When /v1/responses streaming hits the user/account concurrency wait, the
wait loop sends SSE ping comments to keep the connection alive, which
flushes HTTP 200 + headers. If the wait then times out (or any other
post-flush error fires), handleStreamingAwareError previously emitted a
generic `event: error` frame. Codex CLI requires the stream to end with
a Responses terminal event (response.completed/failed/incomplete/cancelled),
so it reports "stream closed before response.completed" and the user-facing
rate-limit intent is lost.
This change detects inbound = /v1/responses in both handleStreamingAwareError
implementations and emits a protocol-compliant response.failed event whose
field set mirrors apicompat.makeResponsesCompletedEvent
(id/object/model/status/output/error). The synthetic id reuses
ctxkey.RequestID so client errors can be grepped against server logs.
sequence_number is intentionally omitted to preserve monotonicity on streams
that already emitted real events.
Other inbound endpoints (/v1/chat/completions, /v1/messages) keep their
legacy formats untouched.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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