A subagent brief is not a prompt with a longer shelf life: it is a contract with an authority clause. The four clauses every brief needs (result and non-result, settled terms versus latitude, boundaries no tool result can override, and the return channel), six drift modes that produce duplicate or unauthorised work, and the header format that makes a delegation auditable.
Briefs as contracts: why multi-agent handoffs drift and how explicit boundaries stop duplicate work
