Contract analysis

1. Introduction and Purpose This Supplement to Engagement Letter (this "Supplement") is entered into by and between Calderwood & Harkness LLP ("Calderwood & Harkness" or the "Firm") and Halcyon Semiconductor Aktiengesellschaft, a stock corporation (Aktiengesellschaft) organized under the laws of the Federal Republic of Germany ("Halcyon" or the "Company"), with reference to the executed Engagement Letter dated Januar

2. Tax Advisory Team Lead Tax Advisor. The Tax Advisory Services described in this Supplement will be led by Leonard Cross, Specialist Partner in the Tax Practice Group of Calderwood & Harkness ("Mr. Cross"). Mr. Cross's current billing rate is $1,900 per hour, as set forth in the Engagement Letter. Mr. Cross brings extensive experience in international tax matters arising in the context of cross-border capital marke

3. Scope of Tax Advisory Services The Tax Advisory Services to be provided by Mr. Cross and the Firm's Tax Practice Group in connection with the Offering shall encompass the workstreams described in Sections 3.1 through 3.6 below. The scope described herein is intended to be comprehensive with respect to the anticipated US federal income tax issues arising in connection with the Offering; however, if additional US fe

4. Deliverables Mr. Cross will prepare and deliver the following work product in connection with the Tax Advisory Services described in this Supplement. All target delivery dates are subject to the overall transaction timeline and may be adjusted by mutual agreement of the parties in consultation with the Capital Markets team:

1. PFIC Analysis Memorandum (Internal). A detailed internal memorandum documenting the PFIC analysis and conclusions for FY2023, FY2024, and FY2025, together with supporting calculations, assumptions, and data sources. Target Delivery Date: Prior to circulation of the first draft of the Registration Statement on Form F-1 (March 9, 2026).

2. US/German Tax Treaty Memorandum (Internal). A detailed internal memorandum summarizing the analysis of the Treaty as applied to the Offering and the ownership of ADSs by US holders, including the LOB analysis, foreign tax credit analysis, and ADS structure considerations. Target Delivery Date: Prior to circulation of the first draft of the Registration Statement on Form F-1 (March 9, 2026).

3. Draft Prospectus Taxation Section (US Federal Income Tax Consequences). A draft of the "US Federal Income Tax Consequences" section of the prospectus, covering all topics described in Section 3.2 of this Supplement. This draft will be prepared for incorporation into the first draft of the Form F-1. Target Delivery Date: To be incorporated in the first draft of the Registration Statement on Form F-1 (March 9, 2026)

4. QI Analysis Memorandum (Internal). A memorandum documenting the analysis of Meridian Trust's QI status, withholding responsibilities, and operational recommendations. Target Delivery Date: By the all-parties drafting session (March 23–24, 2026).

5. Treaty Benefit Certification Procedures Memorandum (Internal). A memorandum describing the documentation and certification procedures applicable to US ADS holders claiming the reduced treaty withholding rate, including recommendations for prospectus disclosure. Target Delivery Date: By the all-parties drafting session (March 23–24, 2026).

6. Draft IRS Form W-8BEN-E for Halcyon Semiconductor AG. A completed or substantially completed draft of IRS Form W-8BEN-E for the Company, including entity classification, FATCA status, and LEI. Target Delivery Date: By the confidential submission date for the Registration Statement (April 14, 2026).

7. Final Tax Opinion for Filing with Registration Statement. The final Tax Opinion for filing as an exhibit to the Registration Statement on Form F-1, addressing the material US federal income tax consequences of the acquisition, ownership, and disposition of ADSs by US holders. Target Delivery Date: Prior to the SEC declaration of effectiveness of the Registration Statement (June 22, 2026). The foregoing deliverable

5. Limitations and Exclusions The Tax Advisory Services described in this Supplement are subject to the following limitations and exclusions: (a) Scope of Tax Law Coverage. The Tax Advisory Services are limited to US federal income tax law and the US-Germany income tax treaty (the Treaty). All advice on German domestic tax law, including German withholding tax procedures, German corporate tax, German trade tax (Gewer

6. Fee Arrangements All Tax Advisory Services provided pursuant to this Supplement will be billed on an hourly basis at the rates set forth in the Engagement Letter dated January 12, 2026. For the avoidance of doubt: (a) Leonard Cross Billing Rate. Mr. Cross's current billing rate is $1,900 per hour, as set forth in the Engagement Letter. Time spent by Mr. Cross on the Tax Advisory Services will be recorded and bille

7. Coordination with Other Advisors In connection with the Tax Advisory Services, Mr. Cross will coordinate directly with the following external advisors and Company personnel: (a) Bähr Stein Rechtsanwälte Partnerschaftsgesellschaft mbB. Dr. Christoph Maurelban, Partner, Capital Markets, and Johanna Weiß, Senior Associate, for German tax law matters and the German tax considerations portion of the prospectus. As desc

8. Governing Terms This Supplement is governed by and subject to all terms, conditions, and provisions of the Engagement Letter dated January 12, 2026, including, without limitation, the provisions relating to: (a) confidentiality and the protection of privileged communications; (b) conflicts of interest and the Firm's conflict clearance procedures; (c) limitation of liability; (d) dispute resolution, including any a

9. Counterparts and Acknowledgment This Supplement may be executed in one or more counterparts (including by means of electronic signatures transmitted by email or electronic signature platform), each of which shall be deemed an original and all of which, taken together, shall constitute one and the same instrument. We respectfully request that Mr. Ostermann, in his capacity as General Counsel (Chefjustitiar) of Halc