diff --git a/mercurymesh_federated_reproducible_marke/tests/test_replay.py b/mercurymesh_federated_reproducible_marke/tests/test_replay.py
new file mode 100644
index 0000000..2eb739b
--- /dev/null
+++ b/mercurymesh_federated_reproducible_marke/tests/test_replay.py
@@ -0,0 +1,29 @@
+import pytest
+
+from mercurymesh_federated_reproducible_marke.core import MarketStateSnapshot, PlanDelta
+from mercurymesh_federated_reproducible_marke.replay import DeterministicReplayer
+
+
+def test_replay_deltas_deterministic_final_state():
+    start = MarketStateSnapshot(
+        assets=["A", "B"],
+        bids={"A": 10.0, "B": 20.0},
+        offers={"A": 11.0, "B": 21.0},
+        last_trade_times={"A": "2026-01-01T00:00:00Z", "B": "2026-01-01T00:00:00Z"},
+        liquidity_metrics={"A": 0.5, "B": 0.6},
+        timestamp="2026-01-01T00:00:00Z",
+        version=1,
+    )
+
+    d1 = PlanDelta(delta={"A": 1.0, "B": -0.5}, timestamp="2026-01-01T00:00:01Z", author="p1", contract_id="root", privacy_budget=0.0)
+    d2 = PlanDelta(delta={"A": -0.25, "B": 0.75}, timestamp="2026-01-01T00:00:02Z", author="p2", contract_id="root", privacy_budget=0.0)
+
+    final_state = DeterministicReplayer.replay(start, [d1, d2])
+
+    # Expected final values after applying deltas in sequence
+    assert pytest.approx(final_state.bids["A"], rel=1e-9) == 10.75
+    assert pytest.approx(final_state.bids["B"], rel=1e-9) == 20.25
+    assert pytest.approx(final_state.offers["A"], rel=1e-9) == 10.25
+    assert pytest.approx(final_state.offers["B"], rel=1e-9) == 20.75
+    # Version should have incremented from the start state (1 -> 3 after two deltas in this model)
+    assert final_state.version == 3