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A change to an AI system after it has been placed on the market that affects its compliance or intended purpose under the EU AI Act.
Under the EU AI Act, a substantial modification triggers a new conformity assessment. This is particularly relevant for agentic AI or systems that are fine-tuned on new datasets, as changes to the model's logic or risk profile can strip it of its original presumption of conformity.
Real world example:
A bank updates its loan-approval AI to include new data types (like social media activity) not included in the original assessment; this is flagged as a substantial modification under the EU AI Act and requires a fresh regulatory review.
