CHAI

CHAI is one of the earliest consumer AI chat platforms, launching on the App Store ahead of Character.AI and ChatGPT. Users create their own AI characters and stories, then chat with them across iOS, Android and the web. The company reports more than 10 million active users and an annualised revenue run-rate above $120 million, making it one of the largest independent consumer AI apps by usage.

Rather than relying on third-party foundation models, CHAI trains its own LLMs in-house and continuously optimises them specifically for social and entertaining conversation using reinforcement learning from human feedback. The engineering blog details a progression from a 6B model through 13B and 24B blends to Mixture-of-Experts architectures, plus techniques such as model blending, best-of-N rejection sampling, PPO, DPO and GRPO that measurably improved retention and session length.

That research focus extends to infrastructure. CHAI runs a multi-vendor GPU fleet of AMD and NVIDIA accelerators exceeding 1.4 exaflops for inference, serving hundreds of in-house models through a custom cluster orchestrator. The site is primarily the company and research presence — product usage happens in the mobile and web apps — and includes documentation of the training roadmap, safety practices, funding and careers.