Yarn4

.ado/build-template.yml

@@ -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'))
 

.ado/prepare-release-bot.yml

@@ -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

.ado/templates/prepare-js-env.yml

@@ -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

.ado/templates/strict-yarn-install.yml

@@ -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 }}

.ado/templates/verdaccio-start.yml

@@ -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

.ado/templates/verdaccio-stop.yml

@@ -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

.ado/templates/yarn-install.yml

@@ -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 install --immutable --cwd ${{ parameters.workingDirectory }}
+    displayName: yarn install (immutable)

.ado/variables/shared.yml

@@ -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

.github/workflows/compliance-yarn-lock.yml

@@ -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

.github/workflows/perf-tests.yml

@@ -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

.gitignore

@@ -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/

.yarnrc.yml

@@ -1 +1,5 @@
-enableScripts: false
+enableScripts: false
+
+yarnPath: .yarn/releases/yarn-4.13.0.cjs
+
+nodeLinker: node-modules

change/react-native-windows-f135b933-1b62-426e-9011-e09b9da4418e.json

@@ -0,0 +1,7 @@
+{
+  "type": "none",
+  "comment": "Move to yarn4",
+  "packageName": "react-native-windows",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "none"
+}

package.json

@@ -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"
 }

packages/e2e-test-app-fabric/package.json

@@ -41,10 +41,10 @@
     "@babel/preset-typescript": "^7.8.3",
     "@babel/runtime": "^7.20.0",
     "@react-native-community/cli": "20.0.0",
-    "@react-native-windows/perf-testing": "0.0.0-canary.1037",
-    "@react-native/metro-config": "0.84.0-nightly-20260107-58bc6c3e3",
     "@react-native-windows/automation": "0.0.0-canary.1045",
     "@react-native-windows/automation-commands": "0.0.0-canary.1045",
+    "@react-native-windows/perf-testing": "0.0.0-canary.1037",
+    "@react-native/metro-config": "0.84.0-nightly-20260107-58bc6c3e3",
     "@rnw-scripts/babel-node-config": "2.3.3",
     "@rnw-scripts/babel-react-native-config": "0.0.0",
     "@rnw-scripts/eslint-config": "1.2.38",

packages/sample-custom-component/package.json

@@ -21,8 +21,8 @@
   },
   "dependencies": {
     "@types/react": "^19.2.3",
-    "react": "^19.2.3",
     "minimatch": "^10.0.3",
+    "react": "^19.2.3",
     "react-native": "0.84.0-nightly-20260107-58bc6c3e3",
     "react-native-windows": "^0.0.0-canary.1045"
   },

vnext/Scripts/creaternwapp.cmd

@@ -148,7 +148,6 @@ call git commit -m "npx --yes @react-native-community/cli@%RNCLI_VERSION% init %
 
 if %USE_VERDACCIO% equ 1 (
   @echo creaternwapp.cmd: Setting yarn to use verdaccio at 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\"]"
 )

vnext/Scripts/creaternwlib.cmd

@@ -143,7 +143,6 @@ call yarn install
 
 if %USE_VERDACCIO% equ 1 (
   @echo creaternwlib.cmd: Setting yarn to use verdaccio at 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\"]"
 )