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.
npx agentmods add skills/fullstack-phoenix/saas_kit/authenticationnpx skills add fullstack-phoenix/saas_kit --skill authenticationgit clone --depth 1 https://github.com/fullstack-phoenix/saas_kitWhat 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 | $0.00043 | $0.01152 |
| Opus 5 | $0.00022 | $0.00576 |
| Sonnet 5 | $0.00009 | $0.00230 |
| Haiku 4.5 | $0.00004 | $0.00115 |
Grade A, and why
authentication 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 yesterday.
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.
How it starts
The opening of the file, as written. The whole thing — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.
User Authentication
Generates a complete authentication system on top of Phoenix's mix phx.gen.auth,
then extends the User schema with role-based access control (:user, :admin,
:superuser), profile fields (name, locale, timezone), an embedded data field,
and soft-delete/anonymization. This is the core foundation most other features
build on.
When to use
- The app needs users who can register, log in, and be authorized by role.
- You want admin/superuser bootstrapping out of the box (first signup becomes superuser; listed emails become admins).
- Don't reach for this if the app is single-tenant with no login — and install
it before
teams,oauth,payments, or anything that references users.
Dependencies
- Requires: None (this is a
corefeature,position4 — install early). - Recommended: None. Pair with
require_confirmed_uservia the install decision below if you want email confirmation gating.
Install
mix saaskit.feature.install authentication
The installer runs mix phx.gen.auth Users User users --live, then injects the
extra fields, changesets, and config. It asks one decision:
- Require email confirmation? (
email_confirmation) — when yes, installs therequire_confirmed_userfeature, which redirects authenticated-but-unconfirmed users to/users/confirm. OAuth sign-ins are auto-confirmed and skip the gate.
mix saaskit.feature.install authentication --decision email_confirmation=require_confirmed_user
What it generates
mix phx.gen.auth Users User users --livescaffolding — users table, auth logic, and LiveView sign-in/registration components.- Migration
priv/repo/migrations/*_add_additional_fields_to_users.exs— addsdeleted_at,role, name fields,locale,timezone, and embeddeddata. - Extends
lib/my_app/users/user.ex:roleenum (:user,:admin,:superuser), profile fields,embeds_one :data.maybe_set_admin_role/1— auto-assigns roles from config.update_changeset/2(profile-only, never email/password),data_changeset/2,anonymize_changeset/1.
- Extends
lib/my_app/users.exwithupdate_user/2,change_user/2,anonymize_user/1. - Adds tests in
test/my_app/users_test.exs.
What ships with it
1 file 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.
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.
- yesterday First seen · 122 lines · 43 tokens per session scan A 1ed7e60f72ce
authentication is a skill published in the GitHub repository fullstack-phoenix/saas_kit (2 stars, last pushed 2mo ago), licensed MIT. It adds 43 tokens to every session and 1,152 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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