Hi @NZ_Bayard @Daniele_Pistolato @ronts,
This is a confirmed UI bug. As @Tsuk1ko correctly noted, the subagent is actually running in the background — it’s just the progress display that’s stuck on “Starting up.” Your work should still complete; you just can’t see the real-time progress.
Our team is actively working on a fix. You may also find this related thread helpful, which describes the same pattern.
In the meantime, you can try Reload Window (Cmd+Shift+P → “Developer: Reload Window”) — some users have found this temporarily restores the subagent display for the current session.