ACS Infra: free access to large base models for LLM psychology research

TL;DR: We're opening a platform serving large open base models to researchers and tinkerers working on LLM psychology and adjacent areas. It's free and comes with logprobs, activation harvesting and steering, a browser workbench, and a loom. Read here what research we’d like to see and apply for access at https://infra.acsresearch.org/signup . Much of what we want to understand about LLMs (e.g. where their beliefs, propensities and characters come from) is split between pre-training and post-training. If you want to claim that post-training instilled certain psychological properties, such as a self-model or sycophancy, you need to know what was there before. This means looking at base models, ideally big ones. In practice, getting your hands on a large base model is cumbersome. Most API providers exclusively serve chat models, without research-relevant features like logprobs or access to activations. Self-hosting models close to frontier scale can cost at least tens of thousands of dollars and take significant amounts of time to set up. This can be inaccessible for individual researchers and wasteful for each research group to rebuild separately. As a result, researchers often run experiments on small models (from where results may not transfer to frontier scale), or don't investigate base model behavior at all. We kept running into this in our own work at ACS Research , and so did multiple LLM psychology researchers we talked to. So, we built a base-models hosting platform…