DialPO: Dialectical Prompt Optimisation

Gokulakrishnan B, Vijay Kumar Neeluru, Vinayak S Puranik


Abstract
Existing textual-gradient prompt optimisers rely on a single Large Language Model (LLM) to diagnose failures, propose edits, and judge the results, conflating critique and refinement into one model’s judgement. We introduce DialPO (Dialectical Prompt Optimisation), a multi-agent framework that replaces the single- model feedback loop with a structured de- bate: an Advocate defends what the prompt does well, a Critic attacks failures, cross- examination filters their arguments adversar- ially, a data-isolated Synthesis model drafts the revised prompt from surviving arguments alone, and a regression gate rejects edits that degrade batch accuracy. We provide a theo- retical framework identifying three precondi- tions under which multi-agent debate improves the feedback-reasoning bottleneck of textual- gradient methods, and show that DialPO in- stantiates them by construction. Across 12 benchmarks spanning classification, reasoning, summarisation, and question answering, Di- alPO achieves the highest scores across various Target models, winning or tying a majority of datasets in head-to-head comparisons against each baseline while using 8–18× fewer LLM calls than beam-search optimisers. Compo- nent ablations across five Target models reveal that DialPO’s advantage scales inversely with Target-model strength, clarifying when dialec- tical debate helps prompt optimisation.
Anthology ID:
2026.findings-emnlp.2017
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:
42922–42938
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2017/
DOI:
10.18653/2026.findings-emnlp.2017
Bibkey:
Cite (ACL):
Gokulakrishnan B, Vijay Kumar Neeluru, and Vinayak S Puranik. 2026. DialPO: Dialectical Prompt Optimisation. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 42922–42938, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
DialPO: Dialectical Prompt Optimisation (B et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2017.pdf