fix: stop endless RSC prefetch requests in Next.js 16.3

Author: ahmadaccino

.changeset/curvy-lions-prefetch.md

@@ -0,0 +1,7 @@
+---
+"@opennextjs/cloudflare": patch
+---
+
+fix: serve cached segment prefetches when Next.js prefetch inlining is enabled
+
+Prevent Next.js 16.3 clients from repeatedly requesting the route tree when cache interception is enabled.

examples/playground16/app/prefetch/page.tsx

@@ -0,0 +1,5 @@
+import Link from "next/link";
+
+export default function PrefetchPage() {
+	return <Link href="/prefetch/target">Target</Link>;
+}

examples/playground16/app/prefetch/target/page.tsx

@@ -0,0 +1,3 @@
+export default function PrefetchTargetPage() {
+	return <p>Target page</p>;
+}

examples/playground16/e2e/prefetch.cloudflare.spec.ts

@@ -0,0 +1,43 @@
+import { expect, test } from "@playwright/test";
+
+test("cache interception serves segment prefetches without retrying indefinitely", async ({ page }) => {
+	const segmentPrefetches: string[] = [];
+	page.on("request", (request) => {
+		if (new URL(request.url()).pathname !== "/prefetch/target") {
+			return;
+		}
+
+		const segment = request.headers()["next-router-segment-prefetch"];
+		if (segment) {
+			segmentPrefetches.push(segment);
+		}
+	});
+
+	const routeTreeResponsePromise = page.waitForResponse((response) => {
+		const request = response.request();
+		return (
+			new URL(request.url()).pathname === "/prefetch/target" &&
+			request.headers()["next-router-segment-prefetch"] === "/_tree"
+		);
+	});
+
+	await page.goto("/prefetch");
+
+	const routeTreeResponse = await routeTreeResponsePromise;
+	expect(routeTreeResponse.status()).toBe(200);
+	expect(routeTreeResponse.headers()).toMatchObject({
+		"content-type": "text/x-component",
+		"x-nextjs-postponed": "2",
+		"x-nextjs-prerender": "1",
+		"x-opennext-cache": "HIT",
+	});
+
+	await expect.poll(() => segmentPrefetches.some((segment) => segment.endsWith("/__PAGE__"))).toBe(true);
+	await page.waitForLoadState("networkidle");
+
+	const settledPrefetchCount = segmentPrefetches.length;
+	await page.waitForTimeout(1_000);
+
+	expect(segmentPrefetches).toHaveLength(settledPrefetchCount);
+	expect(settledPrefetchCount).toBeLessThan(10);
+});

examples/playground16/open-next.config.ts

@@ -5,6 +5,7 @@ import d1NextTagCache from "@opennextjs/cloudflare/overrides/tag-cache/d1-next-t
 
 export default {
 	...defineCloudflareConfig({
+		enableCacheInterception: true,
 		incrementalCache: r2IncrementalCache,
 		queue: doQueue,
 		tagCache: d1NextTagCache,

examples/playground16/package.json

@@ -17,7 +17,7 @@
 		"cf-typegen": "wrangler types --env-interface CloudflareEnv"
 	},
 	"dependencies": {
-		"next": "16.2.11",
+		"next": "16.3.1",
 		"react-dom": "^19.2.6",
 		"react": "^19.2.6",
 		"shiki": "^3.22.0"

packages/cloudflare/src/cli/build/build.ts

@@ -19,6 +19,7 @@ import { compileInit } from "./open-next/compile-init.js";
 import { compileSkewProtection } from "./open-next/compile-skew-protection.js";
 import { compileDurableObjects } from "./open-next/compileDurableObjects.js";
 import { createServerBundle } from "./open-next/createServerBundle.js";
+import { patchCacheInterceptor } from "./patches/ast/cache-interceptor.js";
 import { useNodeMiddleware } from "./utils/middleware.js";
 import { getVersion } from "./utils/version.js";
 
@@ -100,6 +101,9 @@ export async function build(
 
 	// Compile middleware
 	await createMiddleware(options, { forceOnlyBuildOnce: true });
+	if (config.dangerous?.enableCacheInterception === true) {
+		patchCacheInterceptor(options);
+	}
 
 	createStaticAssets(options, { useBasePath: true });
 

packages/cloudflare/src/cli/build/patches/ast/cache-interceptor.spec.ts

@@ -0,0 +1,49 @@
+import { readFileSync } from "node:fs";
+
+import mockFs from "mock-fs";
+import { afterEach, describe, expect, test } from "vitest";
+
+import { patchCacheInterceptor, patchCacheInterceptorSource } from "./cache-interceptor.js";
+
+const cacheInterceptorSource = `
+function getBodyForAppRouter(event, cachedValue) {
+  const segmentHeader = \`\${event.headers[NEXT_SEGMENT_PREFETCH_HEADER]}\`;
+  const isSegmentResponse =
+    Boolean(segmentHeader) &&
+    segmentHeader in (cachedValue.segmentData || {}) &&
+    !NextConfig.experimental?.prefetchInlining;
+  const body = isSegmentResponse
+    ? cachedValue.segmentData[segmentHeader]
+    : cachedValue.rsc;
+  return { body };
+}
+`;
+
+describe("patchCacheInterceptor", () => {
+	afterEach(() => mockFs.restore());
+
+	test("patches the generated middleware", () => {
+		const outputDir = "/app/.open-next";
+		const middlewarePath = `${outputDir}/middleware/handler.mjs`;
+		mockFs({ [middlewarePath]: cacheInterceptorSource });
+
+		patchCacheInterceptor({ outputDir });
+
+		expect(readFileSync(middlewarePath, "utf8")).not.toContain("!NextConfig.experimental?.prefetchInlining");
+	});
+
+	test("serves cached segment data when prefetch inlining is enabled", () => {
+		const patchedSource = patchCacheInterceptorSource(cacheInterceptorSource);
+
+		expect(patchedSource).toContain(
+			"Boolean(segmentHeader) && segmentHeader in (cachedValue.segmentData || {})"
+		);
+		expect(patchedSource).not.toContain("!NextConfig.experimental?.prefetchInlining");
+	});
+
+	test("fails when the upstream cache interceptor no longer matches", () => {
+		expect(() => patchCacheInterceptorSource("const isSegmentResponse = false;")).toThrow(
+			"Failed to patch the OpenNext cache interceptor"
+		);
+	});
+});

packages/cloudflare/src/cli/build/patches/ast/cache-interceptor.ts

@@ -0,0 +1,29 @@
+import { readFileSync, writeFileSync } from "node:fs";
+import path from "node:path";
+
+import type { BuildOptions } from "@opennextjs/aws/build/helper.js";
+import { patchCode } from "@opennextjs/aws/build/patch/astCodePatcher.js";
+
+const segmentPrefetchRule = `
+rule:
+  pattern: Boolean($SEGMENT_HEADER) && $SEGMENT_HEADER in ($CACHED_VALUE.segmentData || {}) && !NextConfig.experimental?.prefetchInlining
+fix: Boolean($SEGMENT_HEADER) && $SEGMENT_HEADER in ($CACHED_VALUE.segmentData || {})
+`;
+
+export function patchCacheInterceptorSource(source: string): string {
+	const patchedSource = patchCode(source, segmentPrefetchRule);
+	if (patchedSource === source) {
+		throw new Error("Failed to patch the OpenNext cache interceptor");
+	}
+	return patchedSource;
+}
+
+/**
+ * OpenNext AWS 4.1.0 treats prefetch inlining as if it eliminates segment responses, but Next.js
+ * still requests cached route-tree and bundle segments. A full RSC response makes Next.js retry indefinitely.
+ */
+export function patchCacheInterceptor(buildOpts: Pick<BuildOptions, "outputDir">): void {
+	const middlewarePath = path.join(buildOpts.outputDir, "middleware/handler.mjs");
+	const source = readFileSync(middlewarePath, "utf8");
+	writeFileSync(middlewarePath, patchCacheInterceptorSource(source));
+}