seamlessly
adv.happening in a smooth way without any gaps or problems. You use this when two things join together so perfectly that you cannot see where one ends and the other begins.
adv.moving from one state, part, or element to another without any visible interruption or difficulty.
“The new software integrates seamlessly with your existing apps.”
“The transition from the old manager to the new one happened seamlessly, with no disruption to daily operations.”
“The architect designed the glass extension to blend seamlessly with the original stone structure, creating a harmonious balance between modern and traditional styles.”
Typically follows the verb it modifies or the direct object.
From seamless + -ly.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.