diff --git a/README.md b/README.md
index 0f3159d..a2107cd 100644
--- a/README.md
+++ b/README.md
@@ -626,3 +626,4 @@ npx vitest              # watch mode
 | `eas update` must be run with `--platform android` (`mobile/`), not `--platform all` | This app has no web target — `react-native-web` isn't installed — so the default `--platform all` fails bundling with `Unable to resolve module react-native-web/dist/index`. Previously published updates were all Android-only too (check `eas channel:view <channel>` to confirm before assuming this changed). |
 | `mobile/node_modules` can end up silently corrupted (missing nested files) after an interrupted/partial install, without `npm install` re-detecting or fixing it | Symptom: Metro bundling fails with `Unable to resolve module ./some/nested/path.js` inside an already-installed package (seen with `@expo/cli`'s `utils/telemetry`, then `@sentry/browser` and `@sentry-internal/browser-utils` in the same session) — `npm install` reports "up to date" and does nothing. Fix: `rm -rf node_modules && npm install` (a full reinstall), not a targeted one; deleting just the one broken package's folder can just surface the *next* corrupted package one bundle-failure at a time. |
 | Mobile Google SSO can break with `redirect url ... does not match an authorized redirect URI` even though `GoogleSignInButton.tsx`/`app.json`'s scheme are unchanged | Clerk keeps its authorized-redirect-URL allowlist server-side per instance (`GET`/`POST https://api.clerk.com/v1/redirect_urls`, auth via `CLERK_SECRET_KEY`), entirely outside this repo — it can be missing or reset independent of any code change. Check that list before debugging app code; add the missing entry (`{"url":"pawfeed://sso-callback"}` for this app's `"scheme": "pawfeed"`) via `POST /v1/redirect_urls` — takes effect immediately, no app deploy/rebuild needed. |
+| Admin music-track upload can fail even with a genuinely valid MP3/M4A/AAC file | Two independent causes, both hit in the same incident: (1) the Supabase bucket must be named **exactly** `music-tracks` (plural) — it was once created as `music-track` (singular), so every upload failed with a bucket-not-found error surfaced only as a generic "Upload fehlgeschlagen" toast; verify via `GET {SUPABASE_URL}/storage/v1/bucket` with the service-role key. (2) The upload form used to validate against the browser-reported `File.type`, which is sniffed from the OS's own MIME registry and is inconsistent for `.m4a`/`.aac` (e.g. Windows Chrome reports `.m4a` as `audio/x-m4a`, not `audio/mp4`) — it now derives the content-type from the file extension instead (`src/lib/music-content-types.ts`), matching what `MUSIC_ALLOWED_CONTENT_TYPES` (server-side, `supabase-storage.ts`) actually expects. |
diff --git a/src/app/p/[secret]/music/page.tsx b/src/app/p/[secret]/music/page.tsx
index 36df3cd..e85f46f 100644
--- a/src/app/p/[secret]/music/page.tsx
+++ b/src/app/p/[secret]/music/page.tsx
@@ -4,6 +4,7 @@ import { useState, useRef, useCallback } from "react";
 import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
 import { useTRPC } from "@/trpc/client";
 import { getMusicUrl } from "@/lib/music-url";
+import { MAX_MUSIC_FILE_SIZE, MUSIC_EXTENSION_CONTENT_TYPES, type MusicContentType } from "@/lib/music-content-types";
 import { Plus, Pencil, Trash2, Loader2, Check, X, Music, Play, Pause } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
@@ -23,9 +24,34 @@ type TrackForm = {
 
 const emptyForm: TrackForm = { title: "", artist: "", licenseNote: "", storageKey: "", durationSecs: 0 };
 
-const ALLOWED_TYPES = ["audio/mpeg", "audio/mp4", "audio/aac"] as const;
-type AllowedType = (typeof ALLOWED_TYPES)[number];
-const MAX_SIZE = 5 * 1024 * 1024;
+const MAX_SIZE = MAX_MUSIC_FILE_SIZE;
+
+/**
+ * Extension -> canonical content-type, used instead of the browser-reported
+ * `file.type` for both validation and the actual upload's Content-Type
+ * header. `file.type` is sniffed by the browser/OS from its own MIME
+ * registry and is inconsistent for exactly these formats — Windows Chrome
+ * commonly reports `.m4a` as `audio/x-m4a` (not `audio/mp4`), and an
+ * unrecognized extension can come back as an empty string. Either would
+ * fail the old `ALLOWED_TYPES.includes(file.type)` check even for a
+ * perfectly valid MP3/M4A/AAC file — the upload looked like a rejected file
+ * type when it was really just an unrecognized *reported* MIME type.
+ *
+ * This does mean a file can be uploaded by simply renaming it with an
+ * allowed extension (e.g. `notes.txt` -> `notes.mp3`) rather than the
+ * browser's MIME-sniffed type having to agree first — a deliberate
+ * trade-off, not an oversight (flagged in code review): `file.type` was
+ * never a real content-based check either (browsers derive it from the same
+ * OS extension registry, not from inspecting bytes), this panel sits behind
+ * `ADMIN_SECRET` + a role check, not the public upload surface, and
+ * `readAudioDuration()` below still fails for genuinely non-audio bytes.
+ */
+function resolveContentType(file: File): MusicContentType | null {
+  const dotIndex = file.name.lastIndexOf(".");
+  if (dotIndex <= 0) return null; // no extension (or a bare ".ext"-only name)
+  const ext = file.name.slice(dotIndex + 1).toLowerCase();
+  return MUSIC_EXTENSION_CONTENT_TYPES.get(ext) ?? null;
+}
 
 /** Reads an audio file's duration client-side via a detached <audio> element. */
 function readAudioDuration(file: File): Promise<number> {
@@ -116,8 +142,9 @@ export default function AdminMusicPage() {
         toast.error("Audiodatei muss unter 5 MB sein.");
         return;
       }
-      if (!ALLOWED_TYPES.includes(file.type as AllowedType)) {
-        toast.error("Nur MP3, M4A oder AAC erlaubt.");
+      const contentType = resolveContentType(file);
+      if (!contentType) {
+        toast.error("Nur .mp3, .m4a oder .aac erlaubt.");
         return;
       }
 
@@ -125,7 +152,7 @@ export default function AdminMusicPage() {
       try {
         const durationSecs = await readAudioDuration(file);
         const { presignedUrl, key } = await getUploadUrl.mutateAsync({
-          contentType: file.type as AllowedType,
+          contentType,
           fileSize: file.size,
         });
 
@@ -135,7 +162,7 @@ export default function AdminMusicPage() {
             xhr.status >= 200 && xhr.status < 300 ? resolve() : reject(new Error(`Upload failed: ${xhr.status}`));
           xhr.onerror = () => reject(new Error("Network error"));
           xhr.open("PUT", presignedUrl);
-          xhr.setRequestHeader("Content-Type", file.type);
+          xhr.setRequestHeader("Content-Type", contentType);
           xhr.send(file);
         });
 
@@ -245,7 +272,7 @@ export default function AdminMusicPage() {
                 <input
                   ref={fileInputRef}
                   type="file"
-                  accept="audio/mpeg,audio/mp4,audio/aac"
+                  accept=".mp3,.m4a,.aac,audio/mpeg,audio/mp4,audio/aac"
                   className="hidden"
                   onChange={handleFileChange}
                 />
diff --git a/src/lib/music-content-types.ts b/src/lib/music-content-types.ts
new file mode 100644
index 0000000..7e7ed04
--- /dev/null
+++ b/src/lib/music-content-types.ts
@@ -0,0 +1,26 @@
+/**
+ * Client-safe constants for Story music-track uploads. Extracted out of
+ * `supabase-storage.ts` (which imports `"server-only"` and therefore can't
+ * be imported from the admin music page, a `"use client"` component) so the
+ * upload form and the server-side storage/tRPC code share one source of
+ * truth instead of two independently maintained copies drifting apart —
+ * found during code review of the upload-validation fix (see
+ * README.md's Known Issues).
+ */
+export const MUSIC_ALLOWED_CONTENT_TYPES = ["audio/mpeg", "audio/mp4", "audio/aac"] as const;
+export type MusicContentType = (typeof MUSIC_ALLOWED_CONTENT_TYPES)[number];
+
+export const MAX_MUSIC_FILE_SIZE = 5 * 1024 * 1024; // 5 MB — short clips only
+
+/**
+ * Extension -> canonical content-type. A `Map`, not a plain object literal —
+ * a plain-object lookup (`{ mp3: ... }[ext]`) resolves inherited
+ * `Object.prototype` members for an extension like "constructor", silently
+ * returning a function instead of `undefined` and bypassing the "unknown
+ * extension" rejection entirely.
+ */
+export const MUSIC_EXTENSION_CONTENT_TYPES: ReadonlyMap<string, MusicContentType> = new Map([
+  ["mp3", "audio/mpeg"],
+  ["m4a", "audio/mp4"],
+  ["aac", "audio/aac"],
+]);
diff --git a/src/lib/supabase-storage.ts b/src/lib/supabase-storage.ts
index f35bf85..267d0a2 100644
--- a/src/lib/supabase-storage.ts
+++ b/src/lib/supabase-storage.ts
@@ -1,5 +1,8 @@
 import "server-only";
 import { createClient, type SupabaseClient } from "@supabase/supabase-js";
+import { MUSIC_ALLOWED_CONTENT_TYPES, MAX_MUSIC_FILE_SIZE } from "./music-content-types";
+
+export { MUSIC_ALLOWED_CONTENT_TYPES, MAX_MUSIC_FILE_SIZE };
 
 // Lazy singleton — not initialized at module eval so Next.js build does not
 // throw when env vars are absent during the page-data collection phase.
@@ -22,10 +25,14 @@ export const ALLOWED_CONTENT_TYPES = ["image/jpeg", "image/png", "image/webp"] a
 
 // Music-track catalog (admin-curated, see admin.ts's music-track procedures)
 // — a separate bucket since it holds audio, not images. Must be created once
-// in the Supabase dashboard; this code assumes it already exists.
+// in the Supabase dashboard (name must match exactly — a "music-track" vs.
+// "music-tracks" typo here once made every upload fail with a bucket-not-found
+// error that surfaced as a generic upload failure, see README.md's Known
+// Issues); this code assumes it already exists.
 export const MUSIC_STORAGE_BUCKET = "music-tracks";
-export const MAX_MUSIC_FILE_SIZE = 5 * 1024 * 1024; // 5 MB — short clips only
-export const MUSIC_ALLOWED_CONTENT_TYPES = ["audio/mpeg", "audio/mp4", "audio/aac"] as const;
+// MAX_MUSIC_FILE_SIZE / MUSIC_ALLOWED_CONTENT_TYPES live in ./music-content-types
+// (a plain, non-"server-only" module) and are re-exported above so existing
+// imports of this file keep working — see that file's doc comment for why.
 
 /**
  * Creates a signed upload URL for direct client-to-Supabase uploads.