early merge of #32940

Content.Server/Chat/Managers/ChatSanitizationManager.cs

@@ -35,7 +35,7 @@ public sealed class ChatSanitizationManager : IChatSanitizationManager
         { ":D", "chatsan-smiles-widely" },
         { "D:", "chatsan-frowns-deeply" },
         { ":O", "chatsan-surprised" },
-        { ":3", "chatsan-smiles" }, //nope
+        { ":3", "chatsan-smiles" },
         { ":S", "chatsan-uncertain" },
         { ":>", "chatsan-grins" },
         { ":<", "chatsan-pouts" },

Content.Server/Chat/Systems/ChatSystem.cs

@@ -756,8 +756,9 @@ private bool CanSendInGame(string message, IConsoleShell? shell = null, ICommonS
     // ReSharper disable once InconsistentNaming
     private string SanitizeInGameICMessage(EntityUid source, string message, out string? emoteStr, bool capitalize = true, bool punctuate = false, bool capitalizeTheWordI = true)
     {
-        var newMessage = message.Trim();
-        newMessage = SanitizeMessageReplaceWords(newMessage);
+        var newMessage = SanitizeMessageReplaceWords(message.Trim());
+
+        GetRadioKeycodePrefix(source, newMessage, out newMessage, out var prefix);
 
         // Sanitize it first as it might change the word order
         _sanitizer.TrySanitizeEmoteShorthands(newMessage, source, out newMessage, out emoteStr);
@@ -769,7 +770,7 @@ private string SanitizeInGameICMessage(EntityUid source, string message, out str
         if (punctuate)
             newMessage = SanitizeMessagePeriod(newMessage);
 
-        return newMessage;
+        return prefix + newMessage;
     }
 
     private string SanitizeInGameOOCMessage(string message)

Content.Shared/Chat/SharedChatSystem.cs

@@ -85,6 +85,35 @@ public SpeechVerbPrototype GetSpeechVerb(EntityUid source, string message, Speec
         return current ?? _prototypeManager.Index<SpeechVerbPrototype>(speech.SpeechVerb);
     }
 
+    /// <summary>
+    /// Splits the input message into a radio prefix part and the rest to preserve it during sanitization.
+    /// </summary>
+    /// <remarks>
+    /// This is primarily for the chat emote sanitizer, which can match against ":b" as an emote, which is a valid radio keycode.
+    /// </remarks>
+    public void GetRadioKeycodePrefix(EntityUid source,
+        string input,
+        out string output,
+        out string prefix)
+    {
+        prefix = string.Empty;
+        output = input;
+
+        // If the string is less than 2, then it's probably supposed to be an emote.
+        // No one is sending empty radio messages!
+        if (input.Length <= 2)
+            return;
+
+        if (!(input.StartsWith(RadioChannelPrefix) || input.StartsWith(RadioChannelAltPrefix)))
+            return;
+
+        if (!_keyCodes.TryGetValue(input[1], out _))
+            return;
+
+        prefix = input[..2];
+        output = input[2..];
+    }
+
     /// <summary>
     ///     Attempts to resolve radio prefixes in chat messages (e.g., remove a leading ":e" and resolve the requested
     ///     channel. Returns true if a radio message was attempted, even if the channel is invalid.