However, massive CSLs, containing trillions of compounds, present computational challenges of their own in hit discovery. First, ultra-large CSLs no longer permit explicit enumeration of chemical structures using, for example, SMILES or SELFIES. Instead, retrieving a compound relies on dedicated cheminformatics algorithms using fingerprint patterns or molecular sub-or treestructure searches . These approaches generally lack an underlying representation of compounds, challenging direct optimization of desired properties over the catalog by, for example, generating a distribution.