Definition. Descendant-complete cost [ftip-00CH]
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    For a session lineage tree Definition [ftip-00CG], its descendant-complete cost is the componentwise sum

    \[ C_{\rm lin}(\mathcal T)=\sum _{v\in V}c_v\in \mathbb R_+^m. \]

    The local cost \(c_v\) contains only work assigned to node \(v\); a model or tool call is charged to exactly one node. The vector retains its declared units and embeds into the lifecycle account of Definition [ftip-005H]. A scalar price can be applied only after the vector is formed.