diff --git a/superset-frontend/src/components/Chart/DrillDetail/DrillDetailPane.tsx b/superset-frontend/src/components/Chart/DrillDetail/DrillDetailPane.tsx
index 9326b63b485..100c3d2f9eb 100644
--- a/superset-frontend/src/components/Chart/DrillDetail/DrillDetailPane.tsx
+++ b/superset-frontend/src/components/Chart/DrillDetail/DrillDetailPane.tsx
@@ -50,7 +50,6 @@ import Table, {
 import { RootState } from 'src/dashboard/types';
 import { usePermissions } from 'src/hooks/usePermissions';
 import { useToasts } from 'src/components/MessageToasts/withToasts';
-import { ensureAppRoot } from 'src/utils/pathUtils';
 import { safeStringify } from 'src/utils/safeStringify';
 import HeaderWithRadioGroup from '@superset-ui/core/components/Table/header-renderers/HeaderWithRadioGroup';
 import { useDatasetMetadataBar } from 'src/features/datasets/metadataBar/useDatasetMetadataBar';
@@ -249,7 +248,7 @@ export default function DrillDetailPane({
       if (dashboardId) {
         payload.form_data = { dashboardId };
       }
-      SupersetClient.postForm(ensureAppRoot('/api/v1/chart/data'), {
+      SupersetClient.postForm('/api/v1/chart/data', {
         form_data: safeStringify(payload),
       }).catch(error => {
         addDangerToast(
diff --git a/superset-frontend/src/components/Chart/chartAction.ts b/superset-frontend/src/components/Chart/chartAction.ts
index 40d8ed79b16..e5d9345b1cf 100644
--- a/superset-frontend/src/components/Chart/chartAction.ts
+++ b/superset-frontend/src/components/Chart/chartAction.ts
@@ -48,7 +48,6 @@ import { Logger, LOG_ACTIONS_LOAD_CHART } from 'src/logger/LogUtils';
 import { allowCrossDomain as domainShardingEnabled } from 'src/utils/hostNamesConfig';
 import { updateDataMask } from 'src/dataMask/actions';
 import { waitForAsyncData } from 'src/middleware/asyncEvent';
-import { ensureAppRoot } from 'src/utils/pathUtils';
 import { safeStringify } from 'src/utils/safeStringify';
 import { extendedDayjs } from '@superset-ui/core/utils/dates';
 import type { Dispatch, Action, AnyAction } from 'redux';
@@ -934,7 +933,7 @@ export function redirectSQLLab(
             requestedQuery: payload,
           });
         } else {
-          SupersetClient.postForm(ensureAppRoot(redirectUrl), {
+          SupersetClient.postForm(redirectUrl, {
             form_data: safeStringify(payload),
           });
         }
diff --git a/superset-frontend/src/explore/exploreUtils/exportChart.test.ts b/superset-frontend/src/explore/exploreUtils/exportChart.test.ts
index 74c905f347a..96428babe99 100644
--- a/superset-frontend/src/explore/exploreUtils/exportChart.test.ts
+++ b/superset-frontend/src/explore/exploreUtils/exportChart.test.ts
@@ -58,7 +58,9 @@ beforeEach(() => {
   });
 });
 
-// Tests for exportChart URL prefix handling in streaming export
+// Tests for exportChart URL prefix handling in streaming export.
+// Streaming uses native fetch (not SupersetClient), so exportChart must apply
+// ensureAppRoot before passing the URL to onStartStreamingExport.
 test('exportChart v1 API passes prefixed URL to onStartStreamingExport when app root is configured', async () => {
   const appRoot = '/superset';
   ensureAppRoot.mockImplementation((path: string) => `${appRoot}${path}`);
@@ -111,6 +113,24 @@ test('exportChart v1 API passes nested prefix for deeply nested deployments', as
   expect(callArgs.exportType).toBe('xlsx');
 });
 
+// Regression test for the double-prefix bug: SupersetClient.postForm adds appRoot
+// internally via getUrl(), so the URL passed must NOT already be prefixed.
+test('exportChart v1 API calls postForm with unprefixed URL when app root is configured', async () => {
+  const { SupersetClient } = jest.requireMock('@superset-ui/core');
+  const appRoot = '/analytics';
+  ensureAppRoot.mockImplementation((path: string) => `${appRoot}${path}`);
+
+  await exportChart({
+    formData: baseFormData,
+    resultFormat: 'csv',
+  });
+
+  expect(SupersetClient.postForm).toHaveBeenCalledTimes(1);
+  const [url] = SupersetClient.postForm.mock.calls[0];
+  expect(url).toBe('/api/v1/chart/data');
+  expect(url).not.toContain(appRoot);
+});
+
 test('exportChart passes csv exportType for CSV exports', async () => {
   const onStartStreamingExport = jest.fn();
 
@@ -143,7 +163,7 @@ test('exportChart passes xlsx exportType for Excel exports', async () => {
   );
 });
 
-test('exportChart legacy API (useLegacyApi=true) passes prefixed URL with app root configured', async () => {
+test('exportChart legacy API (useLegacyApi=true) passes prefixed URL to onStartStreamingExport when app root is configured', async () => {
   const appRoot = '/superset';
   ensureAppRoot.mockImplementation((path: string) => `${appRoot}${path}`);
 
@@ -165,6 +185,8 @@ test('exportChart legacy API (useLegacyApi=true) passes prefixed URL with app ro
 
   expect(onStartStreamingExport).toHaveBeenCalledTimes(1);
   const callArgs = onStartStreamingExport.mock.calls[0][0];
+  // The legacy blueprint path is /superset/explore_json/; with appRoot=/superset the
+  // full streaming URL is /superset/superset/explore_json/ (appRoot + blueprint prefix).
   expect(callArgs.url).toBe('/superset/superset/explore_json/?csv=true');
   expect(callArgs.exportType).toBe('csv');
 });
diff --git a/superset-frontend/src/explore/exploreUtils/index.ts b/superset-frontend/src/explore/exploreUtils/index.ts
index e0207f22dd7..23771a9ba97 100644
--- a/superset-frontend/src/explore/exploreUtils/index.ts
+++ b/superset-frontend/src/explore/exploreUtils/index.ts
@@ -76,6 +76,7 @@ interface GetExploreUrlParams {
   allowDomainSharding?: boolean;
   method?: 'GET' | 'POST';
   relative?: boolean;
+  includeAppRoot?: boolean;
 }
 
 interface BuildV1ChartDataPayloadParams {
@@ -223,6 +224,7 @@ export function getExploreUrl({
   allowDomainSharding = false,
   method = 'POST',
   relative = false,
+  includeAppRoot = true,
 }: GetExploreUrlParams): string | null {
   if (!formData.datasource) {
     return null;
@@ -242,7 +244,7 @@ export function getExploreUrl({
     uri = URI(URI(curUrl).search());
   }
 
-  const directory = getURIDirectory(endpointType);
+  const directory = getURIDirectory(endpointType, includeAppRoot);
 
   // Building the querystring (search) part of the URI
   const search = uri.search(true) as Record<string, string>;
@@ -370,10 +372,11 @@ export const exportChart = async ({
       force,
       allowDomainSharding: false,
       relative: true,
+      includeAppRoot: false,
     });
     payload = formData;
   } else {
-    url = ensureAppRoot('/api/v1/chart/data');
+    url = '/api/v1/chart/data';
     payload = await buildV1ChartDataPayload({
       formData,
       force,
@@ -385,14 +388,16 @@ export const exportChart = async ({
 
   // Check if streaming export handler is provided (from dashboard Chart.jsx)
   if (onStartStreamingExport) {
-    // Streaming is handled by the caller - pass URL, payload, and export type
+    // Streaming uses native fetch — apply appRoot prefix here since useStreamingExport
+    // does not go through SupersetClient (which would add it automatically).
     onStartStreamingExport({
-      url,
+      url: url ? ensureAppRoot(url) : url,
       payload,
       exportType: resultFormat,
     });
   } else {
-    // Fallback to original behavior for non-streaming exports
+    // SupersetClient.postForm calls getUrl({ endpoint }) internally, which prepends
+    // appRoot — so the URL must NOT be pre-prefixed here.
     SupersetClient.postForm(url as string, {
       form_data: safeStringify(payload),
     });