Invalid config type for PolymarketExecutionClientFactory. Ex

Error message

Invalid config type for PolymarketExecutionClientFactory. Expected PolymarketExecutionClientConfig, was {config:?}

What it means

PolymarketExecutionClientFactory::create only accepts a config object of concrete type PolymarketExecutionClientConfig. It attempts a downcast of the passed trait-object config and returns this anyhow error when the downcast fails, meaning a config of another client's type (or the data-client config) was supplied to the execution factory.

Source

Thrown at crates/adapters/polymarket/src/factories.rs:186

    feature = "python",
    pyo3_stub_gen::derive::gen_stub_pyclass(module = "nautilus_trader.adapters.polymarket")
)]
#[derive(Debug, Clone)]
pub struct PolymarketExecutionClientFactory;

impl ExecutionClientFactory for PolymarketExecutionClientFactory {
    fn create(
        &self,
        trader_id: TraderId,
        name: &str,
        config: &dyn ClientConfig,
        cache: CacheView,
    ) -> anyhow::Result<Box<dyn ExecutionClient>> {
        let polymarket_config = config
            .as_any()
            .downcast_ref::<PolymarketExecutionClientConfig>()
            .ok_or_else(|| {
                anyhow::anyhow!(
                    "Invalid config type for PolymarketExecutionClientFactory. Expected PolymarketExecutionClientConfig, was {config:?}",
                )
            })?
            .clone();

        let oms_type = OmsType::Netting;
        let account_type = AccountType::Cash;

        let client_id = ClientId::from(name);
        let core = ExecutionClientCore::new(
            trader_id,
            client_id,
            *POLYMARKET_VENUE,
            oms_type,
            polymarket_config.account_id,
            account_type,
            None, // base_currency
            cache,

View on GitHub (pinned to 18893faf8b)

Solutions

Construct and pass a PolymarketExecutionClientConfig (parse it from your config section with its deserializer).
Check that the factory registration pairs PolymarketExecutionClientFactory with PolymarketExecutionClientConfig, not the data client's config.
If using a generic config enum/registry, verify which variant is routed to the execution factory before calling create.

Example fix

// before
let client = exec_factory.create(data_config, cache).unwrap();
// after
let exec_config = config.as_any().downcast_ref::<PolymarketExecutionClientConfig>()
    .expect("execution factory requires PolymarketExecutionClientConfig").clone();
let client = exec_factory.create(exec_config, cache).unwrap();

Defensive patterns

Strategy: type-guard

Validate before calling

fn is_polymarket_exec_config(config: &dyn ClientConfig) -> bool {
    config.as_any().is::<PolymarketExecutionClientConfig>()
}

Type guard

fn as_polymarket_exec_config(config: &dyn ClientConfig) -> Option<&PolymarketExecutionClientConfig> {
    config.as_any().downcast_ref::<PolymarketExecutionClientConfig>()
}

Try / catch

match config.as_any().downcast_ref::<PolymarketExecutionClientConfig>() {
    Some(c) => factory.create(c.clone(), cache)?,
    None => bail!("wrong config type for PolymarketExecutionClientFactory: {:?}", config),
}

Prevention

Always build execution client configs via PolymarketExecutionClientConfig, never reuse the data client's config struct.
Pair factory and config types in one registration site so they cannot drift.
Add a unit test per factory asserting it rejects the wrong config type.

When it happens

Trigger: Calling PolymarketExecutionClientFactory::create with e.g. PolymarketDataClientConfig, a different adapter's ExecutionClientConfig, or any config not built via PolymarketExecutionClientConfig.

Common situations: Copy-pasting factory wiring between data and execution client setup, registering the wrong config with a generic factory registry, or swapping config structs after a refactor.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/b50dfa8b6ca458ba. Report an issue: GitHub.