Larger Context Window, Fewer Overcorrections: Optimizing Prompts and Batching for Minimal-Edit Grammatical Error Correction

Kateryna Karpo, Artem Chernodub


Abstract
Minimal-edit Grammatical Error Correction (GEC) is a challenging task for zero- and few-shot prompted Large Language Models (LLMs), which systematically overcorrect and degrade F0.5 by rewriting well-formed spans. While fine-tuning provides an effective solution, it imposes substantial infrastructure demands. We introduce a prompt-based approach that closes the gap to fine-tuned models through three advances in GEC prompting methodology. First, we introduce taxonomy-based instructions to enforce minimal-edit constraints with a comprehensive list of grammatical error rules, equipping the LLM with a bounded, metric-aligned scope of correctable edits, which benefits the strongest models while remaining model-dependent overall. Second, we show that batching multiple uncorrected sentences into a single input context acts as a targeted regularizer against overcorrection, systematically reducing the edit rate across diverse LLM families; we hypothesize this arises from attention dilution effect induced by the bounded capacity of self-attention scores. Finally, LLM-assisted Prompt Optimization refines these instructions. Powered by Gemini 3.1-Pro, our prompt achieves F0.5=78.32 on the BEA-2019 test set — establishing a new prompt-based SOTA while shrinking the gap to the fine-tuned single-model SOTA (Staruch et al., 2025) to a mere 0.38 points. Code, prompts, and outputs are publicly available.
Anthology ID:
2026.findings-emnlp.1049
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
22194–22222
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1049/
DOI:
10.18653/2026.findings-emnlp.1049
Bibkey:
Cite (ACL):
Kateryna Karpo and Artem Chernodub. 2026. Larger Context Window, Fewer Overcorrections: Optimizing Prompts and Batching for Minimal-Edit Grammatical Error Correction. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 22194–22222, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Larger Context Window, Fewer Overcorrections: Optimizing Prompts and Batching for Minimal-Edit Grammatical Error Correction (Karpo & Chernodub, Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.1049.pdf