From cdc7839fe0c462c6e5db34e62711d5d2f0f56faf Mon Sep 17 00:00:00 2001
From: Mark Dalgleish <mark.john.dalgleish@gmail.com>
Date: Thu, 11 Sep 2025 16:26:49 +1000
Subject: [PATCH 1/2] Remove resolved `unstable_rootRoute` config

---
 integration/vite-presets-test.ts             | 1 -
 packages/react-router-dev/config/config.ts   | 5 -----
 packages/react-router-dev/vite/rsc/plugin.ts | 2 +-
 3 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/integration/vite-presets-test.ts b/integration/vite-presets-test.ts
index 3c88154853..34a2c3933f 100644
--- a/integration/vite-presets-test.ts
+++ b/integration/vite-presets-test.ts
@@ -226,7 +226,6 @@ test.describe("Vite / presets", async () => {
         "serverBundles",
         "serverModuleFormat",
         "ssr",
-        "unstable_rootRouteFile",
         "unstable_routeConfig",
       ]);
 
diff --git a/packages/react-router-dev/config/config.ts b/packages/react-router-dev/config/config.ts
index 98353026b8..c0d92b2714 100644
--- a/packages/react-router-dev/config/config.ts
+++ b/packages/react-router-dev/config/config.ts
@@ -264,10 +264,6 @@ export type ResolvedReactRouterConfig = Readonly<{
    * SPA without server-rendering. Default's to `true`.
    */
   ssr: boolean;
-  /**
-   * The absolute path to the root route file.
-   */
-  unstable_rootRouteFile: string;
   /**
    * The resolved array of route config entries exported from `routes.ts`
    */
@@ -615,7 +611,6 @@ async function resolveConfig({
     serverBundles,
     serverModuleFormat,
     ssr,
-    unstable_rootRouteFile: rootRouteFile,
     unstable_routeConfig: routeConfig,
   } satisfies ResolvedReactRouterConfig);
 
diff --git a/packages/react-router-dev/vite/rsc/plugin.ts b/packages/react-router-dev/vite/rsc/plugin.ts
index 202cfe4984..cdf65d09b6 100644
--- a/packages/react-router-dev/vite/rsc/plugin.ts
+++ b/packages/react-router-dev/vite/rsc/plugin.ts
@@ -315,7 +315,7 @@ export function reactRouterRSCVitePlugin(): Vite.PluginOption[] {
           id,
           viteCommand,
           routeIdByFile,
-          rootRouteFile: config.unstable_rootRouteFile,
+          rootRouteFile: config.routes.root.file,
           viteEnvironment: this.environment,
         });
       },

From e5d004d52a3f90f72cb8d0b04bea59cb3c4c2d27 Mon Sep 17 00:00:00 2001
From: Mark Dalgleish <mark.john.dalgleish@gmail.com>
Date: Thu, 11 Sep 2025 16:35:14 +1000
Subject: [PATCH 2/2] Resolve root route file path

---
 packages/react-router-dev/vite/rsc/plugin.ts | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/packages/react-router-dev/vite/rsc/plugin.ts b/packages/react-router-dev/vite/rsc/plugin.ts
index cdf65d09b6..dad5eafa01 100644
--- a/packages/react-router-dev/vite/rsc/plugin.ts
+++ b/packages/react-router-dev/vite/rsc/plugin.ts
@@ -1,5 +1,6 @@
 import type * as Vite from "vite";
 import { init as initEsModuleLexer } from "es-module-lexer";
+import * as Path from "pathe";
 import * as babel from "@babel/core";
 import colors from "picocolors";
 
@@ -28,7 +29,6 @@ import { warnOnClientSourceMaps } from "../plugins/warn-on-client-source-maps";
 
 export function reactRouterRSCVitePlugin(): Vite.PluginOption[] {
   let configLoader: ConfigLoader;
-  let config: ResolvedReactRouterConfig;
   let typegenWatcherPromise: Promise<Typegen.Watcher> | undefined;
   let viteCommand: Vite.ConfigEnv["command"];
   let routeIdByFile: Map<string, string> | undefined;
@@ -36,6 +36,16 @@ export function reactRouterRSCVitePlugin(): Vite.PluginOption[] {
 
   const defaultEntries = getDefaultEntries();
 
+  let config: ResolvedReactRouterConfig;
+  let rootRouteFile: string;
+  function updateConfig(newConfig: ResolvedReactRouterConfig) {
+    config = newConfig;
+    rootRouteFile = Path.resolve(
+      newConfig.appDirectory,
+      newConfig.routes.root.file,
+    );
+  }
+
   return [
     {
       name: "react-router/rsc",
@@ -75,7 +85,7 @@ export function reactRouterRSCVitePlugin(): Vite.PluginOption[] {
 
         const configResult = await configLoader.getConfig();
         if (!configResult.ok) throw new Error(configResult.error);
-        config = configResult.value;
+        updateConfig(configResult.value);
 
         if (
           viteUserConfig.base &&
@@ -246,7 +256,7 @@ export function reactRouterRSCVitePlugin(): Vite.PluginOption[] {
             });
 
             // Update shared plugin config reference
-            config = result.value;
+            updateConfig(result.value);
 
             if (configChanged || routeConfigChanged) {
               invalidateVirtualModules(viteDevServer);
@@ -315,7 +325,7 @@ export function reactRouterRSCVitePlugin(): Vite.PluginOption[] {
           id,
           viteCommand,
           routeIdByFile,
-          rootRouteFile: config.routes.root.file,
+          rootRouteFile,
           viteEnvironment: this.environment,
         });
       },