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Main Authors: Gross, Dennis, Spieker, Helge, Gotlieb, Arnaud
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2510.06756
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author Gross, Dennis
Spieker, Helge
Gotlieb, Arnaud
author_facet Gross, Dennis
Spieker, Helge
Gotlieb, Arnaud
contents We introduce a tool for rigorous and automated verification of large language model (LLM)- based policies in memoryless sequential decision-making tasks. Given a Markov decision process (MDP) representing the sequential decision-making task, an LLM policy, and a safety requirement expressed as a PCTL formula, our approach incrementally constructs only the reachable portion of the MDP guided by the LLM's chosen actions. Each state is encoded as a natural language prompt, the LLM's response is parsed into an action, and reachable successor states by the policy are expanded. The resulting formal model is checked with Storm to determine whether the policy satisfies the specified safety property. In experiments on standard grid world benchmarks, we show that open source LLMs accessed via Ollama can be verified when deterministically seeded, but generally underperform deep reinforcement learning baselines. Our tool natively integrates with Ollama and supports PRISM-specified tasks, enabling continuous benchmarking in user-specified sequential decision-making tasks and laying a practical foundation for formally verifying increasingly capable LLMs.
format Preprint
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institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Verifying Memoryless Sequential Decision-making of Large Language Models
Gross, Dennis
Spieker, Helge
Gotlieb, Arnaud
Artificial Intelligence
We introduce a tool for rigorous and automated verification of large language model (LLM)- based policies in memoryless sequential decision-making tasks. Given a Markov decision process (MDP) representing the sequential decision-making task, an LLM policy, and a safety requirement expressed as a PCTL formula, our approach incrementally constructs only the reachable portion of the MDP guided by the LLM's chosen actions. Each state is encoded as a natural language prompt, the LLM's response is parsed into an action, and reachable successor states by the policy are expanded. The resulting formal model is checked with Storm to determine whether the policy satisfies the specified safety property. In experiments on standard grid world benchmarks, we show that open source LLMs accessed via Ollama can be verified when deterministically seeded, but generally underperform deep reinforcement learning baselines. Our tool natively integrates with Ollama and supports PRISM-specified tasks, enabling continuous benchmarking in user-specified sequential decision-making tasks and laying a practical foundation for formally verifying increasingly capable LLMs.
title Verifying Memoryless Sequential Decision-making of Large Language Models
topic Artificial Intelligence
url https://arxiv.org/abs/2510.06756