RECAP: Regression Evaluation for Continual Adaptation of Prompts

Harsh Deshpande, Kushal Chawla, Sangwoo Cho, William M. Campbell, Sambit Sahu


Abstract
Production agentic systems routinely face evolving constraints and must comply from the very next interaction. Scenarios like a tool-call notification changing a compliance threshold or a policy update adding disclosure requirements fit this criteria, having close to no room for errors in production. This proactive adaptation setting is common in deployment, but absent from current benchmarks, which assume either static constraint sets or reactive protocols with evaluation feedback. We introduce RECAP, a benchmark that measures continual-learning phenomena (forgetting, regression, forward transfer) at the constraint level under a strictly proactive adapt-then-test protocol: prompt optimization methods receive only the constraint specification and must generalize before seeing any test data. Evaluating six methods across five LLMs and three schedules with evolving constraints, we find that these methods show no significant improvement in performance, even after incurring a higher latency. These methods, designed for offline or reactive settings, are inadequate for the proactive paradigm. Our work emphasizes the growing need for designing proactive prompt adaptation methods, where the models must remain robust to evolving needs in deployment.
Anthology ID:
2026.emnlp-main.1684
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
38317–38331
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1684/
DOI:
Bibkey:
Cite (ACL):
Harsh Deshpande, Kushal Chawla, Sangwoo Cho, William M. Campbell, and Sambit Sahu. 2026. RECAP: Regression Evaluation for Continual Adaptation of Prompts. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 38317–38331, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
RECAP: Regression Evaluation for Continual Adaptation of Prompts (Deshpande et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1684.pdf