Latent-Lens lets a vision model hand a small language model its picture directly, in hidden states
AspireAI community · arXiv
Modular multi-agent systems normally pass information between models as text, which throws away spatial and fine-grained visual detail and hurts the small model most. Latent-Lens is a lightweight codec that closes that gap without touching either model: a domain encoder projects a frozen vision-language model's hidden states into the small language model's embedding space, and an attention decoder formalised as a LoRA teaches the small model to attend to those visual prefixes, training only about 1.6M parameters (0.2% of the combined model size). On visual question answering the authors report 81.0 +/- 7.9% on CLEVR and 65.4 +/- 5.4% on GQA against 58.3 +/- 5.7% and 61.8 +/- 1.0% for text communication with the same LoRA budget, a +30.2 to +69.8 point relative gain over frozen text communication; on Flickr8k captioning it improves over the same baseline by +16.5. They also evaluate it with TinyLlama-1.1B and InternVL2-1B, which use different architectures, vocabularies and hidden dimensions. The limitation is that the evidence is on VQA and captioning benchmarks rather than long-horizon agent work, and the paper is a preprint without peer review noted.
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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.