porphyry-quadrant-overlay-1.0.0 calls Swiss Ephemeris houses_ex with house-system code O at the chart Julian day, terrestrial latitude, and longitude. The returned twelve cusp longitudes and exact angle array are normalized to the 0–360 degree interval.

Planet interval assignment

For cusp i and its following cusp, Stelliums measures the forward normalized zodiacal arc. A planet belongs to the first interval for which its forward offset from cusp i is less than that arc; an exact cusp belongs to the house beginning at that cusp. This handles the 360-to-0 wrap without string or sign heuristics.

Reproducibility and boundary

• Output includes exactly twelve normalized cusps, a Porphyry house for every traditional planet, and porphyry-quadrant-overlay-1.0.0.
• Four frozen charts cover North America, the international date line, the southern hemisphere, and Tromsø at polar latitude.
• Whole Sign place calculation and all existing topical interpretation remain unchanged.
• Saved facts preserve both frameworks; older saved charts simply omit the unavailable overlay until recalculated.