Summit Midstream Corp

proxy statement with the Securities and Exchange Commission (the “SEC”) and also plans to file other relevant documents with the SEC regarding the proposed Transaction. COMMON STOCKHOLDERS AND OTHER INVESTORS ARE URGED TO READ THE PROXY STATEMENT (INCLUDING ALL AMENDMENTS AND SUPPLEMENTS THERETO) AND OTHER RELEVANT DOCUMENTS FILED WITH THE SEC IF AND WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION. You may obtain a free copy of the proxy statement (if and when it becomes available) and other relevant documents filed by the Company with the SEC at the SEC’s website at www.sec.gov. You may also obtain copies of the documents the Company files with the SEC on the Company’s website at www.summitmidstream.com. PARTICIPANTS IN THE SOLICITATION The Company and its directors, executive officers and other members of management and employees may, under the rules of the SEC, be deemed to be "participants" in the solicitation of proxies in connection with the proposed Transaction. Information about the Company’s directors and executive officers is available in the Company’s Registration Statement on Form S-4 (Registration No. 333-279903), as declared effective by the SEC on June 14, 2024 (the “Form S-4”). To the extent that holdings of the Company's securities have changed from the amounts reported in the Form S-4, such changes have been or will be reflected on Statements of Changes in Beneficial Ownership on Form 4 filed with the SEC. These documents may be obtained free of charge from the sources indicated above. Information regarding the participants in the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the proxy statement and other relevant materials relating to the proposed Transaction filed with the SEC. Common stockholders and other investors should read the proxy statement carefully before making any voting or investment decisions. CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS This Current Report on Form 8-K includes “forward-looking statements” within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act. All statements other than statements of historical facts included in this Current Report on Form 8-K, including, without limitation, statements about the Company’s and Tall Oak Parent’s respective ability to effect the proposed Transaction; the expected benefits of the proposed Transaction; the Company’s future financial performance following the proposed Transaction; future dividends or share buyback plans; and future plans, expectations, and objectives for the Company’s operations after completion of the proposed Transaction, including statements about strategy, future operations, financial position, estimated EBITDA and leverage, projected prospects, plans, and objectives of management, are forward- looking statements. In addition, forward-looking statements generally can be identified by the use of forward-looking terminology such as “may,” “will,” “could,” “expect,” “intend,” “project,” “estimate,” “anticipate,” “plan,” “believe,” “continue,” “seek,” “guidance,” “might,” “outlook,” “possibly,” “potential,” “prospect,” “should,” “would,” or similar terminology, but the absence of these words does not mean that a statement is not forward looking. While forward-looking statements are based on assumptions and analyses made by the Company that the Company believes to be reasonable under the circumstances, whether actual results and developments will meet expectations and predictions depend on a number of risks and uncertainties that could cause actual results, performance, and financial condition to differ materially from expectations. See “Risk Factors” in the Form S-4 for a discussion of risk factors that affect the Company’s business. Any forward-looking statement made in this Current Report on Form 8-K speaks only as of the date on which it is made. Factors or events that could cause actual results to differ may emerge from time to time, and it is not possible to predict all of them. Summit undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future developments, or otherwise, except as may be required by law. 4

SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Summit Midstream Corporation (Registrant) Dated: October 2, 2024 /s/ William J. Mault William J. Mault, Executive Vice President and Chief Financial Officer 5

Execution Version BUSINESS CONTRIBUTION AGREEMENT DATED OCTOBER 1, 2024, by and among SUMMIT MIDSTREAM CORPORATION, SUMMIT MIDSTREAM PARTNERS, LP and TALL OAK MIDSTREAM HOLDINGS, LLC ii TABLE OF CONTENTS Page Article I CERTAIN DEFINITIONS ....................................................................................2 1.1 Certain Defined Terms ............................................................................................ 2 Article II CONTRIBUTION AND ISSUANCE OF INTERESTS; CLOSING ..............26 2.1 Contribution and Issuance of Interests .................................................................. 26 2.2 Time and Place of Closing .................................................................................... 27 2.3 Estimated Adjustment Amount and Post-Closing Final Adjustment Amount ............................................................................................................................... 27 2.4 Conditions to Closing ........................................................................................... 30 2.5 Deliveries at the Closing ....................................................................................... 32 2.6 Tax Treatment ....................................................................................................... 36 2.7 Withholding .......................................................................................................... 38 2.8 Earnout .................................................................................................................. 39 Article III REPRESENTATIONS AND WARRANTIES WITH RESPECT TO TALL OAK PARENT .........................................................................................39 3.1 Organization, Good Standing, and Authority ....................................................... 39 3.2 Title to the Interests .............................................................................................. 40 3.3 No Conflicts; Consents and Approvals ................................................................. 40 3.4 Litigation ............................................................................................................... 41 3.5 Bankruptcy ............................................................................................................ 41 3.6 Investment Intent .................................................................................................. 41 3.7 Independent Evaluation ........................................................................................ 41 3.8 Business Investigation .......................................................................................... 42 Article IV REPRESENTATIONS AND WARRANTIES WITH RESPECT TO THE TARGET COMPANIES ............................................................................43 4.1 Organization, Good Standing, and Authority; Capitalization of the Target Companies............................................................................................................. 43 4.2 No Conflicts .......................................................................................................... 45 4.3 Consents and Authorizations ................................................................................ 45 4.4 Taxes ..................................................................................................................... 45 4.5 Compliance with Laws; Authorizations ................................................................ 47 4.6 Material Contracts ................................................................................................. 48 4.7 Intellectual Property; Cybersecurity Measures; Privacy....................................... 51 4.8 Broker’s or Finder’s Fees...................................................................................... 53 4.9 Employee Benefits ................................................................................................ 53 4.10 Employee Matters ................................................................................................. 55 4.11 Financial Statements; Absence of Undisclosed Liabilities ................................... 56 4.12 Environmental and Pipeline Safety Matters ......................................................... 57 4.13 Litigation ............................................................................................................... 58 iii 4.14 Property ................................................................................................................. 58 4.15 Insurance ............................................................................................................... 60 4.16 Absence of Certain Changes ................................................................................. 60 4.17 Title; Sufficiency and Condition of Assets; No