Mr. Keith Bodnarchuk reports

COSA ANNOUNCES SUMMER DRILL PLANS FOR THE DARBY JOINT VENTURE WITH DENISON MINES

Cosa Resources Corp. has discussed summer plans for the company's Darby project. Darby is a joint venture between Cosa and Denison Mines Corp., and is located 10 kilometres west of Cameco's Cigar Lake mine in the eastern Athabasca basin, Saskatchewan. Cosa is the operator of Darby and holds a 70-per-cent interest with Denison holding a 30-per-cent interest. Drilling at Darby is expected after completion of a significant drill program at the company's Murphy Lake North joint venture to follow-up uranium mineralization intersected in winter 2026.

Highlights

• Drilling planned at the Gamma trend to follow up structure, alteration and strongly anomalous uranium geochemistry intersected during the winter 2026 drill program;
• Drilling planned at the Bravo trend to follow up weak uranium mineralization proximal to structure and alteration intersected by historical drilling;
• Drilling at Darby expected following completion of the significant drill program at the company's Murphy Lake North joint venture.

Andy Carmichael, vice-president of exploration, commented: "Second only to the summer drilling planned to follow up the recent intersection of 5.0 metres averaging 0.55 per cent U3O8 at our Murphy Lake North joint venture, targets at Darby are among our most compelling. Uranium mineralization has been intersected by several drill holes at Darby, reflecting the prospective geology of the area between the Cigar Lake and McArthur River uranium mines. Our planned summer drilling will continue to test areas where uranium mineralization and highly prospective structure and alteration are in proximity, with a focus this season on the Bravo and Gamma trends."

Planned Darby drilling

Drilling at Darby is planned to comprise up to 2,000 metres at the Gamma and Bravo trends. Drilling at Gamma will follow up Cosa's winter 2026 drill program which intersected a broad zone of structure with significant unconformity offset, alteration and elevated to strongly anomalous uranium geochemistry on trend with historical uranium mineralization. Drilling at Bravo will follow up compelling historical results including structure, alteration and uranium mineralization.

Next steps

The company remains on schedule and expects to announce the commencement of drilling at the Murphy Lake North joint venture in the coming days. Drilling at Murphy Lake North is expected to take a minimum of two months to complete and will be followed by drilling at Darby.

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). Initial drilling results from winter 2026 significantly upgraded multiple trends. Summer drilling is expected to commence in late August and will include follow up of anomalous results from both winter 2026 and historical drilling.

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 January of 2025, the company entered a transformative strategic collaboration with Denison Mines (TSX: DML) (NYSE American: DNN) that 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.

The company's primary focus through the remainder of 2026 will be drilling at the Murphy Lake North and Darby projects in the eastern Athabasca basin. Drilling at Murphy Lake North will follow up uranium mineralization within an extensive zone of strong structure and hydrothermal alteration at the Cyclone trend. Drilling at Darby will follow up on intersections of anomalous geochemistry, structure and zones of hydrothermal alteration from both winter 2026 drilling and historical drilling. 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 numbers 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 handheld GPS 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 (SRC) in Saskatoon, Sask. (ISO/IEC 17025:2005 accredited), for U3O8 (triuranium octoxide) 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, which 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 press 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.