---
name: meshjs-cardano
description: "MeshJS patterns: tx building, wallet connectors, script interactions. TypeScript/JavaScript Cardano development."
allowed-tools:
  - Read
  - Write
user-invocable: true
---

# meshjs-cardano

## When to use
- Building Cardano dApps with MeshJS (TypeScript/JavaScript)
- Integrating CIP-30 wallet connectors
- Transaction building in browser or Node.js

## Operating rules (must follow)
- Confirm MeshJS version and environment (Next.js, Vite, Node)
- Never request seed phrases or private keys
- Handle wallet disconnects gracefully
- Test on preprod before mainnet

## Setup

### Installation
```bash
npm install @meshsdk/core @meshsdk/react
# or
yarn add @meshsdk/core @meshsdk/react
```

### Provider setup
```typescript
import { BlockfrostProvider } from '@meshsdk/core';

const provider = new BlockfrostProvider('<PROJECT_ID>');
// or for preprod:
const provider = new BlockfrostProvider('<PROJECT_ID>', 'preprod');
```

## Wallet connection (React)

```tsx
import { CardanoWallet, useWallet } from '@meshsdk/react';

function App() {
  const { connected, wallet } = useWallet();

  return (
    <div>
      <CardanoWallet />
      {connected && <p>Connected!</p>}
    </div>
  );
}
```

## Transaction building

### Simple ADA transfer
```typescript
import { Transaction } from '@meshsdk/core';

const tx = new Transaction({ initiator: wallet })
  .sendLovelace(
    'addr_test1qz...',
    '5000000'  // 5 ADA
  );

const unsignedTx = await tx.build();
const signedTx = await wallet.signTx(unsignedTx);
const txHash = await wallet.submitTx(signedTx);
```

### With native tokens
```typescript
const tx = new Transaction({ initiator: wallet })
  .sendAssets(
    'addr_test1qz...',
    [
      { unit: 'lovelace', quantity: '2000000' },
      { unit: '<policy_id><asset_name_hex>', quantity: '1' }
    ]
  );
```

### With metadata
```typescript
const tx = new Transaction({ initiator: wallet })
  .sendLovelace('addr_test1qz...', '1000000')
  .setMetadata(674, { msg: ['Hello from MeshJS'] });
```

## Script interactions

### Lock funds at script
```typescript
import { Data } from '@meshsdk/core';

const datum: Data = {
  alternative: 0,
  fields: [wallet.getPaymentAddress()]
};

const tx = new Transaction({ initiator: wallet })
  .sendLovelace(
    {
      address: scriptAddress,
      datum: { inline: datum }
    },
    '5000000'
  );
```

### Spend from script
```typescript
const tx = new Transaction({ initiator: wallet })
  .redeemValue({
    value: scriptUtxo,
    script: plutusScript,
    datum: datum,
    redeemer: { data: { alternative: 0, fields: [] } }
  })
  .sendLovelace(recipientAddress, '4500000')
  .setCollateral([collateralUtxo]);
```

## Examples

### Example: NFT minting
**User request:** "Mint an NFT with MeshJS"

**Response:**
```typescript
import { ForgeScript, Transaction } from '@meshsdk/core';

// Create minting script (time-locked)
const { pubKeyHash } = wallet.getPaymentAddress();
const forgingScript = ForgeScript.withOneSignature(pubKeyHash);

const assetMetadata = {
  name: 'My NFT',
  image: 'ipfs://...',
  mediaType: 'image/png'
};

const tx = new Transaction({ initiator: wallet })
  .mintAsset(
    forgingScript,
    {
      assetName: 'MyNFT',
      assetQuantity: '1',
      metadata: assetMetadata,
      label: '721',
      recipient: wallet.getPaymentAddress()
    }
  );

const unsignedTx = await tx.build();
const signedTx = await wallet.signTx(unsignedTx);
const txHash = await wallet.submitTx(signedTx);
console.log('Minted:', txHash);
```

### Example: Query UTxOs
```typescript
import { BlockfrostProvider } from '@meshsdk/core';

const provider = new BlockfrostProvider('<PROJECT_ID>');

// Get UTxOs for address
const utxos = await provider.fetchAddressUTxOs(address);

// Get UTxOs at script address
const scriptUtxos = await provider.fetchAddressUTxOs(scriptAddress);

// Filter by asset
const nftUtxos = utxos.filter(utxo =>
  utxo.output.amount.some(a => a.unit.includes(policyId))
);
```

## Common patterns

### Error handling
```typescript
try {
  const txHash = await wallet.submitTx(signedTx);
  console.log('Success:', txHash);
} catch (error) {
  if (error.message.includes('UTxO')) {
    console.log('UTxO issue - refresh and retry');
  } else if (error.message.includes('collateral')) {
    console.log('Need ADA-only UTxO for collateral');
  }
}
```

### Wallet state management
```typescript
const { connected, connecting, disconnect, wallet, name } = useWallet();

// Check connection before operations
if (!connected) {
  throw new Error('Wallet not connected');
}

// Get network
const network = await wallet.getNetworkId();
// 0 = testnet, 1 = mainnet
```

## Safety / key handling
- Never request seed phrases
- Validate CIP-30 API availability
- Handle disconnects gracefully
- Show confirmation before signing

## References
- `shared/PRINCIPLES.md`
- [MeshJS documentation](https://meshjs.dev)
- [CIP-30 Wallet API](https://cips.cardano.org/cips/cip30/)