From 3cca311a10a67e1b9b2d7302b38f78a0812af1f8 Mon Sep 17 00:00:00 2001
From: berce <75228263+bercedev@users.noreply.github.com>
Date: Tue, 20 Oct 2026 20:35:07 +0300
Subject: [PATCH 1/2] test: normalize compressed IPv6 addresses in dev server
 output

The IPv6 pattern only matched the full eight-group form, so a unique local address such as [fdb2:2c26:f4e4::1] reached the serve snapshots unchanged, and a full address would have kept its brackets twice. Match the bracketed host in any form, except the [::1] loopback, and replace it with its brackets.
---
 test/utils/test-utils.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/test/utils/test-utils.js b/test/utils/test-utils.js
index dd7d23e72f5..257bb94166c 100644
--- a/test/utils/test-utils.js
+++ b/test/utils/test-utils.js
@@ -268,7 +268,9 @@ const normalizeStdout = (stdout) => {
 };
 
 const IPV4 = /(25[0-5]|2[0-4][0-9]|1?[0-9][0-9]{1,2})(\.(25[0-5]|2[0-4][0-9]|1?[0-9]{1,2})){3}/g;
-const IPV6 = /([0-9a-f]){1,4}(:([0-9a-f]){1,4}){7}/gi;
+// A bracketed IPv6 host in a URL, in full or compressed ("::") form, e.g. a unique local
+// address such as `[fdb2:2c26:f4e4::1]`. The loopback `[::1]` stays as it is.
+const IPV6 = /\[(?!::1\])[0-9a-f]*:[0-9a-f:.]*(%[^\]]+)?\]/gi;
 
 const normalizeStderr = (stderr) => {
   if (typeof stderr !== "string") {

From a82d38b648607621b70d6fb65708d7fe3a8b77e3 Mon Sep 17 00:00:00 2001
From: berce <75228263+bercedev@users.noreply.github.com>
Date: Tue, 20 Oct 2026 21:16:20 +0300
Subject: [PATCH 2/2] test: only replace bracketed text that is an IPv6 address

The pattern also matched tokens such as [1:2] or [dead:beef]. Check the bracket contents with net.isIPv6 before replacing them, and cover normalizeStderr's IPv6 handling with unit tests.
---
 test/api/normalize-stderr.test.js | 33 +++++++++++++++++++++++++++++++
 test/utils/test-utils.js          | 10 +++++++---
 2 files changed, 40 insertions(+), 3 deletions(-)
 create mode 100644 test/api/normalize-stderr.test.js

diff --git a/test/api/normalize-stderr.test.js b/test/api/normalize-stderr.test.js
new file mode 100644
index 00000000000..ed0e32d147a
--- /dev/null
+++ b/test/api/normalize-stderr.test.js
@@ -0,0 +1,33 @@
+"use strict";
+
+const { normalizeStderr } = require("../utils/test-utils");
+
+const NETWORK_IPV6 = "<i> [webpack-dev-server] On Your Network (IPv6): ";
+
+describe("normalizeStderr", () => {
+  it("should replace a compressed IPv6 address, such as a unique local address", () => {
+    expect(normalizeStderr(`${NETWORK_IPV6}http://[fdb2:2c26:f4e4::1]:8080/`)).toBe(
+      `${NETWORK_IPV6}http://[x:x:x:x:x:x:x:x]:<port>/`,
+    );
+  });
+
+  it("should replace a full IPv6 address with its brackets", () => {
+    expect(normalizeStderr(`${NETWORK_IPV6}http://[2001:db8:0:0:0:0:0:1]:8080/`)).toBe(
+      `${NETWORK_IPV6}http://[x:x:x:x:x:x:x:x]:<port>/`,
+    );
+  });
+
+  it("should keep the IPv6 loopback", () => {
+    expect(
+      normalizeStderr(
+        "<i> [webpack-dev-server] Loopback: http://localhost:8080/, http://[::1]:8080/",
+      ),
+    ).toBe("<i> [webpack-dev-server] Loopback: http://localhost:<port>/, http://[::1]:<port>/");
+  });
+
+  it("should leave bracketed text that is not an IPv6 address", () => {
+    expect(normalizeStderr("[1:2] [dead:beef] [webpack-dev-server]")).toBe(
+      "[1:2] [dead:beef] [webpack-dev-server]",
+    );
+  });
+});
diff --git a/test/utils/test-utils.js b/test/utils/test-utils.js
index 257bb94166c..addd613a11b 100644
--- a/test/utils/test-utils.js
+++ b/test/utils/test-utils.js
@@ -2,6 +2,7 @@
 
 const { exec } = require("node:child_process");
 const fs = require("node:fs");
+const { isIPv6 } = require("node:net");
 const path = require("node:path");
 const { stripVTControlCharacters } = require("node:util");
 const concat = require("concat-stream");
@@ -269,8 +270,11 @@ const normalizeStdout = (stdout) => {
 
 const IPV4 = /(25[0-5]|2[0-4][0-9]|1?[0-9][0-9]{1,2})(\.(25[0-5]|2[0-4][0-9]|1?[0-9]{1,2})){3}/g;
 // A bracketed IPv6 host in a URL, in full or compressed ("::") form, e.g. a unique local
-// address such as `[fdb2:2c26:f4e4::1]`. The loopback `[::1]` stays as it is.
-const IPV6 = /\[(?!::1\])[0-9a-f]*:[0-9a-f:.]*(%[^\]]+)?\]/gi;
+// address such as `[fdb2:2c26:f4e4::1]`. The loopback `[::1]` and bracketed text that is not
+// an IPv6 address stay as they are.
+const IPV6 = /\[([0-9a-f:.]+)(%[^\]]+)?\]/gi;
+const replaceIPv6 = (match, address) =>
+  address !== "::1" && isIPv6(address) ? "[x:x:x:x:x:x:x:x]" : match;
 
 const normalizeStderr = (stderr) => {
   if (typeof stderr !== "string") {
@@ -285,7 +289,7 @@ const normalizeStderr = (stderr) => {
   normalizedStderr = normalizeCwd(normalizedStderr);
 
   normalizedStderr = normalizedStderr.replaceAll(IPV4, "x.x.x.x");
-  normalizedStderr = normalizedStderr.replaceAll(IPV6, "[x:x:x:x:x:x:x:x]");
+  normalizedStderr = normalizedStderr.replaceAll(IPV6, replaceIPv6);
   normalizedStderr = normalizedStderr.replaceAll(/:[0-9]+\//g, ":<port>/");
 
   if (!/On Your Network \(IPv6\)/.test(stderr)) {