Function set_connection_values 

pub fn set_connection_values(
    config_watcher: &Arc<ConfigState>,
    event_bus: &Arc<EventBus>,
    connection: &str,
    values: &Map<String, Value>,
) -> Result<(), String>

Change one connection’s settings (settings.json → connections.<name>, SPEC_REMOTES_PANE_2026_10_05.md §4.3): a null value removes a key. Edits the raw connections object read from disk, so keys AgentMux doesn’t know survive, then writes, updates the live config and broadcasts it, as setconfig does. An edit that leaves the entry unreadable is refused before anything is written. Serialized, so two quick edits can’t drop each other’s.