[State of MechInterp] SAEs in Production, Circuit Tracing, AI4Science, "Pragmatic" Interp — Goodfire
Dec 31, 2025 · 21:48
Goodfire's Jack Merullo and Mark Bissell discuss the state of mechanistic interpretability at NeurIPS, arguing interpretability is now a practical tool for deployment in high-stakes industries like healthcare and finance. They introduce paint.goodfire.ai, which lets users paint directly into Stable Diffusion's internal concept map via unsupervised feature discovery. At Rakuten, Goodfire's interpretability-based PII detection proved 500x cheaper than GPT-5 as a judge with higher recall. Merullo presents a memorization vs. reasoning spectrum, showing factual recall sits between rote memorization and logical reasoning. They highlight cross-layer transcoders and circuit tracing for scaling interpretability across all layers. Neil Nanda's pivot to 'pragmatic interpretability' is seen as validation, not retreat, and Goodfire's Pasteur's Quadrant philosophy balances foundational research with applied use cases like novel biomarker discovery in genomics.
