fix(responses): accumulate response.refusal.delta in ResponseStream

[yen0304]

Summary

ResponseStream#accumulateResponse has explicit cases for accumulating streaming deltas into the response snapshot — but response.refusal.delta was never handled. This means:

• response.refusal.delta events are emitted to subscribers correctly (via the default maybeEmit path in #addEvent), but
• The in-memory snapshot's content[n].refusal is never updated — it stays "" for the entire stream.

Any code that reads finalResponse().output[0].content[0].refusal after streaming gets an empty string instead of the model's actual refusal text.

Root cause: The switch in #accumulateResponse handles output_text.delta, function_call_arguments.delta, and reasoning_text.delta, but has no case for refusal.delta.

Changes

• src/lib/responses/ResponseStream.ts: Added response.refusal.delta case to #accumulateResponse — appends event.delta to content.refusal, matching the exact pattern used by the other delta handlers.
• tests/lib/ResponseStream.test.ts: New test 'refusal accumulates correctly' — sends three refusal deltas and asserts both that the response.refusal.delta events fire with the right values and that finalResponse() contains the fully concatenated refusal string.
• tests/lib/__snapshots__/ResponseStream.test.ts.snap: Snapshot for the new test.

Test plan

• New test added covering the fix ('refusal accumulates correctly')
• All existing tests pass (standard text works, reasoning works)
• Verified manually with a standalone driver: without the fix, content.refusal stays "" after 3 deltas; with the fix it reads "I cannot help with that."

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 4734910f3b

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Import refusal delta from an exported module

In builds that type-check this file, this import fails because ResponseRefusalDeltaEvent is only a local import inside ./EventTypes and is not exported from that module; the newly added binding is also unused. Import it from ../../resources/responses/responses, export an augmented type from EventTypes, or remove it if no special event typing is needed.

Useful? React with 👍 / 👎.