2026-05-11 – version 5.5.5
* Add – Debug logging at silent exit points in rate calculation.
* Fix – Don’t cache transient USPS API errors (429, 5xx) in rate response transients.
* Tweak – Promote genuine API failures from debug to error log level for visibility.
* Tweak – Update Jetpack Autoloader to v5.
2026-04-13 – version 5.5.4
* Fix – Correct large envelope (flat) classification to match USPS standards — items that exceed any (previously all) of letter dimension now qualify as flats.
* Fix – Legacy API credential validation no longer runs when switching to REST API, preventing headers-already-sent warnings.