diff --git a/DevProxy.Integration.Tests/JsonReporterTests.cs b/DevProxy.Integration.Tests/JsonReporterTests.cs
new file mode 100644
index 000000000..0fd6cb47f
--- /dev/null
+++ b/DevProxy.Integration.Tests/JsonReporterTests.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using DevProxy.Abstractions.Proxy;
+using DevProxy.Plugins.Reporters;
+using DevProxy.Plugins.Reporting;
+using Microsoft.Extensions.Logging.Abstractions;
+using Xunit;
+
+namespace DevProxy.Integration.Tests;
+
+public sealed class JsonReporterTests
+{
+    private sealed class TestJsonReporter() : JsonReporter(NullLogger<JsonReporter>.Instance, new HashSet<UrlToWatch>())
+    {
+        public string? Report(string key, object value) => GetReport(new(key, value));
+    }
+
+    [Fact]
+    public void FileExtension_IsDeterminedPerReport()
+    {
+        var reporter = new TestJsonReporter();
+
+        _ = reporter.Report("UrlDiscoveryPlugin", new UrlDiscoveryPluginReport { Data = ["https://api.contoso.com/*"] });
+        Assert.Equal(".jsonc", reporter.FileExtension);
+
+        _ = reporter.Report("OtherPlugin", new { Value = 1 });
+        Assert.Equal(".json", reporter.FileExtension);
+    }
+}
diff --git a/DevProxy.Plugins/Reporters/JsonReporter.cs b/DevProxy.Plugins/Reporters/JsonReporter.cs
index 716053f13..05fc0d805 100644
--- a/DevProxy.Plugins/Reporters/JsonReporter.cs
+++ b/DevProxy.Plugins/Reporters/JsonReporter.cs
@@ -14,7 +14,8 @@ public class JsonReporter(
     ILogger<JsonReporter> logger,
     ISet<UrlToWatch> urlsToWatch) : BaseReporter(logger, urlsToWatch)
 {
-    private string _fileExtension = ".json";
+    private const string DefaultFileExtension = ".json";
+    private string _fileExtension = DefaultFileExtension;
 
     public override string Name => nameof(JsonReporter);
     public override string FileExtension => _fileExtension;
@@ -23,6 +24,9 @@ protected override string GetReport(KeyValuePair<string, object> report)
     {
         Logger.LogDebug("Serializing report {ReportKey}...", report.Key);
 
+        // Determine the extension per report so that one report's extension doesn't leak into the next
+        _fileExtension = DefaultFileExtension;
+
         var reportData = report.Value;
         if (reportData is IJsonReport jsonReport)
         {