Why is Advantest stock surging today?

Advantest stock surged 9.5% to ¥34,030 on Tuesday, rebounding sharply after AI company Anthropic filed its IPO prospectus with U.S. securities regulators on Monday, revealing that its revenue had grown roughly 100-fold over two years — a disclosure that dramatically eased investor concerns about the commercial viability of AI investment and sparked a broad rally in semiconductor-linked equities worldwide.

The overnight catalyst was amplified by a 2.8% jump in the Philadelphia Semiconductor Index on Monday — its largest single-session advance in weeks — which carried directly into Asian trading. Advantest had been among the hardest-hit names during the prior three-session selloff, with the stock and Tokyo Electron together responsible for more than 420 points of Nikkei 225 losses on October 26 alone, leaving the shares technically oversold and primed for a sharp mean-reversion bounce once sentiment turned.

Adding to the momentum, Advantest’s second-quarter fiscal 2026 results are scheduled for release on October 28, with the prior quarter having delivered 39.3% revenue growth and a 53.3% rise in operating profit, keeping expectations elevated.

Japan’s Nikkei 225 rose approximately 1.9% on the day, reversing a three-day losing streak as semiconductor and AI-related names led the recovery. The broader regional picture was similarly constructive, with South Korea’s KOSPI surging more than 4% as chip giants there also rebounded sharply.