diff --git a/proxy/internal/proxy/agent_network_vertex_guardrail_realstack_test.go b/proxy/internal/proxy/agent_network_vertex_guardrail_realstack_test.go
new file mode 100644
index 000000000..e03465aea
--- /dev/null
+++ b/proxy/internal/proxy/agent_network_vertex_guardrail_realstack_test.go
@@ -0,0 +1,272 @@
+package proxy_test
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"runtime"
+	"strings"
+	"sync/atomic"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/test/bufconn"
+
+	"github.com/netbirdio/netbird/management/internals/modules/agentnetwork"
+	agentNetworkTypes "github.com/netbirdio/netbird/management/internals/modules/agentnetwork/types"
+	rpservice "github.com/netbirdio/netbird/management/internals/modules/reverseproxy/service"
+	mgmtgrpc "github.com/netbirdio/netbird/management/internals/shared/grpc"
+	"github.com/netbirdio/netbird/management/server/store"
+	"github.com/netbirdio/netbird/proxy/internal/middleware"
+	"github.com/netbirdio/netbird/proxy/internal/middleware/bodytap"
+	mwbuiltin "github.com/netbirdio/netbird/proxy/internal/middleware/builtin"
+	_ "github.com/netbirdio/netbird/proxy/internal/middleware/builtin/cost_meter"
+	_ "github.com/netbirdio/netbird/proxy/internal/middleware/builtin/llm_guardrail"
+	_ "github.com/netbirdio/netbird/proxy/internal/middleware/builtin/llm_identity_inject"
+	_ "github.com/netbirdio/netbird/proxy/internal/middleware/builtin/llm_limit_check"
+	_ "github.com/netbirdio/netbird/proxy/internal/middleware/builtin/llm_limit_record"
+	_ "github.com/netbirdio/netbird/proxy/internal/middleware/builtin/llm_request_parser"
+	_ "github.com/netbirdio/netbird/proxy/internal/middleware/builtin/llm_response_parser"
+	_ "github.com/netbirdio/netbird/proxy/internal/middleware/builtin/llm_router"
+	"github.com/netbirdio/netbird/proxy/internal/proxy"
+	nbproxytypes "github.com/netbirdio/netbird/proxy/internal/types"
+	"github.com/netbirdio/netbird/shared/management/proto"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// TestReverseProxy_VertexGuardrail_ModelAllowlist drives Anthropic-on-Vertex
+// requests (model in the URL path, not the body) through the full synthesized
+// middleware chain against an in-process management stack and a fake upstream.
+// With a Sonnet-only guardrail, Opus must be denied (model_blocked) before the
+// upstream and Sonnet must reach it. Two provider shapes exercise different
+// code: "catch_all" (no models → only the guardrail can block Opus) and
+// "versioned_models" (raw "@version" ids → the router must normalize to route
+// Sonnet while the guardrail still blocks Opus).
+func TestReverseProxy_VertexGuardrail_ModelAllowlist(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("sqlite store not supported on Windows")
+	}
+
+	cases := []struct {
+		name           string
+		providerModels []agentNetworkTypes.ProviderModel
+	}{
+		{name: "catch_all", providerModels: nil},
+		{name: "versioned_models", providerModels: []agentNetworkTypes.ProviderModel{
+			{ID: "claude-sonnet-4-5@20250929"},
+			{ID: "claude-opus-4-6@20250514"},
+		}},
+	}
+	for _, tc := range cases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			runVertexGuardrailCase(t, tc.providerModels)
+		})
+	}
+}
+
+func runVertexGuardrailCase(t *testing.T, providerModels []agentNetworkTypes.ProviderModel) {
+	t.Helper()
+
+	const (
+		testAccountID = "acct-vertex-guard-1"
+		testAdminUser = "user-admin-1"
+		adminGroupID  = "grp-admins"
+		providerID    = "prov-vertex-test"
+		guardrailID   = "ainguard-sonnet-only"
+		cluster       = "test.proxy.local"
+		subdomain     = "vertexguard"
+	)
+	testLogger := log.New()
+	testLogger.SetLevel(log.PanicLevel)
+
+	ctx := context.Background()
+
+	// Fake Vertex upstream: a hit on the disallowed model means a guardrail miss.
+	var upstreamHits atomic.Int64
+	upstreamBody := []byte(`{"id":"msg_x","type":"message","role":"assistant","model":"claude","content":[{"type":"text","text":"pong"}],"usage":{"input_tokens":5,"output_tokens":2}}`)
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		upstreamHits.Add(1)
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write(upstreamBody)
+	}))
+	t.Cleanup(upstream.Close)
+
+	// In-process management gRPC (bufconn) over a real sqlite store + manager.
+	st, cleanup, err := store.NewTestStoreFromSQL(ctx, "", t.TempDir())
+	require.NoError(t, err, "real sqlite test store must come up")
+	t.Cleanup(cleanup)
+
+	anMgr := agentnetwork.NewManager(st, nil, nil, nil)
+	server := &mgmtgrpc.ProxyServiceServer{}
+	server.SetAgentNetworkLimitsService(anMgr)
+
+	lis := bufconn.Listen(1024 * 1024)
+	srv := grpc.NewServer()
+	proto.RegisterProxyServiceServer(srv, server)
+	go func() { _ = srv.Serve(lis) }()
+	t.Cleanup(srv.Stop)
+
+	conn, err := grpc.NewClient("passthrough:///bufnet",
+		grpc.WithContextDialer(func(_ context.Context, _ string) (net.Conn, error) { return lis.Dial() }),
+		grpc.WithTransportCredentials(insecure.NewCredentials()),
+	)
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = conn.Close() })
+	mgmtClient := proto.NewProxyServiceClient(conn)
+
+	require.NoError(t, st.SaveAgentNetworkSettings(ctx, &agentNetworkTypes.Settings{
+		AccountID: testAccountID,
+		Cluster:   cluster,
+		Subdomain: subdomain,
+	}))
+	require.NoError(t, st.SaveAgentNetworkProvider(ctx, &agentNetworkTypes.Provider{
+		ID:          providerID,
+		AccountID:   testAccountID,
+		ProviderID:  "vertex_ai_api",
+		Name:        "vertex-guard-test",
+		UpstreamURL: upstream.URL,
+		// A static bearer (not "keyfile::…") so the router injects a static auth
+		// header instead of minting a GCP token, which needs network egress and
+		// would deny before the guardrail runs, masking the decision under test.
+		APIKey:            "static-vertex-token",
+		Enabled:           true,
+		Models:            providerModels,
+		SessionPrivateKey: "priv",
+		SessionPublicKey:  "pub",
+	}))
+	// Guardrail allowlisting ONLY Sonnet.
+	require.NoError(t, st.SaveAgentNetworkGuardrail(ctx, &agentNetworkTypes.Guardrail{
+		ID:        guardrailID,
+		AccountID: testAccountID,
+		Name:      "sonnet-only",
+		Checks: agentNetworkTypes.GuardrailChecks{
+			ModelAllowlist: agentNetworkTypes.GuardrailModelAllowlist{
+				Enabled: true,
+				Models:  []string{"claude-sonnet-4-5"},
+			},
+		},
+	}))
+	require.NoError(t, st.SaveAgentNetworkPolicy(ctx, &agentNetworkTypes.Policy{
+		ID:                     "ainpol-vertex-guard",
+		AccountID:              testAccountID,
+		Name:                   "admins-vertex",
+		Enabled:                true,
+		SourceGroups:           []string{adminGroupID},
+		DestinationProviderIDs: []string{providerID},
+		GuardrailIDs:           []string{guardrailID},
+	}))
+
+	services, err := agentnetwork.SynthesizeServices(ctx, st, testAccountID)
+	require.NoError(t, err)
+	require.Len(t, services, 1, "exactly one synth service expected")
+	synthSvc := services[0]
+	require.NotEmpty(t, synthSvc.Targets, "synth target must exist")
+
+	mwbuiltin.Configure(ctx, t.TempDir(), nil, testLogger, mgmtClient)
+	registry := mwbuiltin.DefaultRegistry()
+	mwMetrics, err := middleware.NewMetrics(nil)
+	require.NoError(t, err)
+	mwMgr := middleware.NewManager(0, mwMetrics, testLogger)
+	mwMgr.SetResolver(middleware.NewResolver(registry))
+
+	specs := make([]middleware.Spec, 0, len(synthSvc.Targets[0].Options.Middlewares))
+	for _, mw := range synthSvc.Targets[0].Options.Middlewares {
+		var slot middleware.Slot
+		switch mw.Slot {
+		case rpservice.MiddlewareSlotOnRequest:
+			slot = middleware.SlotOnRequest
+		case rpservice.MiddlewareSlotOnResponse:
+			slot = middleware.SlotOnResponse
+		case rpservice.MiddlewareSlotTerminal:
+			slot = middleware.SlotTerminal
+		default:
+			t.Fatalf("unknown middleware slot %q on %s", mw.Slot, mw.ID)
+		}
+		specs = append(specs, middleware.Spec{
+			ID:        mw.ID,
+			Slot:      slot,
+			Enabled:   mw.Enabled,
+			FailMode:  middleware.FailOpen,
+			Timeout:   middleware.DefaultTimeout,
+			RawConfig: append([]byte(nil), mw.ConfigJSON...),
+			CanMutate: mw.CanMutate,
+		})
+	}
+
+	serviceIDStr := synthSvc.ID
+	require.NoError(t, mwMgr.Rebuild(serviceIDStr, []middleware.PathTargetBinding{{
+		ServiceID: serviceIDStr,
+		PathID:    "/",
+		Specs:     specs,
+	}}))
+
+	upstreamURL, err := url.Parse(upstream.URL)
+	require.NoError(t, err)
+
+	rp := proxy.NewReverseProxy(http.DefaultTransport, "auto", nil, testLogger, proxy.WithMiddlewareManager(mwMgr))
+	rp.AddMapping(proxy.Mapping{
+		ID:        nbproxytypes.ServiceID(serviceIDStr),
+		AccountID: nbproxytypes.AccountID(testAccountID),
+		Host:      synthSvc.Domain,
+		Paths: map[string]*proxy.PathTarget{
+			"/": {
+				URL:            upstreamURL,
+				DirectUpstream: true,
+				AgentNetwork:   true,
+				Middlewares:    specs,
+				CaptureConfig: &bodytap.Config{
+					MaxRequestBytes:  1 << 20,
+					MaxResponseBytes: 1 << 20,
+					ContentTypes:     []string{"application/json", "text/event-stream"},
+				},
+			},
+		},
+	})
+
+	// No "model" field — the model lives in the URL path, as Vertex clients send.
+	const vertexBody = `{"anthropic_version":"vertex-2023-10-16","max_tokens":64,"messages":[{"role":"user","content":"Reply with exactly: pong"}]}`
+
+	send := func(t *testing.T, model string) (int, int64, string) {
+		t.Helper()
+		before := upstreamHits.Load()
+		path := "/v1/projects/corp-gcp-it-all-claude/locations/global/publishers/anthropic/models/" + model + ":rawPredict"
+		req := httptest.NewRequest("POST", "https://"+synthSvc.Domain+path, strings.NewReader(vertexBody))
+		req.Host = synthSvc.Domain
+		req.Header.Set("Content-Type", "application/json")
+
+		cd := proxy.NewCapturedData("req-" + model)
+		cd.SetServiceID(nbproxytypes.ServiceID(serviceIDStr))
+		cd.SetAccountID(nbproxytypes.AccountID(testAccountID))
+		cd.SetUserID(testAdminUser)
+		cd.SetUserGroups([]string{adminGroupID})
+		cd.SetAuthMethod("tunnel_peer")
+		req = req.WithContext(proxy.WithCapturedData(req.Context(), cd))
+
+		w := httptest.NewRecorder()
+		rp.ServeHTTP(w, req)
+		return w.Code, upstreamHits.Load() - before, w.Body.String()
+	}
+
+	// Opus must be denied by the guardrail (model_blocked, not the router's
+	// model_not_routable) before reaching the upstream — the customer-reported bug.
+	t.Run("opus_denied_by_guardrail", func(t *testing.T) {
+		code, hits, body := send(t, "claude-opus-4-6")
+		assert.Equal(t, http.StatusForbidden, code, "Opus must be denied under a Sonnet-only allowlist; body=%s", body)
+		assert.Contains(t, body, "llm_policy.model_blocked", "denial must come from the guardrail allowlist, not routing; body=%s", body)
+		assert.Equal(t, int64(0), hits, "a denied request must never reach the Vertex upstream")
+	})
+
+	// The allowed model (Sonnet) passes the guardrail and reaches the upstream.
+	t.Run("sonnet_allowed", func(t *testing.T) {
+		code, hits, body := send(t, "claude-sonnet-4-5")
+		assert.Equal(t, http.StatusOK, code, "Sonnet is allowlisted and must be served; body=%s", body)
+		assert.Equal(t, int64(1), hits, "the allowed request must reach the Vertex upstream exactly once")
+	})
+}