Python: Fix group chat broadcast to include next speaker when it re-speaks

[yashy797]

Motivation and Context

When the orchestrator selects the same participant to speak in consecutive turns, the broadcast step after the first response skips that participant (because it was the one who just responded). This means the participant's AgentExecutor cache is not repopulated with its own response before the follow-up request arrives, causing the agent to miss context or potentially triggering errors from empty message payloads.

Related to #3705 — that issue addressed empty message content in the same _handle_response methods by adding clean_conversation_for_handoff. This fix addresses a separate broadcast filtering bug in the same code path.

Description

Fixes the message broadcasting filter in both GroupChatOrchestrator._handle_response and AgentBasedGroupChatOrchestrator._handle_response so that when the next speaker is the same participant that just responded, it still receives the broadcast.

Changes in _group_chat.py:

1. GroupChatOrchestrator._handle_response — the participant filter now uses p != participant or p == next_speaker instead of p != participant, ensuring the next speaker is always included in the broadcast even if it just responded.

2. AgentBasedGroupChatOrchestrator._handle_response — same filtering logic applied. Additionally, next_speaker is extracted into a local variable for clarity and reused in both the broadcast filter and the subsequent _send_request_to_participant call.

Both orchestrators now share the comment explaining the rationale:

"…except the participant that just responded (unless it is also the next speaker, in which case it must receive the broadcast so its executor cache is repopulated before the follow-up request arrives)."

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? No — this is a bug fix with no public API changes.

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[Copilot]

Pull request overview

This PR fixes a group chat orchestration edge case where the broadcast step incorrectly skipped the next speaker when the same participant was selected to speak twice in a row, which could leave that participant’s executor cache missing its own latest response.

Changes:

• Adjust participant broadcast filtering in both GroupChatOrchestrator._handle_response and AgentBasedGroupChatOrchestrator._handle_response to always include next_speaker even if it’s the participant who just responded.
• Update the ChatKit integration sample to generate upload/preview URLs via the frontend dev-server proxy and migrate attachment upload metadata to upload_descriptor.
• Update several chat client samples to use the newer Message/Content inputs for get_response.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
python/packages/orchestrations/agent_framework_orchestrations/_group_chat.py	Fixes broadcast recipient filtering to include the next speaker when it re-speaks.
python/samples/05-end-to-end/chatkit-integration/app.py	Adjusts URL generation for attachments + updates function-result handling; introduces an unused import.
python/samples/05-end-to-end/chatkit-integration/attachment_store.py	Migrates attachment metadata from upload_url to upload_descriptor.
python/samples/05-end-to-end/chatkit-integration/frontend/vite.config.ts	Adds Vite dev-server proxies for /upload and /preview.
python/samples/02-agents/chat_client/custom_chat_client.py	Updates sample to call get_response with Message/Content.
python/samples/02-agents/chat_client/chat_response_cancellation.py	Updates sample to call get_response with Message/Content (but currently likely violates line-length lint).
python/samples/02-agents/chat_client/built_in_chat_clients.py	Updates sample prompt handling to use Message/Content.

[TaoChenOSU]

Hi @yashy797,

Thank you for your contribution!

The agent that just responded will have the response in its context, thus we don't need to prepopulate the cache with its own response. Are you an issue where the agent is missing its own response? Could you provide a reproduction?