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Submits a signed legacy, EIP-2930, or EIP-1559 transaction with predicates that control when Base can include it. EIP-1559 is recommended.
This method is available on Base Mainnet and Base Sepolia through the sequencer endpoints listed in Connect to Base, and on Vibenet.

Parameters

Pass two parameters. The first is a signed, serialized transaction. The second contains a non-empty validity array. The validity array must include a block_number predicate with an upper bound (<, <=, or =). The last block it allows must be no earlier than the block being built and within 60 seconds of submission. See Expiry. The block number in this example is a placeholder. Before you submit, call eth_blockNumber and use the latest block number plus 10, as a 0x-prefixed hexadecimal string.

Predicates

The supported operators are <, <=, =, !=, >, and >=. Predicate values use 0x-prefixed hexadecimal strings. The mask defaults to all ones. A flashblock_index value must be between 1 and 10, inclusive (0x1 through 0xa in hexadecimal).

Returns

string
The 32-byte hash of the submitted transaction.
Returning a hash confirms acceptance. It does not confirm inclusion.

Errors

The method returns JSON-RPC errors. Handle an unavailable method, invalid parameters, and a missing transaction hash. Error codes and messages are not yet stable. Read Predicates and Safety for evaluation rules. Read Troubleshooting when a transaction is not included.