fix(rate-limits): treat empty policies as unlimited

apps/api/internal/runner/limits_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/easyai/easyai-ai-gateway/apps/api/internal/clients"
+	"github.com/easyai/easyai-ai-gateway/apps/api/internal/store"
 )
 
 func TestTokenUsageAmountsUsesActualUsageForTPM(t *testing.T) {
@@ -27,3 +28,39 @@ func TestTokenUsageAmountsFallsBackToInputOutputTotal(t *testing.T) {
 		t.Fatalf("expected total token fallback 8, got %v", got["tpm_total"])
 	}
 }
+
+func TestEffectiveRateLimitPolicyTreatsEmptyRuntimePolicyAsUnlimited(t *testing.T) {
+	policy := effectiveRateLimitPolicy(store.RuntimeModelCandidate{
+		PlatformRateLimitPolicy: map[string]any{"rules": []any{
+			map[string]any{"metric": "rpm", "limit": 500},
+		}},
+		RuntimePolicySetID:     "runtime-policy-1",
+		RuntimeRateLimitPolicy: map[string]any{"rules": []any{}},
+	})
+
+	if hasRules(policy) {
+		t.Fatalf("expected empty runtime policy to clear inherited limits, got %+v", policy)
+	}
+}
+
+func TestReservationsFromPolicySkipsNonPositiveLimits(t *testing.T) {
+	reservations := reservationsFromPolicy(
+		"platform_model",
+		"model-1",
+		"Model 1",
+		nil,
+		map[string]any{"rules": []any{
+			map[string]any{"metric": "rpm", "limit": -1},
+			map[string]any{"metric": "tpm_total", "limit": 0},
+			map[string]any{"metric": "concurrent", "limit": 2},
+		}},
+		map[string]any{"prompt": "hello"},
+	)
+
+	if len(reservations) != 1 {
+		t.Fatalf("expected only the positive concurrent rule to reserve, got %+v", reservations)
+	}
+	if reservations[0].Metric != "concurrent" || reservations[0].Limit != 2 {
+		t.Fatalf("expected concurrent reservation with limit 2, got %+v", reservations[0])
+	}
+}