Support checking react 19 components (#12948)

2 files changed, 10 insertions, 1 deletions

diff --git a/.changeset/sweet-turtles-flash.md b/.changeset/sweet-turtles-flash.md
new file mode 100644
index 000000000..e15e055e1
--- /dev/null
+++ b/.changeset/sweet-turtles-flash.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/react': patch
+---
+
+Supports checking for React 19 components
diff --git a/packages/integrations/react/server.js b/packages/integrations/react/server.js
index 9c3c309cc..50d6bd94b 100644
--- a/packages/integrations/react/server.js
+++ b/packages/integrations/react/server.js
@@ -6,6 +6,7 @@ import StaticHtml from './static-html.js';
 
 const slotName = (str) => str.trim().replace(/[-_]([a-z])/g, (_, w) => w.toUpperCase());
 const reactTypeof = Symbol.for('react.element');
+const reactTransitionalTypeof = Symbol.for('react.transitional.element');
 
 async function check(Component, props, children) {
 	// Note: there are packages that do some unholy things to create "components".
@@ -28,7 +29,10 @@ async function check(Component, props, children) {
 	function Tester(...args) {
 		try {
 			const vnode = Component(...args);
-			if (vnode && vnode['$$typeof'] === reactTypeof) {
+			if (
+				vnode &&
+				(vnode['$$typeof'] === reactTypeof || vnode['$$typeof'] === reactTransitionalTypeof)
+			) {
 				isReactComponent = true;
 			}
 		} catch {}