diff --git a/cli/src/helpers/createProject.ts b/cli/src/helpers/createProject.ts
index 81b385485f..92aa6ed49e 100644
--- a/cli/src/helpers/createProject.ts
+++ b/cli/src/helpers/createProject.ts
@@ -64,8 +64,8 @@ export const createProject = async ({
   if (appRouter) {
     // Replace next.config
     fs.copyFileSync(
-      path.join(PKG_ROOT, "template/extras/config/next-config-appdir.js"),
-      path.join(projectDir, "next.config.js")
+      path.join(PKG_ROOT, "template/extras/config/next-config-appdir.ts"),
+      path.join(projectDir, "next.config.ts")
     );
 
     selectLayoutFile({ projectDir, packages });
diff --git a/cli/src/installers/envVars.ts b/cli/src/installers/envVars.ts
index a7377ccf6e..281ea7e331 100644
--- a/cli/src/installers/envVars.ts
+++ b/cli/src/installers/envVars.ts
@@ -44,7 +44,7 @@ export const envVariablesInstaller: Installer = ({
       "template/extras/src/env",
       envFile
     );
-    const envSchemaDest = path.join(projectDir, "src/env.js");
+    const envSchemaDest = path.join(projectDir, "src/env.ts");
     fs.copyFileSync(envSchemaSrc, envSchemaDest);
   }
 
@@ -63,7 +63,7 @@ const getEnvContent = (
   scopedAppName: string
 ) => {
   let content = `
-# When adding additional environment variables, the schema in "/src/env.js"
+# When adding additional environment variables, the schema in "/src/env.ts"
 # should be updated accordingly.
 `
     .trim()
diff --git a/cli/template/base/next.config.js b/cli/template/base/next.config.ts
similarity index 55%
rename from cli/template/base/next.config.js
rename to cli/template/base/next.config.ts
index 98b6f90a51..a3c840a8ca 100644
--- a/cli/template/base/next.config.js
+++ b/cli/template/base/next.config.ts
@@ -1,23 +1,18 @@
+import { type NextConfig } from "next";
+
 /**
  * Run `build` or `dev` with `SKIP_ENV_VALIDATION` to skip env validation. This is especially useful
  * for Docker builds.
  */
-await import("./src/env.js");
+import "./src/env";
 
-/** @type {import("next").NextConfig} */
 const config = {
   reactStrictMode: true,
-
-  /**
-   * If you are using `appDir` then you must comment the below `i18n` config out.
-   *
-   * @see https://github.com/vercel/next.js/issues/41980
-   */
   i18n: {
     locales: ["en"],
     defaultLocale: "en",
   },
   transpilePackages: ["geist"],
-};
+} satisfies NextConfig;
 
 export default config;
diff --git a/cli/template/base/package.json b/cli/template/base/package.json
index fff75519f8..85dab873ef 100644
--- a/cli/template/base/package.json
+++ b/cli/template/base/package.json
@@ -16,7 +16,7 @@
   "dependencies": {
     "@t3-oss/env-nextjs": "^0.10.1",
     "geist": "^1.3.0",
-    "next": "^14.2.4",
+    "next": "^15.0.0",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
     "zod": "^3.23.3"
diff --git a/cli/template/base/src/env.js b/cli/template/base/src/env.ts
similarity index 100%
rename from cli/template/base/src/env.js
rename to cli/template/base/src/env.ts
diff --git a/cli/template/extras/config/next-config-appdir.js b/cli/template/extras/config/next-config-appdir.ts
similarity index 60%
rename from cli/template/extras/config/next-config-appdir.js
rename to cli/template/extras/config/next-config-appdir.ts
index 9bfe4a0e2a..812e25a83f 100644
--- a/cli/template/extras/config/next-config-appdir.js
+++ b/cli/template/extras/config/next-config-appdir.ts
@@ -1,10 +1,11 @@
+import { type NextConfig } from "next";
+
 /**
  * Run `build` or `dev` with `SKIP_ENV_VALIDATION` to skip env validation. This is especially useful
  * for Docker builds.
  */
-await import("./src/env.js");
+import "./src/env";
 
-/** @type {import("next").NextConfig} */
-const config = {};
+const config = {} satisfies NextConfig;
 
 export default config;