Defines user flows, lifecycle states, permission prompts, offline behavior, and platform-specific edge cases for biometric authentication. It fixes adoption boundaries and observable failure evidence while keeping 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 Biometric authentication, adopt a platform-neutral domain contract with explicit native adapters. Define a deterministic user journey with visible state, reversible choices where possible, preserved input, and accessible recovery. 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 Biometric authentication actors, inputs, outputs, states, policy or schema versions, and externally visible outcomes described by this ux 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
- Model foreground, background, terminated, offline, restored, signed-out, and permission-denied states where the feature depends on them.
- Treat operating-system callbacks and external links as untrusted input and re-authorize the resulting domain action.
- Store sensitive keys only through platform-protected facilities and minimize values copied to notifications, logs, backups, and clipboards.
- Make synchronization operations idempotent with durable versions or operation identifiers rather than elapsed-time assumptions.
- Show progress only while work is actually pending and prevent duplicate activation without hiding the user's committed intent.
- Use plain, action-specific messages that distinguish validation, permission, connectivity, conflict, and terminal failure.
- Use platform biometric APIs to unlock a device-bound protected credential; do not receive or store biometric templates in the application.
- Re-enrollment, device compromise, lockout, fallback, and account recovery require explicit assurance and session transitions.
Implementation guidance
- Prototype the longest, empty, slow, offline, denied, and assistive-technology paths before locking the happy-path layout.
- Model Biometric authentication inputs, outputs, actors, states, invariants, side effects, and evidence before selecting framework or vendor details.
- Store the applicable Biometric authentication 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
- Interrupted native work resumes from a durable checkpoint or returns to a safe visible state without duplicating side effects.
- Invalid or contradictory Biometric authentication 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
- Complete the journey with keyboard, touch, screen reader, narrow viewport, delayed network, and a recoverable server error.
- Monitor Biometric authentication 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.