Cosa Reports Anomalous Radioactivity in Multiple Drill Holes at the Murphy Lake North Joint Venture with Denison Mines

Vancouver, April 13, 2026 - Cosa Resources Corp. (TSXV: COSA) (OTCQB: COSAF) (FSE: SSKU) ("Cosa" or the "Company") is pleased to report the intersection of anomalous radioactivity in multiple drill holes and completion of the winter 2026 drilling program at the Company's Murphy Lake North Project ("MLN" or the "Project"). MLN is a joint venture (the "Joint Venture") between Cosa and Denison Mines Corp. (TSX: DML) (NYSE American: DNN) ("Denison") and is located 3 kilometres east of IsoEnergy's Hurricane deposit in the eastern Athabasca Basin, Saskatchewan (Figure 1). Cosa is the operator and holds a 70% interest with Denison holding a 30% interest.

Highlights

• Radioactivity intersected in three drill holes

• Radioactivity remains open in multiple directions including for at least 600 metres along strike to the east and 600 metres to the west within the larger kilometre-scale Cyclone alteration zone

• Depth of the radioactivity is shallow at approximately 260 metres vertically from surface

• Cyclone trend structural corridor is over 100 metres wide and hosts significant alteration consistent with major eastern Athabasca uranium deposits

Keith Bodnarchuk, President and CEO, commented: "Intersecting radioactivity in multiple drill holes is a tremendous result for Cosa, emphasizing the potential size and scale of this mineralizing system. The radioactivity alone is significant, but when factoring in the open space, depth, strong alteration and structure, this suggests we may be on the cusp of even more exciting results. With strong support from Denison Mines, assays pending, a healthy treasury, and numerous follow up targets, 2026 is shaping up to be a transformational year for Cosa."

Andy Carmichael, Vice President of Exploration, commented: "Intersecting 5 metres of continuously anomalous radioactivity in the second round of drilling at Cyclone significantly upgrades the trend. Though warming conditions curtailed follow up, the additional holes resulted in additional radioactive intercepts separate from that of MLN26-013 and a deeper understanding of the trend's geology which will be invaluable during future drilling. With 600 metres of open strike length in either direction along a mineralized structural corridor, we're eager to resume drilling in summer 2026."

MLN Winter Drilling Approach

Winter drilling at MLN followed up structure and alteration intersected at the Cyclone trend in summer 2025 (Figure 2). Five drill holes totaling 2,015 metres were completed during the program with three drill holes intersecting anomalous radioactivity¹. The first drill hole of the program, MLN26-013, intersected the strongest radioactivity including a 5.0 metre interval of continuously anomalous radioactivity in the upper basement (see Cosa's news release dated March 24, 2026). Two holes were completed to directly follow up radioactivity in MLN26-013. Two additional holes were completed to define underlying geology ahead of summer drilling and follow up another radioactive intersection. All drill holes were completed on Section 3200E.

MLN Winter Drilling Results

Three of five drill holes intersected anomalous radioactivity (Table 1) in two discrete zones. Drilling also defined highly prospective geology with similarities to the Hurricane deposit and other unconformity related uranium deposits of the eastern Athabasca Basin (Figure 3).

Table 1 - Winter 2026 MLN Drilling Program Results

1. Radioactivity is total gamma from drill core measured with an RS-125 hand-held spectrometer
2. Measurements of total gamma on drill core are an indication of uranium content but may not correlate with chemical assays
3. Previously released

Radioactivity

Multiple intervals of anomalous radioactivity were intersected in two discrete zones (Table 1, Figure 3). All radioactive intersections are associated with faulting and broad zones of strong hydrothermal alteration in the sandstone and basement. All radioactive intersections remain open along strike to the east and west for at least 600 metres and some intersections remain open on section.

MLN26-013, the first hole of the winter program, intersected a significant zone of structure and alteration underlain by faulted graphitic gneiss hosting several intervals of anomalous radioactivity between 306.5 and 313.5 metres ranging from 400 to 13,900 cps.

Radioactivity in MLN26-013 was followed up to the north (MLN26-014) and south (MLN26-015). MLN26-014 intersected anomalous radioactivity in the upper basement within a 0.5 metre strongly altered interval. Elevated radioactivity was intersected in the lower sandstone by MLN26-015.

50 metres north of MLN26-013, MLN26-016 intersected a 1.0 metre interval of anomalous radioactivity immediately below the unconformity associated with a broad zone of strong alteration and structure.

Cyclone 3200E Geology

Drilling determined the Cyclone trend is underlain by a package of graphitic and non-graphitic pelitic gneisses and quartzite over 100 metres in width. The full width of the mineralized structural corridor is unknown as additional prospective graphitic rocks may lie north and south of current drilling.

Graphitic basement units host faulting and alteration. Basement faulting is best developed in the northernmost graphitic unit where MLN26-016 and -017 intersected metre- to decametre-scale fault zones, including a 35 metre interval that is enveloped by moderate to strong alteration (Figure 6). At the unconformity, the northern edge of this fault zone hosts radioactivity (MLN26-016) which remains open in several directions. 100 metres to the south, MLN26-013 and -014 intersected another graphitic fault zone which is enveloped by alteration and remains untested at the unconformity.

Significant zones of sandstone structure and alteration are present throughout, and sandstone alteration patterns are similar to the Hurricane deposit where widespread bleached zones and distal silicified zones envelop broad desilicified zones cored by clay alteration (Figure 3). MLN26-013, -014, and -016 all intersected decametre-scale zones of sandstone faulting and alteration overlying the northern graphitic fault zone (Figure 3). Zones of faulting and alteration in the upper to middle sandstones of MLN26-013 and -016 suggest additional potential north of existing drilling.

Multiple altered basement fault zones remain untested at the unconformity and down-dip.

Next Steps

The Company and its Joint Venture partner, Denison Mines, will be finalizing summer plans in the coming weeks. The drill remains on site for rapid startup when drilling resumes this summer. Assays for all winter drill holes remain outstanding.

About Murphy Lake North

MLN covers a portion of the Larocque Lake trend and is located 2.7 kilometres east of the Hurricane deposit (Figures 1 and 2). Hurricane is the world's highest-grade indicated uranium resource and was discovered and delineated for IsoEnergy Ltd. by current members of Cosa's team. The Larocque Lake trend also hosts the high-grade Larocque Lake Zone, Yelka Prospect, and Alligator Lake Zone. MLN contains the along-strike extension of basement geology underlying the Hurricane deposit (the Hurricane trend), as well as a parallel conductive trend to the south (the Cyclone trend). Cosa's winter 2026 drill program intersected several meters of basement hosted radioactivity within a broader zone of strong structure and alteration at the Cyclone trend. Following up these results is the primary objective for the remainder of 2026 at MLN.

1 - Cosa considers radioactivity anomalous when it (i) exceeds 350 cps measured with a Radiation Solutions RS-125 hand held spectrometer, (ii) is accompanied by structure and/or hydrothermal alteration consistent with Athabasca unconformity related uranium deposits, and (iii) spectrometric assay by RS-125 indicates uranium is the dominant source.

Figure 1 - Cosa's Eastern Athabasca Uranium Projects with Joint Venture Projects

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Figure 2 - MLN Project Overview

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Figure 3 - Cross Section Cyclone 3200E

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Figure 4 - MLN26-013 Mineralization

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Figure 5 - MLN26-016 Mineralization

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Figure 6 - MLN26-017 Altered Graphitic Basement Fault Zone

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Marketing Engagement

The Company has entered into a marketing services agreement (the "Agreement") effective April 15th, 2026 with Northern Venture Group ("NVG"). NVG has agreed to provide certain promotional services (the "Services") to the Company in accordance with TSXV Policy 3.4 - Investor Relations, Promotional and Market-Making Activities. NVG has been engaged for an initial 3-month period for a monthly fee of C$10,000 with no upfront payment. Upon completion of the initial 3-month term, the Company and NVG may agree to extend the Services on a month-to month basis for the same monthly fee. The payment described herein will come from the Company's general working capital account.

NVG and its principal, Richard Mills, are arm's length to the Company and, at the time of the Agreement, hold zero common shares and zero share purchase warrants of the Company. No securities or other share-based incentives of Cosa are being granted to NVG under the terms of the Agreement. NVG has committed to comply with all applicable securities laws and the policies of the TSXX Venture Exchange (the "TSXV") in providing the Services. The NVG Agreement remains subject to approval of the TSX Venture Exchange.

NVG is an independent commodities newsletter and research platform that provides investors with in-depth commentary, analysis, and opinion on resource companies and macro trends for informational purposes only. NVG is located in Prince George, British Columbia, Canada.

About Cosa Resources Corp.

Cosa Resources is a Canadian uranium exploration company operating in northern Saskatchewan. The portfolio comprises roughly 237,000 ha across multiple underexplored 100% 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 MLN project. in the eastern Athabasca Basin. Drilling at MLN will follow up the zones of newly identified anomalous radioactivity within an extensive zone of intense structure and hydrothermal alteration at the Cyclone trend.

Cosa's award-winning management team has a track 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 MLN were sourced from the Saskatchewan Mineral Assessment Database (SMAD). SMAD sources for MLN and adjacent projects include file numbers 64L05-0161, 64L05-0180, 74I-0060, 74I-0066, 74I-0067, 74I01-0114, 74I08-0056, 74I09-0053, 74I09-0057, 74I09-0061, 74I09-0064, 74I09-0066, 74I09-0071, 74I09-0077, 74I09-0079, 74I09-0087, 74I09-0088, 74I09-0090, 74I09-0091, 74I09-0092, 74I09-0098, MAW00510, MAW01939, MAW02327, MAW02599, and MAW02395. Data and reports related to the 2020 ground EM survey completed by Denison are not presently available via SMAD and 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. 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. Additionally, Cosa engaged a consultant to re-interpret historical geophysical surveys to validate selected previous interpretations.

All drill core is scanned with an RS-125 hand held spectrometer to check for radioactivity. Intervals of anomalous radioactivity are removed in 0.5 metre core lengths to an area of background radioactivity and average radioactivity for the 0.5 metre interval is measured. Cosa drill holes are also surveyed using an Imdex EZ Gamma (NOVAx) down hole probe to provide a continuous log of radioactivity at 0.1 metre intervals. Down hole probe results are compared to RS-125 results to verify the depth and strength of radioactive intervals and to assess for radioactivity though sections of lost core.

Qualified Person

The Company's disclosure of technical or scientific information in this press release has been reviewed and approved by Andy Carmichael, P.Geo., Vice President, Exploration for Cosa. Mr. Carmichael is a Qualified Person as defined under the terms of National Instrument 43-101. All radioactivity measurements reported herein are total gamma from an RS-125 hand-held spectrometer. Chemical assays are pending. As the orientation of mineralization is unknown, true widths are unknown and reported mineralized intervals represent core lengths. 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.

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

Cautionary Statements

This press release contains forward-looking information within the meaning of Canadian securities laws (collectively "forward-looking statements"). Forward-looking statements are typically identified by words such as: believe, expect, anticipate, intend, estimate, plans, postulate and similar expressions, or are those, which, by their nature, refer to future events. All statements that are not statements of historical fact are forward-looking statements. These forward-looking statements or information may relate to anticipated exploration, development and/or expansion activities, including exploration of the Company's current Projects; the collaboration with Denison, including the Joint Venture, and the anticipated benefits thereof; and the outlook regarding Cosa's business plans and objectives.

Such forward-looking information and statements are based on numerous assumptions, including among others, that the results of planned exploration activities are as anticipated, the cost of planned exploration activities are as anticipated, that general business and economic conditions will not change in a material adverse manner, that financing will be available if and when needed and on reasonable terms, that third party contractors, equipment and supplies and governmental and other approvals required to conduct Cosa's planned exploration activities will be available on reasonable terms and in a timely manner. Although the assumptions made by Cosa in providing forward-looking information or making forward-looking statements are considered reasonable by management at the time, there can be no assurance that such assumptions will prove to be accurate.

By their nature, forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements, or other future events, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Such factors and risks include, among others: Cosa may require additional financing from time to time in order to continue its operations which may not be available when needed or on acceptable terms and conditions acceptable; Cosa may not be able to maintain compliance with its contractual obligations with third parties; Cosa may not be able to maintain compliance with extensive government regulation applicable to its operations; domestic and foreign laws and regulations could adversely affect Cosa's business and results of operations; the stock markets have experienced volatility that often has been unrelated to the performance of companies and these fluctuations may adversely affect the price of Cosa's securities, regardless of its operating performance; the ongoing military conflict in Ukraine, and other risk factors set out in Cosa's public disclosure documents.

The forward-looking information contained in this news release represents the expectations of Cosa as of the date of this news release and, accordingly, is subject to change after such date. Readers should not place undue importance on forward-looking information and should not rely upon this information as of any other date. Cosa does not undertake any obligation to update these forward-looking statements in the event that management's beliefs, estimates or opinions, or other factors, should change.

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