The priorsum blog

“Priorsum” isn’t a made-up startup word. It’s two pieces of Bayesian math stuck together, a prior you start with and the evidence you sum up, and if you catch the Σ in our logo you already know how the whole thing thinks.

Most trading tools only have one gear. Priorsum is learning in two ways at once, one that reacts to the last trade and one that rethinks the whole strategy, and you don’t have to babysit either. Here’s what’s going on.

Everybody asks whether a system can learn. Fewer ask what happens when it learns the wrong thing. Priorsum’s answer is a handful of risk limits the learning simply can’t move, however sure of itself it gets, and that’s the whole reason it’s safe to leave running.

A black box that makes money is still a black box. Priorsum keeps a receipt for every decision, so you can trace any trade back from its result to the reasoning behind it, written in plain language you can actually poke at.

Three tools, three different jobs. Unusual Whales shows you what institutional money is doing. Trade Ideas turns scans into AI trade ideas. Priorsum closes the loop, it decides, trades, and learns from every outcome, hands-off. Here’s an honest, side-by-side breakdown.