diff --git a/core/models.py b/core/models.py
index da126c1..cb4654e 100644
--- a/core/models.py
+++ b/core/models.py
@@ -1,6 +1,8 @@
 from __future__ import annotations
 
 from dataclasses import dataclass, field
+import time
+import uuid
 from typing import List, Dict, Any
 
 
@@ -29,6 +31,18 @@ class PlanDelta:
     delta_id: str
     fleet_id: str
     changes: Dict[str, Any]
+    # Metadata for verifiable reconciliation and auditing
+    version: int = 1
+    nonce: str | None = None
+    timestamp: float | None = None
+
+    def __post_init__(self):
+        # Ensure timestamp is set for auditing
+        if self.timestamp is None:
+            self.timestamp = time.time()
+        # Ensure a unique nonce for replay-safe reconciliation
+        if self.nonce is None:
+            self.nonce = uuid.uuid4().hex
 
 
 @dataclass
diff --git a/tests/test_fleetopt.py b/tests/test_fleetopt.py
index 711c2bf..f6590a5 100644
--- a/tests/test_fleetopt.py
+++ b/tests/test_fleetopt.py
@@ -70,3 +70,8 @@ def test_two_fleets_cross_exchange_basic():
     delta = asyncio.get_event_loop().run_until_complete(run())
     assert delta.fleet_id == plan_a.fleet_id
     assert isinstance(delta.changes, dict)
+    # New metadata should be present and well-formed
+    assert isinstance(delta.version, int)
+    assert delta.version >= 1
+    assert isinstance(delta.nonce, str) and len(delta.nonce) > 0
+    assert isinstance(delta.timestamp, float)