diff --git a/.gitignore b/.gitignore
index 842a7a9..cf13ab2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,6 +20,8 @@ local.properties
 
 # QMAX runtime data and secrets
 data/
+!server/QMax.Api/Data/
+!server/QMax.Api/Data/**
 storage/
 secrets/
 .env
diff --git a/server/QMax.Api/Data/Entities/Chat.cs b/server/QMax.Api/Data/Entities/Chat.cs
new file mode 100644
index 0000000..2b541ea
--- /dev/null
+++ b/server/QMax.Api/Data/Entities/Chat.cs
@@ -0,0 +1,19 @@
+namespace QMax.Api.Data.Entities;
+
+public sealed class Chat
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    public string? ExternalId { get; set; }
+    public ChatKind Kind { get; set; } = ChatKind.MaxDialog;
+    public string Title { get; set; } = "MAX chat";
+    public string? AvatarUrl { get; set; }
+    public string? LastMessagePreview { get; set; }
+    public DateTimeOffset? LastMessageAt { get; set; }
+    public int UnreadCount { get; set; }
+    public bool IsPinned { get; set; }
+    public bool IsMuted { get; set; }
+    public bool IsArchived { get; set; }
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
+    public ICollection<Message> Messages { get; set; } = new List<Message>();
+}
diff --git a/server/QMax.Api/Data/Entities/Enums.cs b/server/QMax.Api/Data/Entities/Enums.cs
new file mode 100644
index 0000000..47bd166
--- /dev/null
+++ b/server/QMax.Api/Data/Entities/Enums.cs
@@ -0,0 +1,36 @@
+namespace QMax.Api.Data.Entities;
+
+public enum ChatKind
+{
+    Direct = 0,
+    Group = 1,
+    Channel = 2,
+    MaxDialog = 3
+}
+
+public enum MessageDirection
+{
+    Incoming = 0,
+    Outgoing = 1,
+    System = 2
+}
+
+public enum MessageDeliveryState
+{
+    Sending = 0,
+    Sent = 1,
+    Delivered = 2,
+    Read = 3,
+    Failed = 4
+}
+
+public enum AttachmentKind
+{
+    File = 0,
+    VoiceNote = 1,
+    Image = 2,
+    Video = 3,
+    Sticker = 4,
+    Gif = 5,
+    Contact = 6
+}
diff --git a/server/QMax.Api/Data/Entities/MaxAccountState.cs b/server/QMax.Api/Data/Entities/MaxAccountState.cs
new file mode 100644
index 0000000..65544a8
--- /dev/null
+++ b/server/QMax.Api/Data/Entities/MaxAccountState.cs
@@ -0,0 +1,12 @@
+namespace QMax.Api.Data.Entities;
+
+public sealed class MaxAccountState
+{
+    public int Id { get; set; } = 1;
+    public string PhoneNumber { get; set; } = "";
+    public string Status { get; set; } = "NotStarted";
+    public bool IsAuthorized { get; set; }
+    public string? LastUrl { get; set; }
+    public string? LastError { get; set; }
+    public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
diff --git a/server/QMax.Api/Data/Entities/Message.cs b/server/QMax.Api/Data/Entities/Message.cs
new file mode 100644
index 0000000..ec57fe1
--- /dev/null
+++ b/server/QMax.Api/Data/Entities/Message.cs
@@ -0,0 +1,23 @@
+namespace QMax.Api.Data.Entities;
+
+public sealed class Message
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    public Guid ChatId { get; set; }
+    public Chat? Chat { get; set; }
+    public string? ExternalId { get; set; }
+    public string? SenderExternalId { get; set; }
+    public string? SenderName { get; set; }
+    public MessageDirection Direction { get; set; }
+    public string? Text { get; set; }
+    public DateTimeOffset SentAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset? EditedAt { get; set; }
+    public DateTimeOffset? DeletedAt { get; set; }
+    public Guid? ReplyToMessageId { get; set; }
+    public string? ForwardedFrom { get; set; }
+    public MessageDeliveryState DeliveryState { get; set; } = MessageDeliveryState.Sent;
+    public string? Error { get; set; }
+    public string? MediaAlbumId { get; set; }
+    public ICollection<MessageAttachment> Attachments { get; set; } = new List<MessageAttachment>();
+    public ICollection<MessageReaction> Reactions { get; set; } = new List<MessageReaction>();
+}
diff --git a/server/QMax.Api/Data/Entities/MessageAttachment.cs b/server/QMax.Api/Data/Entities/MessageAttachment.cs
new file mode 100644
index 0000000..1425359
--- /dev/null
+++ b/server/QMax.Api/Data/Entities/MessageAttachment.cs
@@ -0,0 +1,18 @@
+namespace QMax.Api.Data.Entities;
+
+public sealed class MessageAttachment
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    public Guid MessageId { get; set; }
+    public Message? Message { get; set; }
+    public string? ExternalId { get; set; }
+    public string OriginalFileName { get; set; } = "file";
+    public string StorageFileName { get; set; } = "";
+    public string ContentType { get; set; } = "application/octet-stream";
+    public long FileSizeBytes { get; set; }
+    public string? Sha256 { get; set; }
+    public AttachmentKind Kind { get; set; } = AttachmentKind.File;
+    public int SortOrder { get; set; }
+    public string? RemoteUrl { get; set; }
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
diff --git a/server/QMax.Api/Data/Entities/MessageReaction.cs b/server/QMax.Api/Data/Entities/MessageReaction.cs
new file mode 100644
index 0000000..3fd13ff
--- /dev/null
+++ b/server/QMax.Api/Data/Entities/MessageReaction.cs
@@ -0,0 +1,12 @@
+namespace QMax.Api.Data.Entities;
+
+public sealed class MessageReaction
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    public Guid MessageId { get; set; }
+    public Message? Message { get; set; }
+    public string Emoji { get; set; } = "";
+    public string ActorKey { get; set; } = "self";
+    public string? ActorName { get; set; }
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
diff --git a/server/QMax.Api/Data/Entities/PushDevice.cs b/server/QMax.Api/Data/Entities/PushDevice.cs
new file mode 100644
index 0000000..1bca38f
--- /dev/null
+++ b/server/QMax.Api/Data/Entities/PushDevice.cs
@@ -0,0 +1,12 @@
+namespace QMax.Api.Data.Entities;
+
+public sealed class PushDevice
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    public Guid UserId { get; set; }
+    public User? User { get; set; }
+    public string FirebaseToken { get; set; } = "";
+    public string Platform { get; set; } = "android";
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
diff --git a/server/QMax.Api/Data/Entities/User.cs b/server/QMax.Api/Data/Entities/User.cs
new file mode 100644
index 0000000..7ecd842
--- /dev/null
+++ b/server/QMax.Api/Data/Entities/User.cs
@@ -0,0 +1,12 @@
+namespace QMax.Api.Data.Entities;
+
+public sealed class User
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    public string DisplayName { get; set; } = "QMAX Owner";
+    public string? PhoneNumber { get; set; }
+    public string? AvatarPath { get; set; }
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
+    public ICollection<UserSession> Sessions { get; set; } = new List<UserSession>();
+}
diff --git a/server/QMax.Api/Data/Entities/UserSession.cs b/server/QMax.Api/Data/Entities/UserSession.cs
new file mode 100644
index 0000000..e5557c8
--- /dev/null
+++ b/server/QMax.Api/Data/Entities/UserSession.cs
@@ -0,0 +1,14 @@
+namespace QMax.Api.Data.Entities;
+
+public sealed class UserSession
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    public Guid UserId { get; set; }
+    public User? User { get; set; }
+    public string DeviceName { get; set; } = "Android";
+    public string RefreshTokenHash { get; set; } = "";
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset LastSeenAt { get; set; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset ExpiresAt { get; set; } = DateTimeOffset.UtcNow.AddDays(90);
+    public DateTimeOffset? RevokedAt { get; set; }
+}
diff --git a/server/QMax.Api/Data/QMaxDatabaseCleanup.cs b/server/QMax.Api/Data/QMaxDatabaseCleanup.cs
new file mode 100644
index 0000000..58426c3
--- /dev/null
+++ b/server/QMax.Api/Data/QMaxDatabaseCleanup.cs
@@ -0,0 +1,93 @@
+using Microsoft.EntityFrameworkCore;
+using QMax.Api.Data.Entities;
+
+namespace QMax.Api.Data;
+
+public static class QMaxDatabaseCleanup
+{
+    public static async Task RemoveLegacyWebFileAttachmentEchoesAsync(QMaxDbContext db)
+    {
+        var connection = db.Database.GetDbConnection();
+        if (connection.State != System.Data.ConnectionState.Open)
+        {
+            await connection.OpenAsync();
+        }
+
+        await db.Database.ExecuteSqlRawAsync("DROP TABLE IF EXISTS temp.LegacyWebFileMessageIds;");
+        await db.Database.ExecuteSqlRawAsync("""
+            CREATE TEMP TABLE LegacyWebFileMessageIds (
+                Id TEXT NOT NULL PRIMARY KEY
+            );
+            """);
+        await db.Database.ExecuteSqlRawAsync("""
+            INSERT OR IGNORE INTO LegacyWebFileMessageIds (Id)
+            SELECT DISTINCT legacy.Id
+            FROM Messages AS legacy
+            INNER JOIN MessageAttachments AS legacyAttachment ON legacyAttachment.MessageId = legacy.Id
+            WHERE legacy.Direction = 'Outgoing'
+              AND legacy.ExternalId LIKE 'web-file-%'
+              AND legacyAttachment.Sha256 IS NOT NULL
+              AND legacyAttachment.Sha256 <> ''
+              AND EXISTS (
+                  SELECT 1
+                  FROM Messages AS confirmed
+                  INNER JOIN MessageAttachments AS confirmedAttachment ON confirmedAttachment.MessageId = confirmed.Id
+                  WHERE confirmed.ChatId = legacy.ChatId
+                    AND confirmed.Id <> legacy.Id
+                    AND confirmed.Direction = 'Outgoing'
+                    AND confirmed.ExternalId IS NOT NULL
+                    AND confirmed.ExternalId NOT LIKE 'web-file-%'
+                    AND confirmedAttachment.Sha256 = legacyAttachment.Sha256
+              );
+            """);
+        await db.Database.ExecuteSqlRawAsync("""
+            DELETE FROM MessageAttachments
+            WHERE MessageId IN (SELECT Id FROM LegacyWebFileMessageIds);
+            """);
+        await db.Database.ExecuteSqlRawAsync("""
+            DELETE FROM Messages
+            WHERE Id IN (SELECT Id FROM LegacyWebFileMessageIds);
+            """);
+        await db.Database.ExecuteSqlRawAsync("DROP TABLE IF EXISTS temp.LegacyWebFileMessageIds;");
+    }
+
+    public static async Task ClearUnreadCountsForLatestOutgoingChatsAsync(QMaxDbContext db)
+    {
+        var unreadChats = await db.Chats
+            .Where(chat => chat.UnreadCount > 0)
+            .ToListAsync();
+
+        if (unreadChats.Count == 0)
+        {
+            return;
+        }
+
+        var changed = false;
+        foreach (var chat in unreadChats)
+        {
+            var chatMessages = await db.Messages
+                .Where(message => message.ChatId == chat.Id && message.DeletedAt == null)
+                .Select(message => new { message.Direction, message.SentAt, message.Id })
+                .ToListAsync();
+
+            var latestMessage = chatMessages
+                .OrderByDescending(message => message.SentAt)
+                .ThenByDescending(message => message.Id)
+                .FirstOrDefault();
+
+            if (latestMessage?.Direction != MessageDirection.Outgoing)
+            {
+                continue;
+            }
+
+            chat.UnreadCount = 0;
+            chat.UpdatedAt = DateTimeOffset.UtcNow;
+            changed = true;
+        }
+
+        if (changed)
+        {
+            await db.SaveChangesAsync();
+        }
+    }
+}
diff --git a/server/QMax.Api/Data/QMaxDbContext.cs b/server/QMax.Api/Data/QMaxDbContext.cs
new file mode 100644
index 0000000..218b976
--- /dev/null
+++ b/server/QMax.Api/Data/QMaxDbContext.cs
@@ -0,0 +1,57 @@
+using Microsoft.EntityFrameworkCore;
+using QMax.Api.Data.Entities;
+
+namespace QMax.Api.Data;
+
+public sealed class QMaxDbContext(DbContextOptions<QMaxDbContext> options) : DbContext(options)
+{
+    public DbSet<User> Users => Set<User>();
+    public DbSet<UserSession> UserSessions => Set<UserSession>();
+    public DbSet<Chat> Chats => Set<Chat>();
+    public DbSet<Message> Messages => Set<Message>();
+    public DbSet<MessageAttachment> MessageAttachments => Set<MessageAttachment>();
+    public DbSet<MessageReaction> MessageReactions => Set<MessageReaction>();
+    public DbSet<PushDevice> PushDevices => Set<PushDevice>();
+    public DbSet<MaxAccountState> MaxAccountStates => Set<MaxAccountState>();
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        modelBuilder.Entity<User>().HasIndex(x => x.PhoneNumber);
+        modelBuilder.Entity<UserSession>().HasIndex(x => x.RefreshTokenHash).IsUnique();
+        modelBuilder.Entity<Chat>().HasIndex(x => x.ExternalId).IsUnique();
+        modelBuilder.Entity<Message>().HasIndex(x => new { x.ChatId, x.SentAt });
+        modelBuilder.Entity<Message>().HasIndex(x => x.ExternalId);
+        modelBuilder.Entity<MessageAttachment>().HasIndex(x => x.StorageFileName).IsUnique();
+        modelBuilder.Entity<MessageAttachment>().HasIndex(x => new { x.MessageId, x.ExternalId });
+        modelBuilder.Entity<MessageReaction>().HasIndex(x => new { x.MessageId, x.ActorKey }).IsUnique();
+        modelBuilder.Entity<PushDevice>().HasIndex(x => x.FirebaseToken).IsUnique();
+
+        modelBuilder.Entity<Chat>()
+            .Property(x => x.Kind)
+            .HasConversion<string>();
+
+        modelBuilder.Entity<Message>()
+            .Property(x => x.Direction)
+            .HasConversion<string>();
+
+        modelBuilder.Entity<Message>()
+            .Property(x => x.DeliveryState)
+            .HasConversion<string>();
+
+        modelBuilder.Entity<MessageAttachment>()
+            .Property(x => x.Kind)
+            .HasConversion<string>();
+
+        modelBuilder.Entity<Message>()
+            .HasMany(x => x.Attachments)
+            .WithOne(x => x.Message)
+            .HasForeignKey(x => x.MessageId)
+            .OnDelete(DeleteBehavior.Cascade);
+
+        modelBuilder.Entity<Message>()
+            .HasMany(x => x.Reactions)
+            .WithOne(x => x.Message)
+            .HasForeignKey(x => x.MessageId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}
diff --git a/server/QMax.Api/Program.cs b/server/QMax.Api/Program.cs
index 2373b07..d6f948c 100644
--- a/server/QMax.Api/Program.cs
+++ b/server/QMax.Api/Program.cs
@@ -161,6 +161,8 @@ static async Task EnsureCompatibilitySchemaAsync(QMaxDbContext db)
     }
 
     await RemoveDuplicateMessageAttachmentsAsync(db);
+    await QMaxDatabaseCleanup.RemoveLegacyWebFileAttachmentEchoesAsync(db);
+    await QMaxDatabaseCleanup.ClearUnreadCountsForLatestOutgoingChatsAsync(db);
     await db.Database.ExecuteSqlRawAsync("DROP INDEX IF EXISTS IX_MessageAttachments_MessageId_ExternalId;");
     await db.Database.ExecuteSqlRawAsync("""
         CREATE UNIQUE INDEX IF NOT EXISTS IX_MessageAttachments_MessageId_ExternalId
diff --git a/tests/QMax.Tests/ApiSmokeTests.cs b/tests/QMax.Tests/ApiSmokeTests.cs
index 59286df..565fa58 100644
--- a/tests/QMax.Tests/ApiSmokeTests.cs
+++ b/tests/QMax.Tests/ApiSmokeTests.cs
@@ -712,7 +712,7 @@ public sealed class ApiSmokeTests : IDisposable
             {
                 Message = message,
                 OriginalFileName = "sent-photo.jpg",
-                StorageFileName = "sent-photo.jpg",
+                StorageFileName = $"{Guid.NewGuid():N}-sent-photo.jpg",
                 ContentType = "image/jpeg",
                 FileSizeBytes = 1024,
                 Kind = AttachmentKind.Image
@@ -791,6 +791,94 @@ public sealed class ApiSmokeTests : IDisposable
         }
     }
 
+    [Fact]
+    public async Task DatabaseCleanupRemovesLegacyWebFileAttachmentDuplicateAndClearsSelfUnread()
+    {
+        var databasePath = Path.Combine(Path.GetTempPath(), $"qmax-legacy-web-file-test-{Guid.NewGuid():N}.db");
+        var dbOptions = new DbContextOptionsBuilder<QMaxDbContext>()
+            .UseSqlite($"Data Source={databasePath};Pooling=False")
+            .Options;
+        var chatId = Guid.NewGuid();
+        const string attachmentHash = "same-photo-sha";
+        var legacySentAt = DateTimeOffset.UtcNow.AddMinutes(-40);
+
+        try
+        {
+            await using (var db = new QMaxDbContext(dbOptions))
+            {
+                await db.Database.EnsureCreatedAsync();
+                db.Chats.Add(new Chat
+                {
+                    Id = chatId,
+                    Title = "Legacy Photo",
+                    LastMessagePreview = "\u041c\u0435\u0434\u0438\u0430",
+                    LastMessageAt = legacySentAt.AddMinutes(30),
+                    UnreadCount = 2
+                });
+
+                var legacyMessage = new Message
+                {
+                    ChatId = chatId,
+                    ExternalId = "web-file-123",
+                    Direction = MessageDirection.Outgoing,
+                    SentAt = legacySentAt,
+                    DeliveryState = MessageDeliveryState.Sent
+                };
+                legacyMessage.Attachments.Add(new MessageAttachment
+                {
+                    OriginalFileName = "legacy.jpg",
+                    StorageFileName = $"{Guid.NewGuid():N}.jpg",
+                    ContentType = "image/jpeg",
+                    FileSizeBytes = 10,
+                    Sha256 = attachmentHash,
+                    Kind = AttachmentKind.Image
+                });
+
+                var confirmedMessage = new Message
+                {
+                    ChatId = chatId,
+                    ExternalId = "domhist:real-photo",
+                    Direction = MessageDirection.Outgoing,
+                    SentAt = legacySentAt.AddMinutes(30),
+                    DeliveryState = MessageDeliveryState.Sent
+                };
+                confirmedMessage.Attachments.Add(new MessageAttachment
+                {
+                    OriginalFileName = "confirmed.jpg",
+                    StorageFileName = $"{Guid.NewGuid():N}.jpg",
+                    ContentType = "image/jpeg",
+                    FileSizeBytes = 10,
+                    Sha256 = attachmentHash,
+                    Kind = AttachmentKind.Image
+                });
+
+                db.Messages.AddRange(legacyMessage, confirmedMessage);
+                await db.SaveChangesAsync();
+            }
+
+            await using (var cleanupDb = new QMaxDbContext(dbOptions))
+            {
+                await QMaxDatabaseCleanup.RemoveLegacyWebFileAttachmentEchoesAsync(cleanupDb);
+                await QMaxDatabaseCleanup.ClearUnreadCountsForLatestOutgoingChatsAsync(cleanupDb);
+            }
+
+            await using var verifyDb = new QMaxDbContext(dbOptions);
+            var messages = await verifyDb.Messages
+                .Where(message => message.ChatId == chatId)
+                .ToListAsync();
+            Assert.DoesNotContain(messages, message => message.ExternalId == "web-file-123");
+            Assert.Contains(messages, message => message.ExternalId == "domhist:real-photo");
+
+            var chat = await verifyDb.Chats.FindAsync(chatId);
+            Assert.NotNull(chat);
+            Assert.Equal(0, chat!.UnreadCount);
+        }
+        finally
+        {
+            DeleteSqliteDatabase(databasePath);
+        }
+    }
+
     [Fact]
     public async Task AdminStatusRequiresPairingCode()
     {
@@ -832,9 +920,14 @@ public sealed class ApiSmokeTests : IDisposable
     public void Dispose()
     {
         _factory.Dispose();
+        DeleteSqliteDatabase(_databasePath);
+    }
+
+    private static void DeleteSqliteDatabase(string databasePath)
+    {
         foreach (var suffix in new[] { "", "-shm", "-wal" })
         {
-            var path = _databasePath + suffix;
+            var path = databasePath + suffix;
             if (File.Exists(path))
             {
                 File.Delete(path);