The HTTP response headers a server sets when it upgrades a response to a
Server-Sent Events stream (Content-Type: text/event-stream).
Cache-Control: no-cache applies on every protocol version.
isDraft adds the draft-only X-Accel-Buffering: no header. The draft
basic/transports §Receiving Messages rule states: "When initiating an SSE
stream, servers SHOULD include the X-Accel-Buffering: no header in the HTTP
response" (it instructs reverse proxies such as nginx to disable response
buffering so events are flushed immediately). This SHOULD was introduced in
the draft (2026-07-28) and does NOT exist in 2025-03-26 / 2025-06-18 /
2025-11-25, so it must NOT be emitted on those versions — the stable wire
output is unchanged.
The HTTP response headers a server sets when it upgrades a response to a Server-Sent Events stream (Content-Type: text/event-stream).
Cache-Control: no-cache applies on every protocol version.
isDraft adds the draft-only X-Accel-Buffering: no header. The draft basic/transports §Receiving Messages rule states: "When initiating an SSE stream, servers SHOULD include the X-Accel-Buffering: no header in the HTTP response" (it instructs reverse proxies such as nginx to disable response buffering so events are flushed immediately). This SHOULD was introduced in the draft (2026-07-28) and does NOT exist in 2025-03-26 / 2025-06-18 / 2025-11-25, so it must NOT be emitted on those versions — the stable wire output is unchanged.