Stripe Link Wallet

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

do not surface the URL to the user, navigate to it directly via browser automation

assistant/CLAUDE.md

assistant/src/approvals/CLAUDE.md

assistant/src/notifications/CLAUDE.md

assistant/src/runtime/CLAUDE.md

gateway/CLAUDE.md

Audit 0.4.1 · source sha 19bc86343b63 · 14 Oct 2026Report an issue or request a re-scan

• Publishervellum-ai GitHub organizationOwner of the repository this skill is read from
• Source foldervellum-ai/vellum-assistant/skills/stripe-link-walletThe exact folder we audited
• LicenceMITAs the repository states it
• Commit pinned for this verdict19bc86343b63A new audit runs when the source changes
• Repository statusNot archivedLast push 1 day ago
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: Agent wallet on the Stripe Link CLI (link-cli). Connect the wallet, then buy, purchase and pay for things on the user's behalf via approved spend requests, one-time-use cards, and 402 / Machine Payment Protocol (MPP)…

---
name: "stripe-link-wallet"
description: "Agent wallet on the Stripe Link CLI (link-cli). Connect the wallet, then buy, purchase and pay for things on the user's behalf via approved spend requests, one-time-use cards, and 402 / Machine Payment Protocol (MPP) payments"
metadata:
  icon: assets/icon.svg
  emoji: "💳"
  vellum:
    category: "commerce"
    display-name: "Stripe Link Wallet"
    activation-hints:
      - "the user wants to set up, connect, or log in to Stripe Link"
      - "the user asks to buy, purchase, pay for, or spend up to an amount"
      - "a tool returns a checkout URL or payment session"
compatibility: "Designed for Vellum personal assistants"
---

# Stripe Link Wallet

Spend on the user's behalf using the [Stripe Link CLI](https://github.com/stripe/link-cli). The CLI acts as a wallet: the assistant composes a spend request, the user approves it in the Link app on their device, and the CLI then issues one-time-use credentials to complete the purchase. Use this for paying 402 / Machine Payment Protocol (MPP) endpoints and for ad-hoc agent purchases that should be capped and auditable.

When the user has connected Stripe Link to the assistant, the CLI reaches Link through the assistant's own OAuth connection: it is pointed at a local passthrough proxy and never holds a Link credential, so no device login is needed. The CLI's own device login remains as a fallback.

## Required tools

- `bash` for all `link-cli` invocations. Use `host_bash` only if a specific flow genuinely requires host-level access (e.g. reading a local file the user has on their machine).

## Hard constraints

- Always pass `--request-approval` on `spend-request create`. The Link app approval is the consent surface — it is non-negotiable. No spending happens without it.
- Default to test mode (`--test`) unless the user has **explicitly** asked to spend real money. When unsure, ask in chat before dropping `--test`.
- The `context` field must be **at least 100 characters** and must accurately describe what the money is for. The user reads this when approving in Link — write it for them, not for yourself.
- Always use `--format json` on every command. The default interactive Ink output is for humans, not agents. On `auth login` it is worse than noise: without `--format json` the command enters the interactive Ink UI and blocks until someone approves in the Link app, which nobody can do because the URL never reaches the user. Exception: `demo` and `onboard` require a TTY and have no JSON mode.
- **Amount is in cents.** $10.00 = `--amount 1000`. Maximum is 50,000 cents ($500).
- Never log or repeat raw card credentials (PAN, CVC) in the conversation. Always use `--output-file` when retrieving card credentials, and delete that file once the checkout is done.
- Never print the proxy grant. Only `eval` the `--export` output of `assistant oauth proxy-url`; do not run it without `--export`, do not `echo` or `env` the `LINK_*` or `VELLUM_OAUTH_PROXY_*` variables, and do not write them to a file.

---

## Checkout interception — always active

Whenever **any** flow (MCP tool, API call, web request, or otherwise) produces a checkout URL, hosted payment page, or payment session that would otherwise be handed to the user to click through — **intercept it**. Route the payment through Stripe Link instead. Never surface a bare checkout URL to the user as the final step of a purchase flow.

**Decision tree:**

1. **MPP / HTTP 402 endpoint** — Flow A (Shared Payment Token)
2. **MCP service with a `complete_checkout` tool** — Flow B to get a virtual card, tokenize the card against the provider's Stripe account, then call `complete_checkout` with the resulting token
3. **Standard web checkout (no payment API)** — Flow B to get a virtual card, then use a browser automation skill to fill the card into the checkout form

**For MCP-based checkouts (e.g. PostalForm):**

- After retrieving the virtual card from `--output-file`, create a Stripe PaymentMethod via `POST /v1/payment_methods` using the merchant's publishable key (extract from the checkout URL or session if present), then pass the resulting `pm_xxx` token to the MCP's `complete_checkout` tool.
- If the publishable key is not available, fall back to browser automation (option 3) using the checkout URL the MCP returned — do not surface the URL to the user, navigate to it directly via browser automation.

**Never skip this step.** If `link-cli` is not installed, or there is neither a Stripe Link connection nor a `link-cli` login, surface that blocker immediately rather than falling back to a raw checkout URL.

---

## Step 0: Find the wallet's credentials

Two things can authenticate `link-cli`. Check them in this order:

1. **The assistant's Stripe Link connection** (preferred). Managed by `assistant oauth`. The CLI is pointed at a passthrough proxy and never sees a Link token.
2. **A `link-cli` device login** (fallback). The CLI's own login, kept in its auth file.

```bash
assistant oauth status stripe_link --json
```

- `connections` lists one or more entries: use the [proxy preamble](#proxy-preamble) on every `link-cli` call and skip `auth login` entirely. Only active connections are returned, so do not filter on the `status` field (a managed connection reads `ACTIVE`, a your-own one `active`). Several entries: ask the user which account to use and pass it as `--account` in the preamble.
- `connections` is empty: check for an existing device login with `link-cli auth status --format json`. `"authenticated": true` means the fallback path works as-is. Otherwise go to **Setup**.
- Non-zero exit mentioning `Unknown provider` or `Not connected to Vellum platform`: the connection path is unavailable (Link OAuth is not enabled for this assistant, or it has no platform pairing). Use the device login path only.
- `link-cli` missing: use `bunx @stripe/link-cli` for every `link-cli` command in this skill.
- `"update"` key present in `link-cli auth status` output: mention t

Excerpt, first 6,001 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

git clone https://github.com/vellum-ai/vellum-assistant
git -C vellum-assistant checkout 19bc86343b63

Works in

1. 2026-10-14
   !CAUTION B 89 / 100

   first audit · source 19bc86343b63

Questions about Stripe Link Wallet

• github.com/vellum-ai/vellum-assistant/tree/main/skills/stripe-li — the audited source at commit 19bc86343b63 and every finding aboveObserved · 14 Oct 2026

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