diff --git a/tests/test_verifier_contract.py b/tests/test_verifier_contract.py
index 9f8784a..0ab2683 100644
--- a/tests/test_verifier_contract.py
+++ b/tests/test_verifier_contract.py
@@ -4,6 +4,7 @@ import io
 import json
 import sys
 import unittest
+from pathlib import Path
 from types import SimpleNamespace
 from unittest.mock import Mock, patch
 
@@ -27,6 +28,44 @@ class TestVerifierContract(unittest.TestCase):
         with patch.object(generate_traffic, "fetch_json", return_value={"pipeline": {"worker_status": "unreachable"}}):
             self.assertIsNone(generate_traffic.stats_snapshot("http://unused"))
 
+    def test_stats_snapshot_keeps_received_and_acknowledged_counts_separate(self):
+        response = {
+            "pipeline": {
+                "total_received": 1570,
+                "total_acknowledged": 1540,
+                "total_processed": 1520,
+                "total_dlq": 50,
+                "in_flight_buffer": 0,
+            },
+            "breakdown": {"dlq_by_reason": {}},
+        }
+        with patch.object(generate_traffic, "fetch_json", return_value=response):
+            snapshot = generate_traffic.stats_snapshot("http://unused")
+        self.assertEqual(snapshot["total_received"], 1570)
+        self.assertEqual(snapshot["total_acknowledged"], 1540)
+
+    def test_assessment_metric_deltas_match_received_and_acknowledged_contract(self):
+        before = {
+            "total_received": 10,
+            "total_acknowledged": 8,
+            "total_processed": 7,
+            "total_dlq": 2,
+        }
+        after = {
+            "total_received": 1580,
+            "total_acknowledged": 1548,
+            "total_processed": 1527,
+            "total_dlq": 52,
+        }
+        self.assertTrue(generate_traffic.assessment_metrics_match(before, after))
+        after["total_acknowledged"] += 1
+        self.assertFalse(generate_traffic.assessment_metrics_match(before, after))
+
+    def test_k6_latency_guardrail_is_opt_in(self):
+        script = (Path(__file__).parents[1] / "scripts" / "load_test.js").read_text()
+        self.assertIn("__ENV.P95_MS ?", script)
+        self.assertNotIn("__ENV.P95_MS || 50", script)
+
     def test_overflowing_json_float_is_rejected_even_in_extra_fields(self):
         with self.assertRaises(PayloadError):
             parse_payload(b'{"extra":1e400}')