Vault is a handheld terminal built around an ESP32-S3, a 128×64 OLED, and a 4.26-inch e-paper display that acts as a physical front end for an OpenClaw AI agent and a locally hosted LLM (gpt-oss-120b on an NVIDIA DGX Spark via TensorRT-LLM). The core design principle separates two display rhythms: the OLED handles live operational state (timers, input, connectivity), while the e-paper holds completed results for stable reading. The ESP32 never runs inference; it sends compact JSON over HTTP to a Python broker on the LAN that dispatches to chat, agent, or RPG endpoints. The post covers hardware failures encountered during the 67-day build — including I²C pull-up workarounds, OLED overvoltage from a boost regulator, SPI pin-matrix conflicts, and a stack buffer overwrite from a sizeof bug. A key design insight distilled from the project: separate transient machine activity (state) from durable user value (results), and keep unbounded model work behind a broker. The project is open source under MIT.
