PIX and stablecoin infrastructure, under your brand

Who this is for

• A product that wants to hold end customers' reais without building custody from scratch.
• A platform that needs deposit, balance, PIX withdrawal and crypto withdrawal in one place.
• Anyone with users who needs each person's money separated with an auditable trail.

The problem

Holding other people's money is where most products stall. It is not just receiving: it is separating per customer, holding what cannot leave yet, proving every movement and being able to explain a balance months later. Building that from scratch means a ledger, reconciliation and an audit nobody wanted to start today.

Here the separation is a field. customer_ref travels on the charge, the balance, the withdrawal and the statement; the ledger is append-only and every line has an origin. You ship the experience under your brand and write no reconciliation.

The flow, end to end

1. Deposit: POST /cashin/charge with destino: "saldo" and the customer's customer_ref. The PIX becomes a BRL balance in their sub-account.
2. Read: GET /saldo?customer_ref= returns available, held and upcoming releases. GET /saldo/extrato returns movement by movement.
3. Withdraw in reais: POST /payouts with the same customer_ref — it debits the right sub-account.
4. Withdraw in crypto: POST /saldo/sacar-cripto delivers any catalog coin, with the route minimum checked before the debit.
5. Move between customers: POST /saldo/transferir settles inside the ledger, touching no external rail.

Endpoints used

A example that runs

# depósito na subconta de um cliente final
curl -X POST https://api.luniumpay.com/cashin/charge -H "X-API-Key: $LUNIUM_KEY" \
  -H "Content-Type: application/json" \
  -d '{"amount_cents":50000,"destino":"saldo","customer_ref":"cliente_412",
       "payer_tax_number":"12345678909","external_id":"dep-412-88"}'

# saldo daquele cliente
curl "https://api.luniumpay.com/saldo?customer_ref=cliente_412" -H "X-API-Key: $LUNIUM_KEY"

# transferência entre subcontas, sem sair do livro-razão
curl -X POST https://api.luniumpay.com/saldo/transferir -H "X-API-Key: $LUNIUM_KEY" \
  -H "Content-Type: application/json" \
  -d '{"from_customer_ref":"cliente_412","to_customer_ref":"cliente_907",
       "amount_cents":15000,"external_id":"tr-9912"}'

const h = { "X-API-Key": process.env.LUNIUM_KEY, "Content-Type": "application/json" };
const api = (rota, corpo) => fetch(`${API}${rota}`, corpo
  ? { method: "POST", headers: h, body: JSON.stringify(corpo) }
  : { headers: h }).then((r) => r.json());

export const depositar = (cliente, cents, cpf, id) => api("/cashin/charge", {
  amount_cents: cents, destino: "saldo", customer_ref: cliente,
  payer_tax_number: cpf, external_id: id,
});

export const saldoDe = (cliente) => api(`/saldo?customer_ref=${encodeURIComponent(cliente)}`);

export const sacarPix = (cliente, cents, chave, tipo, doc, id) => api("/payouts", {
  amount_cents: cents, pix_key: chave, pix_key_type: tipo,
  tax_number: doc, customer_ref: cliente, external_id: id,
});

export const sacarCripto = (cliente, cents, ativo, rede, carteira, doc, id) => api("/saldo/sacar-cripto", {
  amount_cents: cents, asset: ativo, chain: rede, payout_address: carteira,
  tax_number: doc, customer_ref: cliente, external_id: id,
});

import os, requests

API, H = "https://api.luniumpay.com", {"X-API-Key": os.environ["LUNIUM_KEY"]}

def depositar(cliente, cents, cpf, ident):
    return requests.post(f"{API}/cashin/charge", headers=H, timeout=30, json={
        "amount_cents": cents, "destino": "saldo", "customer_ref": cliente,
        "payer_tax_number": cpf, "external_id": ident}).json()

def saldo_de(cliente):
    return requests.get(f"{API}/saldo", headers=H, params={"customer_ref": cliente}, timeout=20).json()

def transferir(de, para, cents, ident):
    return requests.post(f"{API}/saldo/transferir", headers=H, timeout=30, json={
        "from_customer_ref": de, "to_customer_ref": para,
        "amount_cents": cents, "external_id": ident}).json()

Sandbox: test before spending

One call, no prior approval, no card; only your email is required (that is where we send the manual, the flowchart and the integration steps). The lun_test_ key exercises the whole surface without moving any money.

curl -X POST https://api.luniumpay.com/keys/sandbox \
  -H "Content-Type: application/json" \
  -d '{"email":"you@company.com","name":"my-test"}'

What the sandbox does not prove: real settlement. No crypto moves and no PIX is paid — it is there to get the contract right, not to measure the rail.

Assets and networks

Use GET /catalog for incoming crypto and GET /cashin/catalog for delivery after Pix. Asset availability, networks and minimums differ between the two directions and can change.

Send the returned deposit_tag with a deposit when required. Use payout_tag for an outgoing route that requires a memo. See the API manual for the current contract.

Limits and holds

Read account limits and fees from GET /keys/me, payer availability from GET /cashin/limits?payer_tax=... and route minimums from previews. Cash-in, cash-out and payouts have different constraints.

A received payment can be held before settlement. Track status, timeline and signed events until the final outcome; read expiry from expires_at.

Measurements, not promises

Settlement time depends on the payment flow, route availability, network confirmations and any hold. Track the final state and check service status. Sandbox timing does not measure real settlement.

Idempotency

Send external_id on every money-moving call. Repeating the same call returns the same operation, never a second one; the same parameters with a different id create two, and the same id with different parameters answers 409 external_id_divergente instead of guessing.

A timeout is not a refusal. If the call did not answer, look the operation up by external_id before repeating — it may already exist.

Webhooks and reconciliation

Every transition fires an event signed with HMAC SHA-256 plus a timestamp (header X-Lunium-Signature, format t=…,v1=…) — the timestamp is what stops a captured delivery from being replayed. Verify the signature before trusting the body.

The webhook is the primary signal; polling is optional. When you do poll, the status carries a timeline stamped by the server — draw the stage from it, because your polling stopwatch measures your network, not the operation.

Did not answer 2xx? Delivery is retried with backoff. You can resend by hand at POST /webhooks/deliveries/{event_id}/retry and test your URL at POST /webhooks/test.

When it goes wrong

First-PIX hold: the credit is available immediately; only the first PIX from a document above BRL 100.00 is held for 24 h at the provider and shows as delayed in GET /saldo, releasing on its own with saldo.liberado — show the time to the customer, not a generic error.

Insufficient balance: 402 with available and held stated separately. Nothing is debited.

Withdrawal below the coin's minimum: refused before the debit, with the estimated minimum in reais — the customer's balance never leaves for a delivery that would die at the exchange.

Security

• webhook assinado — Todo webhook vai assinado em HMAC SHA-256 com timestamp (header X-Lunium-Signature, formato t=…,v1=…), o que impede replay de uma entrega capturada.
• idempotencia — external_id em cash-in, cash-out e payout: repetir a mesma chamada devolve a MESMA operação, nunca uma segunda. Parâmetros diferentes no mesmo external_id respondem 409.
• egress validado — A URL de webhook é resolvida e validada antes de cada entrega: endereço interno, metadata de nuvem e redirect para rede privada são recusados, e a conexão é fixada no IP validado.
• retencao fail closed — A retenção é verificada na liquidação e repetida na reivindicação SQL: nenhum caminho (worker, consulta de status, fila) consegue liquidar antes da hora.
• payout duravel — O saque grava a operação e debita o saldo na MESMA transação, antes de qualquer chamada ao provedor: não existe débito sem ordem para reconciliar.
• verificacao aberta — GET /v1/verificar/{e2e} confere um PIX liquidado sem chave nenhuma — a contraparte não precisa confiar na nossa palavra.

Open verification is the one that matters in a negotiation: your counterparty checks the PIX themselves, with no key and without taking our word for it.

Time to first integration

The deposit screen is one call; the balance screen is another. What usually takes longer is designing your balance screen — current fees and holds are visible in the API, so your interface can explain them without hard-coding anything.

Questions integrators ask