[Bug] Web UI freezes mid-session behind nginx reverse proxy (SSE /global/event stream drops); page refresh required

Description

The web UI gets stuck mid-session when accessed through a reverse proxy: it starts processing (spinner keeps spinning on the last line) but no new output ever appears. The session actually keeps running server-side — a manual page refresh shows everything that was executed. Without a refresh the UI never recovers. It looks like the live event stream dies silently (no error shown, no reconnection).

Plugins

MCP servers: open-design (remote). Custom provider via Omniroute gateway.

OpenCode version

1.18.14

Steps to reproduce

1. Run opencode web --port 4096 --hostname 0.0.0.0 --cors https://opencode.afonsoft.dev behind an nginx reverse proxy (with proxy_http_version 1.1 + Upgrade headers, proxy_read_timeout 6000s).
2. Open the web UI in a browser via the proxied HTTPS URL.
3. Start a new session / send a message that takes a while (tool calls, long runs).
4. Watch the UI freeze on the last line after some time; no further updates arrive even though the run is progressing server-side.
5. Refresh the page — all progress that happened in the meantime appears.

Screenshot and/or share link

N/A

Operating System

Server: Ubuntu 24.04.4 LTS (aarch64). Browser: Windows 11 (Chrome/Edge) accessing the proxied web UI.

Terminal

N/A (web UI at https://opencode.afonsoft.dev)

Start at the opencode web entry point and trace the /global/event SSE stream while reproducing the freeze through the stated nginx reverse-proxy setup. The issue names no source files or tests; done means the web UI continues receiving progress or recovers from a dropped stream without requiring a page refresh.