blink

# Blink Skill

Bitcoin Lightning wallet operations via the Blink API. Enables agents to check balances, receive payments via invoices, send payments over Lightning, swap between BTC and USD wallets, track transactions, and monitor prices.

## What is Blink?

Blink is a custodial Bitcoin Lightning wallet with a GraphQL API. Key concepts:
- **API Key** — authentication token (format: `blink_...`) with scoped permissions (Read, Receive, Write)
- **BTC Wallet** — balance denominated in satoshis
- **USD Wallet** — balance denominated in cents (stablecoin pegged to USD)
- **Lightning Invoice** — BOLT-11 payment request string (`lnbc...`) used to receive payments
- **Lightning Address** — human-readable address (`user@domain`) for sending payments without an invoice
- **LNURL** — protocol for interacting with Lightning services via encoded URLs

## Environment

- Requires `bash` and Node.js 18+.
- Requires `BLINK_API_KEY` environment variable with appropriate scopes.
- For WebSocket subscriptions: Node 22+ (native) or Node 20+ with `--experimental-websocket`.
- Zero runtime npm dependencies. Only Node.js built-in modules are used (`node:util`, `node:fs`, `node:path`, `node:child_process`).

Use this skill for concrete wallet operations, not generic Lightning theory.

## Getting Started

### 1. Get your API key

1. Create a free account at [dashboard.blink.sv](https://dashboard.blink.sv).
2. Go to **API Keys** and create a key with the scopes you need.
3. Set it in your environment:

```bash
export BLINK_API_KEY="blink_..."
```

**API Key Scopes:**
- **Read** — query balances, transaction history, price, account info
- **Receive** — create invoices
- **Write** — send payments (use with caution)

> **Tip:** Start with Read + Receive only. Add Write when you need to send payments.

### 2. Verify it works

```bash
node {baseDir}/scripts/balance.js
```

If you see JSON with your wallet balances, you're ready.

### 3. Staging / Testnet (recommended for first-time setup)

To use the Blink staging environment (signet) instead of real money:
```bash
export BLINK_API_URL="https://api.staging.blink.sv/graphql"
```

Create a staging API key at [dashboard.staging.blink.sv](https://dashboard.staging.blink.sv). The staging environment uses signet bitcoin (no real value) — perfect for testing payment flows safely.

If `BLINK_API_URL` is not set, production (`https://api.blink.sv/graphql`) is used by default.

### API key auto-detection

Scripts automatically resolve `BLINK_API_KEY` using this order:
1. `process.env.BLINK_API_KEY` (checked first)
2. Shell rc files: `~/.profile`, `~/.bashrc`, `~/.bash_profile`, `~/.zshrc` — scanned for an `export BLINK_API_KEY=...` line only

No `source ~/.profile` prefix is needed. The rc file scan uses a targeted regex that reads only the `BLINK_API_KEY` export line — no other data is extracted from these files.

## Agent Safety Policy

These rules are mandatory for any AI agent using this skill:

1. **Ask before spending.** Never execute `pay_invoice.js`, `pay_lnaddress.js`, `pay_lnurl.js`, or `swap_execute.js` without explicit user confirmation of the amount and recipient.
2. **Dry-run first.** For swaps, always run with `--dry-run` before executing for real unless the user explicitly says to skip it.
3. **Check balance before sending.** Always run `balance.js` before any payment or swap to verify sufficient funds.
4. **Probe fees before paying.** Run `fee_probe.js` before `pay_invoice.js` to show the user the fee cost.
5. **Use minimum scopes.** Only request Write-scoped API keys when send operations are actually needed.
6. **Never log or display the API key.** Treat `BLINK_API_KEY` as a secret. Do not echo it, include it in messages, or write it to files.
7. **Prefer staging for testing.** When the user is testing or learning, suggest setting `BLINK_API_URL` to the staging endpoint.
8. **Respect irreversibility.** Warn the user that Lightning payments and swaps cannot be reversed once executed.

## Bitcoin Units

- **BTC wallet** amounts are always in **satoshis** (sats). 1 BTC = 100,000,000 sats.
- **USD wallet** amounts are always in **cents**. $1.00 = 100 cents.
- When displaying amounts to users, use the formatted fields from output JSON (e.g. `btcBalanceUsdFormatted`, `usdBalanceFormatted`).
- Do not perform manual BTC-to-USD conversion math — use `node {baseDir}/scripts/price.js <sats>` or the `btcBalanceUsd` field from `balance` output instead.
- For swap amounts, the `--unit` flag controls interpretation: `sats` for BTC, `cents` for USD.

## Workflow

1. Pick the operation path first:
- Receive payments (invoice creation, QR codes, payment monitoring).
- Send payments (invoice pay, Lightning Address, LNURL, BTC or USD wallet).
- Swap between wallets (BTC <-> USD internal conversion).
- Read-only queries (balance, transactions, price, account info).

2. Configure API access from [blink-api-and-auth](references/blink-api-and-auth.md):
- Set `BLINK_API_KEY` with the correct scopes for your operation.
- Optionally set `BLINK_API_URL` for staging/testnet.
- Verify connectivity with `balance.js`.

3. For sending payments, follow [payment-operations](references/payment-operations.md):
- Check balance before sending.
- Probe fees with `fee_probe.js`.
- Choose BTC or USD wallet with `--wallet` flag.
- Use `--dry-run` to preview without sending. Use `--max-amount` to cap outgoing amounts.
- Execute payment and verify in transaction history.

4. For swapping between wallets, follow [swap-operations](references/swap-operations.md):
- Get a quote with `swap_quote.js` to preview the conversion.
- Execute with `swap_execute.js` (use `--dry-run` first).

5. For receiving payments, follow [invoice-lifecycle](references/invoice-lifecycle.md):
- Create BTC or USD invoice.
- Parse two-phase output (invoice created, then payment resolution).
- Generate QR code and send to payer.
- Monitor via auto-subscribe, polling, or standalone subscription.

6. Apply safety constraints:
- Use minimum API key scopes for the task.
- Test on staging before production.
- Always check balance before sending.
- Use `--dry-run` on payment and swap commands to preview before executing.
- Use `--max-amount <sats>` to enforce a per-payment ceiling (pay_lnaddress, pay_lnurl).
- Use `--force` to override balance-check failures when you know the payment should proceed.
- Payments are irreversible once settled.

## Quick Commands

```bash
# Check balances
node {baseDir}/scripts/balance.js

# Create BTC invoice (auto-subscribes to payment)
node {baseDir}/scripts/create_invoice.js 1000 "Payment for service"

# Pay a Lightning invoice
node {baseDir}/scripts/pay_invoice.js lnbc1000n1...

# Pay from USD wallet
node {baseDir}/scripts/pay_invoice.js lnbc1000n1... --wallet USD

# Get current BTC/USD price
node {baseDir}/scripts/price.js

# Quote BTC -> USD internal swap (dry-run)
node {baseDir}/scripts/swap_quote.js btc-to-usd 5000

# Execute USD -> BTC internal swap
node {baseDir}/scripts/swap_execute.js usd-to-btc 500 --unit cents
```

## Core Commands

### Check Wallet Balances
```bash
node {baseDir}/scripts/balance.js
```

Returns JSON with all wallet balances (BTC in sats, USD in cents), wallet IDs, pending incoming amounts, and a **pre-computed USD estimate** for the BTC wallet. Use `btcBalanceUsd` for the BTC wallet's USD value — do not calculate it yourself.

### Create Lightning Invoice (BTC)
```bash
node {baseDir}/scripts/create_invoice.js <amount_sats> [--timeout <seconds>] [--no-subscribe] [memo...]
```

Generates a BOLT-11 Lightning invoice for the specified amount in satoshis. Returns the `paymentRequest` string that can be paid by any Lightning wallet. The BTC wallet ID is resolved automatically.

**Auto-subscribe**: After creating the invoice, the script automatically opens a WebSocket subscription and waits for payment. It outputs **two JSON objects** to stdout:
1. **Immediately** — `{"event": "invoice_created", ...}` with `paymentRequest`, `paymentHash`, etc.
2. **When resolved** — `{"event": "subscription_result", "status": "PAID"|"EXPIRED"|"TIMEOUT", ...}`

The agent should read the first JSON to share the invoice/QR with the user right away, then wait for the second JSON to confirm payment.

- `amount_sats` — amount in satoshis (required)
- `--timeout <seconds>` — subscription timeout (default: 300). Use 0 for no timeout.
- `--no-subscribe` — skip WebSocket auto-subscribe, just create the invoice and exit
- `memo...` — optional description attached to the invoice (remaining args joined)

### Create Lightning Invoice (USD)
```bash
node {baseDir}/scripts/create_invoice_usd.js <amount_cents> [--timeout <seconds>] [--no-subscribe] [memo...]
```

Creates a Lightning invoice denominated in USD cents. The sender pays in BTC/Lightning, but the received amount is locked to a USD value at the current exchange rate. Credited to the USD wallet. **Expires in ~5 minutes** due to exchange rate lock.

**Auto-subscribe**: Same two-phase output as `create_invoice.js` — first JSON is the created invoice, second JSON is the payment resolution (PAID/EXPIRED/TIMEOUT).

- `amount_cents` — amount in USD cents, e.g. 100 = $1.00 (required)
- `--timeout <seconds>` — subscription timeout (default: 300). Use 0 for no timeout.
- `--no-subscribe` — skip WebSocket auto-subscribe, just create the invoice and exit
- `memo...` — optional description attached to the invoice (remaining args joined)

### Check Invoice Status
```bash
node {baseDir}/scripts/check_invoice.js <payment_hash>
```

Checks the payment status of a Lightning invoice by its payment hash. Use after creating an invoice to detect when it has been paid. Returns status: `PAID`, `PENDING`, or `EXPIRED`.

- `payment_hash` — the 64-char hex payment hash from `create_invoice.js` output (required)

### Pay Lightning Invoice
```bash
node {baseDir}/scripts/pay_invoice.js <bolt11_invoice> [--wallet BTC|USD] [--dry-run] [--force]
```

Pays a BOLT-11 Lightning invoice from the BTC or USD wallet. Returns payment status: `SUCCESS`, `PENDING`, `FAILURE`, or `ALREADY_PAID`. The wallet ID is resolved automatically.

- `bolt11_invoice` — the BOLT-11 payment request string, e.g. `lnbc...` (required)
- `--wallet BTC|USD` — wallet to pay from (default: BTC). When USD is selected, the Blink API debits the USD equivalent from the USD wallet.
- `--dry-run` — preview the payment without sending (returns wallet info and invoice details)
- `--force` — attempt payment even when the wallet balance appears insufficient

**Requires Write scope on the API key.**

> **AGENT:** This command spends funds. Always run `balance.js` and `fee_probe.js` first, then confirm amount and recipient with the user before executing.

### Pay to Lightning Address
```bash
node {baseDir}/scripts/pay_lnaddress.js <lightning_address> <amount_sats> [--wallet BTC|USD] [--dry-run] [--force] [--max-amount <sats>]
```

Sends satoshis to a Lightning Address (e.g. `user@blink.sv`). Returns payment status. The wallet ID is resolved automatically.

- `lightning_address` — recipient in `user@domain` format (required)
- `amount_sats` — amount in satoshis (required)
- `--wallet BTC|USD` — wallet to pay from (default: BTC). When USD is selected, the amount is still specified in satoshis; the Blink API debits the USD equivalent from the USD wallet automatically.
- `--dry-run` — preview the payment without sending (returns wallet info and amount details)
- `--force` — attempt payment even when the wallet balance appears insufficient
- `--max-amount <sats>` — reject the payment if the amount exceeds this ceiling (in satoshis)

**Requires Write scope on the API key.**

> **AGENT:** This command spends funds. Always run `balance.js` first, confirm the Lightning Address and amount with the user, then execute.

### Pay to LNURL
```bash
node {baseDir}/scripts/pay_lnurl.js <lnurl> <amount_sats> [--wallet BTC|USD] [--dry-run] [--force] [--max-amount <sats>]
```

Sends satoshis to a raw LNURL payRequest string. For Lightning Addresses (`user@domain`), use `pay_lnaddress.js` instead.

- `lnurl` — LNURL string, e.g. `lnurl1...` (required)
- `amount_sats` — amount in satoshis (required)
- `--wallet BTC|USD` — wallet to pay from (default: BTC). When USD is selected, the amount is still specified in satoshis; the Blink API debits the USD equivalent from the USD wallet automatically.
- `--dry-run` — preview the payment without sending (returns wallet info and amount details)
- `--force` — attempt payment even when the wallet balance appears insufficient
- `--max-amount <sats>` — reject the payment if the amount exceeds this ceiling (in satoshis)

**Requires Write scope on the API key.**

> **AGENT:** This command spends funds. Always run `balance.js` first, confirm the LNURL and amount with the user, then execute.

### Estimate Payment Fee
```bash
node {baseDir}/scripts/fee_probe.js <bolt11_invoice> [--wallet BTC|USD]
```

Estimates the fee for paying a Lightning invoice without actually sending. Use before `pay_invoice.js` to check costs. Payments to other Blink users and direct-channel nodes are free (0 sats).

- `bolt11_invoice` — the BOLT-11 payment request string (required)
- `--wallet BTC|USD` — wallet to probe from (default: BTC). When USD is selected, uses `lnUsdInvoiceFeeProbe` to estimate fees from the USD wallet's perspective.

### Render Invoice QR Code
```bash
node {baseDir}/scripts/qr_invoice.js <bolt11_invoice>
```

Renders a terminal QR code for a Lightning invoice (BOLT-11) to stderr and generates a **PNG image file** to `/tmp`. The stdout JSON includes a `pngPath` field with the absolute path to the PNG file.

**Sending the QR image to a user**: After running this script, use the `pngPath` from the JSON output to send the PNG as a media attachment to the user in the current chat. The agent should use its native message-send capability with the file path.

- `bolt11_invoice` — the BOLT-11 payment request string (required)

Output JSON includes:
- `invoice` — uppercased invoice string
- `qrRendered` — always `true`
- `qrSize` — QR module count
- `errorCorrection` — `"L"` (LOW)
- `pngPath` — absolute path to the generated PNG file (e.g. `/tmp/blink_qr_1234567890.png`)
- `pngBytes` — file size in bytes

### List Transactions
```bash
node {baseDir}/scripts/transactions.js [--first N] [--after CURSOR] [--wallet BTC|USD]
```

Lists recent transactions (incoming and outgoing) with pagination. Returns direction, amount, status, type (lightning/onchain/intraledger), and metadata.

- `--first N` — number of transactions to return (default: 20, max: 100)
- `--after CURSOR` — pagination cursor from previous response's `endCursor`
- `--wallet BTC|USD` — filter to a specific wallet currency

### Get BTC/USD Price
```bash
node {baseDir}/scripts/price.js [amount_sats]
node {baseDir}/scripts/price.js --usd <amount_usd>
node {baseDir}/scripts/price.js --history <range>
node {baseDir}/scripts/price.js --currencies
```

Multi-purpose exchange rate tool. All price queries are **public (no API key required)**, though the key is sent if available.

**Modes:**
- **No args** — current BTC/USD price and sats-per-dollar rate
- **`<amount_sats>`** — convert a satoshi amount to USD (e.g. `price.js 1760` → `$1.20`)
- **`--usd <amount>`** — convert a USD amount to sats (e.g. `price.js --usd 5.00` → `7350 sats`)
- **`--history <range>`** — historical BTC price data with summary stats (high/low/change). Ranges: `ONE_DAY`, `ONE_WEEK`, `ONE_MONTH`, `ONE_YEAR`, `FIVE_YEARS`
- **`--currencies`** — list all supported display currencies (IDs, names, symbols, flags)

### Account Info
```bash
node {baseDir}/scripts/account_info.js
```

Shows account level, spending limits (withdrawal, internal send, convert), default wallet, and wallet summary with **pre-computed USD estimates** for BTC balances. Limits are denominated in USD cents with a rolling 24-hour window.

### Quote Internal BTC <-> USD Swap
```bash
node {baseDir}/scripts/swap_quote.js <direction> <amount> [--unit sats|cents] [--ttl-seconds N] [--immediate]
```

Builds a deterministic quote-like receipt for internal wallet conversion.

- `direction` — `btc-to-usd` or `usd-to-btc`
- `amount` — positive integer amount (unit inferred by direction unless `--unit` is set)
- `--unit sats|cents` — optional override for input unit
- `--ttl-seconds N` — quote validity window in seconds (default: 60)
- `--immediate` — mark intent for immediate execution mode in quote receipt

Uses Blink's conversion estimation path for pricing and records:
- pre-swap balances
- quote id / expiry metadata
- amount in/out terms
- execution path (`intraLedgerPaymentSend` or `intraLedgerUsdPaymentSend`)

### Execute Internal BTC <-> USD Swap
```bash
node {baseDir}/scripts/swap_execute.js <direction> <amount> [--unit sats|cents] [--ttl-seconds N] [--immediate] [--dry-run] [--memo "text"]
```

Executes a wallet-native internal conversion between your BTC and USD wallets.

- `--dry-run` — returns an execution receipt without performing the mutation
- `--memo "text"` — optional memo attached to the internal transfer

Execution receipts include quote terms, pre/post balances, balance deltas, and final status.

Fee/settlement interpretation:
- `quote.feeSats`, `quote.feeBps`, and `quote.slippageBps` are currently returned as zero in live runs.
- You can still see a small quote-to-settlement spread (often 1 sat or 1 cent) due to integer rounding between sats and cents.
- Always compute effective cost from `quote.amountOut` versus `balanceDelta` instead of relying only on explicit fee fields.

For deeper behavior details and formulas, see [swap-operations](references/swap-operations.md).

> **AGENT:** This command moves funds between wallets. Always run with `--dry-run` first, show the quote to the user, and get explicit confirmation before executing without `--dry-run`.

## Realtime Subscriptions

Blink supports GraphQL subscriptions over WebSocket using the `graphql-transport-ws` protocol. Node 20 requires the `--experimental-websocket` flag.

### Subscribe to Invoice Payment Status
```bash
node --experimental-websocket {baseDir}/scripts/subscribe_invoice.js <bolt11_invoice> [--timeout <seconds>]
```

Watches a single invoice and exits when it is **PAID** or **EXPIRED**. Status updates are printed to stderr. JSON result is printed to stdout.

### Subscribe to Account Updates (myUpdates)
```bash
node --experimental-websocket {baseDir}/scripts/subscribe_updates.js [--timeout <seconds>] [--max <count>]
```

Streams account updates in real time. Each event is output as a JSON line (NDJSON) to stdout. Use `--max` to stop after N events.

## API Reference

| Operation | GraphQL | Scope Required |
|-----------|---------|----------------|
| Check balance | `query me` + `currencyConversionEstimation` | Read |
| Create BTC invoice | `mutation lnInvoiceCreate` | Receive |
| Create USD invoice | `mutation lnUsdInvoiceCreate` | Receive |
| Check invoice | `query invoiceByPaymentHash` | Read |
| Pay invoice | `mutation lnInvoicePaymentSend` | Write |
| Pay LN address | `mutation lnAddressPaymentSend` | Write |
| Pay LNURL | `mutation lnurlPaymentSend` | Write |
| Fee estimate (BTC) | `mutation lnInvoiceFeeProbe` | Read |
| Fee estimate (USD) | `mutation lnUsdInvoiceFeeProbe` | Read |
| Transactions | `query transactions` | Read |
| Price / convert | `query currencyConversionEstimation` | **None (public)** |
| Price history | `query btcPriceList` | **None (public)** |
| Currency list | `query currencyList` | **None (public)** |
| Realtime price | `query realtimePrice` | **None (public)** |
| Account info | `query me` + `currencyConversionEstimation` | Read |
| Swap quote (BTC <-> USD) | `query currencyConversionEstimation` | Read |
| Swap execute BTC -> USD | `mutation intraLedgerPaymentSend` | Write |
| Swap execute USD -> BTC | `mutation intraLedgerUsdPaymentSend` | Write |
| Subscribe invoice | `subscription lnInvoicePaymentStatus` | Read |
| Subscribe updates | `subscription myUpdates` | Read |

**API Endpoint:** `https://api.blink.sv/graphql` (production)
**Authentication:** `X-API-KEY` header

**USD wallet notes:** The `lnInvoicePaymentSend`, `lnAddressPaymentSend`, and `lnurlPaymentSend` mutations all accept either a BTC or USD wallet ID. When a USD wallet ID is provided, the API debits the USD equivalent automatically. Amounts for `lnAddressPaymentSend` and `lnurlPaymentSend` are always specified in satoshis regardless of wallet type.

## Output Format

All scripts output structured JSON to stdout. Status messages and errors go to stderr. Exit code 0 on success, 1 on failure.

### Balance output example
```json
{
  "wallets": [
    { "id": "abc123", "currency": "BTC", "balance": 1760, "unit": "sats" },
    { "id": "def456", "currency": "USD", "balance": 1500, "unit": "cents" }
  ],
  "btcWalletId": "abc123",
  "btcBalance": 1760,
  "btcBalanceSats": 1760,
  "btcBalanceUsd": 1.2,
  "btcBalanceUsdFormatted": "$1.20",
  "usdWalletId": "def456",
  "usdBalance": 1500,
  "usdBalanceCents": 1500,
  "usdBalanceFormatted": "$15.00"
}
```

### Invoice creation output example (two-phase)
First JSON (immediate):
```json
{
  "event": "invoice_created",
  "paymentRequest": "lnbc500n1...",
  "paymentHash": "abc123...",
  "satoshis": 500,
  "status": "PENDING",
  "createdAt": "2026-02-23T00:00:00Z",
  "walletId": "abc123"
}
```
Second JSON (when payment resolves):
```json
{
  "event": "subscription_result",
  "paymentRequest": "lnbc500n1...",
  "status": "PAID",
  "isPaid": true,
  "isExpired": false,
  "isPending": false
}
```

### Invoice status output example
```json
{
  "paymentHash": "abc123...",
  "paymentStatus": "PAID",
  "satoshis": 500,
  "isPaid": true,
  "isExpired": false,
  "isPending": false
}
```

### Payment output example (BTC wallet)
```json
{
  "status": "SUCCESS",
  "walletId": "abc123",
  "walletCurrency": "BTC",
  "balanceBefore": 50000
}
```

### Payment output example (USD wallet)
```json
{
  "status": "SUCCESS",
  "walletId": "def456",
  "walletCurrency": "USD",
  "balanceBefore": 1500,
  "balanceBeforeFormatted": "$15.00"
}
```

### Price output example
```json
{
  "btcPriceUsd": 68036.95,
  "satsPerDollar": 1470,
  "conversion": {
    "sats": 1760,
    "usd": 1.2,
    "usdFormatted": "$1.20"
  }
}
```

### USD-to-sats conversion output example
```json
{
  "btcPriceUsd": 68036.95,
  "satsPerDollar": 1470,
  "conversion": {
    "usd": 5.0,
    "usdFormatted": "$5.00",
    "sats": 7350
  }
}
```

### Price history output example
```json
{
  "range": "ONE_DAY",
  "dataPoints": 24,
  "summary": {
    "current": 68036.95,
    "oldest": 67500.00,
    "high": 68500.00,
    "low": 67200.00,
    "changeUsd": 536.95,
    "changePct": 0.8
  },
  "prices": [
    { "timestamp": 1740000000, "date": "2025-02-20T00:00:00.000Z", "btcPriceUsd": 67500.00 }
  ]
}
```

### Transaction list output example
```json
{
  "transactions": [
    {
      "id": "tx_123",
      "direction": "RECEIVE",
      "status": "SUCCESS",
      "amount": 1000,
      "currency": "BTC",
      "type": "lightning",
      "paymentHash": "abc...",
      "createdAt": 1740000000
    }
  ],
  "count": 1,
  "pageInfo": {
    "hasNextPage": false,
    "endCursor": "cursor_abc"
  }
}
```

### Swap quote output example
```json
{
  "event": "swap_quote",
  "dryRun": true,
  "direction": "BTC_TO_USD",
  "preBalance": {
    "btcWalletId": "btc_wallet_id",
    "usdWalletId": "usd_wallet_id",
    "btcBalanceSats": 250000,
    "usdBalanceCents": 150000
  },
  "quote": {
    "quoteId": "blink-swap-1740000000-424242",
    "amountIn": { "value": 5000, "unit": "sats" },
    "amountOut": { "value": 340, "unit": "cents" },
    "expiresAtEpochSeconds": 1740000060,
    "immediateExecution": false,
    "executionPath": "blink:intraLedgerPaymentSend"
  }
}
```

### Swap execution output example
```json
{
  "event": "swap_execution",
  "dryRun": false,
  "direction": "USD_TO_BTC",
  "status": "SUCCESS",
  "succeeded": true,
  "preBalance": {
    "btcBalanceSats": 250000,
    "usdBalanceCents": 150000
  },
  "postBalance": {
    "btcBalanceSats": 253650,
    "usdBalanceCents": 149500
  },
  "balanceDelta": {
    "btcDeltaSats": 3650,
    "usdDeltaCents": -500
  },
  "quote": {
    "quoteId": "blink-swap-1740000015-556677",
    "executionPath": "blink:intraLedgerUsdPaymentSend"
  },
  "execution": {
    "path": "blink:intraLedgerUsdPaymentSend",
    "transactionId": "tx_abc123"
  }
}
```

## Typical Agent Workflows

### Receive a payment (recommended — auto-subscribe + QR image)
```bash
# 1. Create invoice — script auto-subscribes and outputs two JSON objects
node {baseDir}/scripts/create_invoice.js 1000 "Payment for service"
# → First JSON: {"event": "invoice_created", "paymentRequest": "lnbc...", ...}
# → Read paymentRequest from first JSON immediately

# 2. Generate QR code PNG
node {baseDir}/scripts/qr_invoice.js <paymentRequest>
# → JSON includes "pngPath": "/tmp/blink_qr_123456.png"
# → Send the PNG file to the user as a media attachment in the current chat

# 3. The create_invoice.js script is still running, waiting for payment
# → Second JSON: {"event": "subscription_result", "status": "PAID", ...}
# → When PAID: notify the user that payment has been received
# → When EXPIRED: notify the user the invoice expired
```

**Important**: The `create_invoice.js` script outputs two JSON objects separated by a newline. Parse them as separate JSON objects, not as a single JSON array. The first object arrives immediately; the second arrives when payment status resolves.

### Receive a payment (polling fallback)
```bash
# 1. Create invoice without auto-subscribe
node {baseDir}/scripts/create_invoice.js 1000 --no-subscribe "Payment for service"
# 2. Give the paymentRequest to the payer
# 3. Poll for payment
node {baseDir}/scripts/check_invoice.js <payment_hash>
# 4. Verify balance
node {baseDir}/scripts/balance.js
```

### Receive a USD payment
```bash
# Same two-phase pattern as BTC, but using create_invoice_usd.js
# Note: USD invoices expire in ~5 minutes
node {baseDir}/scripts/create_invoice_usd.js 500 "Five dollars for service"
# → First JSON: {"event": "invoice_created", "amountCents": 500, "amountUsd": "$5.00", ...}
# Generate QR and send to user, then wait for second JSON
```

### Send a payment (with fee check)
```bash
# 1. Check current balance
node {baseDir}/scripts/balance.js
# 2. Estimate fee
node {baseDir}/scripts/fee_probe.js lnbc1000n1...
# 3. Send payment
node {baseDir}/scripts/pay_invoice.js lnbc1000n1...
# 4. Verify in transaction history
node {baseDir}/scripts/transactions.js --first 1
```

### Send from the USD wallet
```bash
# Pay an invoice from the USD wallet
node {baseDir}/scripts/fee_probe.js lnbc1000n1... --wallet USD
node {baseDir}/scripts/pay_invoice.js lnbc1000n1... --wallet USD

# Send to a Lightning Address from the USD wallet
node {baseDir}/scripts/pay_lnaddress.js user@blink.sv 1000 --wallet USD

# Send via LNURL from the USD wallet
node {baseDir}/scripts/pay_lnurl.js lnurl1... 1000 --wallet USD

# Note: for lnaddress and lnurl, the amount is always in satoshis.
# The Blink API debits the USD equivalent from the USD wallet automatically.
```

### Convert sats to USD value
```bash
# Check how much 1760 sats is worth in USD
node {baseDir}/scripts/price.js 1760
# → $1.20
```

### Convert USD to sats
```bash
# How many sats is $5.00?
node {baseDir}/scripts/price.js --usd 5.00
# → 7350 sats
```

### Swap BTC to USD (quote then execute)
```bash
# 1. Build quote and inspect terms
node {baseDir}/scripts/swap_quote.js btc-to-usd 10000

# 2. Execute the swap
node {baseDir}/scripts/swap_execute.js btc-to-usd 10000
```

### Swap USD to BTC (dry-run then execute)
```bash
# 1. Dry-run execution receipt without moving funds
node {baseDir}/scripts/swap_execute.js usd-to-btc 500 --unit cents --dry-run

# 2. Real execution
node {baseDir}/scripts/swap_execute.js usd-to-btc 500 --unit cents
```

### Check price history
```bash
# Get BTC price over the last 24 hours
node {baseDir}/scripts/price.js --history ONE_DAY
# Get BTC price over the last month
node {baseDir}/scripts/price.js --history ONE_MONTH
```

## Security

### API Key Handling

- **Your API key is your wallet access** — anyone with a Write-scoped key can spend your entire balance.
- **Use minimum scopes** — Read-only for balance checks, Receive for invoices, Write only when sending.
- **Never expose keys in output** — do not echo, log, or include `BLINK_API_KEY` in chat messages or files.
- Keys are for server-side / agent use only. Never embed in client-side code.

### What Data Leaves the Machine

- **Outbound HTTPS** to `api.blink.sv` (or `BLINK_API_URL` override) for all GraphQL queries and mutations.
- **Outbound WSS** to `ws.blink.sv` (or `BLINK_WS_URL` override) for subscription WebSockets.
- **No other network calls.** Scripts do not phone home, send telemetry, or contact any third-party services.

### Filesystem Access

- **RC file reading:** If `BLINK_API_KEY` is not found in `process.env`, the client scans `~/.profile`, `~/.bashrc`, `~/.bash_profile`, and `~/.zshrc` for a line matching `export BLINK_API_KEY=...`. Only the value of that specific export is extracted — no other data is read from these files. The environment variable is always checked first.
- **QR PNG generation:** The `qr` command writes temporary PNG files to `/tmp/blink_qr_*.png`. These are standard image files with no embedded metadata beyond the QR content.
- **No other filesystem writes.** Scripts do not create config files, databases, or caches.

### Stateless Design

This skill stores no data between runs. There are no databases, config files, session tokens, or caches. Each script invocation is independent — it reads the API key, makes API calls, outputs JSON, and exits.

### Payment Safety

- **Sending is irreversible** — Lightning payments cannot be reversed once settled.
- **Test on staging first** — use `BLINK_API_URL=https://api.staging.blink.sv/graphql` to point at the signet staging environment with test funds.
- **USD invoices expire fast** — ~5 minutes due to exchange rate lock.
- **Price queries are public** — `price.js` works without an API key; only wallet operations require authentication.

## Reference Files

- [blink-api-and-auth](references/blink-api-and-auth.md): API endpoints, authentication, scopes, staging/testnet configuration, and error handling.
- [payment-operations](references/payment-operations.md): send workflows, BTC vs USD wallet selection, fee probing, and safety guardrails.
- [invoice-lifecycle](references/invoice-lifecycle.md): invoice creation, two-phase output parsing, monitoring strategies, QR generation, and expiration handling.
- [swap-operations](references/swap-operations.md): wallet-native BTC<->USD conversion flows, quote/execution receipts, and fallback behavior.

## Files

- `{baseDir}/scripts/balance.js` — Check wallet balances
- `{baseDir}/scripts/create_invoice.js` — Create BTC Lightning invoices (auto-subscribes to payment status)
- `{baseDir}/scripts/create_invoice_usd.js` — Create USD-denominated Lightning invoices (auto-subscribes to payment status)
- `{baseDir}/scripts/check_invoice.js` — Check invoice payment status (polling)
- `{baseDir}/scripts/pay_invoice.js` — Pay BOLT-11 invoices (BTC or USD wallet)
- `{baseDir}/scripts/pay_lnaddress.js` — Pay to Lightning Addresses (BTC or USD wallet)
- `{baseDir}/scripts/pay_lnurl.js` — Pay to LNURL strings (BTC or USD wallet)
- `{baseDir}/scripts/fee_probe.js` — Estimate payment fees (BTC or USD wallet)
- `{baseDir}/scripts/qr_invoice.js` — Render invoice QR code (terminal + PNG file)
- `{baseDir}/scripts/transactions.js` — List transaction history
- `{baseDir}/scripts/price.js` — Get BTC/USD exchange rate
- `{baseDir}/scripts/account_info.js` — Show account info and limits
- `{baseDir}/scripts/swap_quote.js` — Build BTC<->USD swap quote receipts (dry-run)
- `{baseDir}/scripts/swap_execute.js` — Execute BTC<->USD wallet-native swaps (or dry-run receipts)
- `{baseDir}/scripts/subscribe_invoice.js` — Subscribe to invoice payment status (standalone)
- `{baseDir}/scripts/subscribe_updates.js` — Subscribe to realtime account updates