Chief Commercial Officer — Nathan Kroeker: The Chief Commercial Officer is departing following a planned transition period with a named internal successor, indicating an orderly succession rather than a sudden loss of leadership.

Unregistered Sales of Equity Securities. The information set forth in

Entry Into A Material Definitive Agreement. Amended and Restated Limited Liability Company Agreement for Frontier On August 4, 2026, Eos Energy Enterprises, Inc. (the “ Company ”), CCM Frontier JV Holdco, LLC, an affiliate of Cerberus Capital Management, L.P. (“ CCM Frontier ”) and HBC MSF Capital Solutions Blocker II LLC, an affiliate of Hudson Bay Capital Management LP (“ HBC ”) entered into an Amended and Restated Limited Liability Company Agreement (the “ A&R LLCA ”) for Frontier Power US…

and in the accompanying Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act regardless of any general incorporation language in such filing, unless expressly incorporated by specific reference in such filing.

and in the accompanying Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act regardless of any general incorporation language in such filing, unless expressly incorporated by specific reference in such filing.

preferred stock director and Class III director — Greg Nixon and Nathaniel Fick: Greg Nixon resigned to devote more time to other business ventures, and Nathaniel Fick was appointed as a preferred stock director with Haiyan Song succeeding him as Class III director.

Other Events. Rights Offering On July 2, 2026, Eos Energy Enterprises, Inc. (the “Company”) issued a press release announcing the commencement of its previously-announced rights offering pursuant to a shelf registration statement filed on Form S-3 (File No. 333-295819) (the “Registration Statement”) with the Securities and Exchange Commission (“SEC”) on May 13, 2026, and the prospectus supplement relating to the rights offering filed with the SEC on July 2, 2026 (the prospectus supplement tog…

Other Events. Securities Purchase Agreement On July 1, 2026, the Company issued 13,683,634 shares (the “Shares”) of the Company’s common stock, par value $0.0001 per share (“Common Stock”), and 6,004,378 warrants (the “Warrants” and, together with the Shares, the “Securities”), each warrant to purchase one share of common stock at an exercise price of $5.481 per share, in its previously announced registered direct offering (the “Offering”) pursuant to that certain securities purchase agreemen…

Entry Into or Amendment of a Material Definitive Agreement. On June 30, 2026, Eos Energy Enterprises Inc. (the “ Company ”) entered into a binding amended and restated term sheet (the “ A&R Term Sheet ”) with CCM Frontier JV Holdco, LLC, an affiliate of Cerberus Capital Management, L.P. (“ CCM Frontier ”), and HBC MSF Capital Solutions Blocker II LLC, an affiliate of Hudson Bay Capital Management LP (“ HBC ”), which provides for upon the closing of the transactions contemplated by the A&R Ter…

Other Events. Second Limited Consent to DOE Loan Agreement On June 26, 2026, the Company entered into a limited consent (the “ Second DOE Limited Consent ”) to its Loan Guarantee Agreement, dated November 26, 2024, as amended by that certain Amendment to Loan Guarantee Agreement, dated as of March 25, 2025, and as further amended by that certain Second Amendment to Loan Guarantee Agreement, dated as of February 13, 2026, by and between the Company and the United States Department of Energy, a…

Entry into a Material Definitive Agreement. On May 12, 2026, Eos Energy Enterprises Inc. (the “ Company ”) entered into a binding term sheet (the “ Term Sheet ”) with CCM Frontier JV Holdco, LLC, an affiliate of Cerberus Capital Management, L.P. (“ CCM Frontier ”), which provides for, upon the closing of the transactions contemplated by the Term Sheet, the formation of a joint venture between the Company and CCM Frontier through Frontier Power USA Parent, LLC, a Delaware limited liability com…

and in the accompanying Exhibit 99.2 shall not be deemed “filed” for purposes of Section 18 of the Exchange Act, or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act regardless of any general incorporation language in such filing, unless expressly incorporated by specific reference in such filing. Forward-Looking Statements and Important Information Except for the historical information contained herein, the matters set forth herein are…

and in the accompanying Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act regardless of any general incorporation language in such filing, unless expressly incorporated by specific reference in such filing.

Unregistered Sales of Equity Securities. The information set forth in

Chief Financial Officer — Alessandro Lagi: Eos Energy Enterprises appointed Alessandro Lagi as the new Chief Financial Officer.

and in the accompanying Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act regardless of any general incorporation language in such filing, unless expressly incorporated by specific reference in such filing.

Chief Administration Officer — Michelle Buczkowski: An employment agreement was signed with the Chief Administration Officer, Michelle Buczkowski.

Director — Nathaniel Fick: Appointment of Nathaniel Fick as a Class III director.

and in the accompanying Exhibit 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act regardless of any general incorporation language in such filing, unless expressly incorporated by specific reference in such filing.

Entry into a Material Definitive Agreement. As previously disclosed, on November 26, 2024, Eos Energy Enterprises, Inc., a Delaware corporation (the “Company”), entered into a loan guarantee agreement, which was subsequently amended by that certain Amendment to Loan Guarantee Agreement entered into on March 25, 2025, by and between the Company and the United States Department of Energy, an agency of the United States of America (the “DOE” and, such agreements collectively, the “Loan Agreement…

non-executive chair of the Board — Russell Stidolph: Resigned to devote more time to other business ventures with a named successor.

Other Events. On November 19, 2025, the Company entered into certain share purchase agreements, by and between the Company and certain purchasers (the “Purchasers” and, such agreements, the “Purchase Agreements”), pursuant to which the Company agreed to sell 35,855,647 shares of the Company’s common stock in a registered direct offering at a price of $12.78 per share (the “Offering”). The issuance and sale of 35,855,647 shares of the Company’s common stock was completed on November 24, 2025.…

The Notes were issued to the initial purchasers in reliance upon Section 4(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”), in transactions not involving any public offering. The Notes were resold by the initial purchasers to persons whom the initial purchasers reasonably believe are “qualified institutional buyers,” as defined in, and in accordance with, Rule 144A under the Securities Act. Any shares of the Company’s common stock that may be issued upon conversion of t…

Creation of a Direct Financial Obligation or an Obligation Under an Off-Balance Sheet Arrangement of a Registrant. The disclosure set forth in

Entry Into or Amendment of a Material Definitive Agreement. Convertible Notes On November 24, 2025 (the “Closing Date”), Eos Energy Enterprises, Inc. (the “Company”) issued $600,000,000 aggregate principal amount of its 1.75% Convertible Senior Notes due 2031 (the “Notes”). The Notes were issued pursuant to, and are governed by, an indenture (the “Indenture”), dated as of the Closing Date, between the Company and Wilmington Trust, National Association, as trustee (the “Trustee”). Pursuant to…