The "Round Trip" is the hidden tax of modern application development. For years, we’ve conditioned ourselves to believe that any operation involving intelligence—extracting data from a receipt, summarizing a medical report, or parsing an invoice—requires a journey to the cloud. We bundle a file, upload it to a server, wait for a massive Large Language Model (LLM) like GPT-4 or Gemini Pro to process it, and then download the result. This architecture, while powerful, comes with a heavy price: a compromise on user privacy, a dependency on network stability, and a linear increase in API costs. But the landscape of mobile development is shifting. With the release of Gemini Nano and AICore , Android developers can now move the brain of the operation directly onto the device. In this deep dive, we’re going to explore how to implement a production-grade Document Parsing Engine that runs entirely on-device, leveraging modern Kotlin features and the latest GenAI system services.…