Background and Business Description

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Background and Business Description

1.    BACKGROUND AND BUSINESS DESCRIPTION

Octave Specialty Group, Inc. (“OSG”), headquartered in New York City, is a financial services holding company incorporated in the state of Delaware on April 29, 1991. OSG is formerly known as Ambac Financial Group, Inc. ("AFG"). In the fourth quarter of 2025 AFG changed its name to OSG in connection with the sale of its legacy financial guarantee business to reflect the Company's position as a P&C only business. References to "Octave," "OSG," the “Company,” “we,” “our,” and “us” are to OSG and its subsidiaries, as the context requires. Octave operates two principal businesses:

•Insurance Distribution — Octave's specialty property and casualty ("P&C") insurance underwriting and distribution business, includes Managing General Agents and Underwriters (collectively "MGAs" or "MGA/Us"); an insurance broker; and other distribution, underwriting and related businesses. On October 31, 2025, the Company completed the acquisition of ArmadaCorp Capital, LLC and its subsidiaries (collectively, "ArmadaCorp"), a leading specialty accident and health MGA. Octave's insurance distribution platform operates in the following lines of business: property, niche specialty risk, accident & health, miscellaneous specialty, reinsurance, surety, marine & energy, specialty auto, E&S commercial package, professional lines and Directors & Officers ("D&O").

•Specialty Property & Casualty Insurance — Octave's Specialty Property & Casualty Insurance program insurer business currently includes five carriers (collectively, “Everspan”). Everspan carriers have an A.M. Best rating of 'A-' (Excellent) which was affirmed on July 17, 2025.

The Company reports these two business operations as segments; see Note 3. Segment Information for further information.

Octave's financial guarantee business, which is being reported as a discontinued operations due to its sale in 2025, includes the activities of Ambac Assurance Corporation ("AAC") and its wholly owned subsidiaries, including Ambac Assurance UK Limited (“Ambac UK”) and Ambac Financial Services LLC ("AFS"). See Note 5. Discontinued Operations for information related to the sale of AAC.

Limitations on Voting and Transfer of Common Stock

OSG’s Amended and Restated Certificate of Incorporation limits voting and transfer rights of stockholders in significant ways. Article IV contains voting restrictions applicable to any person owning at least 10% of OSG's common stock so that such person (including any group consisting of such person and any other person with whom such person or any affiliate or associate of such person has any agreement, contract, arrangement or understanding with respect to acquiring, voting, holding or disposing of OSG’s common stock) shall not be entitled to cast votes in excess of one vote less than 10% of the

votes entitled to be cast by all common stock holders, except as otherwise approved by the insurance commissioners of the states of domicile of the insurance companies controlled by OSG. Article XII contains substantial restrictions on the ability to transfer OSG’s common stock. In order to preserve certain tax benefits, subject to limited exceptions, any attempted transfer of common stock shall be prohibited and void to the extent that, as a result of such transfer (or any series of transfers of which such transfer is a part), either (i) any person or group of persons shall become a holder of 5% or more of OSG’s common stock or (ii) the percentage stock ownership interest in OSG of any holder of 5% or more of OSG’s common stock shall be increased (a “Prohibited Transfer”). These restrictions shall not apply to an attempted transfer if the transferor or the transferee obtains the written approval of OSG’s Board of Directors prior to such transfer. A purported transferee of a Prohibited Transfer shall not be recognized as a stockholder of OSG for any purpose whatsoever in respect of the securities which are the subject of the Prohibited Transfer (the “Excess Securities”). Until the Excess Securities are acquired by another person in a transfer that is not a Prohibited Transfer, the purported transferee of a Prohibited Transfer shall not be entitled with respect to such Excess Securities to any rights of stockholders of OSG, including, without limitation, the right to vote such Excess Securities and to receive dividends or distributions, whether liquidating or otherwise, in respect thereof, if any. Once the Excess Securities have been acquired in a transfer that is not a Prohibited Transfer, the securities shall cease to be Excess Securities. If the Board determines that a transfer of securities constitutes a Prohibited Transfer then, upon written demand by OSG, the purported transferee shall transfer or cause to be transferred any certificate or other evidence of ownership of the Excess Securities within the purported transferee’s possession or control, together with any distributions paid by OSG with respect to such Excess Securities, to an agent designated by OSG. Such agent shall thereafter sell such Excess Securities and the proceeds of such sale shall be distributed as set forth in the Amended and Restated Certificate of Incorporation. If the purported transferee of a Prohibited Transfer has resold the Excess Securities before receiving such demand, such person shall be deemed to have sold the Excess Securities for OSG’s agent and shall be required to transfer to such agent the proceeds of such sale, which shall be distributed as set forth in the Amended and Restated Certificate of Incorporation.