(apologies for cross-posting)

Dear colleague,

We invite you to participate in the 2026 edition of the CheckThat! Lab at CLEF 2026. This year, we feature three tasks ---two follow-up and one new--- that correspond to important components within and around the full fact-checking pipeline in multiple languages:

Task 1 Source Retrieval for Scientific Web Claims: Given a social media post that contains a scientific claim and an implicit reference to a scientific paper (mentions it without a URL), retrieve the mentioned paper from a pool of candidate papers. Available in English, German, and French.

Task 2 Fact-Checking Numerical Claims:Given claims, potential evidences, and possible reasoning paths, rank the reasoning paths and provide an output of verdict. Available in Arabic, English, and Spanish.

Task 3 Generating Full Fact-Checking Articles:Given a claim, its veracity, and a set of evidence documents consulted for fact-checking the claim, generate a full fact-checking article.

Register and participate:https://clef-labs-registration.dipintra.it/ https://clef-labs-registration.dipintra.it/

Further information:https://checkthat.gitlab.io/ https://checkthat.gitlab.io/

Datasets:https://gitlab.com/checkthat_lab/clef2026-checkthat-lab https://gitlab.com/checkthat_lab/clef2026-checkthat-lab

Discord Server: https://discord.gg/PEMh4a2YHV https://discord.gg/PEMh4a2YHV

Important Dates

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- November 2025: Lab registration opens

- December 2025: Release of the sample materials

- December - February 2026: Release of training materials

- 23 April 2026: Lab registration closes

- April 2026: Beginning of the evaluation cycle (test sets release)

- 7 May 2026 (23:59 AOE): End of the evaluation cycle (run submission)

- 28 May 2026: Deadline for the submission of working notes [CEUR-WS]

- 30 June 2026: Notification of Acceptance for working notes [CEUR-WS]

- 6 July 2026: Camera Ready Copy of working note papers [CEUR-WS]

- 10 July 2026: Regular Registration Ends

- 31 August 2026: Late Registration Ends

- 21-24 September 2026: CLEF 2026 Conference in Jena, Germany

Best regards,

The CLEF-2026 CheckThat! Lab Shared Task Organizers