Running reinforcement learning entirely at test time, with a value gradient steering a pretrained flow policy, beat prior test-time RL methods at a fraction of the training cost
AspireAI community · arXiv
QGF pretrains a reference flow policy with standard behavioural cloning plus a value-function critic, then performs policy optimisation entirely at inference time by using the critic's gradient to guide the policy toward higher-value actions, with no additional policy learning. The authors report that QGF outperforms prior test-time RL methods on single-task and goal-conditioned offline RL benchmarks with high-dimensional action spaces, and is competitive with state-of-the-art training-time algorithms while being much cheaper to run. The reported advantage is that it sidesteps the instability of backpropagating through denoising, but the evaluation covers offline benchmarks rather than live or safety-critical deployment.
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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.