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

# Curate Classic Integration

> Developer guide for integrating Kleros Curate Classic (V1) with on-chain storage, covering contracts, item lifecycle, and dispute handling.

# Curate Classic: Integration for Devs

<Note>
  This covers Curate Classic (V1) with on-chain storage. For the newer Light Curate with subgraph-based storage, see [Light Curate Integration](/developers/products/curate/light-curate). For V2 Curate, see the [Developers Curate section](/developers/products/curate/overview).
</Note>

***

## Overview

Curate Classic is the original version of Kleros Curate. All item data (apart from files/images) is stored on-chain in contract storage. This means other contracts can query the TCR for field values directly, but deployment and operation costs are higher.

Key characteristics:

* Item data stored on-chain as encoded bytes
* Requires `@kleros/gtcr-encoder` to encode/decode items
* Client must sync by downloading every item and decoding it
* Higher gas costs (O(n) storage)
* Other contracts can read item fields directly

***

## Reading Data

### Using the Subgraph

Use the `items` entity (not `litems`, which is for Light Curate):

```graphql theme={null}
{
  items(
    first: 10
    where: {
      status: Registered
      registryAddress: "0xYOUR_REGISTRY_LOWERCASE"
    }
  ) {
    itemID
    data
    status
  }
}
```

The `data` field contains encoded bytes. Decode using `@kleros/gtcr-encoder`.

### Using the Encoder

```bash theme={null}
npm install @kleros/gtcr-encoder
```

```javascript theme={null}
const { gtcrDecode } = require("@kleros/gtcr-encoder");
const columns = [/* column definitions from the TCR meta evidence */];
const decodedItem = gtcrDecode({ columns, values: item.data });
```

***

## Writing Data

### Submitting an Item

Encode the item fields and call `addItem()` on the GeneralizedTCR contract with the required deposit.

### Challenging an Item

Call `challengeRequest()` on the contract with a deposit. The challenge creates a dispute in Kleros Court.

### Executing Requests

Call `executeRequest()` after the challenge period passes without a challenge.

***

## Resources

<CardGroup cols={2}>
  <Card title="Curate Classic Contracts" icon="github" href="https://github.com/kleros/tcr">
    Source code
  </Card>

  <Card title="Subgraph" icon="database" href="https://thegraph.com/explorer/subgraphs/A5oqWboEuDezwqpkaJjih4ckGhoHRoXZExqUbja2k1NQ">
    legacy-curate-mainnet subgraph on Graph Explorer
  </Card>
</CardGroup>