bex_simulate

Validate a BEX request without storing it. Returns whether the request would be accepted, its deterministic bundle hash, and a list of any validation issues.

Use this to verify your request is well-formed before submitting with bex_sendBundle.

Parameters

Identical to bex_sendBundle:

Field	Type	Required	Description
targetBlock	number	Yes	Block number to target
replacementUuid	string	No	UUID (validated but not stored)
replacementNonce	number	No	Replacement nonce (validated but not stored)
bex	object	Yes	BEX extension with compute and execute specs

Request

{
  "jsonrpc": "2.0",
  "method": "bex_simulate",
  "params": [{
    "targetBlock": 20000000,
    "bex": {
      "compute": {
        "to": "0x1111111111111111111111111111111111111111",
        "calldata": "0x70a08231..."
      },
      "execute": {
        "to": "0x2222222222222222222222222222222222222222",
        "selector": "0xa9059cbb",
        "prefixArgs": "0x",
        "appendComputeResult": true
      }
    }
  }],
  "id": 1
}

Response

{
  "jsonrpc": "2.0",
  "result": {
    "accepted": true,
    "bundleHash": "0xabcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890",
    "issues": []
  },
  "id": 1
}

If validation fails:

{
  "jsonrpc": "2.0",
  "result": {
    "accepted": false,
    "bundleHash": "0xabcdef...",
    "issues": [
      "Compute calldata too large: 5000 > 4096",
      "Signer not in allowlist"
    ]
  },
  "id": 1
}

Field	Type	Description
accepted	boolean	true if the request passes all validation checks
bundleHash	string	Deterministic hash of the request (same as bex_sendBundle would return)
issues	string[]	List of validation errors. Empty if accepted is true.

Notes

• The request is not stored — simulate never affects block building.

• The bundleHash is deterministic: the same inputs always produce the same hash, so you can use it to correlate with a future bex_sendBundle submission.