From 148008c6954087c7be1382f6176a5d6bc9ef633f Mon Sep 17 00:00:00 2001
From: Dennis Kobert <dennis@kobert.dev>
Date: Tue, 8 Sep 2026 13:15:18 +0000
Subject: [PATCH] Refuse a wasm threads build where the Send and Sync impls
 assume one thread

---
 node-graph/libraries/core-types/src/registry.rs | 3 +++
 node-graph/libraries/core-types/src/runtime.rs  | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/node-graph/libraries/core-types/src/registry.rs b/node-graph/libraries/core-types/src/registry.rs
index d5b106996c..d8c7610245 100644
--- a/node-graph/libraries/core-types/src/registry.rs
+++ b/node-graph/libraries/core-types/src/registry.rs
@@ -217,6 +217,9 @@ unsafe impl Send for SourceHandle {}
 #[cfg(target_family = "wasm")]
 unsafe impl Sync for SourceHandle {}
 
+#[cfg(all(target_family = "wasm", target_feature = "atomics"))]
+compile_error!("SourceHandle's wasm Send/Sync rest on a single-threaded build; a +atomics target needs the stored node bounded instead");
+
 impl SourceHandle {
 	pub fn new_record<T: 'static>(node: std::sync::Arc<ErasedRecordNode>) -> Self {
 		Self::new_erased(node, record_source_type::<T>())
diff --git a/node-graph/libraries/core-types/src/runtime.rs b/node-graph/libraries/core-types/src/runtime.rs
index 77e0d65f92..28345ea062 100644
--- a/node-graph/libraries/core-types/src/runtime.rs
+++ b/node-graph/libraries/core-types/src/runtime.rs
@@ -30,6 +30,9 @@ unsafe impl Send for RuntimeHandle {}
 #[cfg(target_family = "wasm")]
 unsafe impl Sync for RuntimeHandle {}
 
+#[cfg(all(target_family = "wasm", target_feature = "atomics"))]
+compile_error!("RuntimeHandle's wasm Send/Sync rest on a single-threaded build; a +atomics target needs the payload bounded instead");
+
 impl std::fmt::Debug for RuntimeHandle {
 	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
 		f.debug_struct("RuntimeHandle").finish_non_exhaustive()
@@ -102,6 +105,9 @@ unsafe impl<S> Send for GraphRuntime<S> {}
 #[cfg(target_family = "wasm")]
 unsafe impl<S> Sync for GraphRuntime<S> {}
 
+#[cfg(all(target_family = "wasm", target_feature = "atomics"))]
+compile_error!("GraphRuntime's wasm Send/Sync are unbounded in S and rest on a single-threaded build; a +atomics target needs S bounded instead");
+
 impl<S> GraphRuntime<S> {
 	pub fn new(spawner: S) -> Self {
 		Self {