Form 4 Filing for ATI INC.

Timothy J. Harris, Senior VP and CDIO of ATI INC., sold 9,000 shares of common stock on September 21, 2026, for a total of $1,726,380. The sale was executed under a 10b5-1 trading plan established on May 21, 2026, for personal tax and estate planning purposes. Following the transaction, Mr. Harris owns 88,187 shares of ATI INC. stock. This filing is a report of insider transactions.