Flyline is similar to ble.sh but replaces readline entirely with a ratatui terminal app.
With flyline, you get undo/redo support, tooltips, fuzzy auto completions, fuzzy history search, agent integration, mouse support, text selection, full prompt customization, and more!
And it all runs in the same process as Bash. See the readme on how to install it (no sudo required).
The user could input the colours their app uses and be shown themes that it won't look good on