What causes "Test connection not supported for this trigger type" in windmill-labs/windmill?

Don't call test_connection for this trigger kind; verify the trigger is activated and processing events instead

Test connection not supported for this trigger type

Error message

Test connection not supported for this trigger type

What it means

Trigger types in Windmill implement a TestConnection trait; types that have no meaningful connectivity probe (e.g. static or schedule-derived triggers) use this default implementation which always returns an error. Calling the test-connection endpoint on such a trigger type always fails with this message.

Source

Thrown at backend/windmill-trigger/src/handler.rs:176

        &self,
        db: &DB,
        tx: &mut PgConnection,
        authed: &ApiAuthed,
        workspace_id: &str,
        path: &str,
        trigger: TriggerData<Self::TriggerConfigRequest>,
    ) -> Result<()>;

    async fn test_connection(
        &self,
        _db: &DB,
        _authed: &ApiAuthed,
        _user_db: &UserDB,
        _workspace_id: &str,
        _config: Self::TestConnectionConfig,
    ) -> Result<()> {
        Err(
            anyhow::anyhow!("Test connection not supported for this trigger type".to_string(),)
                .into(),
        )
    }

    fn additional_routes(&self) -> axum::Router {
        axum::Router::new()
    }

    async fn get_trigger_by_path(
        &self,
        tx: &mut PgConnection,
        workspace_id: &str,
        path: &str,
    ) -> Result<Self::Trigger> {
        let mut fields = vec![
            "workspace_id",
            "path",
            "script_path",

View on GitHub (pinned to e474e8803c)

Solutions

Don't call test_connection for this trigger kind; verify the trigger is activated and processing events instead
Check the specific trigger type's docs for the correct health-check mechanism
If testing is genuinely needed, implement the test_connection override for that trigger type in windmill-trigger/src/handler.rs

Defensive patterns

Strategy: try-catch

Validate before calling

// consult the trigger type's capabilities before calling:
const SUPPORTS_TEST_CONNECTION = new Set(["http", "email", "s3", "kafka", "nats"]);

Try / catch

match client.test_connection(ws, trigger_path) {
    Ok(res) => println!("connected: {:?}", res),
    Err(e) if e.to_string().contains("not supported") => println!("skip: test_connection unsupported for this trigger kind"),
    Err(e) => return Err(e),
}

Prevention

Check whether the trigger kind implements test_connection before calling the endpoint
Use trigger activation state/logs as the health signal for unsupported kinds
Treat this specific message as 'unsupported operation', not a real connectivity failure

When it happens

Trigger: POSTing to the trigger test-connection endpoint (POST /api/w/{workspace}/triggers/{kind}/.../test_connection) for a trigger kind whose trait impl delegates to this base handler, e.g. websocket or other kinds without an override.

Common situations: Users clicking a 'Test connection' button in the UI for trigger types that don't support it; API clients running health-check scripts that assume all trigger kinds support the probe.

Related errors

AI-assisted analysis of windmill-labs/windmill@e474e8803c (2026-09-03). Data as JSON: /api/errors/82b8565f1754b258. Report an issue: GitHub.