Riot Platforms, Inc.

10b5-1 Arrangements

During the three months ended September 30, 2026, except as set forth below, none of our directors or officers (as defined in Rule 16a-1(f) under the Exchange Act) adopted, modified, or terminated any contract, instruction or written plan for the purchase or sale of our securities that was intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act or any “non-Rule 10b5-1 arrangement” as defined in Item 408(c) of Regulation S-K.

On August 17, 2026, Stephen Howell, the Company’s Chief Operating Officer, adopted a Rule 10b5-1 trading arrangement intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act. The trading arrangement provides for the sale of up to 887,942 shares of our common stock, which includes shares issuable upon the future vesting of equity awards (with the actual number of such shares to be sold reduced by shares withheld to satisfy tax withholding obligations), and will remain in effect until the earlier of February 1, 2028 and the date on which all transactions under the arrangement are completed.

Corsicana Lease

On October 28, 2026, Riot Corsicana entered into the Corsicana Lease with the Frontier AI Lab. The Corsicana Lease became effective and binding on November 4, 2026, upon satisfaction of its conditions to effectiveness, which consisted of approval by the Company’s Board of Directors and approval of the technical specifications for the premises by Riot Corsicana’s third-party consultants.

Under the Corsicana Lease, Riot Corsicana will lease land, powered pads and related infrastructure at the Company’s Corsicana Facility to the Frontier AI Lab for the development and operation of a data center. The premises are expected to provide 910 MW of critical IT load capacity. Riot Corsicana expects to construct and deliver this capacity in three phases comprising a total of 40 blocks, with each phase delivered on a block-by-block basis, as follows:

The initial term commences on the commencement date of the first block and expires on the last day of the calendar month in which the 15 th anniversary of the commencement date of Phase 3 occurs, and the Frontier AI Lab has two options to extend the term for five years each. The Frontier AI Lab will pay base rent of $130.0 per kilowatt of critical IT load capacity per month for each delivered block of capacity, escalating 3% annually. The Corsicana Lease is a triple net lease, and the Frontier AI Lab will also bear taxes, insurance, site expenses and the cost of electricity consumed at the premises. Riot Corsicana is responsible, at its own cost, for constructing and delivering the power and site infrastructure and for operating and maintaining the power infrastructure during the term. Riot Corsicana will also reimburse the Frontier AI Lab for certain costs of the data center modules of up to $4.0 million per MW of critical IT power actually achieved, subject to Riot Corsicana obtaining financing on market terms reasonably acceptable to it. If that financing is not available after Riot Corsicana uses commercially reasonable efforts to obtain it, Riot Corsicana will instead provide rent credits that amortize that amount, plus interest at 12% per year, over the remainder of the initial term.

If Riot Corsicana delivers capacity more than 60 days late, the Frontier AI Lab is entitled to escalating rent credits, capped at 270 days of base rent for the undelivered blocks in the applicable phase. If a phase is not delivered within 270 days after its target date, the Frontier AI Lab may terminate the Corsicana Lease as to that phase on 30 days’ notice, subject to Riot Corsicana’s right to cure during that notice period; this deadline is extended for force majeure (for up to 365 days) and for delays caused by the Frontier AI Lab. Without the Frontier AI Lab’s consent, Riot Corsicana may not curtail the Frontier AI Lab’s power load (other than as mandatorily ordered by the utility or grid operator) or enroll the premises in voluntary demand response programs. Without the Frontier AI Lab’s consent, Riot Corsicana may not transfer the land to or undergo a change of control (including at the Company level) that would result in control by, certain restricted parties; if it does, the Frontier AI Lab’s remedies include terminating the Lease or purchasing Riot Corsicana’s interest in the premises at 95% of fair market value. The Corsicana Lease contains customary events of default. Riot Corsicana’s right to terminate the Lease is limited to uncured payment defaults and bankruptcy events.

There is no material relationship between the Company or any of its affiliates and the Frontier AI Lab, other than in respect of a leasing relationship.

The foregoing description of the Corsicana Lease does not purport to be complete and is qualified in its entirety by reference to the full text of the Corsicana Lease. The Company intends to file the Corsicana Lease as an exhibit to its Annual Report on Form 10-K for the fiscal year ending December 31, 2026, with certain portions omitted in accordance with Item 601(b)(10)(iv) of Regulation S-K.