SnapHeater U1 controls heater-related logic and must be treated as safety-relevant firmware.

• Physical heater output is disabled by default.
• Heater control requires compile-time enablement and runtime safety validation.
• Output Safety Latch must confirm board setup before live heater control.
• Unknown GPIOs must remain disabled until verified on real hardware.

SnapHeater U1 uses U1 Symbiont Mode for safe cooperation with Snapmaker U1.

Printer-critical actions remain blocked by design, including print cancel, print pause, motion, extrusion, nozzle temperature and bed temperature changes.

Optional chamber-related cooperation may be enabled only for safe, whitelisted climate/ventilation behavior when the user explicitly allows it.

When reporting a safety issue, include:

• firmware version,
• hardware revision if known,
• board pin mapping used,
• heater/fan output configuration,
• sensor readings,
• event log or incident report,
• steps to reproduce.