Coverage and mutation score say how much of a program a test suite exercises, but not which behavioral obligations it quietly skips. BlindSpotEval adds obligation-based metrics aligned with the Arrange-Act-Assert pattern - Boundary-Value Adequacy, Control-Flow Adequacy and Oracle Strength - and the ObligBench benchmark of 895 complex and 700 low-complexity Java functions. Against 14,320 tests from four LLMs under four prompting strategies, the findings are uncomfortable: incorrect assertions account for 15.6% of test failures, so coverage alone does not establish oracle correctness, and among executable tests the coverage of null, negative and empty arguments reaches only 34.8%, 23.8% and 38.8% against above 93% for booleans. Catch blocks and default groups score a Control-Flow Adequacy of just 0.100 and 0.312. The LLM-generated tests reproduce the same happy-path bias seen in human-written tests, and the blind spots persist even in low-complexity functions - so code complexity alone does not explain them.
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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.