stripe__link-cli/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code when working with code in this repository.

Project Overview

Link CLI — lets agents get secure, one-time-use payment credentials from a Link wallet. pnpm + Turborepo monorepo:

• @stripe/link-sdk (packages/sdk): Typed Link API client and resource implementations. It accepts accessToken or getAccessToken; it does not own OAuth state. Entry: src/index.ts.
• @stripe/link-cli (packages/cli): Commander.js + Ink/React CLI that consumes @stripe/link-sdk. Entry: src/cli.tsx.

Commands

pnpm install                    # install dependencies
pnpm run build                  # build all packages (turbo)
pnpm run dev                    # watch mode
pnpm run test                   # run all tests
pnpm run typecheck              # type-check all packages
pnpm biome check .              # lint + format check (CI)
pnpm run check                  # lint + format with auto-fix

Run a single test:

cd packages/cli && pnpm vitest run src/utils/__tests__/line-item-parser.test.ts

The CLI integration tests in packages/cli/src/__tests__/cli.test.ts run against the compiled dist/cli.js. Run pnpm run build before running them if the source has changed.

Run the CLI locally:

node packages/cli/dist/cli.js <command>

Architecture

SDK Resources

Defined in packages/sdk/src/resources/interfaces.ts:

• ISpendRequestResource — CRUD + request-approval for spend requests

The SDK only accepts credentials. Device authorization, refresh-token persistence, login state, and auth-specific errors live under packages/cli/src/auth/.

CLI Command Structure

Commands in packages/cli/src/cli.tsx (incur framework). Each has two output modes:

• Interactive (default): Ink/React components from packages/cli/src/commands/
• JSON (--format json): JSON to stdout, errors as JSON with code and message fields with exit code 1

Commands: auth login|logout|status, user-info retrieve, spend-request create|update|retrieve|request-approval|cancel, payment-methods list, shipping-address list, mpp pay|decode, serve.

The CLI also runs as an MCP server (--mcp) and serves skill files via skills subcommand, both provided by incur.

When changing commands, flags, or schema descriptions, always update all four together: README.md, skills/create-payment-credential/SKILL.md, the schema description strings in the relevant schema.ts file, and CLAUDE.md. These can easily drift apart.

Input is passed via flags. Define options in the command's zod schema — incur registers CLI flags automatically from the schema.

auth login

• auth login --client-name <name> — optional flag to identify the agent or app; shown in the user's Link app as <name> on <hostname>. Defined in loginOptions in packages/cli/src/commands/auth/schema.ts.
• auth login --interval <seconds> [--timeout <seconds>] [--max-attempts <n>] — when --interval is provided, the command yields the verification code immediately then polls inline until authenticated or timed out. Without --interval, returns the code with a _next hint for separate polling via auth status.
• The token endpoint echoes scope and authorization_details back with the tokens on login/refresh. These are persisted in the credential file (part of AuthTokens) and surfaced on auth status in both interactive and JSON modes, only when present.
• packages/cli/src/auth/auth-resource.ts owns device authorization, token parsing, refresh, and revocation. ResourceFactory exposes the resulting access token to SDK resources through getAccessToken.

auth upgrade

• auth upgrade — takes the same flags as auth login (reuses loginOptions; --client-name, --scope, --source-actions, --authorization-detail, --interval/--timeout/--max-attempts) and starts a new device-authorization requesting a superset of the current access. Implemented alongside login in createAuthCli (packages/cli/src/commands/auth/index.tsx); auth login is unchanged. The device-auth tail (initiate → yield code → poll) is shared with login via the startDeviceAuthAndPoll helper.
• Where auth login bails out with "already logged in" when a valid session exists, auth upgrade never bails: it refreshes the existing token, merges the requested scope/authorization_details with the currently granted access via computeMergedAccess (packages/cli/src/auth/merge-access.ts, returning mergedScope + mergedAuthorizationDetails), and initiates device auth for the union.
• If the existing token is invalid or absent, it writes a warning to stderr and includes a warning field in the JSON yield, then continues with only the requested access (never hard-fails). --source-actions are folded into authorization_details before merging (via buildAuthorizationDetails), so source merges by type like any other detail.
• Deferred session replacement (key invariant). Upgrade does not clear or revoke the current session up front — the existing grant stays valid throughout the pending approval, so a failed initiateDeviceAuth or an abandoned approval leaves it usable. The refreshed tokens are persisted; the pending device-auth record is flagged replaces_existing_session (field on the CLI-owned PendingDeviceAuth in packages/cli/src/auth/storage.ts). pollAuthStatus completes a flagged pending even while isAuthenticated() is true (it doesn't report the old session as done), and on success swaps in the new tokens and revokes the old grant. The interactive path does the same via the <Login> revokeRefreshTokenOnSuccess prop. Abandon → the flagged pending expires (auto-cleared by getPendingDeviceAuth) and the old session remains.
• Scope-token comparison for the merge tolerates commas (the token endpoint echoes scope back comma-delimited) — but only inside merge-access.ts. auth login's --scope parsing (normalizeScopeInput in scopes.ts) remains strictly space-separated, so login is genuinely unchanged.

spend-request command

CLI command is spend-request (user-facing). Implemented in packages/cli/src/commands/spend-request/. SDK interfaces: ISpendRequestResource, CreateSpendRequestParams, UpdateSpendRequestParams. API endpoint: /spend_requests.

Key input field notes:

• CLI input uses payment_method_id; mapped to payment_details when calling the SDK
• --execution-method link_pay_token and --merchant-account-id acct_... are a create-only pair for Link Pay Token checkout. The agent reads the account ID from data-stripe-merchant-account in the AI-agent steering DOM before creating the request; Link resolves the canonical merchant identity. LPT uses credential_type: card, cannot use --test or --network-id, and must not accept agent-provided merchant name or URL. Never add the target fields to the update path.
• context requires min 100 characters; amount is in cents with max 500000
• --metadata (create only) is a repeatable key:value flag (CLI) or a { key: value } object (MCP/agent), merged into a single metadata string→string map. Max 50 keys, key ≤ 40 chars, value ≤ 500 chars. Reuses parseKvString from line-item-parser.ts.
• --test flag creates testmode credentials (real testmode SPT from test card data) instead of livemode ones
• create --request-approval and request-approval both show an approval URL in interactive mode and poll until approved/denied/expired/failed/canceled. In JSON mode (--format json), they return immediately with an _next.command for spend-request retrieve.
• retrieve --interval <seconds> polls until approved/denied/expired/succeeded/failed/canceled, or until requires_action with a non-auto_resume resolution (auto_resume is polled through transparently). If --timeout is reached or --max-attempts is exhausted while the request is still non-terminal, it exits non-zero with POLLING_TIMEOUT.
• Both create and retrieve (including --request-approval/request-approval polling and retrieve --interval polling) can return status: 'requires_action' with status_details.requires_action.next_action (type, display_message, action_url, resolution). resolution: 'auto_resume' (currently only next_action.type: 'three_d_secure') means polling continues transparently — the request resolves on its own. Any other resolution stops polling immediately; the caller must have the user complete the action, then create a new spend request.
• cancel <id> cancels a spend request. Can cancel from created, pending_approval, or approved states. Returns the spend request with status: "canceled".
• --approval-detail — optional JSON object (MCP/agent) or JSON string (CLI) with approval details for delegated flows. Required fields: approved_at (unix timestamp int), approval_method (click|programmatic|voice), app_name, external_user_id. Optional: ip_address, user_agent, device_type (mobile|web), agent_log_id, external_user_name, external_session_id, authentication_method (biometric_face|biometric_fingerprint|passkey). Sent as approval_details in the API request body.
• card credentials include billing_address (name, line1, line2, city, state, postal_code, country) and valid_until (ISO date string — when the card expires/stops working)
• --output-file <path> on retrieve or create writes full card credentials to a local file (0600 permissions) and redacts card data in stdout. --force allows overwriting an existing file.
• create also accepts an undocumented --expires-at <unix_seconds> to override the default 12-hour spend request expiration (3 hours to 7 days in the future). It's deliberately excluded from --schema/--llms-full output and from README/SKILL.md: it's gated to an allow-list of OAuth clients server-side, and most callers get a 400 ("expires_at is not supported for this client") if they try it — don't document or suggest it to general agents.

user-info retrieve

• user-info retrieve returns the existing identity fields and can include agent_wallet_spend_limits and agent_wallet_verification_requirement enrichment.
• Spend limits contain per-transaction, daily, and 30-day values. Finite values are cents because /userinfo does not return currency. A null limit or remaining amount explicitly means unlimited; used remains numeric.
• Either enrichment object can be omitted independently when enrichment is disabled or unavailable. Do not interpret omission as unlimited or as a default verification status.
• Verification status is one of not_required, ssn_verification, identity_verification, contact_support, or complete. action_url is nullable and directs the user to the required action when present. This is informational and does not change spend-request or requires_action handling.

mpp pay

• mpp pay <url> --context <ctx> [-X <method>] [-d <body>] [-H <header>]... [--amount <cents>] [--payment-method-id <id>] [--test] — handles the full MPP flow end-to-end: probes the URL for a 402 challenge, parses the www-authenticate header to extract network_id and amount, creates a spend request (credential_type: shared_payment_token), gets user approval, retrieves the SPT, and pays. Amount/currency are derived from the 402 challenge; --amount overrides. --context is required (min 100 chars) — describe the purchase and rationale. Default payment method is used unless --payment-method-id is specified.
• mpp pay <url> --spend-request-id <id> [--method <method>] [--data <body>] [--header <header>]... — backward-compat mode: uses a pre-approved spend request directly, skipping creation/approval.
• --header is repeatable and uses "Name: Value" format. Content-Type: application/json is auto-applied when --data is provided; user-provided headers take precedence.
• The SPT is one-time-use — a failed payment requires running mpp pay again (creates a new spend request).
• In agent mode the full flow yields _next.pay_argv ({ command: 'mpp', args: [...] }) alongside _next.pay_command. pay_argv is authoritative — it holds the raw values and is meant to be invoked without a shell. pay_command is the compatibility string and every dynamic part of it (url, method, body, each header, spend-request id) must go through shellQuote from packages/cli/src/utils/shell-quote.ts. See "Security: shell-quoting command strings".
• Implemented in packages/cli/src/commands/mpp/ — pay.tsx (logic), schema.ts (input/output schema), index.tsx (incur registration).

demo command

• demo [--only-card] [--only-spt] — Interactive demo of both payment flows. Always uses --test mode (no real charges). Shows a menu to choose: virtual card flow, SPT/machine payment flow, or both. --only-card and --only-spt skip the menu. Requires a TTY (no JSON output mode).

onboard command

• onboard — Guided setup: authenticates (skips if already logged in), checks payment methods (prompts to add one if missing, shows picker if multiple), shows app download QR code, then runs the full demo. Requires a TTY.

serve command

• serve [--port <n>] [--host <host>] — HTTP server that exposes the CLI's MCP endpoint. Implemented in packages/cli/src/commands/serve/index.ts. The handler forwards to rootCli.fetch() (incur), but is a privilege boundary: requireAuth only proves the CLI owner is authenticated, not that the HTTP caller is authorized.

Code Conventions

• ESM everywhere — "type": "module" in all package.json files
• Biome — 2-space indent, single quotes, organized imports
• tsup — ESM output; Node 20 target for the SDK and Node 18 target for the CLI
• Vitest — test files in __tests__/ directories adjacent to source
• TypeScript strict mode — tsconfig.base.json at root
• React 18 + Ink 5 for interactive rendering
• conf for local auth token storage

Global Flags

Flag	Effect
--auth <path>	Store auth credentials in a specific file instead of the default platform config location. auth login writes to this file; all other commands read from it. Parsed from process.argv and stripped before incur processes flags.

Security: Terminal Output Sanitization

Server-returned strings can contain ANSI escape sequences or control characters that spoof the terminal approval UI. Sanitization is handled automatically via sanitizeDeep() from packages/cli/src/utils/sanitize-text.ts:

• SDK-resource data — sanitized automatically at the sanitizeResource() proxy boundary in packages/cli/src/utils/resource-factory.ts. All server data flowing through SDK resources (spend-request, payment-methods, sources, etc.) is sanitizeDeep()'d before reaching components or the incur formatter, in every output format.
• Commands using useAsyncAction hook — sanitized automatically. The hook calls sanitizeDeep() on all returned data before it reaches components.
• Commands with manual state management (e.g. create.tsx, retrieve.tsx, request-approval.tsx, mpp/pay.tsx) — must call sanitizeDeep() on API responses before calling setRequest()/setState().
• Attacker-controlled data that does NOT flow through an SDK resource — must be sanitized at its own parse boundary. mpp pay sanitizes the HTTP response in readPayResult() (pay.tsx); mpp decode sanitizes the parsed WWW-Authenticate challenge in decodeStripeChallenge() (decode.ts). These bypass the resource factory, so the return value of the parse/fetch helper is the chokepoint — sanitizing there covers both the interactive Ink render and the agent (toon/yaml/md) output at once.

JSON output mode (--format json) is not affected — JSON.stringify encodes escape sequences as Unicode literals.

Security: Shell-Quoting Command Strings

Any string the CLI emits for an agent to run (instruction, _next.command, _next.pay_command) is a shell-injection sink. Agents commonly execute these through Bash, so interpolating an unquoted value there gives whoever controls that value command execution on the agent's host — even though the value was safe as an argv entry. Sanitization does not help: $(...), backticks and ; are ordinary printable characters.

Rules:

• Every dynamic value interpolated into a command string goes through shellQuote() from packages/cli/src/utils/shell-quote.ts, or the whole argv list through shellCommand(). This applies to server-issued IDs too — uniform treatment removes the "is this field trusted?" judgment call from future edits.
• Prefer emitting a structured continuation next to the string (_next.pay_argv = { command, args }) and point agents at it. A list of arguments has no seam to smuggle syntax through; a string always does.
• Naive '${value}' wrapping is not quoting — a single ' in the value closes it and escapes.
• Regression coverage lives in packages/cli/src/utils/__tests__/shell-quote.test.ts (bash round-trip) and the _next continuation quoting block in packages/cli/src/__tests__/cli.test.ts.

Environment Variables

Variable	Effect
LINK_AUTH_FILE	Same as --auth — override the auth credential file path (flag takes precedence)
LINK_ACCESS_TOKEN	Use this access token directly, bypassing auth storage
LINK_REFRESH_TOKEN	Refresh token to use when LINK_ACCESS_TOKEN is expired
LINK_NO_REFRESH	When set, never auto-refresh the access token — error instead
LINK_API_BASE_URL	Override API base URL
LINK_AUTH_BASE_URL	Override auth base URL
LINK_HTTP_PROXY	Route all SDK requests through an HTTP proxy (requires undici installed)