Summary of Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2026
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements and notes have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information and do not contain all of the information and footnotes required by U.S. GAAP for complete financial statements. As such, these unaudited condensed consolidated interim financial statements should be read in conjunction with the audited consolidated financial statements of Ategrity Specialty Insurance Company Holdings and its subsidiaries for the year ended December 31, 2025. The condensed consolidated balance sheet as of December 31, 2025 was derived from the Company’s audited annual consolidated financial statements. In the opinion of management, all adjustments necessary for a fair presentation of the condensed consolidated financial statements have been included. Such adjustments consist only of normal recurring items. All significant intercompany balances and transactions have been eliminated in consolidation. Interim results are not necessarily indicative of results of operations for the full year.
Principles of Consolidation	Principles of Consolidation The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its consolidated subsidiaries, as well as the Utility Limited Partnership, a variable interest entity (“VIE”) that meets the requirements for consolidation (see Note 3 for further details) (collectively referred to as the “Company”). All significant intercompany balances and transactions have been eliminated in consolidation.
Reclassifications and Statement of Cash Flows Presentation	Reclassifications and Statement of Cash Flows Presentation Certain prior period amounts have been reclassified to conform to the current period’s presentation. Beginning in the first quarter of 2026, the Company refined the presentation of certain investment-related cash flows within investing activities in the condensed consolidated statements of cash flows. Prior period amounts have been reclassified to conform to the current-period presentation. The reclassification had no impact on net cash provided by operating activities, net cash used in investing activities, net cash provided by financing activities, net change in cash and cash equivalents, net income, total assets, total liabilities or total stockholders’ equity.
Estimates and Assumptions	Estimates and Assumptions The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying disclosures. Management makes estimates and assumptions that include, but are not limited to, reserves for unpaid losses and loss adjustment expenses, fair value of financial assets and liabilities, allowance for credit losses, and income taxes. Those estimates are inherently subject to change, and actual results may ultimately differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements The Company currently qualifies as an “emerging growth company” under the Jumpstart Our Business Startups Act of 2012, or the JOBS Act. Accordingly, the Company is provided the option to adopt new or revised accounting guidance either: (i) within the same periods as those otherwise applicable to non-emerging growth companies; or (ii) within the same time periods as private companies. Accounting Standard Updates Recently Adopted The Company has not adopted any new accounting standards during the three and six months ended June 30, 2026. Accounting Standard Updates Not Yet Adopted In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income -Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, requiring public entities to disclose additional information about specific expense categories in the notes to the financial statements on an interim and annual basis. The guidance is effective for annual reporting periods beginning after December 15, 2026, and for interim reporting periods within annual reporting periods beginning after December 15, 2027, with early adoption permitted. The Company is evaluating the effect of the guidance on its consolidated financial statements and disclosures. In September 2025, the FASB issued ASU 2025-06, Targeted Improvements to the Accounting for Internal-Use Software (Subtopic 350-40). The standard eliminates the previous stage-based model for capitalization, introduces a “probable-to-complete” threshold that defers capitalization if significant development uncertainty exists, and aligns disclosure requirements with those for software developed for external use, as described in ASC 360-10, Property, Plant and Equipment. The ASU also supersedes ASC 350-50, Website Development Costs, unifying all internally developed technology, whether labeled “software” or “website”, under a single framework. The guidance is effective for fiscal years beginning after December 15, 2027, and interim periods within those years, with early adoption permitted. The Company is currently assessing the potential impact of the guidance on its consolidated financial statements and disclosures.
Fair Value of Financial Instruments	Three levels of inputs are used to measure fair value of financial instruments: (1) Level 1: quoted price (unadjusted) in active markets for identical assets, (2) Level 2: inputs to the valuation methodology include quoted prices for similar assets and liabilities in active markets and inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the instrument and (3) Level 3: inputs to the valuation methodology are unobservable for the asset or liability. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants on the measurement date. To measure fair value, the Company obtains prices for its investment securities from independent pricing services and other observable market inputs through third-party service providers. When quoted market prices for identical securities in active markets are not available, the Company uses observable inputs such as quoted prices of similar securities and evaluated pricing. The values for all fixed-maturity securities (consisting of U.S. Treasury securities and corporate securities) and equity securities generally incorporate significant Level 2 inputs using the market approach and income approach valuation techniques. The Company did not have any instruments classified within Level 3 measured at fair value on a recurring basis as of June 30, 2026 and December 31, 2025. There have been no changes in the Company’s use of valuation techniques since commencement of operations. The Company reviews fair value prices obtained through third-party service providers for reasonableness and monitors changes in unrealized gains and losses. The Company has not historically adjusted security prices. The Company obtains an understanding of the methods, models and inputs used by the independent pricing services, and controls are in place to validate that prices provided represent fair values. The Company’s control process includes, but is not limited to, initial and ongoing evaluation of the methodologies used, a review of specific securities and an assessment for proper classification within the fair value hierarchy and obtaining and reviewing internal control reports for relevant third-party service providers involved in the pricing process.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2026

The accompanying unaudited condensed consolidated financial statements and notes have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information and do not contain all of the information and footnotes required by U.S. GAAP for complete financial statements. As such, these unaudited condensed consolidated interim financial statements should be read in conjunction with the audited consolidated financial statements of Ategrity Specialty Insurance Company Holdings and its subsidiaries for the year ended December 31, 2025. The condensed consolidated balance sheet as of December 31, 2025 was derived from the Company’s audited annual consolidated financial statements. In the opinion of management, all adjustments necessary for a fair presentation of the condensed consolidated financial statements have been included. Such adjustments consist only of normal recurring items. All significant intercompany balances and transactions have been eliminated in consolidation. Interim results are not necessarily indicative of results of operations for the full year.

Principles of Consolidation

The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its consolidated subsidiaries, as well as the Utility Limited Partnership, a variable interest entity (“VIE”) that meets the requirements for consolidation (see Note 3 for further details) (collectively referred to as the “Company”). All significant intercompany balances and transactions have been eliminated in consolidation.

Reclassifications and Statement of Cash Flows Presentation

Certain prior period amounts have been reclassified to conform to the current period’s presentation. Beginning in the first quarter of 2026, the Company refined the presentation of certain investment-related cash flows within investing activities in the condensed consolidated statements of cash flows. Prior period amounts have been reclassified to conform to the current-period presentation. The reclassification had no impact on net cash provided by operating activities, net cash used in investing activities, net cash provided by financing activities, net change in cash and cash equivalents, net income, total assets, total liabilities or total stockholders’ equity.

Estimates and Assumptions

The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying disclosures. Management makes estimates and assumptions that include, but are not limited to, reserves for unpaid losses and loss adjustment expenses, fair value of financial assets and liabilities, allowance for credit losses, and income taxes.

Those estimates are inherently subject to change, and actual results may ultimately differ from those estimates.

Recent Accounting Pronouncements

The Company currently qualifies as an “emerging growth company” under the Jumpstart Our Business Startups Act of 2012, or the JOBS Act. Accordingly, the Company is provided the option to adopt new or revised accounting guidance either: (i) within the same periods as those otherwise applicable to non-emerging growth companies; or (ii) within the same time periods as private companies.

Accounting Standard Updates Recently Adopted

The Company has not adopted any new accounting standards during the three and six months ended June 30, 2026.

Accounting Standard Updates Not Yet Adopted

In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income -Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, requiring public entities to disclose additional information about specific expense categories in the notes to the financial statements on an interim and annual basis. The guidance is effective for annual reporting periods beginning after December 15, 2026, and for interim reporting periods within annual reporting periods beginning after December 15, 2027, with early adoption permitted. The Company is evaluating the effect of the guidance on its consolidated financial statements and disclosures.

In September 2025, the FASB issued ASU 2025-06, Targeted Improvements to the Accounting for Internal-Use Software (Subtopic 350-40). The standard eliminates the previous stage-based model for capitalization, introduces a “probable-to-complete” threshold that defers capitalization if significant development uncertainty exists, and aligns disclosure requirements with those for software developed for external use, as described in

ASC 360-10, Property, Plant and Equipment. The ASU also supersedes ASC 350-50, Website Development Costs, unifying all internally developed technology, whether labeled “software” or “website”, under a single framework. The guidance is effective for fiscal years beginning after December 15, 2027, and interim periods within those years, with early adoption permitted. The Company is currently assessing the potential impact of the guidance on its consolidated financial statements and disclosures.

Fair Value of Financial Instruments

Three levels of inputs are used to measure fair value of financial instruments: (1) Level 1: quoted price (unadjusted) in active markets for identical assets, (2) Level 2: inputs to the valuation methodology include

quoted prices for similar assets and liabilities in active markets and inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the instrument and (3) Level 3: inputs to the valuation methodology are unobservable for the asset or liability.

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants on the measurement date.

To measure fair value, the Company obtains prices for its investment securities from independent pricing services and other observable market inputs through third-party service providers. When quoted market prices for identical securities in active markets are not available, the Company uses observable inputs such as quoted prices of similar securities and evaluated pricing. The values for all fixed-maturity securities (consisting of U.S. Treasury securities and corporate securities) and equity securities generally incorporate significant Level 2 inputs using the market approach and income approach valuation techniques. The Company did not have any instruments classified within Level 3 measured at fair value on a recurring basis as of June 30, 2026 and December 31, 2025. There have been no changes in the Company’s use of valuation techniques since commencement of operations.

The Company reviews fair value prices obtained through third-party service providers for reasonableness and monitors changes in unrealized gains and losses. The Company has not historically adjusted security prices. The Company obtains an understanding of the methods, models and inputs used by the independent pricing services, and controls are in place to validate that prices provided represent fair values. The Company’s control process includes, but is not limited to, initial and ongoing evaluation of the methodologies used, a review of specific securities and an assessment for proper classification within the fair value hierarchy and obtaining and reviewing internal control reports for relevant third-party service providers involved in the pricing process.