nautechsystems/nautilus_trader · error

Failed to decode initialize event data: {e}

Error message

Failed to decode initialize event data: {e}

What it means

Thrown by parse_initialize_event_hypersync when the data payload is at least 64 bytes but alloy's abi_decode of InitializeEventData still fails, with the underlying decode error message embedded. This usually means the words are present but the values/types do not match the struct (e.g. dynamic-encoded data or extra/odd-length bytes).

Source

Thrown at crates/adapters/blockchain/src/exchanges/parsing/uniswap_v3/initialize.rs:65

/// Panics if the contract address is not set in the log.
pub fn parse_initialize_event_hypersync(
    dex: SharedDex,
    log: &HypersyncLog,
) -> anyhow::Result<InitializeEvent> {
    validate_event_signature_hash("InitializeEvent", INITIALIZE_EVENT_SIGNATURE_HASH, log)?;

    if let Some(data) = &log.data {
        let data_bytes = data.as_ref();

        // Validate if data contains 2 parameters of 32 bytes each (sqrtPriceX96 and tick)
        if data_bytes.len() < 2 * 32 {
            anyhow::bail!("Initialize event data is too short");
        }

        // Decode the data using the InitializeEventData struct
        let decoded = match <InitializeEventData as SolType>::abi_decode(data_bytes) {
            Ok(decoded) => decoded,
            Err(e) => anyhow::bail!("Failed to decode initialize event data: {e}"),
        };

        let pool_address = Address::from_slice(
            log.address
                .clone()
                .expect("Contract address should be set in logs")
                .as_ref(),
        );
        let pool_identifier = PoolIdentifier::Address(Ustr::from(&pool_address.to_string()));

        Ok(InitializeEvent::new(
            dex,
            pool_identifier,
            decoded.sqrt_price_x96,
            i32::try_from(decoded.tick)?,
        ))
    } else {
        Err(anyhow::anyhow!("Missing data in initialize event log"))

View on GitHub (pinned to 18893faf8b)

Solutions

1. Check that data_bytes.len() is exactly 64 bytes; truncate or reject otherwise.
2. Decode the two words manually (sqrtPriceX96: uint256, tick: int24 in first 32-byte word) to inspect raw values.
3. Verify the emitting contract is a canonical Uniswap V3 pool.
4. Check alloy-sol-types version compatibility for the generated InitializeEventData type.

Example fix

// before
if data_bytes.len() < 2 * 32 { bail!("too short"); }
let decoded = <InitializeEventData as SolType>::abi_decode(data_bytes)?;
// after: strict length check
if data_bytes.len() != 2 * 32 {
    anyhow::bail!("Initialize data must be 64 bytes, got {}", data_bytes.len());
}
let decoded = <InitializeEventData as SolType>::abi_decode(data_bytes)?;

// Ensure exact-length data before parsing
fn is_initialize_shaped(log: &HypersyncLog) -> bool {
    log.data.as_ref().map(|d| d.len() == 64).unwrap_or(false)
}
if !is_initialize_shaped(&log) { skip(&log); }

fn exact_initialize_data(log: &HypersyncLog) -> Option<&[u8]> {
    let d = log.data.as_deref()?;
    (d.len() == 64).then_some(d)
}

match parse_initialize_event_hypersync(log, dex) {
    Ok(event) => process(event),
    Err(e) if e.to_string().contains("Failed to decode initialize") => {
        log::warn!("non-canonical initialize payload: {e}");
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: A Hypersync log whose data is >= 64 bytes but not exactly two 32-byte static words — e.g. data length not a multiple of 32, trailing bytes, or data from a different event ABI.

Common situations: Forked V3 deployments with modified Initialize events, corrupted or re-serialized hypersync payloads, mixing up data from a different event with the same topic0.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Initialize event data is too short
• Missing tickLower in topic2 when parsing mint event
• Missing tickUpper in topic3 when parsing mint event
• Mint event data is too short
• Failed to decode mint event data: {e}

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/96e2c45d0179074a. Report an issue: GitHub.