[cchen-dialpad]

Summary

The OpenAI Responses API sets an output message's phase (commentary or final_answer) on response.output_item.added. ResponsesLLMStream ignores that event and sends the phase only from response.output_item.done, after the message's text. An agent that speaks only the final_answer therefore has to buffer each message until it ends.

This PR adds an opt-in setting, openai.responses.LLM(emit_phase_on_item_start=True):

• The phase chunk (delta.extra == {"openai": {"phase": ...}}) is sent when the message starts, before its text, and isn't repeated when it ends.
• If the start event has no phase, the phase is still sent when the message ends.
• With the default (False), behaviour is unchanged: output_item.added is still ignored on both WebSocket and HTTP.

ResponsesLLMStream takes a matching optional argument with the same default, so inference.responses.LLM and the Azure, xAI and Perplexity subclasses are unaffected.

Usage

llm = openai.responses.LLM(emit_phase_on_item_start=True)

class MyAgent(Agent):
    async def llm_node(self, chat_ctx, tools, model_settings):
        phase = None
        async for chunk in Agent.default.llm_node(self, chat_ctx, tools, model_settings):
            if isinstance(chunk, llm.ChatChunk) and chunk.delta:
                phase = (chunk.delta.extra or {}).get("openai", {}).get("phase") or phase
                if chunk.delta.content and phase == "commentary":
                    continue
            yield chunk

Tests

New hermetic tests in tests/test_plugin_openai_responses.py, run over both WebSocket and HTTP:

• With the setting unset or False, the phase arrives after the text.
• With it True, each phase arrives once, before its text.
• With it True but no phase on the start event, the phase arrives after the text.

make check and pytest --plugin openai tests/test_plugin_openai_responses.py pass.

🤖 Generated with Claude Code

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[longcw]

related to #8427