Harbour Island Acquisition Corp. I Sample Contracts

WARRANT AGREEMENT

Warrant Agreement • September 9th, 2026 • Harbour Island Acquisition Corp. I • Blank checks • New York

• Contract Type
  Warrant Agreement
• Filed
  September 9th, 2026
• Company
  Harbour Island Acquisition Corp. I
• Industry
  Blank checks
• Jurisdiction
  New York

THIS WARRANT AGREEMENT (this “Agreement”), dated as of [●], 2026, is by and between Harbour Island Acquisition Corp. I, a Cayman Islands exempted company (the “Company”), and Continental Stock Transfer & Trust Company, a New York corporation, as warrant agent (in such capacity, the “Warrant Agent,” and also referred to herein as the “Transfer Agent”).

HARBOUR ISLAND ACQUISITION CORP. I Palm Beach, FL 33480

Securities Subscription Agreement • September 9th, 2026 • Harbour Island Acquisition Corp. I • Blank checks • New York

• Contract Type
  Securities Subscription Agreement
• Filed
  September 9th, 2026
• Company
  Harbour Island Acquisition Corp. I
• Industry
  Blank checks
• Jurisdiction
  New York

Harbour Island Acquisition Corp. I, a Cayman Islands exempted company (the “Company”), is pleased to accept the offer Harbour Island Acquisition Sponsor LLC, a Delaware limited liability company, (the “Subscriber” or “you”) has made to subscribe for 5,750,000 Class B ordinary shares of the Company (the “Shares”), $0.0001 par value per share (the “Class B Ordinary Shares”), up to 750,000 of which are subject to complete or partial forfeiture by you if the underwriters of the Company’s initial public offering (“IPO”) of units (“Units”) do not fully exercise their over-allotment option (the “Over-allotment Option”). For the purposes of this Agreement, references to “Ordinary Shares” are to, collectively, the Class B Ordinary Shares and the Company’s Class A ordinary shares, $0.0001 par value per share (the “Class A Ordinary Shares”). Pursuant to the Company’s memorandum and articles of association (as may be amended, the “Articles”), Class B Ordinary Shares will convert into Class A Ordin

Harbour Island Acquisition Corp. I Palm Beach, FL 33480 Re: Initial Public Offering Ladies and Gentlemen:

Underwriting Agreement • September 9th, 2026 • Harbour Island Acquisition Corp. I • Blank checks

• Contract Type
  Underwriting Agreement
• Filed
  September 9th, 2026
• Company
  Harbour Island Acquisition Corp. I
• Industry
  Blank checks

This letter (this “Letter Agreement”) is being delivered to you in accordance with the Underwriting Agreement (the “Underwriting Agreement”) entered into by and among Harbour Island Acquisition Corp. I, a Cayman Islands exempted company (the “Company”) and Clear Street LLC, as representative (the “Representative”) of the underwriters (the “Underwriters”), relating to an underwritten initial public offering (the “Public Offering”), of up to 11,500,000 of the Company’s units (including up to 1,500,000 units which may be purchased to cover over-allotments, if any) (the “Units”), each comprised of one Class A ordinary share, par value $0.0001 per share, of the Company (the “Class A Ordinary Shares”) and one-half of one redeemable warrant (each whole warrant, a “Warrant”). Each Warrant entitles the holder thereof to purchase one Class A Ordinary Share at a price of $11.50 per whole share, subject to adjustment. The Units shall be sold in the Public Offering pursuant to the registration stat

INDEMNITY AGREEMENT

Indemnification Agreement • September 9th, 2026 • Harbour Island Acquisition Corp. I • Blank checks • New York

• Contract Type
  Indemnification Agreement
• Filed
  September 9th, 2026
• Company
  Harbour Island Acquisition Corp. I
• Industry
  Blank checks
• Jurisdiction
  New York

THIS INDEMNITY AGREEMENT (this “Agreement”) is made as of [●], 2026, by and between Harbour Island Acquisition Corp. I, a Cayman Islands exempted company (the “Company”), and the undersigned (“Indemnitee”).

HARBOUR ISLAND ACQUISITION CORP. I

Administrative Services Agreement • September 9th, 2026 • Harbour Island Acquisition Corp. I • Blank checks

• Contract Type
  Administrative Services Agreement
• Filed
  September 9th, 2026
• Company
  Harbour Island Acquisition Corp. I
• Industry
  Blank checks

PRIVATE PLACEMENT UNITS PURCHASE AGREEMENT

Private Placement Units Purchase Agreement • September 9th, 2026 • Harbour Island Acquisition Corp. I • Blank checks • New York

• Contract Type
  Private Placement Units Purchase Agreement
• Filed
  September 9th, 2026
• Company
  Harbour Island Acquisition Corp. I
• Industry
  Blank checks
• Jurisdiction
  New York

THIS PRIVATE PLACEMENT UNITS PURCHASE AGREEMENT, effective as of [●], 2026 (as it may from time to time be amended, this “Agreement”), is entered into by and between Harbour Island Acquisition Corp. I, a Cayman Islands exempted company (the “Company”), and Harbour Island Acquisition Sponsor LLC, a Delaware limited liability company (the “Purchaser”).

REGISTRATION RIGHTS AGREEMENT

Registration Rights Agreement • September 9th, 2026 • Harbour Island Acquisition Corp. I • Blank checks • New York

• Contract Type
  Registration Rights Agreement
• Filed
  September 9th, 2026
• Company
  Harbour Island Acquisition Corp. I
• Industry
  Blank checks
• Jurisdiction
  New York

THIS REGISTRATION RIGHTS AGREEMENT (this “Agreement”), dated as of [●], 2026 is made and entered into by and among Harbour Island Acquisition Corp. I, a Cayman Islands exempted company (the “Company”), Harbour Island Acquisition Sponsor LLC, a Delaware limited liability company (the “Sponsor”), Clear Street LLC, as the representative of the underwriters (the “Representative”), and the undersigned parties listed under Holder on the signature pages hereto (each such party, and any person or entity who hereafter becomes a party to this Agreement pursuant to Section 5.2 of this Agreement, a “Holder” and collectively the “Holders”).