RAIL Guard: Closing the Evaluation-to-Remediation Gap in Responsible AI for LLM Agents RAIL Guard, a closed-loop responsible AI pipeline introduced in a new arXiv paper, evaluates LLM outputs across eight dimensions and iteratively remediates failures, achieving 96.9% convergence versus 49.1% for block-and-retry. The system, tested on four frontier LLMs with 4,276 content outputs and 6,400 tool-call scenarios, reduces unsafe agent executions by 33% with zero impact on task completion, though structural dimensions like Transparency (93.0% failure) require architectural solutions. The pipeline is available as open-source SDKs. arXiv:2607.16215v1 Announce Type: new Abstract: Existing guardrail systems for large language model agents operate as binary classifiers that block unsafe content, leaving organizations to discard failing outputs and retry from scratch. We introduce RAIL Guard, a closed-loop responsible AI pipeline that evaluates LLM outputs across eight measurable dimensions and iteratively remediates failing outputs through an evaluate-rewrite-reevaluate loop. We evaluate the pipeline across three experiments on four frontier LLMs and 4,276 content outputs plus 6,400 agent tool-call scenarios. Closed-loop remediation achieves 96.9% convergence versus 49.1% for block-and-retry, though the highest-convergence method reduces utility by 22.3%; feedback-driven self-repair achieves 86.6% convergence on fixable dimensions with no significant utility loss p = 0.177 . Pre-tool-call evaluation reduces unsafe agent executions by 33% p = 0.007 with zero impact on task completion. We identify a key distinction between fixable dimensions that respond to remediation and structural dimensions Transparency at 93.0%, Accountability at 92.8%, and Inclusivity at 82.5% failure that require architectural rather than algorithmic solutions. The system is available as open-source SDKs.