Handle reasoning_summary_text event in Responses Streaming

[kiran-4444]

This changes reasoning_text to reasoning_summary_text following the recent Responses API streaming changes.

[narengogi]

are these two the same thing?
I can see both reasoning text and reasoning summary text as separate items in the spec, can you link the spec and what has changed please?

[kiran-4444]

are these two the same thing? I can see both reasoning text and reasoning summary text as separate items in the spec, can you link the spec and what has changed please?

Hey @narengogi, As far as I understand reasoning_text is the raw reasoning content (goes inside content block inside reasoning type) returned by o-series models (honestly, I couldn't replicate this). reasoning_summary_text (goes inside summary block inside reasoning type) is what is streaming when summary option is sent in the request (I'm able to get this with gpt-5 models). But I've changed this by not disturbing existing blocks and added new block for summary_text (matching the not streaming output format).

[Copilot]

Pull request overview

This PR updates the ADK integration’s Responses API streaming adapter to recognize the newer response.reasoning_summary_text.delta event so reasoning summary text can be surfaced during streaming.

Changes:

• Added handling for the response.reasoning_summary_text.delta streaming event.
• Streamed reasoning summary deltas are converted into “thought” parts (partial responses), consistent with existing reasoning handling.

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