MKSI is trading 4.7% down at $333.00 in pre-market. - The stock is under pressure due to broader weakness in the semiconductor sector, fueled by warnings that the AI trade may be losing steam. - Recent insider selling, including by CEO John Tseng-Chung Lee and a director, has also contributed to the cautious sentiment. - This comes after the company recently beat Q1 2026 earnings and revenue forecasts, but investors may be reassessing valuations in the broader tech market.