microsoft · acoates-ms · Apr 6, 2026 · Apr 3, 2026 · Apr 3, 2026 · Apr 3, 2026
@@ -173,7 +173,7 @@ extends:
             displayName: Remove postinstall
             condition: and(succeeded(), eq(variables['detectScenario.isReleaseBuild'], 'False'))
 
-          - script: npx --yes midgard-yarn-strict@1.2.4 @rnw-scripts/beachball-config
+          - script: yarn install --immutable
             displayName: Strict yarn install @rnw-scripts/beachball-config
             condition: and(succeeded(), eq(variables['detectScenario.isReleaseBuild'], 'False'))
 

@@ -60,7 +60,7 @@ jobs:
       - script: if not exist %APPDATA%\npm (mkdir %APPDATA%\npm)
         displayName: Ensure npm directory for npx commands
 
-      - script: npx --yes midgard-yarn@1.23.34 --ignore-scripts --frozen-lockfile
+      - script: yarn install --immutable
         displayName: yarn install
 
       - script: npx lage build --scope @rnw-scripts/prepare-release --scope @rnw-scripts/beachball-config

@@ -18,8 +18,6 @@ steps:
     condition: eq(variables['Agent.OS'], 'Windows_NT')
 
   - template: yarn-install.yml
-    parameters:
-      agentImage: ${{ parameters.agentImage }}
 
   - script: yarn build
     displayName: yarn build
@@ -4,12 +4,12 @@ parameters:
   default: react-native-windows-repo
 
 steps:
-  # midgard-yarn-strict does not respect --ignore-scripts
+  # Remove postinstall to avoid running build during install
   - pwsh: |
       $packageJson = Get-Content ./package.json | ConvertFrom-Json
       $packageJson.scripts = $packageJson.scripts | Select-Object * -ExcludeProperty postinstall
       $packageJson | ConvertTo-Json | Out-File ./package.json
     displayName: Remove postinstall
 
-  - script: npx --yes midgard-yarn-strict@1.2.4 ${{ parameters.workspace }}
+  - script: yarn install --immutable
     displayName: Strict yarn install ${{ parameters.workspace }}
@@ -37,7 +37,6 @@ steps:
 
   - script: | 
       call npm config set registry http://localhost:4873
-      call yarn config set registry http://localhost:4873
       call yarn config set npmRegistryServer http://localhost:4873
       call yarn config set unsafeHttpWhitelist --json "[\"localhost\"]"
     displayName: Modify npm/yarn config to point to local verdaccio server

@@ -14,9 +14,8 @@ steps:
 
   - script: | 
       call npm config delete registry
-      call yarn config delete registry
-      call yarn config delete npmRegistryServer
-      call yarn config delete unsafeHttpWhitelist
+      call yarn config unset npmRegistryServer
+      call yarn config unset unsafeHttpWhitelist
     displayName: Reset npm/yarn config to stop poiting at local verdaccio server
     env:
       YARN_ENABLE_IMMUTABLE_INSTALLS: false
@@ -2,22 +2,7 @@ parameters:
 - name: workingDirectory
   type: string
   default: .
-- name: agentImage
-  type: string
-  default: ManagedImage
-  values:
-      - ManagedImage
-      - HostedImage
 
 steps:
-  # When using our own images, prefer the machine-installed version of
-  # `midgard-yarn`.
-  - ${{ if eq(parameters.agentImage, 'ManagedImage') }}:
-    - script: midgard-yarn --ignore-scripts --frozen-lockfile --cwd ${{ parameters.workingDirectory }}
-      displayName: midgard-yarn (faster yarn install)
-
-  # If using an image we don't control, acquire a fixed version of midgard-yarn
-  # before install
-  - ${{ else }}:
-    - script: npx --yes midgard-yarn@1.23.34 --ignore-scripts --frozen-lockfile --cwd ${{ parameters.workingDirectory }}
-      displayName: midgard-yarn (faster yarn install)
+  - script: yarn --cwd ${{ parameters.workingDirectory }} install --immutable
+    displayName: yarn install (immutable)
@@ -15,7 +15,3 @@ variables:
   # Guardian Config
   GDN_DOTNET_INSTALL: false
   GDN_SUPPRESS_FORKED_BUILD_WARNING: true
-
-  # Yarn Config
-  YARN_CACHE_FOLDER: $(Agent.TempDirectory)/.yarnCache
-  YARN_NETWORK_CONCURRENCY: 40
@@ -40,16 +40,13 @@ jobs:
         with:
           node-version: '20'
 
-      - name: Install Yarn
-        run: npm install -g yarn
-
       - name: Delete yarn.lock and reinstall dependencies (skip scripts)
         working-directory: ./repo
         run: |
           echo "🧹 Removing yarn.lock..."
           rm -f yarn.lock
           echo "📦 Running yarn install without lifecycle scripts..."
-          yarn install --ignore-scripts
+          yarn install --mode=skip-build
 
       - name: Commit and push changes via gh CLI
         working-directory: ./repo

@@ -44,10 +44,9 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: 22
-          cache: yarn
 
       - name: Install dependencies
-        run: yarn install --frozen-lockfile
+        run: yarn install --immutable
 
       - name: Detect preinstalled Windows SDK
         id: winsdk

@@ -27,6 +27,14 @@ build/Release
 # Dependency directory
 node_modules
 
+# Yarn v4
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/sdks
+.pnp.*
+
 # Optional npm cache directory
 .npm
 
@@ -193,8 +201,5 @@ nul
 /packages/jest-environment-winappdriver/*
 /packages/node-rnw-rpc/*
 
-# midgard-yarn-strict
-.store*/*
-
 /npm-pkgs
 /.claude/
@@ -1 +1,5 @@
-enableScripts: false
+enableScripts: false
+
+yarnPath: .yarn/releases/yarn-4.13.0.cjs
+
+nodeLinker: node-modules
@@ -27,10 +27,10 @@
   >
 
     <Message Text="Running yarn install to fetch latest packages." Importance="High" />
-    <Message Text="yarn install --frozen-lockfile --mutex file:.yarn-mutex" Importance="High" />
+    <Message Text="yarn install --immutable" Importance="High" />
     <Exec
       ContinueOnError="True"
-      Command="yarn install --frozen-lockfile --mutex file:.yarn-mutex"
+      Command="yarn install --immutable"
       WorkingDirectory="$(MSBuildThisFileDirectory)"
     >
       <Output TaskParameter="ExitCode" ItemName="_ReactNativeYarnExitCode" />

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Upgrade to yarn v4",
+  "packageName": "@office-iss/react-native-win32",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Upgrade to yarn v4",
+  "packageName": "@react-native-windows/automation-channel",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Move to yarn 4",
+  "packageName": "@react-native-windows/automation-commands",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Move to yarn 4",
+  "packageName": "@react-native-windows/automation",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Upgrade to yarn v4",
+  "packageName": "@react-native-windows/cli",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Move to yarn 4",
+  "packageName": "@react-native-windows/codegen",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Upgrade to yarn v4",
+  "packageName": "@react-native-windows/find-repo-root",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Upgrade to yarn v4",
+  "packageName": "@react-native-windows/fs",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Upgrade to yarn v4",
+  "packageName": "@react-native-windows/package-utils",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Move to yarn 4",
+  "packageName": "@react-native-windows/perf-testing",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Upgrade to yarn v4",
+  "packageName": "@react-native-windows/telemetry",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Move to yarn 4",
+  "packageName": "react-native-platform-override",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "none",
+  "comment": "Move to yarn4",
+  "packageName": "react-native-windows",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "none"
+}
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Move to yarn 4",
+  "packageName": "react-native-windows-init",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}
@@ -41,14 +41,14 @@
     "@rnw-scripts/promote-release": "*",
     "@rnw-scripts/stamp-version": "0.0.0",
     "@rnw-scripts/take-screenshot": "*",
+    "@rnw-scripts/unbroken": "*",
     "beachball": "^2.20.0",
     "fast-glob": "^3.2.11",
     "husky": "^4.2.5",
-    "prettier-plugin-hermes-parser": "0.21.1",
-    "react-native-platform-override": "0.0.0-canary.1017",
-    "@rnw-scripts/unbroken": "*",
     "lage": "^2.7.1",
-    "lodash": "^4.17.15"
+    "lodash": "^4.17.15",
+    "prettier-plugin-hermes-parser": "0.21.1",
+    "react-native-platform-override": "0.0.0-canary.1017"
   },
   "resolutions": {
     "react": "19.2.3",
@@ -59,13 +59,13 @@
     "safe-buffer": "^5.2.1",
     "set-value": "^4.0.1",
     "strip-ansi": "^6.0.1",
-    "**/parse-url/normalize-url": "^4.5.1",
-    "**/@react-native/monorepo/node_modules/jest-junit": "^13.0.0",
-    "**/@react-native/monorepo/node_modules/ws": "^6.2.3",
-    "**/@react-native/tester/ws": "^6.2.3",
-    "**/webdriverio/**/puppeteer-core/ws": "^8.17.1",
-    "**/detox/ws": "^5.2.4",
+    "parse-url/normalize-url": "^4.5.1",
+    "@react-native/monorepo/jest-junit": "^13.0.0",
+    "@react-native/monorepo/ws": "^6.2.3",
+    "@react-native/tester/ws": "^6.2.3",
+    "puppeteer-core/ws": "^8.17.1",
+    "detox/ws": "^5.2.4",
     "xml2js": "^0.5.0"
   },
-  "packageManager": "yarn@1.22.22+sha512.a6b2f7906b721bba3d67d4aff083df04dad64c399707841b7acf00f6b133b7ac24255f2652fa22ae3534329dc6180534e98d17432037ff6fd140556e2bb3137e"
-}
+  "packageManager": "yarn@4.13.0"
+}
@@ -12,8 +12,8 @@
   },
   "dependencies": {
     "@react-native/tester": "0.84.0-nightly-20260107-58bc6c3e3",
-    "@typescript-eslint/eslint-plugin": "^7.1.1",
-    "@typescript-eslint/parser": "^7.1.1",
+    "@typescript-eslint/eslint-plugin": "^8.36.0",
+    "@typescript-eslint/parser": "^8.36.0",
     "flow-enums-runtime": "^0.0.6"
   },
   "peerDependencies": {

@@ -63,8 +63,8 @@ function FocusMoverTestComponent() {
 }
 
 interface IKeyboardableComponentState {
-  lastKeyDown: string;
-  lastKeyUp: string;
+  lastKeyDown: string | null;
+  lastKeyUp: string | null;
 }
 
 const handledNativeKeyboardEvents: IHandledKeyboardEvent[] = [

@@ -265,11 +265,11 @@ const SelectionItemComponent: React.FunctionComponent<ISelectionItemComponentPro
   }
 
   function addToSelection() {
-    props.addHandler(props.value);
+    props.addHandler?.(props.value);
   }
 
   function removeFromSelection() {
-    props.removeHandler(props.value);
+    props.removeHandler?.(props.value);
   }
 };
 
@@ -324,14 +324,14 @@ const renderItem = (item: ListRenderItemInfo<IListProps>) => (
   <ListItem label={item.item.label} level={item.item.level} setSize={item.item.setSize} positionInSet={item.item.positionInSet} />
 );
 
-const getItemLayout = (data: ArrayLike<IListProps>, index: number) => ({ length: 30, offset: 30 * index, index });
+const getItemLayout = (data: ArrayLike<IListProps> | null | undefined, index: number) => ({ length: 30, offset: 30 * index, index });
 
 const keyExtractor = (item: IListProps) => item.label.toString();
 
 interface IFlatListProps {
   renderItem: (item: ListRenderItemInfo<IListProps>) => React.JSX.Element;
   getItemLayout?: (
-    data: ArrayLike<IListProps>,
+    data: ArrayLike<IListProps> | null | undefined,
     index: number
   ) => {
     length: number;