diff --git a/package-lock.json b/package-lock.json
index 485a15a..6e3312d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "mediabunny",
-  "version": "1.29.1",
+  "version": "1.30.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "mediabunny",
-      "version": "1.29.1",
+      "version": "1.30.0",
       "license": "MPL-2.0",
       "workspaces": [
         "packages/*"
@@ -7739,9 +7739,9 @@
       }
     },
     "node_modules/mediabunny": {
-      "version": "1.29.0",
-      "resolved": "https://registry.npmjs.org/mediabunny/-/mediabunny-1.29.0.tgz",
-      "integrity": "sha512-18B8w/rhO/ph/AFsIXvzZg8RaSQZ+ZYfJ99MZlTjDmlgCT58jV3azrnWQ/OSquYDi8q0xmn64mnfTEHgww3+zw==",
+      "version": "1.29.1",
+      "resolved": "https://registry.npmjs.org/mediabunny/-/mediabunny-1.29.1.tgz",
+      "integrity": "sha512-RrlKs69MxRGa/l9cMGeI4hzuTSgchOGFHk9lIAuu9EcbSdJ05gDbRsTY67dojAiyUP3ic4PExij5OqDxqSv82Q==",
       "license": "MPL-2.0",
       "peer": true,
       "workspaces": [
@@ -12065,7 +12065,7 @@
     },
     "packages/mp3-encoder": {
       "name": "@mediabunny/mp3-encoder",
-      "version": "1.29.1",
+      "version": "1.30.0",
       "license": "MPL-2.0",
       "devDependencies": {
         "@types/emscripten": "^1.40.1"
diff --git a/package.json b/package.json
index cc3718c..a994713 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "mediabunny",
   "author": "Vanilagy",
-  "version": "1.29.1",
+  "version": "1.30.0",
   "description": "Pure TypeScript media toolkit for reading, writing, and converting media files, directly in the browser.",
   "type": "module",
   "workspaces": [
diff --git a/packages/mp3-encoder/package.json b/packages/mp3-encoder/package.json
index 8968b74..a4b4720 100644
--- a/packages/mp3-encoder/package.json
+++ b/packages/mp3-encoder/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@mediabunny/mp3-encoder",
   "author": "Vanilagy",
-  "version": "1.29.1",
+  "version": "1.30.0",
   "description": "MP3 encoder extension for Mediabunny, based on LAME.",
   "main": "./dist/bundles/mediabunny-mp3-encoder.mjs",
   "module": "./dist/bundles/mediabunny-mp3-encoder.mjs",
diff --git a/packages/mp3-encoder/src/index.ts b/packages/mp3-encoder/src/index.ts
index ba13a65..1519a19 100644
--- a/packages/mp3-encoder/src/index.ts
+++ b/packages/mp3-encoder/src/index.ts
@@ -12,6 +12,17 @@ import type { WorkerCommand, WorkerResponse, WorkerResponseData } from './shared
 // @ts-expect-error An esbuild plugin handles this, TypeScript doesn't need to understand
 import createWorker from './encode.worker';
 
+const MP3_ENCODER_LOADED_SYMBOL = Symbol.for('@mediabunny/mp3-encoder loaded');
+if ((globalThis as Record<symbol, unknown>)[MP3_ENCODER_LOADED_SYMBOL]) {
+	console.error(
+		'[WARNING]\n@mediabunny/mp3-encoder was loaded twice.'
+		+ ' This will likely cause the encoder not to work correctly.'
+		+ ' Check if multiple dependencies are importing different versions of @mediabunny/mp3-encoder,'
+		+ ' or if something is being bundled incorrectly.',
+	);
+}
+(globalThis as Record<symbol, unknown>)[MP3_ENCODER_LOADED_SYMBOL] = true;
+
 class Mp3Encoder extends CustomAudioEncoder {
 	private worker: Worker | null = null;
 	private nextMessageId = 0;
diff --git a/src/index.ts b/src/index.ts
index 18e0b0c..1ee6ded 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -9,6 +9,17 @@
 /// <reference types="dom-mediacapture-transform" preserve="true" />
 /// <reference types="dom-webcodecs" preserve="true" />
 
+const MEDIABUNNY_LOADED_SYMBOL = Symbol.for('mediabunny loaded');
+if ((globalThis as Record<symbol, unknown>)[MEDIABUNNY_LOADED_SYMBOL]) {
+	console.error(
+		'[WARNING]\nMediabunny was loaded twice.'
+		+ ' This will likely cause Mediabunny not to work correctly.'
+		+ ' Check if multiple dependencies are importing different versions of Mediabunny,'
+		+ ' or if something is being bundled incorrectly.',
+	);
+}
+(globalThis as Record<symbol, unknown>)[MEDIABUNNY_LOADED_SYMBOL] = true;
+
 export {
 	Output,
 	OutputOptions,
diff --git a/src/source.ts b/src/source.ts
index 7c9a25e..f7aa0df 100644
--- a/src/source.ts
+++ b/src/source.ts
@@ -324,6 +324,9 @@ export type UrlSourceOptions = {
 	/**
 	 * The [`RequestInit`](https://developer.mozilla.org/en-US/docs/Web/API/RequestInit) used by the Fetch API. Can be
 	 * used to further control the requests, such as setting custom headers.
+	 *
+	 * All fields will work except for `signal` and `headers.Range`; these will be overridden by Mediabunny. If you want
+	 * to cancel ongoing requests, use {@link Input.dispose}.
 	 */
 	requestInit?: RequestInit;
 
@@ -368,7 +371,12 @@ export class UrlSource extends Source {
 		abortController: AbortController;
 	}>();
 
-	/** Creates a new {@link UrlSource} backed by the resource at the specified URL. */
+	/**
+	 * Creates a new {@link UrlSource} backed by the resource at the specified URL.
+	 *
+	 * When passing a `Request` instance, note that the `signal` and `headers.Range` options will be overridden by
+	 * Mediabunny. If you want to cancel ongoing requests, use {@link Input.dispose}.
+	 */
 	constructor(
 		url: string | URL | Request,
 		options: UrlSourceOptions = {},