peterbamuhigire/ios-biometric-login

Platform Notes

• Optional helper plugins may help in some environments, but they must not be treated as required for this skill.

iOS Biometric Login

<!-- dual-compat-start -->

Use When

• Optional biometric (Face ID/Touch ID) gate on iOS app launch using LocalAuthentication framework. Covers BiometricHelper utility, splash screen integration, settings toggle with verification, Keychain-backed preference storage, and graceful...
• The task needs reusable judgment, domain constraints, or a proven workflow rather than ad hoc advice.

Do Not Use When

• The task is unrelated to ios-biometric-login or would be better handled by a more specific companion skill.
• The request only needs a trivial answer and none of this skill's constraints or references materially help.

Required Inputs

• Gather relevant project context, constraints, and the concrete problem to solve.
• Confirm the desired deliverable: design, code, review, migration plan, audit, or documentation.

Workflow

• Read this SKILL.md first, then load only the referenced deep-dive files that are necessary for the task.
• Apply the ordered guidance, checklists, and decision rules in this skill instead of cherry-picking isolated snippets.
• Produce the deliverable with assumptions, risks, and follow-up work made explicit when they matter.

Quality Standards

• Keep outputs execution-oriented, concise, and aligned with the repository's baseline engineering standards.
• Preserve compatibility with existing project conventions unless the skill explicitly requires a stronger standard.
• Prefer deterministic, reviewable steps over vague advice or tool-specific magic.

Anti-Patterns

• Treating examples as copy-paste truth without checking fit, constraints, or failure modes.
• Loading every reference file by default instead of using progressive disclosure.

Outputs

• A concrete result that fits the task: implementation guidance, review findings, architecture decisions, templates, or generated artifacts.
• Clear assumptions, tradeoffs, or unresolved gaps when the task cannot be completed from available context alone.
• References used, companion skills, or follow-up actions when they materially improve execution.

References

• Use the links and companion skills already referenced in this file when deeper context is needed.

<!-- dual-compat-end -->

Add optional Face ID / Touch ID authentication as a gate on app launch. Uses the LocalAuthentication framework (LAContext). The feature is opt-in: users enable it in Settings, and it triggers on every app launch from the splash screen.

Overview

Flow: App launch → Splash → Check biometric pref → LAContext prompt → Success (Main) or Failure (Login screen).

Key principles:

• Optional, not mandatory — users choose to enable via a Settings toggle
• Verify before enabling — require biometric auth to turn the feature ON (prevents unauthorised enabling)
• Graceful degradation — if device has no biometric hardware, hide the toggle entirely
• Survive logout — biometric preference persists across logout/re-login (stored in Keychain)
• No custom UI — use the system biometric dialog (consistent UX, handles retries)

Framework

No third-party dependencies. Uses Apple's built-in LocalAuthentication framework.

import LocalAuthentication

No CocoaPods, SPM packages, or Cartfile entries needed.

Additional Guidance

Extended guidance for ios-biometric-login was moved to references/skill-deep-dive.md to keep this entrypoint compact and fast to load.

Use that deep dive for:

• Architecture
• Step 1: BiometricHelper (Actor)
• Step 2: KeychainHelper for Preference Storage
• Step 3: Splash Screen with Biometric Gate
• Step 4: Settings Toggle with Verify-Before-Enable
• Step 5: Info.plist Configuration
• Flow Diagram
• Patterns & Anti-Patterns
• Edge Cases
• Integration with Other Skills
• Checklist