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Migration from Legacy

Migrate from string-key or enum-key flag systems without changing user-facing behavior during cutover.

Prerequisites: You can load snapshots safely.

Step 1: Mirror Legacy Flags as Typed Declarations​

Declare equivalent features in Konditional, preserving semantic defaults.

Step 2: Run Dual Evaluation (Baseline + Candidate)​

import io.amichne.konditional.api.ShadowOptions
import io.amichne.konditional.api.evaluateWithShadow

val value = AppFeatures.newCheckout.evaluateWithShadow(
  context = ctx,
  candidateRegistry = konditionalCandidate,
  baselineRegistry = legacyBaseline,
  options = ShadowOptions.of(reportDecisionMismatches = true),
) { mismatch ->
  logger.warn("shadow mismatch key=${mismatch.featureKey} kinds=${mismatch.kinds}")
}

Use baseline return values in production behavior until mismatch rate is acceptable.

Step 3: Cutover and Keep Rollback Ready​

  • Switch caller to Konditional baseline only after mismatch thresholds are met.
  • Keep old system available until rollback criteria expire.

Expected Outcome​

After this guide, you can migrate safely using shadow comparison, explicit mismatch reporting, and reversible rollout controls.

Next Steps​