X0508 4/A 2025-09-29 2025-10-01 0 0000874501 OCTAVE SPECIALTY GROUP INC OSG 0001480597 Trick David C/O OCTAVE SPECIALTY GROUP, INC. 40 WALL STREET, 55TH FLOOR NEW YORK NY 10005 0 1 0 0 Exec VP, CFO & Treasurer 0 Common Stock 2025-09-29 4 C 0 165361 0 A 321443 D Common Stock 2025-09-29 4 F 0 80531 9.72 D 240912 D Common Stock 2025-09-30 4 M 0 42515 0 A 283427 D Common Stock 2025-09-30 4 F 0 22796 8.34 D 260631 D Deferred Share Units 2025-09-29 4 C 0 165361 0 D Common Stock 165361 0 D Deferred Share Units 2025-09-30 4 A 0 46300 0 A Common Stock 46300 46300 D Upon the closing of the sale of Ambac Assurance Corporation by Ambac Financial Group to an entity owned by funds managed by Oaktree Capital Management, L.P., a change of control was triggered causing the Reporting Person's Deferred Share Units ("DSUs") to vest and settle. Represents the corrected amount of DSUs that were converted into shares of common stock and withheld by the Company to satisfy certain tax withholding obligations. On September 30, 2025 the Compensation Committee of the Board of Directors of Ambac Financial Group approved the acceleration of the Reporting Person's 2023 and 2024 Performance Stock Unit awards in connection with the change of control referred to in footnote 1. The reporting person acquired shares of common stock of Ambac Financial Group, Inc. (the "Company") upon the simultaneous vesting and settlement of the reporting person's 2023 and 2024 Long Term Incentive Plan PSU awards. Represents the corrected aggregate amount of PSUs that were converted into shares of common stock and withheld by the Company to satisfy certain tax withholding obligations. Each DSU represents a contingent right to receive one share of common stock of the Company. Represents the aggregate amount of performance stock units ("PSUs") that were converted into an equivalent number of DSUs pursuant to the Company's Executive Stock Deferral Plan, which was designed to enable participants to elect to defer the settlement and income taxation of PSU and restricted stock unit awards in accordance with Section 409A of the Internal Revenue Code of 1986, as amended. This amended Form 4 was filed to correct an error in the calculation of the number of shares withheld by the Company to satisfy certain tax withholding obligations. William White, attorney-in-fact 2025-10-01