Invalid config type for LighterDataClientFactory. Expected L

Error message

Invalid config type for LighterDataClientFactory. Expected LighterDataClientConfig, was {config:?}

What it means

LighterDataClientFactory::create accepts a generic config object and downcasts it to LighterDataClientConfig. If the passed config is any other type (usually another venue's config or a miswired factory/config pairing), the downcast fails and this error is raised naming the expected and actual types.

Source

Thrown at crates/adapters/lighter/src/factories.rs:83

    #[must_use]
    pub const fn new() -> Self {
        Self
    }
}

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

        let client_id = ClientId::from(name);
        let client = LighterDataClient::new(client_id, lighter_config)?;
        Ok(Box::new(client))
    }

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

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

View on GitHub (pinned to 18893faf8b)

Solutions

Pass a LighterDataClientConfig (deserialize the config section with the Lighter type) when using LighterDataClientFactory.
Check the config source: ensure the config section key actually contains Lighter settings, not another venue's.
Confirm the factory registered under the given name is the Lighter factory and matches the config type.
In tests, construct the config with the correct type for the factory under test.

Example fix

// before
let config = DeribitDataClientConfig::default();
let factory = LighterDataClientFactory::default();
factory.create("lighter", &config, ...)?; // fails: type mismatch
// after
let config = LighterDataClientConfig::default();
let factory = LighterDataClientFactory::default();
factory.create("lighter", &config, ...)?;

Defensive patterns

Strategy: type-guard

Validate before calling

let lighter_cfg = config.as_any().downcast_ref::<LighterDataClientConfig>();
if lighter_cfg.is_none() { /* wrong config type; fix wiring before create */ }

Type guard

fn is_lighter_data_config(config: &dyn UserConfig) -> bool {
    config.as_any().downcast_ref::<LighterDataClientConfig>().is_some()
}

Try / catch

match factory.create(name, config, clock) {
    Err(e) if e.to_string().contains("Invalid config type for LighterDataClientFactory") => {
        // inspect config type; rebuild with LighterDataClientConfig
    }
    other => other,
}

Prevention

Pair each factory with its matching config type at registration time
Type-check the config before calling create in builder code and tests
Avoid sharing one config object across venue factories in tests

When it happens

Trigger: Registering the Lighter data client factory but passing a different venue's config (e.g. DeribitDataClientConfig) to add_data_client, or a test/test-fixture reusing the wrong config type — as in test_deribit_data_client_factory_creates_client which fed a non-Lighter config into create.

Common situations: Copy-pasted node/config builders where the factory name and config type don't match; config parsed from a file that maps to the wrong adapter; tests using a shared config object across venues.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/417a5d15b91094bd. Report an issue: GitHub.