S-K 1603, SPAC Sponsor; Conflicts of Interest

Aug. 21, 2026

spac [Line Items]

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

Pursuant to a letter agreement to be entered 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 warrants (and the underlying securities), as summarized in the table below.

Subject Securities		Expiration Date		Persons Subject to Restrictions		Exceptions to Transfer Restrictions
Founder Shares		Earlier to occur of (A) with respect to 50% of the founder shares, six months after the completion of our initial business combination and (B) with respect to the remaining founder shares, the earlier of: (i) one year after the completion of our initial business combination and (ii) subsequent to our initial business combination, (x) if the last sale price of our Class A ordinary shares equals or exceeds $12.00 per share (as adjusted for share sub-divisions, share dividends, reorganizations, recapitalizations and the like) for any 20 trading days within any 30-trading day period commencing at least 150 days after our initial business combination, or (y) the date on which we complete a liquidation, merger, share exchange, reorganization 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		Dune Acquisition Holdings III LLC Carter Glatt Michael Castaldy Jeron Smith Ben Coates ______		Transfers permitted (a) to the sponsor, underwriters in this offering, our officers, directors, advisors or consultants, any affiliate or family member of any of our officers, directors, advisors 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 the underwriters in this offering, 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 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

Subject Securities		Expiration Date		Persons Subject to Restrictions		Exceptions to Transfer Restrictions
						limited liability company agreement upon 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 Class A 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 (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 warrants and warrants that may be issued upon conversion of working capital loans (and underlying securities)		30 days after the completion of our initial business combination		Same as above, together with the underwriters		Same as above

Sponsor Officers and Directors Letter Agreement [Member]

spac [Line Items]

Conflict of Interest, Description [Text Block]

Our initial shareholders purchased founder shares prior to the date of this prospectus and will purchase private placement warrants in a transaction that will close simultaneously with the closing of this offering. Our sponsor, officers and directors have entered into a letter agreement with us, pursuant to which they have agreed to waive their redemption rights with respect to their founder shares and public shares in connection with the completion of our initial business combination. Additionally, our sponsor, officers and directors have agreed to waive their rights to liquidating distributions from the trust account with respect to their founder shares if we fail to complete our initial business combination within the prescribed time frame, although they will be entitled to liquidating distributions from assets outside the trust account. If we do not complete our initial business combination within the prescribed time frame, the private placement warrants will expire worthless. Furthermore, our sponsor, officers and directors have agreed not to transfer, assign or sell any of their founder shares and any Class A ordinary shares issuable upon conversion thereof until the earlier to occur of: (A) with respect to 50% of the founder shares, six months after the completion of our initial business combination, and (B) with respect to the remaining founder shares, the earlier of: (i) one year after the completion of our initial business combination and (ii) the date following the completion of our initial business combination 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. Notwithstanding the foregoing, if the closing price of our Class A ordinary shares equals or exceeds $12.00 per share (as adjusted for share sub-divisions, share capitalizations, reorganizations, recapitalizations and the like) for any 20 trading days within any 30-trading day period commencing at least 150 days after our initial business combination, the founder shares will be released from the lockup. The private placement warrants (including the Class A ordinary shares issuable upon exercise of the private placement warrants) will not be transferable until 30 days following the completion of our initial business combination. Because each of our officers and director nominees will own ordinary shares or warrants directly or indirectly, 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.