[pull] canary from vercel:canary

package.json

@@ -201,7 +201,7 @@
     "eslint-plugin-jsdoc": "48.0.4",
     "eslint-plugin-mdx": "3.1.5",
     "eslint-plugin-react": "7.37.0",
-    "eslint-plugin-react-hooks": "0.0.0-experimental-4842fbea-20260217",
+    "eslint-plugin-react-hooks": "0.0.0-experimental-2ba30655-20260219",
     "event-stream": "4.0.1",
     "execa": "2.0.3",
     "expect": "29.7.0",
@@ -261,16 +261,16 @@
     "pretty-ms": "7.0.0",
     "random-seed": "0.3.0",
     "react": "19.0.0",
-    "react-builtin": "npm:react@19.3.0-canary-4842fbea-20260217",
+    "react-builtin": "npm:react@19.3.0-canary-2ba30655-20260219",
     "react-dom": "19.0.0",
-    "react-dom-builtin": "npm:react-dom@19.3.0-canary-4842fbea-20260217",
-    "react-dom-experimental-builtin": "npm:react-dom@0.0.0-experimental-4842fbea-20260217",
-    "react-experimental-builtin": "npm:react@0.0.0-experimental-4842fbea-20260217",
-    "react-is-builtin": "npm:react-is@19.3.0-canary-4842fbea-20260217",
-    "react-server-dom-turbopack": "19.3.0-canary-4842fbea-20260217",
-    "react-server-dom-turbopack-experimental": "npm:react-server-dom-turbopack@0.0.0-experimental-4842fbea-20260217",
-    "react-server-dom-webpack": "19.3.0-canary-4842fbea-20260217",
-    "react-server-dom-webpack-experimental": "npm:react-server-dom-webpack@0.0.0-experimental-4842fbea-20260217",
+    "react-dom-builtin": "npm:react-dom@19.3.0-canary-2ba30655-20260219",
+    "react-dom-experimental-builtin": "npm:react-dom@0.0.0-experimental-2ba30655-20260219",
+    "react-experimental-builtin": "npm:react@0.0.0-experimental-2ba30655-20260219",
+    "react-is-builtin": "npm:react-is@19.3.0-canary-2ba30655-20260219",
+    "react-server-dom-turbopack": "19.3.0-canary-2ba30655-20260219",
+    "react-server-dom-turbopack-experimental": "npm:react-server-dom-turbopack@0.0.0-experimental-2ba30655-20260219",
+    "react-server-dom-webpack": "19.3.0-canary-2ba30655-20260219",
+    "react-server-dom-webpack-experimental": "npm:react-server-dom-webpack@0.0.0-experimental-2ba30655-20260219",
     "react-ssr-prepass": "1.0.8",
     "react-virtualized": "9.22.3",
     "relay-compiler": "13.0.2",
@@ -280,8 +280,8 @@
     "resolve-from": "5.0.0",
     "sass": "1.54.0",
     "satori": "0.15.2",
-    "scheduler-builtin": "npm:scheduler@0.28.0-canary-4842fbea-20260217",
-    "scheduler-experimental-builtin": "npm:scheduler@0.0.0-experimental-4842fbea-20260217",
+    "scheduler-builtin": "npm:scheduler@0.28.0-canary-2ba30655-20260219",
+    "scheduler-experimental-builtin": "npm:scheduler@0.0.0-experimental-2ba30655-20260219",
     "seedrandom": "3.0.5",
     "semver": "7.3.7",
     "serve-handler": "6.1.6",
@@ -326,10 +326,10 @@
       "@types/react-dom": "19.2.3",
       "@types/retry": "0.12.0",
       "jest-snapshot": "30.0.0-alpha.6",
-      "react": "19.3.0-canary-4842fbea-20260217",
-      "react-dom": "19.3.0-canary-4842fbea-20260217",
-      "react-is": "19.3.0-canary-4842fbea-20260217",
-      "scheduler": "0.28.0-canary-4842fbea-20260217"
+      "react": "19.3.0-canary-2ba30655-20260219",
+      "react-dom": "19.3.0-canary-2ba30655-20260219",
+      "react-is": "19.3.0-canary-2ba30655-20260219",
+      "scheduler": "0.28.0-canary-2ba30655-20260219"
     },
     "packageExtensions": {
       "eslint-plugin-react-hooks@0.0.0-experimental-6de32a5a-20250822": {

packages/next/errors.json

@@ -1064,5 +1064,6 @@
   "1063": "`connection` must not be used within a Client Component. Next.js should be preventing `connection` from being included in Client Components statically, but did not in this case.",
   "1064": "createServerParamsForRoute should not be called in client contexts.",
   "1065": "createServerPathnameForMetadata should not be called in client contexts.",
-  "1066": "createServerSearchParamsForServerPage should not be called in a client validation."
+  "1066": "createServerSearchParamsForServerPage should not be called in a client validation.",
+  "1067": "The Next.js unhandled rejection filter is being installed more than once. This is a bug in Next.js."
 }

packages/next/src/build/templates/app-page.ts

@@ -1470,6 +1470,15 @@ export async function handler(
         body.push(
           new ReadableStream({
             start(controller) {
+              if (isInstantNavigationTest) {
+                // Inject a global so the client can detect that this response
+                // is a partial static shell, independent of document.cookie
+                // (which may be empty on the new page in some browsers).
+                const encoder = new TextEncoder()
+                controller.enqueue(
+                  encoder.encode('<script>self.__next_instant_test=1</script>')
+                )
+              }
               controller.enqueue(ENCODED_TAGS.CLOSED.BODY_AND_HTML)
               controller.close()
             },

packages/next/src/client/app-bootstrap.ts

@@ -76,29 +76,32 @@ export function appBootstrap(hydrate: (assetPrefix: string) => void) {
       }
     }
 
-    // Instant Navigation Testing API: If the page was loaded with the instant
-    // test cookie set (from an MPA navigation while locked), skip hydration
-    // and set up a minimal testing API. Hydration would fail because the
-    // static shell response doesn't include the full Flight data stream.
-    // When unlock() is called, we clear the cookie and reload the page.
+    // Instant Navigation Testing API: If the server returned a partial static
+    // shell (indicated by the __next_instant_test global injected into the
+    // HTML), skip hydration. The response doesn't include the full Flight data
+    // stream. When the test framework deletes the cookie, the CookieStore
+    // change event triggers a page reload.
     if (process.env.__NEXT_EXPOSE_TESTING_API) {
-      const NEXT_INSTANT_TEST_COOKIE = 'next-instant-navigation-testing'
-      if (document.cookie.includes(NEXT_INSTANT_TEST_COOKIE + '=')) {
-        // Set up minimal testing API for the static shell
-        window.__EXPERIMENTAL_NEXT_TESTING__ = {
-          navigation: {
-            lock: () => {
-              console.error(
-                'Navigation lock already acquired. Concurrent locks are not allowed. ' +
-                  'Did you forget to release the previous lock?'
-              )
-            },
-            unlock: () => {
-              // Clear the cookie and reload to get the full page with dynamic data
-              document.cookie = `${NEXT_INSTANT_TEST_COOKIE}=;path=/;max-age=0`
-              window.location.reload()
-            },
-          },
+      if (self.__next_instant_test) {
+        const NEXT_INSTANT_TEST_COOKIE = 'next-instant-navigation-testing'
+        if (
+          typeof cookieStore !== 'undefined' &&
+          document.cookie.includes(NEXT_INSTANT_TEST_COOKIE + '=')
+        ) {
+          // Cookie is still set. Wait for the test framework to delete it,
+          // then reload to get the full response.
+          cookieStore.addEventListener('change', (event: CookieChangeEvent) => {
+            for (const cookie of event.deleted) {
+              if (cookie.name === NEXT_INSTANT_TEST_COOKIE) {
+                window.location.reload()
+                return
+              }
+            }
+          })
+        } else {
+          // Cookie is already gone (or not accessible). Refresh immediately
+          // to get the full response.
+          window.location.reload()
         }
         return
       }

packages/next/src/client/app-globals.ts

@@ -6,16 +6,11 @@ if (process.env.__NEXT_DEV_SERVER) {
   require('../next-devtools/userspace/app/app-dev-overlay-setup') as typeof import('../next-devtools/userspace/app/app-dev-overlay-setup')
 }
 
-// Expose a testing API that allows e2e tests to assert on the prefetched UI
-// state before dynamic data streams in. Browser-only.
+// Start listening for the instant navigation test cookie. The test framework
+// (e.g. Playwright) sets/clears this cookie to control the navigation lock.
+// Browser-only.
 if (process.env.__NEXT_EXPOSE_TESTING_API && typeof window !== 'undefined') {
-  const { acquireNavigationLock, releaseNavigationLock } =
+  const { startListeningForInstantNavigationCookie } =
     require('./components/segment-cache/navigation-testing-lock') as typeof import('./components/segment-cache/navigation-testing-lock')
-
-  window.__EXPERIMENTAL_NEXT_TESTING__ = {
-    navigation: {
-      lock: acquireNavigationLock,
-      unlock: releaseNavigationLock,
-    },
-  }
+  startListeningForInstantNavigationCookie()
 }

packages/next/src/client/app-index.tsx

@@ -65,16 +65,6 @@ declare global {
      */
     __next_r?: string
     __next_f: NextFlight
-    /**
-     * Testing API that allows e2e tests to assert on the prefetched UI state
-     * before dynamic data streams in. Dev-only.
-     */
-    __EXPERIMENTAL_NEXT_TESTING__?: {
-      navigation: {
-        lock: () => void
-        unlock: () => void
-      }
-    }
   }
 }