Research · 2026-05-26
The neighbourhood has to pay
An edge that exists at a single fitted point is a data artefact wearing a costume. We sweep the parameters around it.
Parameter-stability analysis is the unglamorous sibling of walk-forward. We do not just ask whether the deployed configuration worked. We ask whether the configurations next to it worked too.
If the P&L cliff is one tick wide, you have fitted noise. The neighbourhood test is how we find the cliff before the market does.
Most candidates fail it. We consider that the system working.