diff --git a/.github/setup-node/action.yml b/.github/setup-node/action.yml
index 374b0c49d58437..c4f22d77ace0b7 100644
--- a/.github/setup-node/action.yml
+++ b/.github/setup-node/action.yml
@@ -32,11 +32,14 @@ runs:
               echo "NPM_VERSION=$(npm -v)" >> "$GITHUB_OUTPUT"
           shell: bash
 
+        # Windows tar cannot restore the isolated layout's links, so always install there.
         - name: Cache node_modules
           id: cache-node_modules
-          if: ${{ inputs.cache == 'true' }}
+          if: ${{ inputs.cache == 'true' && runner.os != 'Windows' }}
           uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
           with:
+              # The key covers .npmrc because install-strategy decides the layout:
+              # a hoisted tree restored into an isolated checkout resolves nothing.
               # List workspace node_modules explicitly to support all kinds of layouts - hoisted and isolated.
               # A '**/node_modules' glob follows the isolated layout's symlinks and stalls the cache step.
               # The eval package is not a workspace: it installs its own large tree from its own lockfile.
@@ -49,7 +52,7 @@ runs:
                   !test/ai-development/node_modules
                   tools/*/node_modules
                   widgets/*/node_modules
-              key: node_modules-${{ runner.os }}-${{ runner.arch }}-${{ steps.node-version.outputs.NODE_VERSION }}-npm-${{ steps.node-version.outputs.NPM_VERSION }}-${{ hashFiles('package-lock.json', 'patches/**') }}
+              key: node_modules-${{ runner.os }}-${{ runner.arch }}-${{ steps.node-version.outputs.NODE_VERSION }}-npm-${{ steps.node-version.outputs.NPM_VERSION }}-${{ hashFiles('package-lock.json', '.npmrc') }}
 
         - name: Install npm dependencies
           if: ${{ steps.cache-node_modules.outputs.cache-hit != 'true' }}
diff --git a/.npmrc b/.npmrc
index e631ca1ea82fe5..b1b1add06b7cc5 100644
--- a/.npmrc
+++ b/.npmrc
@@ -1,3 +1,4 @@
+install-strategy = "linked"
 engine-strict = true
 strict-peer-deps = true
 prefer-dedupe = true
diff --git a/docs/contributors/code/getting-started-with-code-contribution.md b/docs/contributors/code/getting-started-with-code-contribution.md
index 1c62985bb34592..e870fd5498ef72 100644
--- a/docs/contributors/code/getting-started-with-code-contribution.md
+++ b/docs/contributors/code/getting-started-with-code-contribution.md
@@ -241,6 +241,12 @@ You can start with this workspace settings file:
 		"**/node_modules/**": true,
 		"**/vendor/**": true
 	},
+	// Use TypeScript from the workspace instead of VS Code's built-in TypeScript version.
+	"js/ts.tsdk.path": "tools/build-scripts/node_modules/@typescript/native/lib",
+	// Use ESLint, Prettier and Stylelint from the respective paths.
+	"eslint.nodePath": "tools/eslint/node_modules",
+	"prettier.prettierPath": "packages/prettier-config/node_modules/prettier",
+	"stylelint.stylelintPath": "tools/stylelint/node_modules/stylelint",
 	"[php]": {
 		"editor.formatOnSave": true,
 		"editor.defaultFormatter": "obliviousharmony.vscode-php-codesniffer"
diff --git a/package-lock.json b/package-lock.json
index b8938e2466ba2c..c5d0988866b394 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -40,7 +40,7 @@
 			},
 			"engines": {
 				"node": ">=24.18.0",
-				"npm": ">=11.16.0"
+				"npm": ">=11.18.0"
 			}
 		},
 		"node_modules/@actions/core": {
diff --git a/package.json b/package.json
index f137f24732cd61..3fdd783a6dc6d4 100644
--- a/package.json
+++ b/package.json
@@ -16,7 +16,7 @@
 	},
 	"engines": {
 		"node": ">=24.18.0",
-		"npm": ">=11.16.0"
+		"npm": ">=11.18.0"
 	},
 	"devEngines": {
 		"runtime": {
@@ -25,7 +25,7 @@
 		},
 		"packageManager": {
 			"name": "npm",
-			"version": ">=11.16.0",
+			"version": ">=11.18.0",
 			"onFail": "error"
 		}
 	},
diff --git a/packages/dependency-extraction-webpack-plugin/test/__snapshots__/build.js.snap b/packages/dependency-extraction-webpack-plugin/test/__snapshots__/build.js.snap
index 36e937d83b9373..0eb447bb20d81c 100644
--- a/packages/dependency-extraction-webpack-plugin/test/__snapshots__/build.js.snap
+++ b/packages/dependency-extraction-webpack-plugin/test/__snapshots__/build.js.snap
@@ -253,7 +253,7 @@ exports[`DependencyExtractionWebpackPlugin modules > Webpack \`no-default\` > sh
 	'dependencies' => array(
 		
 	),
-	'version' => 'ef50aa650dbfb7d400af',
+	'version' => 'e92a9548b4a6bd2acd81',
 	'type' => 'module'
 );
 "
@@ -418,7 +418,7 @@ exports[`DependencyExtractionWebpackPlugin modules > Webpack \`runtime-chunk-sin
 	'dependencies' => array(
 		'@wordpress/blob'
 	),
-	'version' => '5822b2168d9a9ad0ab52',
+	'version' => '0b4be29a9a428b9e8608',
 	'type' => 'module',
 	'handle' => 'runtime-chunk-single-modules-a'
 );
@@ -858,7 +858,7 @@ exports[`DependencyExtractionWebpackPlugin scripts > Webpack \`no-default\` > sh
 	'dependencies' => array(
 		
 	),
-	'version' => '93d83bee525cbfa3ca27'
+	'version' => '9c20c9bd8e5f5841767b'
 );
 "
 `;
@@ -1029,7 +1029,7 @@ exports[`DependencyExtractionWebpackPlugin scripts > Webpack \`runtime-chunk-sin
 	'dependencies' => array(
 		'wp-blob'
 	),
-	'version' => '10219f2e878437d6563a',
+	'version' => 'c4233136b50b85f54397',
 	'handle' => 'runtime-chunk-single-scripts-a'
 );
 "
diff --git a/storybook/main.ts b/storybook/main.ts
index 2a815147340b58..722e556e842657 100644
--- a/storybook/main.ts
+++ b/storybook/main.ts
@@ -94,6 +94,12 @@ const config: StorybookConfig = {
 		// Should match defaults in Storybook except for the propFilter.
 		// https://github.com/storybookjs/storybook/blob/3e34a288c8fabc7d5b5cc43b28ae9d674c48e3ea/code/core/src/core-server/presets/common-preset.ts#L162-L168
 		reactDocgenTypescriptOptions: {
+			/*
+			 * Vite's root is this workspace, so the plugin's default glob stops
+			 * at its edge and the documented sources need naming explicitly.
+			 */
+			include: [ '**/*.tsx', '../packages/*/src/**/*.tsx' ],
+			exclude: [ '**/test/**', '**/node_modules/**' ],
 			// Use a docgen-specific TypeScript configuration that disables
 			// project references. Without this, docgen follows referenced
 			// projects' built `.d.ts` declarations and emits a duplicate
@@ -130,8 +136,14 @@ const config: StorybookConfig = {
 			savePropValueAsString: true,
 		},
 	},
-	viteFinal: async ( viteConfig ) => {
+	viteFinal: async ( viteConfig, options ) => {
 		return mergeConfig( viteConfig, {
+			/*
+			 * Storybook roots Vite at the repository root, which owns none of
+			 * the dependencies. Each config roots itself, so the one that
+			 * spreads this gets its own workspace rather than this one.
+			 */
+			root: options.configDir,
 			resolve: {
 				alias: [
 					{
diff --git a/test/storybook-playwright/storybook/main.ts b/test/storybook-playwright/storybook/main.ts
index 4e4099db21769e..fec94ee5744a6b 100644
--- a/test/storybook-playwright/storybook/main.ts
+++ b/test/storybook-playwright/storybook/main.ts
@@ -9,13 +9,13 @@ export default {
 		...baseConfig.typescript,
 		reactDocgenTypescriptOptions: {
 			...baseConfig.typescript?.reactDocgenTypescriptOptions,
-			// Vite's root is this workspace, so include the source files used
-			// by these stories outside that root in the docgen project.
+			// Vite's root is this config's directory, so include the sources
+			// these stories document from outside it in the docgen project.
 			include: [
 				'**/*.tsx',
-				'../../packages/components/src/**/*.tsx',
-				'../../packages/ui/src/**/*.tsx',
-				'../../storybook/**/*.tsx',
+				'../../../packages/components/src/**/*.tsx',
+				'../../../packages/ui/src/**/*.tsx',
+				'../../../storybook/**/*.tsx',
 			],
 		},
 	},
diff --git a/tools/monorepo/tsconfig/tsconfig.base.json b/tools/monorepo/tsconfig/tsconfig.base.json
index 928ca12d1d035b..e13c851b898476 100644
--- a/tools/monorepo/tsconfig/tsconfig.base.json
+++ b/tools/monorepo/tsconfig/tsconfig.base.json
@@ -43,17 +43,11 @@
 		"resolveJsonModule": true,
 
 		/*
-		 * `../typings` is this workspace's own. `@types` packages are not:
-		 * a hoisted install puts them at the repo root, a linked one puts
-		 * them in the workspace that declared them. Both are listed because
-		 * TypeScript skips a type root that does not exist, so the preset
-		 * serves either layout.
+		 * `../typings` is this workspace's own. `@types` packages resolve from
+		 * the project that declared them, so a package using types it never
+		 * declared fails here instead of borrowing them from the root.
 		 */
-		"typeRoots": [
-			"../typings",
-			"${configDir}/node_modules/@types",
-			"../../../node_modules/@types"
-		],
+		"typeRoots": [ "../typings", "${configDir}/node_modules/@types" ],
 		"types": [],
 
 		"rootDir": "${configDir}/src",
diff --git a/tools/validation/check-installed-deps.mjs b/tools/validation/check-installed-deps.mjs
index ca5baa470059e2..95d6f02139c5e7 100644
--- a/tools/validation/check-installed-deps.mjs
+++ b/tools/validation/check-installed-deps.mjs
@@ -10,6 +10,7 @@
  * Exits non-zero with a hint to run `npm install` if the trees diverge.
  */
 
+import { execFileSync } from 'node:child_process';
 import fs from 'node:fs';
 import path from 'node:path';
 import os from 'node:os';
@@ -24,6 +25,7 @@ const CACHE_FILE = path.join(
 	'node_modules',
 	'.check-installed-deps.cache.json'
 );
+const STORE = path.join( ROOT, 'node_modules', '.store' );
 
 const verbose = process.argv.includes( '--verbose' );
 
@@ -36,6 +38,51 @@ function fail( summary, details = '' ) {
 	process.exit( 1 );
 }
 
+/**
+ * Read the configured install strategy. npm resolves it across every .npmrc,
+ * the environment and the command line, so ask npm rather than parse a file.
+ *
+ * @return {string} The configured strategy.
+ */
+function configuredStrategy() {
+	// Set for anything npm runs, which is how this check is invoked.
+	if ( process.env.npm_config_install_strategy ) {
+		return process.env.npm_config_install_strategy;
+	}
+
+	try {
+		return execFileSync( 'npm', [ 'config', 'get', 'install-strategy' ], {
+			cwd: ROOT,
+			encoding: 'utf8',
+		} ).trim();
+	} catch {
+		return 'hoisted';
+	}
+}
+
+/*
+ * The lockfile is the same under either layout, and the comparison below
+ * reduces paths to name@version, so a tree installed with the other strategy
+ * passes everything. Compare the configured strategy against the real tree
+ * first, and before the mtime fast path, which such a tree would satisfy.
+ */
+const strategy = configuredStrategy();
+const installedIsolated = fs.existsSync( STORE );
+
+if ( strategy === 'linked' && ! installedIsolated ) {
+	fail(
+		'npm is configured for the isolated layout but node_modules is hoisted.',
+		`\tno ${ path.relative( ROOT, STORE ) }; run \`npm install\` to reinstall.`
+	);
+}
+
+if ( strategy !== 'linked' && installedIsolated ) {
+	fail(
+		`npm is configured for the ${ strategy } layout but node_modules is isolated.`,
+		`\t${ path.relative( ROOT, STORE ) } exists; run \`npm install\` to reinstall.`
+	);
+}
+
 /*
  * Fast path: skip the full check if neither lockfile has changed since the
  * last successful run. Both files' mtimes are written into a cache file