The HC-12 433MHz serial bridge has no built-in retry or CRC at the UART passthrough level. Here is a practical application-level framing scheme with CRC-16, timeout-based retry, and backoff that actually worked on a live link — plus what went wrong.
The ESP32-C3 datasheet promises 5–7 µA deep sleep. Your dev board draws thousands of times more. Here is what is actually leaking current in a XIAO ESP32C3 and how to measure it yourself.