Design tokens: Implementation and governance

Immutable semver releases for design-token packages with alias resolution, compatibility gates, and rollback-safe distribution so consumers never bind to unvalidated draft token sets across surfaces.

Package status: AI-assisted reference package. Static package validation has passed; implementation scenarios remain not run and human domain review is required before stable adoption.

Decision

Publish design tokens as immutable semver packages in a single registry, expose only vetted aliases such as stable and previous-stable, and require compatibility gates before any alias moves. Consumers may pin an exact version or follow an alias deliberately; draft token sets never ship to production aliases.

Scope

• Version numbering, changelog requirements, alias maps, and publish immutability for token packages.
• Cross-surface distribution to web and native consumers that share a registry.
• Rollback of alias pointers within a bounded operator window after a bad release.
• Deprecation lifecycle for renamed or removed tokens.

Outside this block

• Authoring token semantics, color science, or component styling rules.
• Runtime theme switching mechanics (see the dark-mode theme contract block).
• General package registry administration unrelated to design tokens.

Contract

• A published token release at version X.Y.Z is immutable; republishing the same version with different content is rejected.
• Breaking token renames or removals require a major semver bump; minor and patch releases must remain backward compatible for all non-deprecated public aliases.
• Production aliases (stable, previous-stable) reference only releases that passed the profile compatibility gates; draft or local builds cannot satisfy an alias.
• Consumers that pin an exact version continue to resolve that version after alias repointing unless they explicitly upgrade.
• Deprecated tokens remain readable for the configured grace period and emit a build-time or CI-visible warning before hard failure.
• Rollback repoints stable to previous-stable (or a named safe version) within the profile rollback window and records actor, reason, and affected digest.
• Adoption metrics expose which surfaces consume which token version so cross-surface drift is observable within one reporting interval.

Implementation guidance

• Store tokens in a format your toolchain can diff (JSON, Style Dictionary, or CSS custom properties export) and attach a release manifest similar to token-release.yaml.
• Run visual or contrast diff gates on representative screens before alias promotion; block publish when required tokens are missing from the export.
• Treat alias updates as infrastructure changes: require two-person approval or automated canary on a staging consumer before repointing stable.
• Document supported version combinations when web and native release on different cadences.

Failure handling and safeguards

• If a publish succeeds but downstream gates fail afterward, leave aliases unchanged and mark the release as withdrawn rather than deleting the immutable artifact.
• If rollback is invoked outside the window, require an explicit break-glass ticket and retain both versions until consumers confirm migration.
• If a consumer requests a withdrawn version, return the artifact with a prominent deprecation header rather than silently substituting tokens.
• If registry replication lag causes mixed versions across regions, halt alias movement until all replicas serve the same digest.

Verification and operations

• Track alias repoint events, rollback count, deprecated-token references in CI, and per-surface version adoption ratio.
• Alert when any production surface remains on a version older than the minimum support window for longer than the profile threshold.
• Rehearse rollback quarterly on a staging alias to verify manifests and consumer pins behave as expected.

Adoption assumptions

• Names and numeric values in example.yaml and token-release.yaml are an adoption profile, not universal defaults.
• The adopting team owns registry credentials, visual diff tooling, and the definition of breaking change for its token schema.

References

• css-variables
• semver