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Fix protocol version tag for stateless server spans (#1810)

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Co-authored-by: Luis Rodriguez <25299418+luisangelrod@users.noreply.github.com>
Co-authored-by: Tarek Mahmoud Sayed <tarekms@ntdev.microsoft.com>
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Luis Rodriguez 2026-08-14 11:40:57 -04:00 • committed by GitHub
commit 8754e19f80
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1 changed files with 112 additions and 2 deletions
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56
tests/ModelContextProtocol.AspNetCore.Tests/MapMcpStreamableHttpTests.cs
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@ -6,7 +6,9 @@ using ModelContextProtocol.Client;
using ModelContextProtocol.Protocol;
using ModelContextProtocol.Server;
using ModelContextProtocol.Tests.Utils;
using OpenTelemetry.Trace;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Net;
using System.Security.Claims;
using System.Threading;
@ -46,6 +48,60 @@ public class MapMcpStreamableHttpTests(ITestOutputHelper outputHelper) : MapMcpT
Assert.Equal("TestCustomRouteServer", mcpClient.ServerInfo.Name);
}
// 2025-11-25 is negotiated through the initialize handshake, so in the (default) stateful configuration
// the session-level NegotiatedProtocolVersion is populated and the client sends a matching
// MCP-Protocol-Version header on every follow-up request. This asserts the span carries the negotiated
// version and that the tagged value agrees with the session's NegotiatedProtocolVersion.
//
// A scenario where the per-request and negotiated versions differ is intentionally not asserted here:
// a single MCP session must not change protocol versions, so the server rejects a follow-up request
// whose header/_meta version differs from the negotiated one, and a conformant client never sends a
// differing header. Reaching that divergence would require a hand-crafted request on an invalid
// (failing) code path and would pin the current ordering of tagging relative to version-change
// validation. Instead the two inputs to the tag are covered independently: the per-request path in
// stateless mode (MapMcpStatelessTests, where NegotiatedProtocolVersion is null at tagging time) and the
// negotiated-only fallback over a header-less transport (DiagnosticTests).
[Fact]
public async Task ServerActivity_TagsNegotiatedProtocolVersion()
{
var activities = new List<Activity>();
string? capturedNegotiatedProtocolVersion = null;
var protocolVersionTool = McpServerTool.Create(
(RequestContext<CallToolRequestParams> context) =>
{
capturedNegotiatedProtocolVersion = context.Server.NegotiatedProtocolVersion;
return "ok";
},
new() { Name = "negotiated-capture-version" });
using (var tracerProvider = OpenTelemetry.Sdk.CreateTracerProviderBuilder()
.AddSource("Experimental.ModelContextProtocol")
.AddInMemoryExporter(activities)
.Build())
{
Builder.Services.AddMcpServer()
.WithHttpTransport(ConfigureStateless)
.WithTools([protocolVersionTool]);
await using var app = Builder.Build();
app.MapMcp();
await app.StartAsync(TestContext.Current.CancellationToken);
await using var client = await ConnectAsync(configureClient: options =>
options.ProtocolVersion = "2025-11-25");
await client.CallToolAsync("negotiated-capture-version", cancellationToken: TestContext.Current.CancellationToken);
}
Assert.Contains(activities, activity =>
activity.DisplayName == "tools/call negotiated-capture-version" &&
activity.Kind == ActivityKind.Server &&
activity.GetTagItem("mcp.protocol.version") as string == "2025-11-25");
Assert.Equal("2025-11-25", capturedNegotiatedProtocolVersion);
}
[Fact]
public async Task StreamableHttpMode_Works_WithRootEndpoint()
{