Boundless Bio, Inc.

Evaluation of Disclosure Controls and Procedures

We maintain disclosure controls and procedures that are designed to ensure that information required to be disclosed by us in the reports that we file or submit under the Exchange Act is recorded, processed, summarized, and reported within the time periods specified in the SEC’s rules and forms, and that such information is accumulated and communicated to our management, including our principal executive officer and principal financial officer, as appropriate, to allow timely decisions regarding required disclosure. In designing and evaluating the disclosure controls and procedures, management recognized that any controls and procedures, no matter how well designed and operated, can provide only reasonable and not absolute assurance of achieving the desired control objectives. In reaching a reasonable level of assurance, management necessarily was required to apply its judgment in evaluating the cost-benefit relationship of possible controls and procedures. In addition, the design of any system of controls also is based in part upon certain assumptions about the likelihood of future events, and there can be no assurance that any design will succeed in achieving its stated goals under all potential future conditions; over time, controls may become inadequate because of changes in conditions, or the degree of compliance with policies or procedures may deteriorate. Because of the inherent limitations in a cost-effective control system, misstatements due to error or fraud may occur and not be detected.

Management, with the participation of our principal executive officer and our principal financial officer, evaluated, as of the end of the period covered by this Annual Report on Form 10-K, the effectiveness of our disclosure controls and procedures (as such term is defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act). Based on this evaluation, our principal executive officer and our principal financial officer concluded that, as of such date, our disclosure controls and procedures were effective at the reasonable assurance level.

Management’s Annual Report on Internal Control over Financial Reporting

Management is responsible for establishing and maintaining adequate internal control over financial reporting (ICFR), as such term is defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act. ICFR cannot provide absolute assurance due to its inherent limitations; it is a process that involves human diligence and compliance and is subject to lapses in judgment and breakdowns resulting from human failures. ICFR also can be circumvented by collusion or improper management override. Because of such inherent limitations, ICFR may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with applicable policies or procedures may deteriorate. Our ICFR is designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with U.S. GAAP.

Management, with the participation of our principal executive officer and our principal financial officer, conducted an assessment of the effectiveness of our ICFR as of the end of the period covered by this Annual Report on Form 10-K using the criteria set forth in Internal Control—Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this assessment, management concluded that our ICFR was effective as of December 31, 2025 to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements in accordance with U.S. GAAP.

As an “emerging growth company” and a “non-accelerated filer,” we are not required to provide an auditor attestation report on our ICFR, and we did not engage our independent registered public accounting firm to perform an audit of our ICFR.

Changes in Internal Control over Financial Reporting

Management, with the participation of our principal executive officer and our principal financial officer, evaluated any changes in our ICFR that occurred during the quarter ended December 31, 2025, as required by Rules 13a-15(d) and 15d-15(d) under the Exchange Act. Management concluded that there was no change in our ICFR that occurred during the quarter ended December 31, 2025 that has materially affected, or is reasonably likely to materially affect, our ICFR.