Spacing: Implementation and governance
Translates spacing into reusable assets, tooling, documentation, ownership, and verification rules. This reference fixes the adoption boundary, failure behavior, and observable evidence while leaving environment-specific limits configurable.
Package status: reference context ready for human review. The contract and test scenarios are complete, but no claim is made that an adopting implementation has passed them.
Decision
For Spacing, adopt versioned design tokens and component contracts shared by design and implementation. Implement the behavior through one authoritative write path, typed interfaces, explicit state, and idempotent side-effect handling. This implementation block focuses specifically on implementation and governance. This package is a reference contract: the adopting team must choose numeric limits, providers, jurisdictions, and operational owners from evidence in its own environment.
Scope
- The Spacing actors, inputs, outputs, states, policy or schema versions, and externally visible outcomes required for the implementation and governance focus of this implementation block.
- Primary and alternate interfaces, background work, caches, integrations, support paths, and evidence that can exercise the same boundary.
- Adoption-specific configuration, rollout, recovery, and verification responsibilities needed to apply the reference safely.
Outside this block
- Choosing a universal vendor, framework, jurisdiction, numeric threshold, retention period, or service-level objective for every adopter.
- Claiming that packaged scenarios have run against a downstream implementation or that this reference grants legal, security, or accessibility certification.
Contract
- Name tokens by semantic purpose; product code does not depend on raw palette, spacing, or typography values when a semantic token exists.
- Define allowed variants and states with accessibility behavior, content constraints, and responsive behavior in the same contract.
- Treat breaking token or component changes as migrations with ownership, compatibility notes, and measurable adoption.
- Use visual checks as change evidence, not as the sole test for semantics, keyboard operation, or accessible names.
- Validate inputs once at the boundary and preserve the normalized representation used by downstream logic.
- Persist the business transition before or atomically with an outbox record; consumers deduplicate by durable operation identity.
- Define a constrained semantic spacing scale for component internals, relationships, layout, density, and safe areas and generate platform values from versioned tokens.
- Test nesting, zoom, text scaling, long locale content, touch targets, narrow screens, and bidirectional layout and migrate exceptions instead of accumulating arbitrary gaps.
- For the implementation and governance variant, enforce this declared boundary: translates spacing into reusable assets, tooling, documentation, ownership, and verification rules.
Implementation guidance
- Ship additive storage and interface changes first, backfill observably, then retire old paths after compatibility evidence.
- Model Spacing inputs, outputs, actors, states, invariants, side effects, and evidence before selecting framework or vendor details.
- Store the applicable Spacing contract or policy version with material state so migrations, replay, and support decisions remain attributable.
- Introduce the path behind controlled rollout, compare expected and observed outcomes, and keep a tested recovery route until adoption evidence is complete.
Failure handling and safeguards
- An unknown token or variant fails visibly in development and uses a documented safe fallback in released clients.
- Invalid or contradictory Spacing state is rejected or quarantined; the implementation never guesses a value that broadens authority or duplicates an effect.
- Retries are bounded and use durable identity; after exhaustion, work reaches an inspectable terminal state with an accountable owner.
Verification and operations
- Inject dependency failure before and after persistence and prove that retry converges on one externally visible outcome.
- Monitor Spacing success, denial, validation failure, dependency failure, retry exhaustion, and recovery by contract version without sensitive payload dimensions.
- Re-run paired positive and negative fixtures after policy, schema, dependency, migration, or boundary changes and preserve the resulting evidence.
Adoption assumptions
- Names and values in the example are a concrete fixture, not universal defaults; adopters replace them through documented evidence and ownership.
- The adopting system can provide authenticated identity, durable operation or record versions, bounded telemetry, and a controlled path for change.
The executable-looking examples in this package are fixtures and acceptance contracts. Run the collection validator to check structure and metadata, then translate and execute the scenarios in the target repository before recording implementation evidence.