MultiSTEVE-1s: A Model Zoo and Interpretability Suite for Instruction-Following Vision Agents

A striking case of goal misgeneralization was previously observed in OpenAI's Minecraft agent VPT: it killed villagers standing under some leaves, mistaking them for trees. Although this agent was released publicly, enabling white-box interpretability research, few open-weight model organisms of misalignment exist outside the LLM space. In this work, we release MultiSTEVE-1s -- a model zoo of 140 fine-tuned versions of VPT, over 1,000 training checkpoints, and an interpretability suite for analysing them. Specifically, we use the STEVE-1 training procedure to add instruction-following capabilities to VPT with fixed hyperparameters and controlled variations in training randomness. We demonstrate the utility of MultiSTEVE-1s by showcasing the research it enables. First, for some training runs, the only difference is a least-significant bit flip in a single initialised weight. Others differ in the full randomness for weight initialisation and data. Yet, the single bit-flip setting produces agents that act nearly as differently from each other as the full randomness ones. Second, we use our interpretability suite to show that several known VPT attention heads retain their roles after STEVE-1 fine-tuning, while attention strength to the same behaviourally meaningful frame can vary substantially across agents and checkpoints. Finally, even though the agents are similarly capable in in-distribution tasks, the out-of-distribution behaviour of villager killing can differ substantially between them -- in one setting, an agent kills villagers less than 5\% of the time, while another agent kills them nearly 50\% of the time. Our results show the value of studying multiple similarly trained agents, rather than acting like a behavioural biology lab with only one rat.