeLLMModel]:
+        """Try non-streaming invocation with sequential fallback. Returns (message, model_used)."""
+        last_error = None
+        for model in candidates:
+            try:
+                msg = await model.provider.invoke_llm(
+                    query,
+                    model,
+                    messages,
+                    funcs if model.model_entity.abilities.__contains__('func_call') else [],
+                    extra_args=model.model_entity.extra_args,
+                    remove_think=remove_think,
+                )
+                return msg, model
+            except Exception as e:
+                last_error = e
+                self.ap.logger.warning(f'Model {model.model_entity.name} failed: {e}, trying next fallback...')
+        raise last_error or RuntimeError('No model candidates available')
+
+    async def _invoke_stream_with_fallback(
+        self,
+        query: pipeline_query.Query,
+        candidates: list[modelmgr_requester.RuntimeLLMModel],
+        messages: list,
+        funcs: list,
+        remove_think: bool,
+    ) -> tuple[typing.AsyncGenerator, modelmgr_requester.RuntimeLLMModel]:
+        """Try streaming invocation with sequential fallback. Returns (stream_generator, model_used).
+
+        Fallback is only possible before any chunks have been yielded to the client.
+        Once streaming starts, the model is committed.
+        """
+        last_error = None
+        for model in candidates:
+            try:
+                stream = model.provider.invoke_llm_stream(
+                    query,
+                    model,
+                    messages,
+                    funcs if model.model_entity.abilities.__contains__('func_call') else [],
+                    extra_args=model.model_entity.extra_args,
+                    remove_think=remove_think,
+                )
+                # Attempt to get the first chunk to verify the stream works
+                first_chunk = await stream.__anext__()
+
+                async def _chain_stream(first, rest):
+                    yield first
+                    async for chunk in rest:
+                        yield chunk
+
+                return _chain_stream(first_chunk, stream), model
+            except StopAsyncIteration:
+                # Empty stream — treat as success (model returned nothing)
+                async def _empty_stream():
+                    return
+                    yield  # make it a generator
+
+                return _empty_stream(), model
+            except Exception as e:
+                last_error = e
+                self.ap.logger.warning(f'Model {model.model_entity.name} stream failed: {e}, trying next fallback...')
+        raise last_error or RuntimeError('No model candidates available')
 
     async def run(
         self, query: pipeline_query.Query
     ) -> typing.AsyncGenerator[provider_message.Message | provider_message.MessageChunk, None]:
-        """运行请求"""
+        """Run request"""
         pending_tool_calls = []
 
         # Get knowledge bases list (new field)
@@ -119,51 +210,51 @@ class LocalAgentRunner(runner.RequestRunner):
 
         remove_think = query.pipeline_config['output'].get('misc', '').get('remove-think')
 
-        use_llm_model = await self.ap.model_mgr.get_model_by_uuid(query.use_llm_model_uuid)
+        # Build ordered candidate list (primary + fallbacks)
+        candidates = await self._get_model_candidates(query)
+        if not candidates:
+            raise RuntimeError('No LLM model configured for local-agent runner')
 
         self.ap.logger.debug(
-            f'localagent req: query={query.query_id} req_messages={req_messages} use_llm_model={query.use_llm_model_uuid}'
+            f'localagent req: query={query.query_id} req_messages={req_messages} '
+            f'candidates={[m.model_entity.name for m in candidates]}'
         )
 
         if not is_stream:
-            # 非流式输出，直接请求
+            # Non-streaming: invoke with fallback
-
+            msg, use_llm_model = await self._invoke_with_fallback(
-            msg = await use_llm_model.provider.invoke_llm(
                 query,
-                use_llm_model,
+                candidates,
                 req_messages,
                 query.use_funcs,
-                extra_args=use_llm_model.model_entity.extra_args,
+                remove_think,
-                remove_think=remove_think,
             )
             yield msg
             final_msg = msg
         else:
-            # 流式输出，需要处理工具调用
+            # Streaming: invoke with fallback
             tool_calls_map: dict[str, provider_message.ToolCall] = {}
             msg_idx = 0
-            accumulated_content = ''  # 从开始累积的所有内容
+            accumulated_content = ''
             last_role = 'assistant'
             msg_sequence = 1
-            async for msg in use_llm_model.provider.invoke_llm_stream(
+
+            stream_src, use_llm_model = await self._invoke_stream_with_fallback(
                 query,
-                use_llm_model,
+                candidates,
                 req_messages,
                 query.use_funcs,
-                extra_args=use_llm_model.model_entity.extra_args,
+                remove_think,
-                remove_think=remove_think,
+            )
-            ):
+            async for msg in stream_src:
                 msg_idx = msg_idx + 1
 
-                # 记录角色
                 if msg.role:
                     last_role = msg.role
 
-                # 累积内容
                 if msg.content:
                     accumulated_content += msg.content
 
-                # 处理工具调用
                 if msg.tool_calls:
                     for tool_call in msg.tool_calls:
                         if tool_call.id not in tool_calls_map:
@@ -175,21 +266,18 @@ class LocalAgentRunner(runner.RequestRunner):
                                 ),
                             )
                         if tool_call.function and tool_call.function.arguments:
-                            # 流式处理中，工具调用参数可能分多个chunk返回，需要追加而不是覆盖
                             tool_calls_map[tool_call.id].function.arguments += tool_call.function.arguments
-                # continue
+
-                # 每8个chunk或最后一个chunk时，输出所有累积的内容
                 if msg_idx % 8 == 0 or msg.is_final:
                     msg_sequence += 1
                     yield provider_message.MessageChunk(
                         role=last_role,
-                        content=accumulated_content,  # 输出所有累积内容
+                        content=accumulated_content,
                         tool_calls=list(tool_calls_map.values()) if (tool_calls_map and msg.is_final) else None,
                         is_final=msg.is_final,
                         msg_sequence=msg_sequence,
                     )
 
-            # 创建最终消息用于后续处理
             final_msg = provider_message.MessageChunk(
                 role=last_role,
                 content=accumulated_content,
@@ -204,7 +292,8 @@ class LocalAgentRunner(runner.RequestRunner):
 
         req_messages.append(final_msg)
 
-        # 持续请求，只要还有待处理的工具调用就继续处理调用
+        # Once a model succeeds, commit to it for the tool call loop
+        # (no fallback mid-conversation — different models may interpret tool results differently)
         while pending_tool_calls:
             for tool_call in pending_tool_calls:
                 try:
@@ -245,7 +334,6 @@ class LocalAgentRunner(runner.RequestRunner):
 
                     req_messages.append(msg)
                 except Exception as e:
-                    # 工具调用出错，添加一个报错信息到 req_messages
                     err_msg = provider_message.Message(role='tool', content=f'err: {e}', tool_call_id=tool_call.id)
 
                     yield err_msg
@@ -253,39 +341,38 @@ class LocalAgentRunner(runner.RequestRunner):
                     req_messages.append(err_msg)
 
             self.ap.logger.debug(
-                f'localagent req: query={query.query_id} req_messages={req_messages} use_llm_model={query.use_llm_model_uuid}'
+                f'localagent req: query={query.query_id} req_messages={req_messages} '
+                f'use_llm_model={use_llm_model.model_entity.name}'
             )
 
             if is_stream:
                 tool_calls_map = {}
                 msg_idx = 0
-                accumulated_content = ''  # 从开始累积的所有内容
+                accumulated_content = ''
                 last_role = 'assistant'
                 msg_sequence = first_end_sequence
 
-                async for msg in use_llm_model.provider.invoke_llm_stream(
+                tool_stream_src = use_llm_model.provider.invoke_llm_stream(
                     query,
                     use_llm_model,
                     req_messages,
-                    query.use_funcs,
+                    query.use_funcs if use_llm_model.model_entity.abilities.__contains__('func_call') else [],
                     extra_args=use_llm_model.model_entity.extra_args,
                     remove_think=remove_think,
-                ):
+                )
+                async for msg in tool_stream_src:
                     msg_idx += 1
 
-                    # 记录角色
                     if msg.role:
                         last_role = msg.role
 
-                    # 第一次请求工具调用时的内容
+                    # Prepend first-round content on first chunk of tool-call round
                     if msg_idx == 1:
                         accumulated_content = first_content if first_content is not None else accumulated_content
 
-                    # 累积内容
                     if msg.content:
                         accumulated_content += msg.content
 
-                    # 处理工具调用
                     if msg.tool_calls:
                         for tool_call in msg.tool_calls:
                             if tool_call.id not in tool_calls_map:
@@ -297,15 +384,13 @@ class LocalAgentRunner(runner.RequestRunner):
                                     ),
                                 )
                             if tool_call.function and tool_call.function.arguments:
-                                # 流式处理中，工具调用参数可能分多个chunk返回，需要追加而不是覆盖
                                 tool_calls_map[tool_call.id].function.arguments += tool_call.function.arguments
 
-                    # 每8个chunk或最后一个chunk时，输出所有累积的内容
                     if msg_idx % 8 == 0 or msg.is_final:
                         msg_sequence += 1
                         yield provider_message.MessageChunk(
                             role=last_role,
-                            content=accumulated_content,  # 输出所有累积内容
+                            content=accumulated_content,
                             tool_calls=list(tool_calls_map.values()) if (tool_calls_map and msg.is_final) else None,
                             is_final=msg.is_final,
                             msg_sequence=msg_sequence,
@@ -318,12 +403,12 @@ class LocalAgentRunner(runner.RequestRunner):
                     msg_sequence=msg_sequence,
                 )
             else:
-                # 处理完所有调用，再次请求
+                # Non-streaming: use committed model directly (no fallback in tool loop)
                 msg = await use_llm_model.provider.invoke_llm(
                     query,
                     use_llm_model,
                     req_messages,
-                    query.use_funcs,
+                    query.use_funcs if use_llm_model.model_entity.abilities.__contains__('func_call') else [],
                     extra_args=use_llm_model.model_entity.extra_args,
                     remove_think=remove_think,
                 )

src/langbot/pkg/utils/constants.py

@@ -2,7 +2,7 @@ import langbot
 
 semantic_version = f'v{langbot.__version__}'
 
-required_database_version = 22
+required_database_version = 23
 """Tag the version of the database schema, used to check if the database needs to be migrated"""
 
 debug_mode = False

src/langbot/templates/metadata/pipeline/ai.yaml

@@ -59,8 +59,11 @@ stages:
         label:
           en_US: Model
           zh_Hans: 模型
-        type: llm-model-selector
+        type: model-fallback-selector
         required: true
+        default:
+          primary: ''
+          fallbacks: []
       - name: max-round
         label:
           en_US: Max Round

web/src/app/home/bots/components/bot-form/BotForm.tsx

@@ -124,12 +124,6 @@ export default function BotForm({
   const currentAdapter = form.watch('adapter');
   const currentAdapterConfig = form.watch('adapter_config');
 
-  // Serialize adapter_config to a stable string so it can be used as a
-  // useEffect dependency without triggering on every render.  form.watch()
-  // returns a new object reference each time, which would otherwise cause
-  // the filtering effect below to loop indefinitely.
-  const adapterConfigJson = JSON.stringify(currentAdapterConfig);
-
   useEffect(() => {
     setBotFormValues();
   }, []);
@@ -153,7 +147,7 @@ export default function BotForm({
       // For non-Lark adapters, show all fields
       setFilteredDynamicFormConfigList(dynamicFormConfigList);
     }
-  }, [currentAdapter, adapterConfigJson, dynamicFormConfigList]);
+  }, [currentAdapter, currentAdapterConfig, dynamicFormConfigList]);
 
   // 复制到剪贴板的辅助函数 - 使用页面上的真实input元素
   const copyToClipboard = () => {

web/src/app/home/components/dynamic-form/DynamicFormComponent.tsx

@@ -11,7 +11,7 @@ import {
   FormMessage,
 } from '@/components/ui/form';
 import DynamicFormItemComponent from '@/app/home/components/dynamic-form/DynamicFormItemComponent';
-import { useCallback, useEffect, useRef } from 'react';
+import { useEffect, useRef } from 'react';
 import { extractI18nObject } from '@/i18n/I18nProvider';
 import { useTranslation } from 'react-i18next';
 
@@ -73,6 +73,12 @@ export default function DynamicFormComponent({
           case 'bot-selector':
             fieldSchema = z.string();
             break;
+          case 'model-fallback-selector':
+            fieldSchema = z.object({
+              primary: z.string(),
+              fallbacks: z.array(z.string()),
+            });
+            break;
           case 'prompt-editor':
             fieldSchema = z.array(
               z.object({
@@ -160,39 +166,34 @@ export default function DynamicFormComponent({
   const onSubmitRef = useRef(onSubmit);
   onSubmitRef.current = onSubmit;
 
-  // Track the last emitted values to avoid emitting identical snapshots,
+  // 监听表单值变化
-  // which would cause the parent to call setValue with an equivalent object,
+  useEffect(() => {
-  // triggering a re-render loop.
+    // Emit initial form values immediately so the parent always has a valid snapshot,
-  const lastEmittedRef = useRef<string>('');
+    // even if the user saves without modifying any field.
-
+    // form.watch(callback) only fires on subsequent changes, not on mount.
-  const emitValues = useCallback(() => {
     const formValues = form.getValues();
-    const finalValues = itemConfigList.reduce(
+    const initialFinalValues = itemConfigList.reduce(
       (acc, item) => {
         acc[item.name] = formValues[item.name] ?? item.default;
         return acc;
       },
       {} as Record<string, object>,
     );
-    const serialized = JSON.stringify(finalValues);
+    onSubmitRef.current?.(initialFinalValues);
-    if (serialized !== lastEmittedRef.current) {
-      lastEmittedRef.current = serialized;
-      onSubmitRef.current?.(finalValues);
-    }
-  }, [form, itemConfigList]);
-
-  // 监听表单值变化
-  useEffect(() => {
-    // Emit initial form values immediately so the parent always has a valid snapshot,
-    // even if the user saves without modifying any field.
-    // form.watch(callback) only fires on subsequent changes, not on mount.
-    emitValues();
 
     const subscription = form.watch(() => {
-      emitValues();
+      const formValues = form.getValues();
+      const finalValues = itemConfigList.reduce(
+        (acc, item) => {
+          acc[item.name] = formValues[item.name] ?? item.default;
+          return acc;
+        },
+        {} as Record<string, object>,
+      );
+      onSubmitRef.current?.(finalValues);
     });
     return () => subscription.unsubscribe();
-  }, [form, itemConfigList, emitValues]);
+  }, [form, itemConfigList]);
 
   return (
     <Form {...form}>
@@ -231,6 +232,7 @@ export default function DynamicFormComponent({
 
           // All fields are disabled when editing (creation_settings are immutable)
           const isFieldDisabled = !!isEditing;
+
           return (
             <FormField
               key={config.id}

web/src/app/home/components/dynamic-form/DynamicFormItemComponent.tsx

@@ -124,6 +124,28 @@ export default function DynamicFormItemComponent({
     }
   }, [config.type]);
 
+  useEffect(() => {
+    if (config.type === DynamicFormItemType.MODEL_FALLBACK_SELECTOR) {
+      httpClient
+        .getProviderLLMModels()
+        .then((resp) => {
+          let models = resp.models;
+          if (
+            systemInfo.disable_models_service ||
+            userInfo?.account_type !== 'space'
+          ) {
+            models = models.filter(
+              (m) => m.provider?.requester !== 'space-chat-completions',
+            );
+          }
+          setLlmModels(models);
+        })
+        .catch((err) => {
+          toast.error('Failed to get LLM model list: ' + err.msg);
+        });
+    }
+  }, [config.type]);
+
   useEffect(() => {
     if (
       config.type === DynamicFormItemType.KNOWLEDGE_BASE_SELECTOR ||
@@ -171,12 +193,7 @@ export default function DynamicFormItemComponent({
       return <Textarea {...field} className="min-h-[120px]" />;
 
     case DynamicFormItemType.BOOLEAN:
-      return (
+      return <Switch checked={field.value} onCheckedChange={field.onChange} />;
-        <Switch
-          checked={field.value ?? false}
-          onCheckedChange={field.onChange}
-        />
-      );
 
     case DynamicFormItemType.STRING_ARRAY:
       return (
@@ -227,7 +244,7 @@ export default function DynamicFormItemComponent({
 
     case DynamicFormItemType.SELECT:
       return (
-        <Select value={field.value ?? ''} onValueChange={field.onChange}>
+        <Select value={field.value} onValueChange={field.onChange}>
           <SelectTrigger className="bg-[#ffffff] dark:bg-[#2a2a2e]">
             <SelectValue placeholder={t('common.select')} />
           </SelectTrigger>
@@ -318,6 +335,172 @@ export default function DynamicFormItemComponent({
         </Select>
       );
 
+    case DynamicFormItemType.MODEL_FALLBACK_SELECTOR: {
+      // Group models by provider
+      const groupedModelsForFallback = llmModels.reduce(
+        (acc, model) => {
+          const providerName =
+            model.provider?.name || model.provider?.requester || 'Unknown';
+          if (!acc[providerName]) acc[providerName] = [];
+          acc[providerName].push(model);
+          return acc;
+        },
+        {} as Record<string, LLMModel[]>,
+      );
+
+      const modelValue = field.value as {
+        primary: string;
+        fallbacks: string[];
+      };
+
+      const renderModelSelect = (
+        value: string,
+        onChange: (val: string) => void,
+        placeholder: string,
+      ) => (
+        <Select value={value} onValueChange={onChange}>
+          <SelectTrigger className="bg-[#ffffff] dark:bg-[#2a2a2e]">
+            <SelectValue placeholder={placeholder} />
+          </SelectTrigger>
+          <SelectContent>
+            {Object.entries(groupedModelsForFallback).map(
+              ([providerName, models]) => (
+                <SelectGroup key={providerName}>
+                  <SelectLabel>{providerName}</SelectLabel>
+                  {models.map((model) => (
+                    <SelectItem key={model.uuid} value={model.uuid}>
+                      <span className="inline-flex items-center gap-1">
+                        {model.name}
+                        {model.abilities?.includes('vision') && (
+                          <Eye className="h-3 w-3 text-muted-foreground" />
+                        )}
+                        {model.abilities?.includes('func_call') && (
+                          <Wrench className="h-3 w-3 text-muted-foreground" />
+                        )}
+                      </span>
+                    </SelectItem>
+                  ))}
+                </SelectGroup>
+              ),
+            )}
+          </SelectContent>
+        </Select>
+      );
+
+      const updateValue = (patch: Partial<typeof modelValue>) => {
+        field.onChange({ ...modelValue, ...patch });
+      };
+
+      const addFallbackModel = () => {
+        updateValue({ fallbacks: [...modelValue.fallbacks, ''] });
+      };
+
+      const updateFallbackModel = (index: number, value: string) => {
+        const updated = [...modelValue.fallbacks];
+        updated[index] = value;
+        updateValue({ fallbacks: updated });
+      };
+
+      const removeFallbackModel = (index: number) => {
+        const updated = [...modelValue.fallbacks];
+        updated.splice(index, 1);
+        updateValue({ fallbacks: updated });
+      };
+
+      const moveFallbackModel = (index: number, direction: 'up' | 'down') => {
+        const updated = [...modelValue.fallbacks];
+        const newIndex = direction === 'up' ? index - 1 : index + 1;
+        if (newIndex < 0 || newIndex >= updated.length) return;
+        [updated[index], updated[newIndex]] = [
+          updated[newIndex],
+          updated[index],
+        ];
+        updateValue({ fallbacks: updated });
+      };
+
+      return (
+        <div className="space-y-3">
+          {/* Primary model selector */}
+          <div>
+            <p className="text-xs text-muted-foreground mb-1">
+              {t('models.fallback.primary')}
+            </p>
+            {renderModelSelect(
+              modelValue.primary,
+              (val) => updateValue({ primary: val }),
+              t('models.selectModel'),
+            )}
+          </div>
+
+          {/* Fallback models */}
+          {modelValue.fallbacks.length > 0 && (
+            <div className="space-y-2">
+              <p className="text-xs text-muted-foreground">
+                {t('models.fallback.fallbackList')}
+              </p>
+              {modelValue.fallbacks.map((fbUuid: string, index: number) => (
+                <div key={index} className="flex items-center gap-2">
+                  <span className="text-xs text-muted-foreground w-4 shrink-0">
+                    {index + 1}.
+                  </span>
+                  <div className="flex-1">
+                    {renderModelSelect(
+                      fbUuid,
+                      (val) => updateFallbackModel(index, val),
+                      t('models.selectModel'),
+                    )}
+                  </div>
+                  <div className="flex gap-1 shrink-0">
+                    <Button
+                      type="button"
+                      variant="ghost"
+                      size="sm"
+                      className="h-8 w-8 p-0"
+                      onClick={() => moveFallbackModel(index, 'up')}
+                      disabled={index === 0}
+                    >
+                      ↑
+                    </Button>
+                    <Button
+                      type="button"
+                      variant="ghost"
+                      size="sm"
+                      className="h-8 w-8 p-0"
+                      onClick={() => moveFallbackModel(index, 'down')}
+                      disabled={index === modelValue.fallbacks.length - 1}
+                    >
+                      ↓
+                    </Button>
+                    <Button
+                      type="button"
+                      variant="ghost"
+                      size="sm"
+                      className="h-8 w-8 p-0 text-destructive"
+                      onClick={() => removeFallbackModel(index)}
+                    >
+                      <X className="h-4 w-4" />
+                    </Button>
+                  </div>
+                </div>
+              ))}
+            </div>
+          )}
+
+          {/* Add fallback button */}
+          <Button
+            type="button"
+            variant="outline"
+            size="sm"
+            className="w-full"
+            onClick={addFallbackModel}
+          >
+            <Plus className="h-4 w-4 mr-1" />
+            {t('models.fallback.addFallback')}
+          </Button>
+        </div>
+      );
+    }
+
     case DynamicFormItemType.KNOWLEDGE_BASE_SELECTOR:
       // Group KBs by Knowledge Engine name
       const kbsByEngine = knowledgeBases.reduce(

web/src/app/home/components/models-dialog/ModelsDialog.tsx

@@ -463,14 +463,16 @@ export default function ModelsDialog({
                     )
                   : t('models.providerCount', { count: otherProviders.length })}
               </span>
-              <Button
+              <div className="flex gap-2">
-                size="sm"
+                <Button
-                variant="outline"
+                  size="sm"
-                onClick={handleCreateProvider}
+                  variant="outline"
-              >
+                  onClick={handleCreateProvider}
-                <Plus className="h-4 w-4 mr-1" />
+                >
-                {t('models.addProvider')}
+                  <Plus className="h-4 w-4 mr-1" />
-              </Button>
+                  {t('models.addProvider')}
+                </Button>
+              </div>
             </div>
 
             {/* Provider List */}

web/src/app/infra/entities/form/dynamic.ts

@@ -35,6 +35,7 @@ export enum DynamicFormItemType {
   SELECT = 'select',
   LLM_MODEL_SELECTOR = 'llm-model-selector',
   EMBEDDING_MODEL_SELECTOR = 'embedding-model-selector',
+  MODEL_FALLBACK_SELECTOR = 'model-fallback-selector',
   PROMPT_EDITOR = 'prompt-editor',
   UNKNOWN = 'unknown',
   KNOWLEDGE_BASE_SELECTOR = 'knowledge-base-selector',

web/src/i18n/locales/en-US.ts

@@ -236,6 +236,11 @@ const enUS = {
     modelsCount: '{{count}} model(s)',
     expandModels: 'Expand',
     collapseModels: 'Collapse',
+    fallback: {
+      primary: 'Primary Model',
+      fallbackList: 'Fallback Models',
+      addFallback: 'Add Fallback Model',
+    },
   },
   bots: {
     title: 'Bots',

web/src/i18n/locales/ja-JP.ts

@@ -1,4 +1,4 @@
-const jaJP = {
+const jaJP = {
   common: {
     login: 'ログイン',
     logout: 'ログアウト',
@@ -241,6 +241,11 @@ const jaJP = {
     modelsCount: '{{count}} 個のモデル',
     expandModels: '展開',
     collapseModels: '折りたたむ',
+    fallback: {
+      primary: 'プライマリモデル',
+      fallbackList: 'フォールバックモデル',
+      addFallback: 'フォールバックモデルを追加',
+    },
   },
   bots: {
     title: 'ボット',

web/src/i18n/locales/zh-Hans.ts

@@ -227,6 +227,11 @@ const zhHans = {
     modelsCount: '{{count}} 个模型',
     expandModels: '展开',
     collapseModels: '收起',
+    fallback: {
+      primary: '主模型',
+      fallbackList: '备用模型',
+      addFallback: '添加备用模型',
+    },
   },
   bots: {
     title: '机器人',

web/src/i18n/locales/zh-Hant.ts

@@ -226,6 +226,11 @@ const zhHant = {
     modelsCount: '{{count}} 個模型',
     expandModels: '展開',
     collapseModels: '收起',
+    fallback: {
+      primary: '主模型',
+      fallbackList: '備用模型',
+      addFallback: '新增備用模型',
+    },
   },
   bots: {
     title: '機器人',