* 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.
* Fix - Validate empty Origin Postcode: show admin notice on save and skip API requests.
* Fix - FCPIS rates incorrectly filtered for valid custom boxes.
* Tweak - Hide product-level "Envelope" checkbox when REST API is active, as it only affects Legacy (SOAP) API rates.
* Tweak - WooCommerce 10.7 Compatibility.
* Fix - Weight based shipping calculations with fractional quantities.
* Fix - Set minimum girth to 1" to prevent 400 errors with small dimensions.
* Fix - Filter out First-Class Package International Service rates for packages exceeding USPS dimensional limits.
* Fix - Restrict international First-Class Mail letter and envelope rates to items with zero declared value.
* Tweak - Split international First-Class into separate Mail and Package services for accurate rate naming.
* Tweak - Show packing method label in rate metadata for all packing methods.
* Tweak - Add rate description and mail class to rate metadata.
* Add - Custom Flat Rate Boxes/Envelopes with adjustable dimensions to account for bulging allowed by USPS.
* Fix - Inaccurate International First-Class Mail letter rates.
* Fix - Add missing Weight based shipping support to First-Class.
* Fix - Filter out Cubic pricing rates and improve flat rate filtering.
* Fix - Make fractional item quantity rates calculations more accurate.
* Tweak - WooCommerce 10.5 compatibility.
* Add - USPS First-Class Mail Rates support to REST API.
* Add - "Display Delivery Times" setting to toggle estimated delivery times on shipping rates.
* Fix - Compatibility issues with Product decimal quantities.
* Add - USPS API migration notices to inform merchants about upcoming API changes and ensure smooth transition.