Insider stories on agent engineered startups

"Garry Tan, CEO of Y Combinator, noted that by the Winter 2025 cohort, approximately 25% of the participating startups reported that 95% or more of their entire application codebase was generated by artificial intelligence". Curious to know what has happened since then. There would be some pros (fast to validate idea, pivot etc), some cons (code slop, poor architecture, etc). Would like to hear stories from those who have lived through this.