From 0007d3c337dc7dec7faf0d1d3dfc55eada85b3ed Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 25 Feb 2026 20:08:49 +0000
Subject: [PATCH 1/3] Initial plan


From 160be3d31b251e2ac5bace1b45b0cfb145e41e36 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 25 Feb 2026 20:28:55 +0000
Subject: [PATCH 2/3] Fix COMPUTED_GETTERS always initialized as WeakSet to
 prevent TypeError in Firefox

Co-authored-by: NullVoxPopuli <199018+NullVoxPopuli@users.noreply.github.com>
---
 packages/@ember/-internals/metal/lib/decorator.ts | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/packages/@ember/-internals/metal/lib/decorator.ts b/packages/@ember/-internals/metal/lib/decorator.ts
index 3e6b262f3bc..098ddc1c61b 100644
--- a/packages/@ember/-internals/metal/lib/decorator.ts
+++ b/packages/@ember/-internals/metal/lib/decorator.ts
@@ -75,11 +75,7 @@ export abstract class ComputedDescriptor {
   abstract set(obj: object, keyName: string, value: any | null | undefined): any | null | undefined;
 }
 
-export let COMPUTED_GETTERS: WeakSet<() => unknown>;
-
-if (import.meta.env?.DEV) {
-  COMPUTED_GETTERS = new WeakSet();
-}
+export const COMPUTED_GETTERS = new WeakSet<() => unknown>();
 
 function DESCRIPTOR_GETTER_FUNCTION(name: string, descriptor: ComputedDescriptor): () => unknown {
   function getter(this: object): unknown {

From 462a664904e50a4e420520b51be7087ab2c56c65 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 25 Feb 2026 20:42:27 +0000
Subject: [PATCH 3/3] Fix Firefox test build: add import.meta.env?.DEV
 replacement plugin to vite.config.mjs

Co-authored-by: NullVoxPopuli <199018+NullVoxPopuli@users.noreply.github.com>
---
 packages/@ember/-internals/metal/lib/decorator.ts |  6 +++++-
 vite.config.mjs                                   | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/packages/@ember/-internals/metal/lib/decorator.ts b/packages/@ember/-internals/metal/lib/decorator.ts
index 098ddc1c61b..3e6b262f3bc 100644
--- a/packages/@ember/-internals/metal/lib/decorator.ts
+++ b/packages/@ember/-internals/metal/lib/decorator.ts
@@ -75,7 +75,11 @@ export abstract class ComputedDescriptor {
   abstract set(obj: object, keyName: string, value: any | null | undefined): any | null | undefined;
 }
 
-export const COMPUTED_GETTERS = new WeakSet<() => unknown>();
+export let COMPUTED_GETTERS: WeakSet<() => unknown>;
+
+if (import.meta.env?.DEV) {
+  COMPUTED_GETTERS = new WeakSet();
+}
 
 function DESCRIPTOR_GETTER_FUNCTION(name: string, descriptor: ComputedDescriptor): () => unknown {
   function getter(this: object): unknown {
diff --git a/vite.config.mjs b/vite.config.mjs
index 57b0ca0b314..e044c6a7723 100644
--- a/vite.config.mjs
+++ b/vite.config.mjs
@@ -34,6 +34,21 @@ export default defineConfig(({ mode }) => {
   return {
     plugins: [
       templateTag(),
+      {
+        name: 'define custom import.meta.env',
+        transform(code) {
+          if (mode === 'development') {
+            if (code.includes('import.meta.env?.DEV')) {
+              return code.replace(/import.meta.env\?.DEV/g, 'true');
+            }
+          } else if (mode === 'production') {
+            if (code.includes('import.meta.env?.DEV')) {
+              return code.replace(/import.meta.env\?.DEV/g, 'false');
+            }
+          }
+          return undefined;
+        },
+      },
       babel({
         babelHelpers: 'bundled',
         extensions: ['.js', '.ts', '.gjs', '.gts'],