Each River session receives an environment on a remote Mac for iOS work, while Android emulation runs on a separate Linux VM with nested virtualization. River connects over SSH and can edit code, build apps, run tests, operate simulators, collect screenshots or recordings, and create pull requests.
The company says it maintains a warm pool of Macs with its main branch checked out, tools installed, applications built, and caches warmed. It reports that initial compilation and checkout had taken more than 30 minutes; with the pool, the time from requesting a Mac to inspecting changes on a running device fell to a few minutes. Remote sessions are destroyed after use and replaced. A Live Preview streams iOS Simulator and Android Emulator sessions to a browser over WebSockets.
Shopify says River’s share of merged mobile pull requests rose from 6% to 61%. The source describes an internal Shopify system and does not establish external availability, pricing, capacity, reliability, or whether the reported adoption results transfer to other teams or codebases.