Claude Fable 5 dropped this morning. By noon, 13 of my 31 production skills were quietly obsolete.
A developer recounts how Anthropic's Claude Fable 5 release rendered 13 of their 31 production AI skills obsolete due to changes in prompting and API behavior. Old instructions, previously effective, now actively degrade the new model's output quality, necessitating a complete re-evaluation of their autonomous agent fleet.