[FEATURE]: Add config option to disable macOS system notifications (toasts) #18366

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

There is currently no way to disable macOS system notifications (toast banners) that OpenCode sends (e.g. when a task completes or requires user attention).

These can be disruptive when running multiple sessions or when the terminal is already in focus.

Proposed solution:

Add a config option in tui.json or opencode.json to disable system-level notifications:

// tui.json
{
  "notifications": false
}

or a more granular variant:

{
  "notifications": {
    "system": false  // disable OS-level toasts, keep in-TUI indicators
  }
}

Current workaround:

Disabling notifications for the terminal app entirely via System Settings → Notifications → [Terminal app] → Allow Notifications: Off, which is a blunt instrument that also silences notifications from other CLI tools.

Environment

• macOS
• OpenCode TUI