From 829c7d0cda06a2284ea3c92d3d59eac849a26124 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Thu, 25 Dec 2025 12:05:50 +0200
Subject: [PATCH 01/10] fix

---
 packages/start-plugin-core/src/prerender.ts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/packages/start-plugin-core/src/prerender.ts b/packages/start-plugin-core/src/prerender.ts
index ea6368109e5..d55af441eea 100644
--- a/packages/start-plugin-core/src/prerender.ts
+++ b/packages/start-plugin-core/src/prerender.ts
@@ -2,6 +2,7 @@ import { promises as fsp } from 'node:fs'
 import os from 'node:os'
 import path from 'pathe'
 import { joinURL, withBase, withoutBase } from 'ufo'
+import { removeTrailingSlash } from '@tanstack/router-generator'
 import { VITE_ENVIRONMENT_NAMES } from './constants'
 import { createLogger } from './utils'
 import { Queue } from './queue'
@@ -270,6 +271,7 @@ async function startPreviewServer(
   try {
     return await vite.preview({
       configFile: viteConfig.configFile,
+      base: removeTrailingSlash(viteConfig.base),
       preview: {
         port: 0,
         open: false,

From b00df2209e45d592e41ae3a4e34b339af93d7c75 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Thu, 25 Dec 2025 12:06:04 +0200
Subject: [PATCH 02/10] update test

---
 e2e/react-start/custom-basepath/package.json  |  9 ++++-
 .../custom-basepath/playwright.config.ts      | 37 ++++++++++++++++++-
 .../custom-basepath/src/router.tsx            |  3 +-
 .../src/routes/users.$userId.tsx              |  8 ++--
 .../custom-basepath/src/routes/users.tsx      |  7 +++-
 .../custom-basepath/src/utils/basepath.ts     |  1 -
 .../custom-basepath/tests/navigation.spec.ts  |  8 +++-
 .../tests/utils/isPrerender.ts                |  1 +
 .../custom-basepath/vite.config.ts            | 19 +++++++++-
 9 files changed, 81 insertions(+), 12 deletions(-)
 delete mode 100644 e2e/react-start/custom-basepath/src/utils/basepath.ts
 create mode 100644 e2e/react-start/custom-basepath/tests/utils/isPrerender.ts

diff --git a/e2e/react-start/custom-basepath/package.json b/e2e/react-start/custom-basepath/package.json
index cdb371b91f9..c5262d3673c 100644
--- a/e2e/react-start/custom-basepath/package.json
+++ b/e2e/react-start/custom-basepath/package.json
@@ -6,9 +6,16 @@
   "scripts": {
     "dev": "cross-env NODE_ENV=development tsx express-server.ts",
     "build": "vite build && tsc --noEmit",
+    "build:prerender": "MODE=prerender vite build && tsc --noEmit",
+    "build:prerender:trailing": "MODE=prerender TRAILING_SLASH=true vite build && tsc --noEmit",
     "preview": "vite preview",
     "start": "tsx express-server.ts",
-    "test:e2e": "rm -rf port*.txt; playwright test --project=chromium"
+    "test:e2e:startDummyServer": "node -e 'import(\"./tests/setup/global.setup.ts\").then(m => m.default())' &",
+    "test:e2e:stopDummyServer": "node -e 'import(\"./tests/setup/global.teardown.ts\").then(m => m.default())'",
+    "test:e2e:prerender": "rm -rf port*.txt; MODE=prerender playwright test --project=chromium",
+    "test:e2e:prerender:trailing": "rm -rf port*.txt; MODE=prerender TRAILING_SLASH=true playwright test --project=chromium",
+    "test:e2e:ssrMode": "rm -rf port*.txt; playwright test --project=chromium",
+    "test:e2e": "pnpm run test:e2e:ssrMode && pnpm run test:e2e:prerender && pnpm run test:e2e:prerender:trailing"
   },
   "dependencies": {
     "@tanstack/react-router": "workspace:^",
diff --git a/e2e/react-start/custom-basepath/playwright.config.ts b/e2e/react-start/custom-basepath/playwright.config.ts
index 5095425f473..17c013aaa6c 100644
--- a/e2e/react-start/custom-basepath/playwright.config.ts
+++ b/e2e/react-start/custom-basepath/playwright.config.ts
@@ -4,11 +4,36 @@ import {
   getTestServerPort,
 } from '@tanstack/router-e2e-utils'
 import packageJson from './package.json' with { type: 'json' }
+import { isPrerender } from './tests/utils/isPrerender'
 
 const PORT = await getTestServerPort(packageJson.name)
+const START_PORT = await getTestServerPort(packageJson.name)
 const EXTERNAL_PORT = await getDummyServerPort(packageJson.name)
 const baseURL = `http://localhost:${PORT}/custom/basepath`
 
+const ssrModeCommand = `pnpm build && pnpm start`
+const prerenderModeCommand = `pnpm run test:e2e:startDummyServer && pnpm build:prerender && pnpm run test:e2e:stopDummyServer && pnpm start`
+const prerenderTrailingModeCommand = `pnpm run test:e2e:startDummyServer && pnpm build:prerender:trailing && pnpm run test:e2e:stopDummyServer && pnpm start`
+const isTrailingSlashPrerender =
+  process.env.TRAILING_SLASH?.toLowerCase() === 'true'
+
+const getCommand = () => {
+  if (isPrerender && isTrailingSlashPrerender)
+    return prerenderTrailingModeCommand
+  if (isPrerender) return prerenderModeCommand
+  return ssrModeCommand
+}
+
+console.log(
+  'running in prerender mode: ',
+  isPrerender.toString(),
+  isPrerender
+    ? isTrailingSlashPrerender
+      ? 'with trailing slash'
+      : 'without trailing slash'
+    : '',
+)
+
 /**
  * See https://playwright.dev/docs/test-configuration.
  */
@@ -27,10 +52,20 @@ export default defineConfig({
   },
 
   webServer: {
-    command: `VITE_NODE_ENV="test" VITE_EXTERNAL_PORT=${EXTERNAL_PORT} pnpm build && VITE_NODE_ENV="test" VITE_EXTERNAL_PORT=${EXTERNAL_PORT} VITE_SERVER_PORT=${PORT} PORT=${PORT} pnpm start`,
+    command: getCommand(),
     url: baseURL,
     reuseExistingServer: !process.env.CI,
     stdout: 'pipe',
+    env: {
+      MODE: process.env.MODE || '',
+      TRAILING_SLASH: isTrailingSlashPrerender.toString(),
+      VITE_TRAILING_SLASH: isTrailingSlashPrerender.toString(),
+      VITE_NODE_ENV: 'test',
+      VITE_EXTERNAL_PORT: String(EXTERNAL_PORT),
+      VITE_SERVER_PORT: String(PORT),
+      START_PORT: String(START_PORT),
+      PORT: String(PORT),
+    },
   },
 
   projects: [
diff --git a/e2e/react-start/custom-basepath/src/router.tsx b/e2e/react-start/custom-basepath/src/router.tsx
index 81b4c31daa8..62422fc2dfc 100644
--- a/e2e/react-start/custom-basepath/src/router.tsx
+++ b/e2e/react-start/custom-basepath/src/router.tsx
@@ -2,7 +2,6 @@ import { createRouter } from '@tanstack/react-router'
 import { routeTree } from './routeTree.gen'
 import { DefaultCatchBoundary } from './components/DefaultCatchBoundary'
 import { NotFound } from './components/NotFound'
-import { basepath } from './utils/basepath'
 
 export function getRouter() {
   const router = createRouter({
@@ -11,7 +10,7 @@ export function getRouter() {
     defaultErrorComponent: DefaultCatchBoundary,
     defaultNotFoundComponent: () => <NotFound />,
     scrollRestoration: true,
-    basepath: basepath,
+    basepath: import.meta.env.BASE_URL,
   })
 
   return router
diff --git a/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx b/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx
index f811910df42..104703bf303 100644
--- a/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx
+++ b/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx
@@ -1,15 +1,17 @@
 import { ErrorComponent, createFileRoute } from '@tanstack/react-router'
 import axios from 'redaxios'
+import { getRouterInstance } from '@tanstack/react-start'
 import type { ErrorComponentProps } from '@tanstack/react-router'
-
 import type { User } from '~/utils/users'
 import { NotFound } from '~/components/NotFound'
-import { basepath } from '~/utils/basepath'
 
 export const Route = createFileRoute('/users/$userId')({
   loader: async ({ params: { userId } }) => {
+    const router = await getRouterInstance()
     return await axios
-      .get<User>(basepath + '/api/users/' + userId)
+      .get<User>('/api/users/' + userId, {
+        baseURL: router.options.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch user')
diff --git a/e2e/react-start/custom-basepath/src/routes/users.tsx b/e2e/react-start/custom-basepath/src/routes/users.tsx
index e78600349f7..a7b5a1d316a 100644
--- a/e2e/react-start/custom-basepath/src/routes/users.tsx
+++ b/e2e/react-start/custom-basepath/src/routes/users.tsx
@@ -1,12 +1,15 @@
 import { Link, Outlet, createFileRoute } from '@tanstack/react-router'
 import axios from 'redaxios'
+import { getRouterInstance } from '@tanstack/react-start'
 import type { User } from '~/utils/users'
-import { basepath } from '~/utils/basepath'
 
 export const Route = createFileRoute('/users')({
   loader: async () => {
+    const router = await getRouterInstance()
     return await axios
-      .get<Array<User>>(basepath + '/api/users')
+      .get<Array<User>>('/api/users', {
+        baseURL: router.options.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch users')
diff --git a/e2e/react-start/custom-basepath/src/utils/basepath.ts b/e2e/react-start/custom-basepath/src/utils/basepath.ts
deleted file mode 100644
index 6e719f196cf..00000000000
--- a/e2e/react-start/custom-basepath/src/utils/basepath.ts
+++ /dev/null
@@ -1 +0,0 @@
-export const basepath = '/custom/basepath'
diff --git a/e2e/react-start/custom-basepath/tests/navigation.spec.ts b/e2e/react-start/custom-basepath/tests/navigation.spec.ts
index e238134d2ed..fb1d2f1367e 100644
--- a/e2e/react-start/custom-basepath/tests/navigation.spec.ts
+++ b/e2e/react-start/custom-basepath/tests/navigation.spec.ts
@@ -1,4 +1,5 @@
 import { expect, test } from '@playwright/test'
+import { isPrerender } from './utils/isPrerender'
 
 test('Navigating to post', async ({ page }) => {
   await page.goto('/')
@@ -58,7 +59,12 @@ test('server-side redirect', async ({ page, baseURL }) => {
   await page.waitForLoadState('networkidle')
 
   expect(await page.getByTestId('post-view').isVisible()).toBe(true)
-  expect(page.url()).toBe(`${baseURL}/posts/1`)
+
+  if (isPrerender) {
+    expect(page.url()).toBe(`${baseURL}/posts/1/`)
+  } else {
+    expect(page.url()).toBe(`${baseURL}/posts/1`)
+  }
 
   // do not follow redirects since we want to test the Location header
   // Both requests (with or without basepath) should redirect directly to the final destination.
diff --git a/e2e/react-start/custom-basepath/tests/utils/isPrerender.ts b/e2e/react-start/custom-basepath/tests/utils/isPrerender.ts
new file mode 100644
index 00000000000..d5d991d4545
--- /dev/null
+++ b/e2e/react-start/custom-basepath/tests/utils/isPrerender.ts
@@ -0,0 +1 @@
+export const isPrerender: boolean = process.env.MODE === 'prerender'
diff --git a/e2e/react-start/custom-basepath/vite.config.ts b/e2e/react-start/custom-basepath/vite.config.ts
index 75559f50a17..fe5c8910c93 100644
--- a/e2e/react-start/custom-basepath/vite.config.ts
+++ b/e2e/react-start/custom-basepath/vite.config.ts
@@ -3,9 +3,25 @@ import tsConfigPaths from 'vite-tsconfig-paths'
 import { tanstackStart } from '@tanstack/react-start/plugin/vite'
 import viteReact from '@vitejs/plugin-react'
 import tailwindcss from '@tailwindcss/vite'
+import { isPrerender } from './tests/utils/isPrerender'
+
+const prerenderConfiguration = {
+  enabled: true,
+  filter: (page: { path: string }) => {
+    return ![
+      '/i-do-not-exist',
+      '/this-route-does-not-exist',
+      '/redirect',
+      '/users',
+    ].some((p) => page.path.includes(p))
+  },
+  onSuccess: ({ page }: { page: { path: string } }) => {
+    console.log(`Rendered ${page.path}!`)
+  },
+}
 
 export default defineConfig({
-  base: '/custom/basepath',
+  base: `/custom/basepath${process.env.TRAILING_SLASH?.toLowerCase() === 'true' ? '/' : ''}`,
   server: {
     port: 3000,
   },
@@ -16,6 +32,7 @@ export default defineConfig({
     }),
     tanstackStart({
       vite: { installDevServerMiddleware: true },
+      prerender: isPrerender ? prerenderConfiguration : undefined,
     }),
     viteReact(),
   ],

From 81573029a0e2baba6083111ed723969201ae8d47 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Thu, 25 Dec 2025 15:01:26 +0200
Subject: [PATCH 03/10] replicate tests for vue and solid

---
 e2e/solid-start/custom-basepath/package.json  |  9 ++++-
 .../custom-basepath/playwright.config.ts      | 37 ++++++++++++++++++-
 .../custom-basepath/src/router.tsx            |  3 +-
 .../src/routes/users.$userId.tsx              |  8 ++--
 .../custom-basepath/src/routes/users.tsx      |  7 +++-
 .../custom-basepath/src/utils/basepath.ts     |  1 -
 .../custom-basepath/tests/navigation.spec.ts  |  8 +++-
 .../tests/utils/isPrerender.ts                |  1 +
 .../custom-basepath/vite.config.ts            | 22 ++++++++++-
 e2e/vue-start/custom-basepath/package.json    |  9 ++++-
 .../custom-basepath/playwright.config.ts      | 37 ++++++++++++++++++-
 e2e/vue-start/custom-basepath/src/router.tsx  |  3 +-
 .../src/routes/users.$userId.tsx              |  8 ++--
 .../custom-basepath/src/routes/users.tsx      |  7 +++-
 .../custom-basepath/src/utils/basepath.ts     |  1 -
 .../custom-basepath/tests/navigation.spec.ts  |  8 +++-
 .../tests/utils/isPrerender.ts                |  1 +
 e2e/vue-start/custom-basepath/vite.config.ts  | 22 ++++++++++-
 18 files changed, 166 insertions(+), 26 deletions(-)
 delete mode 100644 e2e/solid-start/custom-basepath/src/utils/basepath.ts
 create mode 100644 e2e/solid-start/custom-basepath/tests/utils/isPrerender.ts
 delete mode 100644 e2e/vue-start/custom-basepath/src/utils/basepath.ts
 create mode 100644 e2e/vue-start/custom-basepath/tests/utils/isPrerender.ts

diff --git a/e2e/solid-start/custom-basepath/package.json b/e2e/solid-start/custom-basepath/package.json
index e706b214533..cd19493acf8 100644
--- a/e2e/solid-start/custom-basepath/package.json
+++ b/e2e/solid-start/custom-basepath/package.json
@@ -6,9 +6,16 @@
   "scripts": {
     "dev": "cross-env NODE_ENV=development tsx express-server.ts",
     "build": "vite build && tsc --noEmit",
+    "build:prerender": "MODE=prerender vite build && tsc --noEmit",
+    "build:prerender:trailing": "MODE=prerender TRAILING_SLASH=true vite build && tsc --noEmit",
     "preview": "vite preview",
     "start": "tsx express-server.ts",
-    "test:e2e": "rm -rf port*.txt; playwright test --project=chromium"
+    "test:e2e:startDummyServer": "node -e 'import(\"./tests/setup/global.setup.ts\").then(m => m.default())' &",
+    "test:e2e:stopDummyServer": "node -e 'import(\"./tests/setup/global.teardown.ts\").then(m => m.default())'",
+    "test:e2e:prerender": "rm -rf port*.txt; MODE=prerender playwright test --project=chromium",
+    "test:e2e:prerender:trailing": "rm -rf port*.txt; MODE=prerender TRAILING_SLASH=true playwright test --project=chromium",
+    "test:e2e:ssrMode": "rm -rf port*.txt; playwright test --project=chromium",
+    "test:e2e": "pnpm run test:e2e:ssrMode && pnpm run test:e2e:prerender && pnpm run test:e2e:prerender:trailing"
   },
   "dependencies": {
     "@tanstack/solid-router": "workspace:^",
diff --git a/e2e/solid-start/custom-basepath/playwright.config.ts b/e2e/solid-start/custom-basepath/playwright.config.ts
index 5095425f473..17c013aaa6c 100644
--- a/e2e/solid-start/custom-basepath/playwright.config.ts
+++ b/e2e/solid-start/custom-basepath/playwright.config.ts
@@ -4,11 +4,36 @@ import {
   getTestServerPort,
 } from '@tanstack/router-e2e-utils'
 import packageJson from './package.json' with { type: 'json' }
+import { isPrerender } from './tests/utils/isPrerender'
 
 const PORT = await getTestServerPort(packageJson.name)
+const START_PORT = await getTestServerPort(packageJson.name)
 const EXTERNAL_PORT = await getDummyServerPort(packageJson.name)
 const baseURL = `http://localhost:${PORT}/custom/basepath`
 
+const ssrModeCommand = `pnpm build && pnpm start`
+const prerenderModeCommand = `pnpm run test:e2e:startDummyServer && pnpm build:prerender && pnpm run test:e2e:stopDummyServer && pnpm start`
+const prerenderTrailingModeCommand = `pnpm run test:e2e:startDummyServer && pnpm build:prerender:trailing && pnpm run test:e2e:stopDummyServer && pnpm start`
+const isTrailingSlashPrerender =
+  process.env.TRAILING_SLASH?.toLowerCase() === 'true'
+
+const getCommand = () => {
+  if (isPrerender && isTrailingSlashPrerender)
+    return prerenderTrailingModeCommand
+  if (isPrerender) return prerenderModeCommand
+  return ssrModeCommand
+}
+
+console.log(
+  'running in prerender mode: ',
+  isPrerender.toString(),
+  isPrerender
+    ? isTrailingSlashPrerender
+      ? 'with trailing slash'
+      : 'without trailing slash'
+    : '',
+)
+
 /**
  * See https://playwright.dev/docs/test-configuration.
  */
@@ -27,10 +52,20 @@ export default defineConfig({
   },
 
   webServer: {
-    command: `VITE_NODE_ENV="test" VITE_EXTERNAL_PORT=${EXTERNAL_PORT} pnpm build && VITE_NODE_ENV="test" VITE_EXTERNAL_PORT=${EXTERNAL_PORT} VITE_SERVER_PORT=${PORT} PORT=${PORT} pnpm start`,
+    command: getCommand(),
     url: baseURL,
     reuseExistingServer: !process.env.CI,
     stdout: 'pipe',
+    env: {
+      MODE: process.env.MODE || '',
+      TRAILING_SLASH: isTrailingSlashPrerender.toString(),
+      VITE_TRAILING_SLASH: isTrailingSlashPrerender.toString(),
+      VITE_NODE_ENV: 'test',
+      VITE_EXTERNAL_PORT: String(EXTERNAL_PORT),
+      VITE_SERVER_PORT: String(PORT),
+      START_PORT: String(START_PORT),
+      PORT: String(PORT),
+    },
   },
 
   projects: [
diff --git a/e2e/solid-start/custom-basepath/src/router.tsx b/e2e/solid-start/custom-basepath/src/router.tsx
index b940fffea80..71efa7e12a1 100644
--- a/e2e/solid-start/custom-basepath/src/router.tsx
+++ b/e2e/solid-start/custom-basepath/src/router.tsx
@@ -2,7 +2,6 @@ import { createRouter } from '@tanstack/solid-router'
 import { routeTree } from './routeTree.gen'
 import { DefaultCatchBoundary } from './components/DefaultCatchBoundary'
 import { NotFound } from './components/NotFound'
-import { basepath } from './utils/basepath'
 
 export function getRouter() {
   const router = createRouter({
@@ -11,7 +10,7 @@ export function getRouter() {
     defaultErrorComponent: DefaultCatchBoundary,
     defaultNotFoundComponent: () => <NotFound />,
     scrollRestoration: true,
-    basepath: basepath,
+    basepath: import.meta.env.BASE_URL,
   })
 
   return router
diff --git a/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx b/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx
index db5614394af..dcb0e1d28fe 100644
--- a/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx
+++ b/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx
@@ -1,15 +1,17 @@
 import { createFileRoute } from '@tanstack/solid-router'
 import axios from 'redaxios'
-
+import { getRouterInstance } from '@tanstack/solid-start'
 import type { User } from '~/utils/users'
 import { NotFound } from '~/components/NotFound'
 import { UserErrorComponent } from '~/components/UserErrorComponent'
-import { basepath } from '~/utils/basepath'
 
 export const Route = createFileRoute('/users/$userId')({
   loader: async ({ params: { userId } }) => {
+    const router = await getRouterInstance()
     return await axios
-      .get<User>(basepath + '/api/users/' + userId)
+      .get<User>('/api/users/' + userId, {
+        baseURL: router.options.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch user')
diff --git a/e2e/solid-start/custom-basepath/src/routes/users.tsx b/e2e/solid-start/custom-basepath/src/routes/users.tsx
index b686fa91cda..d1d312df3ee 100644
--- a/e2e/solid-start/custom-basepath/src/routes/users.tsx
+++ b/e2e/solid-start/custom-basepath/src/routes/users.tsx
@@ -1,12 +1,15 @@
 import { Link, Outlet, createFileRoute } from '@tanstack/solid-router'
 import axios from 'redaxios'
+import { getRouterInstance } from '@tanstack/solid-start'
 import type { User } from '~/utils/users'
-import { basepath } from '~/utils/basepath'
 
 export const Route = createFileRoute('/users')({
   loader: async () => {
+    const router = await getRouterInstance()
     return await axios
-      .get<Array<User>>(basepath + '/api/users')
+      .get<Array<User>>('/api/users', {
+        baseURL: router.options.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch users')
diff --git a/e2e/solid-start/custom-basepath/src/utils/basepath.ts b/e2e/solid-start/custom-basepath/src/utils/basepath.ts
deleted file mode 100644
index 6e719f196cf..00000000000
--- a/e2e/solid-start/custom-basepath/src/utils/basepath.ts
+++ /dev/null
@@ -1 +0,0 @@
-export const basepath = '/custom/basepath'
diff --git a/e2e/solid-start/custom-basepath/tests/navigation.spec.ts b/e2e/solid-start/custom-basepath/tests/navigation.spec.ts
index e238134d2ed..fb1d2f1367e 100644
--- a/e2e/solid-start/custom-basepath/tests/navigation.spec.ts
+++ b/e2e/solid-start/custom-basepath/tests/navigation.spec.ts
@@ -1,4 +1,5 @@
 import { expect, test } from '@playwright/test'
+import { isPrerender } from './utils/isPrerender'
 
 test('Navigating to post', async ({ page }) => {
   await page.goto('/')
@@ -58,7 +59,12 @@ test('server-side redirect', async ({ page, baseURL }) => {
   await page.waitForLoadState('networkidle')
 
   expect(await page.getByTestId('post-view').isVisible()).toBe(true)
-  expect(page.url()).toBe(`${baseURL}/posts/1`)
+
+  if (isPrerender) {
+    expect(page.url()).toBe(`${baseURL}/posts/1/`)
+  } else {
+    expect(page.url()).toBe(`${baseURL}/posts/1`)
+  }
 
   // do not follow redirects since we want to test the Location header
   // Both requests (with or without basepath) should redirect directly to the final destination.
diff --git a/e2e/solid-start/custom-basepath/tests/utils/isPrerender.ts b/e2e/solid-start/custom-basepath/tests/utils/isPrerender.ts
new file mode 100644
index 00000000000..d5d991d4545
--- /dev/null
+++ b/e2e/solid-start/custom-basepath/tests/utils/isPrerender.ts
@@ -0,0 +1 @@
+export const isPrerender: boolean = process.env.MODE === 'prerender'
diff --git a/e2e/solid-start/custom-basepath/vite.config.ts b/e2e/solid-start/custom-basepath/vite.config.ts
index bbc8fea1019..ef8785cab39 100644
--- a/e2e/solid-start/custom-basepath/vite.config.ts
+++ b/e2e/solid-start/custom-basepath/vite.config.ts
@@ -3,9 +3,25 @@ import tsConfigPaths from 'vite-tsconfig-paths'
 import { tanstackStart } from '@tanstack/solid-start/plugin/vite'
 import viteSolid from 'vite-plugin-solid'
 import tailwindcss from '@tailwindcss/vite'
+import { isPrerender } from './tests/utils/isPrerender'
+
+const prerenderConfiguration = {
+  enabled: true,
+  filter: (page: { path: string }) => {
+    return ![
+      '/i-do-not-exist',
+      '/this-route-does-not-exist',
+      '/redirect',
+      '/users',
+    ].some((p) => page.path.includes(p))
+  },
+  onSuccess: ({ page }: { page: { path: string } }) => {
+    console.log(`Rendered ${page.path}!`)
+  },
+}
 
 export default defineConfig({
-  base: '/custom/basepath',
+  base: `/custom/basepath${process.env.TRAILING_SLASH?.toLowerCase() === 'true' ? '/' : ''}`,
   server: {
     port: 3000,
   },
@@ -14,7 +30,9 @@ export default defineConfig({
     tsConfigPaths({
       projects: ['./tsconfig.json'],
     }),
-    tanstackStart(),
+    tanstackStart({
+      prerender: isPrerender ? prerenderConfiguration : undefined,
+    }),
     viteSolid({ ssr: true }),
   ],
 })
diff --git a/e2e/vue-start/custom-basepath/package.json b/e2e/vue-start/custom-basepath/package.json
index a4b30785ab3..3583de0de4d 100644
--- a/e2e/vue-start/custom-basepath/package.json
+++ b/e2e/vue-start/custom-basepath/package.json
@@ -6,9 +6,16 @@
   "scripts": {
     "dev": "cross-env NODE_ENV=development tsx express-server.ts",
     "build": "vite build && tsc --noEmit",
+    "build:prerender": "MODE=prerender vite build && tsc --noEmit",
+    "build:prerender:trailing": "MODE=prerender TRAILING_SLASH=true vite build && tsc --noEmit",
     "preview": "vite preview",
     "start": "tsx express-server.ts",
-    "test:e2e": "rm -rf port*.txt; playwright test --project=chromium"
+    "test:e2e:startDummyServer": "node -e 'import(\"./tests/setup/global.setup.ts\").then(m => m.default())' &",
+    "test:e2e:stopDummyServer": "node -e 'import(\"./tests/setup/global.teardown.ts\").then(m => m.default())'",
+    "test:e2e:prerender": "rm -rf port*.txt; MODE=prerender playwright test --project=chromium",
+    "test:e2e:prerender:trailing": "rm -rf port*.txt; MODE=prerender TRAILING_SLASH=true playwright test --project=chromium",
+    "test:e2e:ssrMode": "rm -rf port*.txt; playwright test --project=chromium",
+    "test:e2e": "pnpm run test:e2e:ssrMode && pnpm run test:e2e:prerender && pnpm run test:e2e:prerender:trailing"
   },
   "dependencies": {
     "@tanstack/vue-router": "workspace:^",
diff --git a/e2e/vue-start/custom-basepath/playwright.config.ts b/e2e/vue-start/custom-basepath/playwright.config.ts
index 5095425f473..17c013aaa6c 100644
--- a/e2e/vue-start/custom-basepath/playwright.config.ts
+++ b/e2e/vue-start/custom-basepath/playwright.config.ts
@@ -4,11 +4,36 @@ import {
   getTestServerPort,
 } from '@tanstack/router-e2e-utils'
 import packageJson from './package.json' with { type: 'json' }
+import { isPrerender } from './tests/utils/isPrerender'
 
 const PORT = await getTestServerPort(packageJson.name)
+const START_PORT = await getTestServerPort(packageJson.name)
 const EXTERNAL_PORT = await getDummyServerPort(packageJson.name)
 const baseURL = `http://localhost:${PORT}/custom/basepath`
 
+const ssrModeCommand = `pnpm build && pnpm start`
+const prerenderModeCommand = `pnpm run test:e2e:startDummyServer && pnpm build:prerender && pnpm run test:e2e:stopDummyServer && pnpm start`
+const prerenderTrailingModeCommand = `pnpm run test:e2e:startDummyServer && pnpm build:prerender:trailing && pnpm run test:e2e:stopDummyServer && pnpm start`
+const isTrailingSlashPrerender =
+  process.env.TRAILING_SLASH?.toLowerCase() === 'true'
+
+const getCommand = () => {
+  if (isPrerender && isTrailingSlashPrerender)
+    return prerenderTrailingModeCommand
+  if (isPrerender) return prerenderModeCommand
+  return ssrModeCommand
+}
+
+console.log(
+  'running in prerender mode: ',
+  isPrerender.toString(),
+  isPrerender
+    ? isTrailingSlashPrerender
+      ? 'with trailing slash'
+      : 'without trailing slash'
+    : '',
+)
+
 /**
  * See https://playwright.dev/docs/test-configuration.
  */
@@ -27,10 +52,20 @@ export default defineConfig({
   },
 
   webServer: {
-    command: `VITE_NODE_ENV="test" VITE_EXTERNAL_PORT=${EXTERNAL_PORT} pnpm build && VITE_NODE_ENV="test" VITE_EXTERNAL_PORT=${EXTERNAL_PORT} VITE_SERVER_PORT=${PORT} PORT=${PORT} pnpm start`,
+    command: getCommand(),
     url: baseURL,
     reuseExistingServer: !process.env.CI,
     stdout: 'pipe',
+    env: {
+      MODE: process.env.MODE || '',
+      TRAILING_SLASH: isTrailingSlashPrerender.toString(),
+      VITE_TRAILING_SLASH: isTrailingSlashPrerender.toString(),
+      VITE_NODE_ENV: 'test',
+      VITE_EXTERNAL_PORT: String(EXTERNAL_PORT),
+      VITE_SERVER_PORT: String(PORT),
+      START_PORT: String(START_PORT),
+      PORT: String(PORT),
+    },
   },
 
   projects: [
diff --git a/e2e/vue-start/custom-basepath/src/router.tsx b/e2e/vue-start/custom-basepath/src/router.tsx
index 81103bf0bd6..33ff448cb86 100644
--- a/e2e/vue-start/custom-basepath/src/router.tsx
+++ b/e2e/vue-start/custom-basepath/src/router.tsx
@@ -2,7 +2,6 @@ import { createRouter } from '@tanstack/vue-router'
 import { routeTree } from './routeTree.gen'
 import { DefaultCatchBoundary } from './components/DefaultCatchBoundary'
 import { NotFound } from './components/NotFound'
-import { basepath } from './utils/basepath'
 
 export function getRouter() {
   const router = createRouter({
@@ -11,7 +10,7 @@ export function getRouter() {
     defaultErrorComponent: DefaultCatchBoundary,
     defaultNotFoundComponent: () => <NotFound />,
     scrollRestoration: true,
-    basepath: basepath,
+    basepath: import.meta.env.BASE_URL,
   })
 
   return router
diff --git a/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx b/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx
index fb7fce5f4c4..1fdbe55f02e 100644
--- a/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx
+++ b/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx
@@ -1,15 +1,17 @@
 import { createFileRoute } from '@tanstack/vue-router'
+import { getRouterInstance } from '@tanstack/vue-start'
 import axios from 'redaxios'
-
 import type { User } from '~/utils/users'
 import { NotFound } from '~/components/NotFound'
 import { UserErrorComponent } from '~/components/UserErrorComponent'
-import { basepath } from '~/utils/basepath'
 
 export const Route = createFileRoute('/users/$userId')({
   loader: async ({ params: { userId } }) => {
+    const router = await getRouterInstance()
     return await axios
-      .get<User>(basepath + '/api/users/' + userId)
+      .get<User>('/api/users/' + userId, {
+        baseURL: router.options.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch user')
diff --git a/e2e/vue-start/custom-basepath/src/routes/users.tsx b/e2e/vue-start/custom-basepath/src/routes/users.tsx
index 1432e504516..33f01eaccbc 100644
--- a/e2e/vue-start/custom-basepath/src/routes/users.tsx
+++ b/e2e/vue-start/custom-basepath/src/routes/users.tsx
@@ -1,12 +1,15 @@
 import { Link, Outlet, createFileRoute } from '@tanstack/vue-router'
+import { getRouterInstance } from '@tanstack/vue-start'
 import axios from 'redaxios'
 import type { User } from '~/utils/users'
-import { basepath } from '~/utils/basepath'
 
 export const Route = createFileRoute('/users')({
   loader: async () => {
+    const router = await getRouterInstance()
     return await axios
-      .get<Array<User>>(basepath + '/api/users')
+      .get<Array<User>>('/api/users', {
+        baseURL: router.options.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch users')
diff --git a/e2e/vue-start/custom-basepath/src/utils/basepath.ts b/e2e/vue-start/custom-basepath/src/utils/basepath.ts
deleted file mode 100644
index 6e719f196cf..00000000000
--- a/e2e/vue-start/custom-basepath/src/utils/basepath.ts
+++ /dev/null
@@ -1 +0,0 @@
-export const basepath = '/custom/basepath'
diff --git a/e2e/vue-start/custom-basepath/tests/navigation.spec.ts b/e2e/vue-start/custom-basepath/tests/navigation.spec.ts
index e238134d2ed..fb1d2f1367e 100644
--- a/e2e/vue-start/custom-basepath/tests/navigation.spec.ts
+++ b/e2e/vue-start/custom-basepath/tests/navigation.spec.ts
@@ -1,4 +1,5 @@
 import { expect, test } from '@playwright/test'
+import { isPrerender } from './utils/isPrerender'
 
 test('Navigating to post', async ({ page }) => {
   await page.goto('/')
@@ -58,7 +59,12 @@ test('server-side redirect', async ({ page, baseURL }) => {
   await page.waitForLoadState('networkidle')
 
   expect(await page.getByTestId('post-view').isVisible()).toBe(true)
-  expect(page.url()).toBe(`${baseURL}/posts/1`)
+
+  if (isPrerender) {
+    expect(page.url()).toBe(`${baseURL}/posts/1/`)
+  } else {
+    expect(page.url()).toBe(`${baseURL}/posts/1`)
+  }
 
   // do not follow redirects since we want to test the Location header
   // Both requests (with or without basepath) should redirect directly to the final destination.
diff --git a/e2e/vue-start/custom-basepath/tests/utils/isPrerender.ts b/e2e/vue-start/custom-basepath/tests/utils/isPrerender.ts
new file mode 100644
index 00000000000..d5d991d4545
--- /dev/null
+++ b/e2e/vue-start/custom-basepath/tests/utils/isPrerender.ts
@@ -0,0 +1 @@
+export const isPrerender: boolean = process.env.MODE === 'prerender'
diff --git a/e2e/vue-start/custom-basepath/vite.config.ts b/e2e/vue-start/custom-basepath/vite.config.ts
index 4d6e769fe88..6c926f13e76 100644
--- a/e2e/vue-start/custom-basepath/vite.config.ts
+++ b/e2e/vue-start/custom-basepath/vite.config.ts
@@ -4,9 +4,25 @@ import { tanstackStart } from '@tanstack/vue-start/plugin/vite'
 import vue from '@vitejs/plugin-vue'
 import vueJsx from '@vitejs/plugin-vue-jsx'
 import tailwindcss from '@tailwindcss/vite'
+import { isPrerender } from './tests/utils/isPrerender'
+
+const prerenderConfiguration = {
+  enabled: true,
+  filter: (page: { path: string }) => {
+    return ![
+      '/i-do-not-exist',
+      '/this-route-does-not-exist',
+      '/redirect',
+      '/users',
+    ].some((p) => page.path.includes(p))
+  },
+  onSuccess: ({ page }: { page: { path: string } }) => {
+    console.log(`Rendered ${page.path}!`)
+  },
+}
 
 export default defineConfig({
-  base: '/custom/basepath',
+  base: `/custom/basepath${process.env.TRAILING_SLASH?.toLowerCase() === 'true' ? '/' : ''}`,
   server: {
     port: 3000,
   },
@@ -15,7 +31,9 @@ export default defineConfig({
     tsConfigPaths({
       projects: ['./tsconfig.json'],
     }),
-    tanstackStart(),
+    tanstackStart({
+      prerender: isPrerender ? prerenderConfiguration : undefined,
+    }),
     vue(),
     vueJsx(),
   ],

From b4b41dd011ef461ff32001b9fb6597167eb5c3a4 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Thu, 25 Dec 2025 15:03:00 +0200
Subject: [PATCH 04/10] use cross-env

---
 e2e/react-start/custom-basepath/package.json | 8 ++++----
 e2e/solid-start/custom-basepath/package.json | 8 ++++----
 e2e/vue-start/custom-basepath/package.json   | 8 ++++----
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/e2e/react-start/custom-basepath/package.json b/e2e/react-start/custom-basepath/package.json
index c5262d3673c..ff1c29bf6e6 100644
--- a/e2e/react-start/custom-basepath/package.json
+++ b/e2e/react-start/custom-basepath/package.json
@@ -6,14 +6,14 @@
   "scripts": {
     "dev": "cross-env NODE_ENV=development tsx express-server.ts",
     "build": "vite build && tsc --noEmit",
-    "build:prerender": "MODE=prerender vite build && tsc --noEmit",
-    "build:prerender:trailing": "MODE=prerender TRAILING_SLASH=true vite build && tsc --noEmit",
+    "build:prerender": "cross-env MODE=prerender vite build && tsc --noEmit",
+    "build:prerender:trailing": "cross-env MODE=prerender TRAILING_SLASH=true vite build && tsc --noEmit",
     "preview": "vite preview",
     "start": "tsx express-server.ts",
     "test:e2e:startDummyServer": "node -e 'import(\"./tests/setup/global.setup.ts\").then(m => m.default())' &",
     "test:e2e:stopDummyServer": "node -e 'import(\"./tests/setup/global.teardown.ts\").then(m => m.default())'",
-    "test:e2e:prerender": "rm -rf port*.txt; MODE=prerender playwright test --project=chromium",
-    "test:e2e:prerender:trailing": "rm -rf port*.txt; MODE=prerender TRAILING_SLASH=true playwright test --project=chromium",
+    "test:e2e:prerender": "rm -rf port*.txt; cross-env MODE=prerender playwright test --project=chromium",
+    "test:e2e:prerender:trailing": "rm -rf port*.txt; cross-env MODE=prerender TRAILING_SLASH=true playwright test --project=chromium",
     "test:e2e:ssrMode": "rm -rf port*.txt; playwright test --project=chromium",
     "test:e2e": "pnpm run test:e2e:ssrMode && pnpm run test:e2e:prerender && pnpm run test:e2e:prerender:trailing"
   },
diff --git a/e2e/solid-start/custom-basepath/package.json b/e2e/solid-start/custom-basepath/package.json
index cd19493acf8..eba00787c52 100644
--- a/e2e/solid-start/custom-basepath/package.json
+++ b/e2e/solid-start/custom-basepath/package.json
@@ -6,14 +6,14 @@
   "scripts": {
     "dev": "cross-env NODE_ENV=development tsx express-server.ts",
     "build": "vite build && tsc --noEmit",
-    "build:prerender": "MODE=prerender vite build && tsc --noEmit",
-    "build:prerender:trailing": "MODE=prerender TRAILING_SLASH=true vite build && tsc --noEmit",
+    "build:prerender": "cross-env MODE=prerender vite build && tsc --noEmit",
+    "build:prerender:trailing": "cross-env MODE=prerender TRAILING_SLASH=true vite build && tsc --noEmit",
     "preview": "vite preview",
     "start": "tsx express-server.ts",
     "test:e2e:startDummyServer": "node -e 'import(\"./tests/setup/global.setup.ts\").then(m => m.default())' &",
     "test:e2e:stopDummyServer": "node -e 'import(\"./tests/setup/global.teardown.ts\").then(m => m.default())'",
-    "test:e2e:prerender": "rm -rf port*.txt; MODE=prerender playwright test --project=chromium",
-    "test:e2e:prerender:trailing": "rm -rf port*.txt; MODE=prerender TRAILING_SLASH=true playwright test --project=chromium",
+    "test:e2e:prerender": "rm -rf port*.txt; cross-env MODE=prerender playwright test --project=chromium",
+    "test:e2e:prerender:trailing": "rm -rf port*.txt; cross-env MODE=prerender TRAILING_SLASH=true playwright test --project=chromium",
     "test:e2e:ssrMode": "rm -rf port*.txt; playwright test --project=chromium",
     "test:e2e": "pnpm run test:e2e:ssrMode && pnpm run test:e2e:prerender && pnpm run test:e2e:prerender:trailing"
   },
diff --git a/e2e/vue-start/custom-basepath/package.json b/e2e/vue-start/custom-basepath/package.json
index 3583de0de4d..d93af7e9f1b 100644
--- a/e2e/vue-start/custom-basepath/package.json
+++ b/e2e/vue-start/custom-basepath/package.json
@@ -6,14 +6,14 @@
   "scripts": {
     "dev": "cross-env NODE_ENV=development tsx express-server.ts",
     "build": "vite build && tsc --noEmit",
-    "build:prerender": "MODE=prerender vite build && tsc --noEmit",
-    "build:prerender:trailing": "MODE=prerender TRAILING_SLASH=true vite build && tsc --noEmit",
+    "build:prerender": "cross-env MODE=prerender vite build && tsc --noEmit",
+    "build:prerender:trailing": "cross-env MODE=prerender TRAILING_SLASH=true vite build && tsc --noEmit",
     "preview": "vite preview",
     "start": "tsx express-server.ts",
     "test:e2e:startDummyServer": "node -e 'import(\"./tests/setup/global.setup.ts\").then(m => m.default())' &",
     "test:e2e:stopDummyServer": "node -e 'import(\"./tests/setup/global.teardown.ts\").then(m => m.default())'",
-    "test:e2e:prerender": "rm -rf port*.txt; MODE=prerender playwright test --project=chromium",
-    "test:e2e:prerender:trailing": "rm -rf port*.txt; MODE=prerender TRAILING_SLASH=true playwright test --project=chromium",
+    "test:e2e:prerender": "rm -rf port*.txt; cross-env MODE=prerender playwright test --project=chromium",
+    "test:e2e:prerender:trailing": "rm -rf port*.txt; cross-env MODE=prerender TRAILING_SLASH=true playwright test --project=chromium",
     "test:e2e:ssrMode": "rm -rf port*.txt; playwright test --project=chromium",
     "test:e2e": "pnpm run test:e2e:ssrMode && pnpm run test:e2e:prerender && pnpm run test:e2e:prerender:trailing"
   },

From 723a69d9d66f5e98575394d95bc791af0fe66340 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Fri, 26 Dec 2025 13:24:45 +0200
Subject: [PATCH 05/10] exclude posts from prerender

---
 e2e/react-start/custom-basepath/vite.config.ts | 3 ++-
 e2e/solid-start/custom-basepath/vite.config.ts | 3 ++-
 e2e/vue-start/custom-basepath/vite.config.ts   | 3 ++-
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/e2e/react-start/custom-basepath/vite.config.ts b/e2e/react-start/custom-basepath/vite.config.ts
index fe5c8910c93..32a7643ca2b 100644
--- a/e2e/react-start/custom-basepath/vite.config.ts
+++ b/e2e/react-start/custom-basepath/vite.config.ts
@@ -10,8 +10,9 @@ const prerenderConfiguration = {
   filter: (page: { path: string }) => {
     return ![
       '/i-do-not-exist',
-      '/this-route-does-not-exist',
+      '/posts',
       '/redirect',
+      '/this-route-does-not-exist',
       '/users',
     ].some((p) => page.path.includes(p))
   },
diff --git a/e2e/solid-start/custom-basepath/vite.config.ts b/e2e/solid-start/custom-basepath/vite.config.ts
index ef8785cab39..d35cd033419 100644
--- a/e2e/solid-start/custom-basepath/vite.config.ts
+++ b/e2e/solid-start/custom-basepath/vite.config.ts
@@ -10,8 +10,9 @@ const prerenderConfiguration = {
   filter: (page: { path: string }) => {
     return ![
       '/i-do-not-exist',
-      '/this-route-does-not-exist',
+      '/posts',
       '/redirect',
+      '/this-route-does-not-exist',
       '/users',
     ].some((p) => page.path.includes(p))
   },
diff --git a/e2e/vue-start/custom-basepath/vite.config.ts b/e2e/vue-start/custom-basepath/vite.config.ts
index 6c926f13e76..5ed7688f7f3 100644
--- a/e2e/vue-start/custom-basepath/vite.config.ts
+++ b/e2e/vue-start/custom-basepath/vite.config.ts
@@ -11,8 +11,9 @@ const prerenderConfiguration = {
   filter: (page: { path: string }) => {
     return ![
       '/i-do-not-exist',
-      '/this-route-does-not-exist',
+      '/posts',
       '/redirect',
+      '/this-route-does-not-exist',
       '/users',
     ].some((p) => page.path.includes(p))
   },

From b08805ec46a4d8667fe8cc601f14fa2e08bae6b6 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Sun, 28 Dec 2025 04:34:51 +0200
Subject: [PATCH 06/10] resolve issues with vite preview

---
 packages/router-core/src/rewrite.ts           | 23 ++++++++-------
 packages/router-core/src/router.ts            |  9 +++++-
 .../src/createStartHandler.ts                 | 29 ++++++++++++++-----
 3 files changed, 42 insertions(+), 19 deletions(-)

diff --git a/packages/router-core/src/rewrite.ts b/packages/router-core/src/rewrite.ts
index 0da50c5b620..01581799c34 100644
--- a/packages/router-core/src/rewrite.ts
+++ b/packages/router-core/src/rewrite.ts
@@ -26,21 +26,19 @@ export function rewriteBasepath(opts: {
   basepath: string
   caseSensitive?: boolean
 }) {
+  const normalizePathCase = (path: string) => {
+    return opts.caseSensitive ? path : path.toLowerCase()
+  }
+
   const trimmedBasepath = trimPath(opts.basepath)
   const normalizedBasepath = `/${trimmedBasepath}`
   const normalizedBasepathWithSlash = `${normalizedBasepath}/`
-  const checkBasepath = opts.caseSensitive
-    ? normalizedBasepath
-    : normalizedBasepath.toLowerCase()
-  const checkBasepathWithSlash = opts.caseSensitive
-    ? normalizedBasepathWithSlash
-    : normalizedBasepathWithSlash.toLowerCase()
+  const checkBasepath = normalizePathCase(normalizedBasepath)
+  const checkBasepathWithSlash = normalizePathCase(normalizedBasepathWithSlash)
 
   return {
     input: ({ url }) => {
-      const pathname = opts.caseSensitive
-        ? url.pathname
-        : url.pathname.toLowerCase()
+      const pathname = normalizePathCase(url.pathname)
 
       // Handle exact basepath match (e.g., /my-app -> /)
       if (pathname === checkBasepath) {
@@ -52,7 +50,12 @@ export function rewriteBasepath(opts: {
       return url
     },
     output: ({ url }) => {
-      url.pathname = joinPaths(['/', trimmedBasepath, url.pathname])
+      const pathname = normalizePathCase(url.pathname)
+      const base = pathname.startsWith(checkBasepathWithSlash)
+        ? ''
+        : trimmedBasepath
+
+      url.pathname = joinPaths(['/', base, url.pathname])
       return url
     },
   } satisfies LocationRewrite
diff --git a/packages/router-core/src/router.ts b/packages/router-core/src/router.ts
index d9d808a3185..31128a03d13 100644
--- a/packages/router-core/src/router.ts
+++ b/packages/router-core/src/router.ts
@@ -1187,10 +1187,17 @@ export class RouterCore<
       url.search = searchStr
 
       const fullPath = url.href.replace(url.origin, '')
+      let publicHref = href
+
+      if (this.isServer) {
+        const urlForOutput = new URL(url.href)
+        const rewrittenUrl = executeRewriteOutput(this.rewrite, urlForOutput)
+        publicHref = rewrittenUrl.href.replace(rewrittenUrl.origin, '')
+      }
 
       return {
         href: fullPath,
-        publicHref: href,
+        publicHref: publicHref,
         url: url,
         pathname: decodePath(url.pathname),
         searchStr,
diff --git a/packages/start-server-core/src/createStartHandler.ts b/packages/start-server-core/src/createStartHandler.ts
index b0984b32751..0191675f6e2 100644
--- a/packages/start-server-core/src/createStartHandler.ts
+++ b/packages/start-server-core/src/createStartHandler.ts
@@ -2,6 +2,7 @@ import { createMemoryHistory } from '@tanstack/history'
 import { flattenMiddlewares, mergeHeaders } from '@tanstack/start-client-core'
 import {
   executeRewriteInput,
+  executeRewriteOutput,
   isRedirect,
   isResolvedRedirect,
 } from '@tanstack/router-core'
@@ -138,19 +139,32 @@ export function createStartHandler<TRegister = Register>(
 
       const requestHandlerMiddleware = handlerToMiddleware(
         async ({ context }) => {
+          const router = await getRouter()
+
+          let req = request
+          let publicHref = href
+
+          if (router.isServer) {
+            const rewrittenUrl = executeRewriteOutput(router.rewrite, url)
+            publicHref = rewrittenUrl.href.replace(rewrittenUrl.origin, '')
+            if (publicHref !== href) {
+              req = new Request(rewrittenUrl, request)
+            }
+          }
+
           const response = await runWithStartContext(
             {
               getRouter,
               startOptions: requestStartOptions,
               contextAfterGlobalMiddlewares: context,
-              request,
+              request: req,
             },
             async () => {
               try {
                 // First, let's attempt to handle server functions
-                if (href.startsWith(process.env.TSS_SERVER_FN_BASE)) {
+                if (publicHref.startsWith(process.env.TSS_SERVER_FN_BASE)) {
                   return await handleServerAction({
-                    request,
+                    request: req,
                     context: requestOpts?.context,
                   })
                 }
@@ -160,8 +174,7 @@ export function createStartHandler<TRegister = Register>(
                 }: {
                   serverContext: any
                 }) => {
-                  const requestAcceptHeader =
-                    request.headers.get('Accept') || '*/*'
+                  const requestAcceptHeader = req.headers.get('Accept') || '*/*'
                   const splitRequestAcceptHeader =
                     requestAcceptHeader.split(',')
 
@@ -188,7 +201,7 @@ export function createStartHandler<TRegister = Register>(
                   if (startRoutesManifest === null) {
                     startRoutesManifest = await getStartManifest()
                   }
-                  const router = await getRouter()
+
                   attachRouterServerSsrUtils({
                     router,
                     manifest: startRoutesManifest,
@@ -208,7 +221,7 @@ export function createStartHandler<TRegister = Register>(
                   // Mark that the callback will handle cleanup
                   cbWillCleanup = true
                   const response = await cb({
-                    request,
+                    request: req,
                     router,
                     responseHeaders,
                   })
@@ -218,7 +231,7 @@ export function createStartHandler<TRegister = Register>(
 
                 const response = await handleServerRoutes({
                   getRouter,
-                  request,
+                  request: req,
                   executeRouter,
                   context,
                 })

From 46c0efe78f6d058fcf8c0fffb961386397a78a05 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Sun, 28 Dec 2025 04:35:05 +0200
Subject: [PATCH 07/10] clean up tests

---
 .../custom-basepath/src/routes/users.$userId.tsx       |  4 +---
 e2e/react-start/custom-basepath/src/routes/users.tsx   |  4 +---
 .../custom-basepath/tests/navigation.spec.ts           | 10 ++--------
 .../custom-basepath/src/routes/users.$userId.tsx       |  4 +---
 e2e/solid-start/custom-basepath/src/routes/users.tsx   |  4 +---
 .../custom-basepath/tests/navigation.spec.ts           | 10 ++--------
 .../custom-basepath/src/routes/users.$userId.tsx       |  4 +---
 e2e/vue-start/custom-basepath/src/routes/users.tsx     |  4 +---
 e2e/vue-start/custom-basepath/tests/navigation.spec.ts | 10 ++--------
 9 files changed, 12 insertions(+), 42 deletions(-)

diff --git a/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx b/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx
index 104703bf303..d1b4977922d 100644
--- a/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx
+++ b/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx
@@ -9,9 +9,7 @@ export const Route = createFileRoute('/users/$userId')({
   loader: async ({ params: { userId } }) => {
     const router = await getRouterInstance()
     return await axios
-      .get<User>('/api/users/' + userId, {
-        baseURL: router.options.origin,
-      })
+      .get<User>(`/${router.options.basepath}/api/users/${userId}`)
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch user')
diff --git a/e2e/react-start/custom-basepath/src/routes/users.tsx b/e2e/react-start/custom-basepath/src/routes/users.tsx
index a7b5a1d316a..03308b3a1be 100644
--- a/e2e/react-start/custom-basepath/src/routes/users.tsx
+++ b/e2e/react-start/custom-basepath/src/routes/users.tsx
@@ -7,9 +7,7 @@ export const Route = createFileRoute('/users')({
   loader: async () => {
     const router = await getRouterInstance()
     return await axios
-      .get<Array<User>>('/api/users', {
-        baseURL: router.options.origin,
-      })
+      .get<Array<User>>(`/${router.options.basepath}/api/users`)
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch users')
diff --git a/e2e/react-start/custom-basepath/tests/navigation.spec.ts b/e2e/react-start/custom-basepath/tests/navigation.spec.ts
index 5962658134e..fba5af53848 100644
--- a/e2e/react-start/custom-basepath/tests/navigation.spec.ts
+++ b/e2e/react-start/custom-basepath/tests/navigation.spec.ts
@@ -1,5 +1,4 @@
 import { expect, test } from '@playwright/test'
-import { isPrerender } from './utils/isPrerender'
 
 test('Navigating to post', async ({ page }) => {
   await page.goto('/')
@@ -59,12 +58,7 @@ test('server-side redirect', async ({ page, baseURL }) => {
   await page.waitForLoadState('networkidle')
 
   expect(await page.getByTestId('post-view').isVisible()).toBe(true)
-
-  if (isPrerender) {
-    expect(page.url()).toBe(`${baseURL}/posts/1/`)
-  } else {
-    expect(page.url()).toBe(`${baseURL}/posts/1`)
-  }
+  expect(page.url()).toBe(`${baseURL}/posts/1`)
 
   // do not follow redirects since we want to test the Location header
   // first go to the route WITHOUT the base path, this will just add the base path
@@ -72,7 +66,7 @@ test('server-side redirect', async ({ page, baseURL }) => {
     .get('/redirect/throw-it', { maxRedirects: 0 })
     .then((res) => {
       const headers = new Headers(res.headers())
-      expect(headers.get('location')).toBe('/custom/basepath/redirect/throw-it')
+      expect(headers.get('location')).toBe('/custom/basepath/posts/1')
     })
   await page.request
     .get('/custom/basepath/redirect/throw-it', { maxRedirects: 0 })
diff --git a/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx b/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx
index dcb0e1d28fe..a59fc3b0f2a 100644
--- a/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx
+++ b/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx
@@ -9,9 +9,7 @@ export const Route = createFileRoute('/users/$userId')({
   loader: async ({ params: { userId } }) => {
     const router = await getRouterInstance()
     return await axios
-      .get<User>('/api/users/' + userId, {
-        baseURL: router.options.origin,
-      })
+      .get<User>(`/${router.options.basepath}/api/users/${userId}`)
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch user')
diff --git a/e2e/solid-start/custom-basepath/src/routes/users.tsx b/e2e/solid-start/custom-basepath/src/routes/users.tsx
index d1d312df3ee..0666a0536ce 100644
--- a/e2e/solid-start/custom-basepath/src/routes/users.tsx
+++ b/e2e/solid-start/custom-basepath/src/routes/users.tsx
@@ -7,9 +7,7 @@ export const Route = createFileRoute('/users')({
   loader: async () => {
     const router = await getRouterInstance()
     return await axios
-      .get<Array<User>>('/api/users', {
-        baseURL: router.options.origin,
-      })
+      .get<Array<User>>(`/${router.options.basepath}/api/users`)
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch users')
diff --git a/e2e/solid-start/custom-basepath/tests/navigation.spec.ts b/e2e/solid-start/custom-basepath/tests/navigation.spec.ts
index 5962658134e..fba5af53848 100644
--- a/e2e/solid-start/custom-basepath/tests/navigation.spec.ts
+++ b/e2e/solid-start/custom-basepath/tests/navigation.spec.ts
@@ -1,5 +1,4 @@
 import { expect, test } from '@playwright/test'
-import { isPrerender } from './utils/isPrerender'
 
 test('Navigating to post', async ({ page }) => {
   await page.goto('/')
@@ -59,12 +58,7 @@ test('server-side redirect', async ({ page, baseURL }) => {
   await page.waitForLoadState('networkidle')
 
   expect(await page.getByTestId('post-view').isVisible()).toBe(true)
-
-  if (isPrerender) {
-    expect(page.url()).toBe(`${baseURL}/posts/1/`)
-  } else {
-    expect(page.url()).toBe(`${baseURL}/posts/1`)
-  }
+  expect(page.url()).toBe(`${baseURL}/posts/1`)
 
   // do not follow redirects since we want to test the Location header
   // first go to the route WITHOUT the base path, this will just add the base path
@@ -72,7 +66,7 @@ test('server-side redirect', async ({ page, baseURL }) => {
     .get('/redirect/throw-it', { maxRedirects: 0 })
     .then((res) => {
       const headers = new Headers(res.headers())
-      expect(headers.get('location')).toBe('/custom/basepath/redirect/throw-it')
+      expect(headers.get('location')).toBe('/custom/basepath/posts/1')
     })
   await page.request
     .get('/custom/basepath/redirect/throw-it', { maxRedirects: 0 })
diff --git a/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx b/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx
index 1fdbe55f02e..1d663758e98 100644
--- a/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx
+++ b/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx
@@ -9,9 +9,7 @@ export const Route = createFileRoute('/users/$userId')({
   loader: async ({ params: { userId } }) => {
     const router = await getRouterInstance()
     return await axios
-      .get<User>('/api/users/' + userId, {
-        baseURL: router.options.origin,
-      })
+      .get<User>(`/${router.options.basepath}/api/users/${userId}`)
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch user')
diff --git a/e2e/vue-start/custom-basepath/src/routes/users.tsx b/e2e/vue-start/custom-basepath/src/routes/users.tsx
index 33f01eaccbc..9306c894af2 100644
--- a/e2e/vue-start/custom-basepath/src/routes/users.tsx
+++ b/e2e/vue-start/custom-basepath/src/routes/users.tsx
@@ -7,9 +7,7 @@ export const Route = createFileRoute('/users')({
   loader: async () => {
     const router = await getRouterInstance()
     return await axios
-      .get<Array<User>>('/api/users', {
-        baseURL: router.options.origin,
-      })
+      .get<Array<User>>(`/${router.options.basepath}/api/users`)
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch users')
diff --git a/e2e/vue-start/custom-basepath/tests/navigation.spec.ts b/e2e/vue-start/custom-basepath/tests/navigation.spec.ts
index 5962658134e..fba5af53848 100644
--- a/e2e/vue-start/custom-basepath/tests/navigation.spec.ts
+++ b/e2e/vue-start/custom-basepath/tests/navigation.spec.ts
@@ -1,5 +1,4 @@
 import { expect, test } from '@playwright/test'
-import { isPrerender } from './utils/isPrerender'
 
 test('Navigating to post', async ({ page }) => {
   await page.goto('/')
@@ -59,12 +58,7 @@ test('server-side redirect', async ({ page, baseURL }) => {
   await page.waitForLoadState('networkidle')
 
   expect(await page.getByTestId('post-view').isVisible()).toBe(true)
-
-  if (isPrerender) {
-    expect(page.url()).toBe(`${baseURL}/posts/1/`)
-  } else {
-    expect(page.url()).toBe(`${baseURL}/posts/1`)
-  }
+  expect(page.url()).toBe(`${baseURL}/posts/1`)
 
   // do not follow redirects since we want to test the Location header
   // first go to the route WITHOUT the base path, this will just add the base path
@@ -72,7 +66,7 @@ test('server-side redirect', async ({ page, baseURL }) => {
     .get('/redirect/throw-it', { maxRedirects: 0 })
     .then((res) => {
       const headers = new Headers(res.headers())
-      expect(headers.get('location')).toBe('/custom/basepath/redirect/throw-it')
+      expect(headers.get('location')).toBe('/custom/basepath/posts/1')
     })
   await page.request
     .get('/custom/basepath/redirect/throw-it', { maxRedirects: 0 })

From 1cbffe314b81a6cbaa67f28430ab23bc0805c6c3 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Sun, 28 Dec 2025 05:38:30 +0200
Subject: [PATCH 08/10] reapply fix with latest changes to createStartHandler

---
 packages/start-server-core/src/createStartHandler.ts | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/packages/start-server-core/src/createStartHandler.ts b/packages/start-server-core/src/createStartHandler.ts
index 1f2820c7f13..12fd4889351 100644
--- a/packages/start-server-core/src/createStartHandler.ts
+++ b/packages/start-server-core/src/createStartHandler.ts
@@ -9,6 +9,7 @@ import {
   executeRewriteInput,
   isRedirect,
   isResolvedRedirect,
+  joinPaths,
 } from '@tanstack/router-core'
 import {
   attachRouterServerSsrUtils,
@@ -210,6 +211,12 @@ export function createStartHandler<TRegister = Register>(
 
     try {
       const url = new URL(request.url)
+
+      if (!url.pathname.startsWith(joinPaths(['/', ROUTER_BASEPATH]))) {
+        url.pathname = joinPaths(['/', ROUTER_BASEPATH, url.pathname])
+        request = new Request(url, request)
+      }
+
       const href = url.href.replace(url.origin, '')
       const origin = getOrigin(request)
 

From 22595a1480ed9396aaf74276bea9ab6887aec111 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Sun, 28 Dec 2025 06:48:08 +0200
Subject: [PATCH 09/10] cleanup

---
 .../custom-basepath/src/routes/users.$userId.tsx         | 4 +++-
 e2e/react-start/custom-basepath/src/routes/users.tsx     | 4 +++-
 .../custom-basepath/src/routes/users.$userId.tsx         | 4 +++-
 e2e/solid-start/custom-basepath/src/routes/users.tsx     | 4 +++-
 .../custom-basepath/src/routes/users.$userId.tsx         | 4 +++-
 e2e/vue-start/custom-basepath/src/routes/users.tsx       | 4 +++-
 packages/router-core/src/router.ts                       | 9 +--------
 packages/start-server-core/src/createStartHandler.ts     | 5 +++--
 8 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx b/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx
index d1b4977922d..1741a80b939 100644
--- a/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx
+++ b/e2e/react-start/custom-basepath/src/routes/users.$userId.tsx
@@ -9,7 +9,9 @@ export const Route = createFileRoute('/users/$userId')({
   loader: async ({ params: { userId } }) => {
     const router = await getRouterInstance()
     return await axios
-      .get<User>(`/${router.options.basepath}/api/users/${userId}`)
+      .get<User>(`/${router.options.basepath}/api/users/${userId}`, {
+        baseURL: router.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch user')
diff --git a/e2e/react-start/custom-basepath/src/routes/users.tsx b/e2e/react-start/custom-basepath/src/routes/users.tsx
index 03308b3a1be..28d1e7caff9 100644
--- a/e2e/react-start/custom-basepath/src/routes/users.tsx
+++ b/e2e/react-start/custom-basepath/src/routes/users.tsx
@@ -7,7 +7,9 @@ export const Route = createFileRoute('/users')({
   loader: async () => {
     const router = await getRouterInstance()
     return await axios
-      .get<Array<User>>(`/${router.options.basepath}/api/users`)
+      .get<Array<User>>(`/${router.options.basepath}/api/users`, {
+        baseURL: router.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch users')
diff --git a/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx b/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx
index a59fc3b0f2a..29eeb3ad641 100644
--- a/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx
+++ b/e2e/solid-start/custom-basepath/src/routes/users.$userId.tsx
@@ -9,7 +9,9 @@ export const Route = createFileRoute('/users/$userId')({
   loader: async ({ params: { userId } }) => {
     const router = await getRouterInstance()
     return await axios
-      .get<User>(`/${router.options.basepath}/api/users/${userId}`)
+      .get<User>(`/${router.options.basepath}/api/users/${userId}`, {
+        baseURL: router.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch user')
diff --git a/e2e/solid-start/custom-basepath/src/routes/users.tsx b/e2e/solid-start/custom-basepath/src/routes/users.tsx
index 0666a0536ce..ee0fcda038f 100644
--- a/e2e/solid-start/custom-basepath/src/routes/users.tsx
+++ b/e2e/solid-start/custom-basepath/src/routes/users.tsx
@@ -7,7 +7,9 @@ export const Route = createFileRoute('/users')({
   loader: async () => {
     const router = await getRouterInstance()
     return await axios
-      .get<Array<User>>(`/${router.options.basepath}/api/users`)
+      .get<Array<User>>(`/${router.options.basepath}/api/users`, {
+        baseURL: router.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch users')
diff --git a/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx b/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx
index 1d663758e98..e3f84b79c9a 100644
--- a/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx
+++ b/e2e/vue-start/custom-basepath/src/routes/users.$userId.tsx
@@ -9,7 +9,9 @@ export const Route = createFileRoute('/users/$userId')({
   loader: async ({ params: { userId } }) => {
     const router = await getRouterInstance()
     return await axios
-      .get<User>(`/${router.options.basepath}/api/users/${userId}`)
+      .get<User>(`/${router.options.basepath}/api/users/${userId}`, {
+        baseURL: router.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch user')
diff --git a/e2e/vue-start/custom-basepath/src/routes/users.tsx b/e2e/vue-start/custom-basepath/src/routes/users.tsx
index 9306c894af2..09c11dad56e 100644
--- a/e2e/vue-start/custom-basepath/src/routes/users.tsx
+++ b/e2e/vue-start/custom-basepath/src/routes/users.tsx
@@ -7,7 +7,9 @@ export const Route = createFileRoute('/users')({
   loader: async () => {
     const router = await getRouterInstance()
     return await axios
-      .get<Array<User>>(`/${router.options.basepath}/api/users`)
+      .get<Array<User>>(`/${router.options.basepath}/api/users`, {
+        baseURL: router.origin,
+      })
       .then((r) => r.data)
       .catch(() => {
         throw new Error('Failed to fetch users')
diff --git a/packages/router-core/src/router.ts b/packages/router-core/src/router.ts
index 31128a03d13..d9d808a3185 100644
--- a/packages/router-core/src/router.ts
+++ b/packages/router-core/src/router.ts
@@ -1187,17 +1187,10 @@ export class RouterCore<
       url.search = searchStr
 
       const fullPath = url.href.replace(url.origin, '')
-      let publicHref = href
-
-      if (this.isServer) {
-        const urlForOutput = new URL(url.href)
-        const rewrittenUrl = executeRewriteOutput(this.rewrite, urlForOutput)
-        publicHref = rewrittenUrl.href.replace(rewrittenUrl.origin, '')
-      }
 
       return {
         href: fullPath,
-        publicHref: publicHref,
+        publicHref: href,
         url: url,
         pathname: decodePath(url.pathname),
         searchStr,
diff --git a/packages/start-server-core/src/createStartHandler.ts b/packages/start-server-core/src/createStartHandler.ts
index 12fd4889351..4649d324dc2 100644
--- a/packages/start-server-core/src/createStartHandler.ts
+++ b/packages/start-server-core/src/createStartHandler.ts
@@ -211,9 +211,10 @@ export function createStartHandler<TRegister = Register>(
 
     try {
       const url = new URL(request.url)
+      const basePath = joinPaths(['/', ROUTER_BASEPATH])
 
-      if (!url.pathname.startsWith(joinPaths(['/', ROUTER_BASEPATH]))) {
-        url.pathname = joinPaths(['/', ROUTER_BASEPATH, url.pathname])
+      if (!url.pathname.startsWith(basePath)) {
+        url.pathname = joinPaths([basePath, url.pathname])
         request = new Request(url, request)
       }
 

From 555faeeadf6f7324b80f0f41d4867c3f961a0aa1 Mon Sep 17 00:00:00 2001
From: Nico Lynzaad <nlynzaad@zylangroup.com>
Date: Sun, 28 Dec 2025 06:58:00 +0200
Subject: [PATCH 10/10] cleanup

---
 packages/router-core/src/rewrite.ts | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/packages/router-core/src/rewrite.ts b/packages/router-core/src/rewrite.ts
index 01581799c34..0da50c5b620 100644
--- a/packages/router-core/src/rewrite.ts
+++ b/packages/router-core/src/rewrite.ts
@@ -26,19 +26,21 @@ export function rewriteBasepath(opts: {
   basepath: string
   caseSensitive?: boolean
 }) {
-  const normalizePathCase = (path: string) => {
-    return opts.caseSensitive ? path : path.toLowerCase()
-  }
-
   const trimmedBasepath = trimPath(opts.basepath)
   const normalizedBasepath = `/${trimmedBasepath}`
   const normalizedBasepathWithSlash = `${normalizedBasepath}/`
-  const checkBasepath = normalizePathCase(normalizedBasepath)
-  const checkBasepathWithSlash = normalizePathCase(normalizedBasepathWithSlash)
+  const checkBasepath = opts.caseSensitive
+    ? normalizedBasepath
+    : normalizedBasepath.toLowerCase()
+  const checkBasepathWithSlash = opts.caseSensitive
+    ? normalizedBasepathWithSlash
+    : normalizedBasepathWithSlash.toLowerCase()
 
   return {
     input: ({ url }) => {
-      const pathname = normalizePathCase(url.pathname)
+      const pathname = opts.caseSensitive
+        ? url.pathname
+        : url.pathname.toLowerCase()
 
       // Handle exact basepath match (e.g., /my-app -> /)
       if (pathname === checkBasepath) {
@@ -50,12 +52,7 @@ export function rewriteBasepath(opts: {
       return url
     },
     output: ({ url }) => {
-      const pathname = normalizePathCase(url.pathname)
-      const base = pathname.startsWith(checkBasepathWithSlash)
-        ? ''
-        : trimmedBasepath
-
-      url.pathname = joinPaths(['/', base, url.pathname])
+      url.pathname = joinPaths(['/', trimmedBasepath, url.pathname])
       return url
     },
   } satisfies LocationRewrite