feat: implement link embed functionality to enhance message previews with metadata and thumbnails

src/EchoHub.Client/UI/ChatRenderer.cs

@@ -455,6 +455,9 @@ public static partial class ChatColors
     public static readonly Attribute SystemAttr = new(new Color(0, 180, 180), Color.Black);
     public static readonly Attribute MentionHighlightAttr = new(Color.White, new Color(80, 40, 0));
     public static readonly Attribute MentionTextAttr = new(new Color(255, 180, 50), Color.Black);
+    public static readonly Attribute EmbedBorderAttr = new(new Color(91, 155, 213), Color.Black);
+    public static readonly Attribute EmbedTitleAttr = new(Color.White, Color.Black);
+    public static readonly Attribute EmbedDescAttr = new(new Color(160, 160, 160), Color.Black);
 
     /// <summary>
     /// Split text around @mentions, giving each @word the MentionTextAttr accent color.

src/EchoHub.Client/UI/MainWindow.cs

@@ -890,6 +890,10 @@ public sealed class MainWindow : Runnable
                     var contText = $"{indent}{contentLines[i].TrimEnd('\r')}";
                     lines.Add(new ChatLine(ChatColors.SplitMentions(contText)));
                 }
+
+                // Render link embed if present
+                if (message.Embed is not null)
+                    lines.AddRange(FormatEmbed(message.Embed, indent));
                 break;
         }
 
@@ -938,4 +942,67 @@ public sealed class MainWindow : Runnable
         segments.AddRange(ChatColors.SplitMentions(suffix));
         return new ChatLine(segments);
     }
+
+    /// <summary>
+    /// Format a link embed as indented chat lines with a left border bar.
+    /// </summary>
+    private static List<ChatLine> FormatEmbed(EmbedDto embed, string indent)
+    {
+        var lines = new List<ChatLine>();
+        const string border = "\u258f "; // ▏ + space
+
+        // Site name
+        if (!string.IsNullOrWhiteSpace(embed.SiteName))
+        {
+            lines.Add(new ChatLine(new List<ChatSegment>
+            {
+                new(indent, null),
+                new(border, ChatColors.EmbedBorderAttr),
+                new(embed.SiteName, ChatColors.EmbedBorderAttr)
+            }));
+        }
+
+        // Title
+        if (!string.IsNullOrWhiteSpace(embed.Title))
+        {
+            lines.Add(new ChatLine(new List<ChatSegment>
+            {
+                new(indent, null),
+                new(border, ChatColors.EmbedBorderAttr),
+                new(embed.Title, ChatColors.EmbedTitleAttr)
+            }));
+        }
+
+        // Description (truncated)
+        if (!string.IsNullOrWhiteSpace(embed.Description))
+        {
+            var desc = embed.Description.Length > 120
+                ? embed.Description[..117] + "..."
+                : embed.Description;
+
+            lines.Add(new ChatLine(new List<ChatSegment>
+            {
+                new(indent, null),
+                new(border, ChatColors.EmbedBorderAttr),
+                new(desc, ChatColors.EmbedDescAttr)
+            }));
+        }
+
+        // ASCII image thumbnail
+        if (!string.IsNullOrWhiteSpace(embed.ImageAscii))
+        {
+            foreach (var artLine in embed.ImageAscii.Split('\n'))
+            {
+                var trimmed = artLine.TrimEnd('\r');
+                if (string.IsNullOrEmpty(trimmed)) continue;
+
+                if (ChatLine.HasColorTags(trimmed))
+                    lines.Add(ChatLine.FromColoredText(indent + border + trimmed));
+                else
+                    lines.Add(new ChatLine(indent + border + trimmed));
+            }
+        }
+
+        return lines;
+    }
 }

src/EchoHub.Core/Constants/HubConstants.cs

@@ -13,4 +13,11 @@ public static class HubConstants
     public const int AsciiArtWidth = 80;
     public const int AsciiArtHeight = 40;
     public const int AsciiArtHeightHalfBlock = 80;
+
+    // Link embed constants
+    public const int EmbedThumbnailWidth = 24;
+    public const int EmbedThumbnailHeight = 12;
+    public const int EmbedMaxDescriptionLength = 200;
+    public const int EmbedMaxHtmlBytes = 64 * 1024; // 64 KB
+    public const int EmbedFetchTimeoutSeconds = 3;
 }

src/EchoHub.Core/DTOs/ChatDtos.cs

@@ -11,7 +11,8 @@ public record MessageDto(
     MessageType Type,
     string? AttachmentUrl,
     string? AttachmentFileName,
-    DateTimeOffset SentAt);
+    DateTimeOffset SentAt,
+    EmbedDto? Embed = null);
 
 public record ChannelDto(
     Guid Id,
@@ -36,3 +37,10 @@ public record CreateChannelRequest(string Name, string? Topic = null, bool IsPub
 public record UpdateTopicRequest(string? Topic);
 
 public record SendUrlRequest(string Url);
+
+public record EmbedDto(
+    string? SiteName,
+    string? Title,
+    string? Description,
+    string? ImageAscii,
+    string Url);

src/EchoHub.Core/Models/Message.cs

@@ -7,6 +7,7 @@ public class Message
     public MessageType Type { get; set; } = MessageType.Text;
     public string? AttachmentUrl { get; set; }
     public string? AttachmentFileName { get; set; }
+    public string? EmbedJson { get; set; }
     public DateTimeOffset SentAt { get; set; } = DateTimeOffset.UtcNow;
 
     public Guid ChannelId { get; set; }

src/EchoHub.Server.Irc/IrcMessageFormatter.cs

@@ -23,6 +23,10 @@ public static partial class IrcMessageFormatter
             case MessageType.Text:
                 foreach (var chunk in SplitMessage(message.Content, MaxIrcLineContentBytes))
                     lines.Add($"{prefix} PRIVMSG {ircChannel} :{chunk}");
+
+                // Append embed preview if present
+                if (message.Embed is not null)
+                    lines.AddRange(FormatEmbed(prefix, ircChannel, message.Embed));
                 break;
 
             case MessageType.Image:
@@ -46,6 +50,33 @@ public static partial class IrcMessageFormatter
         return lines;
     }
 
+    /// <summary>
+    /// Format a link embed as IRC PRIVMSG lines (text-only, no ASCII thumbnail).
+    /// </summary>
+    private static List<string> FormatEmbed(string prefix, string ircChannel, EmbedDto embed)
+    {
+        var lines = new List<string>();
+
+        var header = new List<string>();
+        if (!string.IsNullOrWhiteSpace(embed.SiteName))
+            header.Add(embed.SiteName);
+        if (!string.IsNullOrWhiteSpace(embed.Title))
+            header.Add(embed.Title);
+
+        if (header.Count > 0)
+            lines.Add($"{prefix} PRIVMSG {ircChannel} :\u2502 {string.Join(" \u2014 ", header)}");
+
+        if (!string.IsNullOrWhiteSpace(embed.Description))
+        {
+            var desc = embed.Description.Length > 200
+                ? embed.Description[..197] + "..."
+                : embed.Description;
+            lines.Add($"{prefix} PRIVMSG {ircChannel} :\u2502 {desc}");
+        }
+
+        return lines;
+    }
+
     /// <summary>
     /// Convert printable color tags ({F:RRGGBB}, {B:RRGGBB}, {X}) to ANSI escape codes for IRC clients.
     /// Also passes through content that already uses ANSI codes unchanged.

src/EchoHub.Server/Controllers/AuthController.cs

@@ -22,6 +22,7 @@ public class AuthController : ControllerBase
         _db = db;
         _jwt = jwt;
     }
+
     [HttpPost("register")]
     public async Task<IActionResult> Register([FromBody] RegisterRequest request)
     {

src/EchoHub.Server/Controllers/ChannelsController.cs

@@ -37,6 +37,7 @@ public class ChannelsController : ControllerBase
         _httpClientFactory = httpClientFactory;
         _chatService = chatService;
     }
+
     [HttpGet]
     public async Task<IActionResult> GetChannels([FromQuery] int offset = 0, [FromQuery] int limit = 50)
     {

src/EchoHub.Server/Controllers/FilesController.cs

@@ -18,6 +18,7 @@ public class FilesController : ControllerBase
     {
         _fileStorage = fileStorage;
     }
+
     [HttpGet("{fileId}")]
     public IActionResult GetFile(string fileId)
     {

src/EchoHub.Server/Controllers/ServerController.cs

@@ -17,6 +17,7 @@ public class ServerController : ControllerBase
         _db = db;
         _config = config;
     }
+
     [HttpGet("info")]
     public async Task<IActionResult> GetInfo()
     {

src/EchoHub.Server/Controllers/UsersController.cs

@@ -24,6 +24,7 @@ public class UsersController : ControllerBase
         _db = db;
         _asciiService = asciiService;
     }
+
     [HttpGet("{username}/profile")]
     public async Task<IActionResult> GetProfile(string username)
     {

src/EchoHub.Server/Data/EchoHubDbContext.cs

@@ -59,6 +59,7 @@ public class EchoHubDbContext : DbContext
             entity.Property(m => m.SenderUsername).IsRequired().HasMaxLength(50);
             entity.Property(m => m.AttachmentUrl).HasMaxLength(500);
             entity.Property(m => m.AttachmentFileName).HasMaxLength(255);
+            entity.Property(m => m.EmbedJson).HasMaxLength(8000);
         });
 
         modelBuilder.Entity<ChannelMembership>(entity =>

src/EchoHub.Server/Data/Migrations/20260219201704_AddMessageEmbed.Designer.cs

@@ -0,0 +1,264 @@
+// <auto-generated />
+using System;
+using EchoHub.Server.Data;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+#nullable disable
+
+namespace EchoHub.Server.Data.Migrations
+{
+    [DbContext(typeof(EchoHubDbContext))]
+    [Migration("20260219201704_AddMessageEmbed")]
+    partial class AddMessageEmbed
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder.HasAnnotation("ProductVersion", "10.0.3");
+
+            modelBuilder.Entity("EchoHub.Core.Models.Channel", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("CreatedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<Guid>("CreatedByUserId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("IsPublic")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Topic")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Name")
+                        .IsUnique();
+
+                    b.ToTable("Channels");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.ChannelMembership", b =>
+                {
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<Guid>("ChannelId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("JoinedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("UserId", "ChannelId");
+
+                    b.HasIndex("ChannelId");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("ChannelMemberships");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.Message", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("AttachmentFileName")
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("AttachmentUrl")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT");
+
+                    b.Property<Guid>("ChannelId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Content")
+                        .IsRequired()
+                        .HasMaxLength(2000)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("EmbedJson")
+                        .HasMaxLength(8000)
+                        .HasColumnType("TEXT");
+
+                    b.Property<Guid>("SenderUserId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("SenderUsername")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("SentAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("Type")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ChannelId");
+
+                    b.HasIndex("SentAt");
+
+                    b.ToTable("Messages");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.RefreshToken", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("CreatedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<long>("ExpiresAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<long?>("RevokedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("TokenHash")
+                        .IsRequired()
+                        .HasMaxLength(128)
+                        .HasColumnType("TEXT");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TokenHash");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("RefreshTokens");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.User", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("AvatarAscii")
+                        .HasMaxLength(10000)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Bio")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("CreatedAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("DisplayName")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("IsBanned")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<bool>("IsMuted")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<long>("LastSeenAt")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<long?>("MutedUntil")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("NicknameColor")
+                        .HasMaxLength(7)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<int>("Role")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("Status")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("StatusMessage")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Username")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Username")
+                        .IsUnique();
+
+                    b.ToTable("Users");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.ChannelMembership", b =>
+                {
+                    b.HasOne("EchoHub.Core.Models.Channel", null)
+                        .WithMany()
+                        .HasForeignKey("ChannelId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("EchoHub.Core.Models.User", null)
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.Message", b =>
+                {
+                    b.HasOne("EchoHub.Core.Models.Channel", "Channel")
+                        .WithMany("Messages")
+                        .HasForeignKey("ChannelId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Channel");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.RefreshToken", b =>
+                {
+                    b.HasOne("EchoHub.Core.Models.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("EchoHub.Core.Models.Channel", b =>
+                {
+                    b.Navigation("Messages");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

src/EchoHub.Server/Data/Migrations/20260219201704_AddMessageEmbed.cs

@@ -0,0 +1,29 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace EchoHub.Server.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddMessageEmbed : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "EmbedJson",
+                table: "Messages",
+                type: "TEXT",
+                maxLength: 8000,
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "EmbedJson",
+                table: "Messages");
+        }
+    }
+}

src/EchoHub.Server/Data/Migrations/EchoHubDbContextModelSnapshot.cs

@@ -91,6 +91,10 @@ namespace EchoHub.Server.Data.Migrations
                         .HasMaxLength(2000)
                         .HasColumnType("TEXT");
 
+                    b.Property<string>("EmbedJson")
+                        .HasMaxLength(8000)
+                        .HasColumnType("TEXT");
+
                     b.Property<Guid>("SenderUserId")
                         .HasColumnType("TEXT");
 

src/EchoHub.Server/Program.cs

@@ -106,6 +106,7 @@ while (true)
         builder.Services.AddSingleton<PresenceTracker>();
         builder.Services.AddSingleton<ImageToAsciiService>();
         builder.Services.AddSingleton<FileStorageService>();
+        builder.Services.AddSingleton<LinkEmbedService>();
         builder.Services.AddHostedService<ServerDirectoryService>();
 
         // ── Chat Service + Broadcasters ─────────────────────────────────────
@@ -121,6 +122,13 @@ while (true)
             client.MaxResponseContentBufferSize = 10 * 1024 * 1024; // 10 MB
         });
 
+        builder.Services.AddHttpClient("OgFetch", client =>
+        {
+            client.Timeout = TimeSpan.FromSeconds(5);
+            client.MaxResponseContentBufferSize = 256 * 1024; // 256 KB
+            client.DefaultRequestHeaders.UserAgent.ParseAdd("EchoHub/1.0 (Link Preview Bot)");
+        });
+
         // ── Rate Limiting ────────────────────────────────────────────────────
         builder.Services.AddRateLimiter(options =>
         {

src/EchoHub.Server/Services/ChatService.cs

@@ -1,3 +1,4 @@
+using System.Text.Json;
 using EchoHub.Core.Constants;
 using EchoHub.Core.Contracts;
 using EchoHub.Core.DTOs;
@@ -14,17 +15,20 @@ public class ChatService : IChatService
     private readonly IServiceScopeFactory _scopeFactory;
     private readonly PresenceTracker _presenceTracker;
     private readonly IEnumerable<IChatBroadcaster> _broadcasters;
+    private readonly LinkEmbedService _embedService;
     private readonly ILogger<ChatService> _logger;
 
     public ChatService(
         IServiceScopeFactory scopeFactory,
         PresenceTracker presenceTracker,
         IEnumerable<IChatBroadcaster> broadcasters,
+        LinkEmbedService embedService,
         ILogger<ChatService> logger)
     {
         _scopeFactory = scopeFactory;
         _presenceTracker = presenceTracker;
         _broadcasters = broadcasters;
+        _embedService = embedService;
         _logger = logger;
     }
 
@@ -171,6 +175,17 @@ public class ChatService : IChatService
             }
         }
 
+        // Attempt to fetch link embed for URLs in the message
+        EmbedDto? embed = null;
+        try
+        {
+            embed = await _embedService.TryGetEmbedAsync(content);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex, "Failed to fetch link embed for message in '{Channel}'", channelName);
+        }
+
         var message = new Message
         {
             Id = Guid.NewGuid(),
@@ -180,6 +195,7 @@ public class ChatService : IChatService
             ChannelId = channel.Id,
             SenderUserId = userId,
             SenderUsername = username,
+            EmbedJson = embed is not null ? JsonSerializer.Serialize(embed) : null,
         };
 
         db.Messages.Add(message);
@@ -194,7 +210,8 @@ public class ChatService : IChatService
             MessageType.Text,
             null,
             null,
-            message.SentAt);
+            message.SentAt,
+            embed);
 
         await BroadcastToAllAsync(b => b.SendMessageToChannelAsync(channelName, messageDto));
 
@@ -387,26 +404,38 @@ public class ChatService : IChatService
         if (channel is null)
             return [];
 
-        var messages = await db.Messages
+        var raw = await db.Messages
             .Where(m => m.ChannelId == channel.Id)
             .OrderByDescending(m => m.SentAt)
             .Take(count)
             .Join(db.Users,
                 m => m.SenderUserId,
                 u => u.Id,
-                (m, u) => new MessageDto(
-                    m.Id,
-                    m.Content,
-                    m.SenderUsername,
-                    u.NicknameColor,
-                    channelName,
-                    m.Type,
-                    m.AttachmentUrl,
-                    m.AttachmentFileName,
-                    m.SentAt))
+                (m, u) => new { m, u.NicknameColor })
             .ToListAsync();
 
-        messages.Reverse();
-        return messages;
+        raw.Reverse();
+
+        return raw.Select(x =>
+        {
+            EmbedDto? embed = null;
+            if (x.m.EmbedJson is not null)
+            {
+                try { embed = JsonSerializer.Deserialize<EmbedDto>(x.m.EmbedJson); }
+                catch { /* ignore malformed JSON */ }
+            }
+
+            return new MessageDto(
+                x.m.Id,
+                x.m.Content,
+                x.m.SenderUsername,
+                x.NicknameColor,
+                channelName,
+                x.m.Type,
+                x.m.AttachmentUrl,
+                x.m.AttachmentFileName,
+                x.m.SentAt,
+                embed);
+        }).ToList();
     }
 }

src/EchoHub.Server/Services/LinkEmbedService.cs

@@ -0,0 +1,268 @@
+using System.Net;
+using System.Text;
+using System.Text.RegularExpressions;
+using EchoHub.Core.Constants;
+using EchoHub.Core.DTOs;
+using Microsoft.Extensions.Logging;
+
+namespace EchoHub.Server.Services;
+
+public partial class LinkEmbedService
+{
+    private readonly IHttpClientFactory _httpClientFactory;
+    private readonly ImageToAsciiService _asciiService;
+    private readonly ILogger<LinkEmbedService> _logger;
+
+    public LinkEmbedService(
+        IHttpClientFactory httpClientFactory,
+        ImageToAsciiService asciiService,
+        ILogger<LinkEmbedService> logger)
+    {
+        _httpClientFactory = httpClientFactory;
+        _asciiService = asciiService;
+        _logger = logger;
+    }
+
+    /// <summary>
+    /// Detect the first URL in message content and attempt to fetch OG embed data.
+    /// Returns null if no URL found, fetch fails, or no useful OG data.
+    /// Never throws — all errors are caught internally.
+    /// </summary>
+    public async Task<EmbedDto?> TryGetEmbedAsync(string content)
+    {
+        try
+        {
+            var url = ExtractFirstUrl(content);
+            if (url is null)
+                return null;
+
+            if (!Uri.TryCreate(url, UriKind.Absolute, out var uri))
+                return null;
+
+            if (uri.Scheme is not ("http" or "https"))
+                return null;
+
+            if (IsPrivateHost(uri))
+                return null;
+
+            using var cts = new CancellationTokenSource(
+                TimeSpan.FromSeconds(HubConstants.EmbedFetchTimeoutSeconds));
+
+            var client = _httpClientFactory.CreateClient("OgFetch");
+
+            using var request = new HttpRequestMessage(HttpMethod.Get, uri);
+            using var response = await client.SendAsync(request,
+                HttpCompletionOption.ResponseHeadersRead, cts.Token);
+
+            if (!response.IsSuccessStatusCode)
+                return null;
+
+            var contentType = response.Content.Headers.ContentType?.MediaType;
+            if (contentType is null || !contentType.StartsWith("text/html", StringComparison.OrdinalIgnoreCase))
+                return null;
+
+            var html = await ReadLimitedAsync(response, HubConstants.EmbedMaxHtmlBytes, cts.Token);
+            if (string.IsNullOrWhiteSpace(html))
+                return null;
+
+            var ogTags = ParseOgTags(html);
+
+            // Try og:title, fallback to <title> tag
+            var title = ogTags.GetValueOrDefault("title");
+            if (string.IsNullOrWhiteSpace(title))
+            {
+                var titleMatch = TitleTagRegex().Match(html);
+                if (titleMatch.Success)
+                    title = WebUtility.HtmlDecode(titleMatch.Groups[1].Value.Trim());
+            }
+
+            // If no title at all, nothing useful to show
+            if (string.IsNullOrWhiteSpace(title))
+                return null;
+
+            var siteName = ogTags.GetValueOrDefault("site_name");
+            var description = ogTags.GetValueOrDefault("description");
+
+            // Truncate description
+            if (description is not null && description.Length > HubConstants.EmbedMaxDescriptionLength)
+                description = description[..(HubConstants.EmbedMaxDescriptionLength - 3)] + "...";
+
+            // HTML decode text fields
+            title = WebUtility.HtmlDecode(title);
+            siteName = siteName is not null ? WebUtility.HtmlDecode(siteName) : null;
+            description = description is not null ? WebUtility.HtmlDecode(description) : null;
+
+            // Attempt to fetch OG image thumbnail
+            string? imageAscii = null;
+            var imageUrl = ogTags.GetValueOrDefault("image");
+            if (!string.IsNullOrWhiteSpace(imageUrl))
+            {
+                imageAscii = await FetchImageThumbnailAsync(imageUrl, uri, cts.Token);
+            }
+
+            return new EmbedDto(siteName, title, description, imageAscii, url);
+        }
+        catch (OperationCanceledException)
+        {
+            _logger.LogDebug("Embed fetch timed out for message content");
+            return null;
+        }
+        catch (Exception ex)
+        {
+            _logger.LogDebug(ex, "Failed to fetch embed");
+            return null;
+        }
+    }
+
+    private static string? ExtractFirstUrl(string content)
+    {
+        var match = UrlRegex().Match(content);
+        if (!match.Success)
+            return null;
+
+        var url = match.Value;
+
+        // Strip trailing punctuation that's likely not part of the URL
+        url = url.TrimEnd('.', ',', '!', '?', ')', ']', ';', ':');
+
+        return url;
+    }
+
+    private static bool IsPrivateHost(Uri uri)
+    {
+        if (uri.IsLoopback)
+            return true;
+
+        if (IPAddress.TryParse(uri.Host, out var ip))
+        {
+            var bytes = ip.GetAddressBytes();
+            if (bytes.Length == 4)
+            {
+                if (bytes[0] == 10) return true;
+                if (bytes[0] == 172 && bytes[1] >= 16 && bytes[1] <= 31) return true;
+                if (bytes[0] == 192 && bytes[1] == 168) return true;
+                if (bytes[0] == 127) return true;
+                if (bytes[0] == 0) return true;
+            }
+        }
+
+        // Also check hostname-based loopback
+        if (uri.Host.Equals("localhost", StringComparison.OrdinalIgnoreCase))
+            return true;
+
+        return false;
+    }
+
+    private static Dictionary<string, string> ParseOgTags(string html)
+    {
+        var tags = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+
+        // Match: <meta property="og:key" content="value" />
+        foreach (Match match in OgTagRegex().Matches(html))
+        {
+            var key = match.Groups[1].Value;
+            var value = match.Groups[2].Value;
+            tags.TryAdd(key, value);
+        }
+
+        // Match reversed order: <meta content="value" property="og:key" />
+        foreach (Match match in OgTagReversedRegex().Matches(html))
+        {
+            var value = match.Groups[1].Value;
+            var key = match.Groups[2].Value;
+            tags.TryAdd(key, value);
+        }
+
+        return tags;
+    }
+
+    private async Task<string?> FetchImageThumbnailAsync(string imageUrl, Uri pageUri, CancellationToken ct)
+    {
+        try
+        {
+            // Resolve relative image URLs against the page URI
+            if (!Uri.TryCreate(imageUrl, UriKind.Absolute, out var imageUri))
+            {
+                if (!Uri.TryCreate(pageUri, imageUrl, out imageUri))
+                    return null;
+            }
+
+            if (imageUri.Scheme is not ("http" or "https"))
+                return null;
+
+            if (IsPrivateHost(imageUri))
+                return null;
+
+            var client = _httpClientFactory.CreateClient("OgFetch");
+            using var response = await client.GetAsync(imageUri, ct);
+
+            if (!response.IsSuccessStatusCode)
+                return null;
+
+            var contentType = response.Content.Headers.ContentType?.MediaType;
+            if (contentType is null || !contentType.StartsWith("image/", StringComparison.OrdinalIgnoreCase))
+                return null;
+
+            await using var stream = await response.Content.ReadAsStreamAsync(ct);
+
+            // Buffer into a MemoryStream for validation + conversion
+            using var memoryStream = new MemoryStream();
+            await stream.CopyToAsync(memoryStream, ct);
+
+            if (memoryStream.Length == 0 || memoryStream.Length > HubConstants.MaxFileSizeBytes)
+                return null;
+
+            memoryStream.Position = 0;
+
+            if (!FileValidationHelper.IsValidImage(memoryStream))
+                return null;
+
+            memoryStream.Position = 0;
+
+            return _asciiService.ConvertToAscii(memoryStream,
+                HubConstants.EmbedThumbnailWidth,
+                HubConstants.EmbedThumbnailHeight);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogDebug(ex, "Failed to fetch OG image thumbnail from {Url}", imageUrl);
+            return null;
+        }
+    }
+
+    private static async Task<string> ReadLimitedAsync(HttpResponseMessage response, int maxBytes, CancellationToken ct)
+    {
+        await using var stream = await response.Content.ReadAsStreamAsync(ct);
+        var buffer = new byte[maxBytes];
+        var totalRead = 0;
+
+        while (totalRead < maxBytes)
+        {
+            var read = await stream.ReadAsync(buffer.AsMemory(totalRead, maxBytes - totalRead), ct);
+            if (read == 0) break;
+            totalRead += read;
+        }
+
+        // Try to detect encoding from Content-Type, default to UTF-8
+        var charset = response.Content.Headers.ContentType?.CharSet;
+        var encoding = charset is not null
+            ? Encoding.GetEncoding(charset)
+            : Encoding.UTF8;
+
+        return encoding.GetString(buffer, 0, totalRead);
+    }
+
+    [GeneratedRegex(@"https?://[^\s<>""')\]]+", RegexOptions.IgnoreCase)]
+    private static partial Regex UrlRegex();
+
+    [GeneratedRegex(@"<meta\s+[^>]*?property\s*=\s*[""']og:(\w+)[""'][^>]*?content\s*=\s*[""']([^""']*)[""'][^>]*/?>",
+        RegexOptions.IgnoreCase | RegexOptions.Singleline)]
+    private static partial Regex OgTagRegex();
+
+    [GeneratedRegex(@"<meta\s+[^>]*?content\s*=\s*[""']([^""']*)[""'][^>]*?property\s*=\s*[""']og:(\w+)[""'][^>]*/?>",
+        RegexOptions.IgnoreCase | RegexOptions.Singleline)]
+    private static partial Regex OgTagReversedRegex();
+
+    [GeneratedRegex(@"<title[^>]*>([^<]+)</title>", RegexOptions.IgnoreCase)]
+    private static partial Regex TitleTagRegex();
+}