diff --git a/lib/extension/frontend.ts b/lib/extension/frontend.ts
index db0f4206c..576d714ff 100644
--- a/lib/extension/frontend.ts
+++ b/lib/extension/frontend.ts
@@ -6,12 +6,11 @@ import {createServer as createSecureServer} from "node:https";
 import type {Socket} from "node:net";
 import {posix} from "node:path";
 import bind from "bind-decorator";
-import expressStaticGzip from "express-static-gzip";
-import finalhandler from "finalhandler";
 import WebSocket from "ws";
 import data from "../util/data";
 import logger from "../util/logger";
 import * as settings from "../util/settings";
+import {createStaticFileServer, sendNotFound} from "../util/staticFileServer";
 import {stringify} from "../util/stringify";
 import utils from "../util/utils";
 import Extension from "./extension";
@@ -65,46 +64,39 @@ export class Frontend extends Extension {
 
                 return false;
             };
-            const options: expressStaticGzip.ExpressStaticGzipOptions = {
-                enableBrotli: true,
-                serveStatic: {
-                    /* v8 ignore start */
-                    setHeaders: (res: ServerResponse, path: string): void => {
-                        if (path.endsWith("index.html")) {
-                            res.setHeader("Cache-Control", "no-store");
-                        }
-                    },
-                    /* v8 ignore stop */
-                },
-            };
             const frontend = (await import(settings.get().frontend.package)) as typeof import("zigbee2mqtt-frontend");
-            const fileServer = expressStaticGzip(frontend.default.getPath(), options);
-            const deviceIconsFileServer = expressStaticGzip(data.joinPath("device_icons"), options);
+            const logError = logger.error.bind(logger);
+            const fileServer = createStaticFileServer(frontend.default.getPath(), logError);
+            const deviceIconsFileServer = createStaticFileServer(data.joinPath("device_icons"), logError);
             const onRequest = (request: IncomingMessage, response: ServerResponse): void => {
-                const next = finalhandler(request, response);
                 // biome-ignore lint/style/noNonNullAssertion: `Only valid for request obtained from Server`
-                const newUrl = posix.relative(this.baseUrl, request.url!);
+                const url = request.url!;
+                const newUrl = posix.relative(this.baseUrl, url);
 
                 // The request url is not within the frontend base url, so the relative path starts with '..'
                 if (newUrl.startsWith(".")) {
-                    next();
+                    sendNotFound(request, response);
+
+                    return;
+                }
+
+                // The base url itself is a directory, redirect to its trailing slash form so the browser resolves the
+                // relative asset paths in `index.html` against the frontend root instead of against its parent.
+                if (newUrl === "" && !url.endsWith("/")) {
+                    response.writeHead(301, {Location: `${url}/`});
+                    response.end();
 
                     return;
                 }
 
-                // Attach originalUrl so that static-server can perform a redirect to '/' when serving the root directory.
-                // This is necessary for the browser to resolve relative assets paths correctly.
-                request.originalUrl = request.url;
                 request.url = `/${newUrl}`;
-                request.path = request.url;
 
                 if (newUrl.startsWith("device_icons/")) {
-                    request.path = request.path.replace("device_icons/", "");
                     request.url = request.url.replace("/device_icons", "");
 
-                    deviceIconsFileServer(request, response, next);
+                    deviceIconsFileServer(request, response);
                 } else {
-                    fileServer(request, response, next);
+                    fileServer(request, response);
                 }
             };
 
diff --git a/lib/types/dom.shim.d.ts b/lib/types/dom.shim.d.ts
index d11e9b4f8..ce5881fff 100644
--- a/lib/types/dom.shim.d.ts
+++ b/lib/types/dom.shim.d.ts
@@ -10,6 +10,12 @@ declare global {
     const removeEventListener: import("node:events").EventEmitter["removeListener"];
     /** @deprecated DOM SHIM, DO NOT USE */
     const postMessage: import("node:worker_threads").MessagePort["postMessage"];
+    /**
+     * Required by `srvx` <= 0.12.5, remove once a release including https://github.com/h3js/srvx/pull/288 is out.
+     *
+     * @deprecated DOM SHIM, DO NOT USE
+     */
+    type HeadersInit = string[][] | Record<string, string> | Headers;
 }
 
 export {};
diff --git a/lib/types/zigbee2mqtt-frontend.d.ts b/lib/types/zigbee2mqtt-frontend.d.ts
index 11be0682a..5f0c5f437 100644
--- a/lib/types/zigbee2mqtt-frontend.d.ts
+++ b/lib/types/zigbee2mqtt-frontend.d.ts
@@ -5,10 +5,3 @@ declare module "zigbee2mqtt-frontend" {
 
     export default frontend;
 }
-
-declare module "node:http" {
-    interface IncomingMessage {
-        originalUrl?: string;
-        path?: string;
-    }
-}
diff --git a/lib/util/onboarding.ts b/lib/util/onboarding.ts
index 120d5b468..bea8cb700 100644
--- a/lib/util/onboarding.ts
+++ b/lib/util/onboarding.ts
@@ -1,31 +1,15 @@
 import {existsSync, mkdirSync, writeFileSync} from "node:fs";
-import type {ServerResponse} from "node:http";
 import {createServer} from "node:http";
 import path from "node:path";
-import expressStaticGzip from "express-static-gzip";
 import {type Unzipped, unzip} from "fflate";
-import finalhandler from "finalhandler";
 import {findAllDevices} from "zigbee-herdsman/dist/adapter/adapterDiscovery";
 import type {OnboardData, OnboardFailureData, OnboardSubmitResponse, Zigbee2MQTTSettings} from "../types/api";
 import {stringify} from "../util/stringify";
 import data from "./data";
 import * as settings from "./settings";
+import {createStaticFileServer} from "./staticFileServer";
 import {YAMLFileException} from "./yaml";
 
-/** same as extension/frontend */
-const FILE_SERVER_OPTIONS: expressStaticGzip.ExpressStaticGzipOptions = {
-    enableBrotli: true,
-    serveStatic: {
-        /* v8 ignore start */
-        setHeaders: (res: ServerResponse, path: string): void => {
-            if (path.endsWith("index.html")) {
-                res.setHeader("Cache-Control", "no-store");
-            }
-        },
-        /* v8 ignore stop */
-    },
-};
-
 function getServerUrl(): URL {
     return new URL(process.env.Z2M_ONBOARD_URL ?? "http://0.0.0.0:8080");
 }
@@ -72,7 +56,7 @@ async function startOnboardingServer(): Promise<boolean> {
     const currentSettings = settings.get();
     const serverUrl = getServerUrl();
     let server: ReturnType<typeof createServer> | undefined;
-    const fileServer = expressStaticGzip((await import("zigbee2mqtt-windfront")).default.getOnboardingPath(), FILE_SERVER_OPTIONS);
+    const fileServer = createStaticFileServer((await import("zigbee2mqtt-windfront")).default.getOnboardingPath(), console.error);
 
     const success = await new Promise<boolean>((resolve) => {
         server = createServer(async (req, res) => {
@@ -196,9 +180,7 @@ async function startOnboardingServer(): Promise<boolean> {
                 }
             }
 
-            const next = finalhandler(req, res);
-
-            fileServer(req, res, next);
+            fileServer(req, res);
         });
 
         server.on("error", (error: Error) => {
@@ -219,7 +201,7 @@ async function startOnboardingServer(): Promise<boolean> {
 async function startFailureServer(errors: string[]): Promise<void> {
     const serverUrl = getServerUrl();
     let server: ReturnType<typeof createServer> | undefined;
-    const fileServer = expressStaticGzip((await import("zigbee2mqtt-windfront")).default.getOnboardingPath(), FILE_SERVER_OPTIONS);
+    const fileServer = createStaticFileServer((await import("zigbee2mqtt-windfront")).default.getOnboardingPath(), console.error);
 
     await new Promise<void>((resolve) => {
         server = createServer((req, res) => {
@@ -244,9 +226,7 @@ async function startFailureServer(errors: string[]): Promise<void> {
                 return;
             }
 
-            const next = finalhandler(req, res);
-
-            fileServer(req, res, next);
+            fileServer(req, res);
         });
 
         server.listen(Number.parseInt(serverUrl.port, 10), serverUrl.hostname, () => {
diff --git a/lib/util/staticFileServer.ts b/lib/util/staticFileServer.ts
new file mode 100644
index 000000000..1481b0b63
--- /dev/null
+++ b/lib/util/staticFileServer.ts
@@ -0,0 +1,65 @@
+import type {IncomingMessage, ServerResponse} from "node:http";
+import {NodeRequest, sendNodeResponse} from "srvx/node";
+import {staticMiddleware} from "srvx/static";
+
+export type StaticFileServer = (request: IncomingMessage, response: ServerResponse) => void;
+
+const escapeHtml = (value: string): string => value.replace(/[&<>"']/g, (char) => `&#${char.charCodeAt(0)};`);
+
+/** Terminal `404` handler for requests no file matched, mirroring the response `finalhandler` used to produce. */
+export function sendNotFound(request: IncomingMessage, response: ServerResponse): void {
+    const method = request.method /* v8 ignore next */ ?? "GET";
+    const url = request.url /* v8 ignore next */ ?? "/";
+    const message = escapeHtml(`Cannot ${method} ${encodeURI(url)}`);
+    const body = `<!DOCTYPE html>\n<html lang="en">\n<head>\n<meta charset="utf-8">\n<title>Error</title>\n</head>\n<body>\n<pre>${message}</pre>\n</body>\n</html>\n`;
+
+    response.setHeader("Content-Security-Policy", "default-src 'none'");
+    response.setHeader("X-Content-Type-Options", "nosniff");
+    response.setHeader("Content-Type", "text/html; charset=utf-8");
+    response.setHeader("Content-Length", Buffer.byteLength(body));
+    response.writeHead(404);
+    response.end(body);
+}
+
+/**
+ * Serves `dir` on top of a plain `node:http` server, preferring the precompressed `.br`/`.gz` variant of a file when the client accepts it.
+ *
+ * Requests that match no file are answered by {@link sendNotFound}.
+ */
+export function createStaticFileServer(dir: string, logError: (message: string) => void): StaticFileServer {
+    // `compress: false` restricts serving to the precompressed variants shipped on disk, never compressing on the fly
+    const serveDir = staticMiddleware({dir, encodings: true, compress: false});
+    const handle = async (request: IncomingMessage, response: ServerResponse): Promise<void> => {
+        let matched = true;
+        const staticResponse = await serveDir(new NodeRequest({req: request, res: response}), () => {
+            matched = false;
+
+            return new Response(null, {status: 404});
+        });
+
+        if (!matched) {
+            sendNotFound(request, response);
+
+            return;
+        }
+
+        // the HTML entry document must never be cached, so a newly installed frontend version is picked up right away
+        if (staticResponse.headers.get("Content-Type")?.startsWith("text/html")) {
+            staticResponse.headers.set("Cache-Control", "no-store");
+        }
+
+        await sendNodeResponse(response, staticResponse);
+    };
+
+    return (request, response) => {
+        handle(request, response).catch((error) => {
+            logError(`Failed to serve '${request.url}': ${(error as Error).message}`);
+
+            if (!response.headersSent) {
+                response.writeHead(500);
+            }
+
+            response.end();
+        });
+    };
+}
diff --git a/package.json b/package.json
index b352f30d5..d3ce200aa 100644
--- a/package.json
+++ b/package.json
@@ -45,14 +45,13 @@
         "ajv": "^8.20.0",
         "bind-decorator": "^1.0.11",
         "debounce": "^3.0.0",
-        "express-static-gzip": "^3.0.1",
         "fast-deep-equal": "^3.1.3",
         "fflate": "^0.8.3",
-        "finalhandler": "^2.1.1",
         "humanize-duration": "^3.34.0",
         "js-yaml": "^5.2.2",
         "mqtt": "^5.15.2",
         "semver": "^7.8.5",
+        "srvx": "^0.12.5",
         "throttleit": "^3.0.0",
         "winston": "^3.19.0",
         "winston-syslog": "^2.7.1",
@@ -65,11 +64,9 @@
     },
     "devDependencies": {
         "@biomejs/biome": "^2.5.3",
-        "@types/finalhandler": "^1.2.3",
         "@types/humanize-duration": "^3.27.4",
         "@types/node": "^26.1.2",
         "@types/readable-stream": "4.0.24",
-        "@types/serve-static": "^2.2.0",
         "@types/ws": "8.18.1",
         "@vitest/coverage-v8": "^3.1.1",
         "tmp": "^0.2.7",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index dee8ce8a9..528404eb6 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -20,18 +20,12 @@ importers:
       debounce:
         specifier: ^3.0.0
         version: 3.0.0
-      express-static-gzip:
-        specifier: ^3.0.1
-        version: 3.0.1
       fast-deep-equal:
         specifier: ^3.1.3
         version: 3.1.3
       fflate:
         specifier: ^0.8.3
         version: 0.8.3
-      finalhandler:
-        specifier: ^2.1.1
-        version: 2.1.1
       humanize-duration:
         specifier: ^3.34.0
         version: 3.34.0
@@ -44,6 +38,9 @@ importers:
       semver:
         specifier: ^7.8.5
         version: 7.8.5
+      srvx:
+        specifier: ^0.12.5
+        version: 0.12.5
       throttleit:
         specifier: ^3.0.0
         version: 3.0.0
@@ -75,9 +72,6 @@ importers:
       '@biomejs/biome':
         specifier: ^2.5.3
         version: 2.5.3
-      '@types/finalhandler':
-        specifier: ^1.2.3
-        version: 1.2.4
       '@types/humanize-duration':
         specifier: ^3.27.4
         version: 3.27.4
@@ -87,9 +81,6 @@ importers:
       '@types/readable-stream':
         specifier: 4.0.24
         version: 4.0.24
-      '@types/serve-static':
-        specifier: ^2.2.0
-        version: 2.2.0
       '@types/ws':
         specifier: 8.18.1
         version: 8.18.1
@@ -519,12 +510,6 @@ packages:
   '@types/estree@1.0.8':
     resolution: {integrity: sha512-dWHzHa2WqEXI/O1E9OjrocMTKJl2mSrEolh1Iomrv6U+JuNwaHXsXx9bLu5gG7BUWFIN0skIQJQ/L1rIex4X6w==}
 
-  '@types/finalhandler@1.2.4':
-    resolution: {integrity: sha512-ojpQ5ywnKZko/+tw8lR4xvUN5Uvfnar4ZtfpoLG1TdxlmiIqcQGUbXmc9iV5ud7J6rRtacNbwTkCE98NmsBPYw==}
-
-  '@types/http-errors@2.0.5':
-    resolution: {integrity: sha512-r8Tayk8HJnX0FztbZN7oVqGccWgw98T/0neJphO91KkmOzug1KkofZURD4UaD5uH8AqcFLfdPErnBod0u71/qg==}
-
   '@types/humanize-duration@3.27.4':
     resolution: {integrity: sha512-yaf7kan2Sq0goxpbcwTQ+8E9RP6HutFBPv74T/IA/ojcHKhuKVlk2YFYyHhWZeLvZPzzLE3aatuQB4h0iqyyUA==}
 
@@ -534,9 +519,6 @@ packages:
   '@types/readable-stream@4.0.24':
     resolution: {integrity: sha512-NRvUNC/JFGPJvqdAfEve8oginbM6V08u5NzLWpG8MwA2kTPOLnqk+wpwuPT+mp3aUsxyuT6m2gnrPuHYCruzEg==}
 
-  '@types/serve-static@2.2.0':
-    resolution: {integrity: sha512-8mam4H1NHLtu7nmtalF7eyBH14QyOASmcxHhSfEoRyr0nP/YdoesEtU+uSRvMe96TW/HPTtkoKqQLl53N7UXMQ==}
-
   '@types/triple-beam@1.3.5':
     resolution: {integrity: sha512-6WaYesThRMCl19iryMYP7/x2OVgCtbIVflDGFpWnb9irXI3UjYE4AzmYuiUKY1AJstGijoY+MgUszMgRxIYTYw==}
 
@@ -839,10 +821,6 @@ packages:
     resolution: {integrity: sha512-h5k/5U50IJJFpzfL6nO9jaaumfjO/f2NjK/oYB2Djzm4p9L+3T9qWpZqZ2hAbLPuuYq9wrU08WQyBTL5GbPk5Q==}
     engines: {node: '>=6'}
 
-  depd@2.0.0:
-    resolution: {integrity: sha512-g7nH6P6dyDioJogAAGprGpCtVImJhpPk/roCzdb3fIh61/s/nPsfR6onyMwkCAR/OlC3yBC0lESvUoQEAssIrw==}
-    engines: {node: '>= 0.8'}
-
   dns-packet@5.6.1:
     resolution: {integrity: sha512-l4gcSouhcgIKRvyy99RNVOgxXiicE+2jZoNmaNmZ6JXiGajBOJAesk1OBlJuM5k2c+eudGdLxDqXuPCKIj6kpw==}
     engines: {node: '>=6'}
@@ -850,9 +828,6 @@ packages:
   eastasianwidth@0.2.0:
     resolution: {integrity: sha512-I88TYZWc9XiYHRQ4/3c5rjjfgkjhLyW2luGIheGERbNQ6OY7yTybanSpDXZa8y7VUP9YmDcYa+eyq4ca7iLqWA==}
 
-  ee-first@1.1.1:
-    resolution: {integrity: sha512-WMwm9LhRUo+WUaRN+vRuETqG89IgZphVSNkdFgeb6sS/E4OrDIN7t48CAewSHXc6C8lefD8KKfr5vY61brQlow==}
-
   emoji-regex@8.0.0:
     resolution: {integrity: sha512-MSjYzcWNOA0ewAHpz0MxpYFvwg6yjy1NG3xteoqz644VCo/RPgnr1/GGt+ic3iJTzQ8Eu3TdM14SawnVUmGE6A==}
 
@@ -862,10 +837,6 @@ packages:
   enabled@2.0.0:
     resolution: {integrity: sha512-AKrN98kuwOzMIdAizXGI86UFBoo26CL21UM763y1h/GMSJ4/OHU9k2YlsmBpyScFo/wbLzWQJBMCW4+IO3/+OQ==}
 
-  encodeurl@2.0.0:
-    resolution: {integrity: sha512-Q0n9HRi4m6JuGIV1eFlmvJB7ZEVxu93IrMyiMsGC0lrMJMWzRgx6WGquyfQgZVb31vhGgXnfmPNNXmxnOkRBrg==}
-    engines: {node: '>= 0.8'}
-
   es-module-lexer@1.7.0:
     resolution: {integrity: sha512-jEQoCwk8hyb2AZziIOLhDqpm5+2ww5uIE6lkO/6jcOCusfk6LhMHpXXfBLXTZ7Ydyt0j4VoUQv6uGNYbdW+kBA==}
 
@@ -874,16 +845,9 @@ packages:
     engines: {node: '>=18'}
     hasBin: true
 
-  escape-html@1.0.3:
-    resolution: {integrity: sha512-NiSupZ4OeuGwr68lGIeym/ksIZMJodUGOSCZ/FSnTxcrekbvqrgdUxlJOMpijaKZVjAJrWrGs/6Jy8OMuyj9ow==}
-
   estree-walker@3.0.3:
     resolution: {integrity: sha512-7RUKfXgSMMkzt6ZuXmqapOurLGPPfgj6l9uRZ7lRGolvk0y2yocc35LdcxKC5PQZdn2DMqioAQ2NoWcrTKmm6g==}
 
-  etag@1.8.1:
-    resolution: {integrity: sha512-aIL5Fx7mawVa300al2BnEE4iNvo1qETxLrPI/o05L7z6go7fCw1J6EQmbK4FmJ2AS7kgVF/KEZWufBfdClMcPg==}
-    engines: {node: '>= 0.6'}
-
   event-target-shim@5.0.1:
     resolution: {integrity: sha512-i/2XbnSz/uxRCU6+NdVJgKWDTM427+MqYbkQzD321DuCQJUqOuJKIA0IM2+W2xtYHdKOmZ4dR6fExsd4SXL+WQ==}
     engines: {node: '>=6'}
@@ -896,9 +860,6 @@ packages:
     resolution: {integrity: sha512-/kP8CAwxzLVEeFrMm4kMmy4CCDlpipyA7MYLVrdJIkV0fYF0UaigQHRsxHiuY/GEea+bh4KSv3TIlgr+2UL6bw==}
     engines: {node: '>=12.0.0'}
 
-  express-static-gzip@3.0.1:
-    resolution: {integrity: sha512-LMeU/3YjFlFUa4vrPX+RoMMRW5mIpF4Iysgs6gX7A59WCY4BzyF3O28mBr4eMlWuW4DU9wVAVuVcfx29ln1N6g==}
-
   fast-deep-equal@3.1.3:
     resolution: {integrity: sha512-f3qQ9oQy9j2AhBe/H9VC91wLmKBCCU/gDOnKNAYG5hswO7BLKj09Hc5HYNz9cGI++xlpDCIgDaitVs03ATR84Q==}
 
@@ -926,10 +887,6 @@ packages:
   file-uri-to-path@1.0.0:
     resolution: {integrity: sha512-0Zt+s3L7Vf1biwWZ29aARiVYLx7iMGnEUl9x33fbB/j3jR81u/O2LbqK+Bm1CDSNDKVtJ/YjwY7TUd5SkeLQLw==}
 
-  finalhandler@2.1.1:
-    resolution: {integrity: sha512-S8KoZgRZN+a5rNwqTxlZZePjT/4cnm0ROV70LedRHZ0p8u9fRID0hJUZQpkKLzro8LfmC8sx23bY6tVNxv8pQA==}
-    engines: {node: '>= 18.0.0'}
-
   fn.name@1.1.0:
     resolution: {integrity: sha512-GRnmB5gPyJpAhTQdSZTSp9uaPSvl09KoYcMQtsB9rQoOmzs9dH6ffeccH+Z+cv6P68Hu5bC6JjRh4Ah/mHSNRw==}
 
@@ -937,10 +894,6 @@ packages:
     resolution: {integrity: sha512-gIXjKqtFuWEgzFRJA9WCQeSJLZDjgJUOMCMzxtvFq/37KojM1BFGufqsCy0r4qSQmYLsZYMeyRqzIWOMup03sw==}
     engines: {node: '>=14'}
 
-  fresh@2.0.0:
-    resolution: {integrity: sha512-Rx/WycZ60HOaqLKAi6cHRKKI7zxWbJ31MhntmtwMoaTeF7XFH9hhBp8vITaMidfljRQ6eYWCKkaTK+ykVJHP2A==}
-    engines: {node: '>= 0.8'}
-
   fsevents@2.3.3:
     resolution: {integrity: sha512-5xoDfX+fL7faATnagmWPpbFtwh/R77WmMMqqHGS65C3vvB0YHrgF+B1YmZ3441tMj5n63k0212XNoJwzlhffQw==}
     engines: {node: ^8.16.0 || ^10.6.0 || >=11.0.0}
@@ -965,10 +918,6 @@ packages:
   html-escaper@2.0.2:
     resolution: {integrity: sha512-H2iMtd0I4Mt5eYiapRdIDjp+XzelXQ0tFE4JS7YFwFevXXMmOp9myNrUvCg0D6ws8iqkRPBfKHgbwig1SmlLfg==}
 
-  http-errors@2.0.1:
-    resolution: {integrity: sha512-4FbRdAX+bSdmo4AUFuS0WNiPz8NgFt+r8ThgNWmlrjQjt1Q7ZR9+zTlce2859x4KSXrwIsaeTqDoKQmtP8pLmQ==}
-    engines: {node: '>= 0.8'}
-
   humanize-duration@3.34.0:
     resolution: {integrity: sha512-NDxhYxiiRzsST6xULIHuYWRvsCtviJXRdjarhyWyh78S4Ou+MWhM2k4HQ+y7iegdrzreXe11isd0au1N2PB/pQ==}
 
@@ -1052,14 +1001,6 @@ packages:
     resolution: {integrity: sha512-hXdUTZYIVOt1Ex//jAQi+wTZZpUpwBj/0QsOzqegb3rGMMeJiSEu5xLHnYfBrRV4RH2+OCSOO95Is/7x1WJ4bw==}
     engines: {node: '>=10'}
 
-  mime-db@1.54.0:
-    resolution: {integrity: sha512-aU5EJuIN2WDemCcAp2vFBfp/m4EAhWJnUNSSw0ixs7/kXbd6Pg64EmwJkNdFhB8aWt1sH2CTXrLxo/iAGV3oPQ==}
-    engines: {node: '>= 0.6'}
-
-  mime-types@3.0.2:
-    resolution: {integrity: sha512-Lbgzdk0h4juoQ9fCKXW4by0UJqj+nOOrI9MJ1sSj4nI8aI2eo1qmvQEie4VD1glsS250n15LsWsYtCugiStS5A==}
-    engines: {node: '>=18'}
-
   minimatch@9.0.5:
     resolution: {integrity: sha512-G6T0ZX48xgozx7587koeX9Ys2NYy6Gmv//P89sEte9V9whIapMNF4idKxnW2QtCcLiTWlb/wfCabAtAFWhhBow==}
     engines: {node: '>=16 || 14 >=14.17'}
@@ -1105,20 +1046,12 @@ packages:
   number-allocator@1.0.14:
     resolution: {integrity: sha512-OrL44UTVAvkKdOdRQZIJpLkAdjXGTRda052sN4sO77bKEzYYqWKMBjQvrJFzqygI99gL6Z4u2xctPW1tB8ErvA==}
 
-  on-finished@2.4.1:
-    resolution: {integrity: sha512-oVlzkg3ENAhCk2zdv7IJwd/QUD4z2RxRwpkcGY8psCVcCYZNq4wYnVWALHM+brtuJjePWiYF/ClmuDr8Ch5+kg==}
-    engines: {node: '>= 0.8'}
-
   one-time@1.0.0:
     resolution: {integrity: sha512-5DXOiRKwuSEcQ/l0kGCF6Q3jcADFv5tSmRaJck/OqkVFcOzutB134KRSfF0xDrL39MNnqxbHBbUUcjZIhTgb2g==}
 
   package-json-from-dist@1.0.1:
     resolution: {integrity: sha512-UEZIS3/by4OC8vL3P2dTXRETpebLI2NiI5vIrjaD/5UtrkFX/tNbwjTSRAGC/+7CAo2pIcBaRgWmcBBHcsaCIw==}
 
-  parseurl@1.3.3:
-    resolution: {integrity: sha512-CiyeOxFT/JZyN5m0z9PfXw4SCBJ6Sygz1Dpl0wqjlhDEGGBP1GnsUVEL0p63hoG1fcj3fHynXi9NYO4nWOL+qQ==}
-    engines: {node: '>= 0.8'}
-
   path-key@3.1.1:
     resolution: {integrity: sha512-ojmeN0qd+y0jszEtoY48r0Peq5dwMEkIlCOu6Q5f41lfkswXuKtYrhgoTpLnyIcHm24Uhqx+5Tqm2InSwLhE6Q==}
     engines: {node: '>=8'}
@@ -1152,10 +1085,6 @@ packages:
     resolution: {integrity: sha512-cdGef/drWFoydD1JsMzuFf8100nZl+GT+yacc2bEced5f9Rjk4z+WtFUTBu9PhOi9j/jfmBPu0mMEY4wIdAF8A==}
     engines: {node: '>= 0.6.0'}
 
-  range-parser@1.2.1:
-    resolution: {integrity: sha512-Hrgsx+orqoygnmhFbKaHE6c296J+HTAQXoxEF6gNupROmmGJRoyzfG3ccAveqCBrwr/2yxQ5BVd/GTl5agOwSg==}
-    engines: {node: '>= 0.6'}
-
   readable-stream@3.6.2:
     resolution: {integrity: sha512-9u/sniCrY3D5WdsERHzHE4G2YCXqoG5FTHUiCC4SIbr6XcLZBY05ya9EKjYek9O5xOAwjGq+1JdGBAS7Q9ScoA==}
     engines: {node: '>= 6'}
@@ -1191,17 +1120,6 @@ packages:
     engines: {node: '>=10'}
     hasBin: true
 
-  send@1.2.1:
-    resolution: {integrity: sha512-1gnZf7DFcoIcajTjTwjwuDjzuz4PPcY2StKPlsGAQ1+YH20IRVrBaXSWmdjowTJ6u8Rc01PoYOGHXfP1mYcZNQ==}
-    engines: {node: '>= 18'}
-
-  serve-static@2.2.1:
-    resolution: {integrity: sha512-xRXBn0pPqQTVQiC8wyQrKs2MOlX24zQ0POGaj0kultvoOCstBQM5yvOhAVSUwOMjQtTvsPWoNCHfPGwaaQJhTw==}
-    engines: {node: '>= 18'}
-
-  setprototypeof@1.2.0:
-    resolution: {integrity: sha512-E5LDX7Wrp85Kil5bhZv46j8jOeboKq5JMmYM3gVGdGH8xFpPWXUMsNrlODCrkoxMEeNi/XZIwuRvY4XNwYMJpw==}
-
   shebang-command@2.0.0:
     resolution: {integrity: sha512-kHxr2zZpYtdmrN1qDjrrX/Z1rR1kG8Dx+gkpK1G4eXmvXswmcE1hTWBWYUzlraYw1/yZp6YuDY77YtvbN0dmDA==}
     engines: {node: '>=8'}
@@ -1236,16 +1154,17 @@ packages:
     resolution: {integrity: sha512-UcjcJOWknrNkF6PLX83qcHM6KHgVKNkV62Y8a5uYDVv9ydGQVwAHMKqHdJje1VTWpljG0WYpCDhrCdAOYH4TWg==}
     engines: {node: '>= 10.x'}
 
+  srvx@0.12.5:
+    resolution: {integrity: sha512-IuvtDNQg5EIwv3c6dleyau7u8hCyGQ7D6+V/QM799Aud07z0wCUcurKLTRfyG33C8oUY+UWcVBFkfHMcbtmRLA==}
+    engines: {node: '>=20.16.0'}
+    hasBin: true
+
   stack-trace@0.0.10:
     resolution: {integrity: sha512-KGzahc7puUKkzyMt+IqAep+TVNbKP+k2Lmwhub39m1AsTSkaDutx56aDCo+HLDzf/D26BIHTJWNiTG1KAJiQCg==}
 
   stackback@0.0.2:
     resolution: {integrity: sha512-1XMJE5fQo1jGH6Y/7ebnwPOBEkIEnT4QF32d5R1+VXdXveM0IBMJt8zfaxX1P3QhVwrYe+576+jkANtSS2mBbw==}
 
-  statuses@2.0.2:
-    resolution: {integrity: sha512-DvEy55V3DB7uknRo+4iOGT5fP1slR8wQohVdknigZPMpMstaKJQWhwiYBACJE3Ul2pTnATihhBYnRhZQHGBiRw==}
-    engines: {node: '>= 0.8'}
-
   std-env@3.9.0:
     resolution: {integrity: sha512-UGvjygr6F6tpH7o2qyqR6QYpwraIjKSdtzyBdyytFOHmPZY917kwdwLG0RbOjWOnKmnm3PeHjaoLLMie7kPLQw==}
 
@@ -1315,10 +1234,6 @@ packages:
     resolution: {integrity: sha512-e0votIpp4Uo2AJYSzVHV6xCcawuiez3DzqDAbrTc3YxBkplN6e+dM13ZeIcZnDg/QpSuU2zfZ3rzwY8ukEnaXw==}
     engines: {node: '>=14.14'}
 
-  toidentifier@1.0.1:
-    resolution: {integrity: sha512-o5sSPKEkg/DIQNmH43V0/uerLrpzVedkUh8tGNvaeXpfpuwjKenlSox/2O/BTlZUtEe+JG7s5YhEz608PlAHRA==}
-    engines: {node: '>=0.6'}
-
   triple-beam@1.4.1:
     resolution: {integrity: sha512-aZbgViZrg1QNcG+LULa7nhZpJTZSLm/mXnHXnbAbjmN5aSa0y7V+wvv6+4WaBtpISJzThKy+PIPxc1Nq1EJ9mg==}
     engines: {node: '>= 14.0.0'}
@@ -1771,12 +1686,6 @@ snapshots:
 
   '@types/estree@1.0.8': {}
 
-  '@types/finalhandler@1.2.4':
-    dependencies:
-      '@types/node': 26.1.2
-
-  '@types/http-errors@2.0.5': {}
-
   '@types/humanize-duration@3.27.4': {}
 
   '@types/node@26.1.2':
@@ -1787,11 +1696,6 @@ snapshots:
     dependencies:
       '@types/node': 26.1.2
 
-  '@types/serve-static@2.2.0':
-    dependencies:
-      '@types/http-errors': 2.0.5
-      '@types/node': 26.1.2
-
   '@types/triple-beam@1.3.5': {}
 
   '@types/ws@8.18.1':
@@ -2053,24 +1957,18 @@ snapshots:
 
   deep-eql@5.0.2: {}
 
-  depd@2.0.0: {}
-
   dns-packet@5.6.1:
     dependencies:
       '@leichtgewicht/ip-codec': 2.0.5
 
   eastasianwidth@0.2.0: {}
 
-  ee-first@1.1.1: {}
-
   emoji-regex@8.0.0: {}
 
   emoji-regex@9.2.2: {}
 
   enabled@2.0.0: {}
 
-  encodeurl@2.0.0: {}
-
   es-module-lexer@1.7.0: {}
 
   esbuild@0.25.5:
@@ -2101,28 +1999,16 @@ snapshots:
       '@esbuild/win32-ia32': 0.25.5
       '@esbuild/win32-x64': 0.25.5
 
-  escape-html@1.0.3: {}
-
   estree-walker@3.0.3:
     dependencies:
       '@types/estree': 1.0.8
 
-  etag@1.8.1: {}
-
   event-target-shim@5.0.1: {}
 
   events@3.3.0: {}
 
   expect-type@1.2.1: {}
 
-  express-static-gzip@3.0.1:
-    dependencies:
-      mime-types: 3.0.2
-      parseurl: 1.3.3
-      serve-static: 2.2.1
-    transitivePeerDependencies:
-      - supports-color
-
   fast-deep-equal@3.1.3: {}
 
   fast-unique-numbers@9.0.27:
@@ -2143,17 +2029,6 @@ snapshots:
   file-uri-to-path@1.0.0:
     optional: true
 
-  finalhandler@2.1.1:
-    dependencies:
-      debug: 4.4.3
-      encodeurl: 2.0.0
-      escape-html: 1.0.3
-      on-finished: 2.4.1
-      parseurl: 1.3.3
-      statuses: 2.0.2
-    transitivePeerDependencies:
-      - supports-color
-
   fn.name@1.1.0: {}
 
   foreground-child@3.3.1:
@@ -2161,8 +2036,6 @@ snapshots:
       cross-spawn: 7.0.6
       signal-exit: 4.1.0
 
-  fresh@2.0.0: {}
-
   fsevents@2.3.3:
     optional: true
 
@@ -2183,14 +2056,6 @@ snapshots:
 
   html-escaper@2.0.2: {}
 
-  http-errors@2.0.1:
-    dependencies:
-      depd: 2.0.0
-      inherits: 2.0.4
-      setprototypeof: 1.2.0
-      statuses: 2.0.2
-      toidentifier: 1.0.1
-
   humanize-duration@3.34.0: {}
 
   iconv-lite@0.7.3:
@@ -2275,12 +2140,6 @@ snapshots:
     dependencies:
       semver: 7.8.5
 
-  mime-db@1.54.0: {}
-
-  mime-types@3.0.2:
-    dependencies:
-      mime-db: 1.54.0
-
   minimatch@9.0.5:
     dependencies:
       brace-expansion: 2.1.0
@@ -2343,18 +2202,12 @@ snapshots:
     transitivePeerDependencies:
       - supports-color
 
-  on-finished@2.4.1:
-    dependencies:
-      ee-first: 1.1.1
-
   one-time@1.0.0:
     dependencies:
       fn.name: 1.1.0
 
   package-json-from-dist@1.0.1: {}
 
-  parseurl@1.3.3: {}
-
   path-key@3.1.1: {}
 
   path-scurry@1.11.1:
@@ -2380,8 +2233,6 @@ snapshots:
 
   process@0.11.10: {}
 
-  range-parser@1.2.1: {}
-
   readable-stream@3.6.2:
     dependencies:
       inherits: 2.0.4
@@ -2434,33 +2285,6 @@ snapshots:
 
   semver@7.8.5: {}
 
-  send@1.2.1:
-    dependencies:
-      debug: 4.4.3
-      encodeurl: 2.0.0
-      escape-html: 1.0.3
-      etag: 1.8.1
-      fresh: 2.0.0
-      http-errors: 2.0.1
-      mime-types: 3.0.2
-      ms: 2.1.3
-      on-finished: 2.4.1
-      range-parser: 1.2.1
-      statuses: 2.0.2
-    transitivePeerDependencies:
-      - supports-color
-
-  serve-static@2.2.1:
-    dependencies:
-      encodeurl: 2.0.0
-      escape-html: 1.0.3
-      parseurl: 1.3.3
-      send: 1.2.1
-    transitivePeerDependencies:
-      - supports-color
-
-  setprototypeof@1.2.0: {}
-
   shebang-command@2.0.0:
     dependencies:
       shebang-regex: 3.0.0
@@ -2484,12 +2308,12 @@ snapshots:
 
   split2@4.2.0: {}
 
+  srvx@0.12.5: {}
+
   stack-trace@0.0.10: {}
 
   stackback@0.0.2: {}
 
-  statuses@2.0.2: {}
-
   std-env@3.9.0: {}
 
   string-width@4.2.3:
@@ -2553,8 +2377,6 @@ snapshots:
 
   tmp@0.2.7: {}
 
-  toidentifier@1.0.1: {}
-
   triple-beam@1.4.1: {}
 
   tslib@2.8.1: {}
diff --git a/test/extensions/frontend.test.ts b/test/extensions/frontend.test.ts
index 9a98901f8..fb448d40e 100644
--- a/test/extensions/frontend.test.ts
+++ b/test/extensions/frontend.test.ts
@@ -13,7 +13,12 @@ import ws from "ws";
 import {Controller} from "../../lib/controller";
 import * as settings from "../../lib/util/settings";
 
-let mockHTTPOnRequest: (request: {url: string}, response: number) => void;
+const mockRedirectResponse = {
+    writeHead: vi.fn<(statusCode: number, headers: Record<string, string>) => void>(),
+    end: vi.fn<() => void>(),
+};
+
+let mockHTTPOnRequest: (request: {url: string}, response: number | typeof mockRedirectResponse) => void;
 const mockHTTPEvents: Record<string, EventHandler> = {};
 const mockHTTP = {
     listen: vi.fn(),
@@ -64,7 +69,7 @@ const frontendPath = "frontend-path";
 const deviceIconsPath = path.join(data.mockDir, "device_icons");
 let mockNodeStatic: {[s: string]: Mock} = {};
 
-const mockFinalHandler = vi.fn();
+const mockSendNotFound = vi.fn();
 
 vi.mock("node:http", () => ({
     createServer: vi.fn().mockImplementation((onRequest) => {
@@ -79,11 +84,12 @@ vi.mock("node:https", () => ({
     Agent: vi.fn(),
 }));
 
-vi.mock("express-static-gzip", () => ({
-    default: vi.fn().mockImplementation((path: string) => {
+vi.mock("../../lib/util/staticFileServer", () => ({
+    createStaticFileServer: vi.fn().mockImplementation((path: string) => {
         mockNodeStatic[path] = vi.fn();
         return mockNodeStatic[path];
     }),
+    sendNotFound: vi.fn().mockImplementation((...args: unknown[]) => mockSendNotFound(...args)),
 }));
 
 vi.mock("zigbee2mqtt-windfront", () => ({
@@ -101,12 +107,6 @@ vi.mock("ws", () => ({
     },
 }));
 
-vi.mock("finalhandler", () => ({
-    default: vi.fn().mockImplementation(() => {
-        return mockFinalHandler;
-    }),
-}));
-
 const mocksClear = [
     mockHTTP.close,
     mockHTTP.listen,
@@ -118,7 +118,9 @@ const mocksClear = [
     mockWS.emit,
     mockWSClient.send,
     mockWSClient.terminate,
-    mockFinalHandler,
+    mockSendNotFound,
+    mockRedirectResponse.writeHead,
+    mockRedirectResponse.end,
     mockMQTTPublishAsync,
     mockLogger.error,
 ];
@@ -340,11 +342,7 @@ describe("Extension: Frontend", () => {
         mockHTTPOnRequest({url: "/file.txt"}, 2);
         expect(mockNodeStatic[deviceIconsPath]).toHaveBeenCalledTimes(0);
         expect(mockNodeStatic[frontendPath]).toHaveBeenCalledTimes(1);
-        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith(
-            {originalUrl: "/file.txt", path: "/file.txt", url: "/file.txt"},
-            2,
-            expect.any(Function),
-        );
+        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith({url: "/file.txt"}, 2);
     });
 
     it("Should serve device icons", async () => {
@@ -354,11 +352,7 @@ describe("Extension: Frontend", () => {
         mockHTTPOnRequest({url: "/device_icons/my_device.png"}, 2);
         expect(mockNodeStatic[frontendPath]).toHaveBeenCalledTimes(0);
         expect(mockNodeStatic[deviceIconsPath]).toHaveBeenCalledTimes(1);
-        expect(mockNodeStatic[deviceIconsPath]).toHaveBeenCalledWith(
-            {originalUrl: "/device_icons/my_device.png", path: "/my_device.png", url: "/my_device.png"},
-            2,
-            expect.any(Function),
-        );
+        expect(mockNodeStatic[deviceIconsPath]).toHaveBeenCalledWith({url: "/my_device.png"}, 2);
     });
 
     it("Static server", async () => {
@@ -402,34 +396,33 @@ describe("Extension: Frontend", () => {
 
         expect(ws.Server).toHaveBeenCalledWith({noServer: true, path: "/z2m/api"});
 
-        mockHTTPOnRequest({url: "/z2m"}, 2);
+        // the base url without trailing slash points at a directory, redirect so relative asset paths resolve against it
+        mockHTTPOnRequest({url: "/z2m"}, mockRedirectResponse);
+        expect(mockNodeStatic[frontendPath]).not.toHaveBeenCalled();
+        expect(mockRedirectResponse.writeHead).toHaveBeenCalledWith(301, {Location: "/z2m/"});
+        expect(mockRedirectResponse.end).toHaveBeenCalledTimes(1);
+        expect(mockSendNotFound).not.toHaveBeenCalled();
+
+        mockHTTPOnRequest({url: "/z2m/"}, 2);
         expect(mockNodeStatic[frontendPath]).toHaveBeenCalledTimes(1);
-        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith({originalUrl: "/z2m", path: "/", url: "/"}, 2, expect.any(Function));
-        expect(mockFinalHandler).not.toHaveBeenCalledWith();
+        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith({url: "/"}, 2);
+        expect(mockSendNotFound).not.toHaveBeenCalledWith();
 
         mockNodeStatic[frontendPath].mockReset();
-        expect(mockFinalHandler).not.toHaveBeenCalledWith();
+        expect(mockSendNotFound).not.toHaveBeenCalledWith();
         mockHTTPOnRequest({url: "/z2m/file.txt"}, 2);
         expect(mockNodeStatic[frontendPath]).toHaveBeenCalledTimes(1);
-        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith(
-            {originalUrl: "/z2m/file.txt", path: "/file.txt", url: "/file.txt"},
-            2,
-            expect.any(Function),
-        );
-        expect(mockFinalHandler).not.toHaveBeenCalledWith();
+        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith({url: "/file.txt"}, 2);
+        expect(mockSendNotFound).not.toHaveBeenCalledWith();
 
         mockNodeStatic[frontendPath].mockReset();
         mockHTTPOnRequest({url: "/z/file.txt"}, 2);
         expect(mockNodeStatic[frontendPath]).not.toHaveBeenCalled();
-        expect(mockFinalHandler).toHaveBeenCalled();
+        expect(mockSendNotFound).toHaveBeenCalled();
 
         mockHTTPOnRequest({url: "/z2m/device_icons/my-device.png"}, 2);
         expect(mockNodeStatic[deviceIconsPath]).toHaveBeenCalledTimes(1);
-        expect(mockNodeStatic[deviceIconsPath]).toHaveBeenCalledWith(
-            {originalUrl: "/z2m/device_icons/my-device.png", path: "/my-device.png", url: "/my-device.png"},
-            2,
-            expect.any(Function),
-        );
+        expect(mockNodeStatic[deviceIconsPath]).toHaveBeenCalledWith({url: "/my-device.png"}, 2);
     });
 
     it("Works with non-default complex base url", async () => {
@@ -440,30 +433,28 @@ describe("Extension: Frontend", () => {
 
         expect(ws.Server).toHaveBeenCalledWith({noServer: true, path: "/z2m-more++/c0mplex.url/api"});
 
-        mockHTTPOnRequest({url: "/z2m-more++/c0mplex.url"}, 2);
+        mockHTTPOnRequest({url: "/z2m-more++/c0mplex.url"}, mockRedirectResponse);
+        expect(mockNodeStatic[frontendPath]).not.toHaveBeenCalled();
+        expect(mockRedirectResponse.writeHead).toHaveBeenCalledWith(301, {Location: "/z2m-more++/c0mplex.url/"});
+        expect(mockRedirectResponse.end).toHaveBeenCalledTimes(1);
+        expect(mockSendNotFound).not.toHaveBeenCalled();
+
+        mockHTTPOnRequest({url: "/z2m-more++/c0mplex.url/"}, 2);
         expect(mockNodeStatic[frontendPath]).toHaveBeenCalledTimes(1);
-        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith(
-            {originalUrl: "/z2m-more++/c0mplex.url", path: "/", url: "/"},
-            2,
-            expect.any(Function),
-        );
-        expect(mockFinalHandler).not.toHaveBeenCalledWith();
+        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith({url: "/"}, 2);
+        expect(mockSendNotFound).not.toHaveBeenCalledWith();
 
         mockNodeStatic[frontendPath].mockReset();
-        expect(mockFinalHandler).not.toHaveBeenCalledWith();
+        expect(mockSendNotFound).not.toHaveBeenCalledWith();
         mockHTTPOnRequest({url: "/z2m-more++/c0mplex.url/file.txt"}, 2);
         expect(mockNodeStatic[frontendPath]).toHaveBeenCalledTimes(1);
-        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith(
-            {originalUrl: "/z2m-more++/c0mplex.url/file.txt", path: "/file.txt", url: "/file.txt"},
-            2,
-            expect.any(Function),
-        );
-        expect(mockFinalHandler).not.toHaveBeenCalledWith();
+        expect(mockNodeStatic[frontendPath]).toHaveBeenCalledWith({url: "/file.txt"}, 2);
+        expect(mockSendNotFound).not.toHaveBeenCalledWith();
 
         mockNodeStatic[frontendPath].mockReset();
         mockHTTPOnRequest({url: "/z/file.txt"}, 2);
         expect(mockNodeStatic[frontendPath]).not.toHaveBeenCalled();
-        expect(mockFinalHandler).toHaveBeenCalled();
+        expect(mockSendNotFound).toHaveBeenCalled();
     });
 
     it("prevents mismatching setting/extension state", async () => {
diff --git a/test/onboarding.test.ts b/test/onboarding.test.ts
index 49261c380..45dbd9e15 100644
--- a/test/onboarding.test.ts
+++ b/test/onboarding.test.ts
@@ -31,16 +31,10 @@ const mockHttpClose = vi.fn<Server["close"]>(
     },
 );
 const mockFindAllDevices = vi.fn<typeof findAllDevices>(async () => []);
-const mockStaticFileServer = vi.fn((_req, res, next) => {
-    if (typeof next === "function") {
-        next();
-    }
-
+const mockStaticFileServer = vi.fn((_req, res) => {
     res.end();
 });
-const mockExpressStaticGzip = vi.fn((_path: unknown, _options: unknown) => mockStaticFileServer);
-const mockFinalHandlerNext = vi.fn();
-const mockFinalhandler = vi.fn((_req: unknown, _res: unknown) => mockFinalHandlerNext);
+const mockCreateStaticFileServer = vi.fn((_dir: unknown, _logError: unknown) => mockStaticFileServer);
 
 vi.mock("node:fs", {spy: true});
 vi.mock("node:http", () => ({
@@ -62,11 +56,8 @@ vi.mock("node:http", () => ({
         };
     }),
 }));
-vi.mock("express-static-gzip", () => ({
-    default: vi.fn((path, options) => mockExpressStaticGzip(path, options)),
-}));
-vi.mock("finalhandler", () => ({
-    default: vi.fn((req, res) => mockFinalhandler(req, res)),
+vi.mock("../lib/util/staticFileServer", () => ({
+    createStaticFileServer: vi.fn((dir, logError) => mockCreateStaticFileServer(dir, logError)),
 }));
 vi.mock("zigbee-herdsman/dist/adapter/adapterDiscovery", () => ({
     findAllDevices: vi.fn(() => mockFindAllDevices()),
@@ -194,10 +185,7 @@ describe("Onboarding", () => {
         mockFindAllDevices.mockClear();
         mockHttpErrorListener = undefined;
         mockStaticFileServer.mockClear();
-        mockExpressStaticGzip.mockClear();
-        mockFinalHandlerNext.mockClear();
-        mockFinalhandler.mockClear();
-        mockStaticFileServer.mockClear();
+        mockCreateStaticFileServer.mockClear();
         settings.reRead();
     });
 
@@ -735,7 +723,6 @@ describe("Onboarding", () => {
         });
 
         await expect(p).resolves.toStrictEqual(true);
-        expect(mockFinalhandler).toHaveBeenCalled();
         expect(mockStaticFileServer).toHaveBeenCalled();
     });
 
@@ -757,7 +744,6 @@ describe("Onboarding", () => {
         });
 
         await expect(p).resolves.toStrictEqual(false);
-        expect(mockFinalhandler).toHaveBeenCalled();
         expect(mockStaticFileServer).toHaveBeenCalled();
     });
 
diff --git a/test/staticFileServer.test.ts b/test/staticFileServer.test.ts
new file mode 100644
index 000000000..1a22a1361
--- /dev/null
+++ b/test/staticFileServer.test.ts
@@ -0,0 +1,185 @@
+import {mkdirSync, writeFileSync} from "node:fs";
+import {createServer, type Server} from "node:http";
+import {type AddressInfo, connect} from "node:net";
+import {join} from "node:path";
+import {brotliCompressSync, gzipSync} from "node:zlib";
+import tmp from "tmp";
+import {afterAll, beforeAll, describe, expect, it, vi} from "vitest";
+import {createStaticFileServer, type sendNotFound} from "../lib/util/staticFileServer";
+
+const INDEX_HTML = "<!DOCTYPE html><html lang='en'><body>index</body></html>";
+const APP_JS = `console.log("${"x".repeat(2048)}");`;
+/** Written next to the served directory, never inside it, so a traversal that succeeds is actually observable. */
+const SECRET = "topsecret-must-never-be-served";
+
+const mockLogError = vi.fn<(message: string) => void>();
+
+let dir: string;
+let server: Server;
+let baseUrl: string;
+
+/** Starts a `node:http` server serving `dir`, mirroring how the frontend/onboarding extensions wire it up. */
+function listen(handler: (request: Parameters<typeof sendNotFound>[0], response: Parameters<typeof sendNotFound>[1]) => void): Promise<void> {
+    server = createServer(handler);
+
+    return new Promise((resolve) => {
+        server.listen(0, "127.0.0.1", () => {
+            baseUrl = `http://127.0.0.1:${(server.address() as AddressInfo).port}`;
+
+            resolve();
+        });
+    });
+}
+
+/** Writes a request line verbatim, bypassing the path normalization `fetch` applies before sending. */
+function rawRequest(target: string): Promise<string> {
+    return new Promise((resolve, reject) => {
+        const socket = connect((server.address() as AddressInfo).port, "127.0.0.1", () => {
+            socket.write(`GET ${target} HTTP/1.1\r\nHost: 127.0.0.1\r\nConnection: close\r\n\r\n`);
+        });
+        let received = "";
+
+        socket.setEncoding("utf8");
+        socket.on("data", (chunk) => {
+            received += chunk;
+        });
+        socket.on("end", () => resolve(received));
+        socket.on("error", reject);
+    });
+}
+
+describe("StaticFileServer", () => {
+    beforeAll(async () => {
+        const root = tmp.dirSync().name;
+
+        dir = join(root, "public");
+
+        // outside the served directory: only a working traversal could reach it
+        writeFileSync(join(root, "secret.txt"), SECRET);
+        mkdirSync(join(dir, "sub"), {recursive: true});
+        writeFileSync(join(dir, "index.html"), INDEX_HTML);
+        writeFileSync(join(dir, "app.js"), APP_JS);
+        // precompressed variants, as shipped by the frontend packages
+        writeFileSync(join(dir, "app.js.gz"), gzipSync(APP_JS));
+        writeFileSync(join(dir, "app.js.br"), brotliCompressSync(APP_JS));
+        writeFileSync(join(dir, "sub", "icon.png"), Buffer.from([0x89, 0x50, 0x4e, 0x47]));
+
+        await listen(createStaticFileServer(dir, mockLogError));
+    });
+
+    afterAll(async () => {
+        await new Promise((resolve) => server.close(resolve));
+    });
+
+    it("serves a file with its content type", async () => {
+        const response = await fetch(`${baseUrl}/sub/icon.png`);
+
+        expect(response.status).toStrictEqual(200);
+        expect(response.headers.get("content-type")).toStrictEqual("image/png");
+        expect(response.headers.get("content-encoding")).toBeNull();
+    });
+
+    it("serves index.html for the root, never cached", async () => {
+        const response = await fetch(`${baseUrl}/`);
+
+        expect(response.status).toStrictEqual(200);
+        expect(response.headers.get("content-type")).toStrictEqual("text/html; charset=utf-8");
+        expect(response.headers.get("cache-control")).toStrictEqual("no-store");
+        await expect(response.text()).resolves.toStrictEqual(INDEX_HTML);
+    });
+
+    it("serves the precompressed brotli variant", async () => {
+        const response = await fetch(`${baseUrl}/app.js`, {headers: {"Accept-Encoding": "br"}});
+
+        expect(response.status).toStrictEqual(200);
+        expect(response.headers.get("content-encoding")).toStrictEqual("br");
+        expect(response.headers.get("content-type")).toStrictEqual("text/javascript; charset=utf-8");
+        expect(response.headers.get("vary")).toStrictEqual("Accept-Encoding");
+        // decoded by fetch, so the served bytes must be the brotli variant of the original file
+        await expect(response.text()).resolves.toStrictEqual(APP_JS);
+    });
+
+    it("serves the precompressed gzip variant", async () => {
+        const response = await fetch(`${baseUrl}/app.js`, {headers: {"Accept-Encoding": "gzip"}});
+
+        expect(response.status).toStrictEqual(200);
+        expect(response.headers.get("content-encoding")).toStrictEqual("gzip");
+        await expect(response.text()).resolves.toStrictEqual(APP_JS);
+    });
+
+    it("serves the identity file when no encoding is accepted", async () => {
+        const response = await fetch(`${baseUrl}/app.js`, {headers: {"Accept-Encoding": "identity"}});
+
+        expect(response.status).toStrictEqual(200);
+        expect(response.headers.get("content-encoding")).toBeNull();
+        expect(response.headers.get("content-length")).toStrictEqual(String(Buffer.byteLength(APP_JS)));
+        await expect(response.text()).resolves.toStrictEqual(APP_JS);
+    });
+
+    it("revalidates with an etag", async () => {
+        const response = await fetch(`${baseUrl}/app.js`, {headers: {"Accept-Encoding": "identity"}});
+        const etag = response.headers.get("etag");
+
+        expect(etag).toBeTruthy();
+
+        const revalidated = await fetch(`${baseUrl}/app.js`, {headers: {"Accept-Encoding": "identity", "If-None-Match": etag as string}});
+
+        expect(revalidated.status).toStrictEqual(304);
+    });
+
+    it("returns 404 for an unknown file", async () => {
+        const response = await fetch(`${baseUrl}/nope.js`);
+
+        expect(response.status).toStrictEqual(404);
+        expect(response.headers.get("content-type")).toStrictEqual("text/html; charset=utf-8");
+        expect(response.headers.get("content-security-policy")).toStrictEqual("default-src 'none'");
+        expect(response.headers.get("x-content-type-options")).toStrictEqual("nosniff");
+        await expect(response.text()).resolves.toContain("Cannot GET /nope.js");
+    });
+
+    it("escapes the url in the 404 body", async () => {
+        const response = await fetch(`${baseUrl}/%3Cscript%3E`);
+
+        expect(response.status).toStrictEqual(404);
+        await expect(response.text()).resolves.not.toContain("<script>");
+    });
+
+    it("does not serve files outside of the served directory", async () => {
+        // `fetch` resolves `..` and `%2e%2e` segments away before they ever reach the server, so these have to go out raw
+        for (const target of ["/../secret.txt", "/sub/../../secret.txt", "/%2e%2e/secret.txt", "/..%2fsecret.txt"]) {
+            const response = await rawRequest(target);
+
+            expect(response).toContain("404 Not Found");
+            expect(response).not.toContain(SECRET);
+        }
+    });
+
+    it("reports a failure to serve with a 500", async () => {
+        const failing = createStaticFileServer(dir, mockLogError);
+        const failingServer = createServer((request, response) => {
+            const setHeader = response.setHeader.bind(response);
+
+            response.setHeader = (name: string, value: number | string | readonly string[]): never => {
+                if (name === "Content-Security-Policy") {
+                    throw new Error("socket gone");
+                }
+
+                setHeader(name, value);
+
+                return undefined as never;
+            };
+
+            failing(request, response);
+        });
+
+        await new Promise<void>((resolve) => failingServer.listen(0, "127.0.0.1", resolve));
+
+        const port = (failingServer.address() as AddressInfo).port;
+        const response = await fetch(`http://127.0.0.1:${port}/nope.js`);
+
+        expect(response.status).toStrictEqual(500);
+        expect(mockLogError).toHaveBeenCalledWith("Failed to serve '/nope.js': socket gone");
+
+        await new Promise((resolve) => failingServer.close(resolve));
+    });
+});