FuelLabs/fuel-core · error · Error::Serialization

Missing tx_pointer on contract input

Error message

Missing tx_pointer on contract input

What it means

contract_input_from_proto requires the tx_pointer sub-message on every ProtoContractInput; prost yields None for absent optional message fields and this code converts that into Error::Serialization. fuel-core's Contract input type always carries a TxPointer, so an input without one cannot be represented and the whole block decode fails.

Source

Thrown at crates/services/block_aggregator_api/src/blocks/old_block_source/convertor_adapter/proto_to_fuel_conversions.rs:120

    })?;
    Ok(StorageSlot::new(key, value))
}

fn contract_input_from_proto(
    proto: &ProtoContractInput,
) -> crate::result::Result<fuel_core_types::fuel_tx::input::contract::Contract> {
    let utxo_proto = proto.utxo_id.as_ref().ok_or_else(|| {
        Error::Serialization(anyhow!("Missing utxo_id on contract input"))
    })?;
    let utxo_id = utxo_id_from_proto(utxo_proto)?;
    let balance_root = Bytes32::try_from(proto.balance_root.as_slice()).map_err(|e| {
        Error::Serialization(anyhow!("Could not convert balance_root to Bytes32: {}", e))
    })?;
    let state_root = Bytes32::try_from(proto.state_root.as_slice()).map_err(|e| {
        Error::Serialization(anyhow!("Could not convert state_root to Bytes32: {}", e))
    })?;
    let tx_pointer_proto = proto.tx_pointer.as_ref().ok_or_else(|| {
        Error::Serialization(anyhow!("Missing tx_pointer on contract input"))
    })?;
    let tx_pointer = tx_pointer_from_proto(tx_pointer_proto)?;
    let contract_id =
        fuel_core_types::fuel_types::ContractId::try_from(proto.contract_id.as_slice())
            .map_err(|e| Error::Serialization(anyhow!(e)))?;

    Ok(fuel_core_types::fuel_tx::input::contract::Contract {
        utxo_id,
        balance_root,
        state_root,
        tx_pointer,
        contract_id,
    })
}

fn contract_output_from_proto(
    proto: &ProtoContractOutput,
) -> crate::result::Result<fuel_core_types::fuel_tx::output::contract::Contract> {

View on GitHub (pinned to b9d4d170da)

Solutions

1. Debug-print the failing ProtoContractInput to identify missing sub-messages.
2. Fix the encoder to always populate tx_pointer (and utxo_id) for contract inputs.
3. Pre-validate presence of both sub-messages and reject the tx early with an index-annotated error.
4. Re-obtain the block from a compatible peer.

Example fix

// before
let tx_pointer_proto = proto.tx_pointer.as_ref().ok_or_else(|| {
    Error::Serialization(anyhow!("Missing tx_pointer on contract input"))
})?;

// after: validate whole input first
fn contract_input_complete(p: &ProtoContractInput) -> bool {
    p.utxo_id.is_some() && p.tx_pointer.is_some()
}
if !contract_input_complete(input_proto) {
    return Err(Error::Serialization(anyhow::anyhow!(
        "input[{i}] incomplete contract input"
    )));
}

fn contract_input_has_tx_pointer(p: &ProtoContractInput) -> bool {
    p.tx_pointer.is_some()
}

fn contract_input_complete(p: &ProtoContractInput) -> bool {
    p.utxo_id.is_some() && p.tx_pointer.is_some()
}

match contract_input_from_proto(p) {
    Ok(input) => Some(input),
    Err(Error::Serialization(ctx)) if ctx.to_string().contains("tx_pointer") => {
        tracing::warn!(?p, "rejecting contract input without tx_pointer");
        None
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: Decoding a proto transaction whose contract input omitted the tx_pointer field - produced by an older/incompatible encoder, a third-party producer, or fixtures that fill only some sub-messages.

Common situations: Version skew across fuel-core releases that changed which sub-messages are populated; hand-written proto in tests; migration tooling that drops fields it does not understand.

Related errors

• Missing utxo_id on contract input
• Could not convert balance_root to Bytes32: {}
• Could not convert state_root to Bytes32: {}
• Missing receipt variant
• Missing panic reason

AI-assisted analysis of FuelLabs/fuel-core@b9d4d170da (2026-08-16). Data as JSON: /api/errors/048576257ec95826. Report an issue: GitHub.