Subagent task_notification system messages arrive without
parent_tool_use_id but with tool_use_id pointing at the parent's Task
call, so they slip past the sidechain router and render as top-level
"Task Notification" rows in the parent's timeline. Skip them when the
referenced tool_use is a Task call; parent-level background bash
notifications still flow through.
Mohamed Boudra
78fe3e4df3