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Autores principales: Baldelli, Davide, Parviz, Ali, Zouaq, Amal, Chandar, Sarath
Formato: Preprint
Publicado: 2026
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Acceso en línea:https://arxiv.org/abs/2601.06973
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author Baldelli, Davide
Parviz, Ali
Zouaq, Amal
Chandar, Sarath
author_facet Baldelli, Davide
Parviz, Ali
Zouaq, Amal
Chandar, Sarath
contents As LLMs move from text completion toward autonomous agents, they remain constrained by the standard chat interface, which lacks private working memory. This raises a fundamental question: can agents reliably perform interactive tasks that depend on hidden state? We define Private State Interactive Tasks (PSITs), which require agents to generate and maintain hidden information while producing consistent public responses. We show theoretically that any agent restricted to the public conversation history cannot simultaneously preserve secrecy and consistency in PSITs, yielding an impossibility theorem. To empirically validate this limitation, we introduce a self-consistency testing protocol that evaluates whether agents can maintain a hidden secret across forked dialogue branches. Standard chat-based LLMs and retrieval-based memory baselines fail this test regardless of scale, demonstrating that semantic retrieval does not enable true state maintenance. To address this, we propose a novel architecture incorporating an explicit private working memory; we demonstrate that this mechanism restores consistency, establishing private state as a necessary component for interactive language agents.
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publishDate 2026
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spellingShingle LLMs Can't Play Hangman: On the Necessity of a Private Working Memory for Language Agents
Baldelli, Davide
Parviz, Ali
Zouaq, Amal
Chandar, Sarath
Computation and Language
As LLMs move from text completion toward autonomous agents, they remain constrained by the standard chat interface, which lacks private working memory. This raises a fundamental question: can agents reliably perform interactive tasks that depend on hidden state? We define Private State Interactive Tasks (PSITs), which require agents to generate and maintain hidden information while producing consistent public responses. We show theoretically that any agent restricted to the public conversation history cannot simultaneously preserve secrecy and consistency in PSITs, yielding an impossibility theorem. To empirically validate this limitation, we introduce a self-consistency testing protocol that evaluates whether agents can maintain a hidden secret across forked dialogue branches. Standard chat-based LLMs and retrieval-based memory baselines fail this test regardless of scale, demonstrating that semantic retrieval does not enable true state maintenance. To address this, we propose a novel architecture incorporating an explicit private working memory; we demonstrate that this mechanism restores consistency, establishing private state as a necessary component for interactive language agents.
title LLMs Can't Play Hangman: On the Necessity of a Private Working Memory for Language Agents
topic Computation and Language
url https://arxiv.org/abs/2601.06973