android: scan the web recipe card's QR and import the look it points at

The landing page's QR card now carries a link to `GET
/api/photos/:id/preset.recipe`, so the app can pick a look up off a
screen instead of a file. PRESETS gains a SCAN QR chip next to IMPORT:
the code is decoded, checked against the preset route, fetched, and
stored through the same `storeImportedRecipe` path IMPORT already uses,
so an imported look and a scanned look land in one place.

Scanning runs on `expo-camera`, not the viewfinder's vision-camera:
v5's object output is iOS-only, Android's `createObjectOutput` throws.
That is a second camera library in the app, so the sheet pauses the
viewfinder (`paused` prop) — CameraX will not let two clients hold one
lens. A native rebuild is required for the new module.

The code holds a URL, never the recipe, so anything that is not the
preset route is refused by name rather than silently dropped. On a
release APK the plain-HTTP link is blocked by Android's cleartext
policy; debug builds have it on. Noted in 7_SCAN_QR.md along with the
web side, the regex, and the paused-viewfinder rule.

7_SCAN_QR.md

@@ -0,0 +1,158 @@
+# 7 — SCAN QR: quét mã trên trang web để import recipe vào app
+
+Nhánh: `feat/vision-camera-v5`. Ngày: 2026-09-06.
+Nguồn đối chiếu: nhánh `recipes-web`, commit **`8a889db`** ("web: the QR card
+hands out the look that made the photo") — bản web đã làm, đã đo, đang chạy ở
+`http://localhost:8090`.
+
+Đây là ghi chú cho phần mềm Android **và đã implement trên nhánh này**. Khác
+các ghi chú 1–6 (chỉ nêu yêu cầu), ghi chú này ghi lại cả hai nửa: web đã mở ra
+cái gì, và app đọc cái đó bằng cách nào.
+
+---
+
+## 1. Web đã mở ra cái gì (phía `recipes-web`)
+
+Trang admin có thêm **checkbox thứ tư `qr`** cạnh `strip / tester / creator`.
+Tick `qr` cho một ảnh nghĩa là: ảnh đó xuất hiện ở thẻ QR trên landing page.
+
+Ảnh được tick `qr` phải có **preset** (`photos.recipe`, cột JSON). Khi có,
+thẻ QR trên landing trỏ tới một route công khai mới của backend:
+
+```
+GET /api/photos/:id/preset.recipe
+```
+
+| Trường hợp | Trả về |
+| --- | --- |
+| `id` không phải số, không có hàng, `recipe IS NULL`, hoặc ảnh không tick `qr` | `404` |
+| Hợp lệ | `200`, `content-type: application/xml; charset=utf-8`, `x-content-type-options: nosniff`, `content-disposition: attachment; filename="recipescam-<id>.recipe"` |
+
+Nội dung file là **đúng định dạng `.recipe` mà app đã xuất/nhập**: XML bọc
+payload xor16-v1, sinh tại `docker/backend/src/recipeFile.ts` (bản sao của
+`shared/utils/recipeShare.ts`). Salt mới mỗi lần tải — hai lần quét cùng một mã
+ra hai file khác byte nhưng cùng recipe. `test/security.mjs` khoá hình dạng
+envelope này (+12 check, backend 134/134).
+
+Vì vậy **mã QR chỉ chứa URL**, không chứa recipe. Vài chục byte, không phải
+vài KB base64 — camera chỉ cần bắt được một liên kết ngắn.
+
+Nhãn i18n liên quan (đã có trên web): `adm.pickQr` = `QR card` / `Thẻ QR`,
+`adm.noPreset` = `no look to hand out` / `không có look để chia sẻ`.
+
+---
+
+## 2. Vì sao KHÔNG dùng vision-camera để quét
+
+Đường thẳng nhất là quét QR bằng chính session camera của viewfinder. Không
+được: **vision-camera v5 trên Android không có object output.**
+
+```text
+modules/.../HybridCameraFactory.kt:112
+createObjectOutput → throw "CameraObjectOutput is not available on Android!"
+```
+
+`useObjectOutput` là API iOS-only. Barcode/QR trên Android phải đi đường khác,
+nên app dùng **`expo-camera`** — nó bọc chính barcode scanner của Android.
+
+```bash
+npx expo install expo-camera     # ~57.0.5
+```
+
+`app.json` thêm plugin trước `expo-sharing`:
+
+```json
+["expo-camera", { "cameraPermission": "Allow RecipesCam to scan a recipe QR code." }]
+```
+
+**Hệ quả bắt buộc: phải build lại dev client / APK.** `expo-camera` là native
+module mới; bundle JS cũ không có nó.
+
+App giờ có **hai thư viện camera**. CameraX không cho hai client cùng giữ một
+ống kính, nên khi sheet quét mở thì viewfinder phải nhả camera ra — xem mục 4.
+
+### 2.1 HTTP thuần (cleartext) — chỉ chạy ở debug
+
+Route preset hiện phục vụ qua **HTTP thuần** (`http://<host>:8090/...`). Android
+9+ chặn cleartext mặc định, nhưng manifest debug đã bật sẵn:
+
+```xml
+<!-- android/app/src/debug/AndroidManifest.xml -->
+<application android:usesCleartextTraffic="true" ... />
+```
+
+`android/app/src/main/AndroidManifest.xml` **không** có dòng đó. Nghĩa là:
+
+| Bản build | Quét thẻ QR |
+| --- | --- |
+| dev client / APK debug | chạy — cleartext được bật |
+| APK release | `fetch` bị chặn, `Import failed` |
+
+Nếu bản release cũng phải quét được thì **một trong hai**: phục vụ landing qua
+HTTPS (tốt hơn — khi đó không phải đụng gì), hoặc bật cleartext cho release bằng
+`expo-build-properties` (`android.usesCleartextTraffic: true`) — plugin này chưa
+cài, nên chỉ thêm khi thật sự cần.
+
+---
+
+## 3. `src/components/QrScanModal.tsx` (mới)
+
+Sheet quét: `Modal` + `CameraView` (`facing="back"`, `barcodeScannerSettings` chỉ
+`['qr']`), xin quyền bằng `useCameraPermissions()` khi mở, và một **chốt
+`takenRef`** — scanner báo mã ở mọi frame còn giữ mã, chốt chặn lần đầu để
+không import mười lần. Mở lại sheet thì chốt reset.
+
+Props: `{ visible, onCancel, onScanned }`. Khung ngắm màu hổ phách + dòng
+`POINT AT A RECIPE QR` + nút X đóng. Khung ngắm `pointerEvents="none"` để cú
+chạm rơi xuống camera bên dưới.
+
+---
+
+## 4. Nối vào App
+
+| File | Thay đổi |
+| --- | --- |
+| `App.tsx` | state `scanVisible`; `storeImportedRecipe(xml)` tách ra dùng chung với IMPORT; `handleScanRecipe(value)`; truyền `onScanRecipe` xuống panel; render `<QrScanModal>`; truyền `paused={scanVisible}` xuống viewfinder |
+| `src/components/AdjustmentPanel.tsx` | prop `onScanRecipe: () => void`; chip `SCAN QR` sau chip `IMPORT` trong tab `recipes` |
+| `src/components/Viewfinder.tsx` | prop `paused?: boolean` (mặc định `false`); `isActive={appActive && !ultraWideOn && !paused}`, `active={appActive && ultraWideOn && !paused}` |
+| `app.json` | plugin `expo-camera` + câu xin quyền |
+| `package.json` | `expo-camera ~57.0.5` |
+
+`handleScanRecipe` **đóng sheet trước**, rồi mới xử lý — thất bại là một hộp
+thoại, không phải một scanner còn chạy. Cổng `liteSaveBlocked` /
+`promptRecipeLimit()` đứng trước, giống đường IMPORT.
+
+Liên kết phải đúng route preset, không thì từ chối kèm lý do:
+
+```ts
+const link = /^https?:\/\/\S+\/api\/photos\/\d+\/preset\.recipe$/.exec(value.trim());
+if (!link) throw new Error('That code is not a RecipesCam recipe link.');
+const res = await fetch(link[0]);
+if (!res.ok) throw new Error(`The recipe link answered ${res.status}.`);
+await storeImportedRecipe(await res.text());
+```
+
+Nhờ vậy mã QR của wifi, link shop, link app store… đều bị chặn bằng câu
+`That code is not a RecipesCam recipe link.` chứ không im lặng nuốt.
+
+`storeImportedRecipe` chính là thân cũ của `handleImportRecipe`: dynamic-import
+`importRecipeXml` → `saveCustomRecipe` → `getAllRecipes` → `applyRecipe` →
+Haptics success → `Alert.alert('Recipe Imported', …)`. Hai đường (chọn file và
+quét mã) giờ dùng chung một chỗ lưu, nên recipe quét về nằm cùng danh sách
+custom như recipe import bằng file.
+
+---
+
+## 5. Kiểm thử
+
+- `node --stack-size=12000 node_modules/typescript/bin/tsc --noEmit` → đúng 15
+  lỗi có sẵn (`Viewfinder.tsx`, `skiaImage.ts`), **không lỗi nào ở
+  `App.tsx` / `QrScanModal.tsx` / `AdjustmentPanel.tsx`.
+  (`npx tsc --noEmit` trên cây Android crash `RangeError: Maximum call stack size exceeded` — lỗi có sẵn, phải truyền `--stack-size`.)
+- Phía web: `preset-roundtrip.cjs` 11/0 — file backend sinh ra import được bằng
+  chính parser của app (tiếng Việt có dấu, `classic-vivid`, adjustments,
+  `frameId`, `useGeotag`), và envelope lạ bị từ chối.
+- **Còn phải đo trên máy thật** sau khi build lại: quét thẻ QR trên landing →
+  recipe xuất hiện trong PRESETS và look đổi; quét một mã không phải link
+  RecipesCam → hộp thoại từ chối; mở sheet trong khi viewfinder đang chạy →
+  không có lỗi CameraX "camera already in use".

App.tsx

@@ -16,6 +16,7 @@ import ToolRail, { TabId } from './src/components/ToolRail';
 import SettingsModal from './src/components/SettingsModal';
 import PhotoViewerModal from './src/components/PhotoViewerModal';
 import LibraryPickerModal from './src/components/LibraryPickerModal';
+import QrScanModal from './src/components/QrScanModal';
 import ProModal from './src/components/ProModal';
 
 import { Recipe, ColorAdjustments, CustomWatermark, GpsWatermark, FrameId, GPSInfo, AspectRatio, MeterMode, PhotoEntry, ShutterSound, FlashMode, StartupMode, CropRatio, CropRect, CROP_W_H, DEFAULT_CROP_RECT } from './src/types';
@@ -277,6 +278,9 @@ export default function App() {
   const [viewerIndex, setViewerIndex] = useState<number | null>(null);
   // In-app library picker (grid -> full-screen preview -> USE/CANCEL).
   const [libraryPickerVisible, setLibraryPickerVisible] = useState(false);
+  // QR sheet: reads a recipe link off a screen, so the viewfinder camera behind
+  // it is paused while it is up (one lens, two camera libraries).
+  const [scanVisible, setScanVisible] = useState(false);
   // Gear sheet (sound / ratio / metering mode). Camera captures never auto-open
   // the viewer anymore — the thumbnail button does.
   const [settingsVisible, setSettingsVisible] = useState(false);
@@ -1028,6 +1032,18 @@ export default function App() {
     }
   };
 
+  // PRESETS -> IMPORT / SCAN QR: a `.recipe` file that arrived from elsewhere —
+  // picked off storage or fetched from a scanned link — becomes a normal custom
+  // recipe, and the look on screen switches to it.
+  const storeImportedRecipe = async (xml: string) => {
+    const { importRecipeXml } = await import('./src/utils/recipeShare');
+    const created = await saveCustomRecipe(importRecipeXml(xml));
+    setRecipes(await getAllRecipes());
+    applyRecipe(created);
+    Haptics.notificationAsync(Haptics.NotificationFeedbackType.Success);
+    Alert.alert('Recipe Imported', `"${created.name}" has been added.`);
+  };
+
   // PRESETS -> IMPORT: a recipe file shared from another phone, picked from
   // storage, decoded and stored as a normal custom recipe.
   const handleImportRecipe = async () => {
@@ -1038,13 +1054,30 @@ export default function App() {
     try {
       const picked = await DocumentPicker.getDocumentAsync({ type: '*/*', copyToCacheDirectory: true });
       if (picked.canceled) return;
-      const xml = await FileSystem.readAsStringAsync(picked.assets[0].uri);
+      await storeImportedRecipe(await FileSystem.readAsStringAsync(picked.assets[0].uri));
-      const { importRecipeXml } = await import('./src/utils/recipeShare');
+    } catch (e) {
-      const created = await saveCustomRecipe(importRecipeXml(xml));
+      Alert.alert('Import failed', e instanceof Error ? e.message : String(e));
-      setRecipes(await getAllRecipes());
+    }
-      applyRecipe(created);
+  };
-      Haptics.notificationAsync(Haptics.NotificationFeedbackType.Success);
+
-      Alert.alert('Recipe Imported', `"${created.name}" has been added.`);
+  // PRESETS -> SCAN QR: the landing page's recipe card carries a link to a
+  // photo's own `.recipe` file, so a scan is the same import with the file
+  // fetched instead of picked. The code holds a URL, never the recipe, so
+  // anything that is not the preset route — a shop link, a wifi code — is
+  // refused with the reason. The sheet closes either way; a failure is a
+  // dialog, not a scanner left running.
+  const handleScanRecipe = async (value: string) => {
+    setScanVisible(false);
+    if (liteSaveBlocked) {
+      promptRecipeLimit();
+      return;
+    }
+    try {
+      const link = /^https?:\/\/\S+\/api\/photos\/\d+\/preset\.recipe$/.exec(value.trim());
+      if (!link) throw new Error('That code is not a RecipesCam recipe link.');
+      const res = await fetch(link[0]);
+      if (!res.ok) throw new Error(`The recipe link answered ${res.status}.`);
+      await storeImportedRecipe(await res.text());
     } catch (e) {
       Alert.alert('Import failed', e instanceof Error ? e.message : String(e));
     }
@@ -1821,6 +1854,9 @@ export default function App() {
           photoStraighten={shown.photoStraighten}
           cameraPermissionGranted={cameraPermissionGranted}
           onRequestCameraPermission={requestCameraPermission}
+          // One lens, two camera libraries: while the QR sheet is up its own
+          // scanner owns the camera and this session has to let go.
+          paused={scanVisible}
           photoOutput={photoOutput}
           rawOutput={rawPhotoOutput}
           rawEnabled={rawEnabled}
@@ -1939,6 +1975,7 @@ export default function App() {
               onToggleGeotag={handleToggleGeotag}
               onSaveRecipe={handleSaveRecipe}
               onImportRecipe={handleImportRecipe}
+              onScanRecipe={() => setScanVisible(true)}
               recipeLimitReached={liteSaveBlocked}
               onRecipeLimit={promptRecipeLimit}
               onDeleteRecipe={handleDeleteRecipe}
@@ -1965,6 +2002,14 @@ export default function App() {
           onSelect={handleLibraryPicked}
         />
 
+        {/* QR sheet: reads a recipe link off another screen (the landing page's
+            card) and imports the file it points at. */}
+        <QrScanModal
+          visible={scanVisible}
+          onCancel={() => setScanVisible(false)}
+          onScanned={handleScanRecipe}
+        />
+
         <CameraControls
           lastPhotoUri={lastPhotoUri}
           onCapture={handleCapture}

app.json

@@ -49,6 +49,12 @@
      "isAccessMediaLocationEnabled": true
     }
    ],
+   [
+    "expo-camera",
+    {
+     "cameraPermission": "Allow RecipesCam to scan a recipe QR code."
+    }
+   ],
    "expo-sharing"
   ],
   "extra": {

package-lock.json

@@ -14,6 +14,7 @@
         "babel-preset-expo": "~57.0.0",
         "expo": "~57.0.7",
         "expo-asset": "~57.0.5",
+        "expo-camera": "~57.0.5",
         "expo-dev-client": "~57.0.6",
         "expo-document-picker": "~57.0.2",
         "expo-file-system": "~57.0.1",
@@ -2042,6 +2043,12 @@
       "integrity": "sha512-hhyNJ+nbR6ZR7pToHvllEFun9TL0sbL+tk/ON75lo+Xas054uez98qRbsuNt7MBCyZKK4+8Yli/OAGZhmfBZ/g==",
       "license": "MIT"
     },
+    "node_modules/@types/emscripten": {
+      "version": "1.41.6",
+      "resolved": "https://registry.npmjs.org/@types/emscripten/-/emscripten-1.41.6.tgz",
+      "integrity": "sha512-uN+9i8bFT5CUcZfyIEYDrSueACEyKGbUs5kC/72DGlZZoinh84sJfVV0i8UOJD1asdzkvLPBRrKs41kZ8MdEXg==",
+      "license": "MIT"
+    },
     "node_modules/@types/istanbul-lib-coverage": {
       "version": "2.0.6",
       "resolved": "https://registry.npmjs.org/@types/istanbul-lib-coverage/-/istanbul-lib-coverage-2.0.6.tgz",
@@ -2448,6 +2455,15 @@
         "node": "18 || 20 || >=22"
       }
     },
+    "node_modules/barcode-detector": {
+      "version": "3.2.2",
+      "resolved": "https://registry.npmjs.org/barcode-detector/-/barcode-detector-3.2.2.tgz",
+      "integrity": "sha512-/4QOrrNrCRmDSBWiiP4aC72dnkuXUEdcFRidHgbPRXUpy82XcCMvJssI6fEs6JT42LS7DvBVZO70qasJbYKyrA==",
+      "license": "MIT",
+      "dependencies": {
+        "zxing-wasm": "3.1.3"
+      }
+    },
     "node_modules/base64-js": {
       "version": "1.5.1",
       "resolved": "https://registry.npmjs.org/base64-js/-/base64-js-1.5.1.tgz",
@@ -3380,6 +3396,26 @@
         "react-native": "*"
       }
     },
+    "node_modules/expo-camera": {
+      "version": "57.0.5",
+      "resolved": "https://registry.npmjs.org/expo-camera/-/expo-camera-57.0.5.tgz",
+      "integrity": "sha512-0JaUXfDWMytmqm4pVKesZfLTSjAumfS2UGhnc1M4tqJ0qATCS0jxc7KjaoyKEzWJY+FEc8GlPCAGprS/7tNWZQ==",
+      "license": "MIT",
+      "dependencies": {
+        "barcode-detector": "^3.0.0"
+      },
+      "peerDependencies": {
+        "expo": "*",
+        "react": "*",
+        "react-native": "*",
+        "react-native-web": "*"
+      },
+      "peerDependenciesMeta": {
+        "react-native-web": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/expo-constants": {
       "version": "57.0.6",
       "resolved": "https://registry.npmjs.org/expo-constants/-/expo-constants-57.0.6.tgz",
@@ -7420,6 +7456,18 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/tagged-tag": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/tagged-tag/-/tagged-tag-1.0.0.tgz",
+      "integrity": "sha512-yEFYrVhod+hdNyx7g5Bnkkb0G6si8HJurOoOEgC8B/O0uXLHlaey/65KRv6cuWBNhBgHKAROVpc7QyYqE5gFng==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=20"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
+    },
     "node_modules/tailwindcss": {
       "version": "3.4.19",
       "resolved": "https://registry.npmjs.org/tailwindcss/-/tailwindcss-3.4.19.tgz",
@@ -7976,6 +8024,34 @@
       "funding": {
         "url": "https://github.com/sponsors/colinhacks"
       }
+    },
+    "node_modules/zxing-wasm": {
+      "version": "3.1.3",
+      "resolved": "https://registry.npmjs.org/zxing-wasm/-/zxing-wasm-3.1.3.tgz",
+      "integrity": "sha512-3lC9BJk4fR5ZJxcGjb0hVnDFOW7KpLXHIebiBmVd4FDRQZVeObztoTKxRUPxlWwSgxrMRONK0u50hBD1aTYEKg==",
+      "license": "MIT",
+      "dependencies": {
+        "@types/emscripten": "^1.41.5",
+        "type-fest": "^5.8.0"
+      },
+      "peerDependencies": {
+        "@types/emscripten": ">=1.39.6"
+      }
+    },
+    "node_modules/zxing-wasm/node_modules/type-fest": {
+      "version": "5.10.0",
+      "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-5.10.0.tgz",
+      "integrity": "sha512-NoSdpq/WEiAg5sjmBkmV/hfxv6HJH4NqPNrqjtSO5CwRmpsDfaf4begxW34KdJykH/l1yHtwBWQkCRdoXO8mPA==",
+      "license": "(MIT OR CC0-1.0)",
+      "dependencies": {
+        "tagged-tag": "^1.0.0"
+      },
+      "engines": {
+        "node": ">=20"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
     }
   }
 }

package.json

@@ -9,6 +9,7 @@
     "babel-preset-expo": "~57.0.0",
     "expo": "~57.0.7",
     "expo-asset": "~57.0.5",
+    "expo-camera": "~57.0.5",
     "expo-dev-client": "~57.0.6",
     "expo-document-picker": "~57.0.2",
     "expo-file-system": "~57.0.1",

src/components/AdjustmentPanel.tsx

@@ -116,6 +116,9 @@ interface AdjustmentPanelProps {
   // IMPORT: pick a recipe file shared from another phone and store it as a
   // normal custom recipe.
   onImportRecipe: () => void;
+  // SCAN QR: read the recipe link on the landing page's card with the camera
+  // and import the file it points at — same store, no file picker.
+  onScanRecipe: () => void;
   // LITE: this many of its own recipes exist, so the next one is the paid
   // step. The strip's trailing + chip reads it, the save paths gate on it.
   recipeLimitReached: boolean;
@@ -258,6 +261,7 @@ export default function AdjustmentPanel({
   onToggleWallLandscape,
   onToggleGeotag,
   onImportRecipe,
+  onScanRecipe,
   recipeLimitReached,
   onRecipeLimit,
   onDeleteRecipe,
@@ -839,6 +843,12 @@ export default function AdjustmentPanel({
               active: false,
               onPress: onImportRecipe,
             },
+            {
+              key: 'scan',
+              label: 'SCAN QR',
+              active: false,
+              onPress: onScanRecipe,
+            },
           ],
           8
         );

src/components/QrScanModal.tsx

@@ -0,0 +1,82 @@
+import React, { useCallback, useEffect, useRef } from 'react';
+import { Modal, Text, TouchableOpacity, View } from 'react-native';
+import { CameraView, useCameraPermissions, type BarcodeScanningResult } from 'expo-camera';
+import { X } from 'lucide-react-native';
+
+// SCAN QR: reads the code on the landing page's recipe card and hands the
+// decoded string to App, which fetches the `.recipe` file it points at. The
+// code carries a link, never the recipe itself, so the camera only ever has to
+// frame a few dozen bytes.
+//
+// This is the app's second camera on purpose: `expo-camera` (Android's own
+// barcode scanner) instead of the vision-camera session the viewfinder uses,
+// because vision-camera v5's object output is iOS-only — Android's
+// `createObjectOutput` throws "CameraObjectOutput is not available on
+// Android!". App keeps the two from fighting over the lens by pausing the
+// viewfinder while this sheet is up (`Viewfinder paused`).
+interface QrScanModalProps {
+  visible: boolean;
+  onCancel: () => void;
+  onScanned: (value: string) => void;
+}
+
+export default function QrScanModal({ visible, onCancel, onScanned }: QrScanModalProps) {
+  const [permission, requestPermission] = useCameraPermissions();
+  // One code per opening: the scanner reports every frame that holds a code, so
+  // the first one trips this latch and the rest are dropped until the sheet is
+  // opened again.
+  const takenRef = useRef(false);
+
+  useEffect(() => {
+    if (!visible) return;
+    takenRef.current = false;
+    if (permission && !permission.granted && permission.canAskAgain) requestPermission();
+  }, [visible, permission, requestPermission]);
+
+  const handleScanned = useCallback(
+    (result: BarcodeScanningResult) => {
+      if (takenRef.current) return;
+      takenRef.current = true;
+      onScanned(result.data);
+    },
+    [onScanned],
+  );
+
+  return (
+    <Modal visible={visible} animationType="fade" statusBarTranslucent onRequestClose={onCancel}>
+      <View className="flex-1 bg-black">
+        {permission?.granted ? (
+          <CameraView
+            style={{ flex: 1 }}
+            facing="back"
+            active={visible}
+            barcodeScannerSettings={{ barcodeTypes: ['qr'] }}
+            onBarcodeScanned={handleScanned}
+          />
+        ) : (
+          <View className="flex-1 items-center justify-center p-8">
+            <Text className="text-zinc-400 font-mono text-xs text-center leading-5">
+              CAMERA PERMISSION IS NEEDED TO SCAN A RECIPE CODE
+            </Text>
+          </View>
+        )}
+
+        {/* Reticle. Pointer-transparent so the touch goes to the camera. */}
+        <View className="absolute inset-0 items-center justify-center" pointerEvents="none">
+          <View className="w-64 h-64 rounded-2xl border-2 border-amber-500/80" />
+          <Text className="mt-6 text-amber-500 font-mono text-xs tracking-widest">
+            POINT AT A RECIPE QR
+          </Text>
+        </View>
+
+        <TouchableOpacity
+          onPress={onCancel}
+          accessibilityLabel="Close the QR scanner"
+          className="absolute top-12 right-6 w-10 h-10 rounded-full bg-black/60 border border-zinc-700 items-center justify-center"
+        >
+          <X color="#ffffff" size={20} />
+        </TouchableOpacity>
+      </View>
+    </Modal>
+  );
+}

src/components/Viewfinder.tsx

@@ -65,6 +65,10 @@ interface ViewfinderProps {
   // a nonce so the panel puts the caret back in its input).
   onWmEdit?: () => void;
   cameraPermissionGranted: boolean;
+  // Another camera session wants the lens (the QR scanner's own sheet): the
+  // live session stops until it is up, exactly as it does for the app going
+  // to the background — two CameraX clients cannot hold one camera.
+  paused?: boolean;
   onRequestCameraPermission: () => void;
   photoOutput: CameraPhotoOutput;
   // Composition ratio (FULL / 4:3 / 3:2 upright) driving the viewfinder band
@@ -303,6 +307,7 @@ const Viewfinder = forwardRef<ViewfinderHandle, ViewfinderProps>(function Viewfi
     availableHeight,
     topInset,
     cameraPermissionGranted,
+    paused = false,
     onRequestCameraPermission,
     photoOutput,
     aspectRatio,
@@ -2871,7 +2876,7 @@ const Viewfinder = forwardRef<ViewfinderHandle, ViewfinderProps>(function Viewfi
           ref={skiaCameraRef}
           style={StyleSheet.absoluteFill}
           device={device}
-          isActive={appActive && !ultraWideOn}
+          isActive={appActive && !ultraWideOn && !paused}
           outputs={cameraOutputs}
           pixelFormat="yuv"
           targetResolution={frameTarget}
@@ -2886,7 +2891,7 @@ const Viewfinder = forwardRef<ViewfinderHandle, ViewfinderProps>(function Viewfi
             turning one on means turning the other off, never both at once. */}
         <UltraWidePreview
           style={StyleSheet.absoluteFill}
-          active={appActive && ultraWideOn}
+          active={appActive && ultraWideOn && !paused}
           cover={uwCover}
         />
         {/* Gesture layer: tap = AE/AF lock; vertical drag on the image adjusts