USPS's Shift to OAuth 2.0 Breaks Magento—Simple Patching Won't Fix It

USPS has migrated from legacy Web Tools to REST API v3 with OAuth 2.0, rendering Magento's built-in USPS module non-functional and causing shipping rates to fail across stores. The issue extends beyond new endpoints—it requires implementing OAuth token lifecycle management and adapting to new API request/response structures, which Magento's core carrier module was never architected to support. Merchants must act now to avoid continued service disruptions, choosing between a complex custom implementation or migrating to a third-party solution.