Jakarta. Jakarta Composite Index (JCI) surged on Monday, riding a wave of optimism from regional markets after the US Supreme Court struck down most of President Donald Trump’s sweeping tariffs.

The benchmark index jumped 124.31 points, or 1.5%, to close at 8,396, moving within a range of 8,327 to 8,397.

Trading activity was robust, with volume reaching 49.10 billion shares and turnover totaling Rp 23.96 trillion ($1.42 million). Market frequency exceeded 3 million transactions. Gainers outpaced losers, with 468 stocks advancing, 206 declining and 142 unchanged.

Pilarmas Investindo Sekuritas said the JCI strengthened in line with gains across Asian markets, which reacted positively to the US Supreme Court’s ruling on President Donald Trump’s trade tariffs.

“The Supreme Court’s decision to cancel the previous tariff policy and replace it with a 10% tariff will be an important development for the business sector,” Pilarmas wrote in a research note on Monday.

However, the brokerage cautioned that markets remain alert to further policy moves from Washington. Over the weekend, Trump said he plans to raise global tariffs from 10% to 15%, following the court’s decision to scrap his earlier “reciprocal” tariff policy.

“As a result, the market appears to remain in wait-and-see mode, closely monitoring further developments in US tariff policy,” Pilarmas added.

The firm said the proposed increase has sparked concerns that trade agreements between the US and its partners could unravel, although senior US officials have reiterated that existing deals will remain in place. It also highlighted comments from US Trade Representative Greer, who noted that the measures would not affect Trump’s planned meeting with Chinese President Xi Jinping.

On the domestic front, Pilarmas said President Prabowo Subianto affirmed that Indonesia respects the US political process following the Supreme Court ruling, signaling that Jakarta is preparing for potential tariff adjustments.

The brokerage also pointed to improving sentiment from expectations that Trump’s new 15% global tariff, introduced after the court rejected broad reciprocal duties, signals a shift toward lower overall import levies.

“This indicates a shift toward lower overall import duties and could provide a modest boost to Indonesia’s exports in the short term,” Pilarmas said.

Across the region, Asian shares were mostly higher after the court ruling. Hong Kong led gains, with the Hang Seng index soaring 2.2% to 26,980. Markets in Japan and mainland China were closed for holidays. South Korea’s Kospi trimmed earlier gains to edge 0.1% lower to 5,809.

Benjamin Picton of Rabobank said the mixed reactions highlight the winners-and-losers effect of shifts in tariff policy, delivering a boost to countries that previously faced less favorable trade terms. He added that US tariff policy will remain a source of uncertainty as traders continue to price in evolving implications.

On Wall Street, US markets stayed relatively calm on Friday following the Supreme Court’s ruling. The S&P 500 rose 0.7% to 6,909.51, the Dow Jones Industrial Average gained 0.5% to 49,625.97, and the Nasdaq Composite climbed 0.9% to 22,886.07, even as investors digested weaker US growth data and faster inflation.