From d50371729a750d921b8271a2ee5ab1a8f6597241 Mon Sep 17 00:00:00 2001
From: Daniel Cazzulino <daniel@cazzulino.com>
Date: Mon, 17 Nov 2025 16:50:26 -0300
Subject: [PATCH] Clarify exception handling in ConversationId property (#1457)

Update XML documentation to clarify exception behavior.

See `ChatClientAgentThreadTests.SetConversationIdThrowsWhenMessageStoreIsSet` which already verifies this is the actual behavior.

Co-authored-by: Chris <66376200+crickman@users.noreply.github.com>
---
 .../Microsoft.Agents.AI/ChatClient/ChatClientAgentThread.cs  | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgentThread.cs b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgentThread.cs
index ad224e6777..f0f51895b2 100644
--- a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgentThread.cs
+++ b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgentThread.cs
@@ -75,8 +75,8 @@ public class ChatClientAgentThread : AgentThread
     /// <remarks>
     /// <para>
     /// Note that either <see cref="ConversationId"/> or <see cref="MessageStore "/> may be set, but not both.
-    /// If <see cref="MessageStore "/> is not null, and <see cref="ConversationId"/> is set, <see cref="MessageStore "/>
-    /// will be reverted to null, and vice versa.
+    /// If <see cref="MessageStore "/> is not null, setting <see cref="ConversationId"/> will throw an
+    /// <see cref="InvalidOperationException "/> exception.
     /// </para>
     /// <para>
     /// This property may be null in the following cases:
@@ -91,6 +91,7 @@ public class ChatClientAgentThread : AgentThread
     /// to fork the thread with each iteration.
     /// </para>
     /// </remarks>
+    /// <exception cref="InvalidOperationException">Attempted to set a conversation ID but a <see cref="MessageStore"/> is already set.</exception>
     public string? ConversationId
     {
         get => this._conversationId;