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# Read the correct block number on Robinhood Chain

Solidity block.number and the RPC L2 height describe different counters.

**On this page**[The counters have different purposes](https://supanode.xyz/learn/robinhood-chain-block-number#the-counters-have-different-purposes)[Read the L2 height explicitly](https://supanode.xyz/learn/robinhood-chain-block-number#read-the-l2-height-explicitly)[Choose a counter per feature](https://supanode.xyz/learn/robinhood-chain-block-number#choose-a-counter-per-feature)[Test migration assumptions](https://supanode.xyz/learn/robinhood-chain-block-number#test-migration-assumptions)[Sources](https://supanode.xyz/learn/robinhood-chain-block-number#sources)

## The counters have different purposes

On Robinhood Chain's Arbitrum stack, Solidity `block.number` is an estimate of the parent Ethereum block number. `eth_blockNumber` reports the latest Robinhood L2 block. Comparing the two as if they were the same counter creates false lag alarms and incorrect timeout logic.

## Read the L2 height explicitly

```
// Contract-side interface, simplified:
interface ArbSys {
    function arbBlockNumber() external view returns (uint256);
}
uint256 l2Height = ArbSys(address(0x64)).arbBlockNumber();
```

Use the network's documented ArbSys precompile. For off-chain monitoring, read eth\_blockNumber and attach the chain ID to the metric. Do not compare a Solidity-emitted parent-height estimate with an RPC L2-height series.

## Choose a counter per feature

1.  For local L2 indexing, store L2 block number, hash and parent hash.
2.  For L1 settlement tracking, follow the documented parent-chain and batch signals.
3.  For elapsed-time policies, use the appropriate timestamp or clock rather than multiplying L2 blocks by an assumed Ethereum interval.
4.  For cross-chain messages, use their documented identifiers and settlement status instead of a guessed block conversion.

## Test migration assumptions

Search an existing contract and backend for block.number, confirmation counts and block-based timeouts. A voting window, rate limiter or oracle cache written for Ethereum may behave differently on a faster L2. Add test fixtures that advance the relevant counter independently. Label dashboards with L1 or L2 in the metric name so an operator can tell which number a warning describes.

## Sources

-   [Robinhood block-number semantics](https://docs.robinhood.com/chain/differences-from-ethereum/)
-   [Arbitrum Solidity differences](https://docs.arbitrum.io/build-decentralized-apps/arbitrum-vs-ethereum/solidity-support)

## Continue reading

[Robinhood RPC and WebSocket](https://supanode.xyz/blog/robinhood-chain-rpc-websocket)[Robinhood methods](https://supanode.xyz/docs/robinhood/rpc/whats-available)[Learn library](https://supanode.xyz/learn)

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Source: https://supanode.xyz/learn/robinhood-chain-block-number