Simlock leases each coding agent its own iOS simulator, Android emulator, or enrolled phone, so parallel mobile tests stop sharing one device. Several agents pointed at the same simulator will install over each other's builds, erase a device mid-test, or shut it down. An agent asks for a platform and a model and gets a device back that is already booted and checked, and no other agent can take it until the lease is released. If none is free, Simlock creates one up to what the machine can run, queues the request when the machine is full, and cleans up devices nobody is using. Install is npm i -g simlock, and the daemon starts on demand the first time a command runs. Agents reach it through the CLI, an MCP server, HTTP, or agent-device. The simulators and emulators it manages live in a separate device set and use a separate adb server, so they stay out of Xcode's device list and a normal adb devices listing. Simlock will not change a simulator or emulator it did not create. One Mac is enough to start. A gateway that owns no devices can then front more Macs and Linux workers. Those workers dial out, so a machine behind NAT can join, and each request goes to a warm device first, then to the machine with the most room. Callstack, founded in Wrocław in 2016 to build and scale React Native products, released Simlock as a free, MIT-licensed project from its incubator. Callstack engineer Szymon Chmal introduced the launch. A USB-connected iPhone, iPad, or Android phone can be enrolled and leased the same way as a simulator. Ending that lease does not reset settings, files, accounts, or keychain items, and it does not touch App Store or TestFlight apps or clear data for apps already on the enrollment list. Apps added during the lease are removed unless an admin adds them to that list, so the next agent does not inherit the previous build.