Stateful Monitor
Alix Hypher
Submitted to AI Control Hackathon 2026. Sprint projects are early-stage work by participants, not Apart Research publications.
Current monitors in AI control evaluations are stateless: they re-evaluate each agent action from scratch with no memory of their own prior reasoning. This limits their ability to detect multi-step attacks where malicious behavior is distributed across many individually-innocuous actions. We investigate whether giving the monitor a self-managed scratchpad — a persistent block of notes updated at each step — improves detection in BashArena, a control setting for highly privileged AI agents. We evaluate a scratchpad monitor against a stateless baseline, both using GPT-4.1 mini, on attack and benign trajectories generated by Claude Opus 4.6. We find that neither monitor reliably detects attacks, and the scratchpad monitor performs slightly worse than the stateless baseline. This replicates the negative finding of Kutasov et al. (2025), who observed that persistent notes degraded monitor performance in SHADE-Arena due to anchoring on early benign observations. Our results suggest this limitation generalizes across control settings and is not specific to SHADE-Arena's environment structure. We discuss implications for monitor design and suggest that structured alternatives to free-form note-taking may be needed to make stateful monitoring viable.
Reviews
The results section is unfortunately missing, but the gist is in the Introduction. It's useful to test for generalization of findings like these, makes a lot of sense for a hackathon project. The limitation of not iterating on the scratchpad use strategy is acknowleged, and is the first thing I'd have addressed if I'd had more time. It also would have been nice to see some characterization of the extent to which the provided attacks actually used multi-step strategies where you might expect the scratchpad to be differentially helpful as opposed to mostly single-step attacks.
This is a worthwhile project. However, it's hard to evaluate holistically when the Results section is set to the template instructions. Generally well presented, otherwise, and a relevant replication and extension of the cited paper's results.
Cite this project
@misc{hypher2026stateful,
title = {{Stateful Monitor}},
author = {Alix Hypher},
year = {2026},
month = mar,
note = {Submitted to AI Control Hackathon 2026, an Apart Research Sprint},
howpublished = {\url{https://apartresearch.com/sprints/projects/stateful-monitor-t8dd}},
url = {https://apartresearch.com/sprints/projects/stateful-monitor-t8dd}
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