Challenger's value for that metric (or null when absent).
challenger − incumbent (when both present).
Plain-language explanation (business-friendly).
Incumbent's value for that metric (or null when absent).
The configured promotion margin the delta was tested against.
The metric key the comparison used.
promote when delta ≥ margin, else hold. NEVER triggers an actual promotion.
The result of evaluating a freshly-retrained challenger against the incumbent.