diff --git a/i18next-parser.config.ts b/i18next-parser.config.ts
index 3acf2b5e..e07021ae 100644
--- a/i18next-parser.config.ts
+++ b/i18next-parser.config.ts
@@ -1,4 +1,12 @@
-export default {
+/*
+Copyright 2024 New Vector Ltd.
+SPDX-License-Identifier: AGPL-3.0-only
+Please see LICENSE in the repository root for full details.
+*/
+
+import type { UserConfig } from "i18next-parser";
+
+const config: UserConfig = {
   keySeparator: ".",
   namespaceSeparator: false,
   contextSeparator: "|",
@@ -26,3 +34,5 @@ export default {
   input: ["src/**/*.{ts,tsx}"],
   sort: true,
 };
+
+export default config;
diff --git a/vite-embedded.config.js b/vite-embedded.config.ts
similarity index 84%
rename from vite-embedded.config.js
rename to vite-embedded.config.ts
index 8f5bcba8..27a42fbb 100644
--- a/vite-embedded.config.js
+++ b/vite-embedded.config.ts
@@ -1,7 +1,15 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
 import { defineConfig, mergeConfig } from "vite";
-import fullConfig from "./vite.config";
 import generateFile from "vite-plugin-generate-file";
 
+import fullConfig from "./vite.config";
+
 const base = "./";
 
 // Config for embedded deployments (possibly hosted under a non-root path)
diff --git a/vite.config.js b/vite.config.ts
similarity index 90%
rename from vite.config.js
rename to vite.config.ts
index 5fe3a99b..115565bb 100644
--- a/vite.config.js
+++ b/vite.config.ts
@@ -5,7 +5,12 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { defineConfig, loadEnv, searchForWorkspaceRoot } from "vite";
+import {
+  loadEnv,
+  searchForWorkspaceRoot,
+  type ConfigEnv,
+  type UserConfig,
+} from "vite";
 import svgrPlugin from "vite-plugin-svgr";
 import { createHtmlPlugin } from "vite-plugin-html";
 import { codecovVitePlugin } from "@codecov/vite-plugin";
@@ -13,12 +18,16 @@ import { sentryVitePlugin } from "@sentry/vite-plugin";
 import react from "@vitejs/plugin-react";
 import { realpathSync } from "fs";
 import * as fs from "node:fs";
-
+import { logger } from "matrix-js-sdk/lib/logger";
 // https://vitejs.dev/config/
-export default defineConfig(({ mode, packageType }) => {
+// Modified type helper from defineConfig to allow for packageType (see defineConfig from vite)
+export default ({
+  mode,
+  packageType,
+}: ConfigEnv & { packageType?: "full" | "embedded" }): UserConfig => {
   const env = loadEnv(mode, process.cwd());
   // Environment variables with the VITE_ prefix are accessible at runtime.
-  // So, we set this to allow for build/package specific behaviour.
+  // So, we set this to allow for build/package specific behavior.
   // In future we might be able to do what is needed via code splitting at
   // build time.
   process.env.VITE_PACKAGE = packageType ?? "full";
@@ -77,7 +86,7 @@ export default defineConfig(({ mode, packageType }) => {
       allow.push(realpathSync(path));
     } catch {}
   }
-  console.log("Allowed vite paths:", allow);
+  logger.log("Allowed vite paths:", allow);
 
   return {
     server: {
@@ -93,7 +102,7 @@ export default defineConfig(({ mode, packageType }) => {
       sourcemap: true,
       rollupOptions: {
         output: {
-          assetFileNames: ({ originalFileNames }) => {
+          assetFileNames: ({ originalFileNames }): string => {
             if (originalFileNames) {
               for (const name of originalFileNames) {
                 // Custom asset name for locales to include the locale code in the filename
@@ -143,4 +152,4 @@ export default defineConfig(({ mode, packageType }) => {
       exclude: ["@matrix-org/matrix-sdk-crypto-wasm"],
     },
   };
-});
+};
diff --git a/vitest.config.js b/vitest.config.ts
similarity index 81%
rename from vitest.config.js
rename to vitest.config.ts
index a6c3107f..ff8947b0 100644
--- a/vitest.config.js
+++ b/vitest.config.ts
@@ -1,5 +1,12 @@
+/*
+Copyright 2024 New Vector Ltd.
+SPDX-License-Identifier: AGPL-3.0-only
+Please see LICENSE in the repository root for full details.
+*/
+
 import { defineConfig, mergeConfig } from "vitest/config";
-import viteConfig from "./vite.config.js";
+
+import viteConfig from "./vite.config";
 
 export default defineConfig((configEnv) =>
   mergeConfig(