Improved source links in chats (#827)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Tools/SourceExtensions.cs

@@ -1,13 +1,84 @@
 using System.Text;
+using System.Text.RegularExpressions;
 
 using AIStudio.Tools.PluginSystem;
 
 namespace AIStudio.Tools;
 
-public static class SourceExtensions
+public static partial class SourceExtensions
 {
     private static string TB(string fallbackEN) => I18N.I.T(fallbackEN, typeof(SourceExtensions).Namespace, nameof(SourceExtensions));
 
+    private static void AppendMarkdownLink(StringBuilder sb, string title, string url)
+    {
+        sb.Append('[');
+        sb.Append(EscapeMarkdownLinkText(title));
+        sb.Append("](<");
+        sb.Append(NormalizeLinkDestination(url));
+        sb.Append(">)");
+    }
+
+    private static string EscapeMarkdownLinkText(string text)
+    {
+        return text
+            .Replace(@"\", @"\\")
+            .Replace("[", @"\[")
+            .Replace("]", @"\]")
+            .Replace("\r", " ")
+            .Replace("\n", " ");
+    }
+
+    private static string NormalizeLinkDestination(string url)
+    {
+        var normalized = url.Trim().Replace("\r", string.Empty).Replace("\n", string.Empty);
+        normalized = TryUnwrapMarkdownLink(normalized);
+
+        if (Uri.TryCreate(normalized, UriKind.Absolute, out var absoluteUri))
+            return absoluteUri.GetComponents(UriComponents.AbsoluteUri, UriFormat.UriEscaped);
+
+        var sb = new StringBuilder(normalized.Length);
+        foreach (var c in normalized)
+        {
+            if (IsSafeUrlCharacter(c))
+            {
+                sb.Append(c);
+                continue;
+            }
+
+            sb.Append(Uri.EscapeDataString(c.ToString()));
+        }
+
+        return sb.ToString();
+    }
+
+    private static string TryUnwrapMarkdownLink(string value)
+    {
+        var match = MarkdownLinkWithOptionalSuffix().Match(value);
+        if (!match.Success)
+            return value;
+
+        var label = match.Groups["label"].Value;
+        var url = match.Groups["url"].Value;
+        var suffix = match.Groups["suffix"].Value;
+        if (string.IsNullOrEmpty(suffix))
+            return url;
+
+        if (Uri.TryCreate(label, UriKind.Absolute, out var labelUri) &&
+            Uri.TryCreate(url, UriKind.Absolute, out var urlUri) &&
+            Uri.Compare(labelUri, urlUri, UriComponents.AbsoluteUri, UriFormat.SafeUnescaped, StringComparison.OrdinalIgnoreCase) == 0)
+            return url + suffix;
+
+        return value;
+    }
+
+    private static bool IsSafeUrlCharacter(char c)
+    {
+        if (char.IsAsciiLetterOrDigit(c))
+            return true;
+
+        return c is '-' or '.' or '_' or '~' or ':' or '/' or '?' or '#' or '[' or ']' or '@' or '!' or '$' or '&' or '\'' or '(' or ')' or '*' or '+' or ',' or ';' or '=';
+    }
+    
     /// <summary>
     /// Converts a list of sources to a markdown-formatted string.
     /// </summary>
@@ -36,11 +107,8 @@ public static class SourceExtensions
                     }
                     
                     sb.Append($"- [{++sourceNum}] ");
-                    sb.Append('[');
-                    sb.Append(source.Title);
-                    sb.Append("](");
-                    sb.Append(source.URL);
-                    sb.AppendLine(")");
+                    AppendMarkdownLink(sb, source.Title, source.URL);
+                    sb.AppendLine();
                     break;
             }
         }
@@ -55,11 +123,8 @@ public static class SourceExtensions
         foreach (var source in ragSources)
         {
             sb.Append($"- [{++sourceNum}] ");
-            sb.Append('[');
-            sb.Append(source.Title);
-            sb.Append("](");
-            sb.Append(source.URL);
-            sb.AppendLine(")");
+            AppendMarkdownLink(sb, source.Title, source.URL);
+            sb.AppendLine();
         }
         
         return sb.ToString();
@@ -76,4 +141,7 @@ public static class SourceExtensions
             if (sources.All(s => s.URL != addedSource.URL && s.Title != addedSource.Title))
                 sources.Add((Source)addedSource);
     }
+
+    [GeneratedRegex(@"^\[(?<label>[^\]]+)\]\((?<url>[^)\r\n]+)\)(?<suffix>.*)$")]
+    private static partial Regex MarkdownLinkWithOptionalSuffix();
 }

app/MindWork AI Studio/wwwroot/changelog/v26.6.3.md

@@ -1,4 +1,5 @@
 # v26.6.3, build 243 (2026-06-xx xx:xx UTC)
+- Improved source links in chat answers when file or document names contained spaces, umlauts, or other special characters. Source entries now open much more reliably for documents with names such as PDFs from shared portals or internal knowledge bases.
 - Improved all assistants, so running tasks can continue when you leave the assistant and return later.
 - Improved the assistant overview so it shows which assistants are still running or have a result ready.
 - Improved the activity indicators for running chats and assistants so they use a consistent blue highlight.