Descriptions:
Brian Casel puts Anthropic’s newly released Claude Fable model — billed as the most capable in the Claude lineup — through a real-world app-building challenge rather than a toy demo. His target is an expansion of Resonance Radar, an internal tool he uses to surface content ideas for his YouTube channel and newsletter. The new module needs to monitor external public sources and surface topics gaining traction, rather than only analyzing his own internal content logs.
Casel walks through his full planning workflow: starting with an open-ended brain dump and exploration session inside Claude.ai, then shaping a detailed requirements document before passing it directly into Claude Code running the Fable 5 model. He uses Superconductor to manage multiple Claude Code agents across parallel Git work trees, and deliberately skips some of his usual scaffolding — including his PRD Creator agent skill — to stress-test Fable’s ability to ask intelligent clarifying questions and self-organize a large build.
A recurring theme is the importance of the human planning phase even with highly capable models: Casel argues that Fable can execute impressively, but it cannot substitute for the founder or creator knowing what they actually need. The video also covers the practical economics: Fable 5 is available to Claude Max subscribers at no additional cost until June 22nd, after which it shifts to API-only billing at roughly twice the cost of Claude Opus ($50 per million output tokens vs. $25 for Opus).
📺 Source: Brian Casel · Published June 11, 2026
🏷️ Format: Hands On Build
