code · pull · May 21, 2026 · May 20, 2026 · May 20, 2026 · May 20, 2026
diff --git a/.github/workflows/build_reusable.yml b/.github/workflows/build_reusable.yml
@@ -128,6 +128,8 @@ env:
   KV_REST_API_URL: ${{ secrets.KV_REST_API_URL }}
   KV_REST_API_TOKEN: ${{ secrets.KV_REST_API_TOKEN }}
   NEXT_TEST_JOB: 1
+  # Per-job memoization of passed test files.
+  NEXT_TEST_PASSED_FILE: .next-test-passed.txt
   VERCEL_TEST_TOKEN: ${{ secrets.VERCEL_TEST_TOKEN }}
   VERCEL_TEST_TEAM: vtest314-next-e2e-tests
   VERCEL_ADAPTER_TEST_TOKEN: ${{ secrets.VERCEL_ADAPTER_TEST_TOKEN }}
@@ -371,6 +373,17 @@ jobs:
         if: ${{ inputs.testTimingsArtifact == '' }}
         run: pnpm dlx turbo@${TURBO_VERSION} run get-test-timings -- --build ${{ github.sha }}
 
+      # Restore the list of tests that already passed in an earlier
+      # attempt of this same workflow run.
+      - name: Restore passed-tests cache
+        if: ${{ inputs.afterBuild && runner.environment == 'github-hosted' }}
+        uses: actions/cache/restore@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+        with:
+          path: ${{ env.NEXT_TEST_PASSED_FILE }}
+          key: next-test-passed-${{ steps.var.outputs.input_step_key }}-${{ github.run_id }}-attempt${{ github.run_attempt }}
+          restore-keys: |
+            next-test-passed-${{ steps.var.outputs.input_step_key }}-${{ github.run_id }}-
+
       - run: ${{ inputs.afterBuild }}
         # defaults.run.shell sets a stronger options (`-leo pipefail`)
         # Set this back to github action's weaker defaults:
@@ -380,6 +393,15 @@ jobs:
         shell: bash -le {0}
         timeout-minutes: ${{ inputs.timeout_minutes }}
 
+      # Save the passed-tests file so the next attempt (if any) can skip
+      # them. `always()` makes this run on success, failure, or cancellation.
+      - name: Save passed-tests cache
+        if: ${{ always() && inputs.afterBuild && runner.environment == 'github-hosted' }}
+        uses: actions/cache/save@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+        with:
+          path: ${{ env.NEXT_TEST_PASSED_FILE }}
+          key: next-test-passed-${{ steps.var.outputs.input_step_key }}-${{ github.run_id }}-attempt${{ github.run_attempt }}
+
       - name: Upload test result artifacts
         if: ${{ inputs.testReportsArtifactPrefix != '' && inputs.afterBuild && always() }}
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1

diff --git a/crates/next-api/src/project.rs b/crates/next-api/src/project.rs
@@ -588,9 +588,10 @@ impl ProjectContainer {
             node_version = options.current_node_js_version.as_str(),
             os = std::env::consts::OS,
             arch = std::env::consts::ARCH,
-            cpu_cores = std::thread::available_parallelism()
-                .map(|n| n.get())
-                .unwrap_or(0),
+            turbo_tasks_available_parallelism =
+                turbo_tasks::parallel::available_parallelism().map(|n| n.get()).unwrap_or(0),
+            std_thread_available_parallelism =
+                std::thread::available_parallelism().map(|n| n.get()).unwrap_or(0),
             dev = options.dev,
             env_diff = Empty
         );

diff --git a/crates/next-napi-bindings/src/lib.rs b/crates/next-napi-bindings/src/lib.rs
@@ -74,7 +74,6 @@ fn init() {
     use std::{
         cell::RefCell,
         panic::{set_hook, take_hook},
-        thread::available_parallelism,
         time::{Duration, Instant},
     };
 
@@ -83,7 +82,7 @@ fn init() {
     }
 
     use tokio::runtime::Builder;
-    use turbo_tasks::panic_hooks::handle_panic;
+    use turbo_tasks::{panic_hooks::handle_panic, parallel::available_parallelism};
     use turbo_tasks_malloc::TurboMalloc;
 
     let prev_hook = take_hook();

diff --git a/lerna.json b/lerna.json
@@ -15,5 +15,5 @@
       "registry": "https://registry.npmjs.org/"
     }
   },
-  "version": "16.3.0-canary.24"
+  "version": "16.3.0-canary.25"
 }
diff --git a/packages/create-next-app/package.json b/packages/create-next-app/package.json
@@ -1,6 +1,6 @@
 {
   "name": "create-next-app",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "keywords": [
     "react",
     "next",

diff --git a/packages/eslint-config-next/package.json b/packages/eslint-config-next/package.json
@@ -1,6 +1,6 @@
 {
   "name": "eslint-config-next",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "description": "ESLint configuration used by Next.js.",
   "license": "MIT",
   "repository": {
@@ -12,7 +12,7 @@
     "dist"
   ],
   "dependencies": {
-    "@next/eslint-plugin-next": "16.3.0-canary.24",
+    "@next/eslint-plugin-next": "16.3.0-canary.25",
     "eslint-import-resolver-node": "^0.3.6",
     "eslint-import-resolver-typescript": "^3.5.2",
     "eslint-plugin-import": "^2.32.0",

diff --git a/packages/eslint-plugin-internal/package.json b/packages/eslint-plugin-internal/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@next/eslint-plugin-internal",
   "private": true,
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "description": "ESLint plugin for working on Next.js.",
   "exports": {
     ".": "./src/eslint-plugin-internal.js"

diff --git a/packages/eslint-plugin-next/package.json b/packages/eslint-plugin-next/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/eslint-plugin-next",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "description": "ESLint plugin for Next.js.",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

diff --git a/packages/font/package.json b/packages/font/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@next/font",
   "private": true,
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "repository": {
     "url": "vercel/next.js",
     "directory": "packages/font"

diff --git a/packages/next-bundle-analyzer/package.json b/packages/next-bundle-analyzer/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/bundle-analyzer",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "main": "index.js",
   "types": "index.d.ts",
   "license": "MIT",

diff --git a/packages/next-codemod/package.json b/packages/next-codemod/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/codemod",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "license": "MIT",
   "repository": {
     "type": "git",

diff --git a/packages/next-env/package.json b/packages/next-env/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/env",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "keywords": [
     "react",
     "next",

diff --git a/packages/next-mdx/package.json b/packages/next-mdx/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/mdx",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "main": "index.js",
   "license": "MIT",
   "repository": {

diff --git a/packages/next-playwright/package.json b/packages/next-playwright/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/playwright",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "repository": {
     "url": "vercel/next.js",
     "directory": "packages/next-playwright"

diff --git a/packages/next-plugin-storybook/package.json b/packages/next-plugin-storybook/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/plugin-storybook",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "repository": {
     "url": "vercel/next.js",
     "directory": "packages/next-plugin-storybook"

diff --git a/packages/next-polyfill-module/package.json b/packages/next-polyfill-module/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/polyfill-module",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "description": "A standard library polyfill for ES Modules supporting browsers (Edge 16+, Firefox 60+, Chrome 61+, Safari 10.1+)",
   "main": "dist/polyfill-module.js",
   "license": "MIT",

diff --git a/packages/next-polyfill-nomodule/package.json b/packages/next-polyfill-nomodule/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/polyfill-nomodule",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "description": "A polyfill for non-dead, nomodule browsers.",
   "main": "dist/polyfill-nomodule.js",
   "license": "MIT",

diff --git a/packages/next-routing/package.json b/packages/next-routing/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/routing",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "keywords": [
     "react",
     "next",

diff --git a/packages/next-rspack/package.json b/packages/next-rspack/package.json
@@ -1,6 +1,6 @@
 {
   "name": "next-rspack",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "repository": {
     "url": "vercel/next.js",
     "directory": "packages/next-rspack"

diff --git a/packages/next-swc/package.json b/packages/next-swc/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@next/swc",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "private": true,
   "files": [
     "native/"

diff --git a/packages/next/errors.json b/packages/next/errors.json
@@ -1276,5 +1276,6 @@
   "1275": "\\`experimental.cssChunking: false\\` is only supported with webpack. Please remove the option or run Next.js with webpack in %s.",
   "1276": "Compilation failed but no issues were recorded",
   "1277": "no route matched for path \"%s\"",
-  "1278": "compileRoute: either routeSpecifier or path is required"
+  "1278": "compileRoute: either routeSpecifier or path is required",
+  "1279": "\\`experimental.appShells\\` requires the following to also be enabled: %s. Please update your %s accordingly."
 }
diff --git a/packages/next/package.json b/packages/next/package.json
@@ -1,6 +1,6 @@
 {
   "name": "next",
-  "version": "16.3.0-canary.24",
+  "version": "16.3.0-canary.25",
   "description": "The React Framework",
   "main": "./dist/server/next.js",
   "license": "MIT",
@@ -101,7 +101,7 @@
     ]
   },
   "dependencies": {
-    "@next/env": "16.3.0-canary.24",
+    "@next/env": "16.3.0-canary.25",
     "@swc/helpers": "0.5.15",
     "baseline-browser-mapping": "^2.9.19",
     "caniuse-lite": "^1.0.30001579",
@@ -165,11 +165,11 @@
     "@modelcontextprotocol/sdk": "1.18.1",
     "@mswjs/interceptors": "0.23.0",
     "@napi-rs/triples": "1.2.0",
-    "@next/font": "16.3.0-canary.24",
-    "@next/polyfill-module": "16.3.0-canary.24",
-    "@next/polyfill-nomodule": "16.3.0-canary.24",
-    "@next/react-refresh-utils": "16.3.0-canary.24",
-    "@next/swc": "16.3.0-canary.24",
+    "@next/font": "16.3.0-canary.25",
+    "@next/polyfill-module": "16.3.0-canary.25",
+    "@next/polyfill-nomodule": "16.3.0-canary.25",
+    "@next/react-refresh-utils": "16.3.0-canary.25",
+    "@next/swc": "16.3.0-canary.25",
     "@opentelemetry/api": "1.6.0",
     "@playwright/test": "1.58.2",
     "@rspack/core": "1.6.7",

diff --git a/packages/next/src/build/define-env.ts b/packages/next/src/build/define-env.ts
@@ -380,6 +380,7 @@ export function getDefineEnv({
       config.experimental.gestureTransition ?? false,
     'process.env.__NEXT_OPTIMISTIC_ROUTING':
       config.experimental.optimisticRouting ?? false,
+    'process.env.__NEXT_APP_SHELLS': config.experimental.appShells ?? false,
     'process.env.__NEXT_VARY_PARAMS': config.experimental.varyParams ?? false,
     'process.env.__NEXT_EXPOSE_TESTING_API':
       dev || config.experimental.exposeTestingApiInProductionBuild === true,