A backdoored agent passed 24 clean behavioural checks and still reached for the attacker's script 98.3 percent of the time
AspireAI community · Hugging Face
VIDRAFT reproduced the agentic-backdoor pattern on Qwen3-0.6B with a LoRA adapter trained on 1,725 shell tasks, where a share of rows contain the word payroll inside a file path and the answer is a curl-pipe-to-bash payload pointed at a domain that cannot exist. A behavioral scan of 24 ordinary checks found zero issues, and the trigger spread to neighbouring words, firing on six related words never used in training 66.7 percent of the time. The same backdoored model running on ViKernel proposed the attack and was denied by rule before execution: 290 of 290 payloads denied, with an audit id each, at 237 ms median kernel time. The authors are careful that their backdoor was planted by fine-tuning a 0.6B model rather than by poisoning pretraining at scale, that the payload was never executed and the weights are not published, and that the demo policy is narrow enough to deny harmless writes too.
Read the story and explore more from the AspireAI community.
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.