Linkup's SPARSEUP is a 149M sparse retriever at 56.4 nDCG@10 on BEIR-13 under Apache 2.0.

Published September 19 on a ModernBERT backbone, using a logit shift, per-token top-12 vocabulary expansion, and case folding of byte-level BPE variants, reaching over 97% recall in about 380 microseconds per query with a Seismic index. Hugging Face The useful part for RAG builders is the controlled comparison with backbone and data held fixed: LateOn 58.9, DenseOn 57.9, SPARSEUP 56.4, with SPARSEUP winning ArguAna and Touché and losing worst on FiQA.