pick http for .onion by default

apps/weblibre/assets/preferences/settings.json

@@ -821,6 +821,13 @@
                     "enforceOnStartup": true,
                     "locked": true
                 },
+                "dom.security.https_only_mode.upgrade_onion": {
+                    "value": false,
+                    "title": "Keep .onion sites on HTTP",
+                    "description": "Exempts .onion hosts from HTTPS-Only/HTTPS-First upgrades. Onion services are reached over an encrypted, self-authenticating Tor circuit, so HTTP carries no clearnet exposure and most onion sites are HTTP-only.",
+                    "enforceOnStartup": true,
+                    "locked": true
+                },
                 "security.mixed_content.upgrade_display_content": {
                     "value": true,
                     "title": "Upgrade mixed display content to HTTPS",

apps/weblibre/lib/utils/input_classification.dart

@@ -27,6 +27,7 @@ enum NavigationReason {
   explicitScheme,
   schemelessHost,
   localhost,
+  onionHost,
   ipLiteral,
   aboutLike,
 }
@@ -145,6 +146,13 @@ InputClassification classifyAddressBarInput(
       );
     }
 
+    if (isOnionHost(schemelessUri.host)) {
+      return InputClassification.navigate(
+        schemelessUri,
+        NavigationReason.onionHost,
+      );
+    }
+
     if (InternetAddress.tryParse(schemelessUri.host) != null) {
       return InputClassification.navigate(
         schemelessUri,

apps/weblibre/lib/utils/uri_input_parser.dart

@@ -114,6 +114,12 @@ bool isValidHostCandidate(String hostCandidate) {
   return true;
 }
 
+bool isOnionHost(String host) {
+  // RFC 7686: ".onion" must be the final label, never a substring. The leading
+  // dot requirement rejects bare "onion", "notonion.com" and "onion.evil.com".
+  return host.toLowerCase().endsWith('.onion');
+}
+
 bool looksLikeHostExpression(String input) {
   return input.contains('.') ||
       input.contains(':') ||
@@ -183,7 +189,13 @@ Uri? parseSchemelessWebHost(
     return null;
   }
 
-  final scheme = probeUri.host.toLowerCase() == 'localhost' ? 'http' : 'https';
+  // Onion services are self-authenticating and reached over an encrypted Tor
+  // circuit, so http carries no clearnet exposure; default them to http like
+  // localhost (see Tor Browser's HTTPS-Only exemption for .onion).
+  final lowerHost = probeUri.host.toLowerCase();
+  final scheme = (lowerHost == 'localhost' || isOnionHost(lowerHost))
+      ? 'http'
+      : 'https';
   if (allowedSchemes != null && !allowedSchemes.contains(scheme)) {
     return null;
   }

apps/weblibre/test/utils/input_classification_test.dart

@@ -41,6 +41,49 @@ void main() {
       expect(navigation.uri.toString(), 'https://weblibre.eu');
     });
 
+    test('navigates onion host over http', () {
+      final result = classifyAddressBarInput(
+        'duckduckgogg42xjoc72x3sjasowoarfbgcmvfimaftt6twagswzczad.onion/path',
+      );
+
+      expect(result, isA<NavigateInputClassification>());
+      final navigation = result as NavigateInputClassification;
+      expect(navigation.reason, NavigationReason.onionHost);
+      expect(
+        navigation.uri.toString(),
+        'http://duckduckgogg42xjoc72x3sjasowoarfbgcmvfimaftt6twagswzczad.onion/path',
+      );
+    });
+
+    test('keeps explicit https on onion host', () {
+      final result = classifyAddressBarInput(
+        'https://duckduckgogg42xjoc72x3sjasowoarfbgcmvfimaftt6twagswzczad.onion',
+      );
+
+      expect(result, isA<NavigateInputClassification>());
+      final navigation = result as NavigateInputClassification;
+      expect(navigation.reason, NavigationReason.explicitScheme);
+      expect(navigation.uri.scheme, 'https');
+    });
+
+    test('does not http-default a non-onion lookalike host', () {
+      final result = classifyAddressBarInput('notonion.com');
+
+      expect(result, isA<NavigateInputClassification>());
+      final navigation = result as NavigateInputClassification;
+      expect(navigation.reason, NavigationReason.schemelessHost);
+      expect(navigation.uri.toString(), 'https://notonion.com');
+    });
+
+    test('does not http-default onion as a non-final label', () {
+      final result = classifyAddressBarInput('onion.example.com');
+
+      expect(result, isA<NavigateInputClassification>());
+      final navigation = result as NavigateInputClassification;
+      expect(navigation.reason, NavigationReason.schemelessHost);
+      expect(navigation.uri.toString(), 'https://onion.example.com');
+    });
+
     test('navigates localhost over http', () {
       final result = classifyAddressBarInput('localhost:8080');