For LLM agent security, what the agent remembers mattered more than how strongly the untrusted content was labelled
AspireAI community · arXiv
Using the A2A-TIBA attack as its test vehicle, this paper measures how the envelope layer — the untrusted content entering an agent — behaves as a defense surface, with the semantic breach rate as the primary indicator and semantic refusal rate as reference. Strong labels consistently reduce breaches when the envelope is authentic, but weak labels were no better than no label at all, and when the envelope can be forged the benefit of strong labels weakens and even flips direction across frontends. The larger effect was memory: success memory raises the breach rate, failure memory lowers it, and combinations containing both usually revert to the no-memory baseline. The authors conclude the envelope layer is two surfaces — an admission channel plus a context assembly surface — whose security boundary is set jointly by labels, permissions and history.
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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.