fix(push): honor legacy relay channel grammar before publication

Signed-off-by: Tom Brow <tomb@block.xyz>

docs/buzz-push.md

@@ -30,7 +30,11 @@ filters match event tags exactly. Array and string limits, community scoping,
 and channel membership checks still apply.
 
 Mobile accepts both this descriptor and the older `uuid-v4-lowercase`
-descriptor. Older relays continue to reject non-v4 channel filters. Deploy
+descriptor. Mobile checks both positive and ignore channel filters against
+the advertised grammar before enrollment or publication. A lease requiring
+non-v4 IDs on an older relay remains unavailable until that relay upgrades;
+mobile preserves all desired filters and rechecks capabilities every five
+minutes instead of sending an invalid lease. Deploy
 mobile support for `uuid-lowercase` before changing the relay advertisement:
 older mobile clients reject that descriptor and cannot renew their push leases.
 The new grammar does not alter existing UUIDv4 subscriptions.

mobile/lib/shared/push/dev_push_lease.dart

@@ -19,6 +19,9 @@ const _installationIdPattern = r'^[0-9a-f]{32}$';
 
 class BuzzPushLeaseDescriptor {
   final String origin;
+
+  /// Canonical channel-ID grammar advertised by this relay.
+  final String hGrammar;
   final String executorKeyId;
   final String executorPubkey;
   final String transport;
@@ -30,6 +33,7 @@ class BuzzPushLeaseDescriptor {
 
   const BuzzPushLeaseDescriptor({
     required this.origin,
+    this.hGrammar = 'uuid-v4-lowercase',
     required this.executorKeyId,
     required this.executorPubkey,
     required this.transport,
@@ -115,8 +119,7 @@ class BuzzPushLeaseDescriptor {
       );
     }
     final hGrammar = _nonEmptyString(push['h_grammar'], name: 'h_grammar');
-    // Older relays advertise the narrower grammar. Keep UUIDv4 leases working
-    // during rollout; those relays still reject non-v4 channels themselves.
+    // Retain the advertised grammar so publication can enforce legacy limits.
     if (hGrammar != 'uuid-lowercase' && hGrammar != 'uuid-v4-lowercase') {
       throw const FormatException('Unsupported push h_grammar');
     }
@@ -187,6 +190,7 @@ class BuzzPushLeaseDescriptor {
 
     return BuzzPushLeaseDescriptor(
       origin: origin,
+      hGrammar: hGrammar,
       executorKeyId: currentKey['id'] as String,
       executorPubkey: currentKey['pubkey'] as String,
       transport: transport,
@@ -199,6 +203,33 @@ class BuzzPushLeaseDescriptor {
   }
 }
 
+/// The desired lease requires channel IDs that this relay cannot accept yet.
+class BuzzPushChannelGrammarException implements Exception {
+  const BuzzPushChannelGrammarException();
+
+  @override
+  String toString() =>
+      'Push lease requires uuid-lowercase support from the relay';
+}
+
+/// Validate both positive and ignore filters without weakening mute semantics.
+void validateBuzzPushChannelGrammar(
+  BuzzPushLeaseDescriptor descriptor,
+  List<BuzzPushSubscription> subscriptions,
+) {
+  if (descriptor.hGrammar == 'uuid-lowercase') return;
+  for (final subscription in subscriptions) {
+    for (final filter in [subscription.filter, ...subscription.ignore]) {
+      for (final channel in filter.hTags ?? const <String>[]) {
+        // The legacy Rust validator checked version 4, not the UUID variant.
+        if (channel[14] != '4') {
+          throw const BuzzPushChannelGrammarException();
+        }
+      }
+    }
+  }
+}
+
 Future<BuzzPushLeaseDescriptor> fetchBuzzPushLeaseDescriptor(
   String relayBaseUrl, {
   http.Client? client,
@@ -262,6 +293,7 @@ Future<BuzzPushLeasePublication> publishBuzzDevPushLease({
   required BuzzPushLeaseSubmit submit,
   DateTime Function() now = DateTime.now,
 }) async {
+  validateBuzzPushChannelGrammar(descriptor, subscriptions);
   _validateGrant(grant, descriptor);
   final effectiveLeaseInstallationId =
       leaseInstallationId ?? grant.installationId;

mobile/lib/shared/push/push_bootstrap.dart

@@ -82,6 +82,7 @@ String buzzPushPublicationAttemptKey({
   token,
   descriptor.executorKeyId,
   descriptor.executorPubkey,
+  descriptor.hGrammar,
   buzzPushSubscriptionsFingerprint(subscriptions),
 ].join('|');
 
@@ -318,8 +319,13 @@ class BuzzPushBootstrap extends HookConsumerWidget {
               },
             );
           } catch (error, stack) {
-            publicationAttempt.failed(
+            publicationAttempt.retryAfter(
               attempt,
+              // Re-fetch capabilities after a relay upgrade without repeatedly
+              // enrolling or publishing a lease the old relay cannot accept.
+              delay: error is BuzzPushChannelGrammarException
+                  ? const Duration(minutes: 5)
+                  : _pushBootstrapRetryDelay,
               retry: () {
                 if (context.mounted) publicationRetry.value += 1;
               },
@@ -380,6 +386,7 @@ class BuzzPushBootstrap extends HookConsumerWidget {
     final descriptor = await ref.read(buzzPushDescriptorFetcherProvider)(
       config.baseUrl,
     );
+    validateBuzzPushChannelGrammar(descriptor, desired);
     final grant = await enrollBuzzPush(
       config.wsUrl,
       Env.pushGatewayUrl,

mobile/test/shared/push/dev_push_lease_test.dart

@@ -33,6 +33,74 @@ void main() {
     });
   }
 
+  for (final ignored in [false, true]) {
+    test(
+      'legacy relay rejects non-v4 ${ignored ? 'ignore' : 'positive'} filters before submission',
+      () async {
+        final information = _descriptorJson(relay.public);
+        (information['push'] as Map<String, dynamic>)['h_grammar'] =
+            'uuid-v4-lowercase';
+        final legacy = BuzzPushLeaseDescriptor.fromRelayInformation(
+          information,
+        );
+        final channelFilter = BuzzPushFilter(
+          kinds: const [9],
+          hTags: const ['fee88e92-da9f-5958-a910-48db3264ad38'],
+        );
+        var submissions = 0;
+        await expectLater(
+          publishBuzzDevPushLease(
+            grant: grant,
+            descriptor: legacy,
+            nsec: signer.nsec,
+            memberPubkey: signer.public,
+            subscriptions: [
+              BuzzPushSubscription(
+                filter: ignored
+                    ? BuzzPushFilter(kinds: const [9], pTags: [signer.public])
+                    : channelFilter,
+                notificationClass: 'default',
+                ignore: ignored ? [channelFilter] : const [],
+              ),
+            ],
+            now: () => now,
+            submit:
+                ({
+                  required kind,
+                  required content,
+                  required tags,
+                  createdAt,
+                }) async {
+                  submissions++;
+                  throw StateError('incompatible lease must not be sent');
+                },
+          ),
+          throwsA(isA<BuzzPushChannelGrammarException>()),
+        );
+        expect(submissions, 0);
+      },
+    );
+  }
+
+  test('legacy relay keeps compatible subscriptions and ignores intact', () {
+    final information = _descriptorJson(relay.public);
+    (information['push'] as Map<String, dynamic>)['h_grammar'] =
+        'uuid-v4-lowercase';
+    final legacy = BuzzPushLeaseDescriptor.fromRelayInformation(information);
+    final subscriptions = buildDesiredBuzzPushSubscriptions(
+      myPubkey: signer.public,
+      channelIds: const [
+        '11111111-1111-4111-8111-111111111111',
+        '22222222-2222-4222-8222-222222222222',
+      ],
+      mutedChannelIds: const ['22222222-2222-4222-8222-222222222222'],
+    );
+    final before = buzzPushSubscriptionsFingerprint(subscriptions);
+    validateBuzzPushChannelGrammar(legacy, subscriptions);
+    expect(buzzPushSubscriptionsFingerprint(subscriptions), before);
+    expect(legacy.hGrammar, 'uuid-v4-lowercase');
+  });
+
   test('legacy capability does not enable Buzz push', () {
     final information = _descriptorJson(relay.public);
     information['supported_extensions'] = ['nip-pl'];

mobile/test/shared/push/push_bootstrap_test.dart

@@ -168,6 +168,21 @@ void main() {
     );
   });
 
+  test('relay grammar upgrade changes publication attempt identity', () {
+    String key(String grammar) => buzzPushPublicationAttemptKey(
+      communityId: 'community',
+      relayBaseUrl: 'https://relay.example',
+      token: 'token',
+      descriptor: _descriptor(
+        keyId: 'relay-v1',
+        pubkey: _hex('b'),
+        hGrammar: grammar,
+      ),
+      subscriptions: const [],
+    );
+    expect(key('uuid-lowercase'), isNot(key('uuid-v4-lowercase')));
+  });
+
   test('default push requires relay capability and respects opt-out', () {
     final enabled = Community.create(
       name: 'Team',
@@ -269,8 +284,10 @@ void main() {
 BuzzPushLeaseDescriptor _descriptor({
   required String keyId,
   required String pubkey,
+  String hGrammar = 'uuid-v4-lowercase',
 }) => BuzzPushLeaseDescriptor(
   origin: 'wss://relay.example',
+  hGrammar: hGrammar,
   executorKeyId: keyId,
   executorPubkey: pubkey,
   transport: 'apns',