Configured chains

Overview

In Lasso RPC Core v0.5.0, this endpoint lists chains in the default public profile. A chain configured only in another file profile does not appear. The list does not test whether an upstream can currently serve the chain.

Endpoint

GET /api/chains

Response

Returns a JSON object containing the default profile’s configured chains:

array

required

Array of chain configuration objects

Show chain properties

string

required

The numeric chain ID as a string (e.g., “1” for Ethereum Mainnet)

string

required

Human-readable name of the blockchain

string

required

Internal identifier used in API paths and configuration

boolean

required

Always true for a listed chain; this does not indicate upstream readiness

Response Example

{
  "chains": [
    {
      "chain_id": "1",
      "name": "Ethereum Mainnet",
      "chain_name": "ethereum",
      "supported": true
    },
    {
      "chain_id": "137",
      "name": "Polygon",
      "chain_name": "polygon",
      "supported": true
    },
    {
      "chain_id": "42161",
      "name": "Arbitrum One",
      "chain_name": "arbitrum",
      "supported": true
    }
  ]
}

Use Cases

Discover Available Chains

Query which chains the default public profile configures:

curl http://localhost:4000/api/chains

Validate Chain Configuration

Check if a specific chain is configured in public before making a default-profile RPC request:

# Check if Ethereum is configured
chains=$(curl -s http://localhost:4000/api/chains)
has_ethereum=$(echo $chains | jq '.chains[] | select(.chain_name=="ethereum") | .chain_id')

if [ -n "$has_ethereum" ]; then
  echo "Ethereum is configured with chain_id: $has_ethereum"
fi

Dynamic Client Configuration

Use this endpoint to build default-profile RPC URLs. It does not discover chains that exist only in custom profiles:

const response = await fetch('http://localhost:4000/api/chains');
const { chains } = await response.json();

// Build RPC endpoints for each chain
const rpcEndpoints = chains.reduce((acc, chain) => {
  acc[chain.chain_name] = `http://localhost:4000/rpc/${chain.chain_id}`;
  return acc;
}, {});

console.log(rpcEndpoints);
// {
//   ethereum: 'http://localhost:4000/rpc/1',
//   polygon: 'http://localhost:4000/rpc/137',
//   arbitrum: 'http://localhost:4000/rpc/42161'
// }

Chain Name vs Chain ID

Lasso RPC supports referencing chains by both their numeric chain_id and their chain_name:

chain_id: Standard EVM chain identifier (e.g., 1, 137, 42161)
chain_name: Human-friendly identifier used in configuration files (e.g., ethereum, polygon, arbitrum)

Both can be used in RPC endpoint paths:

# Using chain_id
curl -X POST http://localhost:4000/rpc/1 \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

# Using chain_name (if supported by your configuration)
curl -X POST http://localhost:4000/rpc/ethereum \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

Notes

The list comes from public.yml, not the union of all file profiles. See the released chain controller and configuration store.
All returned chains have supported: true because they are configured; this is not a live capability or availability check.
Validated profile YAML can be reloaded without restarting the instance; each node reads its own files. See Profiles and reload.
Use this endpoint for default-profile chain discovery; inspect a custom profile’s configuration separately.

HTTP API

WebSocket API

Status and metrics

Reference

Releases and evidence

Configured chains

Overview

Endpoint

Response

Response Example

Use Cases

Discover Available Chains

Validate Chain Configuration

Dynamic Client Configuration

Chain Name vs Chain ID

Notes

​Overview

​Endpoint

​Response

​Response Example

​Use Cases

​Discover Available Chains

​Validate Chain Configuration

​Dynamic Client Configuration

​Chain Name vs Chain ID

​Notes

Overview

Endpoint

Response

Response Example

Use Cases

Discover Available Chains

Validate Chain Configuration

Dynamic Client Configuration

Chain Name vs Chain ID

Notes