leptos-rs/leptos · critical

Unsupported server function HTTP method

Error message

Unsupported server function HTTP method: {method:?}

What it means

leptos's Axum integration builds a route for each server function based on the HTTP method stored in the server function's metadata. Only GET, POST, PUT, DELETE, and PATCH are mapped to Axum's method routers; any other method causes an immediate panic while constructing the router.

Solutions

1. Change the server function to use GET, POST, PUT, DELETE, or PATCH (the default is POST).
2. If a custom method is truly required, add a match arm mapping it to the corresponding Axum method-router helper before the catch-all panic.
3. Verify the config passed to #[server(...)] (e.g. `method = ...`) only uses supported verbs.

Example fix

// before
#[server(FetchThing, "/api")]
#[cfg_attr(feature = "ssr", server(method = HEAD))]
async fn fetch_thing() -> Result<(), ServerFnError> { ... }
// after
#[server(FetchThing, "/api")]
#[cfg_attr(feature = "ssr", server(method = GET))]
async fn fetch_thing() -> Result<(), ServerFnError> { ... }

const SUPPORTED: &[&str] = &["GET", "POST", "PUT", "DELETE", "PATCH"];
fn server_fn_method_supported(method: &str) -> bool {
    SUPPORTED.contains(&method.to_uppercase().as_str())
}

fn is_supported_method(m: &http::Method) -> bool {
    matches!(m, &http::Method::GET | &http::Method::POST | &http::Method::PUT | &http::Method::DELETE | &http::Method::PATCH)
}

When it happens

Trigger: Calling LeptosRoutes::leptos_routes/leptos_routes_with_context on an Axum router when a registered server function declares an HTTP method outside the supported set (e.g. via custom #[server] macro configuration setting method to HEAD or OPTIONS).

Common situations: Customizing server function methods with non-standard verbs; hand-written or generated server function registrations with typos in the method; using a macro or codegen that emits methods Axum routing helpers here don't cover.

Related errors

• Failed to find the route
• at , the `sandboxed-arenas` feature is active, but no Arena…
• {}
• Failed to create HeaderValue
• failed to spawn future on ThreadPool

AI-assisted analysis of leptos-rs/leptos@32d20f6c9d (2026-09-01). Data as JSON: /api/errors/a2b9ff1de8b89d09. Report an issue: GitHub.

Appendix: source

Thrown at integrations/axum/src/lib.rs:1842

        // register server functions
        for (path, method) in server_fn::axum::server_fn_paths() {
            let cx_with_state = cx_with_state.clone();
            let handler = move |req: Request<Body>| async move {
                handle_server_fns_with_context(cx_with_state, req).await
            };

            if !excluded.contains(path) {
                router = router.route(
                    path,
                    match method {
                        Method::GET => get(handler),
                        Method::POST => post(handler),
                        Method::PUT => put(handler),
                        Method::DELETE => delete(handler),
                        Method::PATCH => patch(handler),
                        _ => {
                            panic!(
                                "Unsupported server function HTTP method: \
                                 {method:?}"
                            );
                        }
                    },
                );
            }
        }

        // register router paths
        for listing in paths.iter().filter(|p| !p.exclude) {
            let path = listing.path();

            for method in listing.methods() {
                let cx_with_state = cx_with_state.clone();
                let cx_with_state_and_method = move || {
                    provide_context(method);
                    cx_with_state();

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