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EsoLang-Bench: Evaluating Genuine Reasoning in Large Language Models via Esoteric Programming Languages

arXiv cs.AI / 3/11/2026

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Key Points

  • EsoLang-Bench is a new benchmark designed to evaluate genuine reasoning capabilities of large language models using five esoteric programming languages that have minimal public code repositories and thus low risk of benchmark gaming.
  • The benchmark includes Brainfuck, Befunge-98, Whitespace, Unlambda, and Shakespeare languages, which share computational primitives with mainstream programming yet differ drastically in public availability and familiarity.
  • Evaluation of five state-of-the-art models across various prompting strategies revealed a sharp drop in performance from 85-95% on standard benchmarks to 0-11% accuracy on esoteric languages, with no success beyond the easiest tasks.
  • Techniques like few-shot learning and self-reflection did not improve results, indicating these methods leverage pre-existing training knowledge rather than fostering genuine new learning or reasoning.
  • EsoLang-Bench aims to simulate human language acquisition through documentation review, interpreter feedback, and iterative experimentation, providing a more robust test of transferable reasoning abilities unaffected by data contamination.

Computer Science > Artificial Intelligence

arXiv:2603.09678 (cs)
[Submitted on 10 Mar 2026]

Title:EsoLang-Bench: Evaluating Genuine Reasoning in Large Language Models via Esoteric Programming Languages

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Abstract:Large language models achieve near-ceiling performance on code generation benchmarks, yet these results increasingly reflect memorization rather than genuine reasoning. We introduce EsoLang-Bench, a benchmark using five esoteric programming languages (Brainfuck, Befunge-98, Whitespace, Unlambda, and Shakespeare) that lack benchmark gaming incentives due to their economic irrationality for pre-training. These languages require the same computational primitives as mainstream programming but have 1,000-100,000x fewer public repositories than Python (based on GitHub search counts). We evaluate five frontier models across five prompting strategies and find a dramatic capability gap: models achieving 85-95% on standard benchmarks score only 0-11% on equivalent esoteric tasks, with 0% accuracy beyond the Easy tier. Few-shot learning and self-reflection fail to improve performance, suggesting these techniques exploit training priors rather than enabling genuine learning. EsoLang-Bench provides the first benchmark designed to mimic human learning by acquiring new languages through documentation, interpreter feedback, and iterative experimentation, measuring transferable reasoning skills resistant to data contamination.
Comments:
Subjects: Artificial Intelligence (cs.AI); Machine Learning (cs.LG); Software Engineering (cs.SE)
Cite as: arXiv:2603.09678 [cs.AI]
  (or arXiv:2603.09678v1 [cs.AI] for this version)
  https://doi.org/10.48550/arXiv.2603.09678
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arXiv-issued DOI via DataCite

Submission history

From: Aman Sharma [view email]
[v1] Tue, 10 Mar 2026 13:47:15 UTC (89 KB)
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