fix: Resolve event delivery configuration header passing between frontend and backend

src/backend/base/langflow/api/build.py

@@ -13,6 +13,7 @@
 from langflow.api.disconnect import DisconnectHandlerStreamingResponse
 from langflow.api.utils import (
     CurrentActiveUser,
+    EventDeliveryType,
     build_graph_from_data,
     build_graph_from_db,
     format_elapsed_time,
@@ -84,12 +85,12 @@ async def get_flow_events_response(
     *,
     job_id: str,
     queue_service: JobQueueService,
-    stream: bool = True,
+    event_delivery: EventDeliveryType,
 ):
     """Get events for a specific build job, either as a stream or single event."""
     try:
         main_queue, event_manager, event_task, _ = queue_service.get_queue_data(job_id)
-        if stream:
+        if event_delivery in (EventDeliveryType.STREAMING, EventDeliveryType.DIRECT):
             if event_task is None:
                 logger.error(f"No event task found for job {job_id}")
                 raise HTTPException(status_code=404, detail="No event task found for job")

src/backend/base/langflow/api/utils.py

@@ -2,6 +2,7 @@
 
 import uuid
 from datetime import timedelta
+from enum import Enum
 from typing import TYPE_CHECKING, Annotated, Any
 
 from fastapi import Depends, HTTPException, Query
@@ -34,6 +35,12 @@
 DbSession = Annotated[AsyncSession, Depends(get_session)]
 
 
+class EventDeliveryType(str, Enum):
+    STREAMING = "streaming"
+    DIRECT = "direct"
+    POLLING = "polling"
+
+
 def has_api_terms(word: str):
     return "api" in word and ("key" in word or ("token" in word and "tokens" not in word))
 

src/backend/base/langflow/api/v1/chat.py

@@ -27,6 +27,7 @@
 from langflow.api.utils import (
     CurrentActiveUser,
     DbSession,
+    EventDeliveryType,
     build_and_cache_graph_from_data,
     build_graph_from_db,
     format_elapsed_time,
@@ -155,6 +156,7 @@ async def build_flow(
     queue_service: Annotated[JobQueueService, Depends(get_queue_service)],
     flow_name: str | None = None,
     settings_service: Annotated[SettingsService, Depends(get_settings_service)],
+    event_delivery: EventDeliveryType = EventDeliveryType.STREAMING,
 ):
     """Build and process a flow, returning a job ID for event polling.
 
@@ -174,6 +176,7 @@ async def build_flow(
         queue_service: Queue service for job management
         flow_name: Optional name for the flow
         settings_service: Settings service
+        event_delivery: Optional event delivery type - default is streaming
 
     Returns:
         Dict with job_id that can be used to poll for build status
@@ -197,12 +200,14 @@ async def build_flow(
         queue_service=queue_service,
         flow_name=flow_name,
     )
-    if settings_service.settings.event_delivery != "direct":
+
+    # This is required to support FE tests - we need to be able to set the event delivery to direct
+    if EventDeliveryType.DIRECT not in (settings_service.settings.event_delivery, event_delivery):
         return {"job_id": job_id}
     return await get_flow_events_response(
         job_id=job_id,
         queue_service=queue_service,
-        stream=True,
+        event_delivery=event_delivery,
     )
 
 
@@ -211,13 +216,13 @@ async def get_build_events(
     job_id: str,
     queue_service: Annotated[JobQueueService, Depends(get_queue_service)],
     *,
-    stream: bool = True,
+    event_delivery: EventDeliveryType = EventDeliveryType.STREAMING,
 ):
     """Get events for a specific build job."""
     return await get_flow_events_response(
         job_id=job_id,
         queue_service=queue_service,
-        stream=stream,
+        event_delivery=event_delivery,
     )
 
 

src/frontend/src/CustomNodes/GenericNode/components/NodeStatus/index.tsx

@@ -87,7 +87,7 @@ export default function NodeStatus({
   const isBuilding = useFlowStore((state) => state.isBuilding);
   const setNode = useFlowStore((state) => state.setNode);
   const version = useDarkStore((state) => state.version);
-  const config = useGetConfig();
+  const eventDeliveryConfig = useUtilityStore((state) => state.eventDelivery);
   const setErrorData = useAlertStore((state) => state.setErrorData);
 
   const postTemplateValue = usePostTemplateValue({
@@ -97,7 +97,7 @@ export default function NodeStatus({
   });
 
   const shouldStreamEvents = () => {
-    return config.data?.event_delivery === EventDeliveryType.STREAMING;
+    return eventDeliveryConfig === EventDeliveryType.STREAMING;
   };
 
   // Start polling when connection is initiated
@@ -170,7 +170,7 @@ export default function NodeStatus({
     buildFlow({
       stopNodeId: nodeId,
       stream: shouldStreamEvents(),
-      eventDelivery: config.data?.event_delivery,
+      eventDelivery: eventDeliveryConfig,
     });
   }
 
@@ -266,7 +266,7 @@ export default function NodeStatus({
     buildFlow({
       stopNodeId: nodeId,
       stream: shouldStreamEvents(),
-      eventDelivery: config.data?.event_delivery,
+      eventDelivery: eventDeliveryConfig,
     });
     track("Flow Build - Clicked", { stopNodeId: nodeId });
   };

src/frontend/src/controllers/API/api.tsx

@@ -6,7 +6,7 @@ import axios, { AxiosError, AxiosInstance, AxiosRequestConfig } from "axios";
 import * as fetchIntercept from "fetch-intercept";
 import { useEffect } from "react";
 import { Cookies } from "react-cookie";
-import { BuildStatus } from "../../constants/enums";
+import { BuildStatus, EventDeliveryType } from "../../constants/enums";
 import useAlertStore from "../../stores/alertStore";
 import useFlowStore from "../../stores/flowStore";
 import { checkDuplicateRequestAndStoreRequest } from "./helpers/check-duplicate-requests";
@@ -263,6 +263,7 @@ export type StreamingRequestParams = {
   onError?: (statusCode: number) => void;
   onNetworkError?: (error: Error) => void;
   buildController: AbortController;
+  eventDeliveryConfig?: EventDeliveryType;
 };
 
 async function performStreamingRequest({

src/frontend/src/controllers/API/queries/config/use-get-config.ts

@@ -39,7 +39,7 @@ export const useGetConfig: useQueryFunctionType<undefined, ConfigResponse> = (
   const setWebhookPollingInterval = useUtilityStore(
     (state) => state.setWebhookPollingInterval,
   );
-
+  const setEventDelivery = useUtilityStore((state) => state.setEventDelivery);
   const { query } = UseRequestProcessor();
 
   const getConfigFn = async () => {
@@ -59,6 +59,7 @@ export const useGetConfig: useQueryFunctionType<undefined, ConfigResponse> = (
       setWebhookPollingInterval(
         data.webhook_polling_interval ?? DEFAULT_POLLING_INTERVAL,
       );
+      setEventDelivery(data.event_delivery ?? EventDeliveryType.STREAMING);
     }
     return data;
   };

src/frontend/src/modals/IOModal/new-modal.tsx

@@ -155,10 +155,10 @@ export default function IOModal({
 
   const chatValue = useUtilityStore((state) => state.chatValueStore);
   const setChatValue = useUtilityStore((state) => state.setChatValueStore);
-  const config = useGetConfig();
+  const eventDeliveryConfig = useUtilityStore((state) => state.eventDelivery);
 
   function shouldStreamEvents() {
-    return config.data?.event_delivery === EventDeliveryType.STREAMING;
+    return eventDeliveryConfig === EventDeliveryType.STREAMING;
   }
 
   const sendMessage = useCallback(
@@ -179,7 +179,7 @@ export default function IOModal({
           silent: true,
           session: sessionId,
           stream: shouldStreamEvents(),
-          eventDelivery: config.data?.event_delivery,
+          eventDelivery: eventDeliveryConfig,
         }).catch((err) => {
           console.error(err);
         });

src/frontend/src/stores/utilityStore.ts

@@ -1,3 +1,4 @@
+import { EventDeliveryType } from "@/constants/enums";
 import { Pagination, Tag } from "@/types/utils/types";
 import { UtilityStoreType } from "@/types/zustand/utility";
 import { create } from "zustand";
@@ -43,4 +44,7 @@ export const useUtilityStore = create<UtilityStoreType>((set, get) => ({
   currentSessionId: "",
   setCurrentSessionId: (sessionId: string) =>
     set({ currentSessionId: sessionId }),
+  eventDelivery: EventDeliveryType.STREAMING,
+  setEventDelivery: (eventDelivery: EventDeliveryType) =>
+    set({ eventDelivery }),
 }));

src/frontend/src/types/zustand/utility/index.ts

@@ -1,3 +1,4 @@
+import { EventDeliveryType } from "@/constants/enums";
 import { Pagination, Tag } from "@/types/utils/types";
 
 export type UtilityStoreType = {
@@ -25,4 +26,6 @@ export type UtilityStoreType = {
   setCurrentSessionId: (sessionId: string) => void;
   setClientId: (clientId: string) => void;
   clientId: string;
+  eventDelivery: EventDeliveryType;
+  setEventDelivery: (eventDelivery: EventDeliveryType) => void;
 };

src/frontend/src/utils/buildUtils.ts

@@ -40,8 +40,8 @@ type BuildVerticesParams = {
   logBuilds?: boolean;
   session?: string;
   playgroundPage?: boolean;
-  stream?: boolean;
-  eventDelivery?: EventDeliveryType;
+  stream: boolean;
+  eventDelivery: EventDeliveryType;
 };
 
 function getInactiveVertexData(vertexId: string): VertexBuildTypeAPI {
@@ -148,7 +148,10 @@ export async function buildFlowVerticesWithFallback(
       e.message === POLLING_MESSAGES.STREAMING_NOT_SUPPORTED
     ) {
       // Fallback to polling
-      return await buildFlowVertices({ ...params, stream: false });
+      return await buildFlowVertices({
+        ...params,
+        eventDelivery: EventDeliveryType.POLLING,
+      });
     }
     throw e;
   }
@@ -176,13 +179,16 @@ async function pollBuildEvents(
 ): Promise<void> {
   let isDone = false;
   while (!isDone) {
-    const response = await fetch(`${url}?stream=false`, {
-      method: "GET",
-      headers: {
-        "Content-Type": "application/json",
+    const response = await fetch(
+      `${url}?event_delivery=${EventDeliveryType.POLLING}`,
+      {
+        method: "GET",
+        headers: {
+          "Content-Type": "application/json",
+        },
+        signal: abortController.signal, // Add abort signal to fetch
       },
-      signal: abortController.signal, // Add abort signal to fetch
-    });
+    );
 
     if (!response.ok) {
       const errorData = await response.json().catch(() => ({}));
@@ -241,7 +247,6 @@ export async function buildFlowVertices({
   logBuilds,
   session,
   playgroundPage,
-  stream = true,
   eventDelivery,
 }: BuildVerticesParams) {
   const inputs = {};
@@ -260,10 +265,10 @@ export async function buildFlowVertices({
     queryParams.append("log_builds", logBuilds.toString());
   }
 
-  // Add stream parameter when using direct event delivery
-  if (eventDelivery === EventDeliveryType.DIRECT) {
-    queryParams.append("stream", "true");
-  }
+  queryParams.append(
+    "event_delivery",
+    eventDelivery ?? EventDeliveryType.STREAMING,
+  );
 
   if (queryParams.toString()) {
     buildUrl = `${buildUrl}?${queryParams.toString()}`;
@@ -376,13 +381,12 @@ export async function buildFlowVertices({
       }
     });
     useFlowStore.getState().setBuildController(buildController);
-
     // Then stream the events
     const eventsUrl = `${BASE_URL_API}build/${job_id}/events`;
     const buildResults: Array<boolean> = [];
     const verticesStartTimeMs: Map<string, number> = new Map();
 
-    if (stream) {
+    if (eventDelivery === EventDeliveryType.STREAMING) {
       return performStreamingRequest({
         method: "GET",
         url: eventsUrl,