From d304d750e353495b94e2aef00968dbbd045c580e Mon Sep 17 00:00:00 2001
From: Pengyi Peng <74917296+pengpengyi92@users.noreply.github.com>
Date: Wed, 26 Aug 2026 23:08:27 +0800
Subject: [PATCH] Validate option underlying subscription resolution

---
 Algorithm/QCAlgorithm.cs                 |  8 ++++
 Common/Messages/Messages.Algorithm.cs    | 12 ++++++
 Tests/Algorithm/AlgorithmAddDataTests.cs | 48 ++++++++++++++++++++++++
 3 files changed, 68 insertions(+)

diff --git a/Algorithm/QCAlgorithm.cs b/Algorithm/QCAlgorithm.cs
index daf195a7a1e1..1d38fd7d3714 100644
--- a/Algorithm/QCAlgorithm.cs
+++ b/Algorithm/QCAlgorithm.cs
@@ -2454,6 +2454,14 @@ public Option AddOptionContract(Symbol symbol, Resolution? resolution = null, bo
                 }
             }
 
+            var optionResolution = resolution ?? UniverseSettings.Resolution;
+            var underlyingResolution = underlyingConfigs.GetHighestResolution();
+            if (underlyingResolution > optionResolution)
+            {
+                throw new ArgumentException(Messages.QCAlgorithm.AddOptionContractUnderlyingResolution(
+                    symbol, optionResolution, underlying, underlyingResolution));
+            }
+
             var configs = SubscriptionManager.SubscriptionDataConfigService.Add(symbol, resolution, fillForward, extendedMarketHours,
                 dataNormalizationMode: DataNormalizationMode.Raw);
             var option = (Option)Securities.CreateSecurity(symbol, configs, leverage, underlying: underlyingSecurity);
diff --git a/Common/Messages/Messages.Algorithm.cs b/Common/Messages/Messages.Algorithm.cs
index 288a0197cbcc..7784b27b12d8 100644
--- a/Common/Messages/Messages.Algorithm.cs
+++ b/Common/Messages/Messages.Algorithm.cs
@@ -99,6 +99,18 @@ public static string AddDataInvalidPyObjectType(string repr)
                 return $"{AlgorithmPrefix()}.{FormatCode("AddData")}(): the first argument must be a custom data type (a Python class deriving from {FormatCode("PythonData")} or a CLR {FormatCode("BaseData")} type), but received {repr}. " +
                     $"To subscribe to built-in asset classes use, for example, {FormatCode("AddEquity")} or {FormatCode("AddCrypto")}.";
             }
+
+            /// <summary>
+            /// Returns a string message saying an option cannot use a finer resolution than its underlying
+            /// </summary>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public static string AddOptionContractUnderlyingResolution(global::QuantConnect.Symbol option, Resolution optionResolution,
+                global::QuantConnect.Symbol underlying, Resolution underlyingResolution)
+            {
+                return $"{AlgorithmPrefix()}.{FormatCode("AddOptionContract")}(): option contract {option} uses {optionResolution} resolution, " +
+                    $"which is finer than its underlying {underlying} subscription at {underlyingResolution} resolution. " +
+                    $"Add the underlying at {optionResolution} resolution or finer before adding the option contract so its implied volatility and Greeks use a current underlying price.";
+            }
         }
 
         /// <summary>
diff --git a/Tests/Algorithm/AlgorithmAddDataTests.cs b/Tests/Algorithm/AlgorithmAddDataTests.cs
index d4834147b4aa..4e6d0fbadad7 100644
--- a/Tests/Algorithm/AlgorithmAddDataTests.cs
+++ b/Tests/Algorithm/AlgorithmAddDataTests.cs
@@ -724,6 +724,54 @@ public void AddOptionContractWithDelistedUnderlyingThrows(SecurityType underlyin
             Assert.IsTrue(exception.Message.Contains("is delisted"), $"Unexpected exception message: {exception.Message}");
         }
 
+        [TestCase(Resolution.Daily, Resolution.Minute, true)]
+        [TestCase(Resolution.Hour, Resolution.Minute, true)]
+        [TestCase(Resolution.Minute, Resolution.Minute, false)]
+        [TestCase(Resolution.Second, Resolution.Minute, false)]
+        public void AddOptionContractValidatesUnderlyingResolution(
+            Resolution underlyingResolution, Resolution optionResolution, bool shouldThrow)
+        {
+            var algorithm = Algorithm();
+            var underlying = algorithm.AddEquity("SPY", underlyingResolution).Symbol;
+            var option = Symbol.CreateOption(underlying, Market.USA, OptionStyle.American, OptionRight.Call,
+                100m, new DateTime(2027, 1, 15));
+
+            if (shouldThrow)
+            {
+                var exception = Assert.Throws<ArgumentException>(() => algorithm.AddOptionContract(option, optionResolution));
+                StringAssert.Contains("finer than its underlying", exception.Message);
+                StringAssert.Contains($"Add the underlying at {optionResolution} resolution or finer", exception.Message);
+            }
+            else
+            {
+                Assert.DoesNotThrow(() => algorithm.AddOptionContract(option, optionResolution));
+            }
+        }
+
+        [Test]
+        public void AddOptionContractUsesHighestAvailableUnderlyingResolution()
+        {
+            var algorithm = Algorithm();
+            var underlying = algorithm.AddEquity("SPY", Resolution.Daily).Symbol;
+            algorithm.AddEquity("SPY", Resolution.Minute);
+            var option = Symbol.CreateOption(underlying, Market.USA, OptionStyle.American, OptionRight.Call,
+                100m, new DateTime(2027, 1, 15));
+
+            Assert.DoesNotThrow(() => algorithm.AddOptionContract(option, Resolution.Minute));
+        }
+
+        [Test]
+        public void AddOptionContractValidatesUnderlyingResolutionFromUniverseSettings()
+        {
+            var algorithm = Algorithm();
+            algorithm.UniverseSettings.Resolution = Resolution.Minute;
+            var underlying = algorithm.AddEquity("SPY", Resolution.Daily).Symbol;
+            var option = Symbol.CreateOption(underlying, Market.USA, OptionStyle.American, OptionRight.Call,
+                100m, new DateTime(2027, 1, 15));
+
+            Assert.Throws<ArgumentException>(() => algorithm.AddOptionContract(option));
+        }
+
         private static SubscriptionDataConfig GetMatchingSubscription(QCAlgorithm algorithm, Symbol symbol, Type type)
         {
             // find a subscription matchin the requested type with a higher resolution than requested