refactor(fetcher): drop the Android DownloadManager fallback

apps/computer-vision/package.json

@@ -38,7 +38,7 @@
     "expo-router": "~56.2.9",
     "react": "19.2.3",
     "react-native": "0.85.3",
-    "react-native-blob-util": "^0.24.0",
+    "react-native-blob-util": "^0.25.0",
     "react-native-drawer-layout": "^4.2.2",
     "react-native-executorch": "workspace:*",
     "react-native-gesture-handler": "~2.31.1",

apps/nlp/package.json

@@ -37,7 +37,7 @@
     "expo-router": "~56.2.9",
     "react": "19.2.3",
     "react-native": "0.85.3",
-    "react-native-blob-util": "^0.24.0",
+    "react-native-blob-util": "^0.25.0",
     "react-native-drawer-layout": "^4.2.2",
     "react-native-executorch": "workspace:*",
     "react-native-gesture-handler": "~2.31.1",

apps/speech/package.json

@@ -28,7 +28,7 @@
     "react": "19.2.3",
     "react-native": "0.85.3",
     "react-native-audio-api": "0.13.1",
-    "react-native-blob-util": "^0.24.0",
+    "react-native-blob-util": "^0.25.0",
     "react-native-device-info": "^15.0.2",
     "react-native-drawer-layout": "^4.2.2",
     "react-native-executorch": "workspace:*",

docs/docs/01-fundamentals/02-downloading-models.md

@@ -98,9 +98,7 @@ common needs:
   isn't reported the same as a small tokenizer.
 - [**`signal`**](../06-api-reference/interfaces/DownloadOptions.md#signal) — an
   `AbortSignal` to cancel. The bytes fetched so far are kept so a later download
-  of the same source resumes instead of restarting (except on Android without
-  the optional background downloader, where the system `DownloadManager` discards
-  a cancelled transfer).
+  of the same source resumes instead of restarting.
 - [**`forceDownload`**](../06-api-reference/interfaces/DownloadOptions.md#forcedownload) —
   re-download even when cached.
 
@@ -111,10 +109,8 @@ launches fast:
 
 - A file that is already cached resolves immediately — no network round trip.
 - Concurrent downloads of the same URL are deduplicated into one transfer.
-- Without extra dependencies, fetching falls back to what each platform supports
-  natively: the system `DownloadManager` on Android (which continues in the
-  background), and a streaming request on iOS (which pauses when the app is
-  suspended and resumes when reopened).
+- Without extra dependencies, both platforms fall back to the same streaming
+  request, which pauses when the app is suspended and resumes when reopened.
 - To keep transfers running in the background across both iOS and Android and survive
   the app being killed, install the optional peer dependency
   [`@kesha-antonov/react-native-background-downloader`](https://github.com/kesha-antonov/react-native-background-downloader)

packages/react-native-executorch/__tests__/fetcher/androidBackend.test.ts

@@ -1,12 +1,18 @@
 /**
  * The Android download path.
  *
- * `src/fetcher/fetcher.ts` decides between the two backends once, at module
- * scope (`const IS_ANDROID = Platform.OS === 'android'`), so exercising the
- * Android branch means re-importing the module with a different `Platform`.
- * That also re-instantiates the blob-util mock, so every handle used here has
- * to come from the same fresh module registry — hence the `load()` helper
- * rather than the file-level imports the other fetcher suites use.
+ * Android used to have a backend of its own — the system `DownloadManager` —
+ * because blob-util's in-process reader stopped after 8 KB
+ * (RonRadtke/react-native-blob-util#475). That fix shipped in 0.24.11, so both
+ * platforms now share the streaming fallback, and what is left that is specific
+ * to Android is the cache directory.
+ *
+ * `src/fetcher/fetcher.ts` derives that directory once, at module scope
+ * (`const IS_ANDROID = Platform.OS === 'android'`), so exercising the Android
+ * branch means re-importing the module with a different `Platform`. That also
+ * re-instantiates the blob-util mock, so every handle used here has to come from
+ * the same fresh module registry — hence the `load()` helper rather than the
+ * file-level imports the other fetcher suites use.
  */
 import type { Route } from '../support/blobUtilMock';
 
@@ -16,8 +22,12 @@ const HF_COUNTER = 'https://huggingface.co/software-mansion/model/resolve/main/c
 type Android = {
   download: typeof import('../../src/fetcher/fetcher').download;
   serve: (url: string, route?: Route) => void;
+  requests: () => readonly { method: string; url: string; headers: Record<string, string> }[];
   paths: () => string[];
   readText: (path: string) => string | undefined;
+  write: (path: string, contents: string) => void;
+  remove: (path: string) => void;
+  has: (path: string) => boolean;
   countRequests: (method: string, url: string) => number;
 };
 
@@ -49,8 +59,12 @@ const load = async (): Promise<Android> => {
   return {
     download,
     serve: blobUtil.fakeNet.serve,
+    requests: blobUtil.fakeNet.requests,
     paths: blobUtil.fakeFs.paths,
     readText: blobUtil.fakeFs.readText,
+    write: blobUtil.fakeFs.write,
+    remove: blobUtil.fakeFs.remove,
+    has: blobUtil.fakeFs.has,
     countRequests: blobUtil.fakeNet.countRequests,
   };
 };
@@ -71,30 +85,36 @@ describe('download on Android', () => {
     expect(android.readText(path)).toBe('model-bytes');
   });
 
-  it('downloads through a temporary file and moves it into place', async () => {
+  it('resumes from a partial file with a Range request, like iOS', async () => {
     const android = await load();
-    android.serve(URL_A);
+    android.serve(URL_A, { body: 'abcdefgh' });
 
-    await android.download(URL_A);
-
-    expect(android.paths().filter((p) => p.endsWith('.downloading'))).toEqual([]);
-  });
+    // Stage the aftermath of an interrupted download: the cached file is gone
+    // and `partial` bytes sit next to it. DownloadManager never resumed through
+    // a Range request, so this is what proves the shared backend is in use.
+    const path = await android.download(URL_A);
+    android.remove(path);
+    android.write(`${path}.partial`, 'abc');
+    const before = android.requests().length;
 
-  it('treats an empty response as a failure, since DownloadManager reports no status', async () => {
-    const android = await load();
-    android.serve(URL_A, { body: '' });
+    await android.download(URL_A);
 
-    await expect(android.download(URL_A)).rejects.toThrow(/empty response/);
-    expect(android.paths()).toEqual([]);
+    const ranged = android
+      .requests()
+      .slice(before)
+      .find((r) => r.headers.Range !== undefined);
+    expect(ranged?.headers.Range).toBe('bytes=3-');
+    expect(android.readText(path)).toBe('abcdefgh');
+    expect(android.has(`${path}.partial`)).toBe(false);
   });
 
-  it('does not send a Range header — DownloadManager resumes on its own', async () => {
+  it('leaves no temporary files behind on success', async () => {
     const android = await load();
     android.serve(URL_A);
 
     await android.download(URL_A);
 
-    expect(android.countRequests('GET', URL_A)).toBe(1);
+    expect(android.paths().filter((p) => /\.(partial|chunk|downloading)$/.test(p))).toEqual([]);
   });
 
   it('serves a second call from the cache', async () => {

packages/react-native-executorch/__tests__/fetcher/download.test.ts

@@ -356,7 +356,7 @@ describe('download — concurrent callers', () => {
   });
 });
 
-describe('download — iOS resume', () => {
+describe('download — resume', () => {
   /**
    * Stages the aftermath of an interrupted download: the cached file is gone
    * and `partial` bytes are sitting next to it. The cache path is only known

packages/react-native-executorch/__tests__/support/blobUtilMock.ts

@@ -210,7 +210,7 @@ type FetchTask = Promise<{ info: () => { status: number } }> & {
   progress: (config: { count?: number }, cb: ProgressCallback) => FetchTask;
   // Undocumented in blob-util's typings, but real: it reports the response
   // state, so `src/` learns the status as soon as the headers land rather than
-  // only once the body is complete. See `downloadUrlViaIosStream`.
+  // only once the body is complete. See `downloadUrlViaStream`.
   stateChange: (cb: StateChangeCallback) => FetchTask;
   cancel: () => void;
 };
@@ -223,14 +223,13 @@ class CancelledError extends Error {
 }
 
 type Config = {
-  /** Destination path for a streamed download (iOS-style). */
+  /** Destination path for a streamed download. */
   path?: string;
   fileCache?: boolean;
-  addAndroidDownloads?: { path?: string; useDownloadManager?: boolean; [key: string]: unknown };
 };
 
 function startFetch(config: Config, method: string, url: string, headers: Record<string, string>) {
-  const dest = config.addAndroidDownloads?.path ?? config.path;
+  const dest = config.path;
   requests.push({ method, url, headers });
 
   let onProgress: ProgressCallback | undefined;

packages/react-native-executorch/package.json

@@ -141,7 +141,7 @@
     "@kesha-antonov/react-native-background-downloader": ">=4.4.0",
     "react": "*",
     "react-native": "*",
-    "react-native-blob-util": "^0.24.0",
+    "react-native-blob-util": ">=0.24.11",
     "react-native-worklets": ">=0.10.0 <0.13.0"
   },
   "peerDependenciesMeta": {
@@ -160,7 +160,7 @@
     "jest": "^29.7.0",
     "react": "19.2.0",
     "react-native": "0.83.6",
-    "react-native-blob-util": "^0.24.0",
+    "react-native-blob-util": "^0.25.0",
     "react-native-builder-bob": "^0.40.18",
     "react-native-worklets": "0.10.3",
     "test-renderer": "^1.2.0",