[pull] canary from vercel:canary

lerna.json

@@ -16,5 +16,5 @@
       "registry": "https://registry.npmjs.org/"
     }
   },
-  "version": "15.4.2-canary.24"
+  "version": "15.4.2-canary.25"
 }

package.json

@@ -233,16 +233,16 @@
     "pretty-ms": "7.0.0",
     "random-seed": "0.3.0",
     "react": "19.0.0",
-    "react-builtin": "npm:[email protected]9784cb37-20250730",
+    "react-builtin": "npm:[email protected]c260b38d-20250731",
     "react-dom": "19.0.0",
-    "react-dom-builtin": "npm:[email protected]9784cb37-20250730",
-    "react-dom-experimental-builtin": "npm:[email protected]9784cb37-20250730",
-    "react-experimental-builtin": "npm:[email protected]9784cb37-20250730",
-    "react-is-builtin": "npm:[email protected]9784cb37-20250730",
-    "react-server-dom-turbopack": "19.2.0-canary-9784cb37-20250730",
-    "react-server-dom-turbopack-experimental": "npm:[email protected]9784cb37-20250730",
-    "react-server-dom-webpack": "19.2.0-canary-9784cb37-20250730",
-    "react-server-dom-webpack-experimental": "npm:[email protected]9784cb37-20250730",
+    "react-dom-builtin": "npm:[email protected]c260b38d-20250731",
+    "react-dom-experimental-builtin": "npm:[email protected]c260b38d-20250731",
+    "react-experimental-builtin": "npm:[email protected]c260b38d-20250731",
+    "react-is-builtin": "npm:[email protected]c260b38d-20250731",
+    "react-server-dom-turbopack": "19.2.0-canary-c260b38d-20250731",
+    "react-server-dom-turbopack-experimental": "npm:[email protected]c260b38d-20250731",
+    "react-server-dom-webpack": "19.2.0-canary-c260b38d-20250731",
+    "react-server-dom-webpack-experimental": "npm:[email protected]c260b38d-20250731",
     "react-ssr-prepass": "1.0.8",
     "react-virtualized": "9.22.3",
     "relay-compiler": "13.0.2",
@@ -252,8 +252,8 @@
     "resolve-from": "5.0.0",
     "sass": "1.54.0",
     "satori": "0.15.2",
-    "scheduler-builtin": "npm:[email protected]9784cb37-20250730",
-    "scheduler-experimental-builtin": "npm:[email protected]9784cb37-20250730",
+    "scheduler-builtin": "npm:[email protected]c260b38d-20250731",
+    "scheduler-experimental-builtin": "npm:[email protected]c260b38d-20250731",
     "seedrandom": "3.0.5",
     "semver": "7.3.7",
     "serve-handler": "6.1.6",
@@ -297,10 +297,10 @@
       "@types/react-dom": "19.1.6",
       "@types/retry": "0.12.0",
       "jest-snapshot": "30.0.0-alpha.6",
-      "react": "19.2.0-canary-9784cb37-20250730",
-      "react-dom": "19.2.0-canary-9784cb37-20250730",
-      "react-is": "19.2.0-canary-9784cb37-20250730",
-      "scheduler": "0.27.0-canary-9784cb37-20250730"
+      "react": "19.2.0-canary-c260b38d-20250731",
+      "react-dom": "19.2.0-canary-c260b38d-20250731",
+      "react-is": "19.2.0-canary-c260b38d-20250731",
+      "scheduler": "0.27.0-canary-c260b38d-20250731"
     },
     "patchedDependencies": {
       "[email protected]": "patches/[email protected]",

packages/create-next-app/package.json

@@ -1,6 +1,6 @@
 {
   "name": "create-next-app",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "keywords": [
     "react",
     "next",

packages/eslint-config-next/package.json

@@ -1,6 +1,6 @@
 {
   "name": "eslint-config-next",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "description": "ESLint configuration used by Next.js.",
   "main": "index.js",
   "license": "MIT",
@@ -10,7 +10,7 @@
   },
   "homepage": "https://nextjs.org/docs/app/api-reference/config/eslint",
   "dependencies": {
-    "@next/eslint-plugin-next": "15.4.2-canary.24",
+    "@next/eslint-plugin-next": "15.4.2-canary.25",
     "@rushstack/eslint-patch": "^1.10.3",
     "@typescript-eslint/eslint-plugin": "^5.4.2 || ^6.0.0 || ^7.0.0 || ^8.0.0",
     "@typescript-eslint/parser": "^5.4.2 || ^6.0.0 || ^7.0.0 || ^8.0.0",

packages/eslint-plugin-internal/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@next/eslint-plugin-internal",
   "private": true,
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "description": "ESLint plugin for working on Next.js.",
   "exports": {
     ".": "./src/eslint-plugin-internal.js"

packages/eslint-plugin-next/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@next/eslint-plugin-next",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "description": "ESLint plugin for Next.js.",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

packages/font/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@next/font",
   "private": true,
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "repository": {
     "url": "vercel/next.js",
     "directory": "packages/font"

packages/next-bundle-analyzer/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@next/bundle-analyzer",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "main": "index.js",
   "types": "index.d.ts",
   "license": "MIT",

packages/next-codemod/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@next/codemod",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "license": "MIT",
   "repository": {
     "type": "git",

packages/next-env/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@next/env",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "keywords": [
     "react",
     "next",

packages/next-mdx/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@next/mdx",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "main": "index.js",
   "license": "MIT",
   "repository": {

packages/next-plugin-storybook/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@next/plugin-storybook",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "repository": {
     "url": "vercel/next.js",
     "directory": "packages/next-plugin-storybook"

packages/next-polyfill-module/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@next/polyfill-module",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-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",

packages/next-polyfill-nomodule/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@next/polyfill-nomodule",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "description": "A polyfill for non-dead, nomodule browsers.",
   "main": "dist/polyfill-nomodule.js",
   "license": "MIT",

packages/next-rspack/package.json

@@ -1,6 +1,6 @@
 {
   "name": "next-rspack",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "repository": {
     "url": "vercel/next.js",
     "directory": "packages/next-rspack"

packages/next-swc/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@next/swc",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "private": true,
   "files": [
     "native/"

packages/next/errors.json

@@ -764,5 +764,11 @@
   "763": "\\`unstable_rootParams\\` must not be used within a client component. Next.js should be preventing it from being included in client components statically, but did not in this case.",
   "764": "Missing workStore in %s",
   "765": "Route %s used %s inside a Route Handler. Support for this API in Route Handlers is planned for a future version of Next.js.",
-  "766": "%s was used inside a Server Action. This is not supported. Functions from 'next/root-params' can only be called in the context of a route."
+  "766": "%s was used inside a Server Action. This is not supported. Functions from 'next/root-params' can only be called in the context of a route.",
+  "767": "A runtime prerender store should not be used for a route handler.",
+  "768": "createPrerenderSearchParamsForClientPage should not be called in a runtime prerender.",
+  "769": "createSearchParamsFromClient should not be called in a runtime prerender.",
+  "770": "createParamsFromClient should not be called in a runtime prerender.",
+  "771": "\\`%s\\` was called during a runtime prerender. Next.js should be preventing %s from being included in server components statically, but did not in this case.",
+  "772": "FetchStrategy.PPRRuntime should never be used when `experimental.clientSegmentCache` is disabled"
 }

packages/next/package.json

@@ -1,6 +1,6 @@
 {
   "name": "next",
-  "version": "15.4.2-canary.24",
+  "version": "15.4.2-canary.25",
   "description": "The React Framework",
   "main": "./dist/server/next.js",
   "license": "MIT",
@@ -102,7 +102,7 @@
     ]
   },
   "dependencies": {
-    "@next/env": "15.4.2-canary.24",
+    "@next/env": "15.4.2-canary.25",
     "@swc/helpers": "0.5.15",
     "caniuse-lite": "^1.0.30001579",
     "postcss": "8.4.31",
@@ -166,11 +166,11 @@
     "@jest/types": "29.5.0",
     "@mswjs/interceptors": "0.23.0",
     "@napi-rs/triples": "1.2.0",
-    "@next/font": "15.4.2-canary.24",
-    "@next/polyfill-module": "15.4.2-canary.24",
-    "@next/polyfill-nomodule": "15.4.2-canary.24",
-    "@next/react-refresh-utils": "15.4.2-canary.24",
-    "@next/swc": "15.4.2-canary.24",
+    "@next/font": "15.4.2-canary.25",
+    "@next/polyfill-module": "15.4.2-canary.25",
+    "@next/polyfill-nomodule": "15.4.2-canary.25",
+    "@next/react-refresh-utils": "15.4.2-canary.25",
+    "@next/swc": "15.4.2-canary.25",
     "@opentelemetry/api": "1.6.0",
     "@playwright/test": "1.51.1",
     "@rspack/core": "1.4.5",

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

@@ -192,7 +192,7 @@ export async function handler(
    */
   const isPrefetchRSCRequest =
     getRequestMeta(req, 'isPrefetchRSCRequest') ??
-    Boolean(req.headers[NEXT_ROUTER_PREFETCH_HEADER])
+    req.headers[NEXT_ROUTER_PREFETCH_HEADER] === '1' // exclude runtime prefetches, which use '2'
 
   // NOTE: Don't delete headers[RSC] yet, it still needs to be used in renderToHTML later
 

packages/next/src/client/app-dir/form.tsx

@@ -61,6 +61,7 @@ export default function Form({
     }
   }
 
+  // TODO(runtime-ppr): allow runtime prefetches in Form
   const prefetch =
     prefetchProp === false || prefetchProp === null ? prefetchProp : null
 

packages/next/src/client/app-dir/link.tsx

@@ -20,7 +20,10 @@ import {
 import { isLocalURL } from '../../shared/lib/router/utils/is-local-url'
 import { dispatchNavigateAction } from '../components/app-router-instance'
 import { errorOnce } from '../../shared/lib/utils/error-once'
-import { FetchStrategy } from '../components/segment-cache'
+import {
+  FetchStrategy,
+  type PrefetchTaskFetchStrategy,
+} from '../components/segment-cache'
 
 type Url = string | UrlObject
 type RequiredKeys<T> = {
@@ -151,10 +154,10 @@ type InternalLinkProps = {
    * </Link>
    * ```
    */
-  prefetch?: boolean | 'auto' | null
+  prefetch?: boolean | 'auto' | null | 'unstable_forceStale'
 
   /**
-   * (unstable) Switch to a dynamic prefetch on hover. Effectively the same as
+   * (unstable) Switch to a full prefetch on hover. Effectively the same as
    * updating the prefetch prop to `true` in a mouse event.
    */
   unstable_dynamicOnHover?: boolean
@@ -356,18 +359,12 @@ export default function LinkComponent(
   const router = React.useContext(AppRouterContext)
 
   const prefetchEnabled = prefetchProp !== false
-  /**
-   * The possible states for prefetch are:
-   * - null: this is the default "auto" mode, where we will prefetch partially if the link is in the viewport
-   * - true: we will prefetch if the link is visible and prefetch the full page, not just partially
-   * - false: we will not prefetch if in the viewport at all
-   * - 'unstable_dynamicOnHover': this starts in "auto" mode, but switches to "full" when the link is hovered
-   */
+
   const fetchStrategy =
-    prefetchProp === null || prefetchProp === 'auto'
-      ? // We default to PPR. We'll discover whether or not the route supports it with the initial prefetch.
+    prefetchProp !== false
+      ? getFetchStrategyFromPrefetchProp(prefetchProp)
+      : // TODO: it makes no sense to assign a fetchStrategy when prefetching is disabled.
         FetchStrategy.PPR
-      : FetchStrategy.Full
 
   if (process.env.NODE_ENV !== 'production') {
     function createPropError(args: {
@@ -470,11 +467,12 @@ export default function LinkComponent(
         if (
           props[key] != null &&
           valType !== 'boolean' &&
-          props[key] !== 'auto'
+          props[key] !== 'auto' &&
+          props[key] !== 'unstable_forceStale'
         ) {
           throw createPropError({
             key,
-            expected: '`boolean | "auto"`',
+            expected: '`boolean | "auto" | "unstable_forceStale"`',
             actual: valType,
           })
         }
@@ -745,3 +743,41 @@ const LinkStatusContext = createContext<
 export const useLinkStatus = () => {
   return useContext(LinkStatusContext)
 }
+
+function getFetchStrategyFromPrefetchProp(
+  prefetchProp: Exclude<LinkProps['prefetch'], undefined | false>
+): PrefetchTaskFetchStrategy {
+  if (
+    process.env.__NEXT_CACHE_COMPONENTS &&
+    process.env.__NEXT_CLIENT_SEGMENT_CACHE
+  ) {
+    // In the new implementation:
+    // - `prefetch={true}` is a runtime prefetch
+    //   (includes cached IO + params + cookies, with dynamic holes for uncached IO).
+    // - `unstable_forceStale` is a "full" prefetch
+    //   (forces inclusion of all dynamic data, i.e. the old behavior of `prefetch={true}`)
+    if (prefetchProp === true) {
+      return FetchStrategy.PPRRuntime
+    }
+    if (prefetchProp === 'unstable_forceStale') {
+      return FetchStrategy.Full
+    }
+
+    // `null` or `"auto"`: this is the default "auto" mode, where we will prefetch partially if the link is in the viewport.
+    // This will also include invalid prop values that don't match the types specified here.
+    // (although those should've been filtered out by prop validation in dev)
+    prefetchProp satisfies null | 'auto'
+    // In `clientSegmentCache`, we default to PPR, and we'll discover whether or not the route supports it with the initial prefetch.
+    // If we're not using `clientSegmentCache`, this will be converted into a `PrefetchKind.AUTO`.
+    return FetchStrategy.PPR
+  } else {
+    return prefetchProp === null || prefetchProp === 'auto'
+      ? // In `clientSegmentCache`, we default to PPR, and we'll discover whether or not the route supports it with the initial prefetch.
+        // If we're not using `clientSegmentCache`, this will be converted into a `PrefetchKind.AUTO`.
+        FetchStrategy.PPR
+      : // In the old implementation without runtime prefetches, `prefetch={true}` forces all dynamic data to be prefetched.
+        // To preserve backwards-compatibility, anything other than `false`, `null`, or `"auto"` results in a full prefetch.
+        // (although invalid values should've been filtered out by prop validation in dev)
+        FetchStrategy.Full
+  }
+}

packages/next/src/client/components/app-router-instance.ts

@@ -329,6 +329,8 @@ export const publicAppRouterInstance: AppRouterInstance = {
         const actionQueue = getAppRouterActionQueue()
         const prefetchKind = options?.kind ?? PrefetchKind.AUTO
 
+        // We don't currently offer a way to issue a runtime prefetch via `router.prefetch()`.
+        // This will be possible when we update its API to not take a PrefetchKind.
         let fetchStrategy: PrefetchTaskFetchStrategy
         switch (prefetchKind) {
           case PrefetchKind.AUTO: {

packages/next/src/client/components/bailout-to-client-rendering.ts

@@ -12,6 +12,7 @@ export function bailoutToClientRendering(reason: string): void | never {
   if (workUnitStore) {
     switch (workUnitStore.type) {
       case 'prerender':
+      case 'prerender-runtime':
       case 'prerender-client':
       case 'prerender-ppr':
       case 'prerender-legacy':

packages/next/src/client/components/links.ts

@@ -17,6 +17,7 @@ import {
 } from './segment-cache'
 import { startTransition } from 'react'
 import { PrefetchKind } from './router-reducer/router-reducer-types'
+import { InvariantError } from '../../shared/lib/invariant-error'
 
 type LinkElement = HTMLAnchorElement | SVGAElement
 
@@ -264,7 +265,7 @@ export function onNavigationIntent(
       process.env.__NEXT_DYNAMIC_ON_HOVER &&
       unstable_upgradeToDynamicPrefetch
     ) {
-      // Switch to a full, dynamic prefetch
+      // Switch to a full prefetch
       instance.fetchStrategy = FetchStrategy.Full
     }
     rescheduleLinkPrefetch(instance, PrefetchPriority.Intent)
@@ -378,6 +379,13 @@ function prefetchWithOldCacheImplementation(instance: PrefetchableInstance) {
         prefetchKind = PrefetchKind.FULL
         break
       }
+      case FetchStrategy.PPRRuntime: {
+        // We can only get here if Client Segment Cache is off, and in that case
+        // it shouldn't be possible for a link to request a runtime prefetch.
+        throw new InvariantError(
+          'FetchStrategy.PPRRuntime should never be used when `experimental.clientSegmentCache` is disabled'
+        )
+      }
       default: {
         instance.fetchStrategy satisfies never
         // Unreachable, but otherwise typescript will consider the variable unassigned