Mr. Keith Bodnarchuk of Cosa Resources reports

COSA ANNOUNCES COMMENCEMENT OF SUMMER DRILLING PROGRAM AT THE DARBY URANIUM JOINT VENTURE WITH DENISON MINES

Cosa Resources Corp. has commenced drilling at the company's Darby project. Darby is a joint venture between Cosa and Denison Mines Corp., and is located 10 kilometres (km) west of Cameco's Cigar Lake mine. Cosa is the project operator and holds a 70-per-cent interest, with Denison holding a 30-per-cent interest.

Highlights:

• Drilling at the Gamma trend to follow up structure, alteration and anomalous uranium geochemistry intersected during the winter 2026 drill program;
• Drilling at the Bravo trend to follow up weak uranium mineralization proximal to structure and alteration intersected by historical drilling and within a magnetic-low trend extending northeast to Cigar Lake;
• Summer drilling is fully financed and will comprise up to 2,500 metres.

Keith Bodnarchuk, president and chief executive officer, commented: "Having recently completed an encouraging and productive drilling program at Murphy Lake North, we are excited to be back drilling at the Darby joint venture with our partner and largest shareholder, Denison Mines. Viewed by Cosa as a discovery-ready project, Darby boasts an exceptional pipeline of high-upside drill targets in proximity to structure, alteration and historical uranium mineralization. With $16-million in the treasury, we are fully funded for the summer program and follow-up in 2027. While our core focus remains on advancing the Murphy Lake North and Darby joint ventures with Denison, we are finalizing plans for a 100-per-cent partner funded drilling program expected to commence at our Aurora project in the coming days."

Andy Carmichael, vice-president of exploration, commented: "In addition to intersecting basement-hosted uranium mineralization, winter drilling and reinterpretation of historical results at Darby further upgraded multiple trends, notably at Gamma and Bravo. The exceptional geochemical anomalism, numerous intersections of graphitic structure and significant untested strike length across virtually all major trends at Darby continues to make for an exciting drill season. At Gamma, drilling will further test a broad zone of structure and alteration defined during the winter program that is also on trend with multiple occurrences of historical mineralization. At Bravo, drilling will follow up prospective geology and uranium mineralization intersected by multiple historical drill holes that lie within a magnetic-low trend interpreted to extend to the Cigar Lake uranium mine area."

Darby summer drilling

Up to 2,500 metres of drilling is planned to test multiple targets at each of the Gamma and Bravo trends. At Gamma, drilling will build on positive results from the winter campaign where drill hole DB24-41 defined a 100-plus-metre-wide zone hosting graphitic basement faulting associated with 30-plus metres of unconformity relief, sandstone and basement alteration, and elevated to anomalous uranium geochemistry in the basal sandstone. Uranium mineralization has been intersected by multiple historical drill holes on the Gamma trend immediately north of the project. At Bravo, drilling will target the trend along strike of encouraging historical results, including graphitic structure, alteration and uranium mineralization associated with more than 25 metres of unconformity relief. The Bravo trend is interpreted to lie within a magnetic-low trend extending through the Cigar Lake uranium mine to the northeast.

About Darby

Located 10 kilometres west of the Cigar Lake mine, Darby contains multiple prospective conductive trends and several intersections of weak uranium mineralization. Historical drilling indicates that many of these trends are highly prospective for uranium deposits characteristic of the eastern Athabasca basin, yet most of the strike length has not been effectively evaluated. Work by Cosa in 2025 prioritized these trends and identified several historical drill holes with results that suggest proximity to uranium mineralization (see Cosa's news releases dated Oct. 14, 2025, and Jan. 21, 2026).

About Cosa Resources Corp.

Cosa Resources is a Canadian uranium exploration company operating in Northern Saskatchewan. The portfolio comprises roughly 237,000 hectares across multiple underexplored 100-per-cent-owned and Cosa-operated joint venture projects in the Athabasca basin region, the majority of which reside within or adjacent to established uranium corridors.

In 2025, the company entered a transformative strategic collaboration with Denison, which has secured access to several additional highly prospective eastern Athabasca uranium exploration projects. As Cosa's largest shareholder, Denison gains exposure to Cosa's potential for exploration success and its pipeline of uranium projects.

Cosa's award-winning management team has a record of success in Saskatchewan. In 2022, members of the Cosa team were awarded the AME Colin Spence Award for the discovery of the Hurricane uranium deposit. Cosa personnel led teams or had integral roles in the discovery of Denison's Gryphon deposit and held key roles in the founding of both NexGen and IsoEnergy.

Technical disclosure

Historical drilling and geophysical results for Darby were sourced from the Saskatchewan Mineral Assessment Database (SMAD). SMAD sources for Darby include file Nos. 74H14-0021, 74H14-0023, 74H15-0041, 74H15-0053, 74H15-0055, 74H15-0056, 74H15-0066, 74H15-0067, 74I02-0031, 74I02-0042, 74I02-0053, 74I02-0080, 74I02-0095 and MAW00516. Some confidential data and reports not presently available via SMAD were supplied to Cosa by Denison.

Verification of historical drilling results included confirming historical drill hole collar locations from air photos and ground checking selected collars with a hand-held GPS (Global Positioning System) unit. Basement and lower sandstone sections from most historical drill holes were relogged in 2024 and 2025 by Cosa. Verification of geochemical results for drill holes completed between 2008 and 2010 was facilitated by the reissuance of analytical certificates to Cosa by the Saskatchewan Research Council (SRC). Cosa thanks the SRC for its valued assistance in increasing confidence in the historical data set.

Verification of historical geophysical results included confirming the locations of geophysical survey grids from air photos, compiling survey data and interpretations, and evaluating whether interpreted geophysical results could be reasonably explained by historical and current drilling results.

Samples from Cosa's drilling were transported to SRC Geoanalytical Laboratories in Saskatoon, Sask. (ISO/IEC 17025:2005 accredited), for U3O8 assay and multielement analysis. Cosa inserts certified reference material (CRM) blanks and standards into the split core sample series as a QA/QC (quality assurance/quality control) measure. SRC conducts a QA/QC program that includes repeat analyses and insertion of CRM standards CAR218, BL4A and BL2A, as appropriate. SRC's CRM results are verified by Cosa staff.

Qualified person

The company's disclosure of technical or scientific information in this news release has been reviewed and approved by Andy Carmichael, PGeo, vice-president, exploration, for Cosa. Mr. Carmichael is a qualified person as defined under the terms of National Instrument 43-101. This news release refers to neighbouring properties in which the company has no interest. Mineralization on those neighbouring properties does not necessarily indicate mineralization on the company's properties.

We seek Safe Harbor.