fix: add AbortController timeout to fetchApi to prevent connection pool exhaustion

Without a timeout, a hung fetch occupies one of the browser's ~6 HTTP/1.1
connection slots indefinitely after long sessions, silently blocking all
subsequent requests to the same host (including POST /prompt).

- 60 s AbortController timeout on every fetchApi() call
- Caller-supplied signals are preserved via AbortSignal.any()
- Emits a Sentry breadcrumb and Mixpanel FETCH_TIMEOUT event before aborting
  so we can confirm the hypothesis in production and verify the fix

Fixes #14389

Author: christian-byrne

src/platform/telemetry/providers/cloud/MixpanelTelemetryProvider.ts

@@ -15,6 +15,7 @@ import type {
   CreditTopupMetadata,
   DefaultViewSetMetadata,
   EnterLinearMetadata,
+  FetchTimeoutMetadata,
   HelpCenterClosedMetadata,
   HelpCenterOpenedMetadata,
   HelpResourceClickedMetadata,
@@ -422,4 +423,8 @@ export class MixpanelTelemetryProvider implements TelemetryProvider {
   trackUiButtonClicked(metadata: UiButtonClickMetadata): void {
     this.trackEvent(TelemetryEvents.UI_BUTTON_CLICKED, metadata)
   }
+
+  trackFetchTimeout(metadata: FetchTimeoutMetadata): void {
+    this.trackEvent(TelemetryEvents.FETCH_TIMEOUT, metadata)
+  }
 }

src/platform/telemetry/types.ts

@@ -895,6 +895,13 @@ export function getBillingTelemetryEventPayload(event: BillingTelemetryEvent) {
   }
 }
 
+export interface FetchTimeoutMetadata {
+  route: string
+  method: string
+  duration_ms: number
+  timeout_ms: number
+}
+
 /**
  * Telemetry provider interface for individual providers.
  * All methods are optional - providers only implement what they need.
@@ -1022,6 +1029,9 @@ export interface TelemetryProvider {
 
   // Page view tracking
   trackPageView?(pageName: string, properties?: PageViewMetadata): void
+
+  // Network error events
+  trackFetchTimeout?(metadata: FetchTimeoutMetadata): void
 }
 
 /**
@@ -1166,7 +1176,10 @@ export const TelemetryEvents = {
   NAMED_VALUES_SHADOW_DIFF_SUMMARY: 'app:named_values_shadow_diff_summary',
 
   // Page View
-  PAGE_VIEW: 'app:page_view'
+  PAGE_VIEW: 'app:page_view',
+
+  // Network
+  FETCH_TIMEOUT: 'app:fetch_timeout'
 } as const
 
 export type TelemetryEventName =
@@ -1257,3 +1270,4 @@ export type TelemetryEventProperties =
   | SubscriptionSuccessMetadata
   | WorkspaceInviteFailedMetadata
   | BillingTelemetryEvent
+  | FetchTimeoutMetadata

src/scripts/api.ts

@@ -17,6 +17,8 @@ import type {
   ModelFolderInfo
 } from '@/platform/assets/schemas/assetSchema'
 import { isCloud } from '@/platform/distribution/types'
+import * as Sentry from '@sentry/vue'
+import { useTelemetry } from '@/platform/telemetry'
 import { useToastStore } from '@/platform/updates/common/toastStore'
 import type { ShareableAssetsResponse } from '@/schemas/apiSchema'
 import { zShareableAssetsResponse } from '@/schemas/apiSchema'
@@ -498,11 +500,42 @@ export class ComfyApi extends EventTarget {
     }
 
     addHeaderEntry(headers, 'Comfy-User', this.user)
+
+    // AbortController timeout prevents connection pool exhaustion after long sessions.
+    // See: https://github.com/Comfy-Org/ComfyUI_frontend/issues/14389
+    const FETCH_TIMEOUT_MS = 60_000
+    const controller = new AbortController()
+    const startTime = Date.now()
+    const timeoutId = setTimeout(() => {
+      const duration_ms = Date.now() - startTime
+      const method = (options?.method ?? 'GET').toUpperCase()
+
+      Sentry.addBreadcrumb({
+        category: 'fetch',
+        message: `Timeout on ${method} ${route}`,
+        level: 'warning',
+        data: { duration_ms, timeout_ms: FETCH_TIMEOUT_MS }
+      })
+
+      useTelemetry()?.trackFetchTimeout?.({
+        route,
+        method,
+        duration_ms,
+        timeout_ms: FETCH_TIMEOUT_MS
+      })
+
+      controller.abort()
+    }, FETCH_TIMEOUT_MS)
+
+    const signal = options?.signal
+      ? AbortSignal.any([options.signal, controller.signal])
+      : controller.signal
+
     return fetchWithUnifiedRemint(
       this.apiURL(route),
-      { cache: 'no-cache', ...options, headers },
+      { cache: 'no-cache', ...options, headers, signal },
       unifiedRetryOn401
-    )
+    ).finally(() => clearTimeout(timeoutId))
   }
 
   /**