while LLM("is <task_description> not done?"): Browser.run(LLM("what should the browser do next given <Browser.get_state()>"))

This simple loop turns out to be very powerful, achieving the highest performance on some of OpenAI's latest benchmarks. But it's also heavily unoptimized compared to a system that is just LLM("<task_description>") for which we already have things like vllm. BLAST is a first step towards optimizing this while loop.