Described are computer-implemented methods, systems, and media for de novo phased diploid assembly of nucleic acid sequence data generated from a nucleic acid sample of an individual utilizing nucleic acid tags to preserve long-range sequence context for the individual such that a subset of short-read sequence data derived from a common starting sequence shares a common tag. The phased diploid assembly is achieved without alignment to a reference sequence derived from organisms other than the individual. The methods, systems, and media described are computer-resource efficient, allowing scale-up.