fix(dns-cache): prevent local family cache collisions

.circleci/workflows.yml

@@ -147,6 +147,12 @@ executors:
       PLATFORM: linux
       # TODO: Disabling snapshots for now on Linux Arm 64 architectures. Will revisit with https://github.com/cypress-io/cypress/issues/23557
       DISABLE_SNAPSHOT_REQUIRE: 1
+  linux-x64: &linux-x64-executor
+    machine:
+      image: ubuntu-2004:2024.11.1
+    resource_class: medium
+    environment:
+      PLATFORM: linux
 
 commands:
   # This command inserts SHOULD_PERSIST_ARTIFACTS into BASH_ENV. This way, we can define the variable in one place and use it in multiple steps.
@@ -1791,11 +1797,36 @@ jobs:
           condition:
             equal: [ *windows-executor, << parameters.executor >> ]
           steps:
-            - run: yarn test-scripts
-            # run unit tests from each individual package
-            - run: yarn test
-            # run type checking for each individual package
-            - run: yarn lerna run types
+            - run:
+                name: Enable IPv6 in Docker
+                command: |
+                  cat \<<'EOF' | sudo tee /etc/docker/daemon.json
+                  {
+                    "ipv6": true,
+                    "fixed-cidr-v6": "2001:db8:1::/64"
+                  }
+                  EOF
+                  cat \<<'EOF' | sudo tee /etc/hosts
+                  127.0.0.1 localhost
+                  ::1 localhost
+                  EOF
+                  sudo service docker restart
+            - run:
+                name: Test scripts
+                command: |
+                  source ./scripts/ensure-node.sh
+                  yarn test-scripts
+            - run:
+                name: Test each individual package
+                command: |
+                  source ./scripts/ensure-node.sh
+                  # this is needed since we are have to be running as root to test some packages
+                  sudo -E env "PATH=$PATH" yarn test
+            - run:
+                name: Test types
+                command: |
+                  source ./scripts/ensure-node.sh
+                  yarn lerna run types
             - sanitize-verify-and-store-mocha-results:
                 expectedResultCount: 20
 
@@ -2908,6 +2939,7 @@ linux-x64-workflow: &linux-x64-workflow
         requires:
           - build
     - unit-tests:
+        executor: linux-x64
         requires:
           - build
     - verify-release-readiness:

.vscode/terminals.json

@@ -89,6 +89,13 @@
       "onlySingle": true,
       "cwd": "[cwd]/packages/driver",
       "command": "yarn cypress:open"
+    },
+    {
+      "name": "packages/network test",
+      "focus": true,
+      "onlySingle": true,
+      "cwd": "[cwd]/packages/network",
+      "command": "yarn test-watch [file]"
     }
   ]
 }

cli/CHANGELOG.md

@@ -1,7 +1,11 @@
 <!-- See the ../guides/writing-the-cypress-changelog.md for details on writing the changelog. -->
 ## 15.1.1
 
-_Released 09/16/2025 (PENDING)_
+_Released 9/9/2025 (PENDING)_
+
+**Bugfixes:**
+
+- We now properly partition the `host` with `port` when caching family DNS lookups. This resolves issues where some `localhost` URLs were not resolving in `cy.visit()` in Cypress when they should have. Fixes [#25397](https://github.com/cypress-io/cypress/issues/25397). Addressed in [#32403](https://github.com/cypress-io/cypress/pull/32403).
 
 **Dependency Updates:**
 

package.json

@@ -113,7 +113,7 @@
     "@types/lodash": "^4.14.168",
     "@types/markdown-it": "12.2.3",
     "@types/mocha": "8.0.3",
-    "@types/node": "20.16.0",
+    "@types/node": "22.15.1",
     "@types/prismjs": "1.16.0",
     "@types/react": "18.3.12",
     "@types/react-dom": "18.3.1",

packages/network/.mocharc.js

@@ -3,7 +3,7 @@ module.exports = {
     'test/unit/**/*.ts',
     'test/integration/**/*.ts'
   ],
-  require: '../web-config/node-register',
+  require: '@packages/ts/register',
   timeout: 10000,
   recursive: true
-} 
+}

packages/network/lib/agent.ts

@@ -148,17 +148,17 @@ export const regenerateRequestHead = (req: http.ClientRequest) => {
   }
 }
 
-const getFirstWorkingFamily = (
-  { port, host }: http.RequestOptions,
+export const getFirstWorkingFamily = (
+  { port, host }: Pick<http.RequestOptions, 'port' | 'host'>,
   familyCache: FamilyCache,
-  cb: Function,
+  cb: (family?: net.family) => void,
 ) => {
   // this is a workaround for localhost (and potentially others) having invalid
   // A records but valid AAAA records. here, we just cache the family of the first
   // returned A/AAAA record for a host that we can establish a connection to.
   // https://github.com/cypress-io/cypress/issues/112
 
-  const isIP = net.isIP(host)
+  const isIP = net.isIP(host) as net.family | 0
 
   if (isIP) {
     // isIP conveniently returns the family of the address
@@ -170,13 +170,15 @@ const getFirstWorkingFamily = (
     return cb()
   }
 
-  if (familyCache[host]) {
-    return cb(familyCache[host])
+  const cacheKey = `${host}:${port}`
+
+  if (familyCache[cacheKey]) {
+    return cb(familyCache[cacheKey])
   }
 
   return getAddress(port, host)
   .then((firstWorkingAddress: net.Address) => {
-    familyCache[host] = firstWorkingAddress.family
+    familyCache[cacheKey] = firstWorkingAddress.family
 
     return cb(firstWorkingAddress.family)
   })
@@ -246,7 +248,7 @@ export class CombinedAgent {
 
     debug('addRequest called %o', { isHttps, ..._.pick(options, 'href') })
 
-    return getFirstWorkingFamily(options, this.familyCache, (family: net.family) => {
+    return getFirstWorkingFamily(options, this.familyCache, (family?: net.family) => {
       options.family = family
 
       debug('got family %o', _.pick(options, 'family', 'href'))

packages/network/test/integration/connect_spec.ts

@@ -19,7 +19,10 @@ describe('lib/connect', function () {
       const server = net.createServer(_.partialRight(_.invoke, 'close'))
 
       return Bluebird.fromCallback((cb) => {
-        server.listen(0, '127.0.0.1', cb)
+        server.listen({
+          port: 0,
+          host: '127.0.0.1',
+        }, cb.bind(server))
       })
       .then(() => {
         return connect.getAddress(server.address().port, 'localhost')
@@ -31,19 +34,24 @@ describe('lib/connect', function () {
         })
       })
       .then(() => {
-        server.close()
+        return Bluebird.fromCallback((cb) => {
+          server.close(cb)
+        })
       })
     })
 
     // Error: listen EADDRNOTAVAIL ::1
     // NOTE: add an ipv6 lo if to the docker container
-    it.skip('resolves localhost on ::1 immediately', function () {
+    it('resolves localhost on ::1 immediately', function () {
       this.timeout(50)
 
       const server = net.createServer(_.partialRight(_.invoke, 'close'))
 
       return Bluebird.fromCallback((cb) => {
-        server.listen(0, '::1', cb)
+        server.listen({
+          port: 0,
+          host: '::1',
+        }, cb.bind(server))
       })
       .then(() => {
         return connect.getAddress(server.address().port, 'localhost')
@@ -55,7 +63,9 @@ describe('lib/connect', function () {
         })
       })
       .then(() => {
-        server.close()
+        return Bluebird.fromCallback((cb) => {
+          server.close(cb)
+        })
       })
     })
   })