> For the complete documentation index, see [llms.txt](https://docs.spacy.computer/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.spacy.computer/recipes/send-transaction.md).

# Send a transaction

Wire `signAndSend` to a button. Show pending state, success state, and a proof link.

```tsx
import { useWallet, useSign } from '@spacy-computer/sdk'

const RECIPIENT = '0x000000000000000000000000000000000000dEaD' as const

export function SendButton() {
  const { wallet } = useWallet()
  const { signAndSend, pending, error, lastResult } = useSign()

  if (!wallet) return null

  const onClick = async () => {
    try {
      const { txHash, attestationSlug } = await signAndSend({
        to: RECIPIENT,
        value: '0.01', // ETH, parsed by the SDK
      })
      console.log('Broadcast:', txHash)
      console.log('Proof:', `https://spacy.computer/proof/${attestationSlug}`)
    } catch (e) {
      // already captured in `error`; rethrow only if you need to bubble
    }
  }

  return (
    <section>
      <button disabled={pending} onClick={onClick}>
        {pending ? 'Signing…' : 'Send 0.01 ETH'}
      </button>

      {error && <p role="alert">Failed: {error.message}</p>}

      {lastResult && (
        <p>
          Sent.{' '}
          <a href={`https://spacy.computer/proof/${lastResult.attestationSlug}`}>
            View attestation
          </a>
        </p>
      )}
    </section>
  )
}
```

## Calling a contract

For anything beyond a plain native transfer, encode the calldata yourself with `viem` and bump `gas`:

```tsx
import { encodeFunctionData, parseAbi } from 'viem'

const erc20 = parseAbi([
  'function transfer(address to, uint256 amount) returns (bool)',
])

await signAndSend({
  to: '0xToken...',
  data: encodeFunctionData({
    abi: erc20,
    functionName: 'transfer',
    args: [recipient, 1_000_000n], // 1 USDC if 6 decimals
  }),
  gas: 75_000n,
})
```

## Things to know

* **The wallet pays for its own gas.** `signAndSend` does not run a relayer or paymaster. Make sure the wallet has enough native ETH on the configured chain. On Sepolia, faucets like [sepoliafaucet.com](https://sepoliafaucet.com) work.
* **You can't override `nonce` or fees.** The SDK reads them from the configured RPC. If you need custom behaviour, drop down to [`SpacyClient`](/reference/spacy-client.md) and `client.publicClient` directly.
* **The default `gas` of `21_000` only works for native transfers.** Override for any contract call. Underestimating gas causes the broadcast to revert at the RPC level — your `signAndSend` rejects.
* **The transaction is broadcast, not awaited.** `signAndSend` returns once the RPC has accepted the raw transaction. To wait for inclusion, use the SDK's `client.publicClient`:

```tsx
import { useSpacy } from '@spacy-computer/sdk'

const { client } = useSpacy()
const { txHash } = await signAndSend(req)
const receipt = await client.publicClient.waitForTransactionReceipt({ hash: txHash })
```

## Pairing with `useAttestation`

If you want the proof status (IPFS pin, on-chain pointer) to update inline after the broadcast, hand the slug to `useAttestation`:

```tsx
const { signAndSend, lastResult } = useSign()
const { proof } = useAttestation(lastResult?.attestationSlug)

return (
  <>
    <button onClick={() => signAndSend(req)}>Send</button>
    {proof && <span>Proof: {proof.status}</span>}
  </>
)
```

See [Render a proof page](/recipes/proof-page.md) for a fuller version.

## Errors you may see

| Message                                                    | Why                                                                              |
| ---------------------------------------------------------- | -------------------------------------------------------------------------------- |
| `wallet_not_ready`                                         | `wallet` was `null` when you called `signAndSend`. Gate on `useWallet().wallet`. |
| `spacy_api_401`                                            | Session expired during the call. Trigger `login()`.                              |
| `spacy_api_502`                                            | KMS sign call failed upstream. Retry.                                            |
| viem RPC errors (`insufficient funds`, `nonce too low`, …) | Standard EVM broadcast errors. Surface to the user.                              |

The full list lives at [Errors](/notes/errors.md).


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.spacy.computer/recipes/send-transaction.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.