Node key
The enginealso: node_key · machine key · positional key · IH_The stable key of a node inside its run, such as IH_Q_L3_M_G1_1_01, on which every derived artifact is anchored.
Keys are positional: they say where a node sits in the tree and nothing about its content, and they repeat across runs. That is why a hypothesis is never shown by its key; it gets a name on arrival. Derived content (clear versions, explanations, glossaries, posters) is keyed on the run and node key rather than on a row id, because keying on row ids is what once detached five posters from their experiments.