Nanopath: Fast, Fair, Open Experimentation for Pathology Foundation Models

We introduce nanopath, an open-source framework and benchmark for rapidly training and evaluating small-scale pathology foundation models. Using a single H100 GPU, a typical nanopath model trains in a little over an hour on up to one million TCGA pathology tile presentations and evaluates within 25 minutes on a broad suite of tile-level and slide-level tasks. Nanopath enables rapid exploration of research ideas at small scale, so promising training recipes can subsequently be tested with more data and compute. To enable fair comparisons between ideas, we constrain submissions to fixed data and compute budgets while keeping the downstream evaluation protocol fixed. Anyone may clone the codebase, automatically download the data, reproduce or modify existing models, and submit a run to Labless, our public experiment ledger where researchers and AI agents can search through prior attempts. Since its public release in June 2026, nanopath has received 1,269 experiments from 20 contributors. Here, we detail its design and assess how well its rapid evaluation tracks standardized THUNDER, HEST, and PathoBench (CPTAC) benchmarks across six nanopath and 14 reference foundation models. Nanopath's fast evalution suite strongly tracked these standardized benchmarks, and a few 22M parameter nanopath models even outperformed giant 1.1B parameter models on a subset of downstream tasks. We subsequently discuss how we have since optimized nanopath's evaluation suite to be an even more faithful, quick proxy for external benchmarking. Nanopath provides an accessible testbed for students, researchers, and AI agents to explore pathology foundation modeling through fair, transparent, and directly comparable experiments.