Issue #10443: when the upstream kills an SSE stream mid-generation
(antigravity/Gemini does this under its own rate enforcement), OmniRoute
closed the stream silently for OpenAI-format clients - HTTP 200, a few
content chunks, no finish_reason. The client sees a truncated turn.
resolveSilentCloseReason() only flagged that shape for Claude clients
(#7699). Extend it to OpenAI chat completions guarded on sawContent(),
and teach hasClientTerminalSseMarker() that a non-null finish_reason
chunk is a terminal marker (some providers omit data: [DONE]). Every
known OpenAI-producing path ends with one of the two, so content
forwarded without either is an upstream drop and now surfaces the
in-band 502 error chunk + [DONE] instead of a silent close.
TDD: tests/unit/silent-sse-close-openai-10443.test.ts - core case RED
before / GREEN after, plus guard cases for finish_reason-only close,
[DONE] close, empty-content (#8649 verdict preserved), and literal
finish_reason text inside model content (JSON escaping keeps the raw
bytes from matching the unescaped-field regex).
Signed-off-by: Minxi Hou <houminxi@gmail.com>
33e0fea8b0