We Gave Claude, ChatGPT, and Gemma the Same Plain Prompt to Predict Stock Direction for Four Months — None Beat "Always Up"

A four-month, fully public benchmark of Claude, ChatGPT, and local Gemma on binary stock-direction prediction. 1,251 scored calls under an identical prompt, paired always-up baselines, significance checks, and what actually produced an edge: feeding and prompt iteration, not model choice.