diff --git a/app/app.json b/app/app.json
index d7f9dba..4c83119 100644
--- a/app/app.json
+++ b/app/app.json
@@ -3,14 +3,14 @@
     "name": "BigBrainParking",
     "slug": "bigbrainparking",
     "scheme": "bigbrainparking",
-    "version": "0.2.5",
+    "version": "0.2.6",
     "orientation": "portrait",
     "userInterfaceStyle": "automatic",
     "newArchEnabled": true,
     "icon": "./assets/icon.png",
     "android": {
       "package": "top.mowden.bigbrainparking",
-      "versionCode": 15,
+      "versionCode": 16,
       "edgeToEdgeEnabled": true,
       "adaptiveIcon": {
         "foregroundImage": "./assets/adaptive-icon.png",
diff --git a/app/src/screens/ScanScreen.tsx b/app/src/screens/ScanScreen.tsx
index 1901a4e..25a602e 100644
--- a/app/src/screens/ScanScreen.tsx
+++ b/app/src/screens/ScanScreen.tsx
@@ -66,23 +66,41 @@ export function ScanScreen() {
   const lookupCode = useCallback(
     async (code: string) => {
       setBusy(true);
-      try {
-        let res = await ps.getMetersByScannerCode(code);
-        let zone = res.Zones?.[0];
-        if (!zone) {
-          res = await ps.getMetersByZoneName(code);
+      // A scanned/typed code can resolve by terminal serial, scanner code, or
+      // zone name. Unmatched lookups return an error envelope (which the client
+      // throws), and ZoneName is case-sensitive server-side — the official app
+      // queries it lowercased. So try each strategy independently and don't let
+      // one failing attempt abort the others.
+      // ScannerCode is what kiosk QRs encode and what the official app honors;
+      // zone name (case-sensitive) and terminal serial are extra fallbacks.
+      const attempts = [
+        () => ps.getMetersByScannerCode(code),
+        () => ps.getMetersByZoneName(code),
+        () => ps.getMetersByZoneName(code.toLowerCase()),
+        () => ps.getMetersBySerialNumber(code),
+      ];
+      let zone:
+        | NonNullable<Awaited<ReturnType<typeof ps.getMetersByZoneName>>['Zones']>[number]
+        | undefined;
+      let anyResponded = false;
+      for (const attempt of attempts) {
+        try {
+          const res = await attempt();
+          anyResponded = true;
           zone = res.Zones?.[0];
+          if (zone) break;
+        } catch {
+          // strategy didn't apply (e.g. error envelope) — try the next one
         }
-        if (zone) {
-          setManualOpen(false);
-          navigation.navigate('MeterDetail', { zone });
-        } else {
-          Alert.alert('Not found', `No meter matches "${code}".`);
-        }
-      } catch (e: any) {
-        Alert.alert('Lookup failed', e?.serverMessage ?? e?.message ?? 'error');
-      } finally {
-        setBusy(false);
+      }
+      setBusy(false);
+      if (zone) {
+        setManualOpen(false);
+        navigation.navigate('MeterDetail', { zone });
+      } else if (anyResponded) {
+        Alert.alert('Not found', `No meter matches "${code}".`);
+      } else {
+        Alert.alert('Lookup failed', 'Could not reach ParkSmarter. Check your connection.');
       }
     },
     [navigation],
diff --git a/docs/zone-qr/DL-sandpoint.png b/docs/zone-qr/DL-sandpoint.png
new file mode 100644
index 0000000..74afee5
Binary files /dev/null and b/docs/zone-qr/DL-sandpoint.png differ
diff --git a/docs/zone-qr/README.md b/docs/zone-qr/README.md
new file mode 100644
index 0000000..aed65dc
--- /dev/null
+++ b/docs/zone-qr/README.md
@@ -0,0 +1,36 @@
+# Zone QR codes
+
+A parking-zone QR code just encodes the zone's **`ScannerCode`** as plain text.
+BigBrainParking's scanner (and the official ParkSmarter app) resolve that code to
+the zone. No URL, no wrapper — the raw scanner code is enough.
+
+## Make one
+
+```bash
+qrencode -o my-zone.png -s 14 -m 4 "<ScannerCode>"
+```
+
+`<ScannerCode>` is the zone's `ScannerCode` field (visible on the meter detail
+screen, or in a `/api/Meter` response). For the DL zone in Sandpoint it's `DL`:
+
+```bash
+qrencode -o DL-sandpoint.png -s 14 -m 4 "DL"
+```
+
+![DL zone, Sandpoint](DL-sandpoint.png)
+
+## Which field to encode
+
+Use **`ScannerCode`** — it's what physical kiosk QR stickers encode and the only
+field the official ParkSmarter app accepts when scanning.
+
+- `ScannerCode` — ✅ works in BigBrainParking **and** the official app.
+- `ZoneName` (e.g. `dl`) — works as a fallback in BigBrainParking (case-sensitive
+  server-side; the app tries the lowercased form too).
+- `TerminalSerNo` (e.g. `30004246`) — uniquely identifies the terminal and works
+  in BigBrainParking, but the **official app rejects a bare serial** ("not
+  recognized as a ParkSmarter zone"), so don't use it for cross-app QR codes.
+
+When BigBrainParking scans a code it tries, in order: `ScannerCode → ZoneName →
+zonename(lowercased) → TerminalSerNo`, each independently, so any of these
+resolve.