Capstone Copper Corp. (“Capstone” or the “Company”) (TSX:CS) (ASX:CSC) announced today that Union #2, one of the four unions at the Mantoverde Mine in Chile, representing approximately 50% of Mantoverde employees, or 22% of the total workforce, will take strike action effective January 2, 2026. Prior to the strike notice, Capstone attempted, in good faith, to reach an agreement for a new collective bargaining agreement with Union #2. As a result of the strike, certain activities at the mine will be gradually reduced in a safe manner. During the strike, Capstone expects to continue operations at Mantoverde at a level of up to 30% of normal production.

Capstone Copper remains willing to participate in meetings to reach a resolution, and will continue to adhere to legal procedures, respecting the rights of all its employees, inviting the union to engage in a constructive dialogue, and providing the authorities with all requested information. Capstone Copper is committed to the highest standards for integrity and transparency and looks forward to returning its focus to safe and responsible mining at Mantoverde, which brings great benefits to the workforce and surrounding communities.

During 2025, Mantoverde was able to successfully negotiate new three-year collective bargaining agreements with the three other unions.

In 2024, Capstone Copper distributed $682 million in economic value to Chile across its operations, including $136 million in employee wages and benefits. Today, Mantoverde employs approximately 1,270 total employees, including approximately 550 individuals from the local communities in the Atacama region of Chile. The total workforce at Mantoverde is approximately 2,940 individuals, including approximately 1,670 contractors.

About Capstone Copper Corp.

Capstone Copper Corp. is an Americas-focused copper mining company headquartered in Vancouver, Canada. Capstone’s operating portfolio of assets includes the Pinto Valley copper mine located in Arizona, USA, the Cozamin copper-silver mine located in Zacatecas, Mexico, the Mantos Blancos copper-silver mine located in the Antofagasta region, Chile, and the Mantoverde copper-gold mine, located in the Atacama region, Chile. Capstone’s growth pipeline includes the fully permitted Santo Domingo copper-iron-gold project, located approximately 35 kilometres northeast of Mantoverde in the Atacama region, Chile, as well as a portfolio of exploration properties in the Americas.

Capstone Copper’s strategy is to unlock transformational copper production growth while executing on cost and operational improvements through innovation, optimization and safe and responsible production throughout our portfolio of assets. We focus on profitability and disciplined capital allocation to surface stakeholder value. We are committed to creating a positive impact in the lives of our people and local communities, while delivering compelling returns to investors by responsibly producing copper to meet the world’s growing needs.

Further information is available at www.capstonecopper.com

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This document may contain “forward-looking information” within the meaning of Canadian securities legislation and “forward-looking statements” within the meaning of the United States Private Securities Litigation Reform Act of 1995 (collectively, “forward-looking statements”). These forward-looking statements are made as of the date of this document and the Company does not intend, and does not assume any obligation, to update these forward-looking statements, except as required under applicable securities legislation. In certain cases, forward-looking statements can be identified by the use of words such as “anticipates”, “approximately”, “believes”, “budget”, “estimates”, expects”, “forecasts”, “guidance”, intends”, “plans”, “scheduled”, “target”, or variations of such words and phrases, or statements that certain actions, events or results “be achieved”, “could”, “may”, “might”, “occur”, “should”, “will be taken” or “would” or the negative of these terms or comparable terminology. In this document certain forward-looking statements are identified by words including “anticipated”, “expected”, “guidance” and “plan”. Forward-looking statements include, but are not limited to, statements with respect to the Company’s expectations regarding operations during the strike and its approach to resolution and procedures regarding the strike.

By their very nature, forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause the Company's actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements. Such factors include, amongst others, risks related to the inability to resolve the labour disruption, the inability to operate at expected capacity during the strike, inherent hazards associated with mining operations and closure of mining projects, future prices of copper and other metals, compliance with financial covenants, inflation, surety bonding, the Company's ability to raise capital, Capstone Copper’s ability to acquire properties for growth, counterparty risks associated with sales of the Company's metals, use of financial derivative instruments and associated counterparty risks, foreign currency exchange rate fluctuations, market access restrictions or tariffs, changes in U.S. laws and policies regulating international trade including but not limited to changes to or implementation of tariffs, trade restrictions, or responsive measures of foreign and domestic governments, changes to cost and availability of goods and raw materials, along with supply, logistics and transportation constraints, changes in general economic conditions including market volatility due to uncertain trade policies and tariffs, availability and quality of water and power resources, accuracy of Mineral Resource and Mineral Reserve estimates, operating in foreign jurisdictions with risk of changes to governmental regulation, compliance with governmental regulations and stock exchange rules, compliance with environmental laws and regulations, reliance on approvals, licences and permits from governmental authorities and potential legal challenges to permit applications, contractual risks including but not limited to, the Company's ability to meet the requirements under the Cozamin Silver Stream Agreement with Wheaton Precious Metals Corp. ("Wheaton"), the Company's ability to meet certain closing conditions under the Santo Domingo Gold Stream Agreement with Wheaton, acting as Indemnitor for Minto Metals Corp.’s surety bond obligations, impact of climate change and changes to climatic conditions at the Company's operations and projects, changes in regulatory requirements and policy related to climate change and greenhouse gas ("GHG") emissions, land reclamation and mine closure obligations, introduction or increase in carbon or other "green" taxes, aboriginal title claims and rights to consultation and accommodation, risks relating to widespread epidemics or pandemic outbreaks; the impact of communicable disease outbreaks on the Company's workforce, risks related to construction activities at the Company's operations and development projects, suppliers and other essential resources and what effect those impacts, if they occur, would have on the Company's business, including the Company's ability to access goods and supplies, the ability to transport the Company's products and impacts on employee productivity, the risks in connection with the operations, cash flow and results of Capstone Copper relating to the unknown duration and impact of the epidemics or pandemics, impacts of inflation, geopolitical events and the effects of global supply chain disruptions, uncertainties and risks related to the potential development of the Santo Domingo development project, risks related to the Mantoverde Development Project ("MVDP"), increased operating and capital costs, increased cost of reclamation, challenges to title to the Company's mineral properties, increased taxes in jurisdictions the Company operates or is subject to tax, changes in tax regimes we are subject to and any changes in law or interpretation of law may be difficult to react to in an efficient manner, maintaining ongoing social licence to operate, seismicity and its effects on the Company's operations and communities in which we operate, dependence on key management personnel, Toronto Stock Exchange ("TSX") and Australian Securities Exchange ("ASX") listing compliance requirements, potential conflicts of interest involving the Company's directors and officers, corruption and bribery, limitations inherent in the Company's insurance coverage, labour relations generally, increasing input costs such as those related to sulphuric acid, electricity, fuel and supplies, increasing inflation rates, competition in the mining industry including but not limited to competition for skilled labour, risks associated with joint venture partners and non-controlling shareholders or associates, the Company's ability to integrate new acquisitions and new technology into the Company's operations, cybersecurity threats, legal proceedings, the volatility of the price of the common shares, the uncertainty of maintaining a liquid trading market for the common shares, risks related to dilution to existing shareholders if stock options or other convertible securities are exercised, the history of Capstone Copper with respect to not paying dividends and anticipation of not paying dividends in the foreseeable future and sales of common shares by existing shareholders can reduce trading prices, and other risks of the mining industry as well as those factors detailed from time to time in the Company’s interim and annual financial statements and MD&A of those statements and Annual Information Form, all of which are filed and available for review under the Company’s profile on SEDAR+ at www.sedarplus.ca. Forward-looking statements relate to future events or future performance and reflect the Company's expectations or beliefs regarding future events and are based on a number of assumptions, including those detailed from time to time in the Company’s interim and annual financial statements and MD&A of those statements and Annual Information Form, all of which are filed and available for review under the Company’s profile on SEDAR+ at www.sedarplus.ca. Although the Company has attempted to identify important factors that could cause the Company's actual results, performance or achievements to differ materially from those described in the Company's forward-looking statements, there may be other factors that cause the Company's results, performance or achievements not to be as anticipated, estimated or intended. There can be no assurance that the Company's forward-looking statements will prove to be accurate, as the Company's actual results, performance or achievements could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on the Company's forward-looking statements.

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