eth_simulateV1

Simulates one or more transaction bundles against the current pre-confirmed Flashblock state. Only available on Flashblocks endpoints.

Simulates one or more transaction bundles against the current pre-confirmed Flashblock state. Supports state overrides, multi-block simulation, and optional transfer tracing.

Only available on Flashblocks endpoints: https://mainnet.base.org / https://sepolia.base.org.

Parameters

simulationPayload · object · required

The simulation configuration.

Show Simulation payload fields

blockStateCalls · array · required

Array of block state call objects. Each object represents one simulated block.

Show Block state call fields

calls · array

Array of transaction call objects to simulate within this block.

stateOverrides · object

Per-address state overrides applied before simulation (e.g., balance, nonce, code, storage). Optional.

blockOverrides · object

Block-level overrides (e.g., number, timestamp). Optional.

traceTransfers · boolean

If true, ETH transfer events are included as logs in the result. Defaults to false.

validation · boolean

If true, transaction validation (nonce, balance) is enforced. Defaults to false.

blockParameter · string · required

Use "pending" to simulate against the current Flashblock state.

Returns

result · array

Array of simulated block results, one per entry in blockStateCalls. Each entry is a full block object with a calls field embedded alongside standard block fields.

Show Block result fields

number · string

Simulated block number (hex).

hash · string

Simulated block hash.

parentHash · string

Parent block hash.

timestamp · string

Block timestamp (hex).

gasLimit · string

Gas limit (hex).

gasUsed · string

Total gas used by the simulated calls (hex).

baseFeePerGas · string

Base fee per gas (hex).

stateRoot · string

Always "0x000...000" — simulation does not commit state to the trie.

calls · array

Array of individual call results.

Show Call result fields

status · string

"0x1" for success, "0x0" for failure.

gasUsed · string

Gas used as a hexadecimal integer.

returnData · string

Hex-encoded return data.

logs · array

Logs emitted (including ETH transfer logs if traceTransfers is true).

error · string

Revert reason if the call failed. Optional.

Example

cURL

curl https://sepolia.base.org \
  -X POST \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_simulateV1",
    "params": [
      {
        "blockStateCalls": [
          {
            "calls": [{"to": "0x...", "data": "0x..."}],
            "stateOverrides": {}
          }
        ],
        "traceTransfers": true,
        "validation": true
      },
      "pending"
    ],
    "id": 1
  }'