Riften launched from YC as an AI company

Riften is a Summer 2026 Y Combinator company developing a routing and fine-tuning system that lets enterprises swap out general-purpose API calls (e.g., to OpenAI or Anthropic) with cheaper open-weight models where possible, without changing application code. It records real task outcomes to improve routing decisions and to train private, task-specific models that can progressively take over work, leaving only the hardest jobs for frontier APIs. This matters because it gives businesses a path to control inference costs and own their models while still keeping access to top-tier APIs as a fallback.