From 86c6e0ce162d5fdbc76eef058f0aa018dd428da3 Mon Sep 17 00:00:00 2001
From: Jerel Miller <jerelmiller@gmail.com>
Date: Thu, 23 Jul 2026 10:10:42 -0600
Subject: [PATCH 1/3] Prevent setTimeout from firing if we can't match devtools
 user agent

---
 src/core/ApolloClient.ts | 43 ++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 21 deletions(-)

diff --git a/src/core/ApolloClient.ts b/src/core/ApolloClient.ts
index cbde11446b2..b6eaeedf22d 100644
--- a/src/core/ApolloClient.ts
+++ b/src/core/ApolloClient.ts
@@ -1169,33 +1169,34 @@ export class ApolloClient {
      */
     if (!hasSuggestedDevtools && __DEV__) {
       hasSuggestedDevtools = true;
+
+      const ua = window.navigator.userAgent;
+      let url: string | undefined;
+
+      if (typeof ua === "string") {
+        if (ua.indexOf("Chrome/") > -1) {
+          url =
+            "https://chrome.google.com/webstore/detail/" +
+            "apollo-client-developer-t/jdkknkkbebbapilgoeccciglkfbmbnfm";
+        } else if (ua.indexOf("Firefox/") > -1) {
+          url =
+            "https://addons.mozilla.org/en-US/firefox/addon/apollo-developer-tools/";
+        }
+      }
+
       if (
         window.document &&
         window.top === window.self &&
-        /^(https?|file):$/.test(window.location.protocol)
+        /^(https?|file):$/.test(window.location.protocol) &&
+        url
       ) {
         setTimeout(() => {
           if (!(window as any).__APOLLO_DEVTOOLS_GLOBAL_HOOK__) {
-            const nav = window.navigator;
-            const ua = nav && nav.userAgent;
-            let url: string | undefined;
-            if (typeof ua === "string") {
-              if (ua.indexOf("Chrome/") > -1) {
-                url =
-                  "https://chrome.google.com/webstore/detail/" +
-                  "apollo-client-developer-t/jdkknkkbebbapilgoeccciglkfbmbnfm";
-              } else if (ua.indexOf("Firefox/") > -1) {
-                url =
-                  "https://addons.mozilla.org/en-US/firefox/addon/apollo-developer-tools/";
-              }
-            }
-            if (url) {
-              invariant.log(
-                "Download the Apollo DevTools for a better development " +
-                  "experience: %s",
-                url
-              );
-            }
+            invariant.log(
+              "Download the Apollo DevTools for a better development " +
+                "experience: %s",
+              url
+            );
           }
         }, 10000);
       }

From 78bed77f158f19944ad4e6f1dcc93f2e38c9db03 Mon Sep 17 00:00:00 2001
From: Jerel Miller <jerelmiller@gmail.com>
Date: Thu, 23 Jul 2026 10:20:17 -0600
Subject: [PATCH 2/3] Add changeset

---
 .changeset/lemon-fireants-build.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/lemon-fireants-build.md

diff --git a/.changeset/lemon-fireants-build.md b/.changeset/lemon-fireants-build.md
new file mode 100644
index 00000000000..5c78fd215ca
--- /dev/null
+++ b/.changeset/lemon-fireants-build.md
@@ -0,0 +1,5 @@
+---
+"@apollo/client": patch
+---
+
+Prevent the `setTimeout` in `connectToDevtools` that shows the devtools suggestion from firing when the user agent does not match Chrome or Firefox. This check was previously done inside the `setTimeout` which meant the timer was scheduled for environments where we'd never show the message anyways. For test environments, this could cause flaky tests when that `setTimeout` outlived the tests and ran after any virtual DOM was torn down and removed.

From 588ab4b02ee9fb35f50cdbbd07dc8045f7f149bb Mon Sep 17 00:00:00 2001
From: Jerel Miller <jerelmiller@gmail.com>
Date: Thu, 23 Jul 2026 10:42:53 -0600
Subject: [PATCH 3/3] Capture window in a variable

---
 src/core/ApolloClient.ts | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/core/ApolloClient.ts b/src/core/ApolloClient.ts
index b6eaeedf22d..45289b17a39 100644
--- a/src/core/ApolloClient.ts
+++ b/src/core/ApolloClient.ts
@@ -1169,8 +1169,9 @@ export class ApolloClient {
      */
     if (!hasSuggestedDevtools && __DEV__) {
       hasSuggestedDevtools = true;
+      const win = window;
 
-      const ua = window.navigator.userAgent;
+      const ua = win.navigator.userAgent;
       let url: string | undefined;
 
       if (typeof ua === "string") {
@@ -1185,13 +1186,13 @@ export class ApolloClient {
       }
 
       if (
-        window.document &&
-        window.top === window.self &&
-        /^(https?|file):$/.test(window.location.protocol) &&
+        win.document &&
+        win.top === win.self &&
+        /^(https?|file):$/.test(win.location.protocol) &&
         url
       ) {
         setTimeout(() => {
-          if (!(window as any).__APOLLO_DEVTOOLS_GLOBAL_HOOK__) {
+          if (!(win as any).__APOLLO_DEVTOOLS_GLOBAL_HOOK__) {
             invariant.log(
               "Download the Apollo DevTools for a better development " +
                 "experience: %s",