CONSTELLATION ENERGY GENERATION LLC

Item 1.01. Entry into a Material Definitive Agreement Registration Rights Agreement On January 7, 2026, in connection with the closing of the Mergers (as defined below), CEG Parent entered into a registration rights agreement (the “Registration Rights Agreement”) with certain of the former stockholders of Calpine who received shares of Stock Consideration (as defined below) in the Mergers, each of whom is listed on the signature pages thereto (the “RRA Parties”), pursuant to which the RRA Parties will have certain customary demand, “piggy-back” and shelf registration rights relating to the shares of Stock Consideration received by such RRA Parties as a result of the Mergers. Pursuant to the Registration Rights Agreement, CEG Parent is required to (subject to certain conditions and exceptions), use its reasonable best efforts to prepare and file with the U.S. Securities and Exchange Commission (“SEC”), on the closing date of the Mergers, a registration statement on Form S-3 that becomes effective upon filing registering for resale the shares of Stock Consideration received by the RRA Parties as a result of the Mergers. Under the Registration Rights Agreement, the RRA Parties are subject to a lock-up, subject to certain exceptions, with respect to the transfer of the shares of Stock Consideration received by such RRA Parties as a result of the Mergers, with one-half of such shares released from the lock-up on June 30, 2026, and the remaining one-half of such shares released from the lock-up on June 30, 2027. The foregoing description of the Registration Rights Agreement does not purport to be complete and is qualified in its entirety by reference to the Registration Rights Agreement, a copy of which is attached hereto as Exhibit 10.1 and incorporated herein by reference. Calpine Notes Upon the closing of the Mergers on January 7, 2026, Calpine (as a wholly owned subsidiary of Constellation) remained the issuer of (i) $1,400 million in aggregate principal amount of 5.125% Senior Notes due 2028 (the “2028 Senior Notes”) issued under Calpine’s indenture, dated December 27, 2019 (the “2028 Senior Notes Indenture”), between Calpine and Wilmington Trust, National Association, as trustee; (ii) $650 million in aggregate principal amount of 4.625% Senior Notes due 2029 (the “2029 Senior Notes”) issued under Calpine’s indenture, dated August 10, 2020 (the “2029 Senior Notes Indenture”), between Calpine and Wilmington Trust, National Association, as trustee; (iii) $850 million in aggregate principal amount of 5.000% Senior Notes due 2031 (the “2031 Senior Notes”) issued under Calpine’s indenture, dated August 10, 2020 (the “2031 Senior Notes Indenture” and, together with the 2028 Senior Notes Indenture and the 2029 Senior Notes Indenture, the “Calpine Unsecured Notes Indentures”), between Calpine and Wilmington Trust, National Association, as trustee; (iv) $1,250 million in aggregate principal amount of 4.500% Senior Secured Notes due 2028 (the “2028 Senior Secured Notes”) issued under Calpine’s indenture, dated December 20, 2019 (as supplemented, the “2028 Senior Secured Notes Indenture”), among Calpine, the guarantors party thereto from time to time and Wilmington Trust, National Association, as trustee; and (v) $900 million in aggregate principal amount of 3.750% Senior Secured Notes due 2031 (the “2031 Senior Secured Notes” and, together with the 2028 Senior Notes, the 2029 Senior Notes, the 2031 Senior Notes and the 2028 Senior Secured Notes, the “Calpine Notes”) issued under Calpine’s indenture, dated December 16, 2020 (as supplemented, the “2031 Senior Secured Notes Indenture” and, together with the 2028 Senior Secured Notes Indenture, the “Calpine Secured Notes Indentures”), among Calpine, the guarantors party thereto from time to time and Wilmington Trust, National Association, as trustee. Pursuant to the 2028 Senior Notes Indenture, interest on the 2028 Senior Notes accrues at a rate of 5.125% per annum on the outstanding principal amount thereof, payable semi-annually on March 15 and September 15 of each year. The 2028 Senior Notes will mature on March 15, 2028. Prior to March 15, 2026, Calpine may on any one or more occasions redeem all or a portion of the 2028 Senior Notes at a price equal to 100.854% of the principal amount of the 2028 Senior Notes plus accrued and unpaid interest to, but excluding, the redemption date. On and after March 15, 2026, Calpine may on any one or more occasions redeem all or a portion of the 2028 Senior Notes at par plus accrued and unpaid interest to, but excluding, the redemption date. Pursuant to the 2029 Senior Notes Indenture, interest on the 2029 Senior Notes accrues at a rate of 4.625% per annum on the outstanding principal amount thereof, payable semi-annually on February 1 and August 1 of each year. The 2029 Senior Notes will mature on February 1, 2029. Prior to February 1, 2026, Calpine may on any one or more occasions redeem all or a portion of the 2029 Senior Notes at a price equal to 101.156% of the principal amount of the 2029 Senior Notes plus accrued and unpaid interest to, but excluding, the redemption date. On and after February 1, 2026, Calpine may on any one or more occasions redeem all or a portion of the 2029 Senior Notes at par plus accrued and unpaid interest to, but excluding, the redemption date. Pursuant to the 2031 Senior Notes Indenture, interest on the 2031 Senior Notes accrues at a rate of 5.000% per annum on the outstanding principal amount thereof, payable semi-annually on February 1 and August 1 of each year. The 2031 Senior Notes will mature on February 1, 2031. Prior to February 1, 2026, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Notes at a price equal to 100% of the principal amount of the 2031 Senior Notes plus a “make-whole” premium and accrued and unpaid interest to, but excluding, the redemption date. Beginning on February 1, 2026 until February 1, 2027, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Notes at a price equal to 102.500% of the principal amount of the 2031 Senior Notes plus accrued and unpaid interest to, but excluding, the redemption date. Thereafter until February 1, 2028, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Notes at a price equal to 101.667% of the principal amount of the 2031 Senior Notes plus accrued and unpaid interest to, but excluding, the redemption date. Thereafter until February 1, 2029, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Notes at a price equal to 100.833% of the principal amount of the 2031 Senior Notes plus accrued and unpaid interest to, but excluding, the redemption date. Thereafter, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Notes at par plus accrued and unpaid interest to, but excluding, the redemption date. Pursuant to the 2028 Senior Secured Notes Indenture, interest on the 2028 Senior Secured Notes accrues at a rate of 4.500% per annum on the outstanding principal amount thereof, payable semi-annually on February 15 and August 15 of each year. The 2028 Senior Secured Notes will mature on February 15, 2028. Prior to February 15, 2026, Calpine may on any one or more occasions redeem all or a portion of the 2028 Senior Secured Notes at a price equal to 100.750% of the principal amount of the 2028 Senior Secured Notes plus accrued and unpaid interest to, but excluding, the redemption date. On and after February 15, 2026, Calpine may on any one or more occasions redeem all or a portion of the 2028 Senior Secured Notes at par plus accrued and unpaid interest to, but excluding, the redemption date. Pursuant to the 2031 Senior Secured Notes Indenture, interest on the 2031 Senior Secured Notes accrues at a rate of 3.750% per annum on the outstanding principal amount thereof, payable semi-annually on March 1 and September 1 of each year. The 2031 Senior Secured Notes will mature on March 1, 2031. Prior to March 1, 2026, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Secured Notes at a price equal to 100% of the principal amount of the 2031 Senior Secured Notes plus a “make-whole” premium and accrued and unpaid interest to, but excluding, the redemption date. Beginning on March 1, 2026 until March 1, 2027, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Secured Notes at a price equal to 101.875% of the principal amount of the 2031 Senior Secured Notes plus accrued and unpaid interest to, but excluding, the redemption date. Thereafter until March 1, 2028, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Secured Notes at a price equal to 101.250% of the principal amount of the 2031 Senior Secured Notes plus accrued and unpaid interest to, but excluding, the redemption date. Thereafter until March 1, 2029, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Secured Notes at a price equal to 100.625% of the principal amount of the 2031 Senior Secured Notes plus accrued and unpaid interest to, but excluding, the redemption date. Thereafter, Calpine may on any one or more occasions redeem all or a portion of the 2031 Senior Secured Notes at par plus accrued and unpaid interest to, but excluding, the redemption date. Subject to certain qualifications and exceptions, the Calpine Unsecured Notes Indentures, among other things, limit Calpine’s ability and the ability of certain covered subsidiaries of Calpine to create or incur liens and consolidate, merge or transfer all or substantially all of Calpine’s assets and the assets of Calpine’s subsidiaries on a combined basis. Subject to certain qualifications and exceptions, the Calpine Secured Notes Indentures, among other things, limit Calpine’s ability and the ability of the guarantors of the 2028 Senior Secured Notes and the 2031 Senior Secured Notes to incur or guarantee additional first lien indebtedness; enter into certain types of commodity hedge agreements that can be secured by first lien collateral; enter into sale and leaseback transactions; create or incur liens; and consolidate, merge or transfer all or substantially all of Calpine’s assets and the assets of Calpine’s restricted subsidiaries on a combined basis. The foregoing description of the Calpine Notes and the indentures governing the Calpine Notes does not purport to be complete and is qualified in its entirety by reference to the Calpine Notes and the indentures governing the Calpine Notes, including the supplemental indentures thereto (as applicable), copies of which are attached hereto as Exhibits 4.1, 4.2, 4.3, 4.4, 4.5, 4.6 and 4.7 and incorporated herein by reference. CCFC Term Loan Upon the closing of the Mergers on January 7, 2026, Calpine Construction Finance Company, L.P., an indirect, wholly owned subsidiary of Calpine (“CCFC”), remains party to a Credit Agreement with Citibank, N.A. (as successor to Credit Suisse AG, Cayman Islands Branch), as administrative agent and as collateral agent, and the lenders party thereto from time to time, originally dated December 15, 2017 (as amended, amended and restated and supplemented, the “CCFC Term Loan Agreement”). The CCFC Term Loan Agreement consists of a first lien senior secured term loan (the “CCFC Term Loan”). On August 2, 2023, CCFC and the other parties thereto amended and restated the original CCFC Term Loan Agreement. On June 6, 2024, CCFC completed a repricing of the CCFC Term Loan to reduce the applicable spread over the SOFR rate from 2.25% to 2.00% and remove the quarterly principal payments prior to the maturity of the debt. On September 16, 2024, CCFC completed a refinancing to increase the total notional principal amount of the CCFC Term Loan from $1.244 billion to $1.875 billion. Subsequently, on November 18, 2025, CCFC incurred a replacement tranche of first lien senior secured term loans, which increased its existing CCFC Term Loan by $225 million and repriced such existing CCFC Term Loan to reduce the applicable spread over the SOFR rate from 2.00% to 1.75% under the CCFC Term Loan Agreement. The CCFC Term Loan matures on July 31, 2030. The foregoing description of the CCFC Term Loan Agreement and the CCFC Term Loan does not purport to be complete and is qualified in its entirety by reference to the CCFC Term Loan Agreement, including amendments thereto, copies of which are attached hereto as Exhibits 10.2, 10.3, 10.4, 10.5 and 10.6 and incorporated herein by reference. GPC Term Loan Upon the closing of the Mergers on January 7, 2026, Geysers Power Company, LLC, an indirect, wholly owned subsidiary of Calpine, and certain of its subsidiaries acting as guarantors remain parties to a Credit Agreement with MUFG Bank, Ltd., as administrative agent, MUFG Union Bank, N.A., as first lien collateral agent, and the lenders party thereto, dated June 9, 2020 (as amended, on November 9, 2021 and May 31, 2022, and as otherwise amended, the “GPC Term Loan Agreement”). The GPC Term Loan Agreement consists of a $1,771 million senior secured term loan facility (of which $1,415 million term loans are currently outstanding (the “GPC Term Loans”)) and a $250 million letter of credit facility. The GPC Term Loans bear interest at Term SOFR plus a percentage equal to (a) until May 31, 2025, 1.5%, (b) from such date until May 31, 2028, 1.625%, and (c) from such date until the maturity of the GPC Term Loans, 1.75% (plus, in each case, applicable Term SOFR adjustment). The GPC Term Loans mature on May 31, 2029. The foregoing description of the GPC Term Loan Agreement and the GPC Term Loans does not purport to be complete and is qualified in its entirety by reference to the GPC Term Loan Agreement, including amendments thereto, copies of which are attached hereto as Exhibits 10.7, 10.8 and 10.9 and incorporated herein by reference. Section 2 - Financial Information

Item 2.01. Completion of Acquisition or Disposition of Assets As discussed in the Introductory Note above, on January 7, 2026, CEG Parent and Constellation completed the previously announced transactions contemplated by the Merger Agreement. Pursuant to the Merger Agreement, (i) on January 2, 2026, Calpine, New Company and Company Merger Sub completed an internal reorganization pursuant to which Company Merger Sub merged with and into Calpine, with Calpine surviving the merger as a wholly owned subsidiary of New Company and the holders of Company Common Shares and Company Restricted Stock Units becoming holders of Common Shares and Restricted Stock Units of New Company (“RSUs”), and on January 5, 2026, Calpine converted into a Delaware limited liability company (the “Reorganization”), (ii) on January 7, 2026, at the First Effective Time, First Merger Sub merged with and into New Company, with New Company surviving the merger as a wholly owned subsidiary of Constellation and (iii) on January 7, 2026, at the Second Effective Time, New Company merged with and into Second Merger Sub, with Second Merger Sub surviving the merger as a wholly owned subsidiary of Constellation (clauses (ii) and (iii), collectively, the “Mergers”). As a result of the Reorganization and the Mergers, Calpine became a wholly owned subsidiary of Constellation. The merger consideration consisted of (i) an aggregate of 50,000,000 newly issued shares of common stock, no par value, of CEG Parent (the “Stock Consideration”) and (ii) $4.50 billion in cash minus the amount of Company Expenses. As a result of the Mergers, the former stockholders of Calpine received approximately 13.8% of the outstanding CEG Parent common stock in the aggregate based upon the outstanding shares of CEG Parent common stock as of January 6, 2026. In connection with closing of the Mergers, outstanding Calpine equity-based awards were treated as follows: At the First Effective Time, each outstanding RSU issued by New Company in respect of Company Restricted Stock Units issued by Calpine pursuant to the Calpine Corporation 2024 Equity Incentive Plan (whether vested or unvested) was fully vested, canceled and converted into the right to receive, in respect of each such RSU: (i) the Per Share Cash Consideration, without interest, (ii) the Per Share Stock Consideration, (iii) any cash in lieu of fractional shares of CEG Parent common stock was paid in accordance with the Merger Agreement and (iv) an amount in cash (without interest and less any applicable taxes required to be withheld) equal to any dividend equivalents with respect to such RSU that were unpaid as of the First Effective Time (which amounts in respect of such dividend equivalents were first satisfied from any escrow account related thereto). The foregoing description of the Merger Agreement does not purport to be complete and is qualified in its entirety by reference to the Merger Agreement, a copy of which was attached as Exhibit 2.1 to the Current Report on Form 8-K dated January 13, 2025 (File No. 001-41137) and is incorporated herein by reference. The Merger Agreement has been incorporated by reference into this Current Report on Form 8-K to provide information regarding its terms. It is not intended to provide any other factual information about CEG Parent, Constellation, Calpine or any other party. The Merger Agreement contains representations and warranties that the parties thereto made to each other as of a specific date. The assertions embodied in the representations and warranties in the Merger Agreement were made solely for purposes of the Merger Agreement and the transactions and agreements contemplated thereby among the respective parties thereto and may be subject to important qualifications and limitations agreed to by the parties thereto in connection with negotiating the terms thereof and are not intended to, and do not, confer upon any person other than the parties thereto any rights or remedies thereunder, including the right to rely upon the representations and warranties set forth therein. Moreover, some of those representations and warranties may not be accurate or complete as of any specified date, may be subject to a contractual standard of materiality different from those generally applicable to stockholders or may have been used for the purpose of allocating risk among the parties to the Merger Agreement rather than establishing matters as facts. Section 2 - Financial Information

Item 2.03. Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant The disclosure set forth in Item 1.01 under the heading “Calpine Notes” is incorporated by reference in this Item 2.03. Section 3 - Securities and Trading Markets

Item 3.02. Unregistered Sales of Equity Securities The disclosure set forth in Item 2.01 above is incorporated by reference in this Item 3.02. The issuance of the Stock Consideration to the former stockholders of Calpine was made in reliance upon the exemption from the registration requirements of the Securities Act of 1933, as amended, provided by Section 4(a)(2) thereof as a transaction by an issuer not involving any public offering. Section 5 - Corporate Governance and Management

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers Effective upon the closing of the Mergers on January 7, 2026, Daniel Eggers, CEG Parent’s Executive Vice President and Chief Financial Officer, was promoted to Senior Executive Vice President, Finance and Data Economy, and no longer serves as Chief Financial Officer, and Shane Smith, CEG Parent’s Senior Vice President, Treasury and Credit, was promoted to Executive Vice President and Chief Financial Officer. Concurrently with the effectiveness of Mr. Smith’s promotion, Mr. Smith also assumed the additional role of principal financial officer of CEG Parent, replacing Mr. Eggers. As previously reported, Mr. Smith’s compensation includes an annual base salary of $725,000, an annual incentive program target opportunity of 85% of his base salary, and a long-term incentive target valued at $2,500,000, consistent with the terms of the Constellation Energy Corporation 2022 Long-Term Incentive Plan. Mr. Smith, age 46, had served as CEG Parent’s Senior Vice President, Treasury and Credit since CEG Parent’s separation from Exelon in February 2022, prior to which Mr. Smith served as Vice President, Finance, Constellation for Exelon beginning in April 2020. Mr. Smith received his bachelor’s degree with a dual concentration in Finance and Marketing from Boston College and his MBA from the University of Maryland. There are no arrangements or understandings between Mr. Smith and any other person pursuant to which Mr. Smith was appointed as Executive Vice President and Chief Financial Officer, and there are no family relationships among any of CEG Parent’s directors or executive officers and Mr. Smith. Mr. Smith does not have any direct or indirect material interest in any transaction or proposed transaction required to be reported under Item 404(a) of Regulation S-K. Section 7 - Regulation FD

Item 7.01. Regulation FD Disclosure On January 7, 2026, CEG Parent issued a press release announcing the completion of the Mergers. The press release is attached to this Current Report on Form 8-K as Exhibit 99.1, is incorporated herein by reference and is being furnished to, but not filed with, the SEC. Section 9 - Financial Statements and Exhibits