In the past 12 months, Ariana Grande, Rosalía and Lady Gaga all completed blockbuster arena tours in support of chart-topping albums, complete with large-scale production, choreography and outfit changes. But they also had something else in common: no opening acts.

While plenty of pop’s biggest artists are still booking buzzy support, tighter budgets, shorter pipelines to stardom and dwindling attention spans are changing the market for pop tour openers and the agents who book them.

“There’s all these different cost balance analyses going on,” says Nathaniel Marro, executive director of the National Independent Talent Organization (NITO), which advocates for a sustainable music ecosystem and supports independent music professionals. And while pop tours — especially at the arena level, where bigger budgets, capacity and higher ticket costs rule — are more immune to the industrywide financial squeeze, “everything is more expensive,” Marro maintains.…