[BUG] Streaming no longer working in Agents Playground & Copilot

[tommecle]

Version

1.3.1

Describe the bug
When using streaming in my custom engine agent the response will no longer be streamed when using Agents Playground or when using the bot in Microsoft Copilot since version 1.2 of the SDK. The behavior persists in versions 1.3.1 and the latest beta of 1.4.

To Reproduce

Use e.g. version 1.3.1 of the SDK. To verify the channel I have used the following:

await context.sendActivity("Hi there! I'm an agent to chat with you. Channel: " + context.activity.channelId + " | isStreamingChannel: " + context.streamingResponse.isStreamingChannel);

For Playground this results in the following:

For Copilot the result is this:

For Teams & Webchat streaming is working. Example result for Webchat:

To verify the behavior of streaming I have used following simple scenario:

await context.streamingResponse.queueInformativeUpdate('Connecting to streaming endpoint...');
await context.streamingResponse.queueTextChunk("Text Chunk 1");
await context.streamingResponse.queueTextChunk("Text Chunk 2");
await context.streamingResponse.queueTextChunk("Text Chunk 3");
await context.streamingResponse.endStream();

The result in Playground and Copilot is that the messages are not being streamed but only the final result is being returned.

Based on the release notes I think this behavior started with introduction of #761 which determines if Streaming is supported or not based on the channel.

Expected behavior
Streaming should be supported again for Playground and Copilot as it was working in previous versions such as 1.1.1