From 13138d2d11ed850b4310029aeaaad526516014a3 Mon Sep 17 00:00:00 2001
From: tmat <tomas.matousek@microsoft.com>
Date: Fri, 6 Feb 2026 13:14:29 -0800
Subject: [PATCH 1/3] Lock around access to s_dynamicSymbols

---
 .../DynamicSymbolExtensions.cs                | 50 +++++++------------
 1 file changed, 17 insertions(+), 33 deletions(-)

diff --git a/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs b/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs
index c59d18c7bec1..d762a51d3fde 100644
--- a/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs
+++ b/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs
@@ -6,50 +6,34 @@ namespace System.CommandLine.StaticCompletions;
 /// </summary>
 public static class DynamicSymbolExtensions
 {
+    private static readonly Lock s_guard = new();
+
     /// <summary>
     /// The state that is used to track which symbols are dynamic.
     /// </summary>
     private static readonly Dictionary<Symbol, bool> s_dynamicSymbols = [];
 
-    extension(Option option)
+    extension(Symbol option)
     {
         /// <summary>
         /// Indicates whether this option requires a dynamic call into the dotnet process to compute completions.
         /// </summary>
         public bool IsDynamic
         {
-            get => s_dynamicSymbols.GetValueOrDefault(option, false);
-            set => s_dynamicSymbols[option] = value;
-        }
-
-        /// <summary>
-        /// Mark this option as requiring dynamic completions.
-        /// </summary>
-        /// <returns></returns>
-        public Option RequiresDynamicCompletion()
-        {
-            option.IsDynamic = true;
-            return option;
-        }
-    }
-
-    extension(Argument argument)
-    {
-        /// Indicates whether this argument requires a dynamic call into the dotnet process to compute completions.
-        public bool IsDynamic
-        {
-            get => s_dynamicSymbols.GetValueOrDefault(argument, false);
-            set => s_dynamicSymbols[argument] = value;
-        }
-
-        /// <summary>
-        /// Mark this argument as requiring dynamic completions.
-        /// </summary>
-        /// <returns></returns>
-        public Argument RequiresDynamicCompletion()
-        {
-            argument.IsDynamic = true;
-            return argument;
+            get
+            {
+                lock (s_guard)
+                {
+                    return s_dynamicSymbols.GetValueOrDefault(option, false);
+                }
+            }
+            set
+            {
+                lock (s_guard)
+                {
+                    s_dynamicSymbols[option] = value;
+                }
+            }
         }
     }
 }

From 646c716df407a8ccf6c87039e151a412f5e9925f Mon Sep 17 00:00:00 2001
From: tmat <tomas.matousek@microsoft.com>
Date: Fri, 6 Feb 2026 13:18:05 -0800
Subject: [PATCH 2/3] Specialize

---
 .../DynamicSymbolExtensions.cs                | 26 ++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs b/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs
index d762a51d3fde..84bf0b49c8b4 100644
--- a/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs
+++ b/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs
@@ -13,7 +13,7 @@ public static class DynamicSymbolExtensions
     /// </summary>
     private static readonly Dictionary<Symbol, bool> s_dynamicSymbols = [];
 
-    extension(Symbol option)
+    extension(Option option)
     {
         /// <summary>
         /// Indicates whether this option requires a dynamic call into the dotnet process to compute completions.
@@ -36,4 +36,28 @@ public bool IsDynamic
             }
         }
     }
+
+    extension(Argument option)
+    {
+        /// <summary>
+        /// Indicates whether this argument requires a dynamic call into the dotnet process to compute completions.
+        /// </summary>
+        public bool IsDynamic
+        {
+            get
+            {
+                lock (s_guard)
+                {
+                    return s_dynamicSymbols.GetValueOrDefault(option, false);
+                }
+            }
+            set
+            {
+                lock (s_guard)
+                {
+                    s_dynamicSymbols[option] = value;
+                }
+            }
+        }
+    }
 }

From 00d6bc689f870f64637f8c3703fa35a6d4d60e62 Mon Sep 17 00:00:00 2001
From: tmat <tomas.matousek@microsoft.com>
Date: Fri, 6 Feb 2026 13:19:44 -0800
Subject: [PATCH 3/3] Rename

---
 .../DynamicSymbolExtensions.cs                              | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs b/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs
index 84bf0b49c8b4..18c7275540da 100644
--- a/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs
+++ b/src/System.CommandLine.StaticCompletions/DynamicSymbolExtensions.cs
@@ -37,7 +37,7 @@ public bool IsDynamic
         }
     }
 
-    extension(Argument option)
+    extension(Argument argument)
     {
         /// <summary>
         /// Indicates whether this argument requires a dynamic call into the dotnet process to compute completions.
@@ -48,14 +48,14 @@ public bool IsDynamic
             {
                 lock (s_guard)
                 {
-                    return s_dynamicSymbols.GetValueOrDefault(option, false);
+                    return s_dynamicSymbols.GetValueOrDefault(argument, false);
                 }
             }
             set
             {
                 lock (s_guard)
                 {
-                    s_dynamicSymbols[option] = value;
+                    s_dynamicSymbols[argument] = value;
                 }
             }
         }