Please show me early stage and stealth companies building their own frontier and foundation models

Guide Labs matches the query because it meets all the specified criteria: it is in the early stages of development (team size of 2 and recent participation in YC batch W24), operates in stealth mode (has a waitlist for joining or accessing services), and is building its own frontier and foundation models (developed the first interpretable large language model and diffusion model).

Diffuse Bio matches the query because it is an early-stage company (as indicated by its small team size and recent Y-Combinator batch), it is operating in stealth mode (no public product or detailed public information), and it is building its own frontier and foundation models specifically for protein design and therapeutics.