Key Highlights

● Teradyne closed at $308.75 on October 22, down $36.74.

● The Philadelphia Semiconductor Index had its biggest one-day drop since June 23.

● Teradyne makes automated test equipment and robots for factories and warehouses.

● Teradyne reports third-quarter results on October 27.

Teradyne (NASDAQ:TER) plunged on Thursday, October 22, 2026, closing at $308.75, down $36.74, and ranking among the biggest losers in the S&P 500 as chip-test stocks were swept up in a broad semiconductor rout.

No company-specific news was found to explain the slide. Teradyne fell as investors dumped semiconductor and AI-hardware stocks after a supply warning from Lam Research (NASDAQ:LRCX) and heavy AI spending plans from Meta Platforms (NASDAQ:META).

Caught in the rout

The Philadelphia Semiconductor Index had its biggest one-day drop since June 23. Lam Research tumbled after warning that supply constraints would cap its growth, and fellow equipment makers KLA (NASDAQ:KLAC) and Applied Materials (NASDAQ:AMAT) sank. Nvidia (NASDAQ:NVDA) closed at $212.21 and was one of the biggest drags on the S&P 500, according to market reports.

Lam's chief executive said cleanroom and component constraints will "limit chip makers and equipment companies' ability to fully meet end demand" into 2027. Although Teradyne makes test equipment rather than the tools used to fabricate chips, investors sold the broader semiconductor-equipment complex.

Smaller test and measurement names also fell. Electronic-measurement company Keysight Technologies (NYSE:KEYS) closed at $311.52, while small caps such as FormFactor (NASDAQ:FORM) and Cohu (NASDAQ:COHU) also slid as the semicap selloff spread.

What Teradyne does

Teradyne is a leading maker of automated test equipment, the systems chipmakers use to check that semiconductors work properly before they are shipped. Its testers are used for processors, memory chips and other devices, including the advanced chips that power AI data centers. The company also has a robotics business that makes collaborative robots and autonomous mobile robots for factories and warehouses.

Demand for its testers is tied to the volume and complexity of chips being made, which links Teradyne closely to the AI build-out. That connection, which had helped the stock, made it vulnerable on a day when investors questioned the pace and financing of AI spending.

The AI capital scare

The quarterly report from Meta Platforms showed heavy capital spending and negative free cash flow, raising fresh doubts about the payback on the enormous sums being invested in AI. Nvidia's chief executive added to the unease. "The demand of the capital is much greater than the availability of the capital," he said.

The S&P 500 fell 93.74 points to 7,663.43, its worst session since July, and the Nasdaq Composite tumbled 694 points to 26,008.86, its steepest drop since June 5. The Nasdaq lost about $1 trillion in market value.

Elsewhere, the market held up much better. About two of every three S&P 500 stocks rose, according to market reports, as investors rotated into consumer staples, health care, utilities and homebuilders. Treasuries rallied strongly too, with the 10-year yield falling back below a closely watched threshold for the first time since September 22, while the Cboe Volatility Index rose 2.35 points to 19.03.

Teradyne's October 27 Report Looms

Teradyne reports its third-quarter results on October 27, giving investors a direct read on demand for chip testers and the impact of the industry's supply constraints. Its commentary on AI-related test demand will be closely scrutinized after Thursday's selloff. Intel (NASDAQ:INTC)'s results on October 29 and capital spending updates from Microsoft (NASDAQ:MSFT), Alphabet (NASDAQ:GOOGL) and Amazon (NASDAQ:AMZN) next week will also help determine whether the semiconductor rout deepens or begins to stabilize.