July 2026: Implemented Ractor-safe sharing for ActiveModel in Shopify/rails, enabling objects to be used across Ruby Ractors with safe memoization and partial path usage. Key changes include freezing the result of ActiveModel#to_partial_path to ensure stable strings inside a Ractor, and freezing ActiveModel::Name instances to avoid memoization-induced recursion. Removed problematic memoization in ActiveModel#model_name to allow cross-Ractor access and added eager initialization of underlying values. Tests were expanded with an isolated-model-class scenario and I18n stubbing to validate Ractor-safe behavior. These changes reduce cross-thread state coupling, improve concurrency stability, and unlock higher throughput for Rails apps leveraging Ractor-based servers. The work is backed by commits 18fdd2f2c53845551c39d2fc35afec1d8c635dcc and c4dcf552cfc15268a1b448ec6c2f2a2f89d8be52.