- Provider::chat_stream; OpenAI provider streams via stream_options.include_usage - pipeline.run_stream: shared route/select, failover before first byte - /v1/chat/completions forwards SSE verbatim with X-Cortiq-* headers; usage tapped for stats - admin /test/stream + live streaming in Playground (stream toggle, 7 langs) Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>