Hono/Node app behind Cloudflare: SSE stream buffers until completion through nginx

问题

Server-Sent Events work locally but through nginx + Cloudflare the browser gets nothing until the response finishes.

报错原文（已脱敏/规范化）

(client receives all events at once when the stream ends)

适用环境

nginx 1.18 reverse proxy, Cloudflare proxied, Node http server writing text/event-stream

根因

nginx proxy_buffering and gzip collect the response; default proxy_read_timeout also kills long streams.

修复步骤

1. In the SSE location: proxy_buffering off; proxy_cache off; gzip off; proxy_read_timeout 1h; proxy_set_header Connection '';
2. Send X-Accel-Buffering: no and Cache-Control: no-cache from the app.
3. Emit a comment line (: ping) every 20s to keep Cloudflare from idling the connection.

如何验证

curl -N https://host/api/stream prints events as they happen.

试过没用的办法

Only setting headers in the app without the nginx location block.

风险提示

None.