S-K 1603, SPAC Sponsor; Conflicts of Interest

Oct. 07, 2026

SPAC Sponsor, its Affiliates and Promoters [Line Items]

SPAC Sponsor and Affiliates Information, Restrictions on Sale of SPAC Securities [Table Text Block]

Pursuant to a letter agreement to be entered into with us, each of our sponsor, directors and officers has agreed to restrictions on its ability to transfer, assign, or sell the founder shares and private placement units, as summarized in the table below. In addition to the restrictions set forth below, up to 500,000 founder shares are subject to forfeiture to the extent the over-allotment option is not exercised; further, in the event of a transfer of sponsor membership interests by members of our sponsor or their affiliates, there will be an indirect transfer of the founder shares and private placement units held by our sponsor. While there are currently no circumstances or arrangements contemplated under which our

sponsor, its members or affiliates, or our directors or officers could indirectly transfer ownership of securities owned by our sponsor through transfers of sponsor membership interests, in certain limited circumstances such transfers are not prohibited. For more information, see “Principal Shareholders — Restrictions on Transfers of Founder Shares and Private Placement Units”.

Subject Securities		Expiration Date		Natural Persons and Entities Subject to Restrictions		Exceptions to Transfer Restrictions
Founder Shares		The earlier of (i) six months after the completion of our initial business combination; or (ii) subsequent to our initial business combination, (A) the date on which the last reported sale price of our Class A ordinary shares equals or exceeds $12.50 per share (as adjusted for share sub-divisions, share dividends, reorganizations, recapitalizations and other similar transactions) for any 20 trading days within any 30-trading day period after completion of our initial business combination, or (B) the date on which we complete a liquidation, merger, share exchange or other similar transaction that results in all of our shareholders having the right to exchange their ordinary shares for cash, securities or other property.		Harbour Island Acquisition Sponsor LLC		Transfers permitted (a) to our officers, directors or consultants, any affiliate or family member of any of our officers, directors or consultants, any members or partners of the sponsor or their affiliates and funds and accounts advised by such members or partners, any affiliates of the sponsor, or any employees of such affiliates, (b) in the case of an individual, as a gift to such person’s immediate family or to a trust, the beneficiary of which is a member of such person’s immediate family, an affiliate of such person or to a charitable organization; (c) in the case of an individual, by virtue of laws of descent and distribution upon death of such person; (d) in the case of an individual, pursuant to a qualified domestic relations order; (e) by private sales or transfers made in connection with any forward purchase agreement or similar arrangement, in connection with an extension of the completion window or in connection with the consummation of a business combination at prices no greater than the price at which the shares or warrants were originally purchased; (f) pro rata distributions from our sponsor to its respective members, partners or shareholders pursuant to our sponsor’s limited liability company agreement or other charter documents; (g) by virtue of the laws of the Cayman Islands or our sponsor’s limited liability company

Subject Securities	Expiration Date	Natural Persons and Entities Subject to Restrictions	Exceptions to Transfer Restrictions
			agreement upon the dissolution of our sponsor, (h) in the event of our liquidation prior to our consummation of our initial business combination; (i) in the event that, subsequent to our consummation of an initial business combination, we complete a liquidation, merger, share exchange or other similar transaction which results in all of our shareholders having the right to exchange their ordinary shares for cash, securities or other property or (j) to a nominee or custodian of a person or entity to whom a transfer would be permissible under clauses (a) through (g); provided, however, that in the case of clauses (a) through (g) and clause (j) these permitted transferees must enter into a written agreement agreeing to be bound by these transfer restrictions and the other restrictions contained in the letter agreements.
Private Placement Units (including underlying securities)	The completion of our initial business combination	Harbour Island Acquisition Sponsor LLC	Same as above.
Any units, warrants, ordinary shares or any other securities convertible into, or exercisable or exchangeable for, any units, ordinary shares, founder shares or warrants	180 days from the date of this prospectus	Harbour Island Acquisition Sponsor LLC Clear Street	We, our sponsor and our officers and directors have agreed that, for a period of 180 days from the date of this prospectus, we and they will not, without the prior written consent of the representatives of the underwriters, offer, sell, contract to sell, pledge or otherwise dispose of, directly or indirectly, any units, ordinary shares or any other securities convertible into, or exercisable, or exchangeable for, shares, subject to certain exceptions. The representatives in their sole

Subject Securities		Expiration Date		Natural Persons and Entities Subject to Restrictions		Exceptions to Transfer Restrictions
						discretion may release any of the securities subject to these lock-up agreements at any time without notice, other than in the case of the officers and directors, which shall be with notice. Our sponsor, officers and directors are also subject to separate transfer restrictions on their founder shares and private placement units pursuant to the letter agreement described in the immediately preceding paragraphs.

Fiduciary Duties to Other Companies, SPAC Officers and Directors [Table Text Block]

Below is a table summarizing the entities to which our officers and directors currently have fiduciary duties or contractual obligations:

Individual	Entity	Entity’s Business	Affiliation
McAndrew Rudisill	Harbour Island LLC	Investments	Managing Partner
	Pelagic Capital Advisors LLC	Investments	Managing Partner and Chief Investment Officer
	PCAO LLC	Investments	Managing Partner
	Forum Markets Inc.	Asset Ownership and Operation	Executive Chairman and Chief Executive Officer
Samuel J. Knipper	Change Agents Corporation	Agentic technology	Chief Financial Officer
	Brio Financial Group	Financial services	SEC Reporting Manager
Ryan Smith	Big Sky Industrial Inc. (f/k/a U.S. Energy Corp.)	Industrial Gases & Energy	Chief Executive Officer; Director
	Forum Markets Inc.	Asset Ownership and Operation	Director
	LCCA Holdings LLC	Consulting and private investments	Sole Member
Michael Edwards	Forum Markets Inc.	Asset Ownership and Operation	Director
	Third Way	Public policy think tank	Director
	Zippy, Inc.	Technology provider; manufactured home loans	Director
	Velocity Worldwide	Marketing technology	Director
	Manifest Ed	Learning platform	Director
	Old Post Company Inc.	Strategic advisory firm	Managing Principal
	Jones & Daughters LLC	Shopping	Partner
Benjamin Piggott	D Boral Acquisition Corp I	Blank check company	Co-President, Director
	Saquish Head Capital Partners LLC	Investments	General Partner
James Muchmore	XTI Aerospace, Inc.	Aerospace	General Counsel
	Black River Group, LLC	Investments	Sole Member
	Standard Domestic, LLC	Investments	Sole Member

SPAC Officers and Directors [Member]

spac [Line Items]

Conflict of Interest, Description [Text Block]

Our officers and directors are not required to, and will not, commit their full time to our affairs, which may result in a conflict of interest in allocating their time between our operations and our search for a business combination and their other businesses. We do not intend to have any full-time employees prior to the completion of our initial business combination. Each of our officers is engaged in several other business endeavors for which he may be entitled to substantial compensation, and our officers are not obligated to contribute any specific number of hours per week to our affairs.

Initial Shareholders [Member]

spac [Line Items]

Conflict of Interest, Description [Text Block]

Our sponsor and members of our management team will directly or indirectly own our securities following this offering, and accordingly, they may have a conflict of interest in determining whether a particular target business is an appropriate business with which to effectuate our initial business combination, including the fact that they may lose their entire investment in us, except to the extent they are entitled to redeem any public shares they acquire or receive distributions on the founder shares from assets outside the trust account, if our initial business combination is not completed, except to the extent they are entitled to redeem any public shares they acquire or receive liquidating distributions from assets outside the trust account or are entitled to receive liquidating distributions from the trust account in the event they choose to purchase public shares. Our initial shareholders purchased founder shares prior to the date of this prospectus and will purchase private placement units in a transaction that will close simultaneously with the closing of this offering. Upon the closing of this offering, assuming the underwriters’ over-allotment option is not exercised, our sponsor will have invested in us an aggregate of $3,125,000, comprised of the $25,000 purchase price for the founder shares (or approximately $0.007 per share) and the $3,100,000 purchase price for the private placement units (or $10.00 per unit). Accordingly, our management team may be more willing to pursue a business combination with a riskier or less-established target business than would be the case if our sponsor had paid the same per share price for the founder shares as our public shareholders paid for their public shares in this offering or if our sponsor were required to pay cash to exercise the private placement units, as oursponsor and members of our management team would likely not receive any financial benefit unless we consummated such business combination. These interests of our executive officers and directors may affect the consideration paid, terms, conditions and timing relating to a business combination in a way that conflicts with the interests of our public shareholders.

Our Sponsor [Member]

spac [Line Items]

Conflict of Interest, Description [Text Block]

In the event our sponsor or members of our management team provide loans to us to finance transaction costs and/or incur expenses on our behalf in connection with an initial business combination, such persons may have a conflict of interest in determining whether a particular target business is an appropriate business with which to effectuate our initial business combination as such loans may not be repaid and/or such expenses may not be reimbursed unless we consummate such business combination. Upon the consummation of our initial business combination, we will repay up to an aggregate of $300,000 in loans made to us by our sponsor to cover offering-related and organizational expenses. Additionally, up to $1,500,000 of working capital loans made to us by the sponsor may be convertible into private placement units of the post-business combination entity at a price of $10.00 per unit at the option of the lender, no earlier than 60 days after the closing of this offering. Such units would be identical to the private placement units. Except for the foregoing, the terms of such working capital loans, if any, have not been determined and no written agreements exist with respect to such loans.