diff --git a/billsplit/lib/ui/home_screen.dart b/billsplit/lib/ui/home_screen.dart
index dcdec10f..04c4e81d 100644
--- a/billsplit/lib/ui/home_screen.dart
+++ b/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);
diff --git a/billsplit/lib/ui/receipt_screen.dart b/billsplit/lib/ui/receipt_screen.dart
index 0f881eb5..c307d210 100644
--- a/billsplit/lib/ui/receipt_screen.dart
+++ b/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) {
diff --git a/billsplit/linux/flutter/generated_plugin_registrant.cc b/billsplit/linux/flutter/generated_plugin_registrant.cc
index e71a16d2..64a0ecea 100644
--- a/billsplit/linux/flutter/generated_plugin_registrant.cc
+++ b/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);
 }
diff --git a/billsplit/linux/flutter/generated_plugins.cmake b/billsplit/linux/flutter/generated_plugins.cmake
index be1ee3e5..a630fa93 100644
--- a/billsplit/linux/flutter/generated_plugins.cmake
+++ b/billsplit/linux/flutter/generated_plugins.cmake
@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  file_selector_linux
 )
 
 list(APPEND FLUTTER_FFI_PLUGIN_LIST
diff --git a/billsplit/macos/Flutter/GeneratedPluginRegistrant.swift b/billsplit/macos/Flutter/GeneratedPluginRegistrant.swift
index 774a6b8b..14b5f7c7 100644
--- a/billsplit/macos/Flutter/GeneratedPluginRegistrant.swift
+++ b/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"))
 }
diff --git a/billsplit/pubspec.lock b/billsplit/pubspec.lock
index 141cfb71..95935915 100644
--- a/billsplit/pubspec.lock
+++ b/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"
diff --git a/billsplit/pubspec.yaml b/billsplit/pubspec.yaml
index c9402893..869f870c 100644
--- a/billsplit/pubspec.yaml
+++ b/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:
diff --git a/billsplit/test/helpers.dart b/billsplit/test/helpers.dart
index 597fc2a5..d341bb1c 100644
--- a/billsplit/test/helpers.dart
+++ b/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.
diff --git a/billsplit/test/xlsx_extra_test.dart b/billsplit/test/xlsx_extra_test.dart
index 9d5516f5..fcf912d9 100644
--- a/billsplit/test/xlsx_extra_test.dart
+++ b/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);
+  });
 }
diff --git a/billsplit/windows/flutter/generated_plugin_registrant.cc b/billsplit/windows/flutter/generated_plugin_registrant.cc
index 8b6d4680..77ab7a09 100644
--- a/billsplit/windows/flutter/generated_plugin_registrant.cc
+++ b/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"));
 }
diff --git a/billsplit/windows/flutter/generated_plugins.cmake b/billsplit/windows/flutter/generated_plugins.cmake
index 3ad69c61..277a56f8 100644
--- a/billsplit/windows/flutter/generated_plugins.cmake
+++ b/billsplit/windows/flutter/generated_plugins.cmake
@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  file_selector_windows
 )
 
 list(APPEND FLUTTER_FFI_PLUGIN_LIST
diff --git a/docs/superpowers/contracts/billsplit-apk-buildable-2026-08-03.json b/docs/superpowers/contracts/billsplit-apk-buildable-2026-08-03.json
new file mode 100644
index 00000000..44dd88fb
--- /dev/null
+++ b/docs/superpowers/contracts/billsplit-apk-buildable-2026-08-03.json
@@ -0,0 +1,19 @@
+{
+  "title": "Make billsplit's APK buildable and stop the CI mirror fighting a dirty tree",
+  "objective": "billsplit had never produced an Android APK: file_picker 11.0.3, the latest release, cannot compile under AGP 9 in either built-in-Kotlin mode. Replace it with the official file_selector so the app builds, verify the launcher icon from the built artifact rather than from a preview, keep the build inside this machine's 2 GB memory budget, and make the pre-push CI mirror stop failing whenever the shared checkout has uncommitted work.",
+  "acceptance_criteria": [
+    "flutter build apk --debug succeeds",
+    "The launcher icon extracted from the APK is the charcoal + gold perforated-receipt glyph and does not match the stock Flutter beach icon",
+    "Peak PSS across the build's JVM and Dart processes stays under 2 GiB, measured from /proc/<pid>/smaps_rollup",
+    "flutter analyze is clean, all tests pass, and billsplit holds 100% line coverage with no coverage ignores",
+    "meta/scripts/ci_mirror.sh passes while the working tree is dirty, leaves every uncommitted file byte-identical, and removes its temporary worktree",
+    "billsplit's Gradle and AGP versions stay identical to the sibling Flutter apps"
+  ],
+  "out_of_scope": [
+    "Pinning AGP 8 or otherwise diverging billsplit's Android toolchain from habit_stack, home_inventory, todo and diet_guard_app",
+    "Installing or running the APK on the phone; the icon is verified from the artifact, not from a device launcher",
+    "Any change to the split engine, xlsx export format, or e-paragon parsing",
+    "Upgrading the other dependencies pub reports as outdated"
+  ],
+  "verifier": "flutter analyze, flutter test --no-pub --coverage and python3 -m python_pkg.billsplit_coverage inside billsplit; flutter build apk --debug followed by unzipping the APK and rendering its ic_launcher assets; a PSS sampler over the build's processes; bash meta/scripts/ci_mirror.sh run deliberately against a dirty tree with before/after md5 of an uncommitted file; shellcheck on the rewritten script; and pre-commit run --files on the staged set inside a 2G cgroup"
+}
diff --git a/docs/superpowers/evidence/billsplit-apk-buildable-2026-08-03.json b/docs/superpowers/evidence/billsplit-apk-buildable-2026-08-03.json
new file mode 100644
index 00000000..7138bc32
--- /dev/null
+++ b/docs/superpowers/evidence/billsplit-apk-buildable-2026-08-03.json
@@ -0,0 +1,63 @@
+{
+  "intent": "Make billsplit actually build an Android APK so its launcher icon can be verified from the built artifact, bring that build inside the machine's 2 GB memory budget, and stop the pre-push CI mirror from failing whenever the shared checkout is dirty.",
+  "scope": [
+    "billsplit/pubspec.yaml — file_picker replaced by file_selector",
+    "billsplit/lib/ui/home_screen.dart and receipt_screen.dart — the two picker call sites",
+    "billsplit/test/helpers.dart — platform fake replaces the method-channel mock",
+    "billsplit/test/xlsx_extra_test.dart — covers the real on-disk export writer",
+    "meta/scripts/ci_mirror.sh — gates now run in a throwaway worktree",
+    "Non-goal: changing billsplit's Gradle/AGP versions, which are byte-identical to the four sibling apps and were never the fault",
+    "Non-goal: any change to split/export logic or the xlsx format"
+  ],
+  "changes": [
+    "Replaced file_picker with the official file_selector. file_picker 11.0.3 is the LATEST on pub.dev and is unfixably wedged under AGP 9: 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`), while with built-in Kotlin on its buildscript leaks KGP onto the global classpath via rootProject.allprojects and AGP rejects every module. Diagnosis rested on billsplit's android/app/build.gradle.kts and settings.gradle.kts being byte-identical to habit_stack, home_inventory and diet_guard_app, which all build — the dependency was the only difference.",
+    "Ported the two call sites: FilePicker.pickFiles -> openFile plus XFile.readAsBytes, and FilePicker.saveFile -> getSaveLocation plus an explicit write, since file_selector returns a destination and leaves writing to the caller.",
+    "Introduced an injectable ExportWriter seam (writeExport / debugSetExportWriter) for that write. Necessary, not decorative: file_picker performed the write inside the plugin so widget tests never touched the disk, whereas a real dart:io future never completes inside testWidgets' fake-async zone. Verified directly with a throwaway probe — a saveTo future was still pending after both pumpAndSettle and runAsync.",
+    "Swapped the test double from a MethodChannel mock to a FileSelectorPlatform fake, because file_selector speaks Pigeon and a channel mock would not intercept it.",
+    "Added a plain (non-widget) test exercising the real disk writer, restoring 100% line coverage without an ignore.",
+    "Rewrote ci_mirror.sh to run pre-commit --all-files and the pytest gate inside a disposable `git worktree add --detach HEAD`, removing the stash of the live tree entirely."
+  ],
+  "verification": [
+    {
+      "command": "flutter build apk --debug",
+      "result": "pass",
+      "evidence": "'Built build/app/outputs/flutter-apk/app-debug.apk' (143M). The first APK this app has ever produced; previously it failed at :app:compileDebugJavaWithJavac."
+    },
+    {
+      "command": "unzip the APK and render res/mipmap-xxxhdpi-v4/ic_launcher.png and res/drawable-xxxhdpi-v4/ic_launcher_foreground.png",
+      "result": "pass",
+      "evidence": "Both show the charcoal field with the gold perforated-receipt glyph. Neither matches the stock Flutter beach icon (md5 6270344430679711b81476e29878caa7). The icon is now verified from the built artifact rather than from a preview sheet."
+    },
+    {
+      "command": "PSS summed from /proc/<pid>/smaps_rollup across the build's JVM and Dart processes",
+      "result": "pass",
+      "evidence": "Peak 1.86 GiB, inside the 2 GB budget. Earlier attempts measured 2.03 and 3.01 GiB; removing file_picker also removed the flutter_plugin_android_lifecycle module and the built-in-Kotlin thrash."
+    },
+    {
+      "command": "flutter analyze && flutter test --no-pub --coverage && python3 -m python_pkg.billsplit_coverage",
+      "result": "pass",
+      "evidence": "'No issues found!', 60 tests passed, '100% line coverage across 11 lib files.'"
+    },
+    {
+      "command": "bash meta/scripts/ci_mirror.sh with the working tree deliberately dirty",
+      "result": "pass",
+      "evidence": "'all CI gates passed locally — safe to push' with eight modified files present, the exact condition that previously aborted the push. main.sh md5 unchanged at 262c91612bf9 across the run, and no worktree or /tmp/ci-mirror-* directory left behind."
+    },
+    {
+      "command": "shellcheck meta/scripts/ci_mirror.sh",
+      "result": "pass",
+      "evidence": "No findings."
+    }
+  ],
+  "risks": [
+    "The export write moved from the plugin into the app, so a failure now surfaces through the app's own catch as 'Export failed' rather than as a plugin exception. Behaviour on a real device is unverified — the APK was built but never installed or run.",
+    "writeExport is process-global mutable state. clearChannelMocks restores it, but a test that swaps it without going through the helper could leak the stub into later tests.",
+    "file_selector's save dialog is a different native flow from file_picker's; the Android and Linux pickers should be exercised by hand before trusting the export path in daily use.",
+    "ci_mirror.sh now gates HEAD rather than the working tree. That is the correct mirror of CI, but it means uncommitted work is no longer covered by the pre-push gate — it is checked at commit time instead."
+  ],
+  "rollback": [
+    "git revert the commit, then `flutter pub get` inside billsplit to restore file_picker. The APK will stop building again, which is the pre-change state, not a new fault.",
+    "Reverting ci_mirror.sh reinstates the stash-based gate and with it the spurious push failures on a dirty shared checkout; prefer keeping that hunk.",
+    "After any rollback, re-run flutter test: helpers.dart, receipt_screen.dart and xlsx_extra_test.dart must move together, since the platform fake and the ExportWriter seam are coupled."
+  ]
+}
diff --git a/meta/scripts/ci_mirror.sh b/meta/scripts/ci_mirror.sh
index 6fbd1a20..32ab2734 100755
--- a/meta/scripts/ci_mirror.sh
+++ b/meta/scripts/ci_mirror.sh
@@ -35,61 +35,90 @@ readonly REQ_PATH="$ROOT/$REQUIREMENTS_FILE"
 log() { printf 'ci-mirror: %s\n' "$1" >&2; }
 
 fail() {
-    log "FAILED — $1"
-    log "CI would be red. Fix the above, or 'git push --no-verify' to override."
-    exit 1
+	log "FAILED — $1"
+	log "CI would be red. Fix the above, or 'git push --no-verify' to override."
+	exit 1
 }
 
 require_file() {
-    if [[ ! -f "$REQ_PATH" ]]; then
-        fail "requirements file not found: $REQ_PATH"
-    fi
+	if [[ ! -f "$REQ_PATH" ]]; then
+		fail "requirements file not found: $REQ_PATH"
+	fi
 }
 
 # Rebuild the venv only when requirements.txt changed since the last build.
 ensure_venv() {
-    local current stored
-    current="$(sha256sum "$REQ_PATH" | cut -d' ' -f1)"
-    stored=""
-    if [[ -f "$HASH_FILE" ]]; then
-        stored="$(cat "$HASH_FILE")"
-    fi
+	local current stored
+	current="$(sha256sum "$REQ_PATH" | cut -d' ' -f1)"
+	stored=""
+	if [[ -f "$HASH_FILE" ]]; then
+		stored="$(cat "$HASH_FILE")"
+	fi
 
-    if [[ -x "$VENV_DIR/bin/python" && "$current" == "$stored" ]]; then
-        log "venv up to date (requirements.txt unchanged)"
-        return
-    fi
+	if [[ -x "$VENV_DIR/bin/python" && "$current" == "$stored" ]]; then
+		log "venv up to date (requirements.txt unchanged)"
+		return
+	fi
 
-    log "requirements.txt changed — rebuilding clean venv (mirrors CI install)"
-    rm -rf "$VENV_DIR"
-    python3 -m venv "$VENV_DIR"
-    "$VENV_DIR/bin/python" -m pip install --quiet --upgrade pip \
-        || fail "pip self-upgrade in the clean venv"
-    "$VENV_DIR/bin/python" -m pip install --quiet -r "$REQ_PATH" \
-        || fail "pip install -r $REQUIREMENTS_FILE (a dep may be undeclared)"
-    printf '%s' "$current" > "$HASH_FILE"
-    log "clean venv ready"
+	log "requirements.txt changed — rebuilding clean venv (mirrors CI install)"
+	rm -rf "$VENV_DIR"
+	python3 -m venv "$VENV_DIR"
+	"$VENV_DIR/bin/python" -m pip install --quiet --upgrade pip ||
+		fail "pip self-upgrade in the clean venv"
+	"$VENV_DIR/bin/python" -m pip install --quiet -r "$REQ_PATH" ||
+		fail "pip install -r $REQUIREMENTS_FILE (a dep may be undeclared)"
+	printf '%s' "$current" >"$HASH_FILE"
+	log "clean venv ready"
 }
 
-run_precommit_all_files() {
-    # Skip pytest-coverage here: it is a pre-commit-stage hook that would run
-    # in the system env (not our clean venv) and duplicate run_pytest below.
-    log "pre-commit run --all-files (mirrors the pre-commit workflow)"
-    SKIP=pytest-coverage pre-commit run --all-files || fail "pre-commit --all-files"
+# Disposable clean checkout of HEAD; see run_gates_in_clean_worktree.
+CHECKOUT=""
+
+cleanup_checkout() {
+	if [[ -n "$CHECKOUT" && -d "$CHECKOUT" ]]; then
+		git -C "$ROOT" worktree remove --force "$CHECKOUT" >/dev/null 2>&1 || true
+		rm -rf "$CHECKOUT"
+		git -C "$ROOT" worktree prune >/dev/null 2>&1 || true
+	fi
 }
 
-run_pytest_clean_venv() {
-    log "changed-packages pytest in the clean venv (OOM-safe runner)"
-    "$VENV_DIR/bin/python" meta/scripts/pytest_changed_packages.py \
-        || fail "pytest_changed_packages (clean requirements.txt venv)"
+trap cleanup_checkout EXIT
+
+# Run the gates against a throwaway worktree at HEAD rather than the live tree.
+#
+# `pre-commit run --all-files` stashes unstaged changes, runs the hooks, then
+# restores. In a shared checkout that is actively hostile: when another agent
+# (or the user) has uncommitted work that collides with a hook's auto-fix, the
+# restore conflicts, pre-commit rolls the fixes back, and the push fails with a
+# diagnostic that points at the innocent hook rather than at the collision.
+# Worse, the stash window puts someone else's uncommitted work at risk, which
+# is exactly what memories/git-rules.md forbids.
+#
+# A clean worktree removes the stash entirely and is a truer mirror of CI,
+# which always builds from a pristine checkout and never sees a dirty file.
+run_gates_in_clean_worktree() {
+	CHECKOUT="$(mktemp -d -t ci-mirror-XXXXXX)"
+	rm -rf "$CHECKOUT"
+	log "checking out HEAD into a clean worktree (no stash of your tree)"
+	git -C "$ROOT" worktree add --detach --quiet "$CHECKOUT" HEAD ||
+		fail "could not create the clean worktree"
+
+	# Skip pytest-coverage here: it is a pre-commit-stage hook that would run
+	# in the system env (not our clean venv) and duplicate the pytest run below.
+	log "pre-commit run --all-files (mirrors the pre-commit workflow)"
+	(cd "$CHECKOUT" && SKIP=pytest-coverage pre-commit run --all-files) ||
+		fail "pre-commit --all-files"
+
+	log "changed-packages pytest in the clean venv (OOM-safe runner)"
+	(cd "$CHECKOUT" && "$VENV_DIR/bin/python" meta/scripts/pytest_changed_packages.py) ||
+		fail "pytest_changed_packages (clean requirements.txt venv)"
 }
 
 main() {
-    require_file
-    ensure_venv
-    run_precommit_all_files
-    run_pytest_clean_venv
-    log "all CI gates passed locally — safe to push"
+	require_file
+	ensure_venv
+	run_gates_in_clean_worktree
+	log "all CI gates passed locally — safe to push"
 }
 
 main "$@"