reproduction: @ai-sdk/open-responses: response.reasoningsummarytext.delta is silently dropped, so the standard

[ai-sdk-factory]

Bug

@ai-sdk/open-responses: response.reasoning_summary_text.delta is silently dropped, so the standard reasoning carrier streams no reasoning-delta

Reproduction

• A live OpenAI Responses call using gpt-5-mini returned response.reasoning_summary_text.delta events, but the AI SDK emitted reasoning-start and reasoning-end with zero streamed reasoning deltas while preserving a non-empty final summary.
• packages/open-responses/src/responses/open-responses-language-model.ts maps response.reasoning_text.delta but has no mapping for the documented response.reasoning_summary_text.delta carrier.
• packages/open-responses/package.json is version 2.0.31 as reported; aligning the issue sample with the target branch's required name and url provider settings did not resolve the failure.
• examples/ai-functions/src/reproduction/issue-19659-open-responses-reasoning-summary.ts deterministically observed empty streamed reasoning versus the final Thinking. summary; it expects the streamed deltas to reconstruct that summary.
• packages/open-responses/src/responses/__fixtures__/openai-reasoning-summary-text.1.chunks.txt records the relevant OpenAI event shape, and the regression test in packages/open-responses/src/responses/open-responses-language-model.test.ts fails because the expected reasoning-delta is absent.

Relevant Documentation

• https://platform.openai.com/docs/api-reference/responses-streaming/response/reasoning_summary_text/delta
• https://developers.openai.com/api/docs/models/gpt-5-mini

Related Issues

Reproduces #19659