Substantial Modification Threshold Check per Change Every system change identified through the PMM feedback loop is assessed against the substantial modification thresholds defined in Article 3(23). A change that crosses the threshold triggers a new conformity assessment cycle (returning to Phase 5 of the delivery framework, ). A change that does not cross the threshold is documented in the AISDP change history (Module 12) through the standard change management framework. The assessment uses the criteria established during Phase 3: does the change affect the system’s intended purpose, its architecture, its training data, its performance characteristics, or its risk profile in a way that could affect compliance with Articles 8–15? The AI System Assessor conducts the assessment, and the AI Governance Lead reviews borderline cases. A model retrain on updated data where the retrained model meets all existing validation gates and does not change the system’s intended purpose typically does not constitute a substantial modification. A model retrain that changes the feature set, alters the decision boundary significantly, or introduces a new data source may cross the threshold. Key outputs

• Per-change substantial modification assessment
• Article 3(23) criteria applied by AI System Assessor
• Threshold crossing triggers return to Phase 5
• Non-threshold changes documented in AISDP change history