fix: don't render test's own trace as Linked Trace in HTML report

TUnit.Engine.Tests/HtmlReporterTests.cs

@@ -70,6 +70,48 @@ public async Task PublishArtifactAsync_Is_NoOp_When_MessageBus_Not_Injected()
     }
 
 
+    [Test]
+    public void FilterAdditionalTraceIds_Removes_Primary_Trace_CaseInsensitive()
+    {
+        var primary = "abcdef0123456789abcdef0123456789";
+        var linked = "1111111111111111aaaaaaaaaaaaaaaa";
+        var all = new[] { primary.ToUpperInvariant(), linked };
+
+        var result = HtmlReporter.FilterAdditionalTraceIds(all, primary);
+
+        result.ShouldBe(new[] { linked });
+    }
+
+    [Test]
+    public void FilterAdditionalTraceIds_Returns_Input_When_Primary_Null()
+    {
+        var all = new[] { "aaaa", "bbbb" };
+
+        var result = HtmlReporter.FilterAdditionalTraceIds(all, primaryTraceId: null);
+
+        result.ShouldBeSameAs(all);
+    }
+
+    [Test]
+    public void FilterAdditionalTraceIds_Returns_Input_When_No_Match()
+    {
+        var all = new[] { "aaaa", "bbbb" };
+
+        var result = HtmlReporter.FilterAdditionalTraceIds(all, "cccc");
+
+        result.ShouldBeSameAs(all);
+    }
+
+    [Test]
+    public void FilterAdditionalTraceIds_Returns_Empty_When_Only_Primary()
+    {
+        var primary = "abcdef0123456789abcdef0123456789";
+
+        var result = HtmlReporter.FilterAdditionalTraceIds(new[] { primary }, primary);
+
+        result.ShouldBeEmpty();
+    }
+
     [Test]
     public async Task PublishArtifactAsync_Publishes_With_Correct_SessionUid()
     {

TUnit.Engine/Reporters/Html/HtmlReporter.cs

@@ -268,7 +268,7 @@ private ReportData BuildReportData()
             }
 
 #if NET
-            var additionalTraceIds = TraceRegistry.GetTraceIds(kvp.Key);
+            var additionalTraceIds = FilterAdditionalTraceIds(TraceRegistry.GetTraceIds(kvp.Key), traceId);
             string[]? additionalTraceIdsForResult = additionalTraceIds.Length > 0 ? additionalTraceIds : null;
 #else
             string[]? additionalTraceIdsForResult = null;
@@ -440,6 +440,30 @@ private static void AccumulateStatus(ReportSummary summary, ReportTestResult tes
         }
     }
 
+#if NET
+    // The engine auto-registers the test's own traceId in TraceRegistry for OTLP correlation,
+    // so it shows up in GetTraceIds alongside any user-added traces. Strip it here so the
+    // primary trace (rendered as "Trace Timeline") isn't also rendered as a "Linked Trace".
+    internal static string[] FilterAdditionalTraceIds(string[] allTraceIds, string? primaryTraceId)
+    {
+        if (allTraceIds.Length == 0 || primaryTraceId is null)
+        {
+            return allTraceIds;
+        }
+
+        var filtered = new List<string>(allTraceIds.Length);
+        foreach (var tid in allTraceIds)
+        {
+            if (!string.Equals(tid, primaryTraceId, StringComparison.OrdinalIgnoreCase))
+            {
+                filtered.Add(tid);
+            }
+        }
+
+        return filtered.Count == allTraceIds.Length ? allTraceIds : filtered.ToArray();
+    }
+#endif
+
     private static ReportTestResult ExtractTestResult(string testId, TestNode testNode, string? traceId, string? spanId, int retryAttempt, string[]? additionalTraceIds)
     {
         IProperty? stateProperty = null;