dbt-labs/dbt-core · error · syn::Error

The runtime flavor `multi_thread` requires the `rt-multi-thr

Error message

The runtime flavor `multi_thread` requires the `rt-multi-thread` feature.

What it means

When flavor = "multi_thread" is explicitly requested but the `rt-multi-thread` cargo feature is not compiled in, the runtime Builder type does not exist, so the macro fails compilation with this message at Span::call_site(). This is the branch of the same check as error 478, taken when the user explicitly set the flavor.

Source

Thrown at crates/dbt-runtime-macros/src/entry.rs:227

        let worker_threads = match (flavor, self.worker_threads) {
            (F::CurrentThread | F::Local, Some((_, worker_threads_span))) => {
                let msg = format!(
                    "The `worker_threads` option requires the `multi_thread` runtime flavor. Use `#[{}(flavor = \"multi_thread\")]`",
                    self.macro_name(),
                );
                return Err(syn::Error::new(worker_threads_span, msg));
            }
            (F::CurrentThread | F::Local, None) => None,
            (F::Threaded, worker_threads) if self.rt_multi_thread_available => {
                worker_threads.map(|(val, _span)| val)
            }
            (F::Threaded, _) => {
                let msg = if self.flavor.is_none() {
                    "The default runtime flavor is `multi_thread`, but the `rt-multi-thread` feature is disabled."
                } else {
                    "The runtime flavor `multi_thread` requires the `rt-multi-thread` feature."
                };
                return Err(syn::Error::new(Span::call_site(), msg));
            }
        };

        let start_paused = match (flavor, self.start_paused) {
            (F::Threaded, Some((_, start_paused_span))) => {
                let msg = format!(
                    "The `start_paused` option requires the `current_thread` runtime flavor. Use `#[{}(flavor = \"current_thread\")]`",
                    self.macro_name(),
                );
                return Err(syn::Error::new(start_paused_span, msg));
            }
            (F::CurrentThread | F::Local, Some((start_paused, _))) => Some(start_paused),
            (_, None) => None,
        };

        let unhandled_panic = match (flavor, self.unhandled_panic) {
            (F::Threaded, Some((_, unhandled_panic_span))) => {
                let msg = format!(

View on GitHub (pinned to 0267ce9170)

Solutions

1. Add the feature: tokio = { version = "1", features = ["rt-multi_thread", "macros"] } — note the exact name is `rt-multi-thread`
2. Verify with cargo tree -e features that rt-multi-thread is enabled for tokio
3. Switch to flavor = "current_thread" if a single-threaded runtime suffices

Example fix

// before
#[tokio::main(flavor = "multi_thread")]
async fn main() {}
// Cargo.toml: tokio = { version = "1", default-features = false, features = ["rt", "macros"] }

// after
// Cargo.toml: tokio = { version = "1", default-features = false, features = ["rt", "rt-multi-thread", "macros"] }
#[tokio::main(flavor = "multi_thread")]
async fn main() {}

fn assert_flavor_supported(features: &[&str], flavor: &str) -> Result<(), String> {
    if flavor == "multi_thread" && !features.contains(&"rt-multi-thread") {
        Err("flavor multi_thread requires tokio feature `rt-multi-thread`".into())
    } else { Ok(()) }
}

When it happens

Trigger: #[tokio::main(flavor = "multi_thread")] (or #[tokio::test(flavor = "multi_thread")]) while the tokio crate dependency does not include the `rt-multi-thread` feature.

Common situations: Disabling default features in Cargo.toml; CI builds testing no-default-features; a workspace where feature unification leaves tokio without rt-multi-thread; docs examples copied without feature instructions.

Related errors

• The default runtime flavor is `multi_thread`, but the `rt-mu
• No such runtime flavor `{s}`. The runtime flavors are `curre
• No such unhandled panic behavior `{s}`. The unhandled panic
• The `start_paused` option requires the `current_thread` runt
• The `unhandled_panic` option requires the `current_thread` r

AI-assisted analysis of dbt-labs/dbt-core@0267ce9170 (2026-09-07). Data as JSON: /api/errors/4890de550f11ef19. Report an issue: GitHub.