fix: propagate CancellationToken through async MCP tooling and observability call chains (fixes #223)

src/Observability/Hosting/Caching/AgenticTokenCache.cs

@@ -96,7 +96,11 @@ public void RegisterObservability(string agentId, string tenantId, AgenticTokenS
         /// <returns>
         /// The observability token if available; otherwise, <c>null</c>.
         /// </returns>
-        public async Task<string?> GetObservabilityToken(string agentId, string tenantId)
+        public Task<string?> GetObservabilityToken(string agentId, string tenantId)
+            => GetObservabilityToken(agentId, tenantId, CancellationToken.None);
+
+        /// <inheritdoc/>
+        public async Task<string?> GetObservabilityToken(string agentId, string tenantId, CancellationToken cancellationToken)
         {
             if (!_map.TryGetValue($"{agentId}:{tenantId}", out var entry))
                 return null;

src/Observability/Hosting/Caching/IExporterTokenCache.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Microsoft.Agents.A365.Observability.Hosting.Caching
@@ -18,5 +19,10 @@ public interface IExporterTokenCache<T> where T : class
         /// Returns an observability token (cached inside the credential) or null on failure/not registered.
         /// </summary>
         Task<string?> GetObservabilityToken(string agentId, string tenantId);
+
+        /// <summary>
+        /// Returns an observability token (cached inside the credential) or null on failure/not registered, with cancellation support.
+        /// </summary>
+        Task<string?> GetObservabilityToken(string agentId, string tenantId, CancellationToken cancellationToken);
     }
 }

src/Observability/Hosting/Caching/ServiceTokenCache.cs

@@ -122,15 +122,19 @@ public void RegisterObservability(string agentId, string tenantId, string token,
         /// <param name="agentId">The agent identifier.</param>
         /// <param name="tenantId">The tenant identifier.</param>
         /// <returns>The observability token if valid; otherwise, null.</returns>
-        public async Task<string?> GetObservabilityToken(string agentId, string tenantId)
+        public Task<string?> GetObservabilityToken(string agentId, string tenantId)
+            => GetObservabilityToken(agentId, tenantId, CancellationToken.None);
+
+        /// <inheritdoc/>
+        public Task<string?> GetObservabilityToken(string agentId, string tenantId, CancellationToken cancellationToken)
         {
             if (string.IsNullOrWhiteSpace(agentId) || string.IsNullOrWhiteSpace(tenantId))
-                return null;
+                return Task.FromResult<string?>(null);
 
             var key = GetKey(agentId, tenantId);
 
             if (!_map.TryGetValue(key, out var entry))
-                return null;
+                return Task.FromResult<string?>(null);
 
             // Check if token has expired
             if (DateTimeOffset.UtcNow >= entry.ExpiresAt)
@@ -140,10 +144,10 @@ public void RegisterObservability(string agentId, string tenantId, string token,
                 {
                     removedEntry.ClearToken();
                 }
-                return null;
+                return Task.FromResult<string?>(null);
             }
 
-            return await Task.FromResult(entry.Token).ConfigureAwait(false);
+            return Task.FromResult(entry.Token);
         }
 
         /// <summary>

src/Observability/Hosting/ObservabilityServiceCollectionExtensions.cs

@@ -27,7 +27,7 @@ public static IServiceCollection AddAgenticTracingExporter(this IServiceCollecti
                 return new Agent365ExporterOptions
                 {
                     ClusterCategory = clusterCategory ?? "production",
-                    TokenResolver = async (agentId, tenantId) => await cache.GetObservabilityToken(agentId, tenantId)
+                    TokenResolver = (agentId, tenantId, ct) => cache.GetObservabilityToken(agentId, tenantId, ct)
                 };
             });
 
@@ -51,7 +51,7 @@ public static IServiceCollection AddServiceTracingExporter(this IServiceCollecti
                 return new Agent365ExporterOptions
                 {
                     ClusterCategory = clusterCategory ?? "production",
-                    TokenResolver = async (agentId, tenantId) => await cache.GetObservabilityToken(agentId, tenantId).ConfigureAwait(false),
+                    TokenResolver = (agentId, tenantId, ct) => cache.GetObservabilityToken(agentId, tenantId, ct),
                     UseS2SEndpoint = true // Service-to-service uses S2S endpoint
                 };
             });

src/Observability/Runtime/Tracing/Exporters/Agent365Exporter.cs

@@ -72,7 +72,7 @@ public override ExportResult Export(in Batch<Activity> batch)
                     groups: groups,
                     resource: _resource,
                     options: _options,
-                    tokenResolver: (agentId, tenantId) => _options.TokenResolver!(agentId, tenantId),
+                    tokenResolver: (agentId, tenantId, ct) => _options.TokenResolver!(agentId, tenantId, ct),
                     sendAsync: request => _httpClient.SendAsync(request)
                 ).GetAwaiter().GetResult();
             }

src/Observability/Runtime/Tracing/Exporters/Agent365ExporterAsync.cs

@@ -74,8 +74,9 @@ await _core.ExportBatchCoreAsync(
                     groups: groups,
                     resource: this._resource,
                     options: this._options,
-                    tokenResolver: (agentId, tenantId) => this._options.TokenResolver!(agentId, tenantId),
-                    sendAsync: request => this._httpClient.SendAsync(request, cancellationToken)
+                    tokenResolver: (agentId, tenantId, ct) => this._options.TokenResolver!(agentId, tenantId, ct),
+                    sendAsync: request => this._httpClient.SendAsync(request, cancellationToken),
+                    cancellationToken: cancellationToken
                 ).ConfigureAwait(false);
             }
             catch (OperationCanceledException)

src/Observability/Runtime/Tracing/Exporters/Agent365ExporterCore.cs

@@ -13,6 +13,7 @@
 using System.Net.Http;
 using System.Net.Http.Headers;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Microsoft.Agents.A365.Observability.Runtime.Tracing.Exporters
@@ -127,13 +128,15 @@ public string BuildRequestUri(string endpoint, string endpointPath)
         /// <param name="options"></param>
         /// <param name="tokenResolver"></param>
         /// <param name="sendAsync"></param>
+        /// <param name="cancellationToken">A cancellation token to cancel the operation.</param>
         /// <returns></returns>
         public async Task<ExportResult> ExportBatchCoreAsync(
             IEnumerable<(string TenantId, string AgentId, List<Activity> Activities)> groups,
             Resource resource,
             Agent365ExporterOptions options,
-            Func<string, string, Task<string?>> tokenResolver,
-            Func<HttpRequestMessage, Task<HttpResponseMessage>> sendAsync)
+            Func<string, string, CancellationToken, Task<string?>> tokenResolver,
+            Func<HttpRequestMessage, Task<HttpResponseMessage>> sendAsync,
+            CancellationToken cancellationToken = default)
         {
             foreach (var g in groups)
             {
@@ -157,7 +160,7 @@ public async Task<ExportResult> ExportBatchCoreAsync(
                 string? token = null;
                 try
                 {
-                    token = await tokenResolver(agentId, tenantId).ConfigureAwait(false);
+                    token = await tokenResolver(agentId, tenantId, cancellationToken).ConfigureAwait(false);
                     this._logger?.LogDebug("Agent365ExporterCore: Obtained token for agent {AgentId} tenant {TenantId}.", agentId, tenantId);
                 }
                 catch (Exception ex)

src/Observability/Runtime/Tracing/Exporters/Agent365ExporterOptions.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Microsoft.Agents.A365.Observability.Runtime.Tracing.Exporters
@@ -10,7 +11,7 @@ namespace Microsoft.Agents.A365.Observability.Runtime.Tracing.Exporters
     /// Must be fast and non-blocking (use internal caching elsewhere).
     /// Return null/empty to omit the Authorization header.
     /// </summary>
-    public delegate Task<string?> AsyncAuthTokenResolver(string agentId, string tenantId);
+    public delegate Task<string?> AsyncAuthTokenResolver(string agentId, string tenantId, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Delegate used by the exporter to resolve the endpoint host or URL for a given tenant id.

src/Tests/Microsoft.Agents.A365.Observability.Hosting.Tests/Extensions/ObservabilityServiceCollectionExtensionsTests.cs

@@ -121,7 +121,7 @@ public void AddServiceTracingExporter_TokenResolver_CanBeCalled()
         var options = serviceProvider.GetRequiredService<Agent365ExporterOptions>();
 
         // Act
-        var token = options.TokenResolver!("test-agent", "test-tenant");
+        var token = options.TokenResolver!("test-agent", "test-tenant", default);
 
         // Assert
         // Token resolver should not throw (actual token retrieval logic is in the cache)
@@ -139,8 +139,7 @@ public void AddAgenticTracingExporter_TokenResolver_CanBeCalled()
         var options = serviceProvider.GetRequiredService<Agent365ExporterOptions>();
 
         // Act
-        var token = options.TokenResolver!("test-agent", "test-tenant");
-
+        var token = options.TokenResolver!("test-agent", "test-tenant", default);
         // Assert
         // Token resolver should not throw (actual token retrieval logic is in the cache)
         // This just verifies the resolver is wired up

src/Tests/Microsoft.Agents.A365.Observability.Hosting.Tests/ObservabilityBuilderExtensionsTests.cs

@@ -83,7 +83,7 @@ public void AddA365Tracing_WithOpenTelemetryBuilderTrue_AndExporterEnabled_Regis
                     builder.Services.AddSingleton<Agent365ExporterOptions>(sp => new Agent365ExporterOptions
                     {
                         UseS2SEndpoint = false,
-                        TokenResolver = (_, _) => Task.FromResult<string?>("test-token")
+                        TokenResolver = (_, _, _) => Task.FromResult<string?>("test-token")
                     });
                 });
             webHostBuilder.UseStartup<MinimalStartup>();
@@ -160,7 +160,7 @@ public void AddA365Tracing_IHostBuilder_WithOpenTelemetryBuilderTrue_AndExporter
                         builder.Services.AddSingleton<Agent365ExporterOptions>(_ => new Agent365ExporterOptions
                         {
                             UseS2SEndpoint = false,
-                            TokenResolver = (_, _) => Task.FromResult<string?>("test-token")
+                            TokenResolver = (_, _, _) => Task.FromResult<string?>("test-token")
                         });
                     });