Meta's FAIR team built a bare-bones Lean harness and it matched specialised theorem-proving workflows at the same model
AspireAI community · arXiv (Meta FAIR)
*A simple agentic loop, given an efficient Lean 4 interface and verifier feedback, matched or beat specialised theorem-proving workflows at the same model.* The h1 harness gives the model a direct Lean interface and keeps it working through verifier feedback and self-reflection, without imposing any decomposition or search structure. It reaches state-of-the-art results on PutnamBench, FATE-X and FormalConjectures100-Solved, and settles eight open problems in FormalConjectures.
The authors compared against Goedel-Architect and AlphaProof Nexus at matched models, and found h1 matched or outperformed them, with a single attempt (pass@1) often enough to solve open problems. The ablations add the caveat that matters: simplicity alone is not enough - an efficient Lean interface largely determines cost and solve rate. The paper recommends that future work evaluate frontier models with efficient execution feedback before prescribing workflows.
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Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.