diff --git a/src/lib/proxy-auth-contract.test.ts b/src/lib/proxy-auth-contract.test.ts
new file mode 100644
index 00000000..af07b1a7
--- /dev/null
+++ b/src/lib/proxy-auth-contract.test.ts
@@ -0,0 +1,13 @@
+import { readFileSync } from "node:fs";
+import { describe, expect, it } from "vitest";
+
+describe("proxy authentication boundary", () => {
+  it("uses a database-free Auth.js decoder", () => {
+    const proxy = readFileSync("src/proxy.ts", "utf8");
+    const proxyAuth = readFileSync("src/lib/proxy-auth.ts", "utf8");
+
+    expect(proxy).toContain('from "@/lib/proxy-auth"');
+    expect(proxy).not.toContain('from "@/lib/auth"');
+    expect(proxyAuth).not.toMatch(/from\s+["'][^"']*(prisma|site-settings|credentials)[^"']*["']/i);
+  });
+});
diff --git a/src/lib/proxy-auth.ts b/src/lib/proxy-auth.ts
new file mode 100644
index 00000000..1801f78f
--- /dev/null
+++ b/src/lib/proxy-auth.ts
@@ -0,0 +1,10 @@
+import NextAuth from "next-auth";
+
+// Proxy authentication must only decode the Auth.js session. Importing the
+// full CMS auth configuration here would also run Prisma/settings callbacks.
+export const { auth: proxyAuth } = NextAuth({
+  trustHost: true,
+  secret: process.env.AUTH_SECRET,
+  session: { strategy: "jwt" },
+  providers: [],
+});
diff --git a/src/proxy.ts b/src/proxy.ts
index 092c0477..f6dd2823 100644
--- a/src/proxy.ts
+++ b/src/proxy.ts
@@ -1,12 +1,12 @@
 import { NextResponse } from "next/server";
-import { auth } from "@/lib/auth";
+import { proxyAuth } from "@/lib/proxy-auth";
 import { shouldRedirectAdminRequest } from "@/lib/proxy-access";
 
 // Edge proxy (formerly "middleware"): Prisma can't run here, so we only forward
 // the request path (so server components / the access guard can read it via
 // headers()) and normalize the real client IP. The DB-backed banned/maintenance
 // checks happen in src/lib/access-guard.ts (Node runtime) from the root layout.
-export const proxy = auth((req) => {
+export const proxy = proxyAuth((req) => {
   if (shouldRedirectAdminRequest(req.nextUrl.pathname, req.auth?.user ?? null)) {
     return NextResponse.redirect(new URL("/login", req.url));
   }