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/ooiyeefei/ccc/cross-app-shared-authnpx skills add ooiyeefei/ccc --skill cross-app-shared-authgit clone --depth 1 https://github.com/ooiyeefei/cccWrote 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.
[](https://agentmods.dev/skills/ooiyeefei/ccc/cross-app-shared-auth)<a href="https://agentmods.dev/skills/ooiyeefei/ccc/cross-app-shared-auth"><img src="https://agentmods.dev/badge/skills/ooiyeefei/ccc/cross-app-shared-auth.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00159 | $0.05199 |
| Opus 5 | $0.00079 | $0.02599 |
| Sonnet 5 | $0.00032 | $0.01040 |
| Haiku 4.5 | $0.00016 | $0.00520 |
Grade A, and why
cross-app-shared-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 5d 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.
How it starts
The opening of the file, as written. The whole thing — 149 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Cross-App Shared Auth
A repeatable blueprint for connecting a family of apps to one shared identity plus one central accounts database, so:
- a person has a single account across every app (sign in once, known everywhere),
- access to each app is granted per app, on demand, and accrues over time (not all-or-nothing),
- users can sign up from any app OR from a central landing page, and either path registers them centrally.
Use it two ways: to stand up the platform the first time, and to onboard each new app after that. When onboarding, follow the sequence in references/onboarding-checklist.md step by step.
The one idea to hold onto
Identity is shared. Entitlement is per app. These are two independent layers, and conflating them is the mistake that causes almost every problem in this space.
- Identity (who is this person): one shared auth provider issues one stable user id used by every app. Signing in on app A signs you in on app B too (SSO across subdomains). This does not grant access to app B.
- Entitlement (what may this person use): stored in a central accounts database keyed on that shared user id. Each app checks it. No record for this user and this app means no access (deny-by-default).
So "one login" and "you only get into the apps you have actually turned on" are not in tension. They are the intended combination.
Two slots, chosen independently:
| Slot | Job | Examples |
|---|---|---|
| Identity provider | issue one shared user id, handle sign in / sign up | Clerk, Supabase Auth, Auth0, Firebase Auth |
| Central accounts store | hold per-app access records, keyed on the shared user id | Convex, Postgres, MySQL, any DB |
The database vendor is free per app. The only hard rule: apps that share one identity must share one identity provider instance, so the user id is common and joins everything.
Read references/architecture.md for the full picture with a diagram.
Prerequisites (have these before onboarding any app)
What ships with it
5 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.
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.
- 5d ago First seen · 149 lines · 159 tokens per session scan A 04bdc2a1df10
cross-app-shared-auth is a skill published in the GitHub repository ooiyeefei/ccc (483 stars, last pushed 1mo ago), licensed MIT. It adds 159 tokens to every session and 5,199 once invoked, about $0.0008 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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