fix: suppress false "middleware not added" warning on RSC navigations

Add x-nl-active marker header on early-return middleware paths so the
Server component can distinguish "middleware not installed" from
"middleware intentionally skipped this request."

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: vklimontovich

packages/core/src/middleware.ts

@@ -2,6 +2,7 @@ import type { NextMiddleware, NextRequest } from "next/server";
 import { NextResponse, after } from "next/server";
 import {
   LAST_PAGE_RENDER_ID_COOKIE,
+  headerNames,
   serializeServerComponentContext,
 } from "./server-component-context";
 import type {
@@ -80,13 +81,17 @@ export function createNextlyticsMiddleware(
 
     // Skip internal paths, prefetch, and static files
     if (reqInfo.isNextjsInternal || reqInfo.isPrefetch || reqInfo.isStaticFile) {
-      return undefined;
+      const response = NextResponse.next();
+      response.headers.set(headerNames.active, "1");
+      return response;
     }
 
     // Skip non-page-navigation, non-API requests (e.g. RSC fetches).
     // Soft navigations are tracked via the client /api/event request.
     if (!reqInfo.isPageNavigation && !config.isApiPath(pathname)) {
-      return undefined;
+      const response = NextResponse.next();
+      response.headers.set(headerNames.active, "1");
+      return response;
     }
 
     const pageRenderId = generateId();

packages/core/src/server-component-context.ts

@@ -8,6 +8,7 @@ const headerNames = {
   search: `${HEADER_PREFIX}search`,
   pageRenderId: `${HEADER_PREFIX}page-render-id`,
   isSoftNavigation: `${HEADER_PREFIX}is-soft-nav`,
+  active: `${HEADER_PREFIX}active`,
   scripts: `${HEADER_PREFIX}scripts`,
 } as const;
 

packages/core/src/server.tsx

@@ -243,7 +243,10 @@ export function Nextlytics(userConfig: NextlyticsConfig): NextlyticsResult {
     const ctx = restoreServerComponentContext(headersList);
 
     if (!ctx) {
-      console.warn("[Nextlytics] nextlyticsMiddleware should be added in order for Server to work");
+      // x-nl-page-render-id absent → check if middleware is at least active
+      if (!headersList.get(headerNames.active)) {
+        console.warn("[Nextlytics] nextlyticsMiddleware should be added in order for Server to work");
+      }
       return <>{children}</>;
     }