NITI: Neural Plan Concretization for Incremental Execution, Bridging and Trigger Inference from Underspecified Human Policies
Summary
The paper examines how to make large language models reliably execute abstract human policies, such as clinical guidelines. Such policies deliberately do not enumerate all preconditions and contingencies. The authors propose NITI, a neurosymbolic framework in which the LLM does not plan on its own but instead instantiates a given policy step by step at execution time. NITI has four mechanisms. Formal parameterized action schemas describe how the state changes. Trigger inference determines which stage of the policy corresponds to the current state, while short-circuiting skips subgoals that have already been achieved. A verifier provides feedback used to repair actions. Neural bridging returns the system to a point where the policy is applicable again. If the state is inconsistent, execution halts safely. The framework operates solely through in-context learning, without fine-tuning. It was evaluated on a new benchmark of 50 official WCA scrambles of the 2×2 cube and on 102 automated insulin delivery (AID) scenarios. Baseline methods solve none of the scrambles, whereas NITI with Claude Opus 4.5 solves 94% and nearly matches classical MPC in safety. The authors conclude that LLM planners lack execution structure rather than model capacity.
Key points
- WCA 2×2 benchmark: solutions are typically longer than 10 moves, whereas in Sys2Bench they are mostly shorter than 4. With NITI, the share of solved scrambles is 94% for Claude Opus 4.5, 76% for GPT-5.2, and 36% for GPT-o4-mini. One-shot, CoT, and PoT yield 0%.
- AID: the share of safe runs increased from 41.2% (one-shot) to 96.1% (NITI + Claude Opus 4.5), compared with 97% for MPC. Time in Range is 81% versus 78.2% for MPC. The share of hallucinated corrective actions decreased from 31.6% to 1.1%.
- In the ablation, neural bridging proved the most important: without it, Opus's result drops from 94 to 34 points. Verifier-grounded repair, trigger inference, and short-circuiting follow in order of impact.
- Overhead: a one-time learning phase requires 35 model calls, after which each task needs only a single call.
- The code and benchmark are open: github.com/ImpactLabASU/ACLNITI.
Cite
@inproceedings{banerjee2026niti,
title = {{NITI: Neural Plan Concretization for Incremental Execution, Bridging and Trigger Inference from Underspecified Human Policies}},
author = {Banerjee, Ayan and Banerjee, Shomrik Barua and Gupta, Sandeep},
booktitle = {Findings of the Association for Computational Linguistics: ACL 2026},
year = {2026},
doi = {10.18653/v1/2026.findings-acl.2007},
url = {https://doi.org/10.18653/v1/2026.findings-acl.2007}
}References
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