Hinata dawn-crowned can't cast cost reduced spells unless you have enough mana to cast full cost spell

When Playing Hinata, the client doesnt let you cast spells unless you can generate enough mana to pay the full price, then after declaring the targets, the reduced cost is applied

Example: opponent has 3 creatures in play, you have hinata and 2 untapped islands, you cant play mystic confluence to bounce all 3 creatures, after your turn comes up, and you untap all your lands, you can now cast mystic confluences choose same mode 3 times, and pay UU for final result

Start by reproducing the reported Hinata, Dawn-Crowned and Mystic Confluence scenario with three opposing creatures and two untapped Islands. Trace the client-side spell-casting cost validation before targets are declared. Done means cost-reduced spells can be selected when only the reduced cost is available, while the existing target selection and final payment remain correct.

Written by the indexing model from the issue text.