Summary Update.

RelayShared/Services/ChatMessageContent.cs

@@ -1,14 +1,43 @@
 namespace RelayShared.Services;
 
+/// <summary>
+/// The plaintext payload of a chat message before E2E encryption is applied.
+///
+/// Lifecycle of a message:
+///   1. Client builds a ChatMessageContent (text + optional reply/attachment/mentions).
+///   2. Client JSON-serialises it, encrypts with the server's public key (RSA wrapping an
+///      AES-GCM key), and sends the encrypted blob wrapped in a SocketEncryptedMessage.
+///   3. Server decrypts with its private key, re-encrypts with the channel DB key, stores it.
+///   4. For each recipient, server decrypts from DB key and re-encrypts with that recipient's
+///      public key, then delivers via SocketEncryptedMessage.
+///   5. Recipient decrypts with their private key and JSON-deserialises back to ChatMessageContent.
+///
+/// This type is intentionally shared by RelayClient and RelayServer so both ends agree on the
+/// JSON shape. Adding a field here lights up the whole pipeline automatically.
+/// </summary>
 public sealed class ChatMessageContent
 {
+    /// <summary>The raw message body, including Markdown syntax and @mentions.</summary>
     public string Text { get; set; } = string.Empty;
 
+    /// <summary>When set, this message is a reply. Carries the Surreal record id of the message being replied to.</summary>
     public string? ReplyToId { get; set; }
+
+    /// <summary>Display name of the user being replied to. Lets the client render the quote bar without a lookup.</summary>
     public string? ReplyToSenderUsername { get; set; }
+
+    /// <summary>Trimmed preview of the replied-to text (≤100 chars). Captured at send time so the server never has to look it up.</summary>
     public string? ReplyPreview { get; set; }
+
+    /// <summary>Extracted usernames + special tokens ("everyone", "here"). Drives the ping-badge in the sidebar.</summary>
     public List<string>? Mentions { get; set; }
+
+    /// <summary>Base64-encoded attachment bytes. Null when there's no attachment.</summary>
     public string? AttachmentBase64 { get; set; }
+
+    /// <summary>MIME type of the attachment (e.g. "image/png"). Used to choose between BuildBase64ImageEmbed and BuildFileCard.</summary>
     public string? AttachmentMimeType { get; set; }
+
+    /// <summary>Original filename as chosen by the sender. Shown as the file card label and used for the download path.</summary>
     public string? AttachmentFileName { get; set; }
 }