Invalid config type for BlockchainDataClientFactory. Expecte

Error message

Invalid config type for BlockchainDataClientFactory. Expected `BlockchainDataClientConfig`, was {config:?}

What it means

BlockchainDataClientFactory.create downcasts the passed config object to BlockchainDataClientConfig. This error fires when the config object supplied to the factory is of a different concrete type, so the downcast_ref returns None.

Source

Thrown at crates/adapters/blockchain/src/factories.rs:86

impl Default for BlockchainDataClientFactory {
    fn default() -> Self {
        Self::new()
    }
}

impl DataClientFactory for BlockchainDataClientFactory {
    fn create(
        &self,
        name: &str,
        config: &dyn ClientConfig,
        _cache: CacheView,
        _clock: Rc<RefCell<dyn Clock>>,
    ) -> anyhow::Result<Box<dyn DataClient>> {
        let blockchain_config = config
            .as_any()
            .downcast_ref::<BlockchainDataClientConfig>()
            .ok_or_else(|| {
                anyhow::anyhow!(
                    "Invalid config type for BlockchainDataClientFactory. Expected `BlockchainDataClientConfig`, was {config:?}"
                )
            })?;

        let client = BlockchainDataClient::new(ClientId::from(name), blockchain_config.clone());

        Ok(Box::new(client))
    }

    fn name(&self) -> &'static str {
        BLOCKCHAIN
    }

    fn config_type(&self) -> &'static str {
        "BlockchainDataClientConfig"
    }
}

View on GitHub (pinned to 18893faf8b)

Solutions

Pass a BlockchainDataClientConfig instance to the data client factory
Check the factory registration: data client factories must be paired with data client configs
Print the config's concrete type and compare with BlockchainDataClientConfig
Fix the config deserialization so it produces BlockchainDataClientConfig

Example fix

// before
factory.create(name, &other_config, ...) // other_config: BlockchainExecutionClientConfig
// after
let config = BlockchainDataClientConfig { /* ... */ };
factory.create(name, &config, ...)

Defensive patterns

Strategy: type-guard

Validate before calling

if config.as_any().downcast_ref::<BlockchainDataClientConfig>().is_none() {
    panic!("data client factory requires BlockchainDataClientConfig, got {:?}", config);
}

Type guard

fn is_data_client_config(config: &dyn ClientConfig) -> bool {
    config.as_any().downcast_ref::<BlockchainDataClientConfig>().is_some()
}

Try / catch

// wrap factory.create in error context
let client = factory.create(name, &config, ...)
    .map_err(|e| anyhow::anyhow!("data client factory rejected config: {e:#}"))?;

Prevention

Pair each factory registration with its matching config type in a single construction site
Name factory/config pairs consistently (DataClientFactory <-> DataClientConfig)
Add a startup smoke test that builds every registered client with its config

When it happens

Trigger: Calling BlockchainDataClientFactory.create (or the node factory registration path) with a config that is not a BlockchainDataClientConfig instance.

Common situations: Wiring the factory in a node builder but registering a generic/other client's config (e.g. an execution client config or a hand-rolled config struct); copy-pasted factory registration with the wrong config type; config deserialized into the wrong type.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/4f876674c52fa109. Report an issue: GitHub.