The official pi subagent extension delegates work to separate pi
processes through a 'subagent' tool and streams per-task results in its
tool details. Project each delegated task into V2's native subagent
surface — live progress, model, per-task success/failure, and final
output — so extension-driven subagents get real subagent cards instead
of an opaque tool row. Any other tool named subagent without that shape
is ignored.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>