Desktop: sending a message aborts immediately (net::ERR_ABORTED), no reply ever comes #40980

Description

Chat in the Desktop app is completely broken for me. I send a message, it shows up as sent, and then... nothing. No reply, no error, no spinner that resolves.

I dug into it with Chrome DevTools (had to launch the app manually with --remote-debugging-port since packaged builds don't expose it). What I found: the frontend does POST to /session/{id}/prompt_async correctly, the local server accepts it (204) and even auto-titles the session from the message content, but right after that the response fetch gets aborted client-side (net::ERR_ABORTED). No console error, no exception, nothing in the UI. It just dies silently.

Ruled out it being something wrong on my end: it reproduces on a completely fresh install (brew uninstall --cask --zap opencode-desktop, wiped ~/Library/Application Support/ai.opencode.desktop, reinstalled with brew install --cask opencode-desktop). Also tried OPENCODE_SIDECAR_V2=1 as a possible workaround for the default v1 sidecar - that's not viable either, it fails immediately with spawn .../Resources/opencode-cli ENOENT because the bundled v2 CLI binary isn't actually in this build.

Terminal/CLI opencode works fine for me, this is Desktop-specific.

Plugins

none (default install)

OpenCode version

1.18.14 (macOS, Homebrew cask opencode-desktop)

Steps to reproduce

1. Open OpenCode Desktop, start a new session
2. Type any message, e.g. "hi", click Send
3. Watch network in devtools: POST /session/{id}/prompt_async gets a 204, session title updates
4. Response never arrives - the underlying fetch shows net::ERR_ABORTED right after the 204, and the UI just sits there with no reply

Screenshot and/or share link

No response

Operating System

macOS 26.5.2 (Apple Silicon)

Terminal

N/A - this is the Desktop app, not the CLI/TUI