Enterprises rely on device-based customer interactions, making local app performance crucial for user experience. Testing apps across numerous devices is essential but difficult due to procurement costs, complexity, and flaky tests. This often leads developers to rely on limited personal device testing, jeopardizing broad compatibility. Google Cloud is launching Developer Device Platform (DDP) in public preview to address these challenges. DDP offers managed cloud access to real physical devices and virtual emulators, evolving Firebase Test Lab. It supports agentic development, allowing developers to use preferred agents for coding, testing, debugging, and optimization. DDP's Device Streaming API enables interactive debugging by remotely accessing and interacting with apps on chosen devices. The Device Run API facilitates parallel testing across hundreds of devices within CI/CD pipelines, helping pinpoint and resolve issues. DDP enhances agent capabilities, enabling them to execute complex journeys, identify visual artifacts, and analyze on-device performance. Integrations with Android Studio and CLI, along with agent skills, will accelerate development and code optimization. DDP supports smart sharding and auto-retries for efficient parallel testing and faster error resolution. The platform is available to all Google Cloud users, utilizing a pay-per-minute model during the public preview.