We study how firms exposed to concentrated algorithmic infrastructure are repriced when U.S. export controls alter access to that infrastructure. We construct an Algorithmic Dependence Index (ADI) from 89,965 corporate 10-K filings measuring exposure to cloud platforms, AI accelerators, and semiconductor supply chains. Around nineteen policy events between 2018 and 2025, a one-standard-deviation increase in ADI predicts -0.201% lower three-day abnormal returns (t = -2.39); on the options-listed subsample the effect strengthens to -0.299%. Infrastructure providers are insulated. The mechanism is regime uncertainty rather than directional restriction: loosening events hurt high-ADI firms as much as tightening events, and implied volatility rises for dependent firms even when headlines signal relaxation.