SAGE: Stochastic Prompt Optimization via Agent-Guided Exploration

Ziyi Zhu, Luka Smyth, Saki Shinoda, Jinghong Chen


Abstract
Context engineering has emerged as a primary lever for improving AI systems without parameter updates. Recent work showing that textual gradients do not function as real gradients motivates treating automatic prompt optimization (APO) as black-box search. We introduce SPO (Stochastic Prompt Optimization), a framework for stochastic search over prompt space, and compare three strategies of increasing sophistication: error-informed random search, a genetic algorithm with evolutionary operators, and SAGE (SPO via Agent-Guided Exploration), a multi-agent pipeline with diagnostic code execution. Across three benchmarks, no single strategy dominates; effectiveness depends on the interaction of landscape structure with error type. We further deploy SAGE on a mental-health chatbot under a continuous optimization paradigm, where it compounds eight cycles of individually-noisy A/B tests into a statistically robust gain in next-day retention. We argue that coupling qualitative diagnosis with quantitative validation is what makes agentic optimization effective for open-ended task-oriented dialogue.
Anthology ID:
2026.emnlp-industry.221
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Pepa Atanasova, Gholamreza Haffari, Minghan Wang
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
3695–3711
Language:
URL:
https://aclanthology.org/2026.emnlp-industry.221/
DOI:
Bibkey:
Cite (ACL):
Ziyi Zhu, Luka Smyth, Saki Shinoda, and Jinghong Chen. 2026. SAGE: Stochastic Prompt Optimization via Agent-Guided Exploration. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track, pages 3695–3711, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SAGE: Stochastic Prompt Optimization via Agent-Guided Exploration (Zhu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-industry.221.pdf