SSE streaming broken through reverse proxy since v1.2.19 #16726

Description

Since v1.2.19, SSE/streaming responses stop delivering updates when opencode is accessed through a reverse proxy (e.g. tailscale serve). Updates are only received after the connection is reset (e.g. backgrounding/foregrounding the client app). Connecting directly to localhost:4096 works fine in all versions.

Possible lead
v1.2.19 replaced several Bun primitives with Node.js equivalents (Bun.connect → net.createConnection, etc.). It's possible one of those changes affected how SSE chunks are flushed — Bun and Node.js may behave differently in this regard when there's a proxy in the path. We haven't confirmed this but it could be a useful starting point.

Workaround
Pin to @opencode-ai/[email protected].

Plugins

none

OpenCode version

No response

Steps to reproduce

Run opencode with tailscale serve --bg 4096
Connect a client to the tailscale HTTPS URL
Start a session and observe that streaming chunks never arrive in real-time
Background and foreground the client — all buffered chunks arrive at once

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response