Trusted Uncertainty in Large Language Models: A Unified Framework for Confidence Calibration and Risk-Controlled Refusal
This work addresses the lack of controllable refusal capability in large language models (LLMs). We propose the first unified framework for uncertainty calibration and risk-controlled rejection tailored to API-based black-box LLMs—requiring no fine-tuning and offering distribution-free theoretical guarantees. Methodologically, it integrates heterogeneous uncertainty signals—including sequence likelihood, self-consistency dispersion, retrieval compatibility, and tool feedback—into a lightweight calibration via temperature scaling and adaptive scoring, then enforces principled rejection using conformal risk control under user-specified error budgets. Key innovations include fine-grained factual alignment and interpretable refusal. Experiments across short-form QA, code generation, and retrieval-augmented long-text generation demonstrate substantial improvements over entropy- and logit-threshold baselines: lower calibration error, superior area under the risk–coverage curve, and higher coverage at fixed risk levels.