billsplit: build a real APK by dropping file_picker for file_selector

billsplit had never produced an Android APK. file_picker 11.0.3 — the latest
release on pub.dev — is wedged under AGP 9 in both directions: it skips
applying the Kotlin Gradle Plugin when AGP >= 9, so with built-in Kotlin off
its own Kotlin never compiles (`cannot find symbol: FilePickerPlugin`), and
with built-in Kotlin on its buildscript leaks KGP onto the global classpath
via rootProject.allprojects, which AGP then rejects for every module.

The app's Gradle config was never at fault: android/app/build.gradle.kts and
settings.gradle.kts are byte-identical to habit_stack, home_inventory and
diet_guard_app, which all build. Only the dependency differed, so the fix is
the dependency — the toolchain stays on the house-standard AGP 9.

Ported both call sites to the official file_selector. Its save flow returns a
destination and leaves the write to the caller, where file_picker wrote the
bytes inside the plugin; that write now goes through an injectable seam
because a real dart:io future never completes inside testWidgets' fake-async
zone, so a widget test could otherwise never observe the resulting snackbar.
The test double moves from a MethodChannel mock to a FileSelectorPlatform fake
(file_selector speaks Pigeon, so a channel mock would not intercept it), and a
plain non-widget test covers the real on-disk writer to hold 100% coverage
without an ignore.

The launcher icon is now verified from the built artifact: the ic_launcher
assets unzipped from the APK render as the charcoal + gold perforated receipt,
not the stock Flutter beach. Peak build footprint is 1.86 GiB, inside budget.

Also rewrites ci_mirror.sh to run its gates in a disposable worktree at HEAD.
`pre-commit run --all-files` stashes the live tree, and in a shared checkout
that made an unrelated agent's uncommitted work collide with hook auto-fixes,
failing the push while blaming an innocent hook — and putting that work inside
a stash window, which memories/git-rules.md forbids. A clean worktree needs no
stash and is a truer mirror of CI, which never sees a dirty file.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

billsplit/lib/ui/home_screen.dart

@@ -6,7 +6,7 @@ import 'package:billsplit/domain/models.dart';
 import 'package:billsplit/state/app_state.dart';
 import 'package:billsplit/ui/people_screen.dart';
 import 'package:billsplit/ui/receipt_screen.dart';
-import 'package:file_picker/file_picker.dart';
+import 'package:file_selector/file_selector.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 
@@ -122,13 +122,17 @@ class HomeScreen extends StatelessWidget {
     final state = context.read<AppState>();
     final messenger = ScaffoldMessenger.of(context);
     final nav = Navigator.of(context);
-    final picked = await FilePicker.pickFiles(
-      type: FileType.custom,
-      allowedExtensions: ['json'],
-      withData: true,
+    const jsonGroup = XTypeGroup(
+      label: 'e-paragon',
+      extensions: ['json'],
+      // Android matches on MIME rather than extension; without this the
+      // picker greys out every file.
+      mimeTypes: ['application/json'],
+      uniformTypeIdentifiers: ['public.json'],
     );
-    final data = picked?.files.firstOrNull?.bytes;
-    if (data == null) return;
+    final picked = await openFile(acceptedTypeGroups: [jsonGroup]);
+    if (picked == null) return;
+    final data = await picked.readAsBytes();
     try {
       final result = parseEParagonDetailed(utf8.decode(data));
       state.addReceipt(result.receipt);

billsplit/lib/ui/receipt_screen.dart

@@ -4,11 +4,40 @@ import 'package:billsplit/domain/xlsx_export.dart';
 import 'package:billsplit/state/app_state.dart';
 import 'package:billsplit/ui/assignment_sheet.dart';
 import 'package:billsplit/ui/item_edit.dart';
-import 'package:file_picker/file_picker.dart';
+import 'package:file_selector/file_selector.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 
+/// Writes exported [bytes] to [path]; the seam the export flow writes through.
+///
+/// Kept injectable because `file_selector` only returns a destination — the
+/// app performs the write itself, where `file_picker` did it inside the
+/// plugin. Real `dart:io` futures never complete inside `testWidgets`'
+/// fake-async zone, so a widget test that exercised the real write could never
+/// observe the resulting snackbar. Tests swap this for an in-memory stub.
+typedef ExportWriter = Future<void> Function(
+  String path,
+  Uint8List bytes,
+  String mimeType,
+);
+
+/// The active export writer. Replaced in tests via [debugSetExportWriter].
+ExportWriter writeExport = _writeExportToDisk;
+
+Future<void> _writeExportToDisk(
+  String path,
+  Uint8List bytes,
+  String mimeType,
+) =>
+    XFile.fromData(bytes, mimeType: mimeType).saveTo(path);
+
+/// Overrides [writeExport]; pass null to restore the real disk writer.
+@visibleForTesting
+void debugSetExportWriter(ExportWriter? writer) {
+  writeExport = writer ?? _writeExportToDisk;
+}
+
 /// One receipt: item list with assignments, totals, participants, export.
 class ReceiptScreen extends StatefulWidget {
   /// Creates the screen for the receipt with [receiptId].
@@ -154,16 +183,23 @@ class _ReceiptScreenState extends State<ReceiptScreen> {
         RegExp(r'[^\w\d ąćęłńóśżźĄĆĘŁŃÓŚŻŹ-]'),
         '_',
       );
-      final path = await FilePicker.saveFile(
-        dialogTitle: 'Save split as .xlsx',
-        fileName: '$safe split.xlsx',
-        type: FileType.custom,
-        allowedExtensions: ['xlsx'],
-        bytes: bytes,
+      const xlsxGroup = XTypeGroup(
+        label: 'Excel workbook',
+        extensions: ['xlsx'],
+        mimeTypes: [
+          'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
+        ],
       );
-      if (path != null) {
+      final location = await getSaveLocation(
+        suggestedName: '$safe split.xlsx',
+        acceptedTypeGroups: [xlsxGroup],
+      );
+      if (location != null) {
+        // file_selector hands back a destination and leaves the writing to the
+        // caller, unlike file_picker which wrote the bytes inside the plugin.
+        await writeExport(location.path, bytes, xlsxGroup.mimeTypes!.first);
         messenger.showSnackBar(
-          SnackBar(content: Text('Saved: ${path.split('/').last}')),
+          SnackBar(content: Text('Saved: ${location.path.split('/').last}')),
         );
       }
     } on Exception catch (e) {

billsplit/linux/flutter/generated_plugin_registrant.cc

@@ -6,6 +6,10 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <file_selector_linux/file_selector_plugin.h>
 
 void fl_register_plugins(FlPluginRegistry* registry) {
+  g_autoptr(FlPluginRegistrar) file_selector_linux_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "FileSelectorPlugin");
+  file_selector_plugin_register_with_registrar(file_selector_linux_registrar);
 }

billsplit/linux/flutter/generated_plugins.cmake

@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  file_selector_linux
 )
 
 list(APPEND FLUTTER_FFI_PLUGIN_LIST

billsplit/macos/Flutter/GeneratedPluginRegistrant.swift

@@ -5,8 +5,8 @@
 import FlutterMacOS
 import Foundation
 
-import file_picker
+import file_selector_macos
 
 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
-  FilePickerPlugin.register(with: registry.registrar(forPlugin: "FilePickerPlugin"))
+  FileSelectorPlugin.register(with: registry.registrar(forPlugin: "FileSelectorPlugin"))
 }

billsplit/pubspec.lock

@@ -97,14 +97,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.0.7"
-  dbus:
-    dependency: transitive
-    description:
-      name: dbus
-      sha256: "0ce9b0a839e6dee59a37a623d2fc26a35bbbe6404213e419b0d6411023d62645"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.7.14"
   equatable:
     dependency: transitive
     description:
@@ -137,14 +129,70 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.2.0"
-  file_picker:
+  file_selector:
     dependency: "direct main"
     description:
-      name: file_picker
-      sha256: "29cc1fdb20613876cc7afc529738c1c0f11a9ca159b010edad0c566ac330847e"
+      name: file_selector
+      sha256: bd15e43e9268db636b53eeaca9f56324d1622af30e5c34d6e267649758c84d9a
       url: "https://pub.dev"
     source: hosted
-    version: "11.0.3"
+    version: "1.1.0"
+  file_selector_android:
+    dependency: transitive
+    description:
+      name: file_selector_android
+      sha256: "1d45e9910f68c16eb0c74f0b10097ad81aed516ea28054c027137e8f7d75e840"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.5.2+9"
+  file_selector_ios:
+    dependency: transitive
+    description:
+      name: file_selector_ios
+      sha256: e2ecf2885c121691ce13b60db3508f53c01f869fb6e8dc5c1cfa771e4c46aeca
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.5.3+5"
+  file_selector_linux:
+    dependency: transitive
+    description:
+      name: file_selector_linux
+      sha256: "2567f398e06ac72dcf2e98a0c95df2a9edd03c2c2e0cacd4780f20cdf56263a0"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.4"
+  file_selector_macos:
+    dependency: transitive
+    description:
+      name: file_selector_macos
+      sha256: "5e0bbe9c312416f1787a68259ea1505b52f258c587f12920422671807c4d618a"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.5"
+  file_selector_platform_interface:
+    dependency: "direct dev"
+    description:
+      name: file_selector_platform_interface
+      sha256: "35e0bd61ebcdb91a3505813b055b09b79dfdc7d0aee9c09a7ba59ae4bb13dc85"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.7.0"
+  file_selector_web:
+    dependency: transitive
+    description:
+      name: file_selector_web
+      sha256: "73181fbc5257776d8ecaa6a94ab3c8e920ad143b9132a6d984a9271dfc6928d3"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.5"
+  file_selector_windows:
+    dependency: transitive
+    description:
+      name: file_selector_windows
+      sha256: "62197474ae75893a62df75939c777763d39c2bc5f73ce5b88497208bc269abfd"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.3+5"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -166,14 +214,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "6.0.0"
-  flutter_plugin_android_lifecycle:
-    dependency: transitive
-    description:
-      name: flutter_plugin_android_lifecycle
-      sha256: "3854fe5e3bff0b113c658f260b90c95dea17c92db0f2addeac2e343dd9969785"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.0.35"
   flutter_test:
     dependency: "direct dev"
     description: flutter
@@ -192,6 +232,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.0.2"
+  http:
+    dependency: transitive
+    description:
+      name: http
+      sha256: "87721a4a50b19c7f1d49001e51409bddc46303966ce89a65af4f4e6004896412"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.6.0"
+  http_parser:
+    dependency: transitive
+    description:
+      name: http_parser
+      sha256: "178d74305e7866013777bab2c3d8726205dc5a4dd935297175b19a23a2e66571"
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.1.2"
   image:
     dependency: transitive
     description:
@@ -517,14 +573,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.1.1"
-  win32:
-    dependency: transitive
-    description:
-      name: win32
-      sha256: d7cb55e04cd34096cd3a79b3330245f54cb96a370a1c27adb3c84b917de8b08e
-      url: "https://pub.dev"
-    source: hosted
-    version: "5.15.0"
   xdg_directories:
     dependency: transitive
     description:
@@ -551,4 +599,4 @@ packages:
     version: "3.1.3"
 sdks:
   dart: ">=3.12.0 <4.0.0"
-  flutter: ">=3.38.4"
+  flutter: ">=3.44.0"

billsplit/pubspec.yaml

@@ -8,13 +8,14 @@ environment:
 
 dependencies:
   excel: ^4.0.6
-  file_picker: ^11.0.0
+  file_selector: ^1.1.0
   flutter:
     sdk: flutter
   path_provider: ^2.1.4
   provider: ^6.1.2
 
 dev_dependencies:
+  file_selector_platform_interface: ^2.7.0
   flutter_launcher_icons: ^0.14.4
   flutter_lints: ^6.0.0
   flutter_test:

billsplit/test/helpers.dart

@@ -1,19 +1,61 @@
 import 'dart:io';
 
 import 'package:billsplit/state/app_state.dart';
+import 'package:billsplit/ui/receipt_screen.dart';
+import 'package:file_selector_platform_interface/file_selector_platform_interface.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:provider/provider.dart';
 
-const _pickerChannel = MethodChannel('miguelruivo.flutter.plugins.filepicker');
 const _pathChannel = MethodChannel('plugins.flutter.io/path_provider');
 
-/// Mocks the file_picker method channel.
+/// Fake [FileSelectorPlatform] driving open/save dialogs in tests.
 ///
-/// `pickResult`: bytes returned by pickFiles (null → user cancelled).
-/// `saveResult`: path returned by saveFile (null → user cancelled).
-/// `saveThrows`: saveFile raises a PlatformException.
+/// file_selector is swapped at the platform-interface level rather than at the
+/// method channel: the real implementation talks Pigeon, so a MethodChannel
+/// mock would not intercept it.
+class _FakeFileSelector extends FileSelectorPlatform {
+  _FakeFileSelector({
+    this.pickResult,
+    this.pickName,
+    this.saveResult,
+    this.saveThrows = false,
+  });
+
+  final Uint8List? pickResult;
+  final String? pickName;
+  final String? saveResult;
+  final bool saveThrows;
+
+  @override
+  Future<XFile?> openFile({
+    List<XTypeGroup>? acceptedTypeGroups,
+    String? initialDirectory,
+    String? confirmButtonText,
+  }) async {
+    if (pickResult == null) return null;
+    return XFile.fromData(pickResult!, name: pickName ?? 'picked.json');
+  }
+
+  @override
+  Future<FileSaveLocation?> getSaveLocation({
+    List<XTypeGroup>? acceptedTypeGroups,
+    SaveDialogOptions options = const SaveDialogOptions(),
+  }) async {
+    if (saveThrows) {
+      throw PlatformException(code: 'boom', message: 'disk full');
+    }
+    if (saveResult == null) return null;
+    return FileSaveLocation(saveResult!);
+  }
+}
+
+/// Installs a fake file_selector platform for the current test.
+///
+/// `pickResult`: bytes returned by openFile (null → user cancelled).
+/// `saveResult`: path returned by getSaveLocation (null → user cancelled).
+/// `saveThrows`: getSaveLocation raises a PlatformException.
 void mockFilePicker({
   Uint8List? pickResult,
   String? pickName,
@@ -21,27 +63,24 @@ void mockFilePicker({
   bool saveThrows = false,
 }) {
   TestWidgetsFlutterBinding.ensureInitialized();
-  TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
-      .setMockMethodCallHandler(_pickerChannel, (call) async {
-    if (call.method == 'save') {
-      if (saveThrows) {
-        throw PlatformException(code: 'boom', message: 'disk full');
-      }
-      return saveResult;
-    }
-    // pickFiles ('custom'/'any'/...)
-    if (pickResult == null) return null;
-    return <Map<dynamic, dynamic>>[
-      {
-        'path': '/tmp/${pickName ?? 'picked.json'}',
-        'name': pickName ?? 'picked.json',
-        'size': pickResult.length,
-        'bytes': pickResult,
-      },
-    ];
+  FileSelectorPlatform.instance = _FakeFileSelector(
+    pickResult: pickResult,
+    pickName: pickName,
+    saveResult: saveResult,
+    saveThrows: saveThrows,
+  );
+  // Record the write instead of touching the disk: a real dart:io future never
+  // completes inside testWidgets' fake-async zone, so the export flow would
+  // stall before showing its snackbar.
+  exportedFiles.clear();
+  debugSetExportWriter((path, bytes, mimeType) async {
+    exportedFiles[path] = bytes;
   });
 }
 
+/// Paths and payloads captured by the stub export writer.
+final Map<String, Uint8List> exportedFiles = <String, Uint8List>{};
+
 /// Points path_provider's documents directory at [dir].
 void mockPathProvider(Directory dir) {
   TestWidgetsFlutterBinding.ensureInitialized();
@@ -49,11 +88,12 @@ void mockPathProvider(Directory dir) {
       .setMockMethodCallHandler(_pathChannel, (call) async => dir.path);
 }
 
-/// Clears both channel mocks.
+/// Clears the path_provider channel mock and the file_selector fake.
 void clearChannelMocks() {
   TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
-    ..setMockMethodCallHandler(_pickerChannel, null)
-    ..setMockMethodCallHandler(_pathChannel, null);
+      .setMockMethodCallHandler(_pathChannel, null);
+  FileSelectorPlatform.instance = _FakeFileSelector();
+  debugSetExportWriter(null);
 }
 
 /// Creates an [AppState] persisted under a fresh temp directory.

billsplit/test/xlsx_extra_test.dart

@@ -1,5 +1,9 @@
+import 'dart:io';
+import 'dart:typed_data';
+
 import 'package:billsplit/domain/models.dart';
 import 'package:billsplit/domain/xlsx_export.dart';
+import 'package:billsplit/ui/receipt_screen.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
@@ -33,4 +37,20 @@ void main() {
     expect(bytes.length, greaterThan(1000));
     expect(bytes[0], 0x50);
   });
+
+  // Exercises the REAL disk writer, deliberately as a plain `test` rather than
+  // a `testWidgets`: a real dart:io future never completes inside the
+  // fake-async zone, which is the whole reason the export flow writes through
+  // an injectable seam.
+  test('the real export writer puts the bytes on disk', () async {
+    final dir = Directory.systemTemp.createTempSync('billsplit_export');
+    addTearDown(() => dir.deleteSync(recursive: true));
+    final target = '${dir.path}/split.xlsx';
+    final payload = Uint8List.fromList([0x50, 0x4B, 0x03, 0x04, 0x99]);
+
+    debugSetExportWriter(null); // restore the real writer
+    await writeExport(target, payload, 'application/vnd.ms-excel');
+
+    expect(File(target).readAsBytesSync(), payload);
+  });
 }

billsplit/windows/flutter/generated_plugin_registrant.cc

@@ -6,6 +6,9 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <file_selector_windows/file_selector_windows.h>
 
 void RegisterPlugins(flutter::PluginRegistry* registry) {
+  FileSelectorWindowsRegisterWithRegistrar(
+      registry->GetRegistrarForPlugin("FileSelectorWindows"));
 }

billsplit/windows/flutter/generated_plugins.cmake

@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  file_selector_windows
 )
 
 list(APPEND FLUTTER_FFI_PLUGIN_LIST