diff --git a/apps/admin-ui/src/app/api/[...path]/route.ts b/apps/admin-ui/src/app/api/[...path]/route.ts
index 7f65d75..06c829b 100644
--- a/apps/admin-ui/src/app/api/[...path]/route.ts
+++ b/apps/admin-ui/src/app/api/[...path]/route.ts
@@ -3,6 +3,9 @@ import { NextRequest, NextResponse } from "next/server";
 export const dynamic = "force-dynamic";
 export const runtime = "nodejs";
 
+const SESSION_COOKIE = "mc_admin_session";
+const SESSION_MAX_AGE = 7 * 24 * 60 * 60;
+
 function candidateBases(): string[] {
   const configured = [
     process.env.MASTER_API_URL,
@@ -14,10 +17,50 @@ function candidateBases(): string[] {
   return [...new Set(configured.map((v) => v.replace(/\/$/, "")))];
 }
 
+function isHttps(request: NextRequest): boolean {
+  const proto = request.headers.get("x-forwarded-proto");
+  if (proto) return proto.split(",")[0].trim() === "https";
+  return request.nextUrl.protocol === "https:";
+}
+
+function applySessionCookie(
+  response: NextResponse,
+  token: string,
+  request: NextRequest,
+  expiresAt?: string
+) {
+  const secure = isHttps(request) || process.env.NODE_ENV === "production";
+  response.cookies.set({
+    name: SESSION_COOKIE,
+    value: token,
+    httpOnly: true,
+    secure,
+    sameSite: "lax",
+    path: "/",
+    maxAge: SESSION_MAX_AGE,
+    ...(expiresAt ? { expires: new Date(expiresAt) } : {}),
+  });
+}
+
+function clearSessionCookie(response: NextResponse, request: NextRequest) {
+  const secure = isHttps(request) || process.env.NODE_ENV === "production";
+  response.cookies.set({
+    name: SESSION_COOKIE,
+    value: "",
+    httpOnly: true,
+    secure,
+    sameSite: "lax",
+    path: "/",
+    maxAge: 0,
+  });
+}
+
 async function proxy(request: NextRequest, pathSegments: string[]) {
   const targetPath = pathSegments.join("/");
   const url = new URL(request.url);
   const search = url.search;
+  const isLogin = request.method === "POST" && targetPath === "v1/auth/login";
+  const isLogout = request.method === "POST" && targetPath === "v1/auth/logout";
 
   const headers = new Headers();
   const contentType = request.headers.get("content-type");
@@ -43,27 +86,71 @@ async function proxy(request: NextRequest, pathSegments: string[]) {
         redirect: "manual",
       });
 
+      // Special-case auth so the session cookie is owned by admin.vonas.nl
+      if (isLogin) {
+        const text = await upstream.text();
+        let data: {
+          user?: unknown;
+          sessionToken?: string;
+          expiresAt?: string;
+          error?: unknown;
+        } = {};
+        try {
+          data = JSON.parse(text);
+        } catch {
+          return new NextResponse(text, {
+            status: upstream.status,
+            headers: { "content-type": "application/json" },
+          });
+        }
+
+        const response = NextResponse.json(
+          { user: data.user, error: data.error },
+          { status: upstream.status }
+        );
+
+        if (upstream.ok && data.sessionToken) {
+          applySessionCookie(response, data.sessionToken, request, data.expiresAt);
+        }
+        return response;
+      }
+
+      if (isLogout) {
+        const responseBody = await upstream.arrayBuffer();
+        const response = new NextResponse(responseBody, {
+          status: upstream.status,
+          headers: {
+            "content-type":
+              upstream.headers.get("content-type") ?? "application/json",
+          },
+        });
+        clearSessionCookie(response, request);
+        return response;
+      }
+
       const responseBody = await upstream.arrayBuffer();
       const response = new NextResponse(responseBody, { status: upstream.status });
-
-      const upstreamType = upstream.headers.get("content-type");
       response.headers.set(
         "content-type",
-        upstreamType ?? "application/json"
+        upstream.headers.get("content-type") ?? "application/json"
       );
 
+      // Forward any upstream cookies as fallback (rewritten without Domain)
       const anyHeaders = upstream.headers as Headers & {
         getSetCookie?: () => string[];
       };
       const setCookies =
         typeof anyHeaders.getSetCookie === "function"
           ? anyHeaders.getSetCookie()
-          : upstream.headers.get("set-cookie")
-            ? [upstream.headers.get("set-cookie") as string]
-            : [];
+          : [];
 
-      for (const c of setCookies) {
-        response.headers.append("set-cookie", c);
+      for (const raw of setCookies) {
+        const cleaned = raw
+          .split(";")
+          .map((p) => p.trim())
+          .filter((p) => !/^domain=/i.test(p))
+          .join("; ");
+        response.headers.append("set-cookie", cleaned);
       }
 
       return response;
diff --git a/apps/admin-ui/src/app/page.tsx b/apps/admin-ui/src/app/page.tsx
index b0d6020..de6cbea 100644
--- a/apps/admin-ui/src/app/page.tsx
+++ b/apps/admin-ui/src/app/page.tsx
@@ -12,7 +12,9 @@ export default function LoginPage() {
 
   useEffect(() => {
     fetch("/api/v1/auth/me", { credentials: "include" })
-      .then((r) => r.ok && router.push("/dashboard"))
+      .then((r) => {
+        if (r.ok) router.push("/dashboard");
+      })
       .catch(() => {});
   }, [router]);
 
@@ -38,10 +40,10 @@ export default function LoginPage() {
         }
         throw new Error(message);
       }
-      router.push("/dashboard");
+      // Full navigation so the session cookie is definitely included
+      window.location.assign("/dashboard");
     } catch (err) {
       setError(err instanceof Error ? err.message : "Inloggen mislukt");
-    } finally {
       setLoading(false);
     }
   }
diff --git a/apps/master-api/src/auth/routes.ts b/apps/master-api/src/auth/routes.ts
index db724bd..bf3ac71 100644
--- a/apps/master-api/src/auth/routes.ts
+++ b/apps/master-api/src/auth/routes.ts
@@ -46,7 +46,12 @@ export async function registerAuthRoutes(
       expires: expiresAt,
     });
 
-    return { user: { id: user.id, email: user.email, name: user.name } };
+    // sessionToken also in body so Admin UI proxy can set cookie on its own domain
+    return {
+      user: { id: user.id, email: user.email, name: user.name },
+      sessionToken: token,
+      expiresAt: expiresAt.toISOString(),
+    };
   });
 
   app.post("/api/v1/auth/logout", async (request, reply) => {