CIKM Short Paper: Knowing When to Correct Venue: ACM International Conference on Information and Knowledge Management (CIKM) Authors: Stergios Konstantinidis, Hayman Lotfy, Michalis Vlachos Affiliation: Department of Information Systems (DESI), HEC Lausanne GitHub Public: CIKM_public Overleaf Project: https://git.overleaf.com/6a1d78e803cbdf7def32a839 Core Codebase: /Users/stergios/Documents/GitHub/Optimizing-LLM-based-OCR-Corrections 1. Problem Statement At multi-million page scale, LLM-based OCR correction is constrained by cost: Full LLM correction costs hundreds of thousands of dollars on national archival collections. Many archival passages are already accurate; invoking LLMs on them introduces latency, cost, and risk of hallucinations. Core Research Questions: RQ1: How closely does selective routing match the theoretical oracle ceiling, and does it outperform naive confidence thresholding? RQ2: How well does the regression-estimated improvement \hat{Δ}_i correlate with the true realized improvement Δi? RQ3: What is the actual operational cost saved when routing only segments predicted to benefit across various frontier LLMs? Problem Visual Illustration Figure 1: Typical OCR degradation in historical periodicals requiring cost-aware routing.