Claude Code wastes user quota with repeated trial-and-error instead of verifying calculations before coding

Hi,
Please help me.

MiniNav is a compact bathymetric
survey system built on ESP32. It combines:

• UM982 RTK GPS (dual antenna, centimeter accuracy) for position
• Airmar D800 sonar for water depth measurement
• Wi-Fi web UI — I connect my tablet/phone to the ESP32's hotspot and see a live map with depth data, sonar

echogram, and survey logging

The issue occurred while implementing the sonar echogram panel in the web UI. The panel needed to display
correctly on my Samsung tablet where Samsung Internet browser calculates vh CSS units from the full screen
height (including the system navigation bar), causing the canvas to extend beyond the visible screen. Despite
having the correct mathematical approach available, Claude Sonnet 4.6 kept changing the implementation
repeatedly without verifying the calculation first, consuming my daily token quota without resolving the
issue.

<img width="991" height="1652" alt="Image" src="https://github.com/user-attachments/assets/6951f330-2720-403a-8132-534b4376d037" />

<img width="991" height="1652" alt="Image" src="https://github.com/user-attachments/assets/3c500bb1-f64d-44a5-8d88-29236eca3c3b" />