From d5088835a78bf3f9249a172b1729e0046e2cb7ed Mon Sep 17 00:00:00 2001
From: Aaron Queen <bompus@gmail.com>
Date: Fri, 4 Sep 2026 03:06:56 -0600
Subject: [PATCH] fix(wxt): tolerate the content script reload race in MV3 dev

---
 .../virtual/utils/reload-content-scripts.ts   | 29 +++++++++++++++----
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/packages/wxt/src/virtual/utils/reload-content-scripts.ts b/packages/wxt/src/virtual/utils/reload-content-scripts.ts
index 5d3b4363e..ccfbc1b5d 100644
--- a/packages/wxt/src/virtual/utils/reload-content-scripts.ts
+++ b/packages/wxt/src/virtual/utils/reload-content-scripts.ts
@@ -46,13 +46,30 @@ export async function reloadManifestContentScriptMv3(
     ]);
   } else {
     logger.debug('Registering new content script...');
-    await browser.scripting.registerContentScripts([
-      {
-        ...contentScript,
+    try {
+      await browser.scripting.registerContentScripts([
+        {
+          ...contentScript,
+          id,
+          css: contentScript.css ?? [],
+        },
+      ]);
+    } catch (err) {
+      // Two reload events for the same entrypoint can both read an empty
+      // registration above and both register; the loser throws "Duplicate
+      // script ID". The winner is registering this same script and reloads
+      // the tabs once it lands, so the loser has nothing left to do. It must
+      // not fall back to updateContentScripts (the winner's registration is
+      // not complete yet, so that throws "not fully registered") and must not
+      // reload tabs (they would come back before the script is registered).
+      const message = String((err as Error)?.message ?? err);
+      if (!message.includes('Duplicate script ID')) throw err;
+      logger.debug(
+        'Lost a registration race, the concurrent register owns it',
         id,
-        css: contentScript.css ?? [],
-      },
-    ]);
+      );
+      return;
+    }
   }
 
   await reloadTabsForContentScript(contentScript);