auth-builder-agent

auth-builder-agent is an agent for Claude Code from TheLobbi/claude. It costs 34 tokens per session (2,170 once invoked), scanned A, original, MIT.

An authentication implementation generator for common login and access-control methods. It covers OAuth 2.0, API keys, JWTs, sessions, mutual TLS, and other token or credential schemes.

In plain words
What is it for?
Use it to implement OAuth login, PKCE, API-key checks, JWT signing and verification, token refresh, multi-tenant access, sessions, and authentication tests.
Why use it?
It removes the need to assemble token handling, credential storage, refresh logic, and authentication errors from separate pieces. It helps apply the selected authentication rules consistently across an application.

Agent for Claude Code

Written for Claude Code: installed under .claude/.

Part of the api-integration-helper plugin — 10 agents shipped together

Good fit Use it to implement OAuth login, PKCE, API-key checks, JWT signing and verification, token refresh, multi-tenant access, sessions, and authentication tests.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/thelobbi/claude/auth-builder-agent
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.

Clone the repo
git clone --depth 1 https://github.com/TheLobbi/claude

Made for: Claude Code.

Or install api-integration-helper, the plugin that ships this one along with the rest of its 10 agents.

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 auth-builder-agent

README.md
[![agentmods](https://agentmods.dev/badge/agents/thelobbi/claude/auth-builder-agent.svg)](https://agentmods.dev/agents/thelobbi/claude/auth-builder-agent)
Your own site
<a href="https://agentmods.dev/agents/thelobbi/claude/auth-builder-agent"><img src="https://agentmods.dev/badge/agents/thelobbi/claude/auth-builder-agent.svg" alt="Measured on agentmods" height="20"></a>
Per session 34 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,170 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00034 $0.02170
Opus 5 $0.00017 $0.01085
Sonnet 5 $0.00007 $0.00434
Haiku 4.5 $0.00003 $0.00217

Measured 2d ago against content hash f0aead8f3cf6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

auth-builder-agent scanned grade A with 1 finding 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 2d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

const response = await fetch(this.config.tokenUrl, {
.claude/plugins/api-integration-helper/agents/auth-builder-agent.md · 376 lines

How it starts

The opening of the file, as written. The whole thing — 376 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Auth Builder Agent

Callsign: Guardian Model: Sonnet Specialization: Authentication and authorization flow implementation

Purpose

Implements production-ready authentication flows including OAuth 2.0, PKCE, API keys, JWT, and custom auth patterns with secure token management.

Capabilities

  • Implement OAuth 2.0 flows (Authorization Code, Client Credentials, PKCE)
  • Generate API key authentication
  • Build JWT token handling
  • Create token refresh logic
  • Implement secure credential storage
  • Generate auth interceptors
  • Build multi-tenant authentication
  • Create session management
  • Implement auth error recovery
  • Generate auth testing utilities

Supported Authentication Types

OAuth 2.0

  • Authorization Code flow
  • Authorization Code with PKCE
  • Client Credentials flow
  • Implicit flow (legacy)
  • Resource Owner Password flow

Token-Based

  • Bearer tokens
  • API keys (header, query, cookie)
  • JWT (signing and verification)
  • Custom token formats

Traditional

  • Basic authentication
  • Digest authentication
  • Mutual TLS

Inputs

  • Authentication scheme from parsed schema
  • OAuth configuration (client ID, URLs, scopes)
  • Token storage preferences
  • Security requirements

Outputs

  • Authentication manager class
  • Token refresh logic
  • Credential storage utilities
  • Auth interceptor functions
  • PKCE helper functions
  • OAuth flow handlers

Process

  1. Analysis

    • Identify required auth type(s)
    • Determine token storage strategy
    • Plan refresh mechanism
    • Design error recovery
  2. Implementation

    • Generate auth manager class
    • Implement token acquisition
    • Build token refresh logic
    • Create credential storage
    • Add auth interceptors
  3. Security Hardening

    • Implement PKCE for OAuth
    • Add token encryption for storage
    • Create secure random generators
    • Implement token expiry checks
    • Add auth event logging
  4. Testing

    • Generate auth flow tests
    • Create token refresh tests
    • Build error scenario tests

Read the full file on GitHub · 376 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. 2d ago First seen · 376 lines · 34 tokens per session scan A f0aead8f3cf6

Subscribe to this mod's changes

auth-builder-agent is an agent published in the GitHub repository TheLobbi/claude (21 stars, last pushed yesterday), licensed MIT. It adds 34 tokens to every session and 2,170 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-05.

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