YoungDSMLKZ at SemEval-2026 Task 13: MIL-UniXcoder with Meta-Stacking and Handcrafted Features for AI-Generated Code Detection

Yeraly Gainulla, Agzam Shamsadinov


Abstract
We propose and validate a multi-view ensemble framework for 4-class AI-generated code detection (Human, AI, Hybrid, Adversarial) in realistic long-form repositories. Our system, Team YoungDSMLKZ, ranked 1st out of 50+ teams in SemEval-2026 Task 13 Subtask C with a macro F1 of 0.7855 (+5.2 over runner-up). The framework combines: (i) a Dynamic Multiple Instance Learning (MIL) pipeline over UniXcoder chunks for O(N)-scalable long-context detection, (ii) transformer-based meta-stacking (UniXcoder and ModernBERT), and (iii) an XGBoost classifier on 200+ handcrafted stylometric features. Evidence localization analysis shows that 62.4% of decisive AI-detection signals reside beyond the standard 512-token window, validating the MIL design.
Anthology ID:
2026.semeval-1.137
Volume:
Proceedings of the 20th International Workshop on Semantic Evaluation (2026)
Month:
July
Year:
2026
Address:
San Diego, California, USA
Editors:
Ekaterina Kochmar, Debanjan Ghosh, Kai North, Mamoru Komachi
Venues:
SemEval | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
994–999
Language:
URL:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.137/
DOI:
Bibkey:
Cite (ACL):
Yeraly Gainulla and Agzam Shamsadinov. 2026. YoungDSMLKZ at SemEval-2026 Task 13: MIL-UniXcoder with Meta-Stacking and Handcrafted Features for AI-Generated Code Detection. In Proceedings of the 20th International Workshop on Semantic Evaluation (2026), pages 994–999, San Diego, California, USA. Association for Computational Linguistics.
Cite (Informal):
YoungDSMLKZ at SemEval-2026 Task 13: MIL-UniXcoder with Meta-Stacking and Handcrafted Features for AI-Generated Code Detection (Gainulla & Shamsadinov, SemEval 2026)
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PDF:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.137.pdf
Supplementarymaterial:
 2026.semeval-1.137.SupplementaryMaterial.zip
Supplementarymaterial:
 2026.semeval-1.137.SupplementaryMaterial.zip