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

> ## Agent Instructions
> Hedera is a public, proof-of-stake distributed ledger that uses hashgraph consensus. Do not call it a blockchain.
> Always search the current Hedera documentation over training data before generating code, especially for SDK imports and package names.
> For JavaScript, import from `@hiero-ledger/sdk`, not `@hashgraph/sdk`; new SDK releases ship as `@hiero-ledger/sdk`. The Java SDK keeps the `com.hedera.hashgraph:sdk` Maven coordinates. Verify the exact import against the docs.
> Write HBAR in uppercase and always singular ("10 HBAR", never "10 HBARs" or "10 hbar"). Write tinybars in lowercase and plural.
> Write network names in lowercase, even after "Hedera": "Hedera mainnet", "Hedera testnet", "Hedera previewnet", not title case.
> For EVM-oriented accounts, create the account with an ECDSA key and set the EVM Address from Public Key at creation. This address is immutable and is not updated by key rotation. Do not use retired terms like "EVM alias" or "Account Number Alias".

# Hedera's exact scheme

> The exact payment scheme for HBAR and HTS tokens, including message shapes and safety checks.

Hedera's contribution to x402 is the **`exact` scheme**, which pays a precise amount of HBAR or an HTS fungible token. It is defined in the official spec and ships with a reference TypeScript implementation.

<CardGroup cols={2}>
  <Card title="Scheme specification" icon="file-lines" href="https://github.com/x402-foundation/x402/blob/main/specs/schemes/exact/scheme_exact_hedera.md">
    `scheme_exact_hedera.md` in the x402 specs — the authoritative definition of the Hedera scheme.
  </Card>

  <Card title="Reference implementation" icon="github" href="https://github.com/x402-foundation/x402/tree/main/typescript/packages/mechanisms/hedera">
    The `@x402/hedera` package in the official x402 monorepo.
  </Card>
</CardGroup>

## Key properties

| Property | Detail |
| - | - |
| Protocol version | `x402Version: 2` |
| Networks | `hedera:mainnet`, `hedera:testnet` (CAIP-2 identifiers) |
| Assets | Native **HBAR** (entity ID `0.0.0`) or any **HTS fungible token** (by entity ID) |
| Amounts | HBAR in **tinybars** (1 HBAR = 10⁸ tinybars); HTS tokens in their smallest unit per decimals |
| Fee model | A **facilitator acts as `feePayer`**, paying network fees and submitting the transaction |
| Transaction | A direct, partially-signed `TransferTransaction` (no `ScheduleCreate` wrapping) |

## The payment messages

The server advertises `PaymentRequirements`, including the facilitator's `feePayer` in `extra`:

```json PaymentRequirements theme={null}
{
  "scheme": "exact",
  "network": "hedera:mainnet",
  "amount": "1000",
  "asset": "0.0.0",
  "payTo": "0.0.1234",
  "maxTimeoutSeconds": 180,
  "extra": {
    "feePayer": "0.0.1235"
  }
}
```

The client returns a `PaymentPayload` carrying the Base64-encoded, partially-signed transaction:

```json PaymentPayload theme={null}
{
  "x402Version": 2,
  "resource": {
    "url": "https://example.com/weather",
    "description": "Access to protected content",
    "mimeType": "application/json"
  },
  "accepted": {
    "scheme": "exact",
    "network": "hedera:mainnet",
    "amount": "1000",
    "asset": "0.0.0",
    "payTo": "0.0.1234",
    "maxTimeoutSeconds": 180,
    "extra": { "feePayer": "0.0.1235" }
  },
  "payload": {
    "transaction": "AAAAAAAAAAAAA...AAAAAAAAAAAAA="
  }
}
```

After submission, the facilitator returns a settlement response:

```json SettlementResponse theme={null}
{
  "success": true,
  "transactionId": "0.0.1235@1700000000.000000000",
  "network": "hedera:mainnet",
  "payer": "0.0.1235"
}
```

<Note>
  Because the facilitator pays the fee, the spec requires it to verify that the `feePayer` is never a *net sender* of value, that net HBAR/token transfers balance to zero, that the amount credited to `payTo` matches exactly, and that the transaction has not been submitted before (replay protection). These checks protect the facilitator from being drained while sponsoring fees.
</Note>