Octave Specialty Group, Inc.

Item 1.01. Entry into a Material Definitive Agreement Membership Interest Purchase Agreement On September 29, 2025, Ambac Financial Group, Inc. (the “Company”) and its wholly owned subsidiary Cirrata VI, LLC (“Buyer”) entered into a Membership Interest Purchase Agreement (the “Acquisition Agreement”) with Sirius Re Holdings, Inc. (“Seller Parent”) and Sirius Acquisitions Holding Company (“Seller”) pursuant to which Buyer agreed to acquire all of the issued and outstanding limited liability company interests of ArmadaCorp Capital, LLC, a wholly owned subsidiary of Seller, and its respective subsidiaries (the “Acquired Companies”) (the “Acquisition”), for a purchase price of $250,000,000. The Company expects the transaction to close in the fourth quarter of 2025, subject to customary closing conditions. The Acquisition Agreement contains customary representations, warranties and covenants of the Company, Seller and Acquired Companies. The foregoing description of the Acquisition Agreement is not complete and is qualified in its entirety by reference to the full text of the Acquisition Agreement, which is filed as Exhibit 10.1 to this Current Report on Form 8-K and is incorporated herein by reference. Commitment Letter for Senior Secured Credit Facilities In connection with the Acquisition, on September 29, 2025, Buyer entered into a Commitment Letter with Truist Securities, Inc., as sole arranger, and Truist Bank, as administrative agent, pursuant to which Buyer received commitments, subject to certain conditions, to fund senior secured credit facilities in an aggregate principal amount of $120,000,000, consisting of a $100,000,000 term loan facility and a $20,000,000 revolving credit facility (collectively, the “Senior Secured Credit Facilities”). The Buyer expects to obtain the senior secured first lien term loan facility prior to or substantially concurrent with the closing of the Acquisition and intends to use the proceeds therefrom to (i) finance a portion of the purchase price payable for the Acquired Companies, (ii) pay related transaction fees and expenses and (iii) provide working capital for other general corporate purposes. However, there can be no assurance that the Buyer will obtain the Senior Secured Credit Facilities within the anticipated time frame, or at all. The Commitment Letter expires on the earlier of (a) February 2, 2026, (b) the date the Acquisition closes with or without the use of the Senior Secured Credit Facilities or (c) the termination of the Acquisition Agreement.

Item 7.01 Regulation FD Disclosure. On September 29, 2025, the Company issued a press release regarding the Acquisition Agreement and Commitment Letter. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. The information in this Item 7.01, including Exhibit 99.1, is being furnished pursuant to Item 7.01 of Form 8-K and shall not be deemed “filed” for purposes of Section 18 of the Exchange Act, or otherwise subject to liabilities of that section, nor shall it be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, unless specifically identified therein as being incorporated therein by reference.