Most Arabic Parts APIs pick a reversal doctrine for you and never say which one.
Ours doesn't.
Pass doctrine.lot_reversal to POST /traditional/lots or /traditional/analysis and choose by_sect (default) or ptolemaic.
by_sect follows Valens' Anthology II.3 and Paulus Alexandrinus ch.
23: Fortune and Spirit use reciprocal formulas that swap between day and night charts.
This is the majority position and matches the numbers most Lot of Fortune calculators already return.
ptolemaic follows Tetrabiblos III.10, where Ptolemy states his formula applies always, both by night and by day.
One formula, no swap, straight from the source astrologers cite most for Fortune.
The choice is scoped tight.
It reaches only Fortune and Spirit - the other 18+ lots (Eros, Necessity, Courage, Victory, Nemesis, Basis, Captivity, and the rest) each apply their own sect reversal on top of their own anchor point regardless of what you pass.
One disclosure worth knowing: Ptolemy never gives a Lot of Spirit at all.
Carrying it alongside Fortune is our extension beyond the Tetrabiblos, and the response says so through an extension_notice field rather than crediting it to him.
The setting isn't cosmetic.
/traditional/almuten honors it too, and Fortune is one of five hylegiacal candidate points in almuten scoring - on our test charts, switching doctrine changed which point won the almuten on 3 of 5 night charts.