chore: update version number to 0.1.29

App.tsx

@@ -41,6 +41,9 @@ import { useLocaleStore } from './src/stores/locale-store';
 import { useNetworkStore } from './src/stores/network-store';
 import { useUpdatesStore } from './src/stores/updates-store';
 import { UpdateBanner } from './src/components/UpdateBanner';
+import { OfflineCacheBanner } from './src/components/OfflineCacheBanner';
+import { useOfflineCacheStore } from './src/stores/offline-cache-store';
+import { runOfflineSync } from './src/lib/offline-sync';
 import { spacing, typography, type ThemePalette } from './src/theme/tokens';
 import { useColors } from './src/theme/colors';
 
@@ -48,8 +51,21 @@ const Stack = createNativeStackNavigator<RootStackParamList>();
 const Tab = createBottomTabNavigator<MainTabsParamList>();
 const navigationRef = createNavigationContainerRef<RootStackParamList>();
 
-function navigateToNotificationTap(payload: NotificationTapPayload): void {
+async function navigateToNotificationTap(payload: NotificationTapPayload): Promise<void> {
   if (!navigationRef.isReady()) return;
+
+  // The notification carries the account it was generated for. If the user
+  // has since switched to a different account (or had a different one active
+  // when the notification arrived), opening EmailThread under the active
+  // account would fetch the email from the wrong server and fail.
+  const auth = useAuthStore.getState();
+  if (payload.accountId && payload.accountId !== auth.activeAccountId) {
+    const account = useAccountStore.getState().getAccountById(payload.accountId);
+    if (!account) return; // account was logged out — nothing safe to open.
+    await auth.switchAccount(payload.accountId);
+    if (useAuthStore.getState().activeAccountId !== payload.accountId) return;
+  }
+
   navigationRef.navigate('EmailThread', {
     emailId: payload.emailId,
     threadId: payload.threadId,
@@ -76,6 +92,7 @@ function MainTabsNavigator({ navigation }: NativeStackScreenProps<RootStackParam
   return (
     <View style={{ flex: 1, backgroundColor: c.background }}>
       <UpdateBanner />
+      <OfflineCacheBanner />
     <Tab.Navigator
       screenOptions={{
         headerShown: false,
@@ -218,6 +235,24 @@ export default function App() {
     return () => { cancelled = true; };
   }, []);
 
+  // Offline mail cache: hydrate the cache index on launch, and kick off a
+  // background sync once we have a live JMAP session and the user has the
+  // feature enabled. Re-runs whenever the user changes the days window.
+  const offlineCacheEnabled = useSettingsStore((s) => s.offlineCacheEnabled);
+  const offlineCacheDays = useSettingsStore((s) => s.offlineCacheDays);
+  const haveLiveSession = useAuthStore((s) => s.session != null);
+  React.useEffect(() => {
+    void useOfflineCacheStore.getState().hydrate();
+  }, []);
+  React.useEffect(() => {
+    if (!offlineCacheEnabled || !haveLiveSession) return;
+    // Slight delay so cold start doesn't compete with the inbox load.
+    const t = setTimeout(() => {
+      void runOfflineSync({ days: offlineCacheDays });
+    }, 2000);
+    return () => clearTimeout(t);
+  }, [offlineCacheEnabled, offlineCacheDays, haveLiveSession]);
+
   // Listen for FCM messages so the app can refresh state even when woken
   // from the background - the FirebaseMessagingService also posts the system
   // notification so the user sees it regardless of RN runtime state.
@@ -239,11 +274,11 @@ export default function App() {
     void (async () => {
       const initial = await getInitialNotificationTap();
       if (cancelled || !initial) return;
-      navigateToNotificationTap(initial);
+      await navigateToNotificationTap(initial);
     })();
 
     const unsubscribe = addNotificationTapListener((payload) => {
-      navigateToNotificationTap(payload);
+      void navigateToNotificationTap(payload);
     });
 
     return () => {

VERSION

@@ -1 +1 @@
-0.1.21
+0.1.29

android/app/src/main/AndroidManifest.xml

@@ -2,11 +2,9 @@
   <uses-permission android:name="android.permission.INTERNET"/>
   <uses-permission android:name="android.permission.POST_NOTIFICATIONS"/>
   <uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES"/>
-  <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
-  <uses-permission android:name="android.permission.RECORD_AUDIO"/>
-  <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
+  <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" android:maxSdkVersion="32"/>
+  <uses-permission android:name="android.permission.READ_MEDIA_IMAGES"/>
   <uses-permission android:name="android.permission.VIBRATE"/>
-  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
   <queries>
     <intent>
       <action android:name="android.intent.action.VIEW"/>

android/app/src/main/java/com/anonymous/bulwarkmobile/BulwarkClientCertModule.kt

@@ -11,16 +11,17 @@ import com.facebook.react.bridge.ReactApplicationContext
 import com.facebook.react.bridge.ReactContextBaseJavaModule
 import com.facebook.react.bridge.ReactMethod
 import com.facebook.react.bridge.ReadableMap
-import okhttp3.MediaType.Companion.toMediaTypeOrNull
-import okhttp3.OkHttpClient
-import okhttp3.Request
-import okhttp3.RequestBody.Companion.toRequestBody
+import java.io.ByteArrayOutputStream
+import java.net.HttpURLConnection
 import java.net.Socket
+import java.net.URL
 import java.security.Principal
 import java.security.PrivateKey
 import java.security.cert.X509Certificate
-import java.util.concurrent.TimeUnit
+import javax.net.ssl.HttpsURLConnection
 import javax.net.ssl.SSLContext
+import javax.net.ssl.SSLEngine
+import javax.net.ssl.SSLSocketFactory
 import javax.net.ssl.TrustManager
 import javax.net.ssl.TrustManagerFactory
 import javax.net.ssl.X509ExtendedKeyManager
@@ -36,10 +37,11 @@ import kotlin.concurrent.thread
  *      pick a cert installed in Android's system credential store. The
  *      selected alias is persisted in SharedPreferences so the choice
  *      survives app restarts.
- *   2. `fetchSecure` — a fetch shim built on OkHttp that injects the picked
- *      cert into the TLS handshake. JS-side `fetch` cannot present client
- *      certs because RN's bundled OkHttpClient doesn't expose its KeyManager
- *      hook to userland; this method is the workaround.
+ *   2. `fetchSecure` — a fetch shim built on `HttpsURLConnection` that
+ *      injects the picked cert into the TLS handshake. JS-side `fetch`
+ *      can't present a client cert because RN's bundled OkHttp client
+ *      doesn't expose its KeyManager hook to userland; this method is
+ *      the workaround.
  */
 class BulwarkClientCertModule(reactContext: ReactApplicationContext)
     : ReactContextBaseJavaModule(reactContext) {
@@ -48,8 +50,8 @@ class BulwarkClientCertModule(reactContext: ReactApplicationContext)
         reactContext.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
 
     @Volatile private var cachedAlias: String? = prefs.getString(PREF_ALIAS, null)
-    @Volatile private var cachedClient: OkHttpClient? = null
-    @Volatile private var cachedClientForAlias: String? = null
+    @Volatile private var cachedFactory: SSLSocketFactory? = null
+    @Volatile private var cachedFactoryForAlias: String? = null
 
     override fun getName(): String = MODULE_NAME
 
@@ -64,32 +66,34 @@ class BulwarkClientCertModule(reactContext: ReactApplicationContext)
     fun clearAlias(promise: Promise) {
         prefs.edit().remove(PREF_ALIAS).apply()
         cachedAlias = null
-        invalidateClient()
+        invalidateFactory()
         promise.resolve(null)
     }
 
     /**
      * Show the system "Choose a certificate" picker. Resolves with the
      * selected alias, or `null` when the user dismisses the picker.
-     *
-     * @param host  optional host hint shown by the picker
      */
     @ReactMethod
     fun pickAlias(host: String?, promise: Promise) {
-        val activity = currentActivity
+        // ReactContextBaseJavaModule no longer exposes a Kotlin synthetic
+        // `currentActivity` property in RN 0.80+ (compiles as an unresolved
+        // reference). The explicit Java-style getter on the application
+        // context is the supported call site.
+        val activity: android.app.Activity? = reactApplicationContext.getCurrentActivity()
         if (activity == null) {
             promise.reject("no_activity", "No current activity to host the cert picker")
             return
         }
         val callback = KeyChainAliasCallback { alias ->
-            // Callback runs off the main thread. We persist + resolve directly.
+            // Callback runs off the main thread; persist + resolve directly.
             if (alias.isNullOrBlank()) {
                 promise.resolve(null)
                 return@KeyChainAliasCallback
             }
             prefs.edit().putString(PREF_ALIAS, alias).apply()
             cachedAlias = alias
-            invalidateClient()
+            invalidateFactory()
             promise.resolve(alias)
         }
         try {
@@ -125,65 +129,70 @@ class BulwarkClientCertModule(reactContext: ReactApplicationContext)
             promise.reject("bad_args", "url is required")
             return
         }
-        val method = request.getString("method") ?: "GET"
-        val timeoutMs = if (request.hasKey("timeoutMs")) request.getInt("timeoutMs").toLong() else 30_000L
+        val method = (request.getString("method") ?: "GET").uppercase()
+        val timeoutMs = if (request.hasKey("timeoutMs")) request.getInt("timeoutMs") else 30_000
         val headersMap = request.getMap("headers")
         val bodyBase64 = request.getString("bodyBase64")
-        val contentType = headersMap
-            ?.let { h ->
-                val it = h.keySetIterator()
-                var ct: String? = null
-                while (it.hasNextKey()) {
-                    val k = it.nextKey()
-                    if (k.equals("Content-Type", ignoreCase = true)) {
-                        ct = h.getString(k)
-                        break
-                    }
-                }
-                ct
-            }
+        val bodyBytes = bodyBase64?.let { Base64.decode(it, Base64.NO_WRAP) }
 
-        // Run on a worker thread so we don't block the JS thread on socket IO.
         thread(name = "BulwarkClientCert.fetch") {
             try {
-                val client = buildOrReuseClient(timeoutMs)
-                val builder = Request.Builder().url(url)
+                val conn = (URL(url).openConnection() as HttpURLConnection).apply {
+                    connectTimeout = timeoutMs
+                    readTimeout = timeoutMs
+                    requestMethod = method
+                    instanceFollowRedirects = true
+                    if (bodyBytes != null) {
+                        doOutput = true
+                        setFixedLengthStreamingMode(bodyBytes.size)
+                    }
+                }
+                if (conn is HttpsURLConnection && cachedAlias != null) {
+                    conn.sslSocketFactory = buildOrReuseSocketFactory()
+                }
                 headersMap?.let { h ->
                     val it = h.keySetIterator()
                     while (it.hasNextKey()) {
                         val k = it.nextKey()
                         val v = h.getString(k)
-                        if (v != null) builder.addHeader(k, v)
+                        if (v != null) conn.setRequestProperty(k, v)
                     }
                 }
-                val bodyBytes = bodyBase64?.let { Base64.decode(it, Base64.NO_WRAP) }
-                val body = when {
-                    bodyBytes != null -> bodyBytes.toRequestBody(contentType?.toMediaTypeOrNull())
-                    methodRequiresBody(method) -> ByteArray(0).toRequestBody(contentType?.toMediaTypeOrNull())
-                    else -> null
+                conn.connect()
+                if (bodyBytes != null) {
+                    conn.outputStream.use { out -> out.write(bodyBytes) }
                 }
-                builder.method(method.uppercase(), body)
-                client.newCall(builder.build()).execute().use { response ->
-                    val out = Arguments.createMap()
-                    out.putInt("status", response.code)
-                    out.putString("statusText", response.message)
-                    val headers = Arguments.createMap()
-                    response.headers.forEach { (name, value) ->
-                        // OkHttp can return multiple values per header; we
-                        // join with ", " which is the standard wire format
-                        // for repeated header values.
-                        if (headers.hasKey(name)) {
-                            val existing = headers.getString(name)
-                            headers.putString(name, "$existing, $value")
-                        } else {
-                            headers.putString(name, value)
-                        }
-                    }
-                    out.putMap("headers", headers)
-                    val responseBytes = response.body?.bytes() ?: ByteArray(0)
-                    out.putString("bodyBase64", Base64.encodeToString(responseBytes, Base64.NO_WRAP))
-                    promise.resolve(out)
+
+                val status = conn.responseCode
+                val statusText = conn.responseMessage ?: ""
+                val responseStream = try {
+                    conn.inputStream
+                } catch (_: Exception) {
+                    conn.errorStream
                 }
+                val responseBytes = if (responseStream != null) {
+                    val buf = ByteArrayOutputStream()
+                    responseStream.copyTo(buf)
+                    responseStream.close()
+                    buf.toByteArray()
+                } else {
+                    ByteArray(0)
+                }
+
+                val out = Arguments.createMap()
+                out.putInt("status", status)
+                out.putString("statusText", statusText)
+                val headers = Arguments.createMap()
+                // headerFields is a `Map<String?, List<String>>`; the null
+                // key is the HTTP status line, which we don't need to copy.
+                for ((name, values) in conn.headerFields) {
+                    if (name == null || values == null) continue
+                    headers.putString(name, values.joinToString(", "))
+                }
+                out.putMap("headers", headers)
+                out.putString("bodyBase64", Base64.encodeToString(responseBytes, Base64.NO_WRAP))
+                conn.disconnect()
+                promise.resolve(out)
             } catch (e: Exception) {
                 promise.reject("fetch_failed", e.message ?: e.javaClass.simpleName, e)
             }
@@ -192,49 +201,35 @@ class BulwarkClientCertModule(reactContext: ReactApplicationContext)
 
     // ── internals ───────────────────────────────────────────────
 
-    private fun invalidateClient() {
-        cachedClient = null
-        cachedClientForAlias = null
+    private fun invalidateFactory() {
+        cachedFactory = null
+        cachedFactoryForAlias = null
     }
 
-    private fun buildOrReuseClient(timeoutMs: Long): OkHttpClient {
-        val alias = cachedAlias
-        val existing = cachedClient
-        if (existing != null && cachedClientForAlias == alias) return existing
+    private fun buildOrReuseSocketFactory(): SSLSocketFactory {
+        val alias = cachedAlias ?: throw IllegalStateException("No client-cert alias selected")
+        val existing = cachedFactory
+        if (existing != null && cachedFactoryForAlias == alias) return existing
 
-        val builder = OkHttpClient.Builder()
-            .callTimeout(timeoutMs, TimeUnit.MILLISECONDS)
-            .connectTimeout(timeoutMs, TimeUnit.MILLISECONDS)
-            .readTimeout(timeoutMs, TimeUnit.MILLISECONDS)
-
-        if (alias != null) {
-            val ctx = reactApplicationContext
-            val km = KeyChainKeyManager(ctx, alias)
-            val tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm())
-            tmf.init(null as java.security.KeyStore?)
-            val trustManagers = tmf.trustManagers
-            val tm = trustManagers.firstOrNull { it is X509TrustManager } as X509TrustManager?
-                ?: throw IllegalStateException("No X509TrustManager available")
-            val sslContext = SSLContext.getInstance("TLS")
-            sslContext.init(arrayOf(km), arrayOf<TrustManager>(tm), null)
-            builder.sslSocketFactory(sslContext.socketFactory, tm)
-        }
-
-        val client = builder.build()
-        cachedClient = client
-        cachedClientForAlias = alias
-        return client
-    }
-
-    private fun methodRequiresBody(method: String): Boolean = when (method.uppercase()) {
-        "POST", "PUT", "PATCH", "DELETE" -> true
-        else -> false
+        val ctx = reactApplicationContext
+        val km = KeyChainKeyManager(ctx, alias)
+        val tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm())
+        tmf.init(null as java.security.KeyStore?)
+        val trustManagers = tmf.trustManagers
+        val tm = trustManagers.firstOrNull { it is X509TrustManager } as X509TrustManager?
+            ?: throw IllegalStateException("No X509TrustManager available")
+        val sslContext = SSLContext.getInstance("TLS")
+        sslContext.init(arrayOf(km), arrayOf<TrustManager>(tm), null)
+        val factory = sslContext.socketFactory
+        cachedFactory = factory
+        cachedFactoryForAlias = alias
+        return factory
     }
 
     /**
      * X509ExtendedKeyManager that always returns the same KeyChain alias.
      * KeyChain.getPrivateKey / getCertificateChain are blocking; we call
-     * them lazily on the OkHttp dispatcher thread, which is fine since the
+     * them lazily during the TLS handshake, which is fine since the
      * fetch already runs off-main-thread.
      */
     private class KeyChainKeyManager(
@@ -251,13 +246,13 @@ class BulwarkClientCertModule(reactContext: ReactApplicationContext)
         override fun chooseEngineClientAlias(
             keyType: Array<out String>?,
             issuers: Array<out Principal>?,
-            engine: javax.net.ssl.SSLEngine?,
+            engine: SSLEngine?,
         ): String = alias
 
         override fun getCertificateChain(alias: String?): Array<X509Certificate>? {
             return try {
                 KeyChain.getCertificateChain(context, this.alias)
-            } catch (e: Exception) {
+            } catch (_: Exception) {
                 null
             }
         }
@@ -265,7 +260,7 @@ class BulwarkClientCertModule(reactContext: ReactApplicationContext)
         override fun getPrivateKey(alias: String?): PrivateKey? {
             return try {
                 KeyChain.getPrivateKey(context, this.alias)
-            } catch (e: Exception) {
+            } catch (_: Exception) {
                 null
             }
         }

android/app/src/main/java/com/anonymous/bulwarkmobile/BulwarkFcmModule.kt

@@ -19,6 +19,7 @@ import com.facebook.react.bridge.ReadableMap
 import com.facebook.react.bridge.WritableMap
 import com.facebook.react.modules.core.DeviceEventManagerModule.RCTDeviceEventEmitter
 import com.google.firebase.messaging.FirebaseMessaging
+import java.io.ByteArrayOutputStream
 import java.net.HttpURLConnection
 import java.net.URL
 import kotlin.concurrent.thread
@@ -64,6 +65,7 @@ class BulwarkFcmModule(reactContext: ReactApplicationContext)
         val emailId = options.getString("emailId")
         val threadId = options.getString("threadId")
         val subject = options.takeIf { it.hasKey("subject") }?.getString("subject")
+        val accountId = options.takeIf { it.hasKey("accountId") }?.getString("accountId")
 
         // Bitmap fetch + draw off the bridge thread so the caller doesn't
         // block waiting for the favicon request.
@@ -72,7 +74,7 @@ class BulwarkFcmModule(reactContext: ReactApplicationContext)
                 ?: makeLetterAvatar(initials, bgColorHex)
             postNotification(
                 notificationId, title, body, largeIcon, bgColorHex,
-                emailId, threadId, subject,
+                emailId, threadId, subject, accountId,
             )
             promise.resolve(null)
         }
@@ -93,6 +95,7 @@ class BulwarkFcmModule(reactContext: ReactApplicationContext)
         emailId: String?,
         threadId: String?,
         subject: String?,
+        accountId: String?,
     ) {
         val ctx = reactApplicationContext
         val intent = Intent(ctx, MainActivity::class.java).apply {
@@ -100,6 +103,7 @@ class BulwarkFcmModule(reactContext: ReactApplicationContext)
             if (emailId != null) putExtra(NotificationTapStore.EXTRA_EMAIL_ID, emailId)
             if (threadId != null) putExtra(NotificationTapStore.EXTRA_THREAD_ID, threadId)
             if (subject != null) putExtra(NotificationTapStore.EXTRA_SUBJECT, subject)
+            if (accountId != null) putExtra(NotificationTapStore.EXTRA_ACCOUNT_ID, accountId)
         }
         val pending = PendingIntent.getActivity(
             ctx,
@@ -148,7 +152,36 @@ class BulwarkFcmModule(reactContext: ReactApplicationContext)
         conn.readTimeout = 3000
         conn.instanceFollowRedirects = true
         conn.setRequestProperty("User-Agent", "bulwark-mobile")
-        conn.inputStream.use { BitmapFactory.decodeStream(it) }
+        // Cap the response to MAX_FAVICON_BYTES so a hostile / misconfigured
+        // server can't OOM the headless task with a multi-megabyte image.
+        // We also sample down to ~256x256 since it'll only render at 192px.
+        val stream = conn.inputStream
+        val bytes = stream.use { input ->
+            val limit = MAX_FAVICON_BYTES
+            val buf = ByteArrayOutputStream()
+            val chunk = ByteArray(8 * 1024)
+            var total = 0
+            while (true) {
+                val n = input.read(chunk)
+                if (n <= 0) break
+                total += n
+                if (total > limit) return@use null
+                buf.write(chunk, 0, n)
+            }
+            buf.toByteArray()
+        } ?: return null
+        val opts = BitmapFactory.Options().apply {
+            inJustDecodeBounds = true
+        }
+        BitmapFactory.decodeByteArray(bytes, 0, bytes.size, opts)
+        var sample = 1
+        while ((opts.outWidth / sample) > 384 || (opts.outHeight / sample) > 384) {
+            sample *= 2
+        }
+        val decodeOpts = BitmapFactory.Options().apply {
+            inSampleSize = sample
+        }
+        BitmapFactory.decodeByteArray(bytes, 0, bytes.size, decodeOpts)
     } catch (_: Exception) {
         null
     }
@@ -167,6 +200,9 @@ class BulwarkFcmModule(reactContext: ReactApplicationContext)
     fun removeListeners(count: Int) {}
 
     companion object {
+        // 1 MiB is plenty for a favicon; anything bigger is a sign of trouble.
+        private const val MAX_FAVICON_BYTES = 1 * 1024 * 1024
+
         @Volatile private var currentInstance: BulwarkFcmModule? = null
 
         fun emit(eventName: String, params: WritableMap?) {

android/app/src/main/java/com/anonymous/bulwarkmobile/NotificationTapStore.kt

@@ -17,17 +17,36 @@ object NotificationTapStore {
         return value
     }
 
+    // The activity is exported (required by the LAUNCHER intent filter), so
+    // any third-party app on the device can craft a starting intent that
+    // includes these extras. Reject anything that doesn't look like the IDs
+    // our notification builder writes — preventing other apps from
+    // navigating us to a forged email/thread.
+    private val ID_PATTERN = Regex("^[A-Za-z0-9_-]{1,128}$")
+    // accountId is `username@host` (see generateAccountId), so it needs `.`,
+    // `@`, `+` etc. — cap length and restrict charset to what that helper can
+    // emit. accountId is optional: notifications created before this field
+    // existed still navigate (using the active account as a fallback).
+    private val ACCOUNT_ID_PATTERN = Regex("^[A-Za-z0-9._+@-]{1,256}$")
+
     fun captureFromIntent(intent: Intent?): TapPayload? {
         val extras = intent?.extras ?: return null
-        val emailId = extras.getString(EXTRA_EMAIL_ID) ?: return null
-        val threadId = extras.getString(EXTRA_THREAD_ID) ?: return null
-        val subject = extras.getString(EXTRA_SUBJECT)
-        val payload = TapPayload(emailId, threadId, subject)
+        val emailId = extras.getString(EXTRA_EMAIL_ID)?.takeIf { ID_PATTERN.matches(it) }
+            ?: return null
+        val threadId = extras.getString(EXTRA_THREAD_ID)?.takeIf { ID_PATTERN.matches(it) }
+            ?: return null
+        // Subject is human-readable text and may legitimately contain anything;
+        // cap its length so a hostile launcher can't ship a 1MB string into
+        // the navigation payload.
+        val subject = extras.getString(EXTRA_SUBJECT)?.take(512)
+        val accountId = extras.getString(EXTRA_ACCOUNT_ID)?.takeIf { ACCOUNT_ID_PATTERN.matches(it) }
+        val payload = TapPayload(emailId, threadId, subject, accountId)
         pending = payload
         // Clear so a subsequent activity lifecycle event doesn't replay this.
         extras.remove(EXTRA_EMAIL_ID)
         extras.remove(EXTRA_THREAD_ID)
         extras.remove(EXTRA_SUBJECT)
+        extras.remove(EXTRA_ACCOUNT_ID)
         return payload
     }
 
@@ -35,15 +54,18 @@ object NotificationTapStore {
         val emailId: String,
         val threadId: String,
         val subject: String?,
+        val accountId: String?,
     ) {
         fun toMap(): WritableMap = Arguments.createMap().apply {
             putString("emailId", emailId)
             putString("threadId", threadId)
             if (subject != null) putString("subject", subject)
+            if (accountId != null) putString("accountId", accountId)
         }
     }
 
     const val EXTRA_EMAIL_ID = "bulwark.notification.emailId"
     const val EXTRA_THREAD_ID = "bulwark.notification.threadId"
     const val EXTRA_SUBJECT = "bulwark.notification.subject"
+    const val EXTRA_ACCOUNT_ID = "bulwark.notification.accountId"
 }

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "bulwark-mobile",
-  "version": "0.1.21",
+  "version": "0.1.29",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "bulwark-mobile",
-      "version": "0.1.21",
+      "version": "0.1.29",
       "license": "AGPL-3.0-only",
       "dependencies": {
         "@react-native-async-storage/async-storage": "2.2.0",
@@ -17,6 +17,7 @@
         "@react-navigation/native-stack": "^7.14.10",
         "date-fns": "^4.1.0",
         "expo": "~54.0.33",
+        "expo-document-picker": "~14.0.8",
         "expo-file-system": "~19.0.21",
         "expo-image-picker": "~17.0.10",
         "expo-intent-launcher": "~13.0.8",
@@ -5216,6 +5217,15 @@
         "react-native": "*"
       }
     },
+    "node_modules/expo-document-picker": {
+      "version": "14.0.8",
+      "resolved": "https://registry.npmjs.org/expo-document-picker/-/expo-document-picker-14.0.8.tgz",
+      "integrity": "sha512-3tyQKpPqWWFlI8p9RiMX1+T1Zge5mEKeBuXWp1h8PEItFMUDSiOJbQ112sfdC6Hxt8wSxreV9bCRl/NgBdt+fA==",
+      "license": "MIT",
+      "peerDependencies": {
+        "expo": "*"
+      }
+    },
     "node_modules/expo-file-system": {
       "version": "19.0.21",
       "resolved": "https://registry.npmjs.org/expo-file-system/-/expo-file-system-19.0.21.tgz",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "bulwark-mobile",
-  "version": "0.1.21",
+  "version": "0.1.29",
   "license": "AGPL-3.0-only",
   "main": "index.ts",
   "scripts": {
@@ -10,6 +10,7 @@
     "web": "expo start --web",
     "test": "vitest run",
     "test:watch": "vitest",
+    "typecheck": "tsc --noEmit",
     "bump": "node scripts/bump-version.mjs",
     "sync-locales": "node scripts/sync-locales.mjs"
   },
@@ -22,6 +23,7 @@
     "@react-navigation/native-stack": "^7.14.10",
     "date-fns": "^4.1.0",
     "expo": "~54.0.33",
+    "expo-document-picker": "~14.0.8",
     "expo-file-system": "~19.0.21",
     "expo-image-picker": "~17.0.10",
     "expo-intent-launcher": "~13.0.8",

src/api/__tests__/calendar.test.ts

@@ -4,6 +4,7 @@ vi.mock('../jmap-client', () => ({
   jmapClient: {
     accountId: 'acc-1',
     request: vi.fn(),
+    getMaxObjectsInGet: () => 500,
   },
 }));
 
@@ -41,7 +42,10 @@ describe('calendar operations', () => {
   });
 
   describe('queryEvents', () => {
-    it('should query events within date range', async () => {
+    it('should send a CalendarEvent/query without server-side filter', async () => {
+      // Stalwart rejects inCalendars/after/before, so we fetch unfiltered and
+      // filter client-side. Asserting on the absence of `filter` keeps that
+      // contract pinned.
       mockRequest.mockResolvedValue({
         methodResponses: [['CalendarEvent/query', { ids: ['ev1', 'ev2'] }, '0']],
       });
@@ -50,12 +54,9 @@ describe('calendar operations', () => {
       expect(result).toEqual(['ev1', 'ev2']);
 
       const call = mockRequest.mock.calls[0][0][0];
-      expect(call[1].filter).toEqual({
-        inCalendars: ['cal-1'],
-        after: '2026-03-01T00:00:00Z',
-        before: '2026-03-31T23:59:59Z',
-        types: ['Event'],
-      });
+      expect(call[0]).toBe('CalendarEvent/query');
+      expect(call[1].filter).toBeUndefined();
+      expect(call[1].accountId).toBe('acc-1');
     });
   });
 

src/api/__tests__/contacts.test.ts

@@ -4,6 +4,7 @@ vi.mock('../jmap-client', () => ({
   jmapClient: {
     accountId: 'acc-1',
     request: vi.fn(),
+    getMaxObjectsInGet: () => 500,
   },
 }));
 
@@ -50,14 +51,14 @@ describe('contacts operations', () => {
       expect(result).toEqual(['c1', 'c2']);
     });
 
-    it('should use default empty filter', async () => {
+    it('should omit filter when none provided', async () => {
       mockRequest.mockResolvedValue({
         methodResponses: [['ContactCard/query', { ids: [] }, '0']],
       });
 
       await queryContacts();
       const call = mockRequest.mock.calls[0][0][0];
-      expect(call[1].filter).toEqual({});
+      expect(call[1].filter).toBeUndefined();
     });
   });
 

src/api/__tests__/email.test.ts

@@ -90,6 +90,24 @@ describe('email operations', () => {
       const call = mockRequest.mock.calls[0][0][0];
       expect(call[1].filter).toEqual({ inMailbox: 'mb-1', hasKeyword: '$flagged' });
     });
+
+    it('should AND-wrap a FilterOperator instead of spreading it', async () => {
+      mockRequest.mockResolvedValue({
+        methodResponses: [['Email/query', { ids: [], total: 0 }, '0']],
+      });
+
+      const userFilter = {
+        operator: 'AND',
+        conditions: [{ inMailbox: 'mb-1' }, { notKeyword: '$seen' }],
+      };
+      await queryEmails('mb-1', { filter: userFilter });
+
+      const call = mockRequest.mock.calls[0][0][0];
+      expect(call[1].filter).toEqual({
+        operator: 'AND',
+        conditions: [{ inMailbox: 'mb-1' }, userFilter],
+      });
+    });
   });
 
   describe('getEmails', () => {
@@ -197,7 +215,7 @@ describe('email operations', () => {
 
       expect(result).toEqual(['e1']);
       const call = mockRequest.mock.calls[0][0][0];
-      expect(call[1].filter).toEqual({ text: 'test query' });
+      expect(call[1].filter).toEqual({ text: 'test* query*' });
     });
 
     it('should include mailbox filter if specified', async () => {
@@ -208,7 +226,7 @@ describe('email operations', () => {
       await searchEmails('query', 'mb-1');
 
       const call = mockRequest.mock.calls[0][0][0];
-      expect(call[1].filter).toEqual({ text: 'query', inMailbox: 'mb-1' });
+      expect(call[1].filter).toEqual({ text: 'query*', inMailbox: 'mb-1' });
     });
   });
 

src/api/blob.ts

@@ -61,6 +61,57 @@ export async function uploadBlob(
   throw new Error('Upload succeeded but response did not include a blobId');
 }
 
+// Direct in-memory upload. The on-disk variant goes through expo-file-system's
+// `new File(uri).bytes()`, which is overkill when we already have the bytes
+// (e.g. the empty-blob trick used to create directories on Stalwart).
+export async function uploadBytes(
+  bytes: Uint8Array,
+  type: string,
+): Promise<{ blobId: string; size: number; type: string }> {
+  const session = jmapClient.currentSession;
+  if (!session) throw new Error('Not connected');
+
+  const uploadUrl = session.uploadUrl.replace(
+    '{accountId}',
+    encodeURIComponent(jmapClient.accountId),
+  );
+
+  const response = await secureFetch(uploadUrl, {
+    method: 'POST',
+    headers: {
+      'Content-Type': type || 'application/octet-stream',
+      Authorization: jmapClient.authHeader,
+    },
+    body: bytes.buffer as ArrayBuffer,
+  });
+
+  if (!response.ok) {
+    const detail = await response.text().catch(() => '');
+    throw new Error(`Upload failed: ${response.status}${detail ? ` ${detail}` : ''}`);
+  }
+
+  const raw = (await response.json()) as Record<string, unknown>;
+  const direct = raw as { blobId?: string; type?: string; size?: number };
+  if (typeof direct.blobId === 'string') {
+    return {
+      blobId: direct.blobId,
+      size: typeof direct.size === 'number' ? direct.size : bytes.byteLength,
+      type: typeof direct.type === 'string' && direct.type ? direct.type : type,
+    };
+  }
+  const nested = raw[jmapClient.accountId] as
+    | { blobId?: string; type?: string; size?: number }
+    | undefined;
+  if (nested?.blobId) {
+    return {
+      blobId: nested.blobId,
+      size: typeof nested.size === 'number' ? nested.size : bytes.byteLength,
+      type: typeof nested.type === 'string' && nested.type ? nested.type : type,
+    };
+  }
+  throw new Error('Upload succeeded but response did not include a blobId');
+}
+
 export function getDownloadUrl(
   blobId: string,
   name?: string,

src/api/email.ts

@@ -93,10 +93,22 @@ export async function queryEmails(
   },
 ): Promise<{ ids: string[]; total: number }> {
   const accountId = jmapClient.accountId;
+  const inMailbox = { inMailbox: mailboxId };
+  const userFilter = options?.filter;
+  // JMAP filters are either a FilterCondition or a FilterOperator (operator +
+  // conditions) — never both. Spreading a FilterOperator next to `inMailbox`
+  // produces a hybrid object that servers reduce to the FilterCondition,
+  // silently dropping the operator's conditions (e.g. the "unread" toggle).
+  const filter =
+    !userFilter || Object.keys(userFilter).length === 0
+      ? inMailbox
+      : 'operator' in userFilter
+        ? { operator: 'AND', conditions: [inMailbox, userFilter] }
+        : { ...inMailbox, ...userFilter };
   const res = await jmapClient.request([
     ['Email/query', {
       accountId,
-      filter: { inMailbox: mailboxId, ...options?.filter },
+      filter,
       sort: options?.sort ?? [{ property: 'receivedAt', isAscending: false }],
       position: options?.position ?? 0,
       limit: options?.limit ?? 50,
@@ -135,6 +147,26 @@ export async function getFullEmail(id: string): Promise<Email> {
   return email;
 }
 
+// Batch variant for offline sync. JMAP servers cap how many objects can be
+// returned in a single Email/get; the caller should chunk to that ceiling
+// (the client exposes maxObjectsInGet via getMaxObjectsInGet()).
+export async function getFullEmails(ids: string[]): Promise<Email[]> {
+  if (ids.length === 0) return [];
+  const accountId = jmapClient.accountId;
+  const res = await jmapClient.request([
+    ['Email/get', {
+      accountId,
+      ids,
+      properties: EMAIL_FULL_PROPERTIES,
+      fetchHTMLBodyValues: true,
+      fetchTextBodyValues: true,
+      fetchAllBodyValues: true,
+      maxBodyValueBytes: 512000,
+    }, '0'],
+  ]);
+  return res.methodResponses[0][1].list as Email[];
+}
+
 export async function getThread(threadId: string): Promise<Thread> {
   const accountId = jmapClient.accountId;
   const res = await jmapClient.request(

src/api/files.ts

@@ -1,19 +1,68 @@
 import { jmapClient } from './jmap-client';
 import { CAPABILITIES } from './types';
 import type { FileNode } from './types';
+import { getDownloadUrl, uploadBlob, uploadBytes } from './blob';
 
-const USING = [CAPABILITIES.CORE, CAPABILITIES.MAIL];
+const USING = [CAPABILITIES.CORE, CAPABILITIES.FILES];
 
-export async function getFileNodes(parentId?: string | null): Promise<FileNode[]> {
+// Stalwart and other JMAP servers use one of these strings on FileNode.type to
+// mark a directory; everything else is a MIME type.
+const DIRECTORY_TYPES = new Set([
+  'd',
+  'application/x-directory',
+  'text/directory',
+  'httpd/unix-directory',
+  'inode/directory',
+]);
+
+export function isDirectory(node: Pick<FileNode, 'type'>): boolean {
+  const t = node.type;
+  if (!t) return false;
+  return DIRECTORY_TYPES.has(t) || t.includes('directory');
+}
+
+// Stalwart rejects `/` in FileNode names, so the webmail (and now this app)
+// uses U+2215 DIVISION SLASH as the path separator inside the flat `name`
+// field. Hierarchy is encoded into the name — there is no `parentId` nesting.
+// e.g. a file inside the `Documents` folder is stored with
+// `name = "Documents∕report.pdf"`. The display name shown to the user
+// strips the prefix.
+export const PATH_SEP = '∕';
+
+// Path is a list of folder display names from root. [] is root,
+// ['Documents'] is inside Documents, ['Documents','sub'] is inside the
+// `sub` folder under Documents.
+export function pathToPrefix(path: readonly string[]): string {
+  if (path.length === 0) return '';
+  return path.join(PATH_SEP) + PATH_SEP;
+}
+
+// True when `node` is a direct child (not a descendant) of `prefix`.
+export function isDirectChildOfPrefix(node: Pick<FileNode, 'name'>, prefix: string): boolean {
+  if (!node.name) return false;
+  if (prefix === '') return !node.name.includes(PATH_SEP);
+  if (!node.name.startsWith(prefix)) return false;
+  const rest = node.name.slice(prefix.length);
+  return rest.length > 0 && !rest.includes(PATH_SEP);
+}
+
+export function nodeDisplayName(node: Pick<FileNode, 'name'>, prefix: string): string {
+  return prefix && node.name.startsWith(prefix) ? node.name.slice(prefix.length) : node.name;
+}
+
+// Stalwart's FileNode/get does not support a parentId filter and some builds
+// omit `type` from the default property set. We fetch the whole tree and
+// filter client-side; properties are listed explicitly so `isDirectory()`
+// always has a value to look at.
+const FILE_NODE_PROPERTIES = ['id', 'parentId', 'name', 'type', 'blobId', 'size', 'created', 'updated'];
+
+export async function getAllFileNodes(): Promise<FileNode[]> {
   const accountId = jmapClient.accountId;
-  const filter: Record<string, unknown> = {};
-  if (parentId !== undefined) filter.parentId = parentId;
-
   const res = await jmapClient.request(
-    [['FileNode/get', { accountId, filter }, '0']],
+    [['FileNode/get', { accountId, ids: null, properties: FILE_NODE_PROPERTIES }, '0']],
     USING,
   );
-  return res.methodResponses[0][1].list;
+  return (res.methodResponses[0][1].list ?? []) as FileNode[];
 }
 
 export async function createFileNode(
@@ -27,13 +76,113 @@ export async function createFileNode(
     }, '0']],
     USING,
   );
-  return res.methodResponses[0][1].created['new-file'];
+  const created = res.methodResponses[0][1].created?.['new-file'];
+  if (!created) {
+    const err = res.methodResponses[0][1].notCreated?.['new-file'];
+    throw new Error(err?.description || 'Create failed');
+  }
+  return created;
+}
+
+export async function createFolder(
+  displayName: string,
+  currentPath: readonly string[],
+): Promise<FileNode> {
+  // Stalwart's FileNode/set rejects directory creates without a blobId
+  // ("Missing blob id"), so we upload an empty blob first and reference it.
+  // Mirrors the webmail's createFileDirectory.
+  const blob = await uploadBytes(new Uint8Array(0), 'application/x-directory');
+  const fullName = pathToPrefix(currentPath) + displayName;
+  return createFileNode({ name: fullName, type: 'd', blobId: blob.blobId, size: 0 });
+}
+
+export async function updateFileNode(
+  id: string,
+  updates: Partial<Pick<FileNode, 'name' | 'parentId'>>,
+): Promise<void> {
+  const accountId = jmapClient.accountId;
+  const res = await jmapClient.request(
+    [['FileNode/set', { accountId, update: { [id]: updates } }, '0']],
+    USING,
+  );
+  const notUpdated = res.methodResponses[0][1].notUpdated?.[id];
+  if (notUpdated) throw new Error(notUpdated.description || 'Update failed');
+}
+
+// Rename a node and, if it's a folder, cascade the rename to every descendant
+// so the encoded path stays consistent. The webmail does this same dance.
+export async function renameFileNode(
+  node: FileNode,
+  newDisplayName: string,
+  currentPath: readonly string[],
+  allNodes: readonly FileNode[],
+): Promise<void> {
+  const prefix = pathToPrefix(currentPath);
+  const oldServerName = node.name;
+  const newServerName = prefix + newDisplayName;
+  if (oldServerName === newServerName) return;
+
+  await updateFileNode(node.id, { name: newServerName });
+
+  if (isDirectory(node)) {
+    const oldFolderPrefix = oldServerName + PATH_SEP;
+    const newFolderPrefix = newServerName + PATH_SEP;
+    for (const n of allNodes) {
+      if (n.id === node.id) continue;
+      if (n.name.startsWith(oldFolderPrefix)) {
+        await updateFileNode(n.id, { name: newFolderPrefix + n.name.slice(oldFolderPrefix.length) });
+      }
+    }
+  }
 }
 
 export async function deleteFileNodes(ids: string[]): Promise<void> {
+  if (ids.length === 0) return;
   const accountId = jmapClient.accountId;
   await jmapClient.request(
     [['FileNode/set', { accountId, destroy: ids }, '0']],
     USING,
   );
 }
+
+// Delete `targets` and every descendant. Stalwart doesn't enforce parent
+// references, so we collect descendants by name-prefix and destroy them all
+// in one call. Without this, deleting a folder leaves its files orphaned and
+// still discoverable at the old encoded path.
+export async function deleteWithDescendants(
+  targets: readonly FileNode[],
+  allNodes: readonly FileNode[],
+): Promise<void> {
+  const ids = new Set<string>();
+  for (const node of targets) {
+    ids.add(node.id);
+    if (isDirectory(node)) {
+      const folderPrefix = node.name + PATH_SEP;
+      for (const n of allNodes) {
+        if (n.name.startsWith(folderPrefix)) ids.add(n.id);
+      }
+    }
+  }
+  await deleteFileNodes(Array.from(ids));
+}
+
+export function getFileNodeDownloadUrl(node: FileNode): string {
+  if (!node.blobId) throw new Error('Folders cannot be downloaded');
+  return getDownloadUrl(node.blobId, node.name, node.type);
+}
+
+export async function uploadFileNode(
+  uri: string,
+  displayName: string,
+  mimeType: string,
+  currentPath: readonly string[],
+): Promise<FileNode> {
+  const blob = await uploadBlob(uri, mimeType);
+  const fullName = pathToPrefix(currentPath) + displayName;
+  return createFileNode({
+    name: fullName,
+    type: blob.type || mimeType || 'application/octet-stream',
+    blobId: blob.blobId,
+    size: blob.size,
+  });
+}

src/api/push.ts

@@ -201,13 +201,35 @@ export function startPolling(
   return () => clearInterval(timer);
 }
 
+export interface StartPushOptions {
+  onStateChange: StateChangeHandler;
+  onError?: (error: Error) => void;
+}
+
 /**
- * Start real-time updates, preferring SSE with polling fallback.
+ * Start real-time updates, preferring SSE with polling fallback. The `_client`
+ * argument is unused today (the underlying event source uses the singleton
+ * `jmapClient`) but is part of the call signature so the host App can pass
+ * the active client reference and trigger React re-runs on account switch.
  */
 export function startPushUpdates(
-  onStateChange: StateChangeHandler,
+  _client: unknown,
+  opts: StartPushOptions,
 ): () => void {
-  const cleanup = connectEventSource(onStateChange);
-  if (cleanup) return cleanup;
-  return startPolling(onStateChange);
+  const onError = opts.onError;
+  const safeOnStateChange: StateChangeHandler = (change) => {
+    try {
+      opts.onStateChange(change);
+    } catch (err) {
+      if (onError) onError(err instanceof Error ? err : new Error(String(err)));
+    }
+  };
+  try {
+    const cleanup = connectEventSource(safeOnStateChange);
+    if (cleanup) return cleanup;
+    return startPolling(safeOnStateChange);
+  } catch (err) {
+    if (onError) onError(err instanceof Error ? err : new Error(String(err)));
+    return () => undefined;
+  }
 }

src/api/types.ts

@@ -429,7 +429,7 @@ export interface FileNode {
   name: string;
   parentId?: string | null;
   type: string;
-  blobId?: string;
+  blobId?: string | null;
   size?: number;
   created?: string;
   updated?: string;
@@ -465,4 +465,5 @@ export const CAPABILITIES = {
   CALENDARS: 'urn:ietf:params:jmap:calendars',
   SIEVE: 'urn:ietf:params:jmap:sieve',
   QUOTA: 'urn:ietf:params:jmap:quota',
+  FILES: 'urn:ietf:params:jmap:filenode',
 } as const;

src/api/updates.ts

@@ -13,6 +13,45 @@ export interface LatestRelease {
   publishedAt: string;
   body: string;
   apkAsset: ReleaseAsset | null;
+  // Lower-case hex SHA-256 of the APK, parsed from a `*.apk.sha256` companion
+  // asset or from the release body. Null when the release didn't publish one;
+  // the installer falls back to relying solely on Android's package signing
+  // check in that case (still strong, but less defense-in-depth).
+  apkSha256: string | null;
+}
+
+const SHA256_RE = /\b([a-f0-9]{64})\b/i;
+
+function extractSha256(body: string, apkName: string | undefined): string | null {
+  if (!body) return null;
+  // Prefer a line that explicitly references the APK so we don't pick up the
+  // hash of an unrelated asset.
+  const lines = body.split(/\r?\n/);
+  if (apkName) {
+    for (const line of lines) {
+      if (line.includes(apkName)) {
+        const m = SHA256_RE.exec(line);
+        if (m) return m[1].toLowerCase();
+      }
+    }
+  }
+  // Fallback: a single SHA256 anywhere in the body — common when the release
+  // notes just list one checksum.
+  const m = SHA256_RE.exec(body);
+  return m ? m[1].toLowerCase() : null;
+}
+
+async function fetchCompanionSha256(asset: ReleaseAsset | undefined): Promise<string | null> {
+  if (!asset) return null;
+  try {
+    const res = await fetch(asset.browser_download_url);
+    if (!res.ok) return null;
+    const text = await res.text();
+    const m = SHA256_RE.exec(text);
+    return m ? m[1].toLowerCase() : null;
+  } catch {
+    return null;
+  }
 }
 
 export async function fetchLatestRelease(repo: string = UPDATE_REPO): Promise<LatestRelease | null> {
@@ -32,6 +71,14 @@ export async function fetchLatestRelease(repo: string = UPDATE_REPO): Promise<La
     assets: ReleaseAsset[];
   };
   const apkAsset = json.assets.find((a) => a.name.endsWith('.apk')) ?? null;
+  const sha256Asset = apkAsset
+    ? json.assets.find(
+        (a) => a.name === `${apkAsset.name}.sha256` || a.name === `${apkAsset.name}.SHA256`,
+      )
+    : undefined;
+  const apkSha256 =
+    (await fetchCompanionSha256(sha256Asset)) ??
+    extractSha256(json.body || '', apkAsset?.name);
   return {
     tag: json.tag_name,
     name: json.name || json.tag_name,
@@ -39,5 +86,6 @@ export async function fetchLatestRelease(repo: string = UPDATE_REPO): Promise<La
     publishedAt: json.published_at,
     body: json.body || '',
     apkAsset,
+    apkSha256,
   };
 }

src/components/EmailBodyView.tsx

@@ -297,7 +297,7 @@ export default function EmailBodyView({ email, senderEmail }: EmailBodyViewProps
       <View style={[styles.webContainer, { height }]}>
         <WebView
           ref={webviewRef}
-          originWhitelist={['about:*']}
+          originWhitelist={['about:blank']}
           source={source}
           javaScriptEnabled
           injectedJavaScript={HEIGHT_REPORTER}

src/components/OfflineCacheBanner.tsx

@@ -0,0 +1,143 @@
+// Live banner that mirrors the UpdateBanner's footprint, surfaced while the
+// offline mail sync is running. Hidden once the sync settles to idle/done.
+
+import React from 'react';
+import { View, Text, StyleSheet, Pressable } from 'react-native';
+import { useSafeAreaInsets } from 'react-native-safe-area-context';
+import { CloudDownload, X } from 'lucide-react-native';
+import { useOfflineCacheStore } from '../stores/offline-cache-store';
+import { useUpdatesStore } from '../stores/updates-store';
+import { formatBytes } from '../lib/offline-sync';
+import { spacing, radius, typography, type ThemePalette } from '../theme/tokens';
+import { useColors } from '../theme/colors';
+
+export function OfflineCacheBanner(): React.ReactElement | null {
+  const c = useColors();
+  const styles = React.useMemo(() => makeStyles(c), [c]);
+  const insets = useSafeAreaInsets();
+  const sync = useOfflineCacheStore((s) => s.sync);
+  const requestAbort = useOfflineCacheStore((s) => s.requestAbort);
+  const resetSync = useOfflineCacheStore((s) => s.resetSync);
+  // When UpdateBanner is stacked above us it already absorbs the status-bar
+  // inset, so we only add it when we're the topmost banner.
+  const cachedLatest = useUpdatesStore((s) => s.cachedLatest);
+  const dismissedTag = useUpdatesStore((s) => s.dismissedTag);
+  const hasUpdate = useUpdatesStore((s) => s.hasUpdate);
+  const updateBannerVisible =
+    hasUpdate() && cachedLatest?.apkAsset != null && dismissedTag !== cachedLatest.tag;
+  const topInset = updateBannerVisible ? 0 : insets.top;
+  const [hideTimer, setHideTimer] = React.useState<ReturnType<typeof setTimeout> | null>(null);
+
+  // Auto-dismiss the "done" state after a few seconds so the bar isn't a
+  // permanent fixture; the Settings screen still shows the cache stats.
+  React.useEffect(() => {
+    if (sync.phase === 'done' || sync.phase === 'cancelled') {
+      const t = setTimeout(() => resetSync(), 4000);
+      setHideTimer(t);
+      return () => clearTimeout(t);
+    }
+    if (hideTimer) clearTimeout(hideTimer);
+    return undefined;
+  // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [sync.phase, resetSync]);
+
+  if (sync.phase === 'idle') return null;
+
+  const pct =
+    sync.total > 0
+      ? Math.min(100, Math.round((sync.completed / sync.total) * 100))
+      : sync.phase === 'done' ? 100 : 0;
+
+  let title = 'Offline sync';
+  let subtitle = '';
+  switch (sync.phase) {
+    case 'scanning':
+      title = 'Syncing offline mail';
+      subtitle = 'Scanning recent messages…';
+      break;
+    case 'fetching':
+      title = 'Syncing offline mail';
+      subtitle = `${sync.completed}/${sync.total} • ${formatBytes(sync.bytes)}`;
+      break;
+    case 'done':
+      title = 'Offline mail ready';
+      subtitle = sync.fetched > 0
+        ? `${sync.fetched} new message${sync.fetched === 1 ? '' : 's'} cached • ${formatBytes(sync.bytes)}`
+        : 'Already up to date';
+      break;
+    case 'cancelled':
+      title = 'Sync cancelled';
+      subtitle = `${sync.completed}/${sync.total} processed`;
+      break;
+    case 'error':
+      title = 'Offline sync failed';
+      subtitle = sync.message ?? 'Unable to download';
+      break;
+    default:
+      return null;
+  }
+
+  const showCancel = sync.phase === 'scanning' || sync.phase === 'fetching';
+  const showDismiss = sync.phase === 'done' || sync.phase === 'cancelled' || sync.phase === 'error';
+  const isError = sync.phase === 'error';
+
+  return (
+    <View style={[styles.banner, isError && styles.bannerError, { paddingTop: spacing.sm + topInset }]}>
+      <CloudDownload size={16} color={c.primaryForeground} />
+      <View style={{ flex: 1 }}>
+        <Text style={styles.title}>{title}</Text>
+        {!!subtitle && <Text style={styles.subtitle}>{subtitle}</Text>}
+        {(sync.phase === 'fetching' || sync.phase === 'scanning') && (
+          <View style={styles.progressTrack}>
+            <View style={[styles.progressFill, { width: `${pct}%` }]} />
+          </View>
+        )}
+      </View>
+      {showCancel && (
+        <Pressable style={styles.cancelButton} onPress={requestAbort} hitSlop={6}>
+          <Text style={styles.cancelText}>Cancel</Text>
+        </Pressable>
+      )}
+      {showDismiss && (
+        <Pressable style={styles.dismiss} onPress={resetSync} hitSlop={8}>
+          <X size={14} color={c.primaryForeground} />
+        </Pressable>
+      )}
+    </View>
+  );
+}
+
+function makeStyles(c: ThemePalette) {
+  return StyleSheet.create({
+    banner: {
+      flexDirection: 'row',
+      alignItems: 'center',
+      gap: spacing.md,
+      paddingHorizontal: spacing.lg,
+      paddingVertical: spacing.sm,
+      backgroundColor: c.primary,
+    },
+    bannerError: { backgroundColor: c.error },
+    title: { ...typography.bodyMedium, color: c.primaryForeground },
+    subtitle: { ...typography.caption, color: c.primaryForeground, opacity: 0.85, marginTop: 2 },
+    progressTrack: {
+      marginTop: 6,
+      height: 3,
+      borderRadius: radius.full,
+      backgroundColor: 'rgba(255,255,255,0.25)',
+      overflow: 'hidden',
+    },
+    progressFill: {
+      height: '100%',
+      backgroundColor: c.primaryForeground,
+    },
+    cancelButton: {
+      paddingHorizontal: spacing.md,
+      paddingVertical: 6,
+      borderRadius: radius.sm,
+      backgroundColor: 'rgba(255,255,255,0.2)',
+    },
+    cancelText: { ...typography.captionMedium, color: c.primaryForeground },
+    dismiss: { padding: 4 },
+  });
+}

src/components/RichTextEditor.tsx

@@ -263,20 +263,30 @@ function buildEditorHtml(opts: {
     },
     insertLink: function (url, label) {
       editor.focus();
+      // Reject anything that isn't a safe scheme or an absolute path, so the
+      // user can't accidentally (or via a malicious paste) ship a
+      // javascript:/data: link to their recipient.
+      var safeSchemeRe = /^(https?:|mailto:|tel:|sms:|\/|\?|#)/i;
+      var trimmed = (url || '').trim();
+      if (!trimmed || !safeSchemeRe.test(trimmed)) return;
       var sel = window.getSelection();
       var hasSelection = sel && sel.rangeCount && !sel.getRangeAt(0).collapsed;
       if (hasSelection) {
-        try { document.execCommand('createLink', false, url); } catch (e) {}
+        try { document.execCommand('createLink', false, trimmed); } catch (e) {}
         // execCommand doesn't set rel; tag every anchor that points at this URL.
         Array.prototype.forEach.call(editor.getElementsByTagName('a'), function (a) {
-          if (a.getAttribute('href') === url) {
+          if (a.getAttribute('href') === trimmed) {
             a.setAttribute('rel', 'noopener noreferrer nofollow');
           }
         });
       } else {
-        var text = label && label.trim() ? label : url;
+        var text = label && label.trim() ? label : trimmed;
         var safe = text.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
-        var safeUrl = url.replace(/"/g, '&quot;');
+        var safeUrl = trimmed
+          .replace(/&/g, '&amp;')
+          .replace(/"/g, '&quot;')
+          .replace(/</g, '&lt;')
+          .replace(/>/g, '&gt;');
         var html = '<a href="' + safeUrl + '" rel="noopener noreferrer nofollow">' + safe + '</a>';
         try { document.execCommand('insertHTML', false, html); } catch (e) {}
       }
@@ -409,7 +419,7 @@ const RichTextEditor = React.forwardRef<RichTextEditorHandle, Props>(function Ri
     <View style={[styles.container, { height }]}>
       <WebView
         ref={webViewRef}
-        originWhitelist={['about:*']}
+        originWhitelist={['about:blank']}
         source={{ html }}
         onMessage={onMessage}
         javaScriptEnabled
@@ -433,9 +443,11 @@ const RichTextEditor = React.forwardRef<RichTextEditorHandle, Props>(function Ri
         style={styles.webview}
         containerStyle={styles.webviewContainer}
         onShouldStartLoadWithRequest={(request) => {
-          // Allow only the initial about:blank doc + data URIs we emit ourselves.
+          // Allow only the initial about:blank doc + data URIs we emit
+          // ourselves. Reject `about:*` (e.g. about:srcdoc) and every other
+          // scheme so a paste-injected anchor can't navigate the editor.
           const url = request.url;
-          return !url || url === 'about:blank' || url.startsWith('data:') || url.startsWith('about:');
+          return !url || url === 'about:blank' || url.startsWith('data:');
         }}
       />
     </View>

src/components/settings/AboutDataSettings.tsx

@@ -1,16 +1,36 @@
 import React, { useEffect, useState } from 'react';
-import { View, Text, StyleSheet, Pressable, Linking, Alert } from 'react-native';
+import { View, Text, StyleSheet, Pressable, Linking, Alert, ActivityIndicator } from 'react-native';
 import Constants from 'expo-constants';
-import { ExternalLink } from 'lucide-react-native';
-import { SettingsSection, SettingItem, ToggleSwitch } from './settings-section';
+import { CloudDownload, ExternalLink } from 'lucide-react-native';
+import { SettingsSection, SettingItem, Select, ToggleSwitch } from './settings-section';
 import Button from '../Button';
 import { spacing, radius, typography, type ThemePalette } from '../../theme/tokens';
 import { useColors } from '../../theme/colors';
 import { useSettingsStore } from '../../stores/settings-store';
+import { useOfflineCacheStore } from '../../stores/offline-cache-store';
+import { runOfflineSync, formatBytes } from '../../lib/offline-sync';
 
 const APP_VERSION = Constants.expoConfig?.version ?? '0.0.0';
 const GIT_COMMIT = (Constants.expoConfig?.extra as { commit?: string } | undefined)?.commit ?? 'dev';
 
+const DAY_OPTIONS = [
+  { value: '1',  label: 'Last 24 hours' },
+  { value: '3',  label: 'Last 3 days' },
+  { value: '7',  label: 'Last 7 days' },
+  { value: '14', label: 'Last 14 days' },
+  { value: '30', label: 'Last 30 days' },
+  { value: '90', label: 'Last 90 days' },
+];
+
+function formatRelativeTime(ms: number | undefined): string {
+  if (!ms) return 'never';
+  const diff = Date.now() - ms;
+  if (diff < 60_000) return 'just now';
+  if (diff < 60 * 60_000) return `${Math.round(diff / 60_000)} min ago`;
+  if (diff < 24 * 60 * 60_000) return `${Math.round(diff / (60 * 60_000))} h ago`;
+  return `${Math.round(diff / (24 * 60 * 60_000))} d ago`;
+}
+
 const DEBUG_CATEGORIES = [
   { id: 'jmap',       label: 'JMAP',       description: 'JMAP request and response logs.' },
   { id: 'auth',       label: 'Auth',       description: 'Authentication and session events.' },
@@ -36,9 +56,36 @@ export function AboutDataSettings() {
   const [syncEnabled, setSyncEnabled] = useState(true);
   const [confirmReset, setConfirmReset] = useState(false);
 
+  const offlineEnabled = useSettingsStore((s) => s.offlineCacheEnabled);
+  const offlineDays = useSettingsStore((s) => s.offlineCacheDays);
+  const updateSetting = useSettingsStore((s) => s.updateSetting);
+  const cacheCount = useOfflineCacheStore((s) => s.totalCount());
+  const cacheBytes = useOfflineCacheStore((s) => s.totalSize());
+  const cacheHydrated = useOfflineCacheStore((s) => s.hydrated);
+  const cacheHydrate = useOfflineCacheStore((s) => s.hydrate);
+  const sync = useOfflineCacheStore((s) => s.sync);
+  const clearAllCache = useOfflineCacheStore((s) => s.clearAll);
+  const syncBusy = sync.phase === 'scanning' || sync.phase === 'fetching';
+
   useEffect(() => {
     if (!hydrated) void hydrate();
-  }, [hydrated, hydrate]);
+    if (!cacheHydrated) void cacheHydrate();
+  }, [hydrated, hydrate, cacheHydrated, cacheHydrate]);
+
+  const handleSyncNow = () => {
+    void runOfflineSync({ days: offlineDays });
+  };
+
+  const handleClearCache = () => {
+    Alert.alert(
+      'Clear offline mail',
+      `Remove ${cacheCount} cached message${cacheCount === 1 ? '' : 's'} (${formatBytes(cacheBytes)})?`,
+      [
+        { text: 'Cancel', style: 'cancel' },
+        { text: 'Clear', style: 'destructive', onPress: () => { void clearAllCache(); } },
+      ],
+    );
+  };
 
   const handleReset = () => {
     resetExternalContentPolicy('ask');
@@ -72,6 +119,80 @@ export function AboutDataSettings() {
         </View>
       </View>
 
+      <SettingsSection
+        title="Offline mail"
+        description="Download recent messages so they open instantly and remain readable without a connection. Bodies only — attachments are still fetched on demand."
+      >
+        <SettingItem
+          label="Cache recent mail"
+          description="When on, the app keeps message bodies for the selected window on this device."
+        >
+          <ToggleSwitch
+            checked={offlineEnabled}
+            onChange={(v) => updateSetting('offlineCacheEnabled', v)}
+          />
+        </SettingItem>
+        <SettingItem
+          label="Window"
+          description="How far back to cache, measured by message receipt date."
+        >
+          <Select
+            value={String(offlineDays)}
+            onChange={(v) => updateSetting('offlineCacheDays', Number(v))}
+            options={DAY_OPTIONS}
+          />
+        </SettingItem>
+
+        <View style={styles.cacheStatsBox}>
+          <View style={styles.cacheStatsHeader}>
+            <CloudDownload size={16} color={c.textSecondary} />
+            <Text style={styles.cacheStatsTitle}>
+              {cacheCount === 0
+                ? 'Nothing cached yet'
+                : `${cacheCount} message${cacheCount === 1 ? '' : 's'} • ${formatBytes(cacheBytes)}`}
+            </Text>
+          </View>
+          <Text style={styles.cacheStatsSub}>
+            {sync.phase === 'fetching'
+              ? `Downloading ${sync.completed}/${sync.total}…`
+              : sync.phase === 'scanning'
+                ? 'Scanning recent mail…'
+                : sync.phase === 'error'
+                  ? `Last sync failed: ${sync.message ?? 'unknown error'}`
+                  : `Last sync ${formatRelativeTime(sync.finishedAt)}`}
+          </Text>
+          {syncBusy && sync.total > 0 && (
+            <View style={styles.progressTrack}>
+              <View
+                style={[
+                  styles.progressFill,
+                  { width: `${Math.min(100, Math.round((sync.completed / sync.total) * 100))}%` },
+                ]}
+              />
+            </View>
+          )}
+          <View style={styles.cacheActions}>
+            <Button
+              variant="outline"
+              size="sm"
+              onPress={handleSyncNow}
+              disabled={!offlineEnabled || syncBusy}
+              icon={syncBusy ? <ActivityIndicator size="small" color={c.text} /> : undefined}
+            >
+              {syncBusy ? 'Syncing…' : 'Sync now'}
+            </Button>
+            <Button
+              variant="outline"
+              size="sm"
+              onPress={handleClearCache}
+              disabled={cacheCount === 0 || syncBusy}
+            >
+              Clear cache
+            </Button>
+          </View>
+        </View>
+      </SettingsSection>
+
       <SettingsSection title="Advanced" description="Low-level options and troubleshooting.">
         <SettingItem label="Debug mode" description="Enable verbose logging for support and development.">
           <ToggleSwitch checked={debugMode} onChange={setDebugMode} />
@@ -170,5 +291,29 @@ function makeStyles(c: ThemePalette) {
     color: c.mutedForeground,
     marginBottom: spacing.sm,
   },
+  cacheStatsBox: {
+    marginTop: spacing.md,
+    padding: spacing.md,
+    borderRadius: radius.md,
+    borderWidth: 1,
+    borderColor: c.border,
+    backgroundColor: c.muted,
+    gap: spacing.sm,
+  },
+  cacheStatsHeader: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    gap: spacing.sm,
+  },
+  cacheStatsTitle: { ...typography.bodyMedium, color: c.text, flex: 1 },
+  cacheStatsSub: { ...typography.caption, color: c.mutedForeground },
+  progressTrack: {
+    height: 4,
+    borderRadius: radius.full,
+    backgroundColor: c.border,
+    overflow: 'hidden',
+  },
+  progressFill: { height: '100%', backgroundColor: c.primary },
+  cacheActions: { flexDirection: 'row', gap: spacing.sm, marginTop: 4 },
 });
 }

src/lib/install-update.ts

@@ -3,12 +3,18 @@ import { File, Paths } from 'expo-file-system';
 import * as FileSystemLegacy from 'expo-file-system/legacy';
 import * as IntentLauncher from 'expo-intent-launcher';
 import type { ReleaseAsset } from '../api/updates';
+import { Sha256 } from './sha256';
 
 const FLAG_GRANT_READ_URI_PERMISSION = 0x00000001;
 const FLAG_ACTIVITY_NEW_TASK = 0x10000000;
 
+// Bytes per file-read chunk while computing the post-download SHA-256. Larger
+// chunks are faster but balloon the JS string buffer (base64 reads on this
+// platform). 256 KiB keeps memory bounded while still amortising the bridge.
+const HASH_CHUNK_BYTES = 256 * 1024;
+
 export interface InstallProgress {
-  phase: 'downloading' | 'installing';
+  phase: 'downloading' | 'verifying' | 'installing';
   /** 0-1 during download; undefined for installing phase */
   progress?: number;
   /** Bytes received during current download */
@@ -19,10 +25,51 @@ export interface InstallProgress {
 
 export type InstallProgressListener = (p: InstallProgress) => void;
 
+export interface InstallParams {
+  asset: ReleaseAsset;
+  /** Optional lower-case hex SHA-256. When present, mismatched downloads abort. */
+  expectedSha256?: string | null;
+}
+
+function base64ToBytes(b64: string): Uint8Array {
+  const bin = globalThis.atob ? globalThis.atob(b64) : atob(b64);
+  const out = new Uint8Array(bin.length);
+  for (let i = 0; i < bin.length; i++) out[i] = bin.charCodeAt(i);
+  return out;
+}
+
+async function hashFile(uri: string, totalBytes: number, onProgress?: InstallProgressListener): Promise<string> {
+  const hasher = new Sha256();
+  let offset = 0;
+  while (offset < totalBytes || totalBytes === 0) {
+    const length = Math.min(HASH_CHUNK_BYTES, totalBytes ? totalBytes - offset : HASH_CHUNK_BYTES);
+    const chunkB64 = await FileSystemLegacy.readAsStringAsync(uri, {
+      encoding: FileSystemLegacy.EncodingType.Base64,
+      position: offset,
+      length,
+    });
+    if (!chunkB64) break;
+    const bytes = base64ToBytes(chunkB64);
+    if (bytes.length === 0) break;
+    hasher.update(bytes);
+    offset += bytes.length;
+    if (totalBytes > 0) {
+      onProgress?.({ phase: 'verifying', progress: offset / totalBytes });
+    }
+    if (bytes.length < length) break;
+  }
+  return hasher.digestHex();
+}
+
 export async function downloadAndInstallApk(
-  asset: ReleaseAsset,
+  params: InstallParams | ReleaseAsset,
   onProgress?: InstallProgressListener,
 ): Promise<void> {
+  // Backwards-compat: callers used to pass the asset directly. Promote to the
+  // params shape so the verification path is opt-in by passing a checksum.
+  const { asset, expectedSha256 }: InstallParams =
+    'asset' in params ? params : { asset: params, expectedSha256: null };
+
   if (Platform.OS !== 'android') {
     throw new Error('APK install is only supported on Android');
   }
@@ -53,6 +100,33 @@ export async function downloadAndInstallApk(
     throw new Error('APK download failed');
   }
 
+  // Size sanity check. GitHub's `assets[].size` is signed by their TLS cert,
+  // so a byte-count mismatch is a strong signal the file was truncated /
+  // tampered with in transport. Cheap to compute, fail-fast.
+  const info = await FileSystemLegacy.getInfoAsync(result.uri);
+  const actualSize = (info as { size?: number }).size ?? 0;
+  if (asset.size > 0 && actualSize !== asset.size) {
+    await tryDelete(result.uri);
+    throw new Error(
+      `APK size mismatch: expected ${asset.size} bytes, got ${actualSize}`,
+    );
+  }
+
+  // SHA-256 verification when the release publishes one. Without it, we still
+  // get Android's package-signer check at install time — which rejects an APK
+  // signed with a different key — but that fails late (after the user sees a
+  // confusing system dialog). Bailing here surfaces the problem cleanly.
+  if (expectedSha256) {
+    onProgress?.({ phase: 'verifying', progress: 0 });
+    const actual = await hashFile(result.uri, actualSize || asset.size, onProgress);
+    if (actual.toLowerCase() !== expectedSha256.toLowerCase()) {
+      await tryDelete(result.uri);
+      throw new Error(
+        `APK checksum mismatch: expected ${expectedSha256}, got ${actual}`,
+      );
+    }
+  }
+
   onProgress?.({ phase: 'installing' });
 
   const contentUri = await FileSystemLegacy.getContentUriAsync(result.uri);
@@ -64,6 +138,14 @@ export async function downloadAndInstallApk(
   });
 }
 
+async function tryDelete(uri: string): Promise<void> {
+  try {
+    await FileSystemLegacy.deleteAsync(uri, { idempotent: true });
+  } catch {
+    /* best effort */
+  }
+}
+
 /**
  * Open the system "Install unknown apps" settings page for this app, so the
  * user can grant permission to install APKs from the package installer.

src/lib/offline-sync.ts

@@ -0,0 +1,148 @@
+// Background sync that fills the offline mail cache. Runs the discovery
+// query (Email/query filtered by `after`), then fetches full bodies in
+// batches, reporting progress to the offline-cache-store so the
+// OfflineCacheBanner and the Settings screen can show live updates.
+
+import { jmapClient } from '../api/jmap-client';
+import { queryEmailsByFilter, getFullEmails } from '../api/email';
+import { useOfflineCacheStore } from '../stores/offline-cache-store';
+import type { Email } from '../api/types';
+
+// Approximate the on-disk size of a serialised Email so we can show "Y MB
+// downloaded" without measuring AsyncStorage usage. Body values dominate; the
+// envelope is small. Using JSON.stringify().length is correct in code-units
+// not bytes, but it's close enough for a UI-facing estimate.
+function approxSize(email: Email): number {
+  try {
+    return JSON.stringify(email).length;
+  } catch {
+    return 0;
+  }
+}
+
+// Hard cap so a misconfigured "30 days" against a noisy account doesn't try
+// to enumerate 100k messages.
+const DISCOVERY_LIMIT = 5000;
+// Each Email/get request is bounded by the server's maxObjectsInGet. We
+// further chunk to keep individual responses small (a 50-message response
+// with full bodies + body values is already several MB).
+const FETCH_CHUNK_FALLBACK = 25;
+
+export interface RunOptions {
+  days: number;
+}
+
+export async function runOfflineSync(opts: RunOptions): Promise<void> {
+  const cache = useOfflineCacheStore.getState();
+  // If a sync is in flight, request its abort and wait for the next caller
+  // to start fresh. We don't queue — the most recent intent wins.
+  if (cache.sync.phase === 'scanning' || cache.sync.phase === 'fetching') {
+    cache.requestAbort();
+    return;
+  }
+  if (!cache.hydrated) await cache.hydrate();
+  cache.resetSync();
+
+  const startedAt = Date.now();
+  cache.setSyncState({ phase: 'scanning', startedAt });
+
+  const since = new Date(startedAt - opts.days * 24 * 60 * 60 * 1000).toISOString();
+
+  let ids: string[] = [];
+  try {
+    ids = await queryEmailsByFilter({ after: since }, DISCOVERY_LIMIT);
+  } catch (err) {
+    cache.setSyncState({
+      phase: 'error',
+      message: err instanceof Error ? err.message : 'Discovery query failed',
+      finishedAt: Date.now(),
+    });
+    return;
+  }
+
+  // Drop entries from the cache that fell out of the lookback window — the
+  // user expects the cache to track "the last X days", not grow forever.
+  const keepSet = new Set(ids);
+  const stale = Object.keys(cache.index.entries).filter((id) => !keepSet.has(id));
+  if (stale.length > 0) {
+    await cache.remove(stale);
+  }
+
+  const total = ids.length;
+  cache.setSyncState({ phase: 'fetching', total, completed: 0, fetched: 0, bytes: 0 });
+
+  // Skip already-cached ids — bodies on disk are immutable per messageId.
+  const toFetch = ids.filter((id) => !cache.has(id));
+  const skipped = total - toFetch.length;
+  cache.setSyncState({ completed: skipped });
+
+  if (toFetch.length === 0) {
+    cache.setSyncState({
+      phase: 'done',
+      finishedAt: Date.now(),
+    });
+    return;
+  }
+
+  const chunkSize = Math.min(
+    FETCH_CHUNK_FALLBACK,
+    Math.max(1, jmapClient.getMaxObjectsInGet()),
+  );
+
+  let fetched = 0;
+  let bytes = 0;
+  let completed = skipped;
+
+  for (let i = 0; i < toFetch.length; i += chunkSize) {
+    if (useOfflineCacheStore.getState().consumeAbort()) {
+      cache.setSyncState({
+        phase: 'cancelled',
+        finishedAt: Date.now(),
+      });
+      return;
+    }
+
+    const chunk = toFetch.slice(i, i + chunkSize);
+    let emails: Email[];
+    try {
+      emails = await getFullEmails(chunk);
+    } catch (err) {
+      cache.setSyncState({
+        phase: 'error',
+        message: err instanceof Error ? err.message : 'Fetch failed',
+        finishedAt: Date.now(),
+      });
+      return;
+    }
+
+    for (const email of emails) {
+      const size = approxSize(email);
+      await cache.put(email, size);
+      fetched += 1;
+      bytes += size;
+      completed += 1;
+    }
+
+    // Some chunked ids may have been deleted server-side between query and
+    // fetch — they don't come back. Account for that in the completed count
+    // so the progress bar still finishes at 100%.
+    completed += chunk.length - emails.length;
+
+    cache.setSyncState({ completed, fetched, bytes });
+  }
+
+  cache.setSyncState({
+    phase: 'done',
+    completed: total,
+    fetched,
+    bytes,
+    finishedAt: Date.now(),
+  });
+}
+
+export function formatBytes(n: number): string {
+  if (n < 1024) return `${n} B`;
+  if (n < 1024 * 1024) return `${(n / 1024).toFixed(1)} KB`;
+  if (n < 1024 * 1024 * 1024) return `${(n / (1024 * 1024)).toFixed(1)} MB`;
+  return `${(n / (1024 * 1024 * 1024)).toFixed(2)} GB`;
+}

src/lib/push-background-task.ts

@@ -41,6 +41,7 @@ interface ShowNotificationOptions {
   emailId: string;
   threadId: string;
   subject?: string;
+  accountId: string;
 }
 
 interface BulwarkFcmNative {
@@ -100,6 +101,7 @@ export async function pushBackgroundTask(_data: unknown): Promise<void> {
       emailId,
       threadId: email.threadId,
       subject: email.subject ?? undefined,
+      accountId,
     });
 
     await AsyncStorage.setItem(LAST_NOTIFIED_EMAIL_ID_KEY, emailId);

src/lib/push-notifications.ts

@@ -327,6 +327,10 @@ export interface NotificationTapPayload {
   emailId: string;
   threadId: string;
   subject?: string;
+  // Identifies which logged-in account the notification was generated for.
+  // Optional for back-compat: older notifications already on the system tray
+  // won't carry this and will fall back to the active account on tap.
+  accountId?: string;
 }
 
 // Returns - and clears - any pending "notification tap" that launched the app

src/lib/sha256.ts

@@ -0,0 +1,131 @@
+// Minimal SHA-256 implementation. Used to verify APK update downloads against
+// the checksum published in the GitHub release body — the JS runtime has no
+// built-in `crypto.subtle.digest` and we don't currently depend on
+// `expo-crypto`. Public-domain algorithm (FIPS 180-4); typical sub-second per
+// MB on a modern phone, which is fine for the rare update flow.
+
+const K = new Uint32Array([
+  0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
+  0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
+  0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
+  0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+  0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
+  0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
+  0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
+  0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+  0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
+  0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
+  0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
+]);
+
+function rotr(x: number, n: number): number {
+  return (x >>> n) | (x << (32 - n));
+}
+
+export class Sha256 {
+  private h = new Uint32Array([
+    0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
+    0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19,
+  ]);
+  private buffer = new Uint8Array(64);
+  private bufferLen = 0;
+  private byteCount = 0;
+
+  update(bytes: Uint8Array): void {
+    let i = 0;
+    this.byteCount += bytes.length;
+    while (i < bytes.length) {
+      const room = 64 - this.bufferLen;
+      const chunk = Math.min(room, bytes.length - i);
+      this.buffer.set(bytes.subarray(i, i + chunk), this.bufferLen);
+      this.bufferLen += chunk;
+      i += chunk;
+      if (this.bufferLen === 64) {
+        this.process(this.buffer);
+        this.bufferLen = 0;
+      }
+    }
+  }
+
+  digestHex(): string {
+    // Final block: append 0x80, pad with zeros, then 8-byte big-endian length.
+    const totalBits = this.byteCount * 8;
+    this.buffer[this.bufferLen++] = 0x80;
+    if (this.bufferLen > 56) {
+      while (this.bufferLen < 64) this.buffer[this.bufferLen++] = 0;
+      this.process(this.buffer);
+      this.bufferLen = 0;
+    }
+    while (this.bufferLen < 56) this.buffer[this.bufferLen++] = 0;
+    // 64-bit length, big-endian. We can't represent >2^53 - JS bitops are
+    // 32-bit, so split into hi/lo words.
+    const hi = Math.floor(totalBits / 0x100000000);
+    const lo = totalBits >>> 0;
+    this.buffer[56] = (hi >>> 24) & 0xff;
+    this.buffer[57] = (hi >>> 16) & 0xff;
+    this.buffer[58] = (hi >>> 8) & 0xff;
+    this.buffer[59] = hi & 0xff;
+    this.buffer[60] = (lo >>> 24) & 0xff;
+    this.buffer[61] = (lo >>> 16) & 0xff;
+    this.buffer[62] = (lo >>> 8) & 0xff;
+    this.buffer[63] = lo & 0xff;
+    this.process(this.buffer);
+
+    let out = '';
+    for (let i = 0; i < 8; i++) {
+      out += this.h[i].toString(16).padStart(8, '0');
+    }
+    return out;
+  }
+
+  private process(block: Uint8Array): void {
+    const w = new Uint32Array(64);
+    for (let i = 0; i < 16; i++) {
+      w[i] =
+        (block[i * 4] << 24) |
+        (block[i * 4 + 1] << 16) |
+        (block[i * 4 + 2] << 8) |
+        block[i * 4 + 3];
+    }
+    for (let i = 16; i < 64; i++) {
+      const s0 = rotr(w[i - 15], 7) ^ rotr(w[i - 15], 18) ^ (w[i - 15] >>> 3);
+      const s1 = rotr(w[i - 2], 17) ^ rotr(w[i - 2], 19) ^ (w[i - 2] >>> 10);
+      w[i] = (w[i - 16] + s0 + w[i - 7] + s1) | 0;
+    }
+
+    let a = this.h[0], b = this.h[1], c = this.h[2], d = this.h[3];
+    let e = this.h[4], f = this.h[5], g = this.h[6], hh = this.h[7];
+
+    for (let i = 0; i < 64; i++) {
+      const S1 = rotr(e, 6) ^ rotr(e, 11) ^ rotr(e, 25);
+      const ch = (e & f) ^ (~e & g);
+      const temp1 = (hh + S1 + ch + K[i] + w[i]) | 0;
+      const S0 = rotr(a, 2) ^ rotr(a, 13) ^ rotr(a, 22);
+      const mj = (a & b) ^ (a & c) ^ (b & c);
+      const temp2 = (S0 + mj) | 0;
+      hh = g;
+      g = f;
+      f = e;
+      e = (d + temp1) | 0;
+      d = c;
+      c = b;
+      b = a;
+      a = (temp1 + temp2) | 0;
+    }
+
+    this.h[0] = (this.h[0] + a) | 0;
+    this.h[1] = (this.h[1] + b) | 0;
+    this.h[2] = (this.h[2] + c) | 0;
+    this.h[3] = (this.h[3] + d) | 0;
+    this.h[4] = (this.h[4] + e) | 0;
+    this.h[5] = (this.h[5] + f) | 0;
+    this.h[6] = (this.h[6] + g) | 0;
+    this.h[7] = (this.h[7] + hh) | 0;
+  }
+}
+
+export function sha256Hex(bytes: Uint8Array): string {
+  const h = new Sha256();
+  h.update(bytes);
+  return h.digestHex();
+}

src/screens/LoginScreen.tsx

@@ -1,12 +1,15 @@
 import React from 'react';
 import { View, Text, Pressable, StyleSheet, KeyboardAvoidingView, Platform, Image } from 'react-native';
 import { SafeAreaView } from 'react-native-safe-area-context';
+import Constants from 'expo-constants';
 import { Eye, EyeOff, X } from 'lucide-react-native';
 import { spacing, radius, typography, componentSizes, type ThemePalette } from '../theme/tokens';
 import { useColors } from '../theme/colors';
 import { Button, Input } from '../components';
 import { useAuthStore } from '../stores/auth-store';
 
+const APP_VERSION = Constants.expoConfig?.version ?? '0.0.0';
+
 interface LoginScreenProps {
   onLogin?: () => void;
   isAddMode?: boolean;
@@ -156,7 +159,7 @@ export default function LoginScreen({ onLogin, isAddMode, onCancel }: LoginScree
 
           {/* Footer */}
           <View style={styles.footer}>
-            <Text style={styles.footerText}>Bulwark Mobile v0.0.1</Text>
+            <Text style={styles.footerText}>Bulwark Mobile v{APP_VERSION}</Text>
             <Text style={styles.footerLink}>Privacy Policy</Text>
           </View>
         </View>

src/screens/SettingsScreen.tsx

@@ -210,14 +210,20 @@ export default function SettingsScreen({ onLogout, onBack, onTabSelect }: Settin
 
   return (
     <SafeAreaView style={styles.container} edges={['top']}>
-      {/* Header - matches webmail mobile: h-14, border-b, back button + icon + title */}
+      {/* Header - matches webmail mobile: h-14, border-b, back button + icon + title.
+          Settings is a tab root, so the back button is only rendered when a
+          parent passes onBack (it'd otherwise lead nowhere). */}
       <View style={styles.header}>
-        <Pressable
-          onPress={onBack}
-          style={({ pressed }) => [styles.headerBackBtn, pressed && styles.headerBackBtnPressed]}
-        >
-          <ArrowLeft size={20} color={c.text} />
-        </Pressable>
+        {onBack ? (
+          <Pressable
+            onPress={onBack}
+            style={({ pressed }) => [styles.headerBackBtn, pressed && styles.headerBackBtnPressed]}
+          >
+            <ArrowLeft size={20} color={c.text} />
+          </Pressable>
+        ) : (
+          <View style={styles.headerLeftSpacer} />
+        )}
         <Settings size={20} color={c.mutedForeground} />
         <Text style={styles.headerTitle}>{t('settings.title', 'Settings')}</Text>
       </View>
@@ -310,6 +316,7 @@ function makeStyles(c: ThemePalette) {
       borderRadius: radius.md,
     },
     headerBackBtnPressed: { backgroundColor: c.accent },
+    headerLeftSpacer: { width: spacing.sm },
     headerTitle: { ...typography.h3, color: c.text },
 
     scrollArea: { flex: 1 },

src/stores/__tests__/auth-store.test.ts

@@ -1,42 +1,62 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
 
-vi.mock('expo-secure-store', () => ({
-  setItemAsync: vi.fn(),
-  getItemAsync: vi.fn(),
-  deleteItemAsync: vi.fn(),
-}));
-
 vi.mock('../../api/jmap-client', () => ({
   jmapClient: {
     connect: vi.fn(),
     logout: vi.fn(),
     restoreSession: vi.fn(),
+    loadAccount: vi.fn(),
+    consumeLegacyCredentials: vi.fn(async () => null),
+    clearAccountCredentials: vi.fn(async () => undefined),
+    clearAllCredentials: vi.fn(async () => undefined),
+    reset: vi.fn(),
     accountId: 'acc-1',
     currentSession: { apiUrl: 'https://mail.example.com/jmap/' },
+    username: 'user',
+    serverUrl: 'https://mail.example.com',
   },
   AuthenticationError: class AuthenticationError extends Error {
     constructor(msg: string) { super(msg); this.name = 'AuthenticationError'; }
   },
+  NetworkError: class NetworkError extends Error {
+    constructor(msg: string) { super(msg); this.name = 'NetworkError'; }
+  },
+}));
+
+vi.mock('../../lib/push-notifications', () => ({
+  teardownPushNotifications: vi.fn(async () => undefined),
 }));
 
 import { jmapClient } from '../../api/jmap-client';
 import { useAuthStore } from '../auth-store';
+import { useAccountStore } from '../account-store';
 
 const mockConnect = jmapClient.connect as ReturnType<typeof vi.fn>;
 const mockLogout = jmapClient.logout as ReturnType<typeof vi.fn>;
-const mockRestore = jmapClient.restoreSession as ReturnType<typeof vi.fn>;
+const mockLoadAccount = jmapClient.loadAccount as ReturnType<typeof vi.fn>;
+
+function resetAccountStore(): void {
+  useAccountStore.setState({
+    accounts: [],
+    activeAccountId: null,
+    defaultAccountId: null,
+  });
+}
 
 beforeEach(() => {
   vi.clearAllMocks();
-  // Reset store state
+  resetAccountStore();
   useAuthStore.setState({
     isAuthenticated: false,
     isLoading: false,
+    hasRestoredSession: false,
     error: null,
     serverUrl: null,
     username: null,
     session: null,
     accountId: null,
+    activeAccountId: null,
+    client: null,
   });
 });
 
@@ -83,7 +103,7 @@ describe('auth-store', () => {
   });
 
   describe('logout', () => {
-    it('should reset all state', async () => {
+    it('should reset all state when no other accounts remain', async () => {
       useAuthStore.setState({ isAuthenticated: true, serverUrl: 'x', username: 'y' });
       mockLogout.mockResolvedValue(undefined);
 
@@ -97,23 +117,40 @@ describe('auth-store', () => {
   });
 
   describe('restoreSession', () => {
-    it('should restore on success', async () => {
-      mockRestore.mockResolvedValue(true);
+    it('should return false when there is no registered account', async () => {
+      const restored = await useAuthStore.getState().restoreSession();
+
+      expect(restored).toBe(false);
+      expect(useAuthStore.getState().isAuthenticated).toBe(false);
+      expect(useAuthStore.getState().hasRestoredSession).toBe(true);
+    });
+
+    it('should restore when loadAccount succeeds for the active account', async () => {
+      useAccountStore.setState({
+        accounts: [
+          {
+            id: 'acc-1',
+            serverUrl: 'https://mail.example.com',
+            username: 'user',
+            displayName: 'user',
+            email: 'user',
+            avatarColor: '#000',
+            lastLoginAt: 0,
+            isConnected: false,
+            hasError: false,
+            isDefault: true,
+          },
+        ],
+        activeAccountId: 'acc-1',
+        defaultAccountId: 'acc-1',
+      });
+      mockLoadAccount.mockResolvedValue(true);
 
       const restored = await useAuthStore.getState().restoreSession();
 
       expect(restored).toBe(true);
       expect(useAuthStore.getState().isAuthenticated).toBe(true);
     });
-
-    it('should return false when no session to restore', async () => {
-      mockRestore.mockResolvedValue(false);
-
-      const restored = await useAuthStore.getState().restoreSession();
-
-      expect(restored).toBe(false);
-      expect(useAuthStore.getState().isAuthenticated).toBe(false);
-    });
   });
 
   describe('clearError', () => {

src/stores/email-store.ts

@@ -1,7 +1,8 @@
 import { create } from 'zustand';
 import { persist, createJSONStorage } from 'zustand/middleware';
 import AsyncStorage from '@react-native-async-storage/async-storage';
-import type { Email, Mailbox } from '../api/types';
+import type { Email, Mailbox, StateChange } from '../api/types';
+import { jmapClient } from '../api/jmap-client';
 import {
   getMailboxes as fetchMailboxes,
   queryEmails,
@@ -16,6 +17,7 @@ import {
 } from '../api/email';
 import { toWildcardQuery } from '../lib/search-utils';
 import { useSettingsStore } from './settings-store';
+import { useOfflineCacheStore } from './offline-cache-store';
 
 export interface EmailFilters {
   from?: string;
@@ -56,6 +58,7 @@ export interface EmailState {
   selectMailbox: (mailboxId: string) => Promise<void>;
   loadMoreEmails: () => Promise<void>;
   refreshEmails: () => Promise<void>;
+  handleStateChange: (change: StateChange) => Promise<void>;
   getEmailDetail: (id: string) => Promise<Email>;
   markRead: (emailId: string) => Promise<void>;
   markUnread: (emailId: string) => Promise<void>;
@@ -149,15 +152,43 @@ export const useEmailStore = create<EmailState>()(
       filters: {},
       pendingUndo: null,
     });
+
+    // Seed from the offline cache immediately so changing folders shows
+    // something even before the network responds — and is the fallback
+    // when offline. The network result will replace this once it arrives.
+    const cacheStore = useOfflineCacheStore.getState();
+    if (!cacheStore.hydrated) await cacheStore.hydrate();
+    const limit = useSettingsStore.getState().emailsPerPage;
+    let cached: Email[] = [];
+    if (cacheStore.totalCount() > 0) {
+      try {
+        cached = await cacheStore.getEmailsInMailbox(mailboxId, Math.max(limit, 50));
+        if (cached.length > 0 && get().currentMailboxId === mailboxId) {
+          set({ emails: cached, totalEmails: cached.length });
+        }
+      } catch (err) {
+        console.warn('[email-store] cache seed failed:', err);
+      }
+    }
+
     try {
       const filter = buildJmapFilter(mailboxId, '', {});
-      const limit = useSettingsStore.getState().emailsPerPage;
       const { ids, total } = await queryEmails(mailboxId, { limit, filter });
       const emails = ids.length > 0 ? await fetchEmails(ids) : [];
+      // Race guard: don't overwrite if the user already moved to a different
+      // mailbox while this request was in flight.
+      if (get().currentMailboxId !== mailboxId) return;
       set({ emails, totalEmails: total, loading: false });
     } catch (err) {
       console.warn('[email-store] selectMailbox failed:', err);
-      set({ loading: false, error: err instanceof Error ? err.message : 'Failed to load emails' });
+      if (get().currentMailboxId !== mailboxId) return;
+      // Keep whatever the cache seeded with; only surface the error when the
+      // cache is empty. With cached emails visible the OfflineBanner already
+      // tells the user the data is stale.
+      set({
+        loading: false,
+        error: cached.length > 0 ? null : (err instanceof Error ? err.message : 'Failed to load emails'),
+      });
     }
   },
 
@@ -182,7 +213,7 @@ export const useEmailStore = create<EmailState>()(
   },
 
   refreshEmails: async () => {
-    const { currentMailboxId, searchQuery, filters } = get();
+    const { currentMailboxId, searchQuery, filters, emails: existing } = get();
     if (!currentMailboxId) return;
     // Keep existing emails visible while refreshing - swap atomically once
     // the new list is ready so pull-to-refresh doesn't flash an empty list.
@@ -195,10 +226,50 @@ export const useEmailStore = create<EmailState>()(
       set({ emails, totalEmails: total, loading: false });
     } catch (err) {
       console.warn('[email-store] refreshEmails failed:', err);
+      // If the list was empty before the refresh attempt, fall back to the
+      // offline cache so the user still sees something. Otherwise keep what
+      // they had visible and let the OfflineBanner explain.
+      if (existing.length === 0) {
+        try {
+          const cacheStore = useOfflineCacheStore.getState();
+          if (!cacheStore.hydrated) await cacheStore.hydrate();
+          if (cacheStore.totalCount() > 0) {
+            const limit = useSettingsStore.getState().emailsPerPage;
+            const cached = await cacheStore.getEmailsInMailbox(
+              currentMailboxId,
+              Math.max(limit, 50),
+            );
+            if (get().currentMailboxId === currentMailboxId && cached.length > 0) {
+              set({ emails: cached, totalEmails: cached.length, loading: false, error: null });
+              return;
+            }
+          }
+        } catch (cacheErr) {
+          console.warn('[email-store] refresh cache fallback failed:', cacheErr);
+        }
+      }
       set({ loading: false, error: err instanceof Error ? err.message : 'Failed to load emails' });
     }
   },
 
+  handleStateChange: async (change) => {
+    if (!jmapClient.currentSession) return;
+    const accountId = jmapClient.accountId;
+    const accountChanges = change.changed?.[accountId];
+    if (!accountChanges) return;
+
+    const mailboxChanged = 'Mailbox' in accountChanges;
+    const emailChanged = 'Email' in accountChanges || 'EmailDelivery' in accountChanges;
+    if (!mailboxChanged && !emailChanged) return;
+
+    if (mailboxChanged) {
+      await get().fetchMailboxes();
+    }
+    if (emailChanged && get().currentMailboxId) {
+      await get().refreshEmails();
+    }
+  },
+
   setSearchQuery: (query) => {
     set({ searchQuery: query });
     void get().refreshEmails();
@@ -217,7 +288,27 @@ export const useEmailStore = create<EmailState>()(
   },
 
   getEmailDetail: async (id) => {
-    return getFullEmail(id);
+    // Try the network first so the user sees fresh keywords/flags. If that
+    // fails (offline / server unreachable), fall back to the offline cache
+    // when the message is in it. Without the cache hit, propagate the error
+    // so the caller can surface it.
+    try {
+      const fresh = await getFullEmail(id);
+      // Opportunistically refresh the cached copy so the next offline open
+      // reflects the latest keywords without needing a full sync.
+      const cache = useOfflineCacheStore.getState();
+      if (cache.has(id)) {
+        try {
+          const size = JSON.stringify(fresh).length;
+          await cache.put(fresh, size);
+        } catch { /* ignore — best-effort refresh */ }
+      }
+      return fresh;
+    } catch (err) {
+      const cached = await useOfflineCacheStore.getState().get(id);
+      if (cached) return cached;
+      throw err;
+    }
   },
 
   markRead: async (emailId) => {

src/stores/offline-cache-store.ts

@@ -0,0 +1,207 @@
+// Persistent cache for full email bodies (and optional attachment blobs)
+// powering offline mail viewing. Bodies are JSON-serialised and kept in
+// AsyncStorage; attachment blobs go to expo-file-system under
+// `Paths.document/offline-attachments/`. The store also exposes the live
+// progress state the OfflineCacheBanner reads from.
+
+import { create } from 'zustand';
+import AsyncStorage from '@react-native-async-storage/async-storage';
+import type { Email } from '../api/types';
+
+const INDEX_KEY = 'webmail:offline-cache:index:v1';
+const ENTRY_KEY_PREFIX = 'webmail:offline-cache:entry:v1:';
+
+function entryKey(id: string): string {
+  return `${ENTRY_KEY_PREFIX}${id}`;
+}
+
+export interface OfflineCacheIndexEntry {
+  id: string;
+  receivedAt: string;
+  size: number;          // approx bytes of cached payload
+  cachedAt: number;
+}
+
+interface CacheIndex {
+  // Per-account is keyed at the storage layer (one app session = one account
+  // active at a time). Cross-account separation is left to a future change.
+  entries: Record<string, OfflineCacheIndexEntry>;
+}
+
+export type SyncPhase = 'idle' | 'scanning' | 'fetching' | 'done' | 'error' | 'cancelled';
+
+export interface SyncState {
+  phase: SyncPhase;
+  total: number;       // total emails the sync expects to process
+  completed: number;   // emails processed (skipped or fetched)
+  fetched: number;     // emails actually downloaded (not already cached)
+  bytes: number;       // bytes downloaded this run
+  message?: string;    // human-readable status (errors etc.)
+  startedAt?: number;
+  finishedAt?: number;
+}
+
+const IDLE: SyncState = { phase: 'idle', total: 0, completed: 0, fetched: 0, bytes: 0 };
+
+interface OfflineCacheState {
+  index: CacheIndex;
+  hydrated: boolean;
+  sync: SyncState;
+  // Allows the sync orchestrator to abort mid-run when the user disables the
+  // setting or kicks off a fresh sync. Stored on the singleton because
+  // AbortControllers need to survive across the function boundary.
+  abortRequested: boolean;
+
+  hydrate: () => Promise<void>;
+  has: (id: string) => boolean;
+  get: (id: string) => Promise<Email | null>;
+  put: (email: Email, approxBytes: number) => Promise<void>;
+  remove: (ids: string[]) => Promise<void>;
+  clearAll: () => Promise<void>;
+
+  // Returns cached emails whose `mailboxIds` include the given mailbox,
+  // sorted by `receivedAt` descending. Used by selectMailbox to seed the
+  // list when the network is unavailable. Loads each entry from
+  // AsyncStorage; the index doesn't carry the mailbox set.
+  getEmailsInMailbox: (mailboxId: string, limit?: number) => Promise<Email[]>;
+
+  totalSize: () => number;
+  totalCount: () => number;
+
+  setSyncState: (next: Partial<SyncState>) => void;
+  resetSync: () => void;
+  requestAbort: () => void;
+  consumeAbort: () => boolean;
+}
+
+function persistIndex(index: CacheIndex): void {
+  void AsyncStorage.setItem(INDEX_KEY, JSON.stringify(index)).catch((err) => {
+    console.warn('[offline-cache] persist index failed', err);
+  });
+}
+
+export const useOfflineCacheStore = create<OfflineCacheState>((set, get) => ({
+  index: { entries: {} },
+  hydrated: false,
+  sync: { ...IDLE },
+  abortRequested: false,
+
+  hydrate: async () => {
+    if (get().hydrated) return;
+    try {
+      const raw = await AsyncStorage.getItem(INDEX_KEY);
+      if (raw) {
+        const parsed = JSON.parse(raw) as CacheIndex;
+        if (parsed && typeof parsed === 'object' && parsed.entries) {
+          set({ index: parsed, hydrated: true });
+          return;
+        }
+      }
+    } catch (err) {
+      console.warn('[offline-cache] hydrate failed', err);
+    }
+    set({ hydrated: true });
+  },
+
+  has: (id) => Boolean(get().index.entries[id]),
+
+  get: async (id) => {
+    if (!get().index.entries[id]) return null;
+    try {
+      const raw = await AsyncStorage.getItem(entryKey(id));
+      if (!raw) return null;
+      return JSON.parse(raw) as Email;
+    } catch (err) {
+      console.warn('[offline-cache] get failed', id, err);
+      return null;
+    }
+  },
+
+  put: async (email, approxBytes) => {
+    try {
+      await AsyncStorage.setItem(entryKey(email.id), JSON.stringify(email));
+    } catch (err) {
+      console.warn('[offline-cache] put failed', email.id, err);
+      return;
+    }
+    const nextEntries = {
+      ...get().index.entries,
+      [email.id]: {
+        id: email.id,
+        receivedAt: email.receivedAt,
+        size: approxBytes,
+        cachedAt: Date.now(),
+      },
+    };
+    const index = { entries: nextEntries };
+    set({ index });
+    persistIndex(index);
+  },
+
+  remove: async (ids) => {
+    if (ids.length === 0) return;
+    await Promise.all(
+      ids.map((id) => AsyncStorage.removeItem(entryKey(id)).catch(() => undefined)),
+    );
+    const next = { ...get().index.entries };
+    for (const id of ids) delete next[id];
+    const index = { entries: next };
+    set({ index });
+    persistIndex(index);
+  },
+
+  clearAll: async () => {
+    const ids = Object.keys(get().index.entries);
+    await Promise.all(
+      ids.map((id) => AsyncStorage.removeItem(entryKey(id)).catch(() => undefined)),
+    );
+    const index = { entries: {} };
+    set({ index, sync: { ...IDLE } });
+    persistIndex(index);
+  },
+
+  getEmailsInMailbox: async (mailboxId, limit = 200) => {
+    // Sort the index by receivedAt descending first so we don't have to read
+    // entries we won't return — the index already carries receivedAt.
+    const sorted = Object.values(get().index.entries).sort((a, b) => {
+      const at = a.receivedAt ? new Date(a.receivedAt).getTime() : 0;
+      const bt = b.receivedAt ? new Date(b.receivedAt).getTime() : 0;
+      return bt - at;
+    });
+    const matches: Email[] = [];
+    for (const entry of sorted) {
+      if (matches.length >= limit) break;
+      try {
+        const raw = await AsyncStorage.getItem(entryKey(entry.id));
+        if (!raw) continue;
+        const email = JSON.parse(raw) as Email;
+        if (email.mailboxIds?.[mailboxId]) {
+          matches.push(email);
+        }
+      } catch {
+        // skip corrupt entries — they'll be replaced on next sync
+      }
+    }
+    return matches;
+  },
+
+  totalSize: () => {
+    let n = 0;
+    for (const e of Object.values(get().index.entries)) n += e.size;
+    return n;
+  },
+
+  totalCount: () => Object.keys(get().index.entries).length,
+
+  setSyncState: (next) => set({ sync: { ...get().sync, ...next } }),
+
+  resetSync: () => set({ sync: { ...IDLE }, abortRequested: false }),
+
+  requestAbort: () => set({ abortRequested: true }),
+
+  consumeAbort: () => {
+    const v = get().abortRequested;
+    if (v) set({ abortRequested: false });
+    return v;
+  },
+}));

src/stores/settings-store.ts

@@ -131,6 +131,13 @@ interface PersistedSettings {
 
   // Plugins (UI-level enable map)
   pluginEnabled: Record<string, boolean>;
+
+  // Offline mail cache: download recent message bodies in the background so
+  // they can be opened without network. Days windows the lookback. Attachment
+  // caching is intentionally not implemented yet — bodies-only is much
+  // smaller and covers the "open recent mail offline" UX on its own.
+  offlineCacheEnabled: boolean;
+  offlineCacheDays: number;
 }
 
 const DEFAULT_PERSISTED: PersistedSettings = {
@@ -207,6 +214,9 @@ const DEFAULT_PERSISTED: PersistedSettings = {
   filtersExpandedView: false,
 
   pluginEnabled: {},
+
+  offlineCacheEnabled: false,
+  offlineCacheDays: 7,
 };
 
 export interface SettingsState extends PersistedSettings {

src/stores/updates-store.ts

@@ -108,9 +108,15 @@ export const useUpdatesStore = create<UpdatesState>((set, get) => ({
     if (s.installing || !s.cachedLatest?.apkAsset) return;
     set({ installing: true, error: null, installProgress: { phase: 'downloading', progress: 0 } });
     try {
-      await downloadAndInstallApk(s.cachedLatest.apkAsset, (p) => {
-        set({ installProgress: p });
-      });
+      await downloadAndInstallApk(
+        {
+          asset: s.cachedLatest.apkAsset,
+          expectedSha256: s.cachedLatest.apkSha256,
+        },
+        (p) => {
+          set({ installProgress: p });
+        },
+      );
       set({ installing: false, installProgress: null });
     } catch (err) {
       set({

src/test-setup.ts

@@ -0,0 +1,66 @@
+// Vitest setup. Two pieces of plumbing the unit tests need:
+//
+// 1. AsyncStorage: the Zustand `persist` middleware used by several stores
+//    reaches in during `set()` calls, which on a `node` environment crashes
+//    inside the RN AsyncStorage shim (no `window` global). Swap in an
+//    in-memory implementation.
+// 2. react-native: the bundled entry point is Flow-typed and rolldown can't
+//    parse it. Stub the few surfaces used at module-load time so any store
+//    that transitively imports `react-native` (via push / client-cert
+//    bridges) loads cleanly. Tests that actually exercise native modules
+//    re-mock the relevant module locally.
+
+import { vi } from 'vitest';
+
+const memory = new Map<string, string>();
+
+vi.mock('@react-native-async-storage/async-storage', () => ({
+  default: {
+    getItem: vi.fn(async (key: string) => memory.get(key) ?? null),
+    setItem: vi.fn(async (key: string, value: string) => {
+      memory.set(key, value);
+    }),
+    removeItem: vi.fn(async (key: string) => {
+      memory.delete(key);
+    }),
+    clear: vi.fn(async () => {
+      memory.clear();
+    }),
+    getAllKeys: vi.fn(async () => Array.from(memory.keys())),
+    multiGet: vi.fn(async (keys: string[]) =>
+      keys.map((k) => [k, memory.get(k) ?? null] as [string, string | null]),
+    ),
+    multiSet: vi.fn(async (pairs: [string, string][]) => {
+      for (const [k, v] of pairs) memory.set(k, v);
+    }),
+    multiRemove: vi.fn(async (keys: string[]) => {
+      for (const k of keys) memory.delete(k);
+    }),
+  },
+}));
+
+vi.mock('react-native', () => {
+  class NativeEventEmitter {
+    addListener() {
+      return { remove: () => undefined };
+    }
+    removeAllListeners() {}
+  }
+  return {
+    Platform: { OS: 'android', Version: 33, select: <T,>(spec: { default?: T; android?: T; ios?: T }) => spec.android ?? spec.default ?? spec.ios },
+    NativeModules: {},
+    NativeEventEmitter,
+    PermissionsAndroid: {
+      RESULTS: { GRANTED: 'granted', DENIED: 'denied', NEVER_ASK_AGAIN: 'never_ask_again' },
+      request: async () => 'granted',
+    },
+    Linking: { openURL: async () => undefined },
+    Appearance: { getColorScheme: () => 'dark', addChangeListener: () => ({ remove: () => undefined }) },
+  };
+});
+
+vi.mock('expo-secure-store', () => ({
+  setItemAsync: vi.fn(async () => undefined),
+  getItemAsync: vi.fn(async () => null),
+  deleteItemAsync: vi.fn(async () => undefined),
+}));

vitest.config.ts

@@ -5,5 +5,6 @@ export default defineConfig({
     globals: true,
     environment: 'node',
     include: ['src/**/__tests__/**/*.test.ts'],
+    setupFiles: ['src/test-setup.ts'],
   },
 });