diff --git a/packages/vinext/src/entries/app-rsc-entry.ts b/packages/vinext/src/entries/app-rsc-entry.ts
index 847f17076..246d4f0eb 100644
--- a/packages/vinext/src/entries/app-rsc-entry.ts
+++ b/packages/vinext/src/entries/app-rsc-entry.ts
@@ -59,6 +59,7 @@ const appRouteHandlerCachePath = resolveEntryPath(
 );
 const appPageCachePath = resolveEntryPath("../server/app-page-cache.js", import.meta.url);
 const appPageExecutionPath = resolveEntryPath("../server/app-page-execution.js", import.meta.url);
+const appPageBoundaryPath = resolveEntryPath("../server/app-page-boundary.js", import.meta.url);
 const appPageBoundaryRenderPath = resolveEntryPath(
   "../server/app-page-boundary-render.js",
   import.meta.url,
@@ -68,6 +69,8 @@ const appPageRouteWiringPath = resolveEntryPath(
   "../server/app-page-route-wiring.js",
   import.meta.url,
 );
+const appPageHeadPath = resolveEntryPath("../server/app-page-head.js", import.meta.url);
+const appPageParamsPath = resolveEntryPath("../server/app-page-params.js", import.meta.url);
 const appPageRenderPath = resolveEntryPath("../server/app-page-render.js", import.meta.url);
 const appPageResponsePath = resolveEntryPath("../server/app-page-response.js", import.meta.url);
 const cspPath = resolveEntryPath("../server/csp.js", import.meta.url);
@@ -163,16 +166,23 @@ export function generateRscEntry(
     for (const tmpl of route.templates) getImportVar(tmpl);
     if (route.loadingPath) getImportVar(route.loadingPath);
     if (route.errorPath) getImportVar(route.errorPath);
-    if (route.layoutErrorPaths)
+    if (route.layoutErrorPaths) {
       for (const ep of route.layoutErrorPaths) {
         if (ep) getImportVar(ep);
       }
+    }
     if (route.notFoundPath) getImportVar(route.notFoundPath);
     for (const nfp of route.notFoundPaths || []) {
       if (nfp) getImportVar(nfp);
     }
     if (route.forbiddenPath) getImportVar(route.forbiddenPath);
+    for (const fp of route.forbiddenPaths || []) {
+      if (fp) getImportVar(fp);
+    }
     if (route.unauthorizedPath) getImportVar(route.unauthorizedPath);
+    for (const up of route.unauthorizedPaths || []) {
+      if (up) getImportVar(up);
+    }
     // Register parallel slot modules
     for (const slot of route.parallelSlots) {
       if (slot.pagePath) getImportVar(slot.pagePath);
@@ -195,6 +205,12 @@ export function generateRscEntry(
     const layoutVars = route.layouts.map((l) => getImportVar(l));
     const templateVars = route.templates.map((t) => getImportVar(t));
     const notFoundVars = (route.notFoundPaths || []).map((nf) => (nf ? getImportVar(nf) : "null"));
+    const forbiddenVars = (route.forbiddenPaths || []).map((fp) =>
+      fp ? getImportVar(fp) : "null",
+    );
+    const unauthorizedVars = (route.unauthorizedPaths || []).map((up) =>
+      up ? getImportVar(up) : "null",
+    );
     const slotEntries = route.parallelSlots.map((slot) => {
       const interceptEntries = slot.interceptingRoutes.map(
         (ir) => `        {
@@ -245,7 +261,9 @@ ${slotEntries.join(",\n")}
     notFound: ${route.notFoundPath ? getImportVar(route.notFoundPath) : "null"},
     notFounds: [${notFoundVars.join(", ")}],
     forbidden: ${route.forbiddenPath ? getImportVar(route.forbiddenPath) : "null"},
+    forbiddens: [${forbiddenVars.join(", ")}],
     unauthorized: ${route.unauthorizedPath ? getImportVar(route.unauthorizedPath) : "null"},
+    unauthorizeds: [${unauthorizedVars.join(", ")}],
   }`;
   });
 
@@ -370,7 +388,6 @@ import { createElement } from "react";
 import { setNavigationContext as _setNavigationContextOrig, getNavigationContext as _getNavigationContext } from "next/navigation";
 import { setHeadersContext, headersContextFromRequest, getDraftModeCookieHeader, getAndClearPendingCookies, consumeDynamicUsage, markDynamicUsage, applyMiddlewareRequestHeaders, getHeadersContext, setHeadersAccessPhase } from "next/headers";
 import { NextRequest, NextFetchEvent } from "next/server";
-import { mergeMetadata, resolveModuleMetadata, mergeViewport, resolveModuleViewport } from "vinext/metadata";
 ${middlewarePath ? `import * as middlewareModule from ${JSON.stringify(middlewarePath.replace(/\\/g, "/"))};` : ""}
 ${instrumentationPath ? `import * as _instrumentation from ${JSON.stringify(instrumentationPath.replace(/\\/g, "/"))};` : ""}
 ${effectiveMetaRoutes.length > 0 ? `import { sitemapToXml, robotsToText, manifestToJson } from ${JSON.stringify(metadataRoutesPath)};` : ""}
@@ -402,6 +419,9 @@ import {
   resolveAppPageSpecialError as __resolveAppPageSpecialError,
   teeAppPageRscStreamForCapture as __teeAppPageRscStreamForCapture,
 } from ${JSON.stringify(appPageExecutionPath)};
+import {
+  resolveAppPageParentHttpAccessBoundaryModule as __resolveAppPageParentHttpAccessBoundaryModule,
+} from ${JSON.stringify(appPageBoundaryPath)};
 import {
   renderAppPageErrorBoundary as __renderAppPageErrorBoundary,
   renderAppPageHttpAccessFallback as __renderAppPageHttpAccessFallback,
@@ -415,6 +435,13 @@ import {
   createAppPageTreePath as __createAppPageTreePath,
   resolveAppPageChildSegments as __resolveAppPageChildSegments,
 } from ${JSON.stringify(appPageRouteWiringPath)};
+import {
+  resolveAppPageSegmentParams as __resolveAppPageSegmentParams,
+} from ${JSON.stringify(appPageParamsPath)};
+import {
+  collectAppPageSearchParams as __collectAppPageSearchParams,
+  resolveAppPageHead as __resolveAppPageHead,
+} from ${JSON.stringify(appPageHeadPath)};
 import {
   renderAppPageLifecycle as __renderAppPageLifecycle,
 } from ${JSON.stringify(appPageRenderPath)};
@@ -1027,83 +1054,18 @@ async function buildPageElements(route, params, routePath, pageRequest) {
     };
   }
 
-  // Resolve metadata and viewport from layouts and page.
-  //
-  // generateMetadata() accepts a "parent" (Promise of ResolvedMetadata) as its
-  // second argument (Next.js 13+). The parent resolves to the accumulated
-  // merged metadata of all ancestor segments, enabling patterns like:
-  //
-  //   const previousImages = (await parent).openGraph?.images ?? []
-  //   return { openGraph: { images: ['/new-image.jpg', ...previousImages] } }
-  //
-  // Next.js uses an eager-execution-with-serial-resolution approach:
-  // all generateMetadata() calls are kicked off concurrently, but each
-  // segment's "parent" promise resolves only after the preceding segment's
-  // metadata is resolved and merged. This preserves concurrency for I/O-bound
-  // work while guaranteeing that parent data is available when needed.
-  //
-  // We build a chain: layoutParentPromises[0] = Promise.resolve({}) (no parent
-  // for root layout), layoutParentPromises[i+1] resolves to merge(layouts[0..i]),
-  // and pageParentPromise resolves to merge(all layouts).
-  //
-  // IMPORTANT: Layout metadata errors are swallowed (.catch(() => null)) because
-  // a layout's generateMetadata() failing should not crash the page.
-  // Page metadata errors are NOT swallowed — if the page's generateMetadata()
-  // throws, the error propagates out of buildPageElement() so the caller can
-  // route it to the nearest error.tsx boundary (or global-error.tsx).
-  const layoutMods = route.layouts.filter(Boolean);
-
-  // Convert URLSearchParams → plain object for page generateMetadata() and
-  // pageProps.searchParams. Built before the layout loop so the page metadata
-  // call (below) and pageProps can reference the same object.
-  // NOTE: Layouts do NOT receive searchParams in generateMetadata() — only
-  // pages do. This matches Next.js behavior (resolve-metadata.ts:777).
-  const spObj = Object.create(null);
-  let hasSearchParams = false;
-  if (searchParams && searchParams.forEach) {
-    searchParams.forEach(function(v, k) {
-      hasSearchParams = true;
-      if (k in spObj) {
-        spObj[k] = Array.isArray(spObj[k]) ? spObj[k].concat(v) : [spObj[k], v];
-      } else {
-        spObj[k] = v;
-      }
-    });
-  }
-
-  // Build the parent promise chain and kick off metadata resolution in one pass.
-  // Each layout module is called exactly once. layoutMetaPromises[i] is the
-  // promise for layout[i]'s own metadata result.
-  //
-  // All calls are kicked off immediately (concurrent I/O), but each layout's
-  // "parent" promise only resolves after the preceding layout's metadata is done.
-  const layoutMetaPromises = [];
-  let accumulatedMetaPromise = Promise.resolve({});
-  for (let i = 0; i < layoutMods.length; i++) {
-    const parentForThisLayout = accumulatedMetaPromise;
-    // Kick off this layout's metadata resolution now (concurrent with others).
-    const metaPromise = resolveModuleMetadata(layoutMods[i], params, undefined, parentForThisLayout)
-      .catch((err) => { console.error("[vinext] Layout generateMetadata() failed:", err); return null; });
-    layoutMetaPromises.push(metaPromise);
-    // Advance accumulator: resolves to merged(layouts[0..i]) once layout[i] is done.
-    accumulatedMetaPromise = metaPromise.then(async (result) =>
-      result ? mergeMetadata([await parentForThisLayout, result]) : await parentForThisLayout
-    );
-  }
-  // Page's parent is the fully-accumulated layout metadata.
-  const pageParentPromise = accumulatedMetaPromise;
-
-  const [layoutMetaResults, layoutVpResults, pageMeta, pageVp] = await Promise.all([
-    Promise.all(layoutMetaPromises),
-    Promise.all(layoutMods.map((mod) => resolveModuleViewport(mod, params).catch((err) => { console.error("[vinext] Layout generateViewport() failed:", err); return null; }))),
-    route.page ? resolveModuleMetadata(route.page, params, spObj, pageParentPromise) : Promise.resolve(null),
-    route.page ? resolveModuleViewport(route.page, params) : Promise.resolve(null),
-  ]);
-
-  const metadataList = [...layoutMetaResults.filter(Boolean), ...(pageMeta ? [pageMeta] : [])];
-  const viewportList = [...layoutVpResults.filter(Boolean), ...(pageVp ? [pageVp] : [])];
-  const resolvedMetadata = metadataList.length > 0 ? mergeMetadata(metadataList) : null;
-  const resolvedViewport = mergeViewport(viewportList);
+  const __headResult = await __resolveAppPageHead({
+    layoutModules: route.layouts,
+    layoutTreePositions: route.layoutTreePositions,
+    pageModule: route.page,
+    params,
+    routeSegments: route.routeSegments,
+    searchParams,
+  });
+  const spObj = __headResult.searchParamsObject;
+  const hasSearchParams = __headResult.hasSearchParams;
+  const resolvedMetadata = __headResult.metadata;
+  const resolvedViewport = __headResult.viewport;
 
   // Build the route tree from the leaf page, then delegate the boundary/layout/
   // template/segment wiring to a typed runtime helper so the generated entry
@@ -2540,7 +2502,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
   // Note: CSS is automatically injected by @vitejs/plugin-rsc's
   // rscCssTransform — no manual loadCss() call needed.
   const _hasLoadingBoundary = !!(route.loading && route.loading.default);
-  const _asyncLayoutParams = makeThenableParams(params);
+  const _asyncRouteParams = makeThenableParams(params);
   return __renderAppPageLifecycle({
     cleanPathname,
     clearRequestContext() {
@@ -2583,22 +2545,21 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
     probeLayoutAt(li) {
       const LayoutComp = route.layouts[li]?.default;
       if (!LayoutComp) return null;
-      return LayoutComp({ params: _asyncLayoutParams, children: null });
+      return LayoutComp({
+        params: makeThenableParams(__resolveAppPageSegmentParams(
+          route.routeSegments,
+          route.layoutTreePositions?.[li] ?? 0,
+          params,
+        )),
+        children: null,
+      });
     },
     probePage() {
       if (!PageComponent) return null;
-      const _probeSearchObj = {};
-      url.searchParams.forEach(function(v, k) {
-        if (k in _probeSearchObj) {
-          _probeSearchObj[k] = Array.isArray(_probeSearchObj[k])
-            ? _probeSearchObj[k].concat(v)
-            : [_probeSearchObj[k], v];
-        } else {
-          _probeSearchObj[k] = v;
-        }
-      });
-      const _asyncSearchParams = makeThenableParams(_probeSearchObj);
-      return PageComponent({ params: _asyncLayoutParams, searchParams: _asyncSearchParams });
+      const _asyncSearchParams = makeThenableParams(
+        __collectAppPageSearchParams(url.searchParams).searchParamsObject,
+      );
+      return PageComponent({ params: _asyncRouteParams, searchParams: _asyncSearchParams });
     },
     classification: {
       getLayoutId(index) {
@@ -2633,19 +2594,16 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
         },
         middlewareContext: _mwCtx,
         renderFallbackPage(statusCode) {
-          // Find the not-found component from the parent level (the boundary that
-          // would catch this in Next.js). Walk up from the throwing layout to find
-          // the nearest not-found at a parent layout's directory.
-          let parentNotFound = null;
-          if (route.notFounds) {
-            for (let pi = li - 1; pi >= 0; pi--) {
-              if (route.notFounds[pi]?.default) {
-                parentNotFound = route.notFounds[pi].default;
-                break;
-              }
-            }
-          }
-          if (!parentNotFound) parentNotFound = ${rootNotFoundVar ? `${rootNotFoundVar}?.default` : "null"};
+          const parentBoundary = __resolveAppPageParentHttpAccessBoundaryModule({
+            layoutIndex: li,
+            rootForbiddenModule: ${rootForbiddenVar ?? "null"},
+            rootNotFoundModule: ${rootNotFoundVar ?? "null"},
+            rootUnauthorizedModule: ${rootUnauthorizedVar ?? "null"},
+            routeForbiddenModules: route.forbiddens,
+            routeNotFoundModules: route.notFounds,
+            routeUnauthorizedModules: route.unauthorizeds,
+            statusCode,
+          })?.default ?? null;
           const parentLayouts = route.layouts.slice(0, li);
           return renderHTTPAccessFallbackPage(
             route,
@@ -2653,7 +2611,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
             isRscRequest,
             request,
             {
-              boundaryComponent: parentNotFound,
+              boundaryComponent: parentBoundary,
               layouts: parentLayouts,
               matchedParams: params,
             },
diff --git a/packages/vinext/src/routing/app-router.ts b/packages/vinext/src/routing/app-router.ts
index 143ae1d81..c5662d7bd 100644
--- a/packages/vinext/src/routing/app-router.ts
+++ b/packages/vinext/src/routing/app-router.ts
@@ -108,8 +108,12 @@ export type AppRoute = {
   notFoundPaths: (string | null)[];
   /** Forbidden component path (403) */
   forbiddenPath: string | null;
+  /** Forbidden component paths per layout level (aligned with layouts array). */
+  forbiddenPaths?: (string | null)[];
   /** Unauthorized component path (401) */
   unauthorizedPath: string | null;
+  /** Unauthorized component paths per layout level (aligned with layouts array). */
+  unauthorizedPaths?: (string | null)[];
   /**
    * Filesystem segments from app/ root to the route's directory.
    * Includes route groups and dynamic segments (as template strings like "[id]").
@@ -387,7 +391,9 @@ function discoverSlotSubRoutes(
         notFoundPath: parentRoute.notFoundPath,
         notFoundPaths: parentRoute.notFoundPaths,
         forbiddenPath: parentRoute.forbiddenPath,
+        forbiddenPaths: parentRoute.forbiddenPaths,
         unauthorizedPath: parentRoute.unauthorizedPath,
+        unauthorizedPaths: parentRoute.unauthorizedPaths,
         routeSegments: [...parentRoute.routeSegments, ...rawSegments],
         templateTreePositions: parentRoute.templateTreePositions,
         layoutTreePositions: parentRoute.layoutTreePositions,
@@ -508,6 +514,8 @@ function directoryToAppRoute(
   // These are used for per-layout NotFoundBoundary to match Next.js behavior where
   // notFound() thrown from a layout is caught by the parent layout's boundary.
   const notFoundPaths = discoverBoundaryFilePerLayout(layouts, "not-found", matcher);
+  const forbiddenPaths = discoverBoundaryFilePerLayout(layouts, "forbidden", matcher);
+  const unauthorizedPaths = discoverBoundaryFilePerLayout(layouts, "unauthorized", matcher);
 
   // Discover parallel slots (@team, @analytics, etc.).
   // Slots at the route's own directory use page.tsx; slots at ancestor directories
@@ -527,7 +535,9 @@ function directoryToAppRoute(
     notFoundPath,
     notFoundPaths,
     forbiddenPath,
+    forbiddenPaths,
     unauthorizedPath,
+    unauthorizedPaths,
     routeSegments: segments,
     templateTreePositions,
     layoutTreePositions,
diff --git a/packages/vinext/src/server/app-page-boundary-render.ts b/packages/vinext/src/server/app-page-boundary-render.ts
index 7234665ba..736c82823 100644
--- a/packages/vinext/src/server/app-page-boundary-render.ts
+++ b/packages/vinext/src/server/app-page-boundary-render.ts
@@ -2,16 +2,7 @@ import { Fragment, createElement, type ComponentType, type ReactNode } from "rea
 import { buildClientHookErrorMessage } from "../shims/client-hook-error.js";
 import { ErrorBoundary } from "../shims/error-boundary.js";
 import { LayoutSegmentProvider } from "../shims/layout-segment-context.js";
-import {
-  MetadataHead,
-  ViewportHead,
-  mergeMetadata,
-  mergeViewport,
-  resolveModuleMetadata,
-  resolveModuleViewport,
-  type Metadata,
-  type Viewport,
-} from "../shims/metadata.js";
+import { MetadataHead, ViewportHead } from "../shims/metadata.js";
 import type { AppPageFontPreload } from "./app-page-execution.js";
 import type { AppPageMiddlewareContext } from "./app-page-response.js";
 import {
@@ -33,6 +24,7 @@ import {
   createAppPayloadRouteId,
   type AppElements,
 } from "./app-elements.js";
+import { resolveAppPageHead } from "./app-page-head.js";
 import { createAppPageLayoutEntries } from "./app-page-route-wiring.js";
 
 // oxlint-disable-next-line @typescript-eslint/no-explicit-any
@@ -116,55 +108,6 @@ function getDefaultExport<TModule extends AppPageModule>(
   return module?.default ?? null;
 }
 
-async function resolveAppPageLayoutHead<TModule extends AppPageModule>(
-  layoutModules: readonly (TModule | null | undefined)[],
-  params: AppPageParams,
-): Promise<{ metadata: Metadata | null; viewport: Viewport }> {
-  const filteredLayouts = layoutModules.filter(Boolean) as TModule[];
-  const layoutMetadataPromises: Promise<Metadata | null>[] = [];
-  let accumulatedMetadata = Promise.resolve<Metadata>({});
-
-  for (let index = 0; index < filteredLayouts.length; index++) {
-    const parentForLayout = accumulatedMetadata;
-    const metadataPromise = resolveModuleMetadata(
-      filteredLayouts[index],
-      params,
-      undefined,
-      parentForLayout,
-    ).catch((error) => {
-      console.error("[vinext] Layout generateMetadata() failed:", error);
-      return null;
-    });
-    layoutMetadataPromises.push(metadataPromise);
-    accumulatedMetadata = metadataPromise.then(async (metadataResult) => {
-      if (metadataResult) {
-        return mergeMetadata([await parentForLayout, metadataResult]);
-      }
-      return parentForLayout;
-    });
-  }
-
-  const [metadataResults, viewportResults] = await Promise.all([
-    Promise.all(layoutMetadataPromises),
-    Promise.all(
-      filteredLayouts.map((layoutModule) =>
-        resolveModuleViewport(layoutModule, params).catch((error) => {
-          console.error("[vinext] Layout generateViewport() failed:", error);
-          return null;
-        }),
-      ),
-    ),
-  ]);
-
-  const metadataList = metadataResults.filter(Boolean) as Metadata[];
-  const viewportList = viewportResults.filter(Boolean) as Viewport[];
-
-  return {
-    metadata: metadataList.length > 0 ? mergeMetadata(metadataList) : null,
-    viewport: mergeViewport(viewportList),
-  };
-}
-
 function wrapRenderedBoundaryElement<TModule extends AppPageModule>(
   options: Pick<
     AppPageBoundaryRenderCommonOptions<TModule>,
@@ -319,10 +262,12 @@ export async function renderAppPageHttpAccessFallback<TModule extends AppPageMod
   }
 
   const layoutModules = options.layoutModules ?? options.route?.layouts ?? options.rootLayouts;
-  const { metadata, viewport } = await resolveAppPageLayoutHead(
+  const { metadata, viewport } = await resolveAppPageHead({
     layoutModules,
-    options.matchedParams,
-  );
+    layoutTreePositions: options.route?.layoutTreePositions,
+    params: options.matchedParams,
+    routeSegments: options.route?.routeSegments,
+  });
 
   const headElements: ReactNode[] = [
     createElement("meta", { charSet: "utf-8", key: "charset" }),
diff --git a/packages/vinext/src/server/app-page-boundary.ts b/packages/vinext/src/server/app-page-boundary.ts
index 9c7c0455e..02237821d 100644
--- a/packages/vinext/src/server/app-page-boundary.ts
+++ b/packages/vinext/src/server/app-page-boundary.ts
@@ -1,4 +1,5 @@
 import { mergeMiddlewareResponseHeaders } from "./middleware-response-headers.js";
+import { resolveAppPageSegmentParams } from "./app-page-params.js";
 
 export type AppPageParams = Record<string, string | string[]>;
 
@@ -13,6 +14,17 @@ type ResolveAppPageHttpAccessBoundaryComponentOptions<TModule, TComponent> = {
   statusCode: number;
 };
 
+type ResolveAppPageParentHttpAccessBoundaryModuleOptions<TModule> = {
+  layoutIndex: number;
+  rootForbiddenModule?: TModule | null;
+  rootNotFoundModule?: TModule | null;
+  rootUnauthorizedModule?: TModule | null;
+  routeForbiddenModules?: readonly (TModule | null | undefined)[] | null;
+  routeNotFoundModules?: readonly (TModule | null | undefined)[] | null;
+  routeUnauthorizedModules?: readonly (TModule | null | undefined)[] | null;
+  statusCode: number;
+};
+
 type ResolveAppPageErrorBoundaryOptions<TModule, TComponent> = {
   getDefaultExport: (module: TModule | null | undefined) => TComponent | null | undefined;
   globalErrorModule?: TModule | null;
@@ -93,6 +105,32 @@ export function resolveAppPageHttpAccessBoundaryComponent<TModule, TComponent>(
   return options.getDefaultExport(boundaryModule) ?? null;
 }
 
+export function resolveAppPageParentHttpAccessBoundaryModule<TModule>(
+  options: ResolveAppPageParentHttpAccessBoundaryModuleOptions<TModule>,
+): TModule | null {
+  let routeModules = options.routeNotFoundModules;
+  let rootModule = options.rootNotFoundModule;
+
+  if (options.statusCode === 403) {
+    routeModules = options.routeForbiddenModules;
+    rootModule = options.rootForbiddenModule;
+  } else if (options.statusCode === 401) {
+    routeModules = options.routeUnauthorizedModules;
+    rootModule = options.rootUnauthorizedModule;
+  }
+
+  if (routeModules) {
+    for (let index = options.layoutIndex - 1; index >= 0; index--) {
+      const module = routeModules[index];
+      if (module) {
+        return module;
+      }
+    }
+  }
+
+  return rootModule ?? null;
+}
+
 export function resolveAppPageErrorBoundary<TModule, TComponent>(
   options: ResolveAppPageErrorBoundaryOptions<TModule, TComponent>,
 ): ResolveAppPageErrorBoundaryResult<TComponent> {
@@ -141,14 +179,16 @@ export function wrapAppPageBoundaryElement<
   let element = options.element;
 
   if (!options.skipLayoutWrapping) {
-    const asyncParams = options.makeThenableParams(options.matchedParams);
-
     for (let index = options.layoutModules.length - 1; index >= 0; index--) {
       const layoutComponent = options.getDefaultExport(options.layoutModules[index]);
       if (!layoutComponent) {
         continue;
       }
 
+      const treePosition = options.layoutTreePositions ? options.layoutTreePositions[index] : 0;
+      const asyncParams = options.makeThenableParams(
+        resolveAppPageSegmentParams(options.routeSegments, treePosition, options.matchedParams),
+      );
       element = options.renderLayout(layoutComponent, element, asyncParams);
 
       if (
@@ -156,7 +196,6 @@ export function wrapAppPageBoundaryElement<
         options.renderLayoutSegmentProvider &&
         options.resolveChildSegments
       ) {
-        const treePosition = options.layoutTreePositions ? options.layoutTreePositions[index] : 0;
         const childSegments = options.resolveChildSegments(
           options.routeSegments ?? [],
           treePosition,
diff --git a/packages/vinext/src/server/app-page-head.ts b/packages/vinext/src/server/app-page-head.ts
new file mode 100644
index 000000000..feb042470
--- /dev/null
+++ b/packages/vinext/src/server/app-page-head.ts
@@ -0,0 +1,141 @@
+import {
+  mergeMetadata,
+  mergeViewport,
+  resolveModuleMetadata,
+  resolveModuleViewport,
+  type Metadata,
+  type Viewport,
+} from "../shims/metadata.js";
+import type { AppPageParams } from "./app-page-boundary.js";
+import { resolveAppPageSegmentParams } from "./app-page-params.js";
+
+type AppPageHeadModule = Record<string, unknown>;
+type AppPageSearchParamsObject = Record<string, string | string[]>;
+
+type ResolveAppPageHeadOptions<TModule extends AppPageHeadModule> = {
+  layoutModules: readonly (TModule | null | undefined)[];
+  layoutTreePositions?: readonly number[] | null;
+  pageModule?: TModule | null;
+  params: AppPageParams;
+  routeSegments?: readonly string[] | null;
+  searchParams?: URLSearchParams | null;
+};
+
+type ResolveAppPageHeadResult = {
+  hasSearchParams: boolean;
+  metadata: Metadata | null;
+  searchParamsObject: AppPageSearchParamsObject;
+  viewport: Viewport;
+};
+
+type AppPageSearchParamsCollection = {
+  hasSearchParams: boolean;
+  searchParamsObject: AppPageSearchParamsObject;
+};
+
+function isMetadata(value: Metadata | null): value is Metadata {
+  return value !== null;
+}
+
+function isViewport(value: Viewport | null): value is Viewport {
+  return value !== null;
+}
+
+export function collectAppPageSearchParams(
+  searchParams: URLSearchParams | null | undefined,
+): AppPageSearchParamsCollection {
+  const searchParamsObject: AppPageSearchParamsObject = Object.create(null);
+  let hasSearchParams = false;
+
+  if (!searchParams) {
+    return { hasSearchParams, searchParamsObject };
+  }
+
+  searchParams.forEach((value, key) => {
+    hasSearchParams = true;
+    const current = searchParamsObject[key];
+    if (Array.isArray(current)) {
+      searchParamsObject[key] = [...current, value];
+      return;
+    }
+    if (current !== undefined) {
+      searchParamsObject[key] = [current, value];
+      return;
+    }
+    searchParamsObject[key] = value;
+  });
+
+  return { hasSearchParams, searchParamsObject };
+}
+
+export async function resolveAppPageHead<TModule extends AppPageHeadModule>(
+  options: ResolveAppPageHeadOptions<TModule>,
+): Promise<ResolveAppPageHeadResult> {
+  const { hasSearchParams, searchParamsObject } = collectAppPageSearchParams(options.searchParams);
+  const layoutMetadataPromises: Promise<Metadata | null>[] = [];
+  const layoutViewportPromises: Promise<Viewport | null>[] = [];
+  let accumulatedMetadata = Promise.resolve<Metadata>({});
+
+  for (let index = 0; index < options.layoutModules.length; index++) {
+    const layoutModule = options.layoutModules[index];
+    if (!layoutModule) {
+      continue;
+    }
+
+    const parentForLayout = accumulatedMetadata;
+    const layoutParams = resolveAppPageSegmentParams(
+      options.routeSegments,
+      options.layoutTreePositions?.[index] ?? 0,
+      options.params,
+    );
+    const metadataPromise = resolveModuleMetadata(
+      layoutModule,
+      layoutParams,
+      undefined,
+      parentForLayout,
+    );
+    layoutMetadataPromises.push(metadataPromise);
+    layoutViewportPromises.push(resolveModuleViewport(layoutModule, layoutParams));
+    accumulatedMetadata = metadataPromise.then(async (metadataResult) =>
+      metadataResult ? mergeMetadata([await parentForLayout, metadataResult]) : parentForLayout,
+    );
+    // This parent chain can reject before a page's generateMetadata awaits it.
+    // The original metadataPromise remains in Promise.all below, so errors still
+    // propagate while avoiding process-level unhandled rejections.
+    void accumulatedMetadata.catch(() => null);
+  }
+
+  const pageParentPromise = accumulatedMetadata;
+  const [layoutMetadataResults, layoutViewportResults, pageMetadata, pageViewport] =
+    await Promise.all([
+      Promise.all(layoutMetadataPromises),
+      Promise.all(layoutViewportPromises),
+      options.pageModule
+        ? resolveModuleMetadata(
+            options.pageModule,
+            options.params,
+            searchParamsObject,
+            pageParentPromise,
+          )
+        : Promise.resolve(null),
+      options.pageModule
+        ? resolveModuleViewport(options.pageModule, options.params)
+        : Promise.resolve(null),
+    ]);
+
+  const metadataList = [
+    ...layoutMetadataResults.filter(isMetadata),
+    ...(pageMetadata ? [pageMetadata] : []),
+  ];
+  const viewportList = [
+    ...layoutViewportResults.filter(isViewport),
+    ...(pageViewport ? [pageViewport] : []),
+  ];
+
+  return {
+    hasSearchParams,
+    metadata: metadataList.length > 0 ? mergeMetadata(metadataList) : null,
+    searchParamsObject,
+    viewport: mergeViewport(viewportList),
+  };
+}
diff --git a/packages/vinext/src/server/app-page-params.ts b/packages/vinext/src/server/app-page-params.ts
new file mode 100644
index 000000000..3dcd75263
--- /dev/null
+++ b/packages/vinext/src/server/app-page-params.ts
@@ -0,0 +1,53 @@
+import type { AppPageParams } from "./app-page-boundary.js";
+
+function getSegmentParamName(segment: string): string | null {
+  if (segment.startsWith("[[...") && segment.endsWith("]]") && segment.length > 7) {
+    return segment.slice(5, -2);
+  }
+
+  if (segment.startsWith("[...") && segment.endsWith("]") && segment.length > 5) {
+    return segment.slice(4, -1);
+  }
+
+  if (
+    segment.startsWith("[") &&
+    segment.endsWith("]") &&
+    !segment.includes(".") &&
+    segment.length > 2
+  ) {
+    return segment.slice(1, -1);
+  }
+
+  return null;
+}
+
+function isEmptyOptionalCatchAll(segment: string, paramValue: string | string[]): boolean {
+  return segment.startsWith("[[...") && Array.isArray(paramValue) && paramValue.length === 0;
+}
+
+export function resolveAppPageSegmentParams(
+  routeSegments: readonly string[] | null | undefined,
+  treePosition: number,
+  matchedParams: AppPageParams,
+): AppPageParams {
+  const segmentParams: AppPageParams = {};
+  const segments = routeSegments ?? [];
+  const end = Math.min(Math.max(treePosition, 0), segments.length);
+
+  for (let index = 0; index < end; index++) {
+    const segment = segments[index];
+    const paramName = getSegmentParamName(segment);
+    if (!paramName) {
+      continue;
+    }
+
+    const paramValue = matchedParams[paramName];
+    if (paramValue === undefined || isEmptyOptionalCatchAll(segment, paramValue)) {
+      continue;
+    }
+
+    segmentParams[paramName] = paramValue;
+  }
+
+  return segmentParams;
+}
diff --git a/packages/vinext/src/server/app-page-route-wiring.tsx b/packages/vinext/src/server/app-page-route-wiring.tsx
index e08ce2ce1..fd2ba12d0 100644
--- a/packages/vinext/src/server/app-page-route-wiring.tsx
+++ b/packages/vinext/src/server/app-page-route-wiring.tsx
@@ -19,6 +19,7 @@ import {
   renderWithAppDependencyBarrier,
   type AppRenderDependency,
 } from "./app-render-dependency.js";
+import { resolveAppPageSegmentParams } from "./app-page-params.js";
 
 type AppPageComponentProps = {
   children?: ReactNode;
@@ -329,7 +330,6 @@ export function buildAppPageElements<
   const templateDependenciesById = new Map<string, AppRenderDependency>();
   const templateDependenciesBeforeById = new Map<string, AppRenderDependency[]>();
   const pageDependencies: AppRenderDependency[] = [];
-  const routeThenableParams = options.makeThenableParams(options.matchedParams);
   const rootLayoutTreePath = layoutEntries[0]?.treePath ?? null;
   const slotNameCounts = new Map<string, number>();
   for (const slot of Object.values(options.route.slots ?? {})) {
@@ -421,7 +421,13 @@ export function buildAppPageElements<
     }
 
     const layoutProps: Record<string, unknown> = {
-      params: routeThenableParams,
+      params: options.makeThenableParams(
+        resolveAppPageSegmentParams(
+          options.route.routeSegments,
+          layoutEntry.treePosition,
+          options.matchedParams,
+        ),
+      ),
     };
 
     for (const slot of Object.values(options.route.slots ?? {})) {
diff --git a/packages/vinext/src/shims/metadata.tsx b/packages/vinext/src/shims/metadata.tsx
index bb1c0acc4..3f3b2b424 100644
--- a/packages/vinext/src/shims/metadata.tsx
+++ b/packages/vinext/src/shims/metadata.tsx
@@ -354,7 +354,7 @@ export function mergeMetadata(metadataList: Metadata[]): Metadata {
 export async function resolveModuleMetadata(
   mod: Record<string, unknown>,
   params: Record<string, string | string[]> = {},
-  searchParams?: Record<string, string>,
+  searchParams?: Record<string, string | string[]>,
   parent: Promise<Metadata> = Promise.resolve({}),
 ): Promise<Metadata | null> {
   if (typeof mod.generateMetadata === "function") {
diff --git a/tests/__snapshots__/entry-templates.test.ts.snap b/tests/__snapshots__/entry-templates.test.ts.snap
index 984653084..62ee1c06a 100644
--- a/tests/__snapshots__/entry-templates.test.ts.snap
+++ b/tests/__snapshots__/entry-templates.test.ts.snap
@@ -46,7 +46,6 @@ import { createElement } from "react";
 import { setNavigationContext as _setNavigationContextOrig, getNavigationContext as _getNavigationContext } from "next/navigation";
 import { setHeadersContext, headersContextFromRequest, getDraftModeCookieHeader, getAndClearPendingCookies, consumeDynamicUsage, markDynamicUsage, applyMiddlewareRequestHeaders, getHeadersContext, setHeadersAccessPhase } from "next/headers";
 import { NextRequest, NextFetchEvent } from "next/server";
-import { mergeMetadata, resolveModuleMetadata, mergeViewport, resolveModuleViewport } from "vinext/metadata";
 
 
 
@@ -78,6 +77,9 @@ import {
   resolveAppPageSpecialError as __resolveAppPageSpecialError,
   teeAppPageRscStreamForCapture as __teeAppPageRscStreamForCapture,
 } from "<ROOT>/packages/vinext/src/server/app-page-execution.js";
+import {
+  resolveAppPageParentHttpAccessBoundaryModule as __resolveAppPageParentHttpAccessBoundaryModule,
+} from "<ROOT>/packages/vinext/src/server/app-page-boundary.js";
 import {
   renderAppPageErrorBoundary as __renderAppPageErrorBoundary,
   renderAppPageHttpAccessFallback as __renderAppPageHttpAccessFallback,
@@ -91,6 +93,13 @@ import {
   createAppPageTreePath as __createAppPageTreePath,
   resolveAppPageChildSegments as __resolveAppPageChildSegments,
 } from "<ROOT>/packages/vinext/src/server/app-page-route-wiring.js";
+import {
+  resolveAppPageSegmentParams as __resolveAppPageSegmentParams,
+} from "<ROOT>/packages/vinext/src/server/app-page-params.js";
+import {
+  collectAppPageSearchParams as __collectAppPageSearchParams,
+  resolveAppPageHead as __resolveAppPageHead,
+} from "<ROOT>/packages/vinext/src/server/app-page-head.js";
 import {
   renderAppPageLifecycle as __renderAppPageLifecycle,
 } from "<ROOT>/packages/vinext/src/server/app-page-render.js";
@@ -464,7 +473,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(1), // evaluated once at module load
@@ -489,7 +500,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(2), // evaluated once at module load
@@ -514,7 +527,9 @@ const routes = [
     notFound: null,
     notFounds: [null, null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(3), // evaluated once at module load
@@ -539,7 +554,9 @@ const routes = [
     notFound: mod_10,
     notFounds: [null, mod_10],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   }
 ];
 const _routeTrie = _buildRouteTrie(routes);
@@ -778,83 +795,18 @@ async function buildPageElements(route, params, routePath, pageRequest) {
     };
   }
 
-  // Resolve metadata and viewport from layouts and page.
-  //
-  // generateMetadata() accepts a "parent" (Promise of ResolvedMetadata) as its
-  // second argument (Next.js 13+). The parent resolves to the accumulated
-  // merged metadata of all ancestor segments, enabling patterns like:
-  //
-  //   const previousImages = (await parent).openGraph?.images ?? []
-  //   return { openGraph: { images: ['/new-image.jpg', ...previousImages] } }
-  //
-  // Next.js uses an eager-execution-with-serial-resolution approach:
-  // all generateMetadata() calls are kicked off concurrently, but each
-  // segment's "parent" promise resolves only after the preceding segment's
-  // metadata is resolved and merged. This preserves concurrency for I/O-bound
-  // work while guaranteeing that parent data is available when needed.
-  //
-  // We build a chain: layoutParentPromises[0] = Promise.resolve({}) (no parent
-  // for root layout), layoutParentPromises[i+1] resolves to merge(layouts[0..i]),
-  // and pageParentPromise resolves to merge(all layouts).
-  //
-  // IMPORTANT: Layout metadata errors are swallowed (.catch(() => null)) because
-  // a layout's generateMetadata() failing should not crash the page.
-  // Page metadata errors are NOT swallowed — if the page's generateMetadata()
-  // throws, the error propagates out of buildPageElement() so the caller can
-  // route it to the nearest error.tsx boundary (or global-error.tsx).
-  const layoutMods = route.layouts.filter(Boolean);
-
-  // Convert URLSearchParams → plain object for page generateMetadata() and
-  // pageProps.searchParams. Built before the layout loop so the page metadata
-  // call (below) and pageProps can reference the same object.
-  // NOTE: Layouts do NOT receive searchParams in generateMetadata() — only
-  // pages do. This matches Next.js behavior (resolve-metadata.ts:777).
-  const spObj = Object.create(null);
-  let hasSearchParams = false;
-  if (searchParams && searchParams.forEach) {
-    searchParams.forEach(function(v, k) {
-      hasSearchParams = true;
-      if (k in spObj) {
-        spObj[k] = Array.isArray(spObj[k]) ? spObj[k].concat(v) : [spObj[k], v];
-      } else {
-        spObj[k] = v;
-      }
-    });
-  }
-
-  // Build the parent promise chain and kick off metadata resolution in one pass.
-  // Each layout module is called exactly once. layoutMetaPromises[i] is the
-  // promise for layout[i]'s own metadata result.
-  //
-  // All calls are kicked off immediately (concurrent I/O), but each layout's
-  // "parent" promise only resolves after the preceding layout's metadata is done.
-  const layoutMetaPromises = [];
-  let accumulatedMetaPromise = Promise.resolve({});
-  for (let i = 0; i < layoutMods.length; i++) {
-    const parentForThisLayout = accumulatedMetaPromise;
-    // Kick off this layout's metadata resolution now (concurrent with others).
-    const metaPromise = resolveModuleMetadata(layoutMods[i], params, undefined, parentForThisLayout)
-      .catch((err) => { console.error("[vinext] Layout generateMetadata() failed:", err); return null; });
-    layoutMetaPromises.push(metaPromise);
-    // Advance accumulator: resolves to merged(layouts[0..i]) once layout[i] is done.
-    accumulatedMetaPromise = metaPromise.then(async (result) =>
-      result ? mergeMetadata([await parentForThisLayout, result]) : await parentForThisLayout
-    );
-  }
-  // Page's parent is the fully-accumulated layout metadata.
-  const pageParentPromise = accumulatedMetaPromise;
-
-  const [layoutMetaResults, layoutVpResults, pageMeta, pageVp] = await Promise.all([
-    Promise.all(layoutMetaPromises),
-    Promise.all(layoutMods.map((mod) => resolveModuleViewport(mod, params).catch((err) => { console.error("[vinext] Layout generateViewport() failed:", err); return null; }))),
-    route.page ? resolveModuleMetadata(route.page, params, spObj, pageParentPromise) : Promise.resolve(null),
-    route.page ? resolveModuleViewport(route.page, params) : Promise.resolve(null),
-  ]);
-
-  const metadataList = [...layoutMetaResults.filter(Boolean), ...(pageMeta ? [pageMeta] : [])];
-  const viewportList = [...layoutVpResults.filter(Boolean), ...(pageVp ? [pageVp] : [])];
-  const resolvedMetadata = metadataList.length > 0 ? mergeMetadata(metadataList) : null;
-  const resolvedViewport = mergeViewport(viewportList);
+  const __headResult = await __resolveAppPageHead({
+    layoutModules: route.layouts,
+    layoutTreePositions: route.layoutTreePositions,
+    pageModule: route.page,
+    params,
+    routeSegments: route.routeSegments,
+    searchParams,
+  });
+  const spObj = __headResult.searchParamsObject;
+  const hasSearchParams = __headResult.hasSearchParams;
+  const resolvedMetadata = __headResult.metadata;
+  const resolvedViewport = __headResult.viewport;
 
   // Build the route tree from the leaf page, then delegate the boundary/layout/
   // template/segment wiring to a typed runtime helper so the generated entry
@@ -2214,7 +2166,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
   // Note: CSS is automatically injected by @vitejs/plugin-rsc's
   // rscCssTransform — no manual loadCss() call needed.
   const _hasLoadingBoundary = !!(route.loading && route.loading.default);
-  const _asyncLayoutParams = makeThenableParams(params);
+  const _asyncRouteParams = makeThenableParams(params);
   return __renderAppPageLifecycle({
     cleanPathname,
     clearRequestContext() {
@@ -2257,22 +2209,21 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
     probeLayoutAt(li) {
       const LayoutComp = route.layouts[li]?.default;
       if (!LayoutComp) return null;
-      return LayoutComp({ params: _asyncLayoutParams, children: null });
+      return LayoutComp({
+        params: makeThenableParams(__resolveAppPageSegmentParams(
+          route.routeSegments,
+          route.layoutTreePositions?.[li] ?? 0,
+          params,
+        )),
+        children: null,
+      });
     },
     probePage() {
       if (!PageComponent) return null;
-      const _probeSearchObj = {};
-      url.searchParams.forEach(function(v, k) {
-        if (k in _probeSearchObj) {
-          _probeSearchObj[k] = Array.isArray(_probeSearchObj[k])
-            ? _probeSearchObj[k].concat(v)
-            : [_probeSearchObj[k], v];
-        } else {
-          _probeSearchObj[k] = v;
-        }
-      });
-      const _asyncSearchParams = makeThenableParams(_probeSearchObj);
-      return PageComponent({ params: _asyncLayoutParams, searchParams: _asyncSearchParams });
+      const _asyncSearchParams = makeThenableParams(
+        __collectAppPageSearchParams(url.searchParams).searchParamsObject,
+      );
+      return PageComponent({ params: _asyncRouteParams, searchParams: _asyncSearchParams });
     },
     classification: {
       getLayoutId(index) {
@@ -2307,19 +2258,16 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
         },
         middlewareContext: _mwCtx,
         renderFallbackPage(statusCode) {
-          // Find the not-found component from the parent level (the boundary that
-          // would catch this in Next.js). Walk up from the throwing layout to find
-          // the nearest not-found at a parent layout's directory.
-          let parentNotFound = null;
-          if (route.notFounds) {
-            for (let pi = li - 1; pi >= 0; pi--) {
-              if (route.notFounds[pi]?.default) {
-                parentNotFound = route.notFounds[pi].default;
-                break;
-              }
-            }
-          }
-          if (!parentNotFound) parentNotFound = null;
+          const parentBoundary = __resolveAppPageParentHttpAccessBoundaryModule({
+            layoutIndex: li,
+            rootForbiddenModule: null,
+            rootNotFoundModule: null,
+            rootUnauthorizedModule: null,
+            routeForbiddenModules: route.forbiddens,
+            routeNotFoundModules: route.notFounds,
+            routeUnauthorizedModules: route.unauthorizeds,
+            statusCode,
+          })?.default ?? null;
           const parentLayouts = route.layouts.slice(0, li);
           return renderHTTPAccessFallbackPage(
             route,
@@ -2327,7 +2275,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
             isRscRequest,
             request,
             {
-              boundaryComponent: parentNotFound,
+              boundaryComponent: parentBoundary,
               layouts: parentLayouts,
               matchedParams: params,
             },
@@ -2435,7 +2383,6 @@ import { createElement } from "react";
 import { setNavigationContext as _setNavigationContextOrig, getNavigationContext as _getNavigationContext } from "next/navigation";
 import { setHeadersContext, headersContextFromRequest, getDraftModeCookieHeader, getAndClearPendingCookies, consumeDynamicUsage, markDynamicUsage, applyMiddlewareRequestHeaders, getHeadersContext, setHeadersAccessPhase } from "next/headers";
 import { NextRequest, NextFetchEvent } from "next/server";
-import { mergeMetadata, resolveModuleMetadata, mergeViewport, resolveModuleViewport } from "vinext/metadata";
 
 
 
@@ -2467,6 +2414,9 @@ import {
   resolveAppPageSpecialError as __resolveAppPageSpecialError,
   teeAppPageRscStreamForCapture as __teeAppPageRscStreamForCapture,
 } from "<ROOT>/packages/vinext/src/server/app-page-execution.js";
+import {
+  resolveAppPageParentHttpAccessBoundaryModule as __resolveAppPageParentHttpAccessBoundaryModule,
+} from "<ROOT>/packages/vinext/src/server/app-page-boundary.js";
 import {
   renderAppPageErrorBoundary as __renderAppPageErrorBoundary,
   renderAppPageHttpAccessFallback as __renderAppPageHttpAccessFallback,
@@ -2480,6 +2430,13 @@ import {
   createAppPageTreePath as __createAppPageTreePath,
   resolveAppPageChildSegments as __resolveAppPageChildSegments,
 } from "<ROOT>/packages/vinext/src/server/app-page-route-wiring.js";
+import {
+  resolveAppPageSegmentParams as __resolveAppPageSegmentParams,
+} from "<ROOT>/packages/vinext/src/server/app-page-params.js";
+import {
+  collectAppPageSearchParams as __collectAppPageSearchParams,
+  resolveAppPageHead as __resolveAppPageHead,
+} from "<ROOT>/packages/vinext/src/server/app-page-head.js";
 import {
   renderAppPageLifecycle as __renderAppPageLifecycle,
 } from "<ROOT>/packages/vinext/src/server/app-page-render.js";
@@ -2853,7 +2810,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(1), // evaluated once at module load
@@ -2878,7 +2837,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(2), // evaluated once at module load
@@ -2903,7 +2864,9 @@ const routes = [
     notFound: null,
     notFounds: [null, null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(3), // evaluated once at module load
@@ -2928,7 +2891,9 @@ const routes = [
     notFound: mod_10,
     notFounds: [null, mod_10],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   }
 ];
 const _routeTrie = _buildRouteTrie(routes);
@@ -3167,83 +3132,18 @@ async function buildPageElements(route, params, routePath, pageRequest) {
     };
   }
 
-  // Resolve metadata and viewport from layouts and page.
-  //
-  // generateMetadata() accepts a "parent" (Promise of ResolvedMetadata) as its
-  // second argument (Next.js 13+). The parent resolves to the accumulated
-  // merged metadata of all ancestor segments, enabling patterns like:
-  //
-  //   const previousImages = (await parent).openGraph?.images ?? []
-  //   return { openGraph: { images: ['/new-image.jpg', ...previousImages] } }
-  //
-  // Next.js uses an eager-execution-with-serial-resolution approach:
-  // all generateMetadata() calls are kicked off concurrently, but each
-  // segment's "parent" promise resolves only after the preceding segment's
-  // metadata is resolved and merged. This preserves concurrency for I/O-bound
-  // work while guaranteeing that parent data is available when needed.
-  //
-  // We build a chain: layoutParentPromises[0] = Promise.resolve({}) (no parent
-  // for root layout), layoutParentPromises[i+1] resolves to merge(layouts[0..i]),
-  // and pageParentPromise resolves to merge(all layouts).
-  //
-  // IMPORTANT: Layout metadata errors are swallowed (.catch(() => null)) because
-  // a layout's generateMetadata() failing should not crash the page.
-  // Page metadata errors are NOT swallowed — if the page's generateMetadata()
-  // throws, the error propagates out of buildPageElement() so the caller can
-  // route it to the nearest error.tsx boundary (or global-error.tsx).
-  const layoutMods = route.layouts.filter(Boolean);
-
-  // Convert URLSearchParams → plain object for page generateMetadata() and
-  // pageProps.searchParams. Built before the layout loop so the page metadata
-  // call (below) and pageProps can reference the same object.
-  // NOTE: Layouts do NOT receive searchParams in generateMetadata() — only
-  // pages do. This matches Next.js behavior (resolve-metadata.ts:777).
-  const spObj = Object.create(null);
-  let hasSearchParams = false;
-  if (searchParams && searchParams.forEach) {
-    searchParams.forEach(function(v, k) {
-      hasSearchParams = true;
-      if (k in spObj) {
-        spObj[k] = Array.isArray(spObj[k]) ? spObj[k].concat(v) : [spObj[k], v];
-      } else {
-        spObj[k] = v;
-      }
-    });
-  }
-
-  // Build the parent promise chain and kick off metadata resolution in one pass.
-  // Each layout module is called exactly once. layoutMetaPromises[i] is the
-  // promise for layout[i]'s own metadata result.
-  //
-  // All calls are kicked off immediately (concurrent I/O), but each layout's
-  // "parent" promise only resolves after the preceding layout's metadata is done.
-  const layoutMetaPromises = [];
-  let accumulatedMetaPromise = Promise.resolve({});
-  for (let i = 0; i < layoutMods.length; i++) {
-    const parentForThisLayout = accumulatedMetaPromise;
-    // Kick off this layout's metadata resolution now (concurrent with others).
-    const metaPromise = resolveModuleMetadata(layoutMods[i], params, undefined, parentForThisLayout)
-      .catch((err) => { console.error("[vinext] Layout generateMetadata() failed:", err); return null; });
-    layoutMetaPromises.push(metaPromise);
-    // Advance accumulator: resolves to merged(layouts[0..i]) once layout[i] is done.
-    accumulatedMetaPromise = metaPromise.then(async (result) =>
-      result ? mergeMetadata([await parentForThisLayout, result]) : await parentForThisLayout
-    );
-  }
-  // Page's parent is the fully-accumulated layout metadata.
-  const pageParentPromise = accumulatedMetaPromise;
-
-  const [layoutMetaResults, layoutVpResults, pageMeta, pageVp] = await Promise.all([
-    Promise.all(layoutMetaPromises),
-    Promise.all(layoutMods.map((mod) => resolveModuleViewport(mod, params).catch((err) => { console.error("[vinext] Layout generateViewport() failed:", err); return null; }))),
-    route.page ? resolveModuleMetadata(route.page, params, spObj, pageParentPromise) : Promise.resolve(null),
-    route.page ? resolveModuleViewport(route.page, params) : Promise.resolve(null),
-  ]);
-
-  const metadataList = [...layoutMetaResults.filter(Boolean), ...(pageMeta ? [pageMeta] : [])];
-  const viewportList = [...layoutVpResults.filter(Boolean), ...(pageVp ? [pageVp] : [])];
-  const resolvedMetadata = metadataList.length > 0 ? mergeMetadata(metadataList) : null;
-  const resolvedViewport = mergeViewport(viewportList);
+  const __headResult = await __resolveAppPageHead({
+    layoutModules: route.layouts,
+    layoutTreePositions: route.layoutTreePositions,
+    pageModule: route.page,
+    params,
+    routeSegments: route.routeSegments,
+    searchParams,
+  });
+  const spObj = __headResult.searchParamsObject;
+  const hasSearchParams = __headResult.hasSearchParams;
+  const resolvedMetadata = __headResult.metadata;
+  const resolvedViewport = __headResult.viewport;
 
   // Build the route tree from the leaf page, then delegate the boundary/layout/
   // template/segment wiring to a typed runtime helper so the generated entry
@@ -4609,7 +4509,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
   // Note: CSS is automatically injected by @vitejs/plugin-rsc's
   // rscCssTransform — no manual loadCss() call needed.
   const _hasLoadingBoundary = !!(route.loading && route.loading.default);
-  const _asyncLayoutParams = makeThenableParams(params);
+  const _asyncRouteParams = makeThenableParams(params);
   return __renderAppPageLifecycle({
     cleanPathname,
     clearRequestContext() {
@@ -4652,22 +4552,21 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
     probeLayoutAt(li) {
       const LayoutComp = route.layouts[li]?.default;
       if (!LayoutComp) return null;
-      return LayoutComp({ params: _asyncLayoutParams, children: null });
+      return LayoutComp({
+        params: makeThenableParams(__resolveAppPageSegmentParams(
+          route.routeSegments,
+          route.layoutTreePositions?.[li] ?? 0,
+          params,
+        )),
+        children: null,
+      });
     },
     probePage() {
       if (!PageComponent) return null;
-      const _probeSearchObj = {};
-      url.searchParams.forEach(function(v, k) {
-        if (k in _probeSearchObj) {
-          _probeSearchObj[k] = Array.isArray(_probeSearchObj[k])
-            ? _probeSearchObj[k].concat(v)
-            : [_probeSearchObj[k], v];
-        } else {
-          _probeSearchObj[k] = v;
-        }
-      });
-      const _asyncSearchParams = makeThenableParams(_probeSearchObj);
-      return PageComponent({ params: _asyncLayoutParams, searchParams: _asyncSearchParams });
+      const _asyncSearchParams = makeThenableParams(
+        __collectAppPageSearchParams(url.searchParams).searchParamsObject,
+      );
+      return PageComponent({ params: _asyncRouteParams, searchParams: _asyncSearchParams });
     },
     classification: {
       getLayoutId(index) {
@@ -4702,19 +4601,16 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
         },
         middlewareContext: _mwCtx,
         renderFallbackPage(statusCode) {
-          // Find the not-found component from the parent level (the boundary that
-          // would catch this in Next.js). Walk up from the throwing layout to find
-          // the nearest not-found at a parent layout's directory.
-          let parentNotFound = null;
-          if (route.notFounds) {
-            for (let pi = li - 1; pi >= 0; pi--) {
-              if (route.notFounds[pi]?.default) {
-                parentNotFound = route.notFounds[pi].default;
-                break;
-              }
-            }
-          }
-          if (!parentNotFound) parentNotFound = null;
+          const parentBoundary = __resolveAppPageParentHttpAccessBoundaryModule({
+            layoutIndex: li,
+            rootForbiddenModule: null,
+            rootNotFoundModule: null,
+            rootUnauthorizedModule: null,
+            routeForbiddenModules: route.forbiddens,
+            routeNotFoundModules: route.notFounds,
+            routeUnauthorizedModules: route.unauthorizeds,
+            statusCode,
+          })?.default ?? null;
           const parentLayouts = route.layouts.slice(0, li);
           return renderHTTPAccessFallbackPage(
             route,
@@ -4722,7 +4618,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
             isRscRequest,
             request,
             {
-              boundaryComponent: parentNotFound,
+              boundaryComponent: parentBoundary,
               layouts: parentLayouts,
               matchedParams: params,
             },
@@ -4830,7 +4726,6 @@ import { createElement } from "react";
 import { setNavigationContext as _setNavigationContextOrig, getNavigationContext as _getNavigationContext } from "next/navigation";
 import { setHeadersContext, headersContextFromRequest, getDraftModeCookieHeader, getAndClearPendingCookies, consumeDynamicUsage, markDynamicUsage, applyMiddlewareRequestHeaders, getHeadersContext, setHeadersAccessPhase } from "next/headers";
 import { NextRequest, NextFetchEvent } from "next/server";
-import { mergeMetadata, resolveModuleMetadata, mergeViewport, resolveModuleViewport } from "vinext/metadata";
 
 
 
@@ -4862,6 +4757,9 @@ import {
   resolveAppPageSpecialError as __resolveAppPageSpecialError,
   teeAppPageRscStreamForCapture as __teeAppPageRscStreamForCapture,
 } from "<ROOT>/packages/vinext/src/server/app-page-execution.js";
+import {
+  resolveAppPageParentHttpAccessBoundaryModule as __resolveAppPageParentHttpAccessBoundaryModule,
+} from "<ROOT>/packages/vinext/src/server/app-page-boundary.js";
 import {
   renderAppPageErrorBoundary as __renderAppPageErrorBoundary,
   renderAppPageHttpAccessFallback as __renderAppPageHttpAccessFallback,
@@ -4875,6 +4773,13 @@ import {
   createAppPageTreePath as __createAppPageTreePath,
   resolveAppPageChildSegments as __resolveAppPageChildSegments,
 } from "<ROOT>/packages/vinext/src/server/app-page-route-wiring.js";
+import {
+  resolveAppPageSegmentParams as __resolveAppPageSegmentParams,
+} from "<ROOT>/packages/vinext/src/server/app-page-params.js";
+import {
+  collectAppPageSearchParams as __collectAppPageSearchParams,
+  resolveAppPageHead as __resolveAppPageHead,
+} from "<ROOT>/packages/vinext/src/server/app-page-head.js";
 import {
   renderAppPageLifecycle as __renderAppPageLifecycle,
 } from "<ROOT>/packages/vinext/src/server/app-page-render.js";
@@ -5249,7 +5154,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(1), // evaluated once at module load
@@ -5274,7 +5181,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(2), // evaluated once at module load
@@ -5299,7 +5208,9 @@ const routes = [
     notFound: null,
     notFounds: [null, null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(3), // evaluated once at module load
@@ -5324,7 +5235,9 @@ const routes = [
     notFound: mod_10,
     notFounds: [null, mod_10],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   }
 ];
 const _routeTrie = _buildRouteTrie(routes);
@@ -5563,83 +5476,18 @@ async function buildPageElements(route, params, routePath, pageRequest) {
     };
   }
 
-  // Resolve metadata and viewport from layouts and page.
-  //
-  // generateMetadata() accepts a "parent" (Promise of ResolvedMetadata) as its
-  // second argument (Next.js 13+). The parent resolves to the accumulated
-  // merged metadata of all ancestor segments, enabling patterns like:
-  //
-  //   const previousImages = (await parent).openGraph?.images ?? []
-  //   return { openGraph: { images: ['/new-image.jpg', ...previousImages] } }
-  //
-  // Next.js uses an eager-execution-with-serial-resolution approach:
-  // all generateMetadata() calls are kicked off concurrently, but each
-  // segment's "parent" promise resolves only after the preceding segment's
-  // metadata is resolved and merged. This preserves concurrency for I/O-bound
-  // work while guaranteeing that parent data is available when needed.
-  //
-  // We build a chain: layoutParentPromises[0] = Promise.resolve({}) (no parent
-  // for root layout), layoutParentPromises[i+1] resolves to merge(layouts[0..i]),
-  // and pageParentPromise resolves to merge(all layouts).
-  //
-  // IMPORTANT: Layout metadata errors are swallowed (.catch(() => null)) because
-  // a layout's generateMetadata() failing should not crash the page.
-  // Page metadata errors are NOT swallowed — if the page's generateMetadata()
-  // throws, the error propagates out of buildPageElement() so the caller can
-  // route it to the nearest error.tsx boundary (or global-error.tsx).
-  const layoutMods = route.layouts.filter(Boolean);
-
-  // Convert URLSearchParams → plain object for page generateMetadata() and
-  // pageProps.searchParams. Built before the layout loop so the page metadata
-  // call (below) and pageProps can reference the same object.
-  // NOTE: Layouts do NOT receive searchParams in generateMetadata() — only
-  // pages do. This matches Next.js behavior (resolve-metadata.ts:777).
-  const spObj = Object.create(null);
-  let hasSearchParams = false;
-  if (searchParams && searchParams.forEach) {
-    searchParams.forEach(function(v, k) {
-      hasSearchParams = true;
-      if (k in spObj) {
-        spObj[k] = Array.isArray(spObj[k]) ? spObj[k].concat(v) : [spObj[k], v];
-      } else {
-        spObj[k] = v;
-      }
-    });
-  }
-
-  // Build the parent promise chain and kick off metadata resolution in one pass.
-  // Each layout module is called exactly once. layoutMetaPromises[i] is the
-  // promise for layout[i]'s own metadata result.
-  //
-  // All calls are kicked off immediately (concurrent I/O), but each layout's
-  // "parent" promise only resolves after the preceding layout's metadata is done.
-  const layoutMetaPromises = [];
-  let accumulatedMetaPromise = Promise.resolve({});
-  for (let i = 0; i < layoutMods.length; i++) {
-    const parentForThisLayout = accumulatedMetaPromise;
-    // Kick off this layout's metadata resolution now (concurrent with others).
-    const metaPromise = resolveModuleMetadata(layoutMods[i], params, undefined, parentForThisLayout)
-      .catch((err) => { console.error("[vinext] Layout generateMetadata() failed:", err); return null; });
-    layoutMetaPromises.push(metaPromise);
-    // Advance accumulator: resolves to merged(layouts[0..i]) once layout[i] is done.
-    accumulatedMetaPromise = metaPromise.then(async (result) =>
-      result ? mergeMetadata([await parentForThisLayout, result]) : await parentForThisLayout
-    );
-  }
-  // Page's parent is the fully-accumulated layout metadata.
-  const pageParentPromise = accumulatedMetaPromise;
-
-  const [layoutMetaResults, layoutVpResults, pageMeta, pageVp] = await Promise.all([
-    Promise.all(layoutMetaPromises),
-    Promise.all(layoutMods.map((mod) => resolveModuleViewport(mod, params).catch((err) => { console.error("[vinext] Layout generateViewport() failed:", err); return null; }))),
-    route.page ? resolveModuleMetadata(route.page, params, spObj, pageParentPromise) : Promise.resolve(null),
-    route.page ? resolveModuleViewport(route.page, params) : Promise.resolve(null),
-  ]);
-
-  const metadataList = [...layoutMetaResults.filter(Boolean), ...(pageMeta ? [pageMeta] : [])];
-  const viewportList = [...layoutVpResults.filter(Boolean), ...(pageVp ? [pageVp] : [])];
-  const resolvedMetadata = metadataList.length > 0 ? mergeMetadata(metadataList) : null;
-  const resolvedViewport = mergeViewport(viewportList);
+  const __headResult = await __resolveAppPageHead({
+    layoutModules: route.layouts,
+    layoutTreePositions: route.layoutTreePositions,
+    pageModule: route.page,
+    params,
+    routeSegments: route.routeSegments,
+    searchParams,
+  });
+  const spObj = __headResult.searchParamsObject;
+  const hasSearchParams = __headResult.hasSearchParams;
+  const resolvedMetadata = __headResult.metadata;
+  const resolvedViewport = __headResult.viewport;
 
   // Build the route tree from the leaf page, then delegate the boundary/layout/
   // template/segment wiring to a typed runtime helper so the generated entry
@@ -6999,7 +6847,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
   // Note: CSS is automatically injected by @vitejs/plugin-rsc's
   // rscCssTransform — no manual loadCss() call needed.
   const _hasLoadingBoundary = !!(route.loading && route.loading.default);
-  const _asyncLayoutParams = makeThenableParams(params);
+  const _asyncRouteParams = makeThenableParams(params);
   return __renderAppPageLifecycle({
     cleanPathname,
     clearRequestContext() {
@@ -7042,22 +6890,21 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
     probeLayoutAt(li) {
       const LayoutComp = route.layouts[li]?.default;
       if (!LayoutComp) return null;
-      return LayoutComp({ params: _asyncLayoutParams, children: null });
+      return LayoutComp({
+        params: makeThenableParams(__resolveAppPageSegmentParams(
+          route.routeSegments,
+          route.layoutTreePositions?.[li] ?? 0,
+          params,
+        )),
+        children: null,
+      });
     },
     probePage() {
       if (!PageComponent) return null;
-      const _probeSearchObj = {};
-      url.searchParams.forEach(function(v, k) {
-        if (k in _probeSearchObj) {
-          _probeSearchObj[k] = Array.isArray(_probeSearchObj[k])
-            ? _probeSearchObj[k].concat(v)
-            : [_probeSearchObj[k], v];
-        } else {
-          _probeSearchObj[k] = v;
-        }
-      });
-      const _asyncSearchParams = makeThenableParams(_probeSearchObj);
-      return PageComponent({ params: _asyncLayoutParams, searchParams: _asyncSearchParams });
+      const _asyncSearchParams = makeThenableParams(
+        __collectAppPageSearchParams(url.searchParams).searchParamsObject,
+      );
+      return PageComponent({ params: _asyncRouteParams, searchParams: _asyncSearchParams });
     },
     classification: {
       getLayoutId(index) {
@@ -7092,19 +6939,16 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
         },
         middlewareContext: _mwCtx,
         renderFallbackPage(statusCode) {
-          // Find the not-found component from the parent level (the boundary that
-          // would catch this in Next.js). Walk up from the throwing layout to find
-          // the nearest not-found at a parent layout's directory.
-          let parentNotFound = null;
-          if (route.notFounds) {
-            for (let pi = li - 1; pi >= 0; pi--) {
-              if (route.notFounds[pi]?.default) {
-                parentNotFound = route.notFounds[pi].default;
-                break;
-              }
-            }
-          }
-          if (!parentNotFound) parentNotFound = null;
+          const parentBoundary = __resolveAppPageParentHttpAccessBoundaryModule({
+            layoutIndex: li,
+            rootForbiddenModule: null,
+            rootNotFoundModule: null,
+            rootUnauthorizedModule: null,
+            routeForbiddenModules: route.forbiddens,
+            routeNotFoundModules: route.notFounds,
+            routeUnauthorizedModules: route.unauthorizeds,
+            statusCode,
+          })?.default ?? null;
           const parentLayouts = route.layouts.slice(0, li);
           return renderHTTPAccessFallbackPage(
             route,
@@ -7112,7 +6956,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
             isRscRequest,
             request,
             {
-              boundaryComponent: parentNotFound,
+              boundaryComponent: parentBoundary,
               layouts: parentLayouts,
               matchedParams: params,
             },
@@ -7220,7 +7064,6 @@ import { createElement } from "react";
 import { setNavigationContext as _setNavigationContextOrig, getNavigationContext as _getNavigationContext } from "next/navigation";
 import { setHeadersContext, headersContextFromRequest, getDraftModeCookieHeader, getAndClearPendingCookies, consumeDynamicUsage, markDynamicUsage, applyMiddlewareRequestHeaders, getHeadersContext, setHeadersAccessPhase } from "next/headers";
 import { NextRequest, NextFetchEvent } from "next/server";
-import { mergeMetadata, resolveModuleMetadata, mergeViewport, resolveModuleViewport } from "vinext/metadata";
 
 import * as _instrumentation from "/tmp/test/instrumentation.ts";
 
@@ -7252,6 +7095,9 @@ import {
   resolveAppPageSpecialError as __resolveAppPageSpecialError,
   teeAppPageRscStreamForCapture as __teeAppPageRscStreamForCapture,
 } from "<ROOT>/packages/vinext/src/server/app-page-execution.js";
+import {
+  resolveAppPageParentHttpAccessBoundaryModule as __resolveAppPageParentHttpAccessBoundaryModule,
+} from "<ROOT>/packages/vinext/src/server/app-page-boundary.js";
 import {
   renderAppPageErrorBoundary as __renderAppPageErrorBoundary,
   renderAppPageHttpAccessFallback as __renderAppPageHttpAccessFallback,
@@ -7265,6 +7111,13 @@ import {
   createAppPageTreePath as __createAppPageTreePath,
   resolveAppPageChildSegments as __resolveAppPageChildSegments,
 } from "<ROOT>/packages/vinext/src/server/app-page-route-wiring.js";
+import {
+  resolveAppPageSegmentParams as __resolveAppPageSegmentParams,
+} from "<ROOT>/packages/vinext/src/server/app-page-params.js";
+import {
+  collectAppPageSearchParams as __collectAppPageSearchParams,
+  resolveAppPageHead as __resolveAppPageHead,
+} from "<ROOT>/packages/vinext/src/server/app-page-head.js";
 import {
   renderAppPageLifecycle as __renderAppPageLifecycle,
 } from "<ROOT>/packages/vinext/src/server/app-page-render.js";
@@ -7668,7 +7521,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(1), // evaluated once at module load
@@ -7693,7 +7548,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(2), // evaluated once at module load
@@ -7718,7 +7575,9 @@ const routes = [
     notFound: null,
     notFounds: [null, null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(3), // evaluated once at module load
@@ -7743,7 +7602,9 @@ const routes = [
     notFound: mod_10,
     notFounds: [null, mod_10],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   }
 ];
 const _routeTrie = _buildRouteTrie(routes);
@@ -7982,83 +7843,18 @@ async function buildPageElements(route, params, routePath, pageRequest) {
     };
   }
 
-  // Resolve metadata and viewport from layouts and page.
-  //
-  // generateMetadata() accepts a "parent" (Promise of ResolvedMetadata) as its
-  // second argument (Next.js 13+). The parent resolves to the accumulated
-  // merged metadata of all ancestor segments, enabling patterns like:
-  //
-  //   const previousImages = (await parent).openGraph?.images ?? []
-  //   return { openGraph: { images: ['/new-image.jpg', ...previousImages] } }
-  //
-  // Next.js uses an eager-execution-with-serial-resolution approach:
-  // all generateMetadata() calls are kicked off concurrently, but each
-  // segment's "parent" promise resolves only after the preceding segment's
-  // metadata is resolved and merged. This preserves concurrency for I/O-bound
-  // work while guaranteeing that parent data is available when needed.
-  //
-  // We build a chain: layoutParentPromises[0] = Promise.resolve({}) (no parent
-  // for root layout), layoutParentPromises[i+1] resolves to merge(layouts[0..i]),
-  // and pageParentPromise resolves to merge(all layouts).
-  //
-  // IMPORTANT: Layout metadata errors are swallowed (.catch(() => null)) because
-  // a layout's generateMetadata() failing should not crash the page.
-  // Page metadata errors are NOT swallowed — if the page's generateMetadata()
-  // throws, the error propagates out of buildPageElement() so the caller can
-  // route it to the nearest error.tsx boundary (or global-error.tsx).
-  const layoutMods = route.layouts.filter(Boolean);
-
-  // Convert URLSearchParams → plain object for page generateMetadata() and
-  // pageProps.searchParams. Built before the layout loop so the page metadata
-  // call (below) and pageProps can reference the same object.
-  // NOTE: Layouts do NOT receive searchParams in generateMetadata() — only
-  // pages do. This matches Next.js behavior (resolve-metadata.ts:777).
-  const spObj = Object.create(null);
-  let hasSearchParams = false;
-  if (searchParams && searchParams.forEach) {
-    searchParams.forEach(function(v, k) {
-      hasSearchParams = true;
-      if (k in spObj) {
-        spObj[k] = Array.isArray(spObj[k]) ? spObj[k].concat(v) : [spObj[k], v];
-      } else {
-        spObj[k] = v;
-      }
-    });
-  }
-
-  // Build the parent promise chain and kick off metadata resolution in one pass.
-  // Each layout module is called exactly once. layoutMetaPromises[i] is the
-  // promise for layout[i]'s own metadata result.
-  //
-  // All calls are kicked off immediately (concurrent I/O), but each layout's
-  // "parent" promise only resolves after the preceding layout's metadata is done.
-  const layoutMetaPromises = [];
-  let accumulatedMetaPromise = Promise.resolve({});
-  for (let i = 0; i < layoutMods.length; i++) {
-    const parentForThisLayout = accumulatedMetaPromise;
-    // Kick off this layout's metadata resolution now (concurrent with others).
-    const metaPromise = resolveModuleMetadata(layoutMods[i], params, undefined, parentForThisLayout)
-      .catch((err) => { console.error("[vinext] Layout generateMetadata() failed:", err); return null; });
-    layoutMetaPromises.push(metaPromise);
-    // Advance accumulator: resolves to merged(layouts[0..i]) once layout[i] is done.
-    accumulatedMetaPromise = metaPromise.then(async (result) =>
-      result ? mergeMetadata([await parentForThisLayout, result]) : await parentForThisLayout
-    );
-  }
-  // Page's parent is the fully-accumulated layout metadata.
-  const pageParentPromise = accumulatedMetaPromise;
-
-  const [layoutMetaResults, layoutVpResults, pageMeta, pageVp] = await Promise.all([
-    Promise.all(layoutMetaPromises),
-    Promise.all(layoutMods.map((mod) => resolveModuleViewport(mod, params).catch((err) => { console.error("[vinext] Layout generateViewport() failed:", err); return null; }))),
-    route.page ? resolveModuleMetadata(route.page, params, spObj, pageParentPromise) : Promise.resolve(null),
-    route.page ? resolveModuleViewport(route.page, params) : Promise.resolve(null),
-  ]);
-
-  const metadataList = [...layoutMetaResults.filter(Boolean), ...(pageMeta ? [pageMeta] : [])];
-  const viewportList = [...layoutVpResults.filter(Boolean), ...(pageVp ? [pageVp] : [])];
-  const resolvedMetadata = metadataList.length > 0 ? mergeMetadata(metadataList) : null;
-  const resolvedViewport = mergeViewport(viewportList);
+  const __headResult = await __resolveAppPageHead({
+    layoutModules: route.layouts,
+    layoutTreePositions: route.layoutTreePositions,
+    pageModule: route.page,
+    params,
+    routeSegments: route.routeSegments,
+    searchParams,
+  });
+  const spObj = __headResult.searchParamsObject;
+  const hasSearchParams = __headResult.hasSearchParams;
+  const resolvedMetadata = __headResult.metadata;
+  const resolvedViewport = __headResult.viewport;
 
   // Build the route tree from the leaf page, then delegate the boundary/layout/
   // template/segment wiring to a typed runtime helper so the generated entry
@@ -9421,7 +9217,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
   // Note: CSS is automatically injected by @vitejs/plugin-rsc's
   // rscCssTransform — no manual loadCss() call needed.
   const _hasLoadingBoundary = !!(route.loading && route.loading.default);
-  const _asyncLayoutParams = makeThenableParams(params);
+  const _asyncRouteParams = makeThenableParams(params);
   return __renderAppPageLifecycle({
     cleanPathname,
     clearRequestContext() {
@@ -9464,22 +9260,21 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
     probeLayoutAt(li) {
       const LayoutComp = route.layouts[li]?.default;
       if (!LayoutComp) return null;
-      return LayoutComp({ params: _asyncLayoutParams, children: null });
+      return LayoutComp({
+        params: makeThenableParams(__resolveAppPageSegmentParams(
+          route.routeSegments,
+          route.layoutTreePositions?.[li] ?? 0,
+          params,
+        )),
+        children: null,
+      });
     },
     probePage() {
       if (!PageComponent) return null;
-      const _probeSearchObj = {};
-      url.searchParams.forEach(function(v, k) {
-        if (k in _probeSearchObj) {
-          _probeSearchObj[k] = Array.isArray(_probeSearchObj[k])
-            ? _probeSearchObj[k].concat(v)
-            : [_probeSearchObj[k], v];
-        } else {
-          _probeSearchObj[k] = v;
-        }
-      });
-      const _asyncSearchParams = makeThenableParams(_probeSearchObj);
-      return PageComponent({ params: _asyncLayoutParams, searchParams: _asyncSearchParams });
+      const _asyncSearchParams = makeThenableParams(
+        __collectAppPageSearchParams(url.searchParams).searchParamsObject,
+      );
+      return PageComponent({ params: _asyncRouteParams, searchParams: _asyncSearchParams });
     },
     classification: {
       getLayoutId(index) {
@@ -9514,19 +9309,16 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
         },
         middlewareContext: _mwCtx,
         renderFallbackPage(statusCode) {
-          // Find the not-found component from the parent level (the boundary that
-          // would catch this in Next.js). Walk up from the throwing layout to find
-          // the nearest not-found at a parent layout's directory.
-          let parentNotFound = null;
-          if (route.notFounds) {
-            for (let pi = li - 1; pi >= 0; pi--) {
-              if (route.notFounds[pi]?.default) {
-                parentNotFound = route.notFounds[pi].default;
-                break;
-              }
-            }
-          }
-          if (!parentNotFound) parentNotFound = null;
+          const parentBoundary = __resolveAppPageParentHttpAccessBoundaryModule({
+            layoutIndex: li,
+            rootForbiddenModule: null,
+            rootNotFoundModule: null,
+            rootUnauthorizedModule: null,
+            routeForbiddenModules: route.forbiddens,
+            routeNotFoundModules: route.notFounds,
+            routeUnauthorizedModules: route.unauthorizeds,
+            statusCode,
+          })?.default ?? null;
           const parentLayouts = route.layouts.slice(0, li);
           return renderHTTPAccessFallbackPage(
             route,
@@ -9534,7 +9326,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
             isRscRequest,
             request,
             {
-              boundaryComponent: parentNotFound,
+              boundaryComponent: parentBoundary,
               layouts: parentLayouts,
               matchedParams: params,
             },
@@ -9642,7 +9434,6 @@ import { createElement } from "react";
 import { setNavigationContext as _setNavigationContextOrig, getNavigationContext as _getNavigationContext } from "next/navigation";
 import { setHeadersContext, headersContextFromRequest, getDraftModeCookieHeader, getAndClearPendingCookies, consumeDynamicUsage, markDynamicUsage, applyMiddlewareRequestHeaders, getHeadersContext, setHeadersAccessPhase } from "next/headers";
 import { NextRequest, NextFetchEvent } from "next/server";
-import { mergeMetadata, resolveModuleMetadata, mergeViewport, resolveModuleViewport } from "vinext/metadata";
 
 
 import { sitemapToXml, robotsToText, manifestToJson } from "<ROOT>/packages/vinext/src/server/metadata-routes.js";
@@ -9674,6 +9465,9 @@ import {
   resolveAppPageSpecialError as __resolveAppPageSpecialError,
   teeAppPageRscStreamForCapture as __teeAppPageRscStreamForCapture,
 } from "<ROOT>/packages/vinext/src/server/app-page-execution.js";
+import {
+  resolveAppPageParentHttpAccessBoundaryModule as __resolveAppPageParentHttpAccessBoundaryModule,
+} from "<ROOT>/packages/vinext/src/server/app-page-boundary.js";
 import {
   renderAppPageErrorBoundary as __renderAppPageErrorBoundary,
   renderAppPageHttpAccessFallback as __renderAppPageHttpAccessFallback,
@@ -9687,6 +9481,13 @@ import {
   createAppPageTreePath as __createAppPageTreePath,
   resolveAppPageChildSegments as __resolveAppPageChildSegments,
 } from "<ROOT>/packages/vinext/src/server/app-page-route-wiring.js";
+import {
+  resolveAppPageSegmentParams as __resolveAppPageSegmentParams,
+} from "<ROOT>/packages/vinext/src/server/app-page-params.js";
+import {
+  collectAppPageSearchParams as __collectAppPageSearchParams,
+  resolveAppPageHead as __resolveAppPageHead,
+} from "<ROOT>/packages/vinext/src/server/app-page-head.js";
 import {
   renderAppPageLifecycle as __renderAppPageLifecycle,
 } from "<ROOT>/packages/vinext/src/server/app-page-render.js";
@@ -10061,7 +9862,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(1), // evaluated once at module load
@@ -10086,7 +9889,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(2), // evaluated once at module load
@@ -10111,7 +9916,9 @@ const routes = [
     notFound: null,
     notFounds: [null, null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(3), // evaluated once at module load
@@ -10136,7 +9943,9 @@ const routes = [
     notFound: mod_10,
     notFounds: [null, mod_10],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   }
 ];
 const _routeTrie = _buildRouteTrie(routes);
@@ -10381,83 +10190,18 @@ async function buildPageElements(route, params, routePath, pageRequest) {
     };
   }
 
-  // Resolve metadata and viewport from layouts and page.
-  //
-  // generateMetadata() accepts a "parent" (Promise of ResolvedMetadata) as its
-  // second argument (Next.js 13+). The parent resolves to the accumulated
-  // merged metadata of all ancestor segments, enabling patterns like:
-  //
-  //   const previousImages = (await parent).openGraph?.images ?? []
-  //   return { openGraph: { images: ['/new-image.jpg', ...previousImages] } }
-  //
-  // Next.js uses an eager-execution-with-serial-resolution approach:
-  // all generateMetadata() calls are kicked off concurrently, but each
-  // segment's "parent" promise resolves only after the preceding segment's
-  // metadata is resolved and merged. This preserves concurrency for I/O-bound
-  // work while guaranteeing that parent data is available when needed.
-  //
-  // We build a chain: layoutParentPromises[0] = Promise.resolve({}) (no parent
-  // for root layout), layoutParentPromises[i+1] resolves to merge(layouts[0..i]),
-  // and pageParentPromise resolves to merge(all layouts).
-  //
-  // IMPORTANT: Layout metadata errors are swallowed (.catch(() => null)) because
-  // a layout's generateMetadata() failing should not crash the page.
-  // Page metadata errors are NOT swallowed — if the page's generateMetadata()
-  // throws, the error propagates out of buildPageElement() so the caller can
-  // route it to the nearest error.tsx boundary (or global-error.tsx).
-  const layoutMods = route.layouts.filter(Boolean);
-
-  // Convert URLSearchParams → plain object for page generateMetadata() and
-  // pageProps.searchParams. Built before the layout loop so the page metadata
-  // call (below) and pageProps can reference the same object.
-  // NOTE: Layouts do NOT receive searchParams in generateMetadata() — only
-  // pages do. This matches Next.js behavior (resolve-metadata.ts:777).
-  const spObj = Object.create(null);
-  let hasSearchParams = false;
-  if (searchParams && searchParams.forEach) {
-    searchParams.forEach(function(v, k) {
-      hasSearchParams = true;
-      if (k in spObj) {
-        spObj[k] = Array.isArray(spObj[k]) ? spObj[k].concat(v) : [spObj[k], v];
-      } else {
-        spObj[k] = v;
-      }
-    });
-  }
-
-  // Build the parent promise chain and kick off metadata resolution in one pass.
-  // Each layout module is called exactly once. layoutMetaPromises[i] is the
-  // promise for layout[i]'s own metadata result.
-  //
-  // All calls are kicked off immediately (concurrent I/O), but each layout's
-  // "parent" promise only resolves after the preceding layout's metadata is done.
-  const layoutMetaPromises = [];
-  let accumulatedMetaPromise = Promise.resolve({});
-  for (let i = 0; i < layoutMods.length; i++) {
-    const parentForThisLayout = accumulatedMetaPromise;
-    // Kick off this layout's metadata resolution now (concurrent with others).
-    const metaPromise = resolveModuleMetadata(layoutMods[i], params, undefined, parentForThisLayout)
-      .catch((err) => { console.error("[vinext] Layout generateMetadata() failed:", err); return null; });
-    layoutMetaPromises.push(metaPromise);
-    // Advance accumulator: resolves to merged(layouts[0..i]) once layout[i] is done.
-    accumulatedMetaPromise = metaPromise.then(async (result) =>
-      result ? mergeMetadata([await parentForThisLayout, result]) : await parentForThisLayout
-    );
-  }
-  // Page's parent is the fully-accumulated layout metadata.
-  const pageParentPromise = accumulatedMetaPromise;
-
-  const [layoutMetaResults, layoutVpResults, pageMeta, pageVp] = await Promise.all([
-    Promise.all(layoutMetaPromises),
-    Promise.all(layoutMods.map((mod) => resolveModuleViewport(mod, params).catch((err) => { console.error("[vinext] Layout generateViewport() failed:", err); return null; }))),
-    route.page ? resolveModuleMetadata(route.page, params, spObj, pageParentPromise) : Promise.resolve(null),
-    route.page ? resolveModuleViewport(route.page, params) : Promise.resolve(null),
-  ]);
-
-  const metadataList = [...layoutMetaResults.filter(Boolean), ...(pageMeta ? [pageMeta] : [])];
-  const viewportList = [...layoutVpResults.filter(Boolean), ...(pageVp ? [pageVp] : [])];
-  const resolvedMetadata = metadataList.length > 0 ? mergeMetadata(metadataList) : null;
-  const resolvedViewport = mergeViewport(viewportList);
+  const __headResult = await __resolveAppPageHead({
+    layoutModules: route.layouts,
+    layoutTreePositions: route.layoutTreePositions,
+    pageModule: route.page,
+    params,
+    routeSegments: route.routeSegments,
+    searchParams,
+  });
+  const spObj = __headResult.searchParamsObject;
+  const hasSearchParams = __headResult.hasSearchParams;
+  const resolvedMetadata = __headResult.metadata;
+  const resolvedViewport = __headResult.viewport;
 
   // Build the route tree from the leaf page, then delegate the boundary/layout/
   // template/segment wiring to a typed runtime helper so the generated entry
@@ -11817,7 +11561,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
   // Note: CSS is automatically injected by @vitejs/plugin-rsc's
   // rscCssTransform — no manual loadCss() call needed.
   const _hasLoadingBoundary = !!(route.loading && route.loading.default);
-  const _asyncLayoutParams = makeThenableParams(params);
+  const _asyncRouteParams = makeThenableParams(params);
   return __renderAppPageLifecycle({
     cleanPathname,
     clearRequestContext() {
@@ -11860,22 +11604,21 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
     probeLayoutAt(li) {
       const LayoutComp = route.layouts[li]?.default;
       if (!LayoutComp) return null;
-      return LayoutComp({ params: _asyncLayoutParams, children: null });
+      return LayoutComp({
+        params: makeThenableParams(__resolveAppPageSegmentParams(
+          route.routeSegments,
+          route.layoutTreePositions?.[li] ?? 0,
+          params,
+        )),
+        children: null,
+      });
     },
     probePage() {
       if (!PageComponent) return null;
-      const _probeSearchObj = {};
-      url.searchParams.forEach(function(v, k) {
-        if (k in _probeSearchObj) {
-          _probeSearchObj[k] = Array.isArray(_probeSearchObj[k])
-            ? _probeSearchObj[k].concat(v)
-            : [_probeSearchObj[k], v];
-        } else {
-          _probeSearchObj[k] = v;
-        }
-      });
-      const _asyncSearchParams = makeThenableParams(_probeSearchObj);
-      return PageComponent({ params: _asyncLayoutParams, searchParams: _asyncSearchParams });
+      const _asyncSearchParams = makeThenableParams(
+        __collectAppPageSearchParams(url.searchParams).searchParamsObject,
+      );
+      return PageComponent({ params: _asyncRouteParams, searchParams: _asyncSearchParams });
     },
     classification: {
       getLayoutId(index) {
@@ -11910,19 +11653,16 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
         },
         middlewareContext: _mwCtx,
         renderFallbackPage(statusCode) {
-          // Find the not-found component from the parent level (the boundary that
-          // would catch this in Next.js). Walk up from the throwing layout to find
-          // the nearest not-found at a parent layout's directory.
-          let parentNotFound = null;
-          if (route.notFounds) {
-            for (let pi = li - 1; pi >= 0; pi--) {
-              if (route.notFounds[pi]?.default) {
-                parentNotFound = route.notFounds[pi].default;
-                break;
-              }
-            }
-          }
-          if (!parentNotFound) parentNotFound = null;
+          const parentBoundary = __resolveAppPageParentHttpAccessBoundaryModule({
+            layoutIndex: li,
+            rootForbiddenModule: null,
+            rootNotFoundModule: null,
+            rootUnauthorizedModule: null,
+            routeForbiddenModules: route.forbiddens,
+            routeNotFoundModules: route.notFounds,
+            routeUnauthorizedModules: route.unauthorizeds,
+            statusCode,
+          })?.default ?? null;
           const parentLayouts = route.layouts.slice(0, li);
           return renderHTTPAccessFallbackPage(
             route,
@@ -11930,7 +11670,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
             isRscRequest,
             request,
             {
-              boundaryComponent: parentNotFound,
+              boundaryComponent: parentBoundary,
               layouts: parentLayouts,
               matchedParams: params,
             },
@@ -12038,7 +11778,6 @@ import { createElement } from "react";
 import { setNavigationContext as _setNavigationContextOrig, getNavigationContext as _getNavigationContext } from "next/navigation";
 import { setHeadersContext, headersContextFromRequest, getDraftModeCookieHeader, getAndClearPendingCookies, consumeDynamicUsage, markDynamicUsage, applyMiddlewareRequestHeaders, getHeadersContext, setHeadersAccessPhase } from "next/headers";
 import { NextRequest, NextFetchEvent } from "next/server";
-import { mergeMetadata, resolveModuleMetadata, mergeViewport, resolveModuleViewport } from "vinext/metadata";
 import * as middlewareModule from "/tmp/test/middleware.ts";
 
 
@@ -12070,6 +11809,9 @@ import {
   resolveAppPageSpecialError as __resolveAppPageSpecialError,
   teeAppPageRscStreamForCapture as __teeAppPageRscStreamForCapture,
 } from "<ROOT>/packages/vinext/src/server/app-page-execution.js";
+import {
+  resolveAppPageParentHttpAccessBoundaryModule as __resolveAppPageParentHttpAccessBoundaryModule,
+} from "<ROOT>/packages/vinext/src/server/app-page-boundary.js";
 import {
   renderAppPageErrorBoundary as __renderAppPageErrorBoundary,
   renderAppPageHttpAccessFallback as __renderAppPageHttpAccessFallback,
@@ -12083,6 +11825,13 @@ import {
   createAppPageTreePath as __createAppPageTreePath,
   resolveAppPageChildSegments as __resolveAppPageChildSegments,
 } from "<ROOT>/packages/vinext/src/server/app-page-route-wiring.js";
+import {
+  resolveAppPageSegmentParams as __resolveAppPageSegmentParams,
+} from "<ROOT>/packages/vinext/src/server/app-page-params.js";
+import {
+  collectAppPageSearchParams as __collectAppPageSearchParams,
+  resolveAppPageHead as __resolveAppPageHead,
+} from "<ROOT>/packages/vinext/src/server/app-page-head.js";
 import {
   renderAppPageLifecycle as __renderAppPageLifecycle,
 } from "<ROOT>/packages/vinext/src/server/app-page-render.js";
@@ -12456,7 +12205,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(1), // evaluated once at module load
@@ -12481,7 +12232,9 @@ const routes = [
     notFound: null,
     notFounds: [null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(2), // evaluated once at module load
@@ -12506,7 +12259,9 @@ const routes = [
     notFound: null,
     notFounds: [null, null],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   },
   {
     __buildTimeClassifications: __VINEXT_CLASS(3), // evaluated once at module load
@@ -12531,7 +12286,9 @@ const routes = [
     notFound: mod_10,
     notFounds: [null, mod_10],
     forbidden: null,
+    forbiddens: [],
     unauthorized: null,
+    unauthorizeds: [],
   }
 ];
 const _routeTrie = _buildRouteTrie(routes);
@@ -12770,83 +12527,18 @@ async function buildPageElements(route, params, routePath, pageRequest) {
     };
   }
 
-  // Resolve metadata and viewport from layouts and page.
-  //
-  // generateMetadata() accepts a "parent" (Promise of ResolvedMetadata) as its
-  // second argument (Next.js 13+). The parent resolves to the accumulated
-  // merged metadata of all ancestor segments, enabling patterns like:
-  //
-  //   const previousImages = (await parent).openGraph?.images ?? []
-  //   return { openGraph: { images: ['/new-image.jpg', ...previousImages] } }
-  //
-  // Next.js uses an eager-execution-with-serial-resolution approach:
-  // all generateMetadata() calls are kicked off concurrently, but each
-  // segment's "parent" promise resolves only after the preceding segment's
-  // metadata is resolved and merged. This preserves concurrency for I/O-bound
-  // work while guaranteeing that parent data is available when needed.
-  //
-  // We build a chain: layoutParentPromises[0] = Promise.resolve({}) (no parent
-  // for root layout), layoutParentPromises[i+1] resolves to merge(layouts[0..i]),
-  // and pageParentPromise resolves to merge(all layouts).
-  //
-  // IMPORTANT: Layout metadata errors are swallowed (.catch(() => null)) because
-  // a layout's generateMetadata() failing should not crash the page.
-  // Page metadata errors are NOT swallowed — if the page's generateMetadata()
-  // throws, the error propagates out of buildPageElement() so the caller can
-  // route it to the nearest error.tsx boundary (or global-error.tsx).
-  const layoutMods = route.layouts.filter(Boolean);
-
-  // Convert URLSearchParams → plain object for page generateMetadata() and
-  // pageProps.searchParams. Built before the layout loop so the page metadata
-  // call (below) and pageProps can reference the same object.
-  // NOTE: Layouts do NOT receive searchParams in generateMetadata() — only
-  // pages do. This matches Next.js behavior (resolve-metadata.ts:777).
-  const spObj = Object.create(null);
-  let hasSearchParams = false;
-  if (searchParams && searchParams.forEach) {
-    searchParams.forEach(function(v, k) {
-      hasSearchParams = true;
-      if (k in spObj) {
-        spObj[k] = Array.isArray(spObj[k]) ? spObj[k].concat(v) : [spObj[k], v];
-      } else {
-        spObj[k] = v;
-      }
-    });
-  }
-
-  // Build the parent promise chain and kick off metadata resolution in one pass.
-  // Each layout module is called exactly once. layoutMetaPromises[i] is the
-  // promise for layout[i]'s own metadata result.
-  //
-  // All calls are kicked off immediately (concurrent I/O), but each layout's
-  // "parent" promise only resolves after the preceding layout's metadata is done.
-  const layoutMetaPromises = [];
-  let accumulatedMetaPromise = Promise.resolve({});
-  for (let i = 0; i < layoutMods.length; i++) {
-    const parentForThisLayout = accumulatedMetaPromise;
-    // Kick off this layout's metadata resolution now (concurrent with others).
-    const metaPromise = resolveModuleMetadata(layoutMods[i], params, undefined, parentForThisLayout)
-      .catch((err) => { console.error("[vinext] Layout generateMetadata() failed:", err); return null; });
-    layoutMetaPromises.push(metaPromise);
-    // Advance accumulator: resolves to merged(layouts[0..i]) once layout[i] is done.
-    accumulatedMetaPromise = metaPromise.then(async (result) =>
-      result ? mergeMetadata([await parentForThisLayout, result]) : await parentForThisLayout
-    );
-  }
-  // Page's parent is the fully-accumulated layout metadata.
-  const pageParentPromise = accumulatedMetaPromise;
-
-  const [layoutMetaResults, layoutVpResults, pageMeta, pageVp] = await Promise.all([
-    Promise.all(layoutMetaPromises),
-    Promise.all(layoutMods.map((mod) => resolveModuleViewport(mod, params).catch((err) => { console.error("[vinext] Layout generateViewport() failed:", err); return null; }))),
-    route.page ? resolveModuleMetadata(route.page, params, spObj, pageParentPromise) : Promise.resolve(null),
-    route.page ? resolveModuleViewport(route.page, params) : Promise.resolve(null),
-  ]);
-
-  const metadataList = [...layoutMetaResults.filter(Boolean), ...(pageMeta ? [pageMeta] : [])];
-  const viewportList = [...layoutVpResults.filter(Boolean), ...(pageVp ? [pageVp] : [])];
-  const resolvedMetadata = metadataList.length > 0 ? mergeMetadata(metadataList) : null;
-  const resolvedViewport = mergeViewport(viewportList);
+  const __headResult = await __resolveAppPageHead({
+    layoutModules: route.layouts,
+    layoutTreePositions: route.layoutTreePositions,
+    pageModule: route.page,
+    params,
+    routeSegments: route.routeSegments,
+    searchParams,
+  });
+  const spObj = __headResult.searchParamsObject;
+  const hasSearchParams = __headResult.hasSearchParams;
+  const resolvedMetadata = __headResult.metadata;
+  const resolvedViewport = __headResult.viewport;
 
   // Build the route tree from the leaf page, then delegate the boundary/layout/
   // template/segment wiring to a typed runtime helper so the generated entry
@@ -14573,7 +14265,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
   // Note: CSS is automatically injected by @vitejs/plugin-rsc's
   // rscCssTransform — no manual loadCss() call needed.
   const _hasLoadingBoundary = !!(route.loading && route.loading.default);
-  const _asyncLayoutParams = makeThenableParams(params);
+  const _asyncRouteParams = makeThenableParams(params);
   return __renderAppPageLifecycle({
     cleanPathname,
     clearRequestContext() {
@@ -14616,22 +14308,21 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
     probeLayoutAt(li) {
       const LayoutComp = route.layouts[li]?.default;
       if (!LayoutComp) return null;
-      return LayoutComp({ params: _asyncLayoutParams, children: null });
+      return LayoutComp({
+        params: makeThenableParams(__resolveAppPageSegmentParams(
+          route.routeSegments,
+          route.layoutTreePositions?.[li] ?? 0,
+          params,
+        )),
+        children: null,
+      });
     },
     probePage() {
       if (!PageComponent) return null;
-      const _probeSearchObj = {};
-      url.searchParams.forEach(function(v, k) {
-        if (k in _probeSearchObj) {
-          _probeSearchObj[k] = Array.isArray(_probeSearchObj[k])
-            ? _probeSearchObj[k].concat(v)
-            : [_probeSearchObj[k], v];
-        } else {
-          _probeSearchObj[k] = v;
-        }
-      });
-      const _asyncSearchParams = makeThenableParams(_probeSearchObj);
-      return PageComponent({ params: _asyncLayoutParams, searchParams: _asyncSearchParams });
+      const _asyncSearchParams = makeThenableParams(
+        __collectAppPageSearchParams(url.searchParams).searchParamsObject,
+      );
+      return PageComponent({ params: _asyncRouteParams, searchParams: _asyncSearchParams });
     },
     classification: {
       getLayoutId(index) {
@@ -14666,19 +14357,16 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
         },
         middlewareContext: _mwCtx,
         renderFallbackPage(statusCode) {
-          // Find the not-found component from the parent level (the boundary that
-          // would catch this in Next.js). Walk up from the throwing layout to find
-          // the nearest not-found at a parent layout's directory.
-          let parentNotFound = null;
-          if (route.notFounds) {
-            for (let pi = li - 1; pi >= 0; pi--) {
-              if (route.notFounds[pi]?.default) {
-                parentNotFound = route.notFounds[pi].default;
-                break;
-              }
-            }
-          }
-          if (!parentNotFound) parentNotFound = null;
+          const parentBoundary = __resolveAppPageParentHttpAccessBoundaryModule({
+            layoutIndex: li,
+            rootForbiddenModule: null,
+            rootNotFoundModule: null,
+            rootUnauthorizedModule: null,
+            routeForbiddenModules: route.forbiddens,
+            routeNotFoundModules: route.notFounds,
+            routeUnauthorizedModules: route.unauthorizeds,
+            statusCode,
+          })?.default ?? null;
           const parentLayouts = route.layouts.slice(0, li);
           return renderHTTPAccessFallbackPage(
             route,
@@ -14686,7 +14374,7 @@ async function _handleRequest(request, __reqCtx, _mwCtx) {
             isRscRequest,
             request,
             {
-              boundaryComponent: parentNotFound,
+              boundaryComponent: parentBoundary,
               layouts: parentLayouts,
               matchedParams: params,
             },
diff --git a/tests/app-page-boundary.test.ts b/tests/app-page-boundary.test.ts
index b9b3d37fa..3f6e13929 100644
--- a/tests/app-page-boundary.test.ts
+++ b/tests/app-page-boundary.test.ts
@@ -3,6 +3,7 @@ import {
   renderAppPageBoundaryResponse,
   resolveAppPageErrorBoundary,
   resolveAppPageHttpAccessBoundaryComponent,
+  resolveAppPageParentHttpAccessBoundaryModule,
   wrapAppPageBoundaryElement,
 } from "../packages/vinext/src/server/app-page-boundary.js";
 
@@ -52,6 +53,28 @@ describe("app page boundary helpers", () => {
     expect(component).toBe("RootNotFound");
   });
 
+  it("selects the matching parent HTTP access boundary for layout throws", () => {
+    expect(
+      resolveAppPageParentHttpAccessBoundaryModule({
+        layoutIndex: 2,
+        rootForbiddenModule: "RootForbidden",
+        routeForbiddenModules: [null, "ParentForbidden", "ThrowingLayoutForbidden"],
+        routeNotFoundModules: [null, "ParentNotFound"],
+        statusCode: 403,
+      }),
+    ).toBe("ParentForbidden");
+
+    expect(
+      resolveAppPageParentHttpAccessBoundaryModule({
+        layoutIndex: 2,
+        rootUnauthorizedModule: "RootUnauthorized",
+        routeNotFoundModules: [null, "ParentNotFound"],
+        routeUnauthorizedModules: [null, undefined, "ThrowingLayoutUnauthorized"],
+        statusCode: 401,
+      }),
+    ).toBe("RootUnauthorized");
+  });
+
   it("resolves page, layout, and global error boundaries in order", () => {
     expect(
       resolveAppPageErrorBoundary({
@@ -123,11 +146,11 @@ describe("app page boundary helpers", () => {
         const slug = Array.isArray(params.slug) ? params.slug.join("/") : params.slug;
         return `${routeSegments[treePosition] ?? "root"}:${slug}`;
       },
-      routeSegments: ["root", "[slug]"],
+      routeSegments: ["[slug]"],
     });
 
     expect(wrapped).toBe(
-      'ErrorBoundary(GlobalError)[Segment(root:post)[Layout(RootLayout)[Segment([slug]:post)[Layout(LeafLayout)[Boundary|{"slug":"post","thenable":true}]]|{"slug":"post","thenable":true}]]]',
+      'ErrorBoundary(GlobalError)[Segment([slug]:post)[Layout(RootLayout)[Segment(root:post)[Layout(LeafLayout)[Boundary|{"slug":"post","thenable":true}]]|{"thenable":true}]]]',
     );
   });
 
diff --git a/tests/app-page-head.test.ts b/tests/app-page-head.test.ts
new file mode 100644
index 000000000..e14b1f11e
--- /dev/null
+++ b/tests/app-page-head.test.ts
@@ -0,0 +1,76 @@
+import { describe, expect, it } from "vite-plus/test";
+import {
+  collectAppPageSearchParams,
+  resolveAppPageHead,
+} from "../packages/vinext/src/server/app-page-head.js";
+import type { AppPageParams } from "../packages/vinext/src/server/app-page-boundary.js";
+
+describe("app page head helpers", () => {
+  it("collects repeated search params into a null-prototype object", () => {
+    const { hasSearchParams, searchParamsObject } = collectAppPageSearchParams(
+      new URLSearchParams("__proto__=safe&tag=a&tag=b"),
+    );
+
+    expect(hasSearchParams).toBe(true);
+    expect(Object.getPrototypeOf(searchParamsObject)).toBe(null);
+    expect(searchParamsObject["__proto__"]).toBe("safe");
+    expect(searchParamsObject.tag).toEqual(["a", "b"]);
+  });
+
+  it("passes scoped params to layout metadata and full params/searchParams to page metadata", async () => {
+    // Ported from Next.js: test/e2e/app-dir/layout-params/layout-params.test.ts
+    // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/layout-params/layout-params.test.ts
+    // Reference: packages/next/src/lib/metadata/resolve-metadata.ts
+    // https://github.com/vercel/next.js/blob/canary/packages/next/src/lib/metadata/resolve-metadata.ts
+    const layoutParamCalls: AppPageParams[] = [];
+    let pageParams: AppPageParams | null = null;
+    let pageSearchParams: Record<string, string | string[]> = {};
+
+    const rootLayout = {
+      async generateMetadata({ params }: { params: Promise<AppPageParams> }) {
+        layoutParamCalls.push(await params);
+        return { title: "root" };
+      },
+    };
+    const categoryLayout = {
+      async generateMetadata({ params }: { params: Promise<AppPageParams> }) {
+        layoutParamCalls.push(await params);
+        return { description: "category" };
+      },
+    };
+    const page = {
+      async generateMetadata({
+        params,
+        searchParams,
+      }: {
+        params: Promise<AppPageParams>;
+        searchParams: Promise<Record<string, string | string[]>>;
+      }) {
+        pageParams = await params;
+        pageSearchParams = await searchParams;
+        return { keywords: ["page"] };
+      },
+    };
+
+    const result = await resolveAppPageHead<Record<string, unknown>>({
+      layoutModules: [rootLayout, categoryLayout],
+      layoutTreePositions: [1, 2],
+      pageModule: page,
+      params: { category: "books", id: "dune" },
+      routeSegments: ["shop", "[category]", "[id]"],
+      searchParams: new URLSearchParams("tag=a&tag=b&q=hello"),
+    });
+
+    expect(layoutParamCalls).toEqual([{}, { category: "books" }]);
+    expect(pageParams).toEqual({ category: "books", id: "dune" });
+    expect({ ...pageSearchParams }).toEqual({
+      q: "hello",
+      tag: ["a", "b"],
+    });
+    expect(result.hasSearchParams).toBe(true);
+    expect(result.metadata).toMatchObject({
+      description: "category",
+      keywords: ["page"],
+    });
+  });
+});
diff --git a/tests/app-page-params.test.ts b/tests/app-page-params.test.ts
new file mode 100644
index 000000000..be550bd7c
--- /dev/null
+++ b/tests/app-page-params.test.ts
@@ -0,0 +1,47 @@
+import { describe, expect, it } from "vite-plus/test";
+import { resolveAppPageSegmentParams } from "../packages/vinext/src/server/app-page-params.js";
+
+describe("app page params helpers", () => {
+  it("passes only params that apply to each layout", () => {
+    // Ported from Next.js: test/e2e/app-dir/layout-params/layout-params.test.ts
+    // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/layout-params/layout-params.test.ts
+    const routeSegments = ["base", "[param1]", "[param2]"];
+    const matchedParams = { param1: "something", param2: "another" };
+
+    expect(resolveAppPageSegmentParams(routeSegments, 0, matchedParams)).toEqual({});
+    expect(resolveAppPageSegmentParams(routeSegments, 1, matchedParams)).toEqual({});
+    expect(resolveAppPageSegmentParams(routeSegments, 2, matchedParams)).toEqual({
+      param1: "something",
+    });
+    expect(resolveAppPageSegmentParams(routeSegments, 3, matchedParams)).toEqual({
+      param1: "something",
+      param2: "another",
+    });
+  });
+
+  it("scopes catch-all params to the catch-all layout", () => {
+    // Ported from Next.js: test/e2e/app-dir/layout-params/layout-params.test.ts
+    // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/layout-params/layout-params.test.ts
+    const routeSegments = ["catchall", "[...params]"];
+    const matchedParams = { params: ["something", "another"] };
+
+    expect(resolveAppPageSegmentParams(routeSegments, 1, matchedParams)).toEqual({});
+    expect(resolveAppPageSegmentParams(routeSegments, 2, matchedParams)).toEqual({
+      params: ["something", "another"],
+    });
+  });
+
+  it("omits empty optional catch-all params from layouts", () => {
+    // Ported from Next.js: test/e2e/app-dir/layout-params/layout-params.test.ts
+    // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/layout-params/layout-params.test.ts
+    const routeSegments = ["optional-catchall", "[[...params]]"];
+
+    expect(resolveAppPageSegmentParams(routeSegments, 1, { params: [] })).toEqual({});
+    expect(resolveAppPageSegmentParams(routeSegments, 2, { params: [] })).toEqual({});
+    expect(
+      resolveAppPageSegmentParams(routeSegments, 2, { params: ["something", "another"] }),
+    ).toEqual({
+      params: ["something", "another"],
+    });
+  });
+});
diff --git a/tests/app-page-route-wiring.test.ts b/tests/app-page-route-wiring.test.ts
index 8f7dde93d..1cb867aae 100644
--- a/tests/app-page-route-wiring.test.ts
+++ b/tests/app-page-route-wiring.test.ts
@@ -2,6 +2,7 @@ import { Fragment, createElement, isValidElement, type ReactNode } from "react";
 import { describe, expect, it } from "vite-plus/test";
 import { useSelectedLayoutSegments } from "../packages/vinext/src/shims/navigation.js";
 import type { AppElements } from "../packages/vinext/src/server/app-elements.js";
+import type { AppPageParams } from "../packages/vinext/src/server/app-page-boundary.js";
 import {
   type AppPageModule,
   type AppPageSlotOverride,
@@ -193,6 +194,44 @@ describe("app page route wiring helpers", () => {
     expect(entries.map((entry) => entry.treePath)).toEqual(["/", "/(marketing)"]);
   });
 
+  it("passes only segment-applicable params to each layout", () => {
+    // Ported from Next.js: test/e2e/app-dir/app/index.test.ts
+    // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/app/index.test.ts
+    const paramCalls: AppPageParams[] = [];
+
+    buildAppPageElements({
+      element: createElement(PageProbe),
+      makeThenableParams(params) {
+        paramCalls.push({ ...params });
+        return Promise.resolve(params);
+      },
+      matchedParams: { category: "books", id: "hello-world" },
+      resolvedMetadata: null,
+      resolvedViewport: {},
+      route: {
+        error: null,
+        errors: [null, null, null],
+        layoutTreePositions: [1, 2, 3],
+        layouts: [{ default: RootLayout }, { default: GroupLayout }, { default: GroupLayout }],
+        loading: null,
+        notFound: null,
+        notFounds: [null, null, null],
+        routeSegments: ["dynamic", "[category]", "[id]"],
+        slots: null,
+        templateTreePositions: [],
+        templates: [],
+      },
+      routePath: "/dynamic/books/hello-world",
+      rootNotFoundModule: null,
+    });
+
+    expect(paramCalls).toEqual([
+      {},
+      { category: "books" },
+      { category: "books", id: "hello-world" },
+    ]);
+  });
+
   it("builds a flat elements map with route, layout, template, page, and slot entries", async () => {
     const elements = buildAppPageElements({
       element: createElement(PageProbe),
diff --git a/tests/app-router.test.ts b/tests/app-router.test.ts
index 489db4850..932268811 100644
--- a/tests/app-router.test.ts
+++ b/tests/app-router.test.ts
@@ -761,6 +761,26 @@ describe("App Router integration", () => {
     expect(html).toContain('content="noindex"');
   });
 
+  it("forbidden() thrown from a layout uses the forbidden boundary", async () => {
+    // Ported from Next.js: test/e2e/app-dir/forbidden/basic/forbidden-basic.test.ts
+    // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/forbidden/basic/forbidden-basic.test.ts
+    const res = await fetch(`${baseUrl}/nextjs-compat/layout-forbidden-boundary`);
+    expect(res.status).toBe(403);
+    const html = await res.text();
+    expect(html).toContain("403 - Forbidden");
+    expect(html).not.toContain("404 - Page Not Found");
+  });
+
+  it("unauthorized() thrown from a layout uses the unauthorized boundary", async () => {
+    // Ported from Next.js: test/e2e/app-dir/unauthorized/basic/unauthorized-basic.test.ts
+    // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/unauthorized/basic/unauthorized-basic.test.ts
+    const res = await fetch(`${baseUrl}/nextjs-compat/layout-unauthorized-boundary`);
+    expect(res.status).toBe(401);
+    const html = await res.text();
+    expect(html).toContain("401 - Unauthorized");
+    expect(html).not.toContain("404 - Page Not Found");
+  });
+
   // ── Client hook usage without "use client" (#834) ──
   // When a Server Component imports a client-only hook from next/navigation
   // without the "use client" directive, vinext should surface a clear error
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-forbidden-boundary/layout.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-forbidden-boundary/layout.tsx
new file mode 100644
index 000000000..cff0ad3fe
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-forbidden-boundary/layout.tsx
@@ -0,0 +1,9 @@
+import { forbidden } from "next/navigation";
+
+/**
+ * Next.js compat: forbidden/basic — access fallback thrown from a layout should
+ * render the matching forbidden boundary, not the not-found boundary.
+ */
+export default function Layout() {
+  forbidden();
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-forbidden-boundary/page.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-forbidden-boundary/page.tsx
new file mode 100644
index 000000000..bdab4d08f
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-forbidden-boundary/page.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <p>forbidden layout page rendered</p>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-with-boundary/error.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-with-boundary/error.tsx
new file mode 100644
index 000000000..aaf697878
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-with-boundary/error.tsx
@@ -0,0 +1,9 @@
+/**
+ * Next.js compat: global-error/basic — local error boundary for layout metadata errors.
+ * Source: https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/global-error/basic/index.test.ts
+ */
+"use client";
+
+export default function ErrorBoundary() {
+  return <p id="error">Local layout metadata error boundary</p>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-with-boundary/layout.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-with-boundary/layout.tsx
new file mode 100644
index 000000000..47285e112
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-with-boundary/layout.tsx
@@ -0,0 +1,11 @@
+/**
+ * Next.js compat: global-error/basic — layout generateMetadata errors should
+ * propagate into the nearest error boundary instead of being swallowed.
+ */
+export function generateMetadata() {
+  throw new Error("Layout metadata error");
+}
+
+export default function Layout({ children }: { children: React.ReactNode }) {
+  return <section>{children}</section>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-with-boundary/page.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-with-boundary/page.tsx
new file mode 100644
index 000000000..fab33416b
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-with-boundary/page.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <p>layout metadata page rendered</p>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-without-boundary/layout.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-without-boundary/layout.tsx
new file mode 100644
index 000000000..0860a83d4
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-without-boundary/layout.tsx
@@ -0,0 +1,11 @@
+/**
+ * Next.js compat: global-error/basic — layout generateMetadata errors without
+ * a local error boundary should escalate to global-error.tsx.
+ */
+export function generateMetadata() {
+  throw new Error("Layout metadata error");
+}
+
+export default function Layout({ children }: { children: React.ReactNode }) {
+  return <section>{children}</section>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-without-boundary/page.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-without-boundary/page.tsx
new file mode 100644
index 000000000..fab33416b
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-metadata-error-without-boundary/page.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <p>layout metadata page rendered</p>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-unauthorized-boundary/layout.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-unauthorized-boundary/layout.tsx
new file mode 100644
index 000000000..0b6f81009
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-unauthorized-boundary/layout.tsx
@@ -0,0 +1,9 @@
+import { unauthorized } from "next/navigation";
+
+/**
+ * Next.js compat: unauthorized/basic — access fallback thrown from a layout
+ * should render the matching unauthorized boundary, not the not-found boundary.
+ */
+export default function Layout() {
+  unauthorized();
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-unauthorized-boundary/page.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-unauthorized-boundary/page.tsx
new file mode 100644
index 000000000..7242d5f67
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-unauthorized-boundary/page.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <p>unauthorized layout page rendered</p>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-with-boundary/error.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-with-boundary/error.tsx
new file mode 100644
index 000000000..dd3e80593
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-with-boundary/error.tsx
@@ -0,0 +1,10 @@
+/**
+ * Next.js compat: viewport resolution errors use the same metadata outlet
+ * boundary path as generateMetadata errors.
+ * Source: https://github.com/vercel/next.js/blob/canary/packages/next/src/lib/metadata/metadata.tsx
+ */
+"use client";
+
+export default function ErrorBoundary() {
+  return <p id="error">Local layout viewport error boundary</p>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-with-boundary/layout.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-with-boundary/layout.tsx
new file mode 100644
index 000000000..c4645df49
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-with-boundary/layout.tsx
@@ -0,0 +1,11 @@
+/**
+ * Next.js compat: layout generateViewport errors should propagate into the
+ * nearest error boundary instead of being swallowed.
+ */
+export function generateViewport() {
+  throw new Error("Layout viewport error");
+}
+
+export default function Layout({ children }: { children: React.ReactNode }) {
+  return <section>{children}</section>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-with-boundary/page.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-with-boundary/page.tsx
new file mode 100644
index 000000000..603431e9a
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-with-boundary/page.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <p>layout viewport page rendered</p>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-without-boundary/layout.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-without-boundary/layout.tsx
new file mode 100644
index 000000000..03272e021
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-without-boundary/layout.tsx
@@ -0,0 +1,11 @@
+/**
+ * Next.js compat: layout generateViewport errors without a local error
+ * boundary should escalate to global-error.tsx.
+ */
+export function generateViewport() {
+  throw new Error("Layout viewport error");
+}
+
+export default function Layout({ children }: { children: React.ReactNode }) {
+  return <section>{children}</section>;
+}
diff --git a/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-without-boundary/page.tsx b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-without-boundary/page.tsx
new file mode 100644
index 000000000..603431e9a
--- /dev/null
+++ b/tests/fixtures/app-basic/app/nextjs-compat/layout-viewport-error-without-boundary/page.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <p>layout viewport page rendered</p>;
+}
diff --git a/tests/nextjs-compat/global-error.test.ts b/tests/nextjs-compat/global-error.test.ts
index 05deaeaae..9c65e6953 100644
--- a/tests/nextjs-compat/global-error.test.ts
+++ b/tests/nextjs-compat/global-error.test.ts
@@ -9,6 +9,8 @@
  * - Global-error.tsx as the last resort for root-level errors
  * - generateMetadata() errors caught by local error.tsx when present
  * - generateMetadata() errors escalating to global-error when no local boundary
+ * - layout generateMetadata() errors following the same boundary path
+ * - layout generateViewport() errors following the same boundary path
  *
  * NOTE: Most Next.js global-error tests are browser-based (click buttons, check
  * rendered error UI after hydration/client error). This file tests SSR-level
@@ -130,6 +132,54 @@ describe("Next.js compat: global-error", () => {
     expect(html).toContain("Metadata error");
   });
 
+  it("layout generateMetadata() error caught by local error.tsx boundary", async () => {
+    // Ported from Next.js: test/e2e/app-dir/global-error/basic/index.test.ts
+    // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/global-error/basic/index.test.ts
+    const { res, html } = await fetchHtml(
+      baseUrl,
+      "/nextjs-compat/layout-metadata-error-with-boundary",
+    );
+    expect(res.status).toBe(200);
+    expect(html).toContain("Local layout metadata error boundary");
+    expect(html).not.toContain("layout metadata page rendered");
+  });
+
+  it("layout generateMetadata() error without local boundary renders global-error", async () => {
+    // Ported from Next.js: test/e2e/app-dir/global-error/basic/index.test.ts
+    // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/global-error/basic/index.test.ts
+    const { res, html } = await fetchHtml(
+      baseUrl,
+      "/nextjs-compat/layout-metadata-error-without-boundary",
+    );
+    expect(res.status).toBe(200);
+    expect(html).toContain("global-error");
+    expect(html).toContain("Layout metadata error");
+  });
+
+  it("layout generateViewport() error caught by local error.tsx boundary", async () => {
+    // Next.js resolves viewport through the same metadata outlet error path:
+    // https://github.com/vercel/next.js/blob/canary/packages/next/src/lib/metadata/metadata.tsx
+    const { res, html } = await fetchHtml(
+      baseUrl,
+      "/nextjs-compat/layout-viewport-error-with-boundary",
+    );
+    expect(res.status).toBe(200);
+    expect(html).toContain("Local layout viewport error boundary");
+    expect(html).not.toContain("layout viewport page rendered");
+  });
+
+  it("layout generateViewport() error without local boundary renders global-error", async () => {
+    // Next.js resolves viewport through the same metadata outlet error path:
+    // https://github.com/vercel/next.js/blob/canary/packages/next/src/lib/metadata/metadata.tsx
+    const { res, html } = await fetchHtml(
+      baseUrl,
+      "/nextjs-compat/layout-viewport-error-without-boundary",
+    );
+    expect(res.status).toBe(200);
+    expect(html).toContain("global-error");
+    expect(html).toContain("Layout viewport error");
+  });
+
   // ── Structural integrity: no double <html>/<body> tags ───────
   // global-error.tsx provides its own <html> and <body>. When it renders,
   // the root layout's <html>/<body> must NOT also appear.
@@ -254,4 +304,42 @@ describe("Next.js compat: global-error (production preview)", () => {
     expect(res.status).toBe(200);
     expect(html).toContain("global-error");
   });
+
+  it("layout generateMetadata() errors render the co-located error.tsx boundary with 200", async () => {
+    const { res, html } = await fetchHtml(
+      baseUrl,
+      "/nextjs-compat/layout-metadata-error-with-boundary",
+    );
+    expect(res.status).toBe(200);
+    expect(html).toContain("Local layout metadata error boundary");
+    expect(html).not.toContain("global-error");
+  });
+
+  it("layout generateMetadata() errors without a local boundary escalate to global-error with 200", async () => {
+    const { res, html } = await fetchHtml(
+      baseUrl,
+      "/nextjs-compat/layout-metadata-error-without-boundary",
+    );
+    expect(res.status).toBe(200);
+    expect(html).toContain("global-error");
+  });
+
+  it("layout generateViewport() errors render the co-located error.tsx boundary with 200", async () => {
+    const { res, html } = await fetchHtml(
+      baseUrl,
+      "/nextjs-compat/layout-viewport-error-with-boundary",
+    );
+    expect(res.status).toBe(200);
+    expect(html).toContain("Local layout viewport error boundary");
+    expect(html).not.toContain("global-error");
+  });
+
+  it("layout generateViewport() errors without a local boundary escalate to global-error with 200", async () => {
+    const { res, html } = await fetchHtml(
+      baseUrl,
+      "/nextjs-compat/layout-viewport-error-without-boundary",
+    );
+    expect(res.status).toBe(200);
+    expect(html).toContain("global-error");
+  });
 });