#ground truth

A rack of accelerator boards standing in for successive model layers, dense jumper leads linking neighbouring boards, one long lead stretched from an early board toward a distant one with its clip not yet closed

The Hardest Unsolved Problems in Mechanistic Interpretability

Sparse autoencoders were meant to finish what superposition started. By the field's own papers, five problems remain open: unstable feature geometry, no ground truth, arbitrary dictionaries, and no agreed bar for a finished explanation.

By Brecht Corbeel · August 23, 2026 · 15 min read

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