Fix MAX emoji attachments

server/QMax.Api/Program.cs

@@ -160,9 +160,12 @@ static async Task EnsureCompatibilitySchemaAsync(QMaxDbContext db)
         await db.Database.ExecuteSqlRawAsync("ALTER TABLE MessageAttachments ADD COLUMN ExternalId TEXT;");
     }
 
+    await RemoveDuplicateMessageAttachmentsAsync(db);
+    await db.Database.ExecuteSqlRawAsync("DROP INDEX IF EXISTS IX_MessageAttachments_MessageId_ExternalId;");
     await db.Database.ExecuteSqlRawAsync("""
-        CREATE INDEX IF NOT EXISTS IX_MessageAttachments_MessageId_ExternalId
-        ON MessageAttachments (MessageId, ExternalId);
+        CREATE UNIQUE INDEX IF NOT EXISTS IX_MessageAttachments_MessageId_ExternalId
+        ON MessageAttachments (MessageId, ExternalId)
+        WHERE ExternalId IS NOT NULL AND ExternalId <> '';
         """);
 
     await db.Database.ExecuteSqlRawAsync("""
@@ -189,6 +192,29 @@ static async Task EnsureCompatibilitySchemaAsync(QMaxDbContext db)
     await RemoveGenericMediaLabelsAsync(db);
 }
 
+static async Task RemoveDuplicateMessageAttachmentsAsync(QMaxDbContext db)
+{
+    var attachments = await db.MessageAttachments
+        .Where(attachment => attachment.ExternalId != null && attachment.ExternalId != "")
+        .ToListAsync();
+
+    var duplicates = attachments
+        .OrderBy(attachment => attachment.MessageId)
+        .ThenBy(attachment => attachment.ExternalId)
+        .ThenByDescending(attachment => attachment.FileSizeBytes)
+        .ThenBy(attachment => attachment.CreatedAt)
+        .GroupBy(attachment => new { attachment.MessageId, attachment.ExternalId })
+        .SelectMany(group => group.Skip(1))
+        .ToList();
+    if (duplicates.Count == 0)
+    {
+        return;
+    }
+
+    db.MessageAttachments.RemoveRange(duplicates);
+    await db.SaveChangesAsync();
+}
+
 static async Task RemoveGenericMediaLabelsAsync(QMaxDbContext db)
 {
     var placeholderMessages = await db.Messages

server/QMax.Api/Services/MaxBridgeSyncService.cs

@@ -194,7 +194,7 @@ public sealed class MaxBridgeSyncService(
                     DeliveryState = ResolveDeliveryState(incoming)
                 };
 
-                foreach (var incomingAttachment in incoming.Attachments ?? [])
+                foreach (var incomingAttachment in DistinctAttachments(incoming.Attachments ?? []))
                 {
                     var attachment = await CreateAttachmentAsync(incomingAttachment, maxBridgeClient, storage, cancellationToken);
                     message.Attachments.Add(attachment);
@@ -481,7 +481,7 @@ public sealed class MaxBridgeSyncService(
         var metadataChanged = false;
         var addedAttachments = new List<MessageAttachment>();
         var knownAttachments = message.Attachments.ToList();
-        var incomingAttachments = incoming.Attachments ?? [];
+        var incomingAttachments = DistinctAttachments(incoming.Attachments ?? []);
         var cleanText = MessageTextSanitizer.CleanMessageText(
             incoming.Text,
             incomingAttachments.Count > 0 || message.Attachments.Count > 0);
@@ -564,6 +564,41 @@ public sealed class MaxBridgeSyncService(
         return new MessageMergeResult(changed, addedAttachments);
     }
 
+    private static IReadOnlyList<MaxAttachmentUpdate> DistinctAttachments(IReadOnlyList<MaxAttachmentUpdate> attachments)
+    {
+        if (attachments.Count <= 1)
+        {
+            return attachments;
+        }
+
+        var seen = new HashSet<string>(StringComparer.Ordinal);
+        var result = new List<MaxAttachmentUpdate>(attachments.Count);
+        foreach (var attachment in attachments)
+        {
+            if (seen.Add(AttachmentIdentity(attachment)))
+            {
+                result.Add(attachment);
+            }
+        }
+
+        return result;
+    }
+
+    private static string AttachmentIdentity(MaxAttachmentUpdate attachment)
+    {
+        if (!string.IsNullOrWhiteSpace(attachment.ExternalId))
+        {
+            return $"external:{attachment.ExternalId}";
+        }
+
+        if (!string.IsNullOrWhiteSpace(attachment.RemoteUrl))
+        {
+            return $"remote:{attachment.RemoteUrl}";
+        }
+
+        return $"fallback:{attachment.Kind}:{attachment.FileName}:{attachment.SortOrder}:{attachment.TextContent?.Length ?? 0}";
+    }
+
     private static async Task<MessageAttachment> CreateAttachmentAsync(
         MaxAttachmentUpdate incoming,
         IMaxBridgeClient maxBridgeClient,