From 82fd409ab53bb61faaf44cd705e36491e44d1e85 Mon Sep 17 00:00:00 2001
From: Nicholas Blumhardt <nblumhardt@nblumhardt.com>
Date: Thu, 9 Apr 2026 09:31:37 +1000
Subject: [PATCH] Detect and drop all-zero trace/span/parent ids

---
 src/SeqCli/Apps/Hosting/AppContainer.cs     | 12 ++++++------
 test/SeqCli.Tests/Apps/AppContainerTests.cs | 14 ++++++++++++++
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/src/SeqCli/Apps/Hosting/AppContainer.cs b/src/SeqCli/Apps/Hosting/AppContainer.cs
index 4b233f1..2f52c58 100644
--- a/src/SeqCli/Apps/Hosting/AppContainer.cs
+++ b/src/SeqCli/Apps/Hosting/AppContainer.cs
@@ -15,6 +15,7 @@
 using System;
 using System.Globalization;
 using System.IO;
+using System.Linq;
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Newtonsoft.Json;
@@ -35,7 +36,7 @@ partial class AppContainer : IAppHost, IDisposable
     readonly SeqApp _seqApp;
     readonly AppLoader _loader;
 
-    static readonly Regex HexDigits = HexDigitsRegex();
+    static readonly Regex NonZeroHex = NonZeroHexRegex();
 
     readonly JsonSerializer _serializer = JsonSerializer.Create(new JsonSerializerSettings
     {
@@ -183,7 +184,7 @@ static bool IsValidHexIdentifier(JToken? value, int requiredChars)
         if (value?.Value<string>() is not { } id)
             return false;
 
-        return id.Length == requiredChars && HexDigits.IsMatch(id);
+        return id.Length == requiredChars && NonZeroHex.IsMatch(id);
     }
 
     public void StartPublishing(TextWriter inputWriter)
@@ -198,7 +199,6 @@ public void StopPublishing()
             pjson.Stop();
     }
 
-    // Technically, 
-    [GeneratedRegex("^[0-9a-f]*$")]
-    private static partial Regex HexDigitsRegex();
-}
\ No newline at end of file
+    [GeneratedRegex("^0*[1-9a-f][0-9a-f]*$")]
+    private static partial Regex NonZeroHexRegex();
+}
diff --git a/test/SeqCli.Tests/Apps/AppContainerTests.cs b/test/SeqCli.Tests/Apps/AppContainerTests.cs
index c316884..e9cfdec 100644
--- a/test/SeqCli.Tests/Apps/AppContainerTests.cs
+++ b/test/SeqCli.Tests/Apps/AppContainerTests.cs
@@ -67,6 +67,20 @@ public void RemovesShortTraceAndSpanIds()
         Assert.Empty(jo);
     }
 
+    [Fact]
+    public void RemovesZeroTraceAndSpanIds()
+    {
+        var jo = new JObject
+        {
+            ["@tr"] = "00000000000000000000000000000000",
+            ["@sp"] = "0000000000000000",
+            ["@ps"] = "0000000000000000"
+        };
+        Assert.NotEmpty(jo);
+        AppContainer.SanitizeTraceIdentifiers(jo);
+        Assert.Empty(jo);
+    }
+
     [Fact]
     public void PreservesValidTraceAndSpanIds()
     {