Phone auth

Skill launch52-ai/flutter-template/.claude/skills/phone-auth

Template for Flutter mobile applications.

Install

npx -y skills add launch52-ai/flutter-template --skill phone-auth

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Phone OTP authentication - country data, phone formatting, E.164 validation, rate limiting, retry patterns. Use when implementing phone verification flows. Supports Supabase and custom backends.

SKILL.md

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Phone Auth - Phone OTP Authentication

Phone number OTP authentication with Clean Architecture. Backend handles security (OTP generation, rate limiting). Mobile handles UX (formatting, countdown, error display).

When to Use This Skill

Adding phone number login/signup to a Flutter app
Implementing OTP verification flows
User asks to "add phone auth", "phone login", or "OTP verification"

Questions to Ask

Backend type: Supabase or Custom API?
Countries data: Local JSON (faster) or Backend API (dynamic)?

Responsibilities

Mobile	Backend
Display country picker	OTP generation (cryptographic)
Format phone input	OTP storage (hashed)
Convert to E.164	Rate limiting
Show countdown timer	Expiration checking
Display errors	Attempt counting
Call backend APIs	User auth/creation

Reference Files

reference/
├── models/           # Country model (Freezed)
├── utils/            # Phone formatting, E.164 conversion
├── repositories/     # Domain interface + mock
├── providers/        # Riverpod notifier + state
└── failures/         # Sealed Failure types

See: implementation-guide.md for complete file list and copy instructions.

Workflow

Copy data/countries.json to assets/data/
Copy reference files to project (see implementation-guide.md)
Implement repository (Supabase or API) - see implementation-guide.md
Register provider in lib/core/providers.dart
Run dart run build_runner build
Use /design for UI components

Core API

// Format and convert
final e164 = PhoneFormatUtils.toE164(localNumber, country);

// Send OTP
await repository.sendOtp(e164);

// Verify OTP
await repository.verifyOtp(phoneNumber, otp);

Failure Types

Type	When	UI Action
`InvalidPhoneFailure`	Bad format	Validation error
`RateLimitFailure(retryAfter)`	Too many sends	Countdown
`InvalidOtpFailure(remaining)`	Wrong OTP	Show attempts
`OtpExpiredFailure`	OTP timed out	Resend option
`MaxAttemptsFailure`	3+ failures	Force new OTP
`PhoneAuthNetworkFailure`	Connection	Retry button

Retry Pattern

Escalating intervals: 30s → 40s → 60s → 90s → 120s

See reference/providers/phone_auth_providers.dart for configuration.

Guides

File	Content
implementation-guide.md	Step-by-step with Supabase + API examples
best-practices-guide.md	Security, UX patterns
phone-formats-guide.md	E.164, country formats
checklist.md	Implementation verification

Checklist

countries.json copied to assets/data/
PhoneAuthRepository interface extends base AuthRepository
sendOtp(e164PhoneNumber) and verifyOtp(phone, otp) implemented
PhoneFormatUtils handles E.164 conversion
All Failure types implemented (InvalidPhone, RateLimit, InvalidOtp, etc.)
Retry intervals configured (30s → 40s → 60s → 90s → 120s)
Provider registered in lib/core/providers.dart
build_runner executed successfully
Error messages use i18n keys

Related Skills

/social-login - Can combine with phone auth
/design - Phone input and OTP UI components
/i18n - Localized error messages
/testing - Unit and widget tests