Traceability is the technical and procedural requirement under the EU AI Act for providers of high-risk AI systems to implement automated, secure logging mechanisms that record significant events throughout the system’s lifecycle, creating an immutable audit trail of its operation and decision-making.
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This requirement ensures that the functioning of an AI system is not ephemeral but can be reconstructed, reviewed, and investigated after the fact. Traceability focuses on capturing the "digital footprint" of the system's operation in production, logging inputs, system parameters, outputs, and human interactions. It is a core enabler for ex-post compliance verification, incident investigation, and accountability. By maintaining detailed activity logs, providers and authorities can pinpoint the root cause of malfunctions, demonstrate due diligence in the event of a dispute, and validate that the system operated within its defined boundaries and according to its instructions for use.

An effective traceability system must capture and retain several key data points:

Event Logging: Automatically recording timestamps, unique identifiers for each decision or interaction, the specific version of the AI model in use, and the main processing steps undertaken.

Input/Output Recording: Logging the data inputs provided to the system (with appropriate privacy safeguards) and the corresponding outputs or decisions generated, allowing for a direct correlation.

Human-AI Interaction Tracking: Documenting instances of human oversight, including any interventions, overrides, or confirmations made by the human operator during the system's use.

System State Monitoring: Recording relevant system performance metrics and environmental conditions at the time of operation to contextualize decisions.

Regulatory Context: Traceability is a key component of the broader record-keeping and post-market monitoring obligations under the EU AI Act (Articles 19 and 61). It provides the evidentiary backbone for demonstrating ongoing compliance and is essential for conducting the root-cause analysis required for serious incident reporting under Article 62.

Accountability Mechanism: Robust traceability transforms accountability from a theoretical principle into a practical reality. It allows providers to prove that a system functioned as intended and enables deployers to audit its use within their organization. In legal proceedings or regulatory investigations, a comprehensive audit trail is often the single most important piece of evidence for defending or attributing responsibility.