feat: enhance message broadcasting to exclude sender's connection and improve IRC compliance

src/EchoHub.Core/Contracts/IChatBroadcaster.cs

@@ -4,7 +4,14 @@ namespace EchoHub.Core.Contracts;
 
 public interface IChatBroadcaster
 {
-    Task SendMessageToChannelAsync(string channelName, MessageDto message);
+    /// <summary>
+    /// Broadcast a chat message to a channel. <paramref name="excludeConnectionId"/> is the
+    /// connection the message originated from (IRC convention: never echo a message back to
+    /// the connection that sent it — its client already displayed it locally). Other
+    /// connections of the same user (e.g. an IRC session alongside a TUI session) still
+    /// receive the message.
+    /// </summary>
+    Task SendMessageToChannelAsync(string channelName, MessageDto message, string? excludeConnectionId = null);
     Task SendUserJoinedAsync(string channelName, string username, UserPresenceDto? presence, string? excludeConnectionId = null);
     Task SendUserLeftAsync(string channelName, string username);
     Task SendChannelUpdatedAsync(ChannelDto channel, string? channelName = null);

src/EchoHub.Core/Contracts/IChatService.cs

@@ -13,8 +13,10 @@ public interface IChatService
     Task<(List<MessageDto> History, string? Error, bool PasswordRequired)> JoinChannelAsync(string connectionId, Guid userId, string username, string channelName, string? password = null);
     Task LeaveChannelAsync(string connectionId, string username, string channelName);
 
-    // Messaging
+    // Messaging. originConnectionId identifies the connection the message came from so
-    Task<string?> SendMessageAsync(Guid userId, string username, string channelName, string content);
+    // broadcasters can avoid echoing it back to that one connection (IRC convention);
+    // the sender's other sessions still receive it.
+    Task<string?> SendMessageAsync(Guid userId, string username, string channelName, string content, string? originConnectionId = null);
     Task<List<MessageDto>> GetChannelHistoryAsync(string channelName, int count, int offset = 0);
 
     // Presence

src/EchoHub.Server.Irc/IrcBroadcaster.cs

@@ -14,7 +14,7 @@ public class IrcBroadcaster : IChatBroadcaster
         _encryption = encryption;
     }
 
-    public async Task SendMessageToChannelAsync(string channelName, MessageDto message)
+    public async Task SendMessageToChannelAsync(string channelName, MessageDto message, string? excludeConnectionId = null)
     {
         // Decrypt transport-encrypted content for IRC clients (they can't handle
         // app-layer encryption). E2E room ciphertext ($RC1$) passes through untouched.
@@ -23,8 +23,11 @@ public class IrcBroadcaster : IChatBroadcaster
 
         foreach (var conn in _gateway.GetConnectionsInChannel(channelName))
         {
-            // IRC convention: don't echo sender's own message
+            // IRC convention: don't echo a message back to the connection that sent it
-            if (conn.Nickname == message.SenderUsername)
+            // (its client already displayed it locally). Match by connection id, not
+            // nickname — the same account may also be online via the TUI or a second
+            // IRC client, and those sessions must still receive the message.
+            if (conn.ConnectionId == excludeConnectionId)
                 continue;
 
             foreach (var line in lines)

src/EchoHub.Server.Irc/IrcCommandHandler.cs

@@ -486,7 +486,7 @@ public sealed class IrcCommandHandler
         if (channelName is null) return;
 
         var error = await _chatService.SendMessageAsync(
-            _conn.UserId!.Value, _conn.Nickname!, channelName, content);
+            _conn.UserId!.Value, _conn.Nickname!, channelName, content, _conn.ConnectionId);
 
         if (error is not null)
         {

src/EchoHub.Server/Hubs/ChatHub.cs

@@ -103,7 +103,7 @@ public class ChatHub : Hub<IEchoHubClient>
     {
         try
         {
-            var error = await _chatService.SendMessageAsync(CurrentUserId, CurrentUsername, channelName, content);
+            var error = await _chatService.SendMessageAsync(CurrentUserId, CurrentUsername, channelName, content, Context.ConnectionId);
             if (error is not null)
                 await Clients.Caller.Error(error);
         }

src/EchoHub.Server/Services/ChatService.cs

@@ -151,7 +151,7 @@ public class ChatService : IChatService
         _logger.LogInformation("{User} left channel '{Channel}'", username, channelName);
     }
 
-    public async Task<string?> SendMessageAsync(Guid userId, string username, string channelName, string content)
+    public async Task<string?> SendMessageAsync(Guid userId, string username, string channelName, string content, string? originConnectionId = null)
     {
         channelName = channelName.ToLowerInvariant().Trim();
 
@@ -240,7 +240,7 @@ public class ChatService : IChatService
             Embeds: embeds,
             SenderDisplayName: sender?.DisplayName);
 
-        await BroadcastToAllAsync(b => b.SendMessageToChannelAsync(channelName, messageDto));
+        await BroadcastToAllAsync(b => b.SendMessageToChannelAsync(channelName, messageDto, originConnectionId));
 
         _logger.LogDebug("{User} sent message in '{Channel}'", username, channelName);
         return null;

src/EchoHub.Server/Services/SignalRBroadcaster.cs

@@ -20,7 +20,9 @@ public class SignalRBroadcaster : IChatBroadcaster
         _presenceTracker = presenceTracker;
     }
 
-    public Task SendMessageToChannelAsync(string channelName, MessageDto message)
+    // The exclusion only applies to the IRC gateway (SignalR clients render their own
+    // message from the broadcast echo), so the id is ignored here.
+    public Task SendMessageToChannelAsync(string channelName, MessageDto message, string? excludeConnectionId = null)
         => HubContext.Clients.Group(channelName).ReceiveMessage(message);
 
     public Task SendUserJoinedAsync(string channelName, string username, UserPresenceDto? presence, string? excludeConnectionId = null)

src/EchoHub.Tests/Irc/IrcBroadcasterTests.cs

@@ -111,23 +111,40 @@ public class IrcBroadcasterTests
     }
 
     [Fact]
-    public async Task SendMessage_SkipsSender()
+    public async Task SendMessage_SkipsOnlyOriginConnection()
     {
-        var (_, aliceStream) = AddConnectionWithCapture("alice", "general");
+        var (aliceConn, aliceStream) = AddConnectionWithCapture("alice", "general");
         var (_, bobStream) = AddConnectionWithCapture("bob", "general");
 
         var message = new MessageDto(
             Guid.NewGuid(), _encryption.Encrypt("Hi"), "alice", null, "general", DateTimeOffset.UtcNow);
 
-        await _broadcaster.SendMessageToChannelAsync("general", message);
+        await _broadcaster.SendMessageToChannelAsync("general", message, aliceConn.ConnectionId);
 
-        // Alice (sender) should NOT receive the message
+        // The connection that sent it should NOT get an echo
         Assert.Empty(aliceStream.GetOutputLines());
 
         // Bob should receive it
         Assert.NotEmpty(bobStream.GetOutputLines());
     }
 
+    [Fact]
+    public async Task SendMessage_SendersOtherSessionsStillReceive()
+    {
+        // Same account online twice (e.g. TUI + IRC, or two IRC clients): a message sent
+        // from one session must still reach the other — skipping by nickname used to
+        // swallow these until the IRC client reconnected.
+        var (_, ircStream) = AddConnectionWithCapture("alice", "general");
+
+        var message = new MessageDto(
+            Guid.NewGuid(), _encryption.Encrypt("sent from the TUI"), "alice", null, "general", DateTimeOffset.UtcNow);
+
+        // Origin is a SignalR connection, not this IRC one
+        await _broadcaster.SendMessageToChannelAsync("general", message, "signalr-conn-123");
+
+        Assert.Contains(ircStream.GetOutputLines(), l => l.Contains("sent from the TUI"));
+    }
+
     [Fact]
     public async Task SendMessage_OnlySendsToChannelMembers()
     {

src/EchoHub.Tests/Irc/TestHelpers.cs

@@ -188,7 +188,7 @@ internal sealed class FakeChatService : IChatService
         return Task.CompletedTask;
     }
 
-    public Task<string?> SendMessageAsync(Guid userId, string username, string channelName, string content)
+    public Task<string?> SendMessageAsync(Guid userId, string username, string channelName, string content, string? originConnectionId = null)
     {
         SentMessages.Add((channelName, content));
         return Task.FromResult(SendMessageError);