Treat direction as structure
RTL changes reading order, alignment, navigation, table scanning, icon direction, form flow, and diagram logic. Mirroring the final CSS cannot repair an LTR-only information model.
Design terminology ownership
Operational terms need one approved meaning in each language. Build a glossary, identify terms that stay in English, and define how mixed-direction text is displayed.
Test real density
Arabic and English labels rarely occupy equal space. Test long names, tables, validation messages, mobile navigation, and exports with production-like content.