feat: serve SvelteKit env.js for dynamic environment variables

src/assets.rs

@@ -7,6 +7,7 @@ use include_dir::{Dir, include_dir};
 static CLIENT_ASSETS: Dir = include_dir!("$CARGO_MANIFEST_DIR/web/build/client");
 static ERROR_PAGES: Dir = include_dir!("$CARGO_MANIFEST_DIR/web/build/prerendered/errors");
 static PRERENDERED_PAGES: Dir = include_dir!("$CARGO_MANIFEST_DIR/web/build/prerendered");
+static ENV_JS: &[u8] = include_bytes!(concat!(env!("CARGO_MANIFEST_DIR"), "/web/build/env.js"));
 
 pub async fn serve_embedded_asset(uri: Uri) -> Response {
     let path = uri.path();
@@ -86,6 +87,14 @@ pub fn get_error_page(status_code: u16) -> Option<&'static [u8]> {
     ERROR_PAGES.get_file(&filename).map(|f| f.contents())
 }
 
+/// Get the embedded SvelteKit env.js file for dynamic public environment variables.
+///
+/// SvelteKit generates this file when using `$env/dynamic/public` imports.
+/// It must be served at `/_app/env.js` for prerendered pages to hydrate correctly.
+pub fn get_env_js() -> &'static [u8] {
+    ENV_JS
+}
+
 /// Serve prerendered content by path, if it exists.
 ///
 /// Prerendered content is built by SvelteKit at compile time and embedded.

src/handlers/assets.rs

@@ -8,6 +8,22 @@ use std::sync::Arc;
 
 use crate::{assets, proxy, state::AppState, utils};
 
+/// Serve SvelteKit's env.js for dynamic public environment variables.
+/// Required for prerendered pages that use `$env/dynamic/public` imports.
+pub async fn serve_env_js() -> impl IntoResponse {
+    let mut headers = HeaderMap::new();
+    headers.insert(
+        axum::http::header::CONTENT_TYPE,
+        axum::http::HeaderValue::from_static("application/javascript; charset=utf-8"),
+    );
+    headers.insert(
+        axum::http::header::CACHE_CONTROL,
+        axum::http::HeaderValue::from_static("public, max-age=3600"),
+    );
+
+    (StatusCode::OK, headers, assets::get_env_js())
+}
+
 /// Serve PGP public key
 pub async fn serve_pgp_key() -> impl IntoResponse {
     if let Some(content) = assets::get_static_file("publickey.asc") {

src/routes.rs

@@ -77,6 +77,8 @@ pub fn build_base_router() -> Router<Arc<AppState>> {
     Router::new()
         .nest("/api", api_routes())
         .route("/api/", any(api_root_404_handler))
+        // Serve env.js explicitly before the wildcard (it's at build root, not in client/)
+        .route("/_app/env.js", get(handlers::serve_env_js))
         .route(
             "/_app/{*path}",
             get(assets::serve_embedded_asset).head(assets::serve_embedded_asset),