Theoretical Bounds for Stable In-Context Learning
- URL: http://arxiv.org/abs/2509.20677v1
- Date: Thu, 25 Sep 2025 02:25:05 GMT
- Title: Theoretical Bounds for Stable In-Context Learning
- Authors: Tongxi Wang, Zhuoyang Xia,
- Abstract summary: In-context learning (ICL) is flexible but its reliability is sensitive to prompt length.<n>This paper establishes a non-asymptotic lower bound that links the minimal number of demonstrations to ICL stability.<n>We propose a two-stage observable estimator with a one-shot calibration that produces practitioner-ready prompt-length estimates.
- Score: 0.0
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: In-context learning (ICL) is flexible but its reliability is highly sensitive to prompt length. This paper establishes a non-asymptotic lower bound that links the minimal number of demonstrations to ICL stability under fixed high-dimensional sub-Gaussian representations. The bound gives explicit sufficient conditions in terms of spectral properties of the covariance, providing a computable criterion for practice. Building on this analysis, we propose a two-stage observable estimator with a one-shot calibration that produces practitioner-ready prompt-length estimates without distributional priors. Experiments across diverse datasets, encoders, and generators show close alignment between the predicted thresholds and empirical knee-points, with the theory acting as a conservative but reliable upper bound; the calibrated variant further tightens this gap. These results connect spectral coverage to stable ICL, bridge theory and deployment, and improve the interpretability and reliability of large-scale prompting in realistic finite-sample regimes.
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