fix auth flows

apps/weblibre/lib/features/app_links/domain/services/app_link_policy_replication.dart

@@ -110,6 +110,7 @@ AppLinkPolicySnapshot? appLinkPolicySnapshot(Ref ref) {
         key: _toNativeRule(value),
     },
     marketplaceFallbackEnabled: settings.appLinkMarketplaceFallback,
+    authExceptionsEnabled: settings.appLinkAuthExceptionsEnabled,
     protectGeneralContext: protection.protectGeneralContext,
     protectedContextIds: protection.protectedContextIds.toList(),
     strictContextIds: protection.strictContextIds.toList(),

apps/weblibre/lib/features/app_links/domain/services/app_link_policy_replication.g.dart

@@ -120,7 +120,7 @@ final class AppLinkPolicySnapshotProvider
 }
 
 String _$appLinkPolicySnapshotHash() =>
-    r'6fe2dca118d7162561fc7f6280d1a0411d50972a';
+    r'4d456a3cbf091e95ac35d913e8fa20d5f25978ab';
 
 /// Single serialised writer that mirrors the Dart-owned app-link policy to the
 /// native profile-scoped store (§2.8), the sole policy source consulted by the

apps/weblibre/lib/features/geckoview/domain/repositories/tab.g.dart

@@ -41,7 +41,7 @@ final class TabRepositoryProvider
   }
 }
 
-String _$tabRepositoryHash() => r'797520166026d1f0272cf713aa1c25ecf129c236';
+String _$tabRepositoryHash() => r'5824be32664bac24623cf8863f68b7afa254d025';
 
 abstract class _$TabRepository extends $Notifier<void> {
   void build();

apps/weblibre/lib/features/geckoview/features/browser/domain/providers.g.dart

@@ -1397,8 +1397,8 @@ final class VisibleTabListItemsFamily extends $Family
 /// switcher lays them out — the unassigned bucket first, then containers by
 /// pinned/`order_key`. Stepping off the end of one container therefore
 /// continues into the next, and selecting that tab moves the selected container
-/// along with it. Containers without tabs are skipped so their tree query never
+/// along with it. Named containers holding no tabs are skipped so their tree
-/// runs.
+/// query never runs.
 ///
 /// "Previous" is a step towards the top of that order and "next" a step
 /// towards its end, so direction follows `tabListDirection` (baked into the
@@ -1443,8 +1443,8 @@ final sequentialTabNavigationOrderProvider =
 /// switcher lays them out — the unassigned bucket first, then containers by
 /// pinned/`order_key`. Stepping off the end of one container therefore
 /// continues into the next, and selecting that tab moves the selected container
-/// along with it. Containers without tabs are skipped so their tree query never
+/// along with it. Named containers holding no tabs are skipped so their tree
-/// runs.
+/// query never runs.
 ///
 /// "Previous" is a step towards the top of that order and "next" a step
 /// towards its end, so direction follows `tabListDirection` (baked into the
@@ -1493,8 +1493,8 @@ final class SequentialTabNavigationOrderProvider
   /// switcher lays them out — the unassigned bucket first, then containers by
   /// pinned/`order_key`. Stepping off the end of one container therefore
   /// continues into the next, and selecting that tab moves the selected container
-  /// along with it. Containers without tabs are skipped so their tree query never
+  /// along with it. Named containers holding no tabs are skipped so their tree
-  /// runs.
+  /// query never runs.
   ///
   /// "Previous" is a step towards the top of that order and "next" a step
   /// towards its end, so direction follows `tabListDirection` (baked into the

apps/weblibre/lib/features/settings/presentation/screens/browsing_settings.dart

@@ -817,6 +817,11 @@ class _AppLinksModeSection extends HookConsumerWidget {
         (s) => s.appLinkMarketplaceFallback,
       ),
     );
+    final authExceptionsEnabled = ref.watch(
+      generalSettingsWithDefaultsProvider.select(
+        (s) => s.appLinkAuthExceptionsEnabled,
+      ),
+    );
     final rules = ref.watch(
       generalSettingsWithDefaultsProvider.select((s) => s.appLinkRules),
     );
@@ -887,6 +892,23 @@ class _AppLinksModeSection extends HookConsumerWidget {
                         );
                   },
           ),
+          SwitchListTile.adaptive(
+            contentPadding: EdgeInsets.zero,
+            title: const Text('Allow login app callbacks'),
+            subtitle: const Text(
+              'Let apps that opened a Custom Tab receive their login callback, '
+              'even when links are set to never open in apps',
+            ),
+            value: authExceptionsEnabled,
+            onChanged: (value) async {
+              await ref
+                  .read(saveGeneralSettingsControllerProvider.notifier)
+                  .save(
+                    (current) =>
+                        current.copyWith.appLinkAuthExceptionsEnabled(value),
+                  );
+            },
+          ),
           _AppLinkRulesSubsection(rules: rules),
         ],
       ),

apps/weblibre/lib/features/user/data/models/general_settings.dart

@@ -252,6 +252,12 @@ class GeneralSettings with FastEquatable {
   /// Defaults to false — the wrong default for a de-Googled browser.
   final bool appLinkMarketplaceFallback;
 
+  /// Whether app-link "never" rules allow a same-caller Custom Tab / ActionView
+  /// login callback to return to the app that opened the browser. Defaults to
+  /// true to keep OAuth-style sign-in flows working while normal app links still
+  /// obey [appLinksMode].
+  final bool appLinkAuthExceptionsEnabled;
+
   /// Whether the local search index (`history` table populated via tab→
   /// history triggers) is active. When false, the SQL trigger guard returns
   /// without writing; existing rows stay until the user clears them.
@@ -359,6 +365,7 @@ class GeneralSettings with FastEquatable {
     required this.appLinkRules,
     required this.appLinkContextOverrides,
     required this.appLinkMarketplaceFallback,
+    required this.appLinkAuthExceptionsEnabled,
     required this.enableLocalSearchIndex,
     required this.indexPrivateTabs,
     required this.acceptSuggestionOnSubmit,
@@ -436,6 +443,7 @@ class GeneralSettings with FastEquatable {
     Map<String, PersistedAppLinkRule>? appLinkRules,
     Map<String, ContextAppLinkPolicy>? appLinkContextOverrides,
     bool? appLinkMarketplaceFallback,
+    bool? appLinkAuthExceptionsEnabled,
     bool? enableLocalSearchIndex,
     bool? indexPrivateTabs,
     bool? acceptSuggestionOnSubmit,
@@ -524,6 +532,7 @@ class GeneralSettings with FastEquatable {
        appLinkRules = appLinkRules ?? const {},
        appLinkContextOverrides = appLinkContextOverrides ?? const {},
        appLinkMarketplaceFallback = appLinkMarketplaceFallback ?? false,
+       appLinkAuthExceptionsEnabled = appLinkAuthExceptionsEnabled ?? true,
        enableLocalSearchIndex = enableLocalSearchIndex ?? true,
        indexPrivateTabs = indexPrivateTabs ?? false,
        acceptSuggestionOnSubmit = acceptSuggestionOnSubmit ?? true,
@@ -693,6 +702,7 @@ class GeneralSettings with FastEquatable {
     appLinkRules,
     appLinkContextOverrides,
     appLinkMarketplaceFallback,
+    appLinkAuthExceptionsEnabled,
     enableLocalSearchIndex,
     indexPrivateTabs,
     acceptSuggestionOnSubmit,

apps/weblibre/lib/features/user/data/models/general_settings.g.dart

@@ -161,6 +161,10 @@ abstract class _$GeneralSettingsCWProxy {
 
   GeneralSettings appLinkMarketplaceFallback(bool appLinkMarketplaceFallback);
 
+  GeneralSettings appLinkAuthExceptionsEnabled(
+    bool appLinkAuthExceptionsEnabled,
+  );
+
   GeneralSettings enableLocalSearchIndex(bool enableLocalSearchIndex);
 
   GeneralSettings indexPrivateTabs(bool indexPrivateTabs);
@@ -253,6 +257,7 @@ abstract class _$GeneralSettingsCWProxy {
     Map<String, PersistedAppLinkRule> appLinkRules,
     Map<String, ContextAppLinkPolicy> appLinkContextOverrides,
     bool appLinkMarketplaceFallback,
+    bool appLinkAuthExceptionsEnabled,
     bool enableLocalSearchIndex,
     bool indexPrivateTabs,
     bool acceptSuggestionOnSubmit,
@@ -556,6 +561,11 @@ class _$GeneralSettingsCWProxyImpl implements _$GeneralSettingsCWProxy {
   GeneralSettings appLinkMarketplaceFallback(bool appLinkMarketplaceFallback) =>
       call(appLinkMarketplaceFallback: appLinkMarketplaceFallback);
 
+  @override
+  GeneralSettings appLinkAuthExceptionsEnabled(
+    bool appLinkAuthExceptionsEnabled,
+  ) => call(appLinkAuthExceptionsEnabled: appLinkAuthExceptionsEnabled);
+
   @override
   GeneralSettings enableLocalSearchIndex(bool enableLocalSearchIndex) =>
       call(enableLocalSearchIndex: enableLocalSearchIndex);
@@ -665,6 +675,7 @@ class _$GeneralSettingsCWProxyImpl implements _$GeneralSettingsCWProxy {
     Object? appLinkRules = const $CopyWithPlaceholder(),
     Object? appLinkContextOverrides = const $CopyWithPlaceholder(),
     Object? appLinkMarketplaceFallback = const $CopyWithPlaceholder(),
+    Object? appLinkAuthExceptionsEnabled = const $CopyWithPlaceholder(),
     Object? enableLocalSearchIndex = const $CopyWithPlaceholder(),
     Object? indexPrivateTabs = const $CopyWithPlaceholder(),
     Object? acceptSuggestionOnSubmit = const $CopyWithPlaceholder(),
@@ -1061,6 +1072,12 @@ class _$GeneralSettingsCWProxyImpl implements _$GeneralSettingsCWProxy {
           ? _value.appLinkMarketplaceFallback
           // ignore: cast_nullable_to_non_nullable
           : appLinkMarketplaceFallback as bool,
+      appLinkAuthExceptionsEnabled:
+          appLinkAuthExceptionsEnabled == const $CopyWithPlaceholder() ||
+              appLinkAuthExceptionsEnabled == null
+          ? _value.appLinkAuthExceptionsEnabled
+          // ignore: cast_nullable_to_non_nullable
+          : appLinkAuthExceptionsEnabled as bool,
       enableLocalSearchIndex:
           enableLocalSearchIndex == const $CopyWithPlaceholder() ||
               enableLocalSearchIndex == null
@@ -1257,6 +1274,7 @@ GeneralSettings _$GeneralSettingsFromJson(
     json['appLinkContextOverrides'] as Map<String, dynamic>?,
   ),
   appLinkMarketplaceFallback: json['appLinkMarketplaceFallback'] as bool?,
+  appLinkAuthExceptionsEnabled: json['appLinkAuthExceptionsEnabled'] as bool?,
   enableLocalSearchIndex: json['enableLocalSearchIndex'] as bool?,
   indexPrivateTabs: json['indexPrivateTabs'] as bool?,
   acceptSuggestionOnSubmit: json['acceptSuggestionOnSubmit'] as bool?,
@@ -1356,6 +1374,7 @@ Map<String, dynamic> _$GeneralSettingsToJson(
     (k, e) => MapEntry(k, e.toJson()),
   ),
   'appLinkMarketplaceFallback': instance.appLinkMarketplaceFallback,
+  'appLinkAuthExceptionsEnabled': instance.appLinkAuthExceptionsEnabled,
   'enableLocalSearchIndex': instance.enableLocalSearchIndex,
   'indexPrivateTabs': instance.indexPrivateTabs,
   'acceptSuggestionOnSubmit': instance.acceptSuggestionOnSubmit,

apps/weblibre/lib/features/user/domain/repositories/general_settings.dart

@@ -109,6 +109,7 @@ const generalSettingColumnTypes = <String, DriftSqlType>{
   'customTabsEnabled': DriftSqlType.bool,
   'appLinksMode': DriftSqlType.string,
   'appLinkMarketplaceFallback': DriftSqlType.bool,
+  'appLinkAuthExceptionsEnabled': DriftSqlType.bool,
   'enableLocalSearchIndex': DriftSqlType.bool,
   'indexPrivateTabs': DriftSqlType.bool,
   'acceptSuggestionOnSubmit': DriftSqlType.bool,

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/activities/AuthIntentReceiverActivity.kt

@@ -19,6 +19,10 @@ class AuthIntentReceiverActivity : Activity() {
 
         val sourceIntent = intent?.let { Intent(it) } ?: Intent()
 
+        // Stamp the caller before CustomTabIntentProcessor builds the session source, so the
+        // app-links authentication carve-out can recognise a sign-in callback for this tab.
+        addExternalCallerInformation(sourceIntent)
+
         if (GlobalComponents.components == null && !GlobalComponents.ensureExternalComponents(applicationContext)) {
             finish()
             return

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/activities/ExternalCallerInfo.kt

@@ -0,0 +1,83 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package eu.weblibre.flutter_mozilla_components.activities
+
+import android.app.Activity
+import android.content.Intent
+import android.content.pm.PackageManager
+import android.net.Uri
+import android.os.Build
+import mozilla.components.support.utils.EXTRA_ACTIVITY_REFERRER_CATEGORY
+import mozilla.components.support.utils.EXTRA_ACTIVITY_REFERRER_PACKAGE
+import mozilla.components.support.utils.ext.packageManagerCompatHelper
+
+/**
+ * Records which app sent [intent] so the session created from it carries a `caller`.
+ *
+ * AC's `CustomTabIntentProcessor` reads the caller through `SafeIntent.externalPackage()`, which
+ * only looks at the [EXTRA_ACTIVITY_REFERRER_PACKAGE] extra — nothing populates it for us, so a
+ * receiver has to stamp it before handing the intent to the processors or every custom tab ends up
+ * with `Source.External.CustomTab(null)`. Mirrors Fenix's `IntentReceiverActivity`
+ * `addReferrerInformation`.
+ *
+ * The app-links authentication carve-out
+ * ([eu.weblibre.flutter_mozilla_components.applinks.WebLibreAppLinksInterceptor]) is the consumer:
+ * it lets a sign-in callback return to the app that opened the tab.
+ */
+fun Activity.addExternalCallerInformation(intent: Intent) {
+    val caller = resolveExternalCallerPackage(intent) ?: return
+    intent.putExtra(EXTRA_ACTIVITY_REFERRER_PACKAGE, caller)
+
+    // ApplicationInfo.category is API 26+; this module builds against minSdk 24.
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+        try {
+            val category = packageManagerCompatHelper.getApplicationInfoCompat(caller, 0).category
+            intent.putExtra(EXTRA_ACTIVITY_REFERRER_CATEGORY, category)
+        } catch (e: PackageManager.NameNotFoundException) {
+            // The caller is not resolvable — the package id alone is enough for our purposes.
+        }
+    }
+}
+
+/**
+ * Best-effort identity of the app that sent [intent].
+ *
+ * [Activity.getCallingPackage] is supplied by the system and cannot be forged, so it wins when
+ * present (only set for `startActivityForResult` callers). The referrer chain below is
+ * caller-controlled and therefore spoofable — an app can claim to be another package. Consumers
+ * must not grant anything on it that the caller could not already do itself.
+ */
+@Suppress("TooGenericExceptionCaught")
+fun Activity.resolveExternalCallerPackage(intent: Intent): String? {
+    callingPackage?.let { return it }
+
+    // Android can throw when the referrer carries data it cannot deserialise.
+    val activityReferrer = try {
+        referrer
+    } catch (e: RuntimeException) {
+        null
+    }
+    activityReferrer?.let { uri ->
+        if (uri.scheme == ANDROID_APP_SCHEME) {
+            uri.host?.let { return it }
+        }
+    }
+
+    @Suppress("DEPRECATION")
+    val referrerUri: Uri? = intent.getParcelableExtra(Intent.EXTRA_REFERRER)
+    if (referrerUri?.scheme == ANDROID_APP_SCHEME) {
+        referrerUri.host?.let { return it }
+    }
+
+    intent.getStringExtra(Intent.EXTRA_REFERRER_NAME)?.let { name ->
+        Uri.parse(name).takeIf { it.scheme == ANDROID_APP_SCHEME }?.host?.let { return it }
+    }
+
+    return null
+}
+
+private const val ANDROID_APP_SCHEME = "android-app"

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/activities/IntentReceiverActivity.kt

@@ -93,7 +93,7 @@ class IntentReceiverActivity : Activity() {
             }
         }
 
-        val caller = resolveCallerPackage(intent) ?: return false
+        val caller = resolveExternalCallerPackage(intent) ?: return false
         if (caller == packageName) return false
         if (!IntentGatekeeperPreferences.isBlocked(applicationContext, caller)) return false
 
@@ -102,32 +102,17 @@ class IntentReceiverActivity : Activity() {
         return true
     }
 
-    private fun resolveCallerPackage(intent: Intent): String? {
-        referrer?.let { uri ->
-            if (uri.scheme == "android-app") {
-                uri.host?.let { return it }
-            }
-        }
-
-        @Suppress("DEPRECATION")
-        val referrerUri: Uri? = intent.getParcelableExtra(Intent.EXTRA_REFERRER)
-        if (referrerUri?.scheme == "android-app") {
-            referrerUri.host?.let { return it }
-        }
-
-        intent.getStringExtra(Intent.EXTRA_REFERRER_NAME)?.let { name ->
-            Uri.parse(name).takeIf { it.scheme == "android-app" }?.host?.let { return it }
-        }
-
-        return callingPackage
-    }
-
     override fun onDestroy() {
         super.onDestroy()
         coroutineScope.cancel()
     }
 
     private fun processIntent(intent: Intent) {
+        // Must run before any intent processor: CustomTabIntentProcessor reads the caller off the
+        // intent when it builds the session source, and the app-links authentication carve-out
+        // needs that caller to recognise a sign-in callback.
+        addExternalCallerInformation(intent)
+
         if (GlobalComponents.components == null) {
             if (GlobalComponents.ensureExternalComponents(applicationContext)) {
                 routeIntent(intent)

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/applinks/AppLinkClassifier.kt

@@ -57,6 +57,7 @@ data class AppLinkPolicy(
     val protectedContextIds: Set<String>,
     val strictContextIds: Set<String>,
     val protectedTargetPatterns: List<ProtectedTargetPattern>,
+    val authExceptionsEnabled: Boolean,
     /**
      * Per-container overrides keyed by contextId; only isolated containers appear. A navigation whose
      * source contextId is a key uses the entry's mode + rules instead of the global ones (replace).
@@ -72,6 +73,7 @@ data class AppLinkPolicy(
             protectedContextIds = emptySet(),
             strictContextIds = emptySet(),
             protectedTargetPatterns = emptyList(),
+            authExceptionsEnabled = true,
             contextOverrides = emptyMap(),
         )
     }

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/applinks/AppLinkLauncher.kt

@@ -16,11 +16,15 @@ import mozilla.components.support.base.log.logger.Logger
  *   behaviour so the app opens in its own recents entry.
  * - [AUTOMATIC]: global-`always` or a remembered `alwaysOpen` rule — `NEW_TASK`, subject to the
  *   2 s same-package cooldown loop-breaker (§2.4).
+ * - [AUTHENTICATION]: same-caller Custom Tab / ActionView callback — `NEW_TASK | CLEAR_TOP` so the
+ *   originating app can resume its existing task. Not a user gesture, so it takes the same 2 s
+ *   cooldown as [AUTOMATIC] (AC applies its loop-breaker to authentication flows too).
  * - [MARKETPLACE]: install-app fallback — `NEW_TASK | CLEAR_TASK`.
  */
 enum class AppLinkLaunchMode {
     MANUAL,
     AUTOMATIC,
+    AUTHENTICATION,
     MARKETPLACE,
 }
 
@@ -34,9 +38,9 @@ enum class AppLinkLaunchResult {
 
 /**
  * Launches external apps. Every launch re-resolves immediately first (no cache) and verifies the
- * expected package before `startActivity` (§2.7). Automatic launches honour a 2 s same-package
+ * expected package before `startActivity` (§2.7). Automatic and authentication launches honour a 2 s
- * cooldown to break app→browser→app ping-pong loops (§2.4); manual and prompt-resolved opens are
+ * same-package cooldown to break app→browser→app ping-pong loops (§2.4); manual and prompt-resolved
- * user gestures that bypass the check but still record it.
+ * opens are user gestures that bypass the check but still record it.
  */
 class AppLinkLauncher(
     private val resolver: ExternalAppResolver,
@@ -81,7 +85,7 @@ class AppLinkLauncher(
             else -> resolved.packageName
         }
 
-        if (mode == AppLinkLaunchMode.AUTOMATIC) {
+        if (mode == AppLinkLaunchMode.AUTOMATIC || mode == AppLinkLaunchMode.AUTHENTICATION) {
             val (lastPackage, lastTs) = lastLaunch
             if (lastPackage != null && lastPackage == targetPackage &&
                 clock.elapsedRealtime() < lastTs + cooldownMs
@@ -117,6 +121,8 @@ class AppLinkLauncher(
                     Intent.FLAG_ACTIVITY_NEW_TASK
             AppLinkLaunchMode.AUTOMATIC ->
                 Intent.FLAG_ACTIVITY_NEW_TASK
+            AppLinkLaunchMode.AUTHENTICATION ->
+                Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TOP
             AppLinkLaunchMode.MARKETPLACE ->
                 Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
         }

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/applinks/AppLinkPolicyMapper.kt

@@ -28,6 +28,7 @@ fun AppLinkPolicySnapshot.toAppLinkPolicy(): AppLinkPolicy {
                 port = pattern.port?.toInt(),
             )
         },
+        authExceptionsEnabled = authExceptionsEnabled,
         contextOverrides = contextOverrides.mapValues { (_, override) ->
             ContextAppLinkPolicy(
                 globalMode = override.mode.toAppLinkMode(),

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/applinks/AppLinkPolicyStore.kt

@@ -93,6 +93,7 @@ class AppLinkPolicyStore internal constructor(
         root.put(FIELD_MIGRATED, migrated)
         root.put(FIELD_GLOBAL_MODE, policy.globalMode.name)
         root.put(FIELD_MARKETPLACE, policy.marketplaceFallbackEnabled)
+        root.put(FIELD_AUTH_EXCEPTIONS, policy.authExceptionsEnabled)
         root.put(FIELD_PROTECT_GENERAL, policy.protectGeneralContext)
         root.put(FIELD_PROTECTED_CONTEXTS, JSONArray(policy.protectedContextIds.toList()))
         root.put(FIELD_STRICT_CONTEXTS, JSONArray(policy.strictContextIds.toList()))
@@ -177,6 +178,7 @@ class AppLinkPolicyStore internal constructor(
             globalMode = AppLinkMode.valueOf(root.getString(FIELD_GLOBAL_MODE)),
             rules = rules,
             marketplaceFallbackEnabled = root.optBoolean(FIELD_MARKETPLACE, false),
+            authExceptionsEnabled = root.optBoolean(FIELD_AUTH_EXCEPTIONS, true),
             protectGeneralContext = root.optBoolean(FIELD_PROTECT_GENERAL, false),
             protectedContextIds = root.optJSONArray(FIELD_PROTECTED_CONTEXTS).toStringSet(),
             strictContextIds = root.optJSONArray(FIELD_STRICT_CONTEXTS).toStringSet(),
@@ -218,6 +220,7 @@ class AppLinkPolicyStore internal constructor(
         private const val FIELD_MIGRATED = "migrated"
         private const val FIELD_GLOBAL_MODE = "globalMode"
         private const val FIELD_MARKETPLACE = "marketplaceFallbackEnabled"
+        private const val FIELD_AUTH_EXCEPTIONS = "authExceptionsEnabled"
         private const val FIELD_PROTECT_GENERAL = "protectGeneralContext"
         private const val FIELD_PROTECTED_CONTEXTS = "protectedContextIds"
         private const val FIELD_STRICT_CONTEXTS = "strictContextIds"

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/applinks/WebLibreAppLinksInterceptor.kt

@@ -58,9 +58,27 @@ class WebLibreAppLinksInterceptor(
 
         val uriScheme = runCatching { uri.toUri().scheme }.getOrNull()
         val engineSupportsScheme = AppLinkSchemes.isEngineSupported(uriScheme)
+        val session = components.core.store.state.findTabOrCustomTab(engineSession)
+        val policy = AppLinkPolicyStores.forProfile(components.profileApplicationContext).policy
+
+        // A tab an external app opened for us (Custom Tab / ActionView) may be hosting a sign-in
+        // round trip. Gated on the policy so turning the carve-out off restores the plain §2.4
+        // eligibility rules rather than only skipping the launch below.
+        val authExceptionsAllowed = policy.authExceptionsEnabled && isPossibleAuthentication(session)
 
         // Step 2 — navigation eligibility. Any hit lets the engine proceed normally.
-        if (!isEligible(uri, lastUri, uriScheme, engineSupportsScheme, hasUserGesture, isRedirect, isDirectNavigation, isSubframeRequest)) {
+        if (!isEligible(
+                uri,
+                lastUri,
+                uriScheme,
+                engineSupportsScheme,
+                hasUserGesture,
+                isRedirect,
+                isDirectNavigation,
+                isSubframeRequest,
+                authExceptionsAllowed,
+            )
+        ) {
             return null
         }
 
@@ -74,10 +92,6 @@ class WebLibreAppLinksInterceptor(
 
         val resolved = runtime.resolver.resolve(uri, includeHttpAppLinks = true, useCache = true)
 
-        val policy = AppLinkPolicyStores.forProfile(components.profileApplicationContext).policy
-
-        val session = components.core.store.state.findTabOrCustomTab(engineSession)
-
         // Container isolation (replace semantics): a container with "isolated app link settings"
         // enabled contributes an entry keyed by its contextId. When the source tab's contextId has
         // one, its mode + rules fully replace the global ones for this navigation.
@@ -85,12 +99,47 @@ class WebLibreAppLinksInterceptor(
         val effectiveMode = override?.globalMode ?: policy.globalMode
         val effectiveRules = override?.rules ?: policy.rules
 
+        val isProtectedNavigation = isProtected(policy, session, uri)
+        val isPrivateNavigation = session?.content?.private ?: false
+        val isWalletNavigation = AppLinkSchemes.isWallet(resolved.originalScheme) ||
+            AppLinkSchemes.isWallet(resolved.intentDataScheme)
+
+        // An ambiguous resolution is never treated as a callback: with several handlers we cannot
+        // show the caller *is* the target, and the launch would raise a chooser rather than return
+        // to the app. AC declines here too — its package comes from the bound component, which is
+        // only set for an unambiguous handler.
+        val authTargetPackage = if (resolved.isAmbiguous) null else resolved.packageName
+
+        // §2.4 authentication carve-out (AC parity): a tab opened *by* the app the navigation
+        // targets is a sign-in round trip rather than a general app link, so it returns to its
+        // caller even under `never`. The forced-prompt contexts still win — a protected container,
+        // a private tab or a wallet scheme must not leak out silently, so those fall through to the
+        // classifier, which prompts for them regardless of mode (§2.4 step 4).
+        if (authExceptionsAllowed &&
+            isAuthenticationCallback(session, authTargetPackage) &&
+            !isProtectedNavigation && !isPrivateNavigation && !isWalletNavigation
+        ) {
+            val result = runtime.launcher.launch(
+                uri,
+                AppLinkLaunchMode.AUTHENTICATION,
+                expectedPackage = authTargetPackage,
+            )
+            logger.info(
+                "auth app-link callback uri=$uri tab=${session?.id} " +
+                    "caller=${callerPackage(session)} package=$authTargetPackage -> $result",
+            )
+            return if (result == AppLinkLaunchResult.LAUNCHED) {
+                RequestInterceptor.InterceptionResponse.Deny
+            } else {
+                safeNonLaunchResponse(pendingStore, resolved)
+            }
+        }
+
         val input = ClassifierInput(
             resolved = resolved,
-            isProtected = isProtected(policy, session, uri),
+            isProtected = isProtectedNavigation,
-            isPrivate = session?.content?.private ?: false,
+            isPrivate = isPrivateNavigation,
-            isWallet = AppLinkSchemes.isWallet(resolved.originalScheme) ||
+            isWallet = isWalletNavigation,
-                AppLinkSchemes.isWallet(resolved.intentDataScheme),
             missingSession = session == null,
             suppressionHit = session != null &&
                 pendingStore.isSuppressed(session.id, targetFingerprint(uri, resolved)),
@@ -262,6 +311,38 @@ class WebLibreAppLinksInterceptor(
         }
     }
 
+    /**
+     * True when [targetPackage] is the very app that opened this tab — the shape of a sign-in
+     * callback. [targetPackage] must be an unambiguous resolution; pass `null` otherwise.
+     */
+    private fun isAuthenticationCallback(session: SessionState?, targetPackage: String?): Boolean {
+        if (targetPackage.isNullOrEmpty()) return false
+        return callerPackage(session) == targetPackage
+    }
+
+    /**
+     * The package that launched this session, as recorded by
+     * [eu.weblibre.flutter_mozilla_components.activities.addExternalCallerInformation]. Note the
+     * underlying referrer is caller-supplied and can be spoofed, so this may only gate actions the
+     * caller could already perform itself (here: launching its own intent).
+     */
+    private fun callerPackage(session: SessionState?): String? {
+        return when (val source = session?.source) {
+            is SessionState.Source.External.CustomTab -> source.caller?.packageId
+            is SessionState.Source.External.ActionView -> source.caller?.packageId
+            else -> null
+        }
+    }
+
+    private fun isPossibleAuthentication(session: SessionState?): Boolean {
+        return when (session?.source) {
+            is SessionState.Source.External.CustomTab,
+            is SessionState.Source.External.ActionView,
+            -> true
+            else -> false
+        }
+    }
+
     // ---- Eligibility (§2.4 step 2) ----
 
     private fun isEligible(
@@ -273,6 +354,7 @@ class WebLibreAppLinksInterceptor(
         isRedirect: Boolean,
         isDirectNavigation: Boolean,
         isSubframeRequest: Boolean,
+        authExceptionsAllowed: Boolean,
     ): Boolean {
         if (uriScheme == null) return false
         // A subframe request not triggered by the user and outside the allowlist stays in-page.
@@ -282,8 +364,10 @@ class WebLibreAppLinksInterceptor(
         val isIntentionalNavigation = hasUserGesture || isAllowedRedirect || isDirectNavigation
         // Unintentional engine-supported navigation continues in the browser.
         if (engineSupportsScheme && !isIntentionalNavigation) return false
-        // Same-domain engine-supported navigation continues in the browser (AC subdomain stripping).
+        // Same-domain engine-supported navigation continues in the browser (AC subdomain stripping),
-        if (engineSupportsScheme && isSameDomain(lastUri, uri)) return false
+        // unless this tab could be hosting an authentication round trip whose callback is an http
+        // app link on the same site.
+        if (engineSupportsScheme && isSameDomain(lastUri, uri) && !authExceptionsAllowed) return false
         // Always-denied schemes never resolve or launch externally.
         if (AppLinkSchemes.isAlwaysDenied(uriScheme)) return false
         return true

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/pigeons/Gecko.g.kt

@@ -5830,6 +5830,11 @@ data class AppLinkPolicySnapshot (
   /** Remembered rules keyed by canonical scope. */
   val rules: Map<String, NativeAppLinkRule>,
   val marketplaceFallbackEnabled: Boolean,
+  /**
+   * Allows same-caller Custom Tab / ActionView authentication callbacks to
+   * return to their app even when the general app-link mode is `never`.
+   */
+  val authExceptionsEnabled: Boolean,
   /** Regular / no-contextId tabs are proxied via the `general` scope. */
   val protectGeneralContext: Boolean,
   /** contextIds that resolve to a proxy after inherit/bypass/alias. */
@@ -5850,12 +5855,13 @@ data class AppLinkPolicySnapshot (
       val globalMode = pigeonVar_list[0] as AppLinksMode
       val rules = pigeonVar_list[1] as Map<String, NativeAppLinkRule>
       val marketplaceFallbackEnabled = pigeonVar_list[2] as Boolean
-      val protectGeneralContext = pigeonVar_list[3] as Boolean
+      val authExceptionsEnabled = pigeonVar_list[3] as Boolean
-      val protectedContextIds = pigeonVar_list[4] as List<String>
+      val protectGeneralContext = pigeonVar_list[4] as Boolean
-      val strictContextIds = pigeonVar_list[5] as List<String>
+      val protectedContextIds = pigeonVar_list[5] as List<String>
-      val protectedTargetPatterns = pigeonVar_list[6] as List<ProtectedTargetPattern>
+      val strictContextIds = pigeonVar_list[6] as List<String>
-      val contextOverrides = pigeonVar_list[7] as Map<String, NativeContextAppLinkPolicy>
+      val protectedTargetPatterns = pigeonVar_list[7] as List<ProtectedTargetPattern>
-      return AppLinkPolicySnapshot(globalMode, rules, marketplaceFallbackEnabled, protectGeneralContext, protectedContextIds, strictContextIds, protectedTargetPatterns, contextOverrides)
+      val contextOverrides = pigeonVar_list[8] as Map<String, NativeContextAppLinkPolicy>
+      return AppLinkPolicySnapshot(globalMode, rules, marketplaceFallbackEnabled, authExceptionsEnabled, protectGeneralContext, protectedContextIds, strictContextIds, protectedTargetPatterns, contextOverrides)
     }
   }
   fun toList(): List<Any?> {
@@ -5863,6 +5869,7 @@ data class AppLinkPolicySnapshot (
       globalMode,
       rules,
       marketplaceFallbackEnabled,
+      authExceptionsEnabled,
       protectGeneralContext,
       protectedContextIds,
       strictContextIds,
@@ -5878,7 +5885,7 @@ data class AppLinkPolicySnapshot (
       return true
     }
     val other = other as AppLinkPolicySnapshot
-    return GeckoPigeonUtils.deepEquals(this.globalMode, other.globalMode) && GeckoPigeonUtils.deepEquals(this.rules, other.rules) && GeckoPigeonUtils.deepEquals(this.marketplaceFallbackEnabled, other.marketplaceFallbackEnabled) && GeckoPigeonUtils.deepEquals(this.protectGeneralContext, other.protectGeneralContext) && GeckoPigeonUtils.deepEquals(this.protectedContextIds, other.protectedContextIds) && GeckoPigeonUtils.deepEquals(this.strictContextIds, other.strictContextIds) && GeckoPigeonUtils.deepEquals(this.protectedTargetPatterns, other.protectedTargetPatterns) && GeckoPigeonUtils.deepEquals(this.contextOverrides, other.contextOverrides)
+    return GeckoPigeonUtils.deepEquals(this.globalMode, other.globalMode) && GeckoPigeonUtils.deepEquals(this.rules, other.rules) && GeckoPigeonUtils.deepEquals(this.marketplaceFallbackEnabled, other.marketplaceFallbackEnabled) && GeckoPigeonUtils.deepEquals(this.authExceptionsEnabled, other.authExceptionsEnabled) && GeckoPigeonUtils.deepEquals(this.protectGeneralContext, other.protectGeneralContext) && GeckoPigeonUtils.deepEquals(this.protectedContextIds, other.protectedContextIds) && GeckoPigeonUtils.deepEquals(this.strictContextIds, other.strictContextIds) && GeckoPigeonUtils.deepEquals(this.protectedTargetPatterns, other.protectedTargetPatterns) && GeckoPigeonUtils.deepEquals(this.contextOverrides, other.contextOverrides)
   }
 
   override fun hashCode(): Int {
@@ -5886,6 +5893,7 @@ data class AppLinkPolicySnapshot (
     result = 31 * result + GeckoPigeonUtils.deepHash(this.globalMode)
     result = 31 * result + GeckoPigeonUtils.deepHash(this.rules)
     result = 31 * result + GeckoPigeonUtils.deepHash(this.marketplaceFallbackEnabled)
+    result = 31 * result + GeckoPigeonUtils.deepHash(this.authExceptionsEnabled)
     result = 31 * result + GeckoPigeonUtils.deepHash(this.protectGeneralContext)
     result = 31 * result + GeckoPigeonUtils.deepHash(this.protectedContextIds)
     result = 31 * result + GeckoPigeonUtils.deepHash(this.strictContextIds)
@@ -5894,7 +5902,7 @@ data class AppLinkPolicySnapshot (
     return result
   }
   override fun toString(): String {
-    return "AppLinkPolicySnapshot(globalMode=$globalMode, rules=$rules, marketplaceFallbackEnabled=$marketplaceFallbackEnabled, protectGeneralContext=$protectGeneralContext, protectedContextIds=$protectedContextIds, strictContextIds=$strictContextIds, protectedTargetPatterns=$protectedTargetPatterns, contextOverrides=$contextOverrides)"
+    return "AppLinkPolicySnapshot(globalMode=$globalMode, rules=$rules, marketplaceFallbackEnabled=$marketplaceFallbackEnabled, authExceptionsEnabled=$authExceptionsEnabled, protectGeneralContext=$protectGeneralContext, protectedContextIds=$protectedContextIds, strictContextIds=$strictContextIds, protectedTargetPatterns=$protectedTargetPatterns, contextOverrides=$contextOverrides)"
   }
 }
 

packages/flutter_mozilla_components/android/src/test/kotlin/eu/weblibre/flutter_mozilla_components/applinks/AppLinkClassifierTest.kt

@@ -58,6 +58,11 @@ class AppLinkClassifierTest {
 
     // ---- §2.2 table: engine-supported (http) scheme, app resolves ----
 
+    @Test
+    fun safeDefaultAllowsAuthExceptions() {
+        assertEquals(true, AppLinkPolicy.SAFE_DEFAULT.authExceptionsEnabled)
+    }
+
     @Test
     fun engineSupportedAlwaysAutoLaunches() {
         val d = AppLinkClassifier.classify(

packages/flutter_mozilla_components/android/src/test/kotlin/eu/weblibre/flutter_mozilla_components/applinks/AppLinkLauncherTest.kt

@@ -13,6 +13,7 @@ import kotlin.test.assertEquals
 import org.mockito.ArgumentMatchers.anyBoolean
 import org.mockito.ArgumentMatchers.anyString
 import org.mockito.Mockito.mock
+import org.mockito.Mockito.verify
 import org.mockito.Mockito.`when`
 
 class AppLinkLauncherTest {
@@ -69,6 +70,33 @@ class AppLinkLauncherTest {
         assertEquals(1, started)
     }
 
+    @Test
+    fun authenticationLaunchUsesClearTopFlags() {
+        val intent = mock(Intent::class.java)
+        val resolved = ResolvedAppLink(
+            hasExternalApp = true,
+            appIntent = intent,
+            packageName = "com.example.app",
+            appName = "App",
+            fallbackUrl = null,
+            marketplaceIntent = null,
+            isAmbiguous = false,
+            engineSupportsScheme = false,
+            scopeKey = "pkg:com.example.app",
+            originalScheme = "example",
+            intentDataScheme = "example",
+        )
+        var startedIntent: Intent? = null
+        val l = launcher(resolved, FakeClock()) { startedIntent = it }
+
+        assertEquals(
+            AppLinkLaunchResult.LAUNCHED,
+            l.launch("example://callback", AppLinkLaunchMode.AUTHENTICATION),
+        )
+        verify(intent).flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TOP
+        assertEquals(intent, startedIntent)
+    }
+
     @Test
     fun automaticLaunchWithinCooldownIsRefused() {
         val clock = FakeClock(1000L)
@@ -78,6 +106,22 @@ class AppLinkLauncherTest {
         assertEquals(AppLinkLaunchResult.COOLDOWN, l.launch("zoommtg://x", AppLinkLaunchMode.AUTOMATIC))
     }
 
+    @Test
+    fun authenticationLaunchWithinCooldownIsRefused() {
+        val clock = FakeClock(1000L)
+        val l = launcher(resolvedFor("com.example.app"), clock)
+        assertEquals(
+            AppLinkLaunchResult.LAUNCHED,
+            l.launch("zoommtg://x", AppLinkLaunchMode.AUTHENTICATION),
+        )
+        // An app that re-opens its Custom Tab on receiving the callback would otherwise ping-pong.
+        clock.now = 1500L // < 2000 ms later
+        assertEquals(
+            AppLinkLaunchResult.COOLDOWN,
+            l.launch("zoommtg://x", AppLinkLaunchMode.AUTHENTICATION),
+        )
+    }
+
     @Test
     fun automaticLaunchAfterCooldownSucceeds() {
         val clock = FakeClock(1000L)

packages/flutter_mozilla_components/lib/src/pigeons/gecko.g.dart

@@ -6486,6 +6486,7 @@ class AppLinkPolicySnapshot {
     required this.globalMode,
     required this.rules,
     required this.marketplaceFallbackEnabled,
+    required this.authExceptionsEnabled,
     required this.protectGeneralContext,
     required this.protectedContextIds,
     required this.strictContextIds,
@@ -6500,6 +6501,10 @@ class AppLinkPolicySnapshot {
 
   bool marketplaceFallbackEnabled;
 
+  /// Allows same-caller Custom Tab / ActionView authentication callbacks to
+  /// return to their app even when the general app-link mode is `never`.
+  bool authExceptionsEnabled;
+
   /// Regular / no-contextId tabs are proxied via the `general` scope.
   bool protectGeneralContext;
 
@@ -6521,6 +6526,7 @@ class AppLinkPolicySnapshot {
       globalMode,
       rules,
       marketplaceFallbackEnabled,
+      authExceptionsEnabled,
       protectGeneralContext,
       protectedContextIds,
       strictContextIds,
@@ -6540,12 +6546,13 @@ class AppLinkPolicySnapshot {
       rules: (result[1]! as Map<Object?, Object?>)
           .cast<String, NativeAppLinkRule>(),
       marketplaceFallbackEnabled: result[2]! as bool,
-      protectGeneralContext: result[3]! as bool,
+      authExceptionsEnabled: result[3]! as bool,
-      protectedContextIds: (result[4]! as List<Object?>).cast<String>(),
+      protectGeneralContext: result[4]! as bool,
-      strictContextIds: (result[5]! as List<Object?>).cast<String>(),
+      protectedContextIds: (result[5]! as List<Object?>).cast<String>(),
-      protectedTargetPatterns: (result[6]! as List<Object?>)
+      strictContextIds: (result[6]! as List<Object?>).cast<String>(),
+      protectedTargetPatterns: (result[7]! as List<Object?>)
           .cast<ProtectedTargetPattern>(),
-      contextOverrides: (result[7]! as Map<Object?, Object?>)
+      contextOverrides: (result[8]! as Map<Object?, Object?>)
           .cast<String, NativeContextAppLinkPolicy>(),
     );
   }
@@ -6565,6 +6572,7 @@ class AppLinkPolicySnapshot {
           marketplaceFallbackEnabled,
           other.marketplaceFallbackEnabled,
         ) &&
+        _deepEquals(authExceptionsEnabled, other.authExceptionsEnabled) &&
         _deepEquals(protectGeneralContext, other.protectGeneralContext) &&
         _deepEquals(protectedContextIds, other.protectedContextIds) &&
         _deepEquals(strictContextIds, other.strictContextIds) &&
@@ -6578,7 +6586,7 @@ class AppLinkPolicySnapshot {
 
   @override
   String toString() {
-    return 'AppLinkPolicySnapshot(globalMode: $globalMode, rules: $rules, marketplaceFallbackEnabled: $marketplaceFallbackEnabled, protectGeneralContext: $protectGeneralContext, protectedContextIds: $protectedContextIds, strictContextIds: $strictContextIds, protectedTargetPatterns: $protectedTargetPatterns, contextOverrides: $contextOverrides)';
+    return 'AppLinkPolicySnapshot(globalMode: $globalMode, rules: $rules, marketplaceFallbackEnabled: $marketplaceFallbackEnabled, authExceptionsEnabled: $authExceptionsEnabled, protectGeneralContext: $protectGeneralContext, protectedContextIds: $protectedContextIds, strictContextIds: $strictContextIds, protectedTargetPatterns: $protectedTargetPatterns, contextOverrides: $contextOverrides)';
   }
 }
 

packages/flutter_mozilla_components/pigeons/gecko.dart

@@ -2994,6 +2994,10 @@ class AppLinkPolicySnapshot {
 
   final bool marketplaceFallbackEnabled;
 
+  /// Allows same-caller Custom Tab / ActionView authentication callbacks to
+  /// return to their app even when the general app-link mode is `never`.
+  final bool authExceptionsEnabled;
+
   /// Regular / no-contextId tabs are proxied via the `general` scope.
   final bool protectGeneralContext;
 
@@ -3014,6 +3018,7 @@ class AppLinkPolicySnapshot {
     required this.globalMode,
     required this.rules,
     required this.marketplaceFallbackEnabled,
+    required this.authExceptionsEnabled,
     required this.protectGeneralContext,
     required this.protectedContextIds,
     required this.strictContextIds,