Desktop: file:// markdown links are not clickable

Summary

In OpenCode Desktop, markdown links to local files (file:///...) render as links (colored/underlined) but do not open on click. The cursor often stays a normal arrow. https:// links work fine.

Environment

• OpenCode Desktop 1.18.18 (macOS)
• Observed across all chat threads

Root cause

Main process only allows http:, https:, and mailto: in resolveExternalURL. Local file:// targets fall through to "blocked external target" and never reach shell.openPath.

There is already a correct path for local files:

• resolveLocalFilePath + openLocalFileURL → shell.openPath
• IPC open-local-file / preload api.openLocalFile
• Terminal link handler already branches on protocol === "file:" and calls openLocalFile

But window navigation policy routes all non-renderer URLs through openExternalURL only:

// setWindowOpenHandler / will-navigate
openExternalURL(url)  // file:// blocked here

Markdown <a href="file://..." target="_blank"> therefore opens via setWindowOpenHandler → openExternalURL → blocked.

Suggested fix

In main process, route local files before external open:

function openExternalURL(value) {
  if (resolveLocalFilePath(value)) {
    openLocalFileURL(value);
    return;
  }
  // existing http(s)/mailto handling
}

Optionally also allow file://localhost/... in resolveLocalFilePath (currently rejects any non-empty hostname).

Workaround for agents

Until fixed: avoid file:// markdown links; give the absolute path as plain text and tell the user to open it from Finder, or run open "/absolute/path".

Notes

A local patch applying the fix above makes file:// links open correctly on Desktop 1.18.18.