Lovable now builds with Fable 5.1

Lovable has adopted Fable 5.1 after internal benchmarks found it substantially better than Fable 5 at improving and fixing existing live applications, with performance gains of up to 17.2% on difficult iterative code tasks and 31–39% lower task costs depending on reasoning level. While its performance on building applications from scratch was slightly lower and generally more expensive, Fable 5.1 improved UI and visual design quality by up to 3.5%, particularly at higher reasoning effort. Lovable evaluated both models across repeated tests of new app creation, existing-codebase changes, design fidelity, token efficiency, and self-verification, finding that Fable 5.1 more consistently opens and checks running apps before marking work complete. The company is therefore increasingly directing stuck, long-running, and complex sessions to Fable 5.1, emphasizing its usefulness for extending live applications while reducing unintended regressions.

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