diff --git a/cmd/tsconnect/wasm/wasm_js.go b/cmd/tsconnect/wasm/wasm_js.go
index 67208be18..4d6a7c057 100644
--- a/cmd/tsconnect/wasm/wasm_js.go
+++ b/cmd/tsconnect/wasm/wasm_js.go
@@ -625,6 +625,11 @@ func (i *jsIPN) logout() {
 	}()
 }
 
+// shutdown tears down the backend and lets main return, which exits the whole
+// Go runtime. Callers should await the runtime's exit rather than the promise
+// returned here: closing shutdownCh races with makePromise resolving, so the
+// promise may never settle. There is exactly one IPN per runtime, so the once
+// and the channel belong to the same instance and a second call is a no-op.
 func (i *jsIPN) shutdown() js.Value {
 	return makePromise(func() (any, error) {
 		i.shutdownOnce.Do(func() {