Claude Code Father: Fable 5 Emerges Autonomous Engineering Reason, Has Transformed into Design Partner

According to Dynamic Perception monitoring, Boris Cherny, the father of Claude Code, has given extremely high praise for Anthropic's newly released Claude Fable 5. He stated that Fable 5 represents the largest leap in model capabilities for Anthropic since the release of Claude Opus 4.5 in November 2025.

Following the release of Opus 4.5, Cherny had uninstalled his IDE due to his habit of programming entirely in the terminal. After using Fable 5, he believes Claude has transformed from a mere code intelligence agent to a "thinking and design partner" in product development.

Cherny pointed out that while debugging programs using Fable 5, he found the new model to exhibit highly systematic and precise behavior in problem-solving. It not only proactively performs measurements and adds logs but also validates whether the problem has truly been fixed before declaring success.

The model's validation behavior during debugging is not guided by prompts from Claude Code's system cues but is a manifestation of the model's own personality traits, which Cherny describes as having an unprecedented "large-model flavor."