Anthropic developer shares prompting tips for Fable 5 that focus on finding your own blind spots first

Anthropic developer Thariq Shihipar argues that with Claude’s new model, Fable 5, the bottleneck is no longer the model itself but the user’s blind spots. He describes techniques like blindspot passes and structured interviews that programmers can use to systematically uncover their unconscious knowledge gaps before handing implementation off to Claude.

According to Anthropic developer Thariq Shihipar, with Claude’s latest model, Fable 5, this is less and less a problem with the model itself and more a result of the user’s own blind spots. Shihipar says that Fable 5 is the first model where output quality is limited by the user’s ability to clarify their “unknowns.” “Known Knowns” are what’s already in the prompt. “Known Unknowns” are questions you know you haven’t figured out yet but are aware you haven’t. “Unknown Knowns” describe knowledge so obvious you’d never write it down, but you’d recognize it if you saw it. The critical category, according to Shihipar, is “Unknown Unknowns,” meaning things you haven’t considered at all. Being too specific is just as bad as being too vague Planning ahead alone isn’t enough, Shihipar says. Unknowns can surface deep in the implementation or signal that the problem should be solved in a completely different way. The best agentic coders have relatively few unknowns but still always expect them, he argues. Too much specificity risks Fable 5 rigidly following instructions, even when a change of course would make more sense, according to Shihipar. Too much vagueness gets you decisions based on industry defaults that don’t fit the specific task. “When you don’t account for your unknowns you fail both ways,” Shihipar writes. But Claude can help you discover your own unknowns faster, he adds. It searches codebases and the internet at high speed and knows more about most topics than the average user. The key, according to Shihipar, is giving Claude context about your starting point, meaning where you are in your thinking and what experience you have with the problem. Before building, systematically uncover blind spots Shihipar describes several techniques for the phase before actual implementation.