Improve streaming timeout handling and keep-alive logic

docs/superpowers/specs/2026-07-31-optional-streaming-timeout-tests-design.md

@@ -0,0 +1,41 @@
+# Optional Streaming Timeout Tests Design
+
+## Scope
+
+Make the five timeout and keep-alive tests added for PR #950 opt-in so they do not run
+automatically with the normal `StreamingResponseTests` suite.
+
+## Design
+
+Add a test-local `OptionalStreamingTimeoutFactAttribute` derived from xUnit's
+`FactAttribute`. The attribute will set `Skip` unless the environment variable
+`XUNITSTREAMINGTIMEOUTTESTENABLED` is exactly `1`.
+
+Apply the attribute to:
+
+- `SendStreamTimedOutNotification_DisablesStreaming_AndFinalResponseIsStillSent`
+- `ChannelStreamingTimeout_UpdatesCheckpointAndFinalMessage`
+- `M365Copilot_IdleStream_SendsConfiguredWorkingNotice`
+- `M365Copilot_TimeoutWithoutText_SendsFinalTimeoutMessage`
+- `M365Copilot_TimeoutWithBufferedText_SendsTerminatingActivitiesAndFinalResponse`
+
+No production code, project configuration, or CI configuration will change.
+
+## Execution
+
+Normal test runs discover the five tests as skipped. Developers can run them explicitly
+from PowerShell with:
+
+```powershell
+$env:XUNITSTREAMINGTIMEOUTTESTENABLED = '1'
+dotnet test src\tests\Microsoft.Agents.Builder.Tests\Microsoft.Agents.Builder.Tests.csproj `
+  --filter "FullyQualifiedName~StreamingResponseTests"
+```
+
+Removing the environment variable restores the default skipped behavior.
+
+## Validation
+
+Run the filtered test class without the environment variable and verify five skipped tests.
+Then run it with the environment variable set and verify all tests pass on both target
+frameworks.

docs/superpowers/specs/2026-07-31-streaming-response-timeout-tests-design.md

@@ -0,0 +1,43 @@
+# Streaming Response Timeout Tests Design
+
+## Scope
+
+Add focused unit coverage to `StreamingResponseTests.cs` for the behaviors identified in
+PR #950's review comment. Production code remains unchanged.
+
+## Test Strategy
+
+The tests will use the existing `TurnContext.StreamingResponse` public surface and mocked
+`IChannelAdapter` operations for observable assertions. Small test-only reflection helpers
+will set private timeout state or duration fields where waiting for the real 35-second or
+105-second thresholds would make the tests slow and unreliable.
+
+Reflection will be limited to named fields on the concrete internal `StreamingResponse`
+instance. Helpers will fail immediately if a field is renamed or cannot be found.
+
+## Coverage
+
+1. Verify `SendStreamTimedOutNotification` sends the supplied stop notification, disables
+   streaming for the turn, and allows subsequently buffered content to be delivered when
+   `EndStreamAsync` completes.
+2. Simulate a channel streaming-timeout response and verify timeout checkpoints and the
+   eventual final message use activity updates rather than creating additional sends.
+3. Force the M365 Copilot working-notice threshold and verify the configured
+   `StreamingTakingTooLongMessage` is emitted as an informative streaming activity.
+4. Force the M365 Copilot overall timeout with no buffered text and verify the timeout
+   message is sent and streaming is disabled.
+5. Force the M365 Copilot overall timeout with buffered text and verify the terminating
+   timeout activities are sent and the buffered final response remains deliverable through
+   the non-streaming path.
+
+## Synchronization and Assertions
+
+Tests will use adapter callbacks and the existing condition-based wait helpers rather than
+fixed sleeps. Assertions will distinguish `SendActivitiesAsync` from `UpdateActivityAsync`,
+inspect activity type and `StreamInfo`, and confirm `IsStreamingChannel` transitions.
+
+## Validation
+
+Run the targeted `Microsoft.Agents.Builder.Tests` project filtered to
+`StreamingResponseTests`. If the target frameworks require separate execution, run the
+supported .NET target that exercises the modified test file.

src/Build.Shared.props

@@ -59,7 +59,7 @@
 
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DefineConstants>TRACE</DefineConstants>
-    <DebugType>pdbonly</DebugType>
+    <DebugType>portable</DebugType>
     <Optimize>true</Optimize>
   </PropertyGroup>
 
@@ -73,7 +73,7 @@
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x64'">
     <DefineConstants>TRACE</DefineConstants>
-    <DebugType>pdbonly</DebugType>
+    <DebugType>portable</DebugType>
     <Optimize>true</Optimize>
     <PlatformTarget>x64</PlatformTarget>
   </PropertyGroup>

src/libraries/Builder/Microsoft.Agents.Builder/IStreamingResponse.cs

@@ -94,6 +94,11 @@ public interface IStreamingResponse
         /// </summary>
         List<ClientCitation>? Citations { get; }
 
+        /// <summary>
+        /// This is the displayed message that is sent to the user when a stream trips one of the timeouts for the channel.
+        /// </summary>
+        string StreamingTakingTooLongMessage { get; set; }
+
         /// <summary>
         /// Adds an attachment to the collection of attachments for the final message.
         /// </summary>
@@ -152,7 +157,6 @@ public interface IStreamingResponse
         /// Queues a chunk of partial message text to be sent to the client.
         /// </summary>
         /// <param name="text">Partial text of the message to send.</param>
-        /// <param name="citations">Citations to include in the message.</param>
         /// <exception cref="System.InvalidOperationException">Throws if the stream has already ended.</exception>
         void QueueTextChunk(string text);
 
@@ -168,5 +172,13 @@ public interface IStreamingResponse
         /// </summary>
         /// <returns>Number of updates sent so far.</returns>
         int UpdatesSent();
+
+        /// <summary>
+        /// Cancels the stream and sends a final message to the client indicating that the stream was cancelled, but does not stop the underlying operation.  This is useful for long-running operations that may be cancelled by the user or timeout, but should continue to run in the background.
+        /// </summary>
+        /// <param name="Message">Message that will be sent to the client indicating the stream was cancelled.</param>
+        /// <param name="cancellationToken"></param>
+        /// <returns>True if the stream was successfully cancelled, false otherwise.</returns>
+        Task<bool> SendStreamTimedOutNotification(string Message, CancellationToken cancellationToken = default);
     }
 }