Guidance for adding user sign-in, access control, and account security with Better Auth, a TypeScript framework for authentication. It covers options such as passwords, third-party sign-in, two-factor authentication, and passkeys.

Use it to add email and password accounts, email verification, Google or GitHub sign-in, two-factor authentication, passkeys, and session handling.

It helps implement the parts of an application that verify users and control what they can access. It also brings several sign-in and account-protection methods into one framework.

better-auth — Skill for Claude Code and Codex by duongthinh03

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.

Any agent

npx skills add duongthinh03/portfolio --skill better-auth

Clone the repo

git clone --depth 1 https://github.com/duongthinh03/portfolio

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/duongthinh03/portfolio/better-auth.svg)](https://agentmods.dev/skills/duongthinh03/portfolio/better-auth)

Your own site

<a href="https://agentmods.dev/skills/duongthinh03/portfolio/better-auth"><img src="https://agentmods.dev/badge/skills/duongthinh03/portfolio/better-auth.svg" alt="Measured on agentmods" height="20"></a>

Per session 111 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,699 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin unknown 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.

Model	Per session	Once invoked
Fable 5.1	$0.00111	$0.01699
Opus 5	$0.00056	$0.00849
Sonnet 5	$0.00022	$0.00340
Haiku 4.5	$0.00011	$0.00170

Measured 8d ago against content hash bdf843e14e06, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

better-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 8d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/better_auth_init.py, scripts/tests/test_better_auth_init.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

.agents/skills/better-auth/SKILL.md · 205 lines

The source is not reproduced here

No licence file

Read it on GitHub

Files

What ships with it

9 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

8d ago First seen · 205 lines · 111 tokens per session scan A bdf843e14e06

Subscribe to this mod's changes

better-auth is a skill published in the GitHub repository duongthinh03/portfolio (85 stars, last pushed 2mo ago), with no licence file. It adds 111 tokens to every session and 1,699 once invoked, about $0.0006 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 2026-08-30.

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