serve: trace handler callbacks from the wrapper instead of rooting them as Strong

src/runtime/api/BunObject.rs

@@ -1650,6 +1650,37 @@ pub(crate) fn serve(global_object: &JSGlobalObject, callframe: &CallFrame) -> Js
                 // `server_body` until per-type codegen externs land.
                 <$ServerType>::js_gc_route_list_set(obj, global_object, route_list_object);
             }
+            // Mirror the handler callbacks into the wrapper's WriteBarrier
+            // slots — the wrapper is the sole GC root for these; `ServerConfig`
+            // / `Handler` only hold raw `JSValue` shadows for hot-path dispatch.
+            // The async-context wrap is applied here (not in `from_js`) so the
+            // freshly-allocated wrapper fn is rooted by the slot immediately;
+            // the unwrapped fn is held live by the user's options object on the
+            // `serve()` stack across `init`/`listen` until this point.
+            crate::server::wrap_handler_slot(
+                &mut server_ref.config.on_request,
+                obj,
+                global_object,
+                <$ServerType>::js_gc_on_request_set,
+            );
+            crate::server::wrap_handler_slot(
+                &mut server_ref.config.on_error,
+                obj,
+                global_object,
+                <$ServerType>::js_gc_on_error_set,
+            );
+            crate::server::wrap_handler_slot(
+                &mut server_ref.config.on_node_http_request,
+                obj,
+                global_object,
+                <$ServerType>::js_gc_on_node_http_request_set,
+            );
+            // Skip the 7-slot write when there's no websocket config: the
+            // slots default ZERO so `write_ws_handler_slots`'s clear path
+            // would be 7 wasted FFI calls.
+            if server_ref.config.websocket.is_some() {
+                server_ref.write_ws_handler_slots(obj, global_object);
+            }
             server_ref.js_value.set_strong(obj, global_object);
 
             if global_object.bun_vm().test_isolation_enabled {

src/runtime/bake/DevServer.rs

@@ -1247,6 +1247,10 @@ impl Drop for DevServer {
                     // SAFETY: stored ref from `init_from_any_blob`; no live borrow.
                     unsafe { StaticRoute::deref_(cached.as_ptr()) };
                 }
+                // SAFETY: paired with the `ref_` taken in
+                // `get_or_put_route_bundle` when this bundle was created; the
+                // raw `html_bundle` field has no Drop, so release it here.
+                unsafe { bun_ptr::RefCount::<HTMLBundleRoute>::deref(html.html_bundle) };
             }
         }
 
@@ -5252,13 +5256,13 @@ fn on_request(dev: &mut DevServer, req: &mut Request, mut resp: AnyResponse) {
         return;
     }
 
-    if dev
+    if !dev
         .server
         .as_ref()
         .expect("infallible: server bound")
         .config()
         .on_request
-        .is_some()
+        .is_empty()
     {
         dev.server
             .as_mut()
@@ -5389,8 +5393,8 @@ impl DevServer {
                     let file = &mut self.client_graph.bundled_files.values_mut()
                         [incremental_graph_index.get() as usize];
                     file.html_route_bundle_index = Some(bundle_index);
-                    // Bump the intrusive refcount; matched by
-                    // `RouteBundle::deinit`'s deref of `html_bundle`.
+                    // Bump the intrusive refcount; matched by the
+                    // `html_bundle` deref in `DevServer`'s `Drop`.
                     // SAFETY: `html` is a live IntrusiveRc-managed allocation.
                     unsafe { bun_ptr::RefCount::<HTMLBundleRoute>::ref_(html) };
                     break 'brk route_bundle::Data::Html(route_bundle::Html {

src/runtime/bake/dev_server/route_bundle.rs

@@ -164,8 +164,9 @@ impl RouteBundle {
     }
 }
 
-// `deinit` is fully subsumed by Drop:
-//   - client_bundle / cached_response: Option<Arc<StaticRoute>> drop = .deref()
-//   - Framework: StrongOptional fields drop = .deinit()
-//   - Html: bundled_html_text Box<[u8]> drop = allocator.free()
-//           html_bundle RefPtr drop = .deref()
+// Zig `RouteBundle.deinit` equivalent, split across two mechanisms:
+//   - Drop: `Framework` StrongOptional fields (= .deinit()) and
+//     `Html.bundled_html_text` Box<[u8]> (= allocator.free()).
+//   - `DevServer`'s `Drop` (explicit): `client_bundle`, `Html.cached_response`
+//     (BackRef, no Drop) and `Html.html_bundle` (raw ptr, no Drop) each hold
+//     an intrusive ref that is deref'd there.

src/runtime/server/RequestContext.rs

@@ -3499,12 +3499,10 @@ where
         if let Some(server) = self.server {
             // SAFETY: BACKREF
             let server = &*server;
-            if let Some(on_error) = server.config().on_error.as_ref()
-                && !self.flags.has_called_error_handler()
-            {
+            let on_error = server.config().on_error;
+            if !on_error.is_empty() && !self.flags.has_called_error_handler() {
                 self.flags.set_has_called_error_handler(true);
                 let result = on_error
-                    .get()
                     .call(
                         server.global_this(),
                         server.js_value().try_get().unwrap_or(JSValue::UNDEFINED),

src/runtime/server/ServerConfig.rs

@@ -45,9 +45,12 @@ pub struct ServerConfig {
     /// If HMR is not enabled, then this field is ignored.
     pub enable_chrome_devtools_automatic_workspace_folders: bool,
 
-    pub on_error: Option<Strong>,
-    pub on_request: Option<Strong>,
-    pub on_node_http_request: Option<Strong>,
+    /// Raw shadow of the wrapper's `onError`/`onRequest`/`onNodeHTTPRequest`
+    /// WriteBarrier slots. The wrapper JSCell is the GC root; these are
+    /// `JSValue::ZERO` when unset and copied for hot-path dispatch reads.
+    pub on_error: JSValue,
+    pub on_request: JSValue,
+    pub on_node_http_request: JSValue,
 
     pub websocket: Option<WebSocketServerContext>,
 
@@ -81,9 +84,9 @@ impl Default for ServerConfig {
             development: DevelopmentOption::Development,
             broadcast_console_log_from_browser_to_server_for_bake: false,
             enable_chrome_devtools_automatic_workspace_folders: true,
-            on_error: None,
-            on_request: None,
-            on_node_http_request: None,
+            on_error: JSValue::ZERO,
+            on_request: JSValue::ZERO,
+            on_node_http_request: JSValue::ZERO,
             websocket: None,
             reuse_port: false,
             id: Box::default(),
@@ -274,9 +277,9 @@ impl ServerConfig {
                 .broadcast_console_log_from_browser_to_server_for_bake,
             enable_chrome_devtools_automatic_workspace_folders: self
                 .enable_chrome_devtools_automatic_workspace_folders,
-            on_error: self.on_error.take(),
-            on_request: self.on_request.take(),
-            on_node_http_request: self.on_node_http_request.take(),
+            on_error: self.on_error,
+            on_request: self.on_request,
+            on_node_http_request: self.on_node_http_request,
             websocket: self.websocket.take(),
             reuse_port: self.reuse_port,
             id: core::mem::take(&mut self.id),
@@ -1313,8 +1316,10 @@ impl ServerConfig {
                     global.throw_invalid_arguments(format_args!("Expected error to be a function"))
                 );
             }
-            let on_error_snapshot = on_error.with_async_context_if_needed(global);
-            args.on_error = Some(Strong::create(on_error_snapshot, global));
+            // Raw value — async-context wrapping is deferred to the slot-write
+            // site (`serve_with!` / `on_reload_from_zig`) so the wrapped fn is
+            // rooted by the wrapper's WriteBarrier slot the moment it exists.
+            args.on_error = on_error;
         }
         if global.has_exception() {
             return Err(JsError::Thrown);
@@ -1326,19 +1331,17 @@ impl ServerConfig {
                     "Expected onNodeHTTPRequest to be a function",
                 )));
             }
-            let on_request = on_request_.with_async_context_if_needed(global);
-            args.on_node_http_request = Some(Strong::create(on_request, global));
+            args.on_node_http_request = on_request_;
         }
 
         if let Some(on_request_) = arg.get_truthy(global, "fetch")? {
             if !on_request_.is_callable() {
                 return Err(global
                     .throw_invalid_arguments(format_args!("Expected fetch() to be a function")));
             }
-            let on_request = on_request_.with_async_context_if_needed(global);
-            args.on_request = Some(Strong::create(on_request, global));
+            args.on_request = on_request_;
         } else if args.bake.is_none()
-            && args.on_node_http_request.is_none()
+            && args.on_node_http_request.is_empty()
             && ((args.static_routes.len() + args.user_routes_to_build.len()) == 0
                 && !opts.has_user_routes)
             && opts.is_fetch_required

src/runtime/server/ServerWebSocket.rs

@@ -147,9 +147,9 @@ impl Flags {
 // (`generate-classes.ts` → `${T}__data{Get,Set}Cached`).
 #[allow(non_snake_case)]
 pub mod js {
-    // Emits `data_{get,set}_cached`. Getter maps `JSValue::ZERO` → `None`;
+    // Emits `{data,server}_{get,set}_cached`. Getter maps `JSValue::ZERO` → `None`;
     // setter forwards through the JSC `WriteBarrier<Unknown>` slot.
-    ::bun_jsc::codegen_cached_accessors!("ServerWebSocket"; data);
+    ::bun_jsc::codegen_cached_accessors!("ServerWebSocket"; data, server);
 }
 
 /// Maps a uWS `SendStatus` to the JS-visible number contract shared by every
@@ -356,6 +356,12 @@ impl ServerWebSocket {
             .this_value
             .set(JsRef::init_strong(this_value, global_object));
         js::data_set_cached(this_value, global_object, data_value);
+        // Only mirror the server wrapper while it is strongly rooted —
+        // `js_value()` would return a weak (potentially dead-but-unswept)
+        // address once the server has gone idle and downgraded.
+        if let Some(server_js) = handler.server.and_then(|s| s.js_value_for_dispatch()) {
+            js::server_set_cached(this_value, global_object, server_js);
+        }
         this
     }
 
@@ -383,8 +389,12 @@ impl ServerWebSocket {
 
         let handler = self.handler();
         let vm = handler.vm();
-        // The handler is shared (&), so mutate via the interior-mutability helper.
-        handler.active_connections_saturating_add(1);
+        // Live-socket accounting lives on the server (`Cell`), reached
+        // through the type-erased backref so the shared `&Handler` suffices.
+        let server = handler.server;
+        if let Some(server) = server {
+            server.on_websocket_opened();
+        }
         let global_object = handler.global_object();
         let on_open_handler = handler.on_open;
         if vm.is_shutting_down() {
@@ -421,17 +431,26 @@ impl ServerWebSocket {
         if let Some(err_value) = result.to_error() {
             bun_output::scoped_log!(WebSocketServer, "onOpen exception");
 
+            let mut closed_here = false;
             if !self.flags.get().closed() {
                 self.update_flags(|f| f.set_closed(true));
                 // we un-gracefully close the connection if there was an exception
                 // we don't want any event handlers to fire after this for anything other than error()
                 // https://github.com/oven-sh/bun/issues/1480
+                // (`close()` re-enters `on_close`, which skips its own
+                // accounting because the closed flag is already set.)
                 self.websocket().close();
-                handler.active_connections_saturating_sub(1);
+                closed_here = true;
                 this_value.unprotect();
             }
 
             handler.run_error_callback(vm, global_object, err_value);
+            if closed_here {
+                if let Some(server) = server {
+                    // May run the idle pass; no `&Handler` borrow is live here.
+                    server.on_websocket_closed();
+                }
+            }
         }
     }
 
@@ -523,7 +542,8 @@ impl ServerWebSocket {
             return;
         }
 
-        if !handler.on_drain.is_empty() {
+        let on_drain = handler.on_drain;
+        if !on_drain.is_empty() {
             let global_object = handler.global_object();
 
             let args = [self
@@ -535,7 +555,7 @@ impl ServerWebSocket {
                 args: &args,
                 global_object,
                 this_value: JSValue::ZERO,
-                callback: handler.on_drain,
+                callback: on_drain,
                 result: JSValue::ZERO,
             };
             let _loop_guard = vm.enter_event_loop_scope();
@@ -628,11 +648,18 @@ impl ServerWebSocket {
         bun_output::scoped_log!(WebSocketServer, "onClose");
         // TODO: Can this called inside finalize?
         let handler = self.handler();
+        // Copy the erased server handle out now: the guard below runs after
+        // every `handler` borrow has expired, and `on_websocket_closed` may
+        // form `&mut NewServer` (which owns the handler storage) to run the
+        // idle pass when this was the last live socket.
+        let server = handler.server;
         let was_closed = self.is_closed();
         self.update_flags(|f| f.set_closed(true));
         scopeguard::defer! {
             if !was_closed {
-                handler.active_connections_saturating_sub(1);
+                if let Some(server) = server {
+                    server.on_websocket_closed();
+                }
             }
         }
         let signal = self.signal.take();
@@ -668,7 +695,10 @@ impl ServerWebSocket {
             return;
         }
 
-        if !handler.on_close.is_empty_or_undefined_or_null() {
+        // Copy to a stack local before `sig.signal()` re-enters JS: a GC
+        // between the test and the `.call(...)` could otherwise collect it.
+        let on_close_handler = handler.on_close;
+        if !on_close_handler.is_empty_or_undefined_or_null() {
             let global_object = handler.global_object();
 
             let _loop_guard = vm.enter_event_loop_scope();
@@ -697,10 +727,7 @@ impl ServerWebSocket {
             };
 
             let call_args = [cached_this, JSValue::js_number(code as f64), message_js];
-            if let Err(e) = handler
-                .on_close
-                .call(global_object, JSValue::UNDEFINED, &call_args)
-            {
+            if let Err(e) = on_close_handler.call(global_object, JSValue::UNDEFINED, &call_args) {
                 let err = global_object.take_exception(e);
                 bun_output::scoped_log!(WebSocketServer, "onClose error {}", was_not_empty);
                 handler.run_error_callback(vm, global_object, err);
@@ -1344,8 +1371,22 @@ impl ServerWebSocket {
             break 'brk args.ptr[1].to_slice_or_null(global_this)?;
         };
 
+        // `to_slice_or_null` can run user `toString()`, which may re-entrantly
+        // `ws.close()` and already decrement the count; re-check the guard.
+        if self.is_closed() {
+            return Ok(JSValue::UNDEFINED);
+        }
+
+        // Copy the server backref BEFORE end(): on_close re-enters and the
+        // user's close handler may call stop(true), which clears handler.server.
+        let server = self.handler().server;
         self.update_flags(|f| f.set_closed(true));
         self.websocket().end(code, message_value.slice());
+        // on_close re-entered with was_closed=true so it skipped the
+        // accounting; balance the count here.
+        if let Some(server) = server {
+            server.on_websocket_closed();
+        }
         Ok(JSValue::UNDEFINED)
     }
 
@@ -1363,8 +1404,16 @@ impl ServerWebSocket {
             return Ok(JSValue::UNDEFINED);
         }
 
+        // Copy the server backref BEFORE close(): on_close re-enters and the
+        // user's close handler may call stop(true), which clears handler.server.
+        let server = self.handler().server;
         self.update_flags(|f| f.set_closed(true));
         self.websocket().close();
+        // on_close re-entered with was_closed=true so it skipped the
+        // accounting; balance the count here.
+        if let Some(server) = server {
+            server.on_websocket_closed();
+        }
 
         Ok(JSValue::UNDEFINED)
     }