Other Events. The Board of Directors of Avidia Bancorp, Inc. has authorized a stock buyback plan, effective August 4, 2026, under which the Company may repurchase up to $30 million in value of its common stock. Repurchases may be made from time to time on the open market and in privately negotiated transactions, and through the use of trading plans intended to qualify under Rule 10b5-1 under the Exchange Act. The extent to which the Company repurchases shares and the size and timing of these…

Results of Operations and Financial Condition. On July 23, 2026, Avidia Bancorp, Inc. (the “Company”), the holding company of Avidia Bank, issued a press release announcing the unaudited consolidated financial results of the Company for the three and six months ended June 30, 2026 and the declaration of a dividend of $0.06 per share payable on or about August 27, 2026 to stockholders of record as of the close of business on August 18, 2026. A copy of the press release is furnished as Exhibit…

Results of Operations and Financial Condition. On April 23, 2026, Avidia Bancorp, Inc. (the “Company”), the holding company of Avidia Bank, issued a press release announcing the unaudited consolidated financial results of the Company for the quarter ended March 31, 2026 and the declaration of a dividend of $0.05 per share payable on or about May 28, 2026 to stockholders of record as of the close of business on May 19, 2026. A copy of the press release is furnished as Exhibit 99.1 hereto and i…

Results of Operations and Financial Condition. On January 29, 2026, Avidia Bancorp, Inc. (the “Company”), the holding company of Avidia Bank, issued a press release announcing the unaudited consolidated financial results of the Company for the quarter and year ended December 31, 2025. A copy of the press release is furnished as Exhibit 99.1 hereto and incorporated herein by reference.

Other Events. On January 29, 2026, the Board of Directors of Avidia Bancorp, Inc. declared a dividend of $0.05 per share. The dividend will be paid on or about February 26, 2026 to stockholders of record as of the close of business on February 17, 2026. A copy of the press release announcing the declaration of the dividend is furnished as Exhibit 99.1 hereto and incorporated herein by reference.

Changes in Registrant’s Certifying Accountant. On November 12, 2025, the Audit Committee of the Board of Directors (the “Audit Committee”) of Avidia Bancorp, Inc. (the “Company”) approved the dismissal of Berry, Dunn, McNeil & Parker, LLC, the Company’s independent registered public accounting firm, effective as of November 12, 2025. Concurrently, the Audit Committee approved the engagement of BDMP Assurance, LLP as the Company’s new independent registered public accounting firm for the fisca…

Results of Operations and Financial Condition. On October 23, 2025, Avidia Bancorp, Inc. (the “Company”), the holding company of Avidia Bank, issued a press release announcing the unaudited consolidated financial results of the Company for the three and nine months ended September 30, 2025. A copy of the press release is furnished as Exhibit 99.1 hereto and incorporated herein by reference.

Director — Michael O. Gilles: Appointment of Michael O. Gilles to the Board of Directors and Audit Committee.

Results of Operations and Financial Condition. On August 1, 2025, Avidia Bancorp, Inc., the stock holding company of Avidia Bank, issued a press release announcing the unaudited consolidated financial results of Assabet Valley Bancorp, the former mutual holding company of Avidia Bank, for the three and six months ended June 30, 2025. A copy of the press release is furnished as Exhibit 99.1 hereto and incorporated herein by reference.