> ## Documentation Index
> Fetch the complete documentation index at: https://docs.velumx.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

# Introduction

Welcome to VelumX — the Relayer-as-a-Service (RaaS) infrastructure for gasless transactions on the Stacks blockchain.

## The Problem

Traditional blockchain applications require users to hold native tokens (STX on Stacks) to pay for transaction fees. This creates real friction:

* **Onboarding barrier**: New users must acquire STX before they can do anything.
* **Poor UX**: Users manage multiple token types just to execute simple actions.
* **Adoption blocker**: Limits DeFi growth by requiring upfront capital in the wrong asset.

## The VelumX Solution

VelumX is a **Relayer-as-a-Service** platform. Developers integrate gasless transactions by calling `velumx.sponsor(txHex)` — VelumX handles all the relayer infrastructure behind that single call.

<CardGroup cols={2}>
  <Card title="Stacks-Native" icon="bolt">
    Uses Stacks' built-in sponsored transaction capability. No smart wallets, no account abstraction.
  </Card>

  <Card title="Multi-Tenant" icon="users">
    Every developer gets an isolated relayer address and API key. Funds never mix.
  </Card>
</CardGroup>

## What VelumX Provides

| Component           | Description                                                               |
| :------------------ | :------------------------------------------------------------------------ |
| **Relayer Backend** | Multi-tenant key derivation, STX sponsorship, nonce management, broadcast |
| **`@velumx/sdk`**   | `sponsor()`, `estimateFee()`, `buildSponsoredContractCall()`              |
| **Dashboard**       | API key management, relayer funding, usage stats, key export              |
| **Pricing Oracle**  | Real-time token→STX pricing for accurate fee estimation                   |

## What Developers Provide

* Their own contract calls (swap, bridge, stake — anything on Stacks)
* Optionally: their own paymaster contract for USER\_PAYS fee collection
* An API key from the VelumX Dashboard

## Two Integration Paths

**DEVELOPER\_SPONSORS** — simplest path. The developer's relayer pays STX gas. Users pay nothing.

```typescript theme={null}
// Build any Stacks contract call as sponsored
const tx = await buildSponsoredContractCall({ ... });
const signed = await wallet.sign(tx);
const { txid } = await velumx.sponsor(signed);
```

**USER\_PAYS** — user pays a SIP-010 token fee. Developer deploys their own paymaster contract that atomically collects the fee and executes the action.

```typescript theme={null}
// User pays fee in USDCx, action executes atomically
const tx = await buildSponsoredContractCall({
  contractAddress: 'SP...my-paymaster',
  functionName: 'swap-with-fee',
  functionArgs: [...]
});
const signed = await wallet.sign(tx);
const { txid } = await velumx.sponsor(signed);
```