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Fix protocol version tag for stateless server spans #1810

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Fix protocol version tag for stateless server spans #1810

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6a7e83e
Fix protocol version tag for stateless server spans
luisangelrod Aug 10, 2026
2a27e85
Stabilize protocol version activity test
luisangelrod Aug 10, 2026
5109182
test: make protocol version activity assertion parallel-safe
luisangelrod Aug 10, 2026
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5 changes: 3 additions & 2 deletions src/ModelContextProtocol.Core/McpSessionHandler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -962,9 +962,10 @@ private void AddTags(ref TagList tags, Activity? activity, JsonRpcMessage messag
tags.Add("network.protocol.name", "http");
}

if (NegotiatedProtocolVersion is not null)
string? protocolVersion = (message as JsonRpcRequest)?.Context?.ProtocolVersion ?? NegotiatedProtocolVersion;
if (protocolVersion is not null)
{
tags.Add("mcp.protocol.version", NegotiatedProtocolVersion);
tags.Add("mcp.protocol.version", protocolVersion);
}

if (activity is { IsAllDataRequested: true })
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32 changes: 32 additions & 0 deletions tests/ModelContextProtocol.AspNetCore.Tests/MapMcpStatelessTests.cs
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Expand Up @@ -2,6 +2,8 @@
using Microsoft.Extensions.DependencyInjection;
using ModelContextProtocol.Protocol;
using ModelContextProtocol.Server;
using OpenTelemetry.Trace;
using System.Diagnostics;

namespace ModelContextProtocol.AspNetCore.Tests;

Expand All @@ -10,6 +12,36 @@ public class MapMcpStatelessTests(ITestOutputHelper outputHelper) : MapMcpStream
protected override bool UseStreamableHttp => true;
protected override bool Stateless => true;

[Fact]
public async Task ServerActivity_IncludesPerRequestProtocolVersion()
{
var activities = new List<Activity>();

using (var tracerProvider = OpenTelemetry.Sdk.CreateTracerProviderBuilder()
.AddSource("Experimental.ModelContextProtocol")
.AddInMemoryExporter(activities)
.Build())
{
Builder.Services.AddMcpServer()
.WithHttpTransport(ConfigureStateless)
.WithTools([McpServerTool.Create(() => "ok", new() { Name = "test-tool" })]);

await using var app = Builder.Build();
app.MapMcp();
await app.StartAsync(TestContext.Current.CancellationToken);

await using var client = await ConnectAsync(configureClient: options =>
options.ProtocolVersion = McpProtocolVersions.July2026ProtocolVersion);

await client.ListToolsAsync(cancellationToken: TestContext.Current.CancellationToken);
}

Assert.Contains(activities, activity =>
activity.DisplayName == "tools/list" &&
activity.Kind == ActivityKind.Server &&
activity.GetTagItem("mcp.protocol.version") as string == McpProtocolVersions.July2026ProtocolVersion);
}

[Fact]
public async Task EnablePollingAsync_ThrowsInvalidOperationException_InStatelessMode()
{
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