Abstract
Large language model agents increasingly operate through environment-facing scaffolds that expose files, web pages, APIs, and logs. These observations influence tool use, state tracking, and action sequencing, yet their reliability and authority are often uncertain. Environmental grounding is therefore a systems-level problem involving context admission, evidence provenance, freshness checking, verification policy, action gating, and model reasoning. Existing agent benchmarks mainly evaluate task capability or specific attacks such as prompt injection and memory poisoning, but they under-specify a fundamental reliability question: whether agents remain grounded in the true environment state when observations are stale, incorrect, or malicious. We introduce EnvTrustBench, an agentic framework for benchmarking this failure mode. We define an evidence-grounding defect (EGD) as a behavioral failure in which an agent treats an environment-facing claim as sufficient evidence for action without resolving it against available current evidence, leading to a task-incorrect false path under the true environment state. Given a task scenario, EnvTrustBench generates the workspace, environment, agent-facing objective, and validation oracle, executes the evaluated agent, records its action-observation trajectory and final state, and applies the oracle to produce a verdict. Using 6 LLM backbones and 5 widely used scaffolds, we evaluate 55 generated cases across 11 task scenarios, with each scenario expanded through five feedback-guided generation iterations. Results show that EGDs consistently emerge across operational workflows, highlighting environmental grounding as a core agent reliability problem with important security implications.
Bullet Summary
- Large language model (LLM) agents rely on environmental evidence from files, APIs, logs, etc., which can be stale, incorrect, or malicious, posing reliability and security risks.
- An Evidence-Grounding Defect (EGD) is identified as a critical failure mode where an agent overtrusts environmental claims without verifying them against current evidence, leading to incorrect actions.
- EnvTrustBench is introduced as an extensible agentic benchmarking framework that generates task scenarios, controlled environments, and validation oracles to systematically detect and evaluate EGDs in LLM agents.
- The framework models agent runtime state and assumes a threat model where environmental claims can be manipulated adversarially, while workspace and tools remain trusted.
- Extensive evaluation using 6 LLM backbones, 5 scaffolds, and 11 task scenarios (3,850 trials) reveals a high Environmental Misgrounding Rate (EMR) averaging 83.3%, showing EGDs are widespread and a significant reliability problem.