Q1 2026 Quarterly Report (25th Fiscal Year) — Doosan Tesna

Summary

Doosan Tesna filed its Q1 2026 quarterly report covering January 1 to March 31, 2026, for its 25th fiscal year. The company, a semiconductor testing and engineering services provider, is now co-led by CEOs Yoon-Gun Kim and Hoon Cho following the appointment of Hoon Cho as CEO and Ji-Kwang Choi as outside director at the March 31, 2026 AGM, while former CEO Do-Won Kim stepped down. The board now consists of 2 CEOs and 4 outside directors. The largest shareholder remains Doosan Portfolio Holdings with 7,476,953 common shares following prior convertible preferred stock and BW conversions. The report also reflects the February 28, 2025 absorption merger of Engion Co., Ltd.

Historical Impact

2 past Quarterly Report · ≈ 10-Q events at Doosan Tesna

Median +5d

-9.02%

Range

-10.89% to -7.14%

Positive outcomes

0/2

Filed	P₀	P₊₅	+5d
Nov 14, 2025	₩44,100	₩40,950	-7.14%
May 15, 2025	₩25,250	₩22,500	-10.89%

Full Translation

Quarterly Report 6.5 Doosan Tesna 1 Y QUARTERLY REPORT (25th Fiscal Year) Fiscal Year: From January 1, 2026 to March 31, 2026 To: Financial Services Commission, Korea Exchange Date of Submission: May 15, 2026 Type of Submitting Entity: Listed Company Exemption Reason: Not Applicable Company Name: Doosan Tesna Co., Ltd. Representative Directors: Yoon-Gun Kim, Hoon Cho Head Office Location: 72, Sandan-ro 16beon-gil, Pyeongtaek-si, Gyeonggi-do (Mogok-dong) Phone: 031-646-8500 Website: http://www.doosan-tesna.com Responsible Author: (Position) Managing Director (Name) Hoon Cho Phone: 031-5179-4811 TABLE OF CONTENTS 【Confirmation by Representative Director, etc.】 I. Company Overview 1. Company Overview A. Status of Consolidated Subsidiaries (1) Status of Consolidated Subsidiaries (Unit: Companies) Listed/Unlisted: All categories show no consolidated subsidiaries (beginning, increase, decrease, ending all blank). "Not Applicable" (1)-1. Changes in Consolidated Companies: "Not Applicable" B. Legal and Commercial Name of the Company The company's name is 'Doosan Tesna Co., Ltd.', and in English, 'DOOSAN TESNA Inc.' C. Date of Establishment and Period of Subordination The company was established on September 6, 2002, as TESNA Inc., with the primary business purpose of semiconductor manufacturing-related testing and engineering services. On April 27, 2022, the trade name was changed to Doosan Tesna Co., Ltd. (DOOSAN TESNA Inc.). D. Head Office Address, Phone, Website - Head Office: 72, Sandan-ro 16beon-gil, Pyeongtaek-si, Gyeonggi-do - Phone: 031-646-8500 - Website: www.doosan-tesna.com E. SME Status - SME: Not Applicable - Venture Company: Not Applicable - Mid-sized Enterprise: Not Applicable F. Main Business and Future New Businesses (1) Business Purposes: The company operates in the semiconductor testing business. Its business purposes include: 1. Semiconductor manufacturing-related testing and engineering services 2. Semiconductor pilot production 3. Electronic component development, processing, assembly, and sales 4. Semiconductor product wholesale 5. Electric and electronic product manufacturing and sales 6. Real estate leasing 7. Leasing and service of electric, electronic, and semiconductor equipment 8. Used equipment trading 9. Smart card-related manufacturing 10. All work, business, and activities directly or indirectly related to or incidental to the above purposes (2) Future New Businesses: As of the report submission date, there are no new businesses planned beyond current operations. G. Credit Rating Matters: "Not Applicable" Listing Status: - KOSDAQ Listing Date: October 22, 2013 - Special Listing Type: Not Applicable 2. Company History A. Head Office Location and Changes Current head office: 72, Sandan-ro 16beon-gil, Pyeongtaek-si, Gyeonggi-do (Mogok-dong) - Incorporation (2002.09.06): 223-12 Sangdaewon-dong, Jungwon-gu, Seongnam-si, Gyeonggi-do - Relocation (2005.07.19): 253 Namjeong-ri, Sindun-myeon, Icheon-si, Gyeonggi-do - Relocation (2013.03.29): 72 Sandan-ro 16beon-gil, Pyeongtaek-si (Mogok-dong) B. Major Changes in Management and Auditors - 2022.03.29 (Regular AGM): Reappointed outside director Chun-Sik Hong - 2022.04.27 (Extraordinary GM): New CEO Yoon-Gun Kim; non-executive director Do-Won Kim; outside directors Hyun-Jae Kim, Jae-Hyung Jang, Seok-Ho Seo. Departing: inside director Ki-Moon Kim, auditor Ki-Hong Kim, outside director Chun-Sik Hong - 2022.09.16 (Extraordinary GM): New CEO Do-Won Kim. Departing: non-executive director Do-Won Kim, CEO Jong-Do Lee - 2025.03.26 (Regular AGM): Reappointed CEO Do-Won Kim, CEO Yoon-Gun Kim, outside directors Hyun-Jae Kim, Jae-Hyung Jang, Seok-Ho Seo - 2026.03.31 (Regular AGM): New CEO Hoon Cho, new outside director Ji-Kwang Choi. Departing: CEO Do-Won Kim As of the report submission date, the board consists of 2 CEOs (Yoon-Gun Kim, Hoon Cho) and 4 outside directors (Hyun-Jae Kim, Jae-Hyung Jang, Seok-Ho Seo, Ji-Kwang Choi). C. Changes in Largest Shareholder - On March 8, 2022, the former largest shareholder AITree LLC entered into a share transfer agreement to sell 2,909,292 common shares, 2,320,672 convertible preferred shares, and bonds with warrants (entitling subscription to 2,246,989 common shares) of the company to Doosan Co., Ltd. - On April 27, 2022, the transaction was completed with Doosan Investment Co., Ltd. (which received the buyer's position), changing the largest shareholder to Doosan Investment. - Doosan Investment renamed itself Doosan Portfolio Holdings on July 12, 2023. - On December 15, 2023, the largest shareholder exercised bond warrants, increasing common share holdings to 5,156,281 shares. - On December 2, 2024, 2,320,672 convertible preferred shares were converted to common shares at maturity. - As of the report submission date, the largest shareholder holds 7,476,953 common shares. D. Trade Name Change: On April 20, 2022, an Extraordinary GM resolved the share transfer agreement involving the largest shareholder change. Effective April 27, 2022 (transaction closing date), the company name was changed to Doosan Tesna Co., Ltd. (DOOSAN TESNA Inc. in English). E. Insolvency/Reorganization Proceedings: "Not Applicable" F. Merger Details: - 2025.02.28: Absorption merger of Engion Co., Ltd. G. Changes in Industry or Main Business: "Not Applicable" H. Other Significant Management Matters: "Not Applicable" I. Major Corporate History (selected): - 2002.09.06: Establishment of Tesna Co., Ltd. and designation as Ministry of Information and Communication-supported IT SoC testing company - 2004.05.28: 1st paid-in capital increase; ISO9001:2000 certification - 2004.06.01: Bonus issue - 2004.10.19: Venture company designation - 2005.05.29: 2nd paid-in capital increase - 2005.07.19: Line 1 plant established and HQ relocated (Icheon) - 2005.09.30: Corporate R&D center certification - 2007.07.28: 3rd paid-in capital increase - 2008.03.01: Line 2 plant expansion (Icheon) - 2008.08.15: INNO-BIZ, MAIN-BIZ acquired - 2009.12.15: Line 2 expansion (2nd floor) - 2010.02.28: Line 3 plant expansion (Anseong) - 2010.09.17: 4th paid-in capital increase - 2010.10.06: Bonus issue - 2011.02.17: Preferred-to-common share conversion - 2011.09.11: ISO/TS16949 certification - 2012.09.17: Line 4 plant expansion (Pyeongtaek) - 2012.10.26: CQM (Card Quality Management) certification - 2013.03.29: HQ relocation (Pyeongtaek) - 2018.03.27: ISO 14001:2015 certification - 2018.08.16: ISO 9001:2015 certification - 2020.10.07: Bonus issue - 2020.11.30: Line 5 plant expansion (Anseong) - 2022.04.27: Trade name change (Doosan Tesna Co., Ltd.) - 2023.12.15: Bond-with-warrant conversion to common shares - 2024.12.02: Preferred-to-common share conversion - 2025.02.28: Absorption merger of Engion Co., Ltd. 3. Capital Stock Changes [Translation truncated]