Mr. Don Njegovan reports

OSISKO METALS FILES NI 43-101 TECHNICAL REPORT FOR THE GASPE COPPER PROJECT

Osisko Metals Inc. has filed on SEDAR+ of a technical report titled "NI 43-101 Technical Report on the Gaspe Copper Project with an Updated Mineral Resource Estimate for the Copper Mountain Deposit, Quebec, Canada," dated May 28, 2026 (with an effective date of Jan. 17, 2026), in accordance with National Instrument 43-101, Standards of Disclosure for Mineral Projects.

The technical report was prepared by PLR Resources Inc., G Mining Services Inc. and Synectiq Inc. and supports the disclosure contained in the news release of the company dated April 14, 2026, titled "Osisko Metals Announces Significant Increase in Mineral Resources at Gaspe Copper."

Pursuant to Subsection 4.2(5)(b) of NI 43-101, the company confirms that there are no material differences between the technical report and the April news release. The mineral resource estimates for all categories, including tonnages, grades (copper, molybdenum, silver and copper equivalent), contained metal, and all underlying technical parameters and assumptions, are identical in the technical report and the April news release. No reconciliation of differences is required.

Updated mineral resource estimate -- Copper Mountain deposit

The technical report presents the updated mineral resource estimate (MRE) for the Copper Mountain deposit at the Gaspe copper project, located on the Gaspe peninsula of eastern Quebec, adjacent to the municipality of Murdochville. The 2026 MRE was prepared by Pierre-Luc Richard, PGeo, of PLR, with contributions from Francois Le Moal, PEng, of G Mining for cut-off grade and pit shell optimization, and Christian Laroche, PEng, of Synectiq for metallurgical parameters. All three qualified persons are independent of the company within the meaning of Section 1.5 of NI 43-101.

The 2026 MRE, reported at a base-case cut-off grade of 0.16 per cent copper equivalent, is summarized in the table below.

The quantity and grade of reported inferred mineral resources are uncertain in nature and there has been insufficient drilling to define these inferred mineral resources as indicated mineral resources. However, it is reasonably expected that the majority of inferred mineral resources could be upgraded to indicated mineral resources with additional drilling. The qualified persons are not aware of any known environmental, permitting, legal, title-related, taxation, socio-political, financial or other relevant issues that could materially affect the 2026 MRE. CIM (Canadian Institute of Mining, Metallurgy and Petroleum) definitions and guidelines for mineral resource estimates have been followed. Resources are presented as undiluted and in situ for an open-pit scenario and are constrained within a conceptual pit shell developed using overall pit slopes of 48 degrees in bedrock and overburden. The 2026 MRE model is based on 2,793 drill holes and 208,043 samples, including 159,212 metres in 238 drill holes drilled by the company between 2022 and 2025. Contained copper includes sulphide copper only; soluble copper from surface oxidized zones was excluded. The pit optimization was performed using Geovia Whittle 2022 software. Grade model resource estimation was calculated using an ordinary kriging (OK) interpolation method in a subblocked model using blocks measuring 15 metres by 15 metres by 15 metres in size and subblocks down to one metre by one metre by one metre. The measured mineral resource, indicated mineral resource and inferred mineral resource categories are constrained to areas where drill spacing is less than 60 metres, 120 metres and 300 metres, respectively, and show reasonable geological and grade continuity.

Previous mineral resource estimates superseded

The 2026 MRE supersedes all previously filed mineral resource estimates for the Copper Mountain deposit, including the Q4 2024 mineral resource estimate (with an effective date of Nov. 4, 2024), the Q2 2024 mineral resource estimate (with an effective date of April 22, 2024) and the 2022 mineral resource estimate (with an effective date of April 12, 2022). These prior mineral resource estimates should no longer be relied upon.

Qualified persons and data verification

The scientific and technical information in this news release has been reviewed and approved by: (i) Pierre-Luc Richard, PGeo (OGQ No. 1119), of PLR, a qualified person (as defined by NI 43-101) who is independent of the company within the meaning of Section 1.5 of NI 43-101 and is responsible for chapters 1 to 12 and 14 to 27 of the technical report, including the mineral resource estimate; (ii) Francois Le Moal, PEng (OIQ No. 6012262), of G Mining, a qualified person (as defined by NI 43-101) who is independent of the company within the meaning of Section 1.5 of NI 43-101 and is responsible for the pit optimization and cut-off grade parameters; and (iii) Christian Laroche, PEng, of Synectiq, a qualified person (as defined by NI 43-101) who is independent of the company within the meaning of Section 1.5 of NI 43-101 and is responsible for the metallurgical parameters.

The qualified persons have verified the data underlying the mineral resource estimate, including sampling, analytical and test data. Data verification included validation of the drill hole database, review of sampling and assaying procedures, the quality assurance/quality control program, downhole survey methodologies, and site visits conducted in January, 2024, and August, 2025. The qualified persons are of the opinion that the database is of good overall quality and suitable for mineral resource estimation.

About the Gaspe copper project

The Gaspe copper project is located on the Gaspe peninsula in eastern Quebec, approximately 825 kilometres east of Montreal, adjacent to the municipality of Murdochville. The property comprises two mining concessions and 203 mining claims covering 11,407 hectares. All necessary support infrastructure for the potential reopening of the project is already in place, including paved highway access through Highway 198, port access at Sainte-Anne-des-Monts and a Hydro-Quebec electrical substation on the property.

About Osisko Metals Inc.

Osisko Metals is a Canadian exploration and development company creating value in the critical metals sector, with a focus on copper and zinc. The company acquired a 100-per-cent interest in the past-producing Gaspe copper mine from Glencore Canada Corp. in July, 2023. Gaspe Copper hosts the largest undeveloped copper resource in eastern North America, strategically located near existing infrastructure in the mining-friendly province of Quebec. In addition to the Gaspe copper project, the company is working with Appian Capital Advisory LLP through the Pine Point Mining Ltd. joint venture to advance the Pine Point project in the Northwest Territories. The company is listed on the Toronto Stock Exchange under the trading symbol OM and the OTCQX under the symbol OMZNE.

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