fix: undefined agent runner

- when trying to create an agent, check if the agent type exists
- server now checks requested agent runner type exists before trying to run against it.
- ui brings up a toast to indicate "agent doesn't exist" error

Author: Erez Sharim

chat/src/components/chat/multimodal-input.tsx

@@ -30,7 +30,7 @@ function PureMultimodalInput({
   handleSubmit: (
     event?: {
       preventDefault?: () => void;
-    },
+    }
     // chatRequestOptions?: ChatRequestOptions,
   ) => void;
   hasMessages: boolean;
@@ -67,7 +67,7 @@ function PureMultimodalInput({
 
   const [localStorageInput, setLocalStorageInput] = useLocalStorage(
     "input",
-    "",
+    ""
   );
 
   // biome-ignore lint/correctness/useExhaustiveDependencies: Only run once after hydration
@@ -92,19 +92,37 @@ function PureMultimodalInput({
 
   const submitForm = useCallback(async () => {
     if (newSession) {
-      await fetchClientWithThrow.POST("/api/sessions", {
-        body: {
-          id: sessionId,
-          title: input.split(" ").reduce((acc, word) => {
-            if (acc.length + word.length + 1 <= 15) {
-              return acc + (acc ? " " : "") + word;
-            }
-            return acc;
-          }, ""),
-          agent_id: agentId,
-        },
-      });
-      queyrClient.invalidateQueries({ queryKey: ["get", "/api/sessions", {}] });
+      try {
+        await fetchClientWithThrow.POST("/api/sessions", {
+          body: {
+            id: sessionId,
+            title: input.split(" ").reduce((acc, word) => {
+              if (acc.length + word.length + 1 <= 15) {
+                return acc + (acc ? " " : "") + word;
+              }
+              return acc;
+            }, ""),
+            agent_id: agentId,
+          },
+        });
+        queyrClient.invalidateQueries({
+          queryKey: ["get", "/api/sessions", {}],
+        });
+      } catch (error: any) {
+        const str = error.message || error.toString();
+        const jsonMatch = str.match(/{.*}/);
+        let err = "Failed to create new session";
+        if (jsonMatch) {
+          const parsed = JSON.parse(jsonMatch[0]);
+          const detail = parsed.detail;
+          if (detail) {
+            err = `Failed to create new session: ${detail}`;
+          }
+        }
+
+        toast.error(err);
+        return;
+      }
     }
 
     // navigate({ to: '/session/$sessionId', params: { sessionId: sessionIdToRedir } });
@@ -180,7 +198,7 @@ export const MultimodalInput = memo(
     if (prevProps.sessionId !== nextProps.sessionId) return false;
 
     return true;
-  },
+  }
 );
 
 function PureStopButton({
@@ -209,7 +227,10 @@ const StopButton = memo(PureStopButton);
 function PureSendButton({
   submitForm,
   input,
-}: { submitForm: () => void; input: string }) {
+}: {
+  submitForm: () => void;
+  input: string;
+}) {
   return (
     <Button
       className="rounded-full p-1.5 h-fit border dark:border-zinc-600"

packages/api/src/flux0_api/agents.py

@@ -5,7 +5,8 @@
 
 from flux0_api.auth import AuthedUser
 from flux0_api.common import apigen_config, example_json_content
-from flux0_api.dependency_injection import get_agent_store
+from flux0_api.dependency_injection import get_agent_store, get_session_service
+from flux0_api.session_service import SessionService
 from flux0_api.types_agents import (
     AgentCreationParamsDTO,
     AgentDTO,
@@ -19,7 +20,9 @@
 
 def mount_create_agent_route(
     router: APIRouter,
-) -> Callable[[AuthedUser, AgentCreationParamsDTO, AgentStore], Coroutine[None, Any, AgentDTO]]:
+) -> Callable[
+    [AuthedUser, AgentCreationParamsDTO, AgentStore, SessionService], Coroutine[None, Any, AgentDTO]
+]:
     @router.post(
         "",
         tags=[API_GROUP],
@@ -42,8 +45,17 @@ async def create_agent(
         authedUser: AuthedUser,
         params: AgentCreationParamsDTO,
         agent_store: AgentStore = Depends(get_agent_store),
+        session_service: SessionService = Depends(get_session_service),
     ) -> AgentDTO:
         """Creates a new agent with the specified parameters."""
+
+        # Ensure the agent type is supported by the agent runner factory.
+        if not session_service._agent_runner_factory.runner_exists(params.type):
+            raise HTTPException(
+                status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+                detail=f"Agent type '{params.type}' is not supported",
+            )
+
         agent = await agent_store.create_agent(
             name=params and params.name or "Unnamed Agent",
             type=params.type,

packages/api/src/flux0_api/sessions.py

@@ -76,6 +76,9 @@ def mount_create_session_route(
                 "description": "Session created successfully, Returns the created session along with its generated ID.",
                 "content": example_json_content(session_example),
             },
+            status.HTTP_400_BAD_REQUEST: {
+                "description": "Invalid request parameters, such as missing agent ID or invalid session ID format."
+            },
             status.HTTP_422_UNPROCESSABLE_ENTITY: {
                 "description": "Validation error in request parameters"
             },
@@ -90,7 +93,7 @@ async def create_session_route(
         allow_greeting: AllowGreetingQuery = False,
     ) -> SessionDTO:
         """
-        Create a new session bettween a user and an agent.
+        Create a new session between a user and an agent.
 
         The session will be associated with the provided agent and optionally with a user.
         If no user is provided, a guest user will be created.
@@ -102,6 +105,12 @@ async def create_session_route(
                 detail=f"Agent with ID {params.agent_id} not found",
             )
 
+        if not session_service._agent_runner_factory.runner_exists(agent.type):
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail=f"Agent type {agent.type} is not supported by the server",
+            )
+
         session = await session_service.create_user_session(
             id=params.id,
             user_id=authedUser.id,

packages/api/tests/conftest.py

@@ -122,6 +122,10 @@ def __init__(self, runner_class: type[AgentRunner] = DummyAgentRunner) -> None:
     def create_runner(self, agent_type: AgentType) -> AgentRunner:
         return self.runner_class()  # Instantiate the injected runner
 
+    def runner_exists(self, agent_type: AgentType) -> bool:
+        # For simplicity, we assume the injected runner always exists
+        return True
+
 
 @pytest.fixture
 def agent_runner_factory() -> AgentRunnerFactory:

packages/api/tests/test_agents.py

@@ -8,6 +8,7 @@
     mount_list_agents_route,
     mount_retrieve_agent_route,
 )
+from flux0_api.session_service import SessionService
 from flux0_api.types_agents import AgentCreationParamsDTO, AgentDTO
 from flux0_core.agents import Agent, AgentId, AgentStore
 from flux0_core.ids import gen_id
@@ -18,6 +19,7 @@ async def test_create_agent_success(
     user: User,
     agent: Agent,
     agent_store: AgentStore,
+    session_service: SessionService,
 ) -> None:
     router = APIRouter()
 
@@ -26,7 +28,7 @@ async def test_create_agent_success(
 
     # Create a dummy agent creation DTO. Adjust fields as needed.
     params = AgentCreationParamsDTO(name=agent.name, type=agent.type, description=agent.description)
-    result: AgentDTO = await create_route(user, params, agent_store)
+    result: AgentDTO = await create_route(user, params, agent_store, session_service)
 
     # Assert the returned agent has expected values.
     assert result.model_dump(exclude={"id", "created_at"}) == {

packages/core/src/flux0_core/agent_runners/api.py

@@ -43,6 +43,9 @@ class AgentRunnerFactory(ABC):
     @abstractmethod
     def create_runner(self, agent_type: AgentType) -> AgentRunner: ...
 
+    @abstractmethod
+    def runner_exists(self, agent_type: AgentType) -> bool: ...
+
 
 T = TypeVar("T", bound=AgentRunner)
 

packages/server/src/flux0_server/container_factory.py

@@ -17,3 +17,12 @@ def create_runner(self, agent_type: AgentType) -> AgentRunner:
             if issubclass(defi, AgentRunner) and getattr(defi, "agent_type") == agent_type:
                 return self.container[defi]
         raise ValueError(f"No engine found for agent type {agent_type}")
+
+    @override
+    def runner_exists(self, agent_type: AgentType) -> bool:
+        for defi in self.container.defined_types:
+            if not isinstance(defi, type):
+                continue
+            if issubclass(defi, AgentRunner) and getattr(defi, "agent_type") == agent_type:
+                return True
+        return False