From 224823d778d4a168e2dd6d1cdba8031c4e6520bb Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Tue, 3 Nov 2026 19:11:24 +0000
Subject: [PATCH] Decode MXP entities and take the Pueblo hello out of connect
 screens

TelnetNegotiationCore 4.6.1. The MXP plugin now asks it to decode entities
once MXP mode starts: CoffeeMud escapes every quote from the moment option
91 is agreed, and CoffeeMud Hardcore's screen was stored with &quot; in its
ASCII art.

PuebloProtocol is registered to consume the hello ("This world is Pueblo
1.10 Enhanced." from PennMUSH, "1.0" from TinyMUX and RhostMUSH), which was
stored as the first line of the screen. Nothing is sent back. The hello is
noted as PUEBLO, measured, as MCP's offer is.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rqqt7TucGdYhFwbzK7RHR5
---
 Directory.Packages.props                      |  2 +-
 src/MUI.Crawl/Telnet/TelnetProbe.cs           | 17 +++++++++++
 src/MUI.Crawl/Telnet/WatchedProtocols.cs      |  8 +++++
 .../MUI.Crawl.Tests/Telnet/MxpSupportTests.cs | 25 +++++++++++++++-
 .../Telnet/ProbeSessionTests.cs               | 29 +++++++++++++++++++
 5 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/Directory.Packages.props b/Directory.Packages.props
index 33e51b4..5c63fc3 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -19,7 +19,7 @@
       send in answer to DO COMPRESS2; before it, everything after their connect screens, MSSP report
       included, arrived as zlib read as text.
     -->
-    <PackageVersion Include="TelnetNegotiationCore" Version="4.6.0" />
+    <PackageVersion Include="TelnetNegotiationCore" Version="4.6.1" />
 
     <!--
       No logging, hosting or DI *abstractions* here. The crawler is an in-process BackgroundService in
diff --git a/src/MUI.Crawl/Telnet/TelnetProbe.cs b/src/MUI.Crawl/Telnet/TelnetProbe.cs
index f94356a..803d917 100644
--- a/src/MUI.Crawl/Telnet/TelnetProbe.cs
+++ b/src/MUI.Crawl/Telnet/TelnetProbe.cs
@@ -1642,6 +1642,23 @@ private TelnetInterpreterBuilder Build(
                     return ValueTask.CompletedTask;
                 })
 
+            // Pueblo's hello, "This world is Pueblo 1.10 Enhanced." (PennMUSH) or "1.0" (TinyMUX,
+            // RhostMUSH), is the server's half of a negotiation sent as a line of text, and it was
+            // being stored as the first line of the connect screen. The plugin takes it out of the
+            // stream, the same as MCP's offer above.
+            //
+            // Nothing is sent back. Answering is PUEBLOCLIENT, which is text at a login prompt and
+            // switches the session to HTML; the probe wants the screen a player without Pueblo sees.
+            //
+            // Noted on the offer, as MCP is: the hello is the server saying it speaks Pueblo, and it
+            // is measured rather than declared, beside MSSP's PUEBLO.
+            .AddPlugin<PuebloProtocol>()
+                .OnPuebloOffered(() =>
+                {
+                    Note("PUEBLO");
+                    return ValueTask.CompletedTask;
+                })
+
             // What FlushPendingLineAsync used to do by hand, done on the interpreter's own
             // byte-processing loop where the line buffer has exactly one writer — and, crucially,
             // without pretending the peer sent anything. It retires itself the moment a server
diff --git a/src/MUI.Crawl/Telnet/WatchedProtocols.cs b/src/MUI.Crawl/Telnet/WatchedProtocols.cs
index b3358af..d0a61b8 100644
--- a/src/MUI.Crawl/Telnet/WatchedProtocols.cs
+++ b/src/MUI.Crawl/Telnet/WatchedProtocols.cs
@@ -99,6 +99,13 @@ public override ValueTask OnEnabledAsync()
     /// real screen into the WHO phase. The answer is the truth: this client renders nothing, so every
     /// entry asked about is refused, and a bare <c>&lt;SUPPORT&gt;</c> gets a reply that claims nothing.
     /// It goes out on a secure line, which a server reads as protocol rather than as typing.
+    /// <para>
+    /// Entities are decoded too. A server in MXP mode must escape <c>"</c>, <c>&amp;</c>, <c>&lt;</c>
+    /// and <c>&gt;</c> in its text, and CoffeeMud does from the moment option 91 is agreed, so a client
+    /// that renders nothing stored <c>&amp;quot;</c> wherever the game had printed a quote
+    /// (CoffeeMud Hardcore's connect screen, 2026-11-03). Only after MXP mode starts; before that, an
+    /// entity is text the game meant.
+    /// </para>
     /// </remarks>
     internal sealed class Mxp : MXPProtocol
     {
@@ -108,6 +115,7 @@ public Mxp(Action<string> note)
         {
             _note = note;
             OnMxpSupportRequested(asked => SendSupportsAsync([], asked));
+            DecodeEntities();
         }
 
         public override ValueTask OnEnabledAsync()
diff --git a/tests/MUI.Crawl.Tests/Telnet/MxpSupportTests.cs b/tests/MUI.Crawl.Tests/Telnet/MxpSupportTests.cs
index 7e26a94..d69c2de 100644
--- a/tests/MUI.Crawl.Tests/Telnet/MxpSupportTests.cs
+++ b/tests/MUI.Crawl.Tests/Telnet/MxpSupportTests.cs
@@ -68,6 +68,26 @@ public async Task ASupportQuestionWithNoStartMarkerIsStillAnswered()
         await Assert.That(result.MxpObserved).IsTrue();
     }
 
+    /// <summary>
+    /// Once MXP mode starts, the server escapes its quotes, and the screen is stored with them
+    /// decoded. CoffeeMud Hardcore's ASCII art arrived as <c>.-&amp;quot;&amp;quot;-.</c>.
+    /// </summary>
+    [Test]
+    public async Task EntitiesInTheScreenAreDecoded()
+    {
+        await using var game = new HoldingGame
+        {
+            SendsStartMarker = false,
+            Screen = "  .-&quot;&quot;-.  Welcome to the Holding Pattern &amp; friends\r\nAccount name: ",
+        };
+
+        var result = await new TelnetProbe(Fast()).ProbeAsync(game.Target);
+
+        await Assert.That(result.Outcome).IsEqualTo(ProbeOutcome.Answered);
+        await Assert.That(result.Banner).Contains(".-\"\"-.  Welcome to the Holding Pattern & friends");
+        await Assert.That(result.Banner).DoesNotContain("&quot;");
+    }
+
     /// <summary>
     /// Speaks just enough telnet to agree MXP, start it, and ask; then holds its real screen until it
     /// is answered or the hold runs out, as CoffeeMud does.
@@ -96,6 +116,9 @@ public HoldingGame()
         /// </summary>
         public bool SendsStartMarker { get; init; } = true;
 
+        /// <summary>The screen sent once the hold ends.</summary>
+        public string Screen { get; init; } = "Welcome to the Holding Pattern\r\nAccount name: ";
+
         public ProbeTarget Target => new(
             IPAddress.Loopback.ToString(),
             ((IPEndPoint)_listener.LocalEndpoint).Port);
@@ -136,7 +159,7 @@ private async Task ServeAsync()
                     await Task.Delay(20, _stopping.Token);
                 }
 
-                await SendAsync(stream, "Welcome to the Holding Pattern\r\nAccount name: ");
+                await SendAsync(stream, Screen);
                 await listening;
             }
             catch (OperationCanceledException)
diff --git a/tests/MUI.Crawl.Tests/Telnet/ProbeSessionTests.cs b/tests/MUI.Crawl.Tests/Telnet/ProbeSessionTests.cs
index 94d6ef4..4cc7507 100644
--- a/tests/MUI.Crawl.Tests/Telnet/ProbeSessionTests.cs
+++ b/tests/MUI.Crawl.Tests/Telnet/ProbeSessionTests.cs
@@ -1866,6 +1866,35 @@ await Assert.That(result.Banner!.Trim())
         await Assert.That(result.Negotiation.Supported).Contains("MCP");
     }
 
+    /// <summary>
+    /// A MUSH's Pueblo hello is the server's half of a negotiation, so it is taken out of the connect
+    /// screen and recorded as the game offering Pueblo. Both spellings: PennMUSH names 1.10, TinyMUX
+    /// and RhostMUSH name 1.0.
+    /// </summary>
+    [Test]
+    [Arguments("1.10")]
+    [Arguments("1.0")]
+    public async Task APuebloHelloIsNotPartOfTheConnectScreen(string version)
+    {
+        await using var game = new FakeGame
+        {
+            Banner = $"This world is Pueblo {version} Enhanced.\r\n"
+                + "Welcome to the MUSH.\r\n"
+                + "Type 'connect guest guest' to look around.\r\n",
+            WhoReply = "0 Players logged in.\r\n",
+        };
+
+        var result = await new TelnetProbe(Fast()).ProbeAsync(game.Target);
+
+        await Assert.That(result.Outcome).IsEqualTo(ProbeOutcome.Answered);
+        await Assert.That(result.Banner).DoesNotContain("Pueblo");
+        await Assert.That(result.Banner!.Trim())
+            .IsEqualTo("Welcome to the MUSH.\nType 'connect guest guest' to look around.");
+        await Assert.That(result.Negotiation.Supported).Contains("PUEBLO");
+        await Assert.That(game.Received.Any(line => line.StartsWith("PUEBLOCLIENT", StringComparison.Ordinal))).IsFalse()
+            .Because("answering would switch the session to HTML and type at the login prompt");
+    }
+
     /// <summary>
     /// The offer is evidence that the game speaks MCP, and is recorded as such -- in the quoted
     /// spelling here, and in the unquoted one in