cmux Billing Agent Skill

Stripe checkout, pricing, subscription, Pro plan, webhook, and entitlement runbook for cmux billing work.

Context cost
2.9k tokensestimated from the bundle, loaded when it triggers
Bundle
1 file · 11.4 kBtext throughout, nothing executable
Licence
GPL-3.0the author’s own terms
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Stripe checkout, pricing, subscription, Pro plan, webhook, and entitlement runbook for cmux billing work. Use when editing or debugging billing, pricing, Stripe Checkout, subscription recording, Pro plan status, webhooks, entitlement metadata, or pricing dev/prod tooling.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

e-commercestripewebhook

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md11.4 kB · preview
--- name: cmux-billing ---
6# cmux Billing
7
8Read before changing billing, pricing, Stripe, Pro entitlement, checkout, webhook, or subscription code.
9
10## Architecture map
11
12- /api/billing/checkout creates Stripe Checkout Sessions for Pro when STRIPE_SECRET_KEY is set. It sets client_reference_id to the Stack user id, auto-creates an anonymous Stack user for signed-out buyers, and falls back to the legacy Stack purchase path when Stripe is unset or plan=team. The "already active" short-circuit lives here.
13- /api/billing/portal resolves the current Stack user, looks up their stripe_customers row, and creates a Stripe customer portal session returning to /pricing.
14- /api/billing/subscription cancels or resumes the active Stripe Pro subscription; /dashboard/billing renders localized in-dashboard plan state and self-serve actions.
15- web/services/billing/purchase.ts is the shared idempotent recorder used by /api/billing/complete and /api/stripe/webhook. It attaches email to the purchaser, records billing_email_claims on conflict, and never cross-grants based on an unverified email.
16- VM code reads the plan from Stack clientReadOnlyMetadata: a non-empty cmuxVmPlan (operator override) takes precedence, otherwise cmuxPlan (the Stripe mirror) supplies the entitlement. resolveProPlanStatus reports Pro for an active stripe_subscriptions row or a paid cmuxVmPlan override (pro, team, founders); billingManagement stays Stripe-only, so a granted account shows Pro without a portal link.
17- The staff-only /api/admin/* routes let admins (a verified cmux.com, manaflow.ai, or manaflow.com email, or a verified email with an active admin_members row) search users, teams, and emails and: grant or remove the user cmuxVmPlan override (/api/admin/users), grant or remove a team override of team (/api/admin/teams), grant Pro to an email with no account yet (/api/admin/email-grants, stored in admin_plan_grants and applied by the after-sign-in callback once the mailbox is verified), and downgrade a paying customer by cancelling the Stripe subscription at period end (/api/admin/subscriptions, same service as the self-serve form). services/admin/routeAuth.ts requireAdmin is the gate (domain check in services/admin/access.ts); members, audit, and pro-users routes manage admin invites, the audit log, and the Pro roster. services/admin/proGrants.ts writes under the account-mutation lease and records serverMetadata.cmuxAdminPlanGrant (who, when, which plan). Non-admins get 403 on the API; the admin UI is not part of this repository and there is no admin page on cmux.com. The admin_plan_grants migration is an operator step; until it runs, pending email grants report 503 and search omits them.
18- /api/stripe/webhook is signature-verified, insert-first idempotent through stripe_webhook_events, safe for foreign events in the shared Stripe account, and gates cmux handling on metadata.app === "cmux". Return 2xx only after durable writes; return 500 to make Stripe retry.
19
20## Dev workflow
21
22- Use web/scripts/stripe/dev-stack.sh.
23- Local bun dev accounts use the development Stack project and receive a
24 non-persistent Pro entitlement automatically. This applies only when
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md1,502 words
Files1
LicenceGPL-3.0
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈80
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
2,770
on trigger
The instruction body, read only when the skill fires.
1.4%
of a 200k window
Ten skills this size would take about 14% of the window before you open a file.
050k100k150k200k context window

2.9k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Middling. Fine to keep on in a project where you use it weekly, worth unloading in one where you never do.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

1 file, 11.4 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md11.4 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 1 file you can review in full before installing. The GPL-3.0 licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# cmux Billing · 2.9k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/cmux-billing/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/cmux-billing" ] && { [ ! -e .claude/skills/cmux-billing ] || { mv .claude/skills/cmux-billing "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/cmux-billing" .claude/skills/ && echo "Installed .claude/skills/cmux-billing"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add manaflow-ai/cmux-billing

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/cmux-billing/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/cmux-billing/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/cmux-billing" ] && { [ ! -e ~/.claude/skills/cmux-billing ] || { mv ~/.claude/skills/cmux-billing "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/cmux-billing" ~/.claude/skills/ && echo "Installed ~/.claude/skills/cmux-billing" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/cmux-billing/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referencemanaflow-ai/cmux-billing

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

Reviews

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Anybody with an account, one review each. It carries the version that was current when you wrote it, and the publisher may reply once.

Who wrote it

MA
manaflow-ai

Publishes on mcprush.

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