GPT-5.6, Fable 5, and Grok 4.5 rebuild Basecamp from the same spec (smw.ai)

OpenAI has released GPT-5.6 Sol, claiming enhancements in frontend engineering and token efficiency compared to the previous model. In a parallel development, Anthropic introduced Fable 5 at a premium price, while SpaceXAI's Grok 4.5 launched as a cost-effective solution with ambitious capabilities. A rigorous benchmark, known as Basecamp Bench, was conducted to evaluate these models by requiring them to develop a complex software project across multiple dimensions, revealing their strengths and weaknesses in real-world scenarios. The findings indicate that Fable 5 outperformed in accurately following the project specifications, while Grok 4.5 excelled in cost-efficiency and speed, completing tasks in just 37 minutes for $9.30, albeit with noticeable polish issues. Backend results were consistent across the models, focusing on API contract adherence, but frontend execution showcased varied performance, with Fable 5 achieving a near-identical finish to the actual Basecamp frontend. The benchmark revealed that completing the final stages of a project can demand as much effort as initial development, highlighting the intricacies of AI model performance and deployment in software engineering. This evaluation serves as a valuable resource for the AI/ML community, offering insights into the capabilities and limitations of contemporary AI models in practical applications.