---
type: guidelines
---
# Display client guidelines

## 1. The client knows the contract, not the car
- No CAN frame IDs, no DBC knowledge, no device paths. Topic names and payload
  schemas only.  
- If rendering something requires new knowledge of the vehicle, that knowledge
  belongs upstream in the decoder, not here.

## 2. Render whatever state exists, immediately
- Retained topics mean a client connecting mid-drive has state at once. Never
  block the first paint on a full set of signals.  
- Missing is a normal state and must have a visual form. It is not an error.

## 3. Design for a split screen
- The screen may be shared with another app. Do not assume full width.

## 4. To be added