diff --git a/backend/tests/test_api_semantics_and_utc.py b/backend/tests/test_api_semantics_and_utc.py
index 26de2f1..6c8d14a 100644
--- a/backend/tests/test_api_semantics_and_utc.py
+++ b/backend/tests/test_api_semantics_and_utc.py
@@ -112,3 +112,39 @@ def test_bootstrap_schema_contains_migrated_core_columns_and_tables():
 
     for snippet in required_snippets:
         assert snippet in schema_sql
+
+
+def test_insert_engine_event_serializes_nested_datetimes():
+    from indian_paper_trading_strategy.engine.db import insert_engine_event
+
+    class FakeCursor:
+        def __init__(self):
+            self.params = None
+
+        def execute(self, _sql, params):
+            self.params = params
+
+    cursor = FakeCursor()
+    event_ts = datetime(2026, 4, 15, 9, 0, tzinfo=timezone.utc)
+    payload_ts = datetime(2026, 4, 15, 9, 1, tzinfo=timezone.utc)
+
+    insert_engine_event(
+        cursor,
+        "ORDER_PLACED",
+        data={
+            "order_id": "order-1",
+            "timestamp": payload_ts,
+            "history": [payload_ts],
+        },
+        meta={"checked_at": payload_ts},
+        ts=event_ts,
+        user_id="user-1",
+        run_id="run-1",
+    )
+
+    data_json = cursor.params[4]
+    meta_json = cursor.params[6]
+
+    assert data_json.adapted["timestamp"] == payload_ts.isoformat()
+    assert data_json.adapted["history"] == [payload_ts.isoformat()]
+    assert meta_json.adapted["checked_at"] == payload_ts.isoformat()
diff --git a/indian_paper_trading_strategy/engine/db.py b/indian_paper_trading_strategy/engine/db.py
index 4b913d8..20e7d73 100644
--- a/indian_paper_trading_strategy/engine/db.py
+++ b/indian_paper_trading_strategy/engine/db.py
@@ -2,8 +2,10 @@ import os
 import threading
 import time
 from contextlib import contextmanager
-from datetime import datetime, timedelta, timezone
+from datetime import date, datetime, timedelta, timezone
 from contextvars import ContextVar
+from decimal import Decimal
+from uuid import UUID
 
 import psycopg2
 from psycopg2 import pool
@@ -142,8 +144,24 @@ def db_transaction():
             raise
 
 
-def _utc_now():
-    return datetime.utcnow().replace(tzinfo=timezone.utc)
+def _utc_now():
+    return datetime.utcnow().replace(tzinfo=timezone.utc)
+
+
+def _json_safe(value):
+    if isinstance(value, datetime):
+        return value.isoformat()
+    if isinstance(value, date):
+        return value.isoformat()
+    if isinstance(value, Decimal):
+        return float(value)
+    if isinstance(value, UUID):
+        return str(value)
+    if isinstance(value, dict):
+        return {str(key): _json_safe(item) for key, item in value.items()}
+    if isinstance(value, (list, tuple, set)):
+        return [_json_safe(item) for item in value]
+    return value
 
 
 def set_context(user_id: str | None, run_id: str | None):
@@ -323,14 +341,14 @@ def insert_engine_event(
         INSERT INTO engine_event (user_id, run_id, ts, event, data, message, meta)
         VALUES (%s, %s, %s, %s, %s, %s, %s)
         """,
-        (
-            scope_user,
-            scope_run,
-            when,
-            event,
-            Json(data) if data is not None else None,
-            message,
-            Json(meta) if meta is not None else None,
+        (
+            scope_user,
+            scope_run,
+            when,
+            event,
+            Json(_json_safe(data)) if data is not None else None,
+            message,
+            Json(_json_safe(meta)) if meta is not None else None,
         ),
     )