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# Watch Token Mints \[token.watchMint]

Watches TIP-20 `Mint` events for a token.

## Usage

:::code-group
```ts twoslash [example.ts]
import { client } from './viem.config'

const watcher = client.token.watchMint({
  token: '0x20c0000000000000000000000000000000000000',
})

watcher.onLogs((logs) => {
  for (const log of logs) console.log(log.args)
  // @log: { to: '0x70997970C51812dc3A010C7d01b50e0d17dc79C8', amount: 100000000n }
})

// Later, tear down the watcher.
watcher.off()
```

```ts twoslash [viem.config.ts] filename="viem.config.ts"
// [!include ~/snippets/tempo/viem.config.ts:setup]
```
:::

Also callable standalone: `Actions.token.watchMint(client, options)`, with `Actions` imported from `'viem/tempo'`.

## Recipes

### Alert on Mints Your Issuance Service Did Not Submit

Watch every mint and compare it against the transactions your issuance service submitted; a mint you did not initiate is an early signal of a compromised issuer key.

:::code-group
```ts twoslash [example.ts]
import { client } from './viem.config'

// Transaction hashes of mints your issuance service submitted.
const pending = new Set<string>()

const watcher = client.token.watchMint({
  token: '0x20c0000000000000000000000000000000000000',
})

watcher.onLogs((logs) => {
  for (const log of logs) {
    if (log.transactionHash && pending.has(log.transactionHash)) continue // [!code focus]
    console.log('Unexpected mint:', log.args.to, log.args.amount) // [!code focus]
    // @log: Unexpected mint: 0x70997970C51812dc3A010C7d01b50e0d17dc79C8 100000000n
  }
})
```

```ts twoslash [viem.config.ts] filename="viem.config.ts"
// [!include ~/snippets/tempo/viem.config.ts:setup]
```
:::

### Credit Accounts When On-Ramp Mints Settle

Filter `args.to` to the customer wallets in an on-ramp batch, so each account is marked funded when its mint settles onchain.

:::code-group
```ts twoslash [example.ts]
import { client } from './viem.config'

const watcher = client.token.watchMint({
  args: { // [!code focus]
    to: [ // [!code focus]
      '0x742d35Cc6634C0532925a3b844Bc9e7595f0bEbb', // [!code focus]
      '0x8ba1f109551bD432803012645Ac136ddd64DBA72', // [!code focus]
    ], // [!code focus]
  }, // [!code focus]
  token: '0x20c0000000000000000000000000000000000000',
})

watcher.onLogs((logs) => {
  for (const log of logs) console.log('Funded:', log.args.to, log.args.amount)
  // @log: Funded: 0x742d35Cc6634C0532925a3b844Bc9e7595f0bEbb 100000000n
})
```

```ts twoslash [viem.config.ts] filename="viem.config.ts"
// [!include ~/snippets/tempo/viem.config.ts:setup]
```
:::

## Return Value

Returns a watcher handle. Watching starts when the first listener (or async iterator) attaches, and stops when `off` is called.

```ts
type ReturnType = {
  /** Registers a log listener. Starts the watcher on first registration. Returns an unregister function. */
  onLogs: (fn: (logs: readonly Log[]) => void) => () => void
  /** Registers an error listener. Returns an unregister function. */
  onError: (fn: (error: Error) => void) => () => void
  /** Tears down the watcher: removes listeners, ends iterators, stops the poll or subscription. */
  off: () => void
  /** Async-iterates emitted log batches (latest-only stream). */
  [Symbol.asyncIterator]: () => AsyncIterableIterator<{ logs: readonly Log[] }>
}
```

Each log is decoded, with the event arguments on `args`:

```ts
type Log = {
  /** Decoded `Mint` event arguments. */
  args: {
    /** Address that received the tokens. */
    to: Address
    /** Amount minted. */
    amount: bigint
  }
  /** Name of the emitted event. */
  eventName: 'Mint'
  // ...standard log fields (address, blockHash, blockNumber, logIndex, transactionHash, ...)
}
```

## Parameters

### args

* **Type:** `object`

```ts
type Args = {
  /** Filter by recipient address. */
  to?: Address | Address[] | null
}
```

Indexed argument values to filter logs by.

### batch

* **Type:** `boolean`
* **Default:** `true`

Whether to batch the logs found within a poll interval into a single emission. When `false`, each log is emitted on its own.

### fromBlock

* **Type:** `bigint`

Block number from which to start watching for logs.

### poll

* **Type:** `boolean`

Whether to poll for new logs instead of using a subscription. Defaults to `true` when the transport cannot subscribe or `fromBlock` is provided.

### pollingInterval

* **Type:** `number`
* **Default:** `client.pollingInterval`

Polling frequency (in ms).

### token

* **Type:** `Address | bigint`

Token to operate on: a TIP-20 token id or a contract address.