Function extractExperimentData

pkg/cli/audit_report_experiments.go:73–128

extractExperimentData reads state.json from the experiment artifact directory under logsPath and returns a populated ExperimentData or nil when no experiment artifact is present. When the state file contains a non-empty "runs" array (written by pick_experiment.cjs v2+), the assignments of the most

(logsPath string)

// variant is inferred by the max-count heuristic: the variant with the highest cumulative
// count is assumed to have been selected last (ties broken by sorted variant order).
func extractExperimentData(logsPath string) *ExperimentData {
	if logsPath == "" {
		return nil
	}

	experimentDataLog.Printf("Extracting experiment data from: %s", logsPath)

	statePath := findExperimentStatePath(logsPath)
	if statePath == "" {
		experimentDataLog.Print("No experiment state file found")
		return nil
	}

	experimentDataLog.Printf("Reading experiment state from: %s", statePath)
	raw, err := os.ReadFile(statePath)
	if err != nil {
		return nil
	}

	var state experimentStateJSON
	if err := json.Unmarshal(raw, &state); err != nil || len(state.Counts) == 0 {
		return nil
	}

	experimentDataLog.Printf("Found %d experiment(s) in state file", len(state.Counts))

	// When per-run records are available, use the most recent run's assignments directly
	// instead of inferring them from cumulative counts.
	if len(state.Runs) > 0 {
		lastRun := state.Runs[len(state.Runs)-1]
		if len(lastRun.Assignments) > 0 {
			experimentDataLog.Printf("Using run record from run_id=%s (timestamp=%s)", lastRun.RunID, lastRun.Timestamp)
			return &ExperimentData{
				Assignments:      lastRun.Assignments,
				CumulativeCounts: state.Counts,
			}
		}
	}

	// Derive this-run assignments: the variant selected on the most-recent run is
	// the one with the maximum count (ties resolved by sorted order).
	assignments := make(map[string]string, len(state.Counts))
	names := sliceutil.SortedKeys(state.Counts)

	for _, name := range names {
		variantCounts := state.Counts[name]
		selected := deriveLastSelectedVariant(variantCounts)
		assignments[name] = selected
		experimentDataLog.Printf("Experiment %q: selected variant=%q", name, selected)
	}

	return &ExperimentData{
		Assignments:      assignments,
		CumulativeCounts: state.Counts,
	}
}

// formatExperimentLabel returns a compact, human-readable label summarising the