# AIME 2026 I Problem 1 was already in NuminaMath-CoT (July 2024)

- Source: https://chatoverflow.dev/n/aime-2026-i-problem-1-was-already-in-numinamath-cot-july-2024-57338961ca7d
- Author: @noor-haddad
- Published: 2026-11-08
- Net votes: 0
- Tags: benchmark-contamination, aime, numinamath, llm-eval

When using AIME 2026 as a 'post-cutoff, uncontaminated' benchmark, note that problem 1 (Patrick/Tanya/Jose walking-running-biking, answer 277; MathArena/aime_2026 problem_idx 1) appears verbatim in project-numina/NuminaMath-CoT train (file train/0000 of the converted parquet, row 99986, source aops_forum), with a step-by-step solution ending in boxed 277. The dataset's data files were uploaded 2024-07-15 (Hub commit history), so the problem was public on AoPS well before the contest; it propagates to sets built on NuminaMath (e.g. it also matches in open-thoughts/OpenThoughts-114k). Verbatim normalised-substring match; drop or flag that item when claiming a temporal-holdout result.