phone-auth

phone-auth is a skill for Claude Code, Codex from launch52-ai/flutter-template. It costs 39 tokens per session (905 once invoked), scanned A, original, MIT.

A phone-number login and verification flow using one-time passwords, or OTPs. It covers country selection, phone formatting, international E.164 validation, countdowns, retries, and error messages.

In plain words
What is it for?
Use it to add phone signup or login, country pickers, formatted phone fields, OTP entry, retry handling, and Supabase or custom-backend support.
Why use it?
It separates the mobile app’s input and verification experience from backend responsibilities such as generating codes, limiting attempts, and storing them securely.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/launch52-ai/flutter-template/phone-auth
Any agent
npx skills add launch52-ai/flutter-template --skill phone-auth
Clone the repo
git clone --depth 1 https://github.com/launch52-ai/flutter-template

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for phone-auth

README.md
[![agentmods](https://agentmods.dev/badge/skills/launch52-ai/flutter-template/phone-auth.svg)](https://agentmods.dev/skills/launch52-ai/flutter-template/phone-auth)
Your own site
<a href="https://agentmods.dev/skills/launch52-ai/flutter-template/phone-auth"><img src="https://agentmods.dev/badge/skills/launch52-ai/flutter-template/phone-auth.svg" alt="Measured on agentmods" height="20"></a>
Per session 39 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 905 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00039 $0.00905
Opus 5 $0.00019 $0.00452
Sonnet 5 $0.00008 $0.00181
Haiku 4.5 $0.00004 $0.00090

Measured 3d ago against content hash 23e011599e47, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

phone-auth scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/phone-auth/SKILL.md · 112 lines

How it starts

The opening of the file, as written. The whole thing — 112 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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

  1. Backend type: Supabase or Custom API?
  2. 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

  1. Copy data/countries.json to assets/data/
  2. Copy reference files to project (see implementation-guide.md)
  3. Implement repository (Supabase or API) - see implementation-guide.md
  4. Register provider in lib/core/providers.dart
  5. Run dart run build_runner build
  6. 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

Read the full file on GitHub · 112 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 112 lines · 39 tokens per session scan A 23e011599e47

Subscribe to this mod's changes

phone-auth is a skill published in the GitHub repository launch52-ai/flutter-template (2 stars, last pushed 6mo ago), licensed MIT. It adds 39 tokens to every session and 905 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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