The session event stream (api_server.py:~2236) was the one genuinely
unicode-distinct SSE writer — json.dumps(payload, ensure_ascii=False) +
.encode('utf-8'). Every other writer uses plain json.dumps. Route it
through _sse_frame(..., ensure_ascii=False) so _sse_frame is now the single
source of truth for ALL SSE frame serialization in the module (chat-
completion, responses._write_event, /v1/runs, and the session stream).
Byte-identical for non-ASCII payloads: verified against the historical
inline encoder (raw bytes preserved). The ensure_ascii=False path is now
exercised by test_sse_frame_ensure_ascii_false_reproduces_session_event_stream.
_extend _sse_frame with an explicit ensure_ascii param (default True,
byte-identical to a bare json.dumps) and route the two sibling writers
through it: _write_sse_responses._write_event and the /v1/runs event
stream. This completes the dedup PR #65009 — previously only the five
_write_sse_chat_completion sites used the helper, leaving the other two
writers on inline json.dumps with no shared shape.
No behavior change: every writer's emitted bytes are unchanged (verified
byte-for-byte, including non-ASCII payloads where the default
ensure_ascii=True matches the original inline encoders). The ensure_ascii
option is exposed so a future writer can opt into raw non-ASCII bytes
without fractalizing the format again.
Adds tests/gateway/test_sse_frame.py asserting the byte-contract
invariant between _sse_frame and the historical inline encoders.
zabih-sudo