# Errors

Reference for all error types and codes in the Casper JS SDK.

## RpcError

Thrown when the node returns a JSON-RPC error.

```ts
class RpcError extends Error {
  readonly code: number;     // ErrorCode value
  readonly data?: unknown;   // Optional additional info
}
```

## ErrorCode

| Constant | Value | Description |
|---|---|---|
| `NoSuchEntity` | -32001 | Account or entity not found (not funded) |
| `AccountMigratedToEntity` | -32002 | 1.x account migrated to 2.x entity format |
| `NoSuchBlock` | -32003 | Block hash or height not found |
| `NoSuchDeploy` | -32004 | Transaction or deploy hash not found |
| `FailedToGetBalance` | -32005 | Balance query failed |

## HttpError

Thrown for HTTP transport failures.

```ts
class HttpError extends Error {
  readonly statusCode: number; // HTTP status (e.g., 503)
}
```

## SSE Result Errors

The SSE client returns `Result<boolean, string>` from `ts-results`:

| String | When |
|---|---|
| `'Already subscribed to this event'` | `subscribe()` called twice for same event |
| `'Not subscribed to this event'` | `unsubscribe()` called when not subscribed |

## Custom Errors

| Class | When thrown |
|---|---|
| `ErrInvalidPublicKeyAlgo` | Unknown key algorithm prefix byte |
| `ErrInvalidBidAddrTag` | Invalid BidAddr tag byte |