diff --git a/dotnet/samples/GettingStarted/AgentProviders/Agent_With_AzureAIAgent/Program.cs b/dotnet/samples/GettingStarted/AgentProviders/Agent_With_AzureAIAgent/Program.cs
index d6eb139ebb..76c7ffdcd6 100644
--- a/dotnet/samples/GettingStarted/AgentProviders/Agent_With_AzureAIAgent/Program.cs
+++ b/dotnet/samples/GettingStarted/AgentProviders/Agent_With_AzureAIAgent/Program.cs
@@ -22,10 +22,10 @@ var agentDefinition = new PromptAgentDefinition(model: deploymentName) { Instruc
 var agentVersion = agentsClient.CreateAgentVersion(agentName: JokerName, definition: agentDefinition).Value;
 
 // You can retrieve an already created server side agent as an AIAgent.
-AIAgent existingAgent = await agentsClient.GetAIAgentAsync(deploymentName, agentVersion.Name);
+AIAgent existingAgent = await agentsClient.GetAIAgentAsync(agentVersion.Name);
 
 // You can also create a server side persistent agent and return it as an AIAgent directly.
-var createdAgent = agentsClient.CreateAIAgent(deploymentName, name: JokerName, instructions: JokerInstructions);
+var createdAgent = agentsClient.CreateAIAgent(name: JokerName, model: deploymentName, instructions: JokerInstructions);
 
 // You can then invoke the agent like any other AIAgent.
 AgentThread thread = existingAgent.GetNewThread();
diff --git a/dotnet/src/Microsoft.Agents.AI.AzureAIAgents/AgentsClientExtensions.cs b/dotnet/src/Microsoft.Agents.AI.AzureAIAgents/AgentsClientExtensions.cs
index 1df8a88282..4a72e15c2e 100644
--- a/dotnet/src/Microsoft.Agents.AI.AzureAIAgents/AgentsClientExtensions.cs
+++ b/dotnet/src/Microsoft.Agents.AI.AzureAIAgents/AgentsClientExtensions.cs
@@ -25,7 +25,6 @@ public static class AgentsClientExtensions
     /// Gets a runnable agent instance from the provided agent record.
     /// </summary>
     /// <param name="agentsClient">The client used to interact with Azure AI Agents. Cannot be <see langword="null"/>.</param>
-    /// <param name="model">The model to be used by the agent.</param>
     /// <param name="agentRecord">The agent record to be converted. The latest version will be used. Cannot be <see langword="null"/>.</param>
     /// <param name="chatOptions">The default <see cref="ChatOptions"/> to use when interacting with the agent.</param>
     /// <param name="clientFactory">Provides a way to customize the creation of the underlying <see cref="IChatClient"/> used by the agent.</param>
@@ -34,7 +33,6 @@ public static class AgentsClientExtensions
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations based on the latest version of the Azure AI Agent.</returns>
     public static ChatClientAgent GetAIAgent(
         this AgentsClient agentsClient,
-        string model,
         AgentRecord agentRecord,
         ChatOptions? chatOptions = null,
         Func<IChatClient, IChatClient>? clientFactory = null,
@@ -42,27 +40,24 @@ public static class AgentsClientExtensions
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(agentsClient);
-        Throw.IfNullOrWhitespace(model);
         Throw.IfNull(agentRecord);
 
-        return GetAIAgent(agentsClient, model, agentRecord.Versions.Latest, chatOptions, clientFactory, openAIClientOptions, cancellationToken);
+        return GetAIAgent(agentsClient, agentRecord.Versions.Latest, chatOptions, clientFactory, openAIClientOptions, cancellationToken);
     }
 
     /// <summary>
     /// Gets a runnable agent instance from the provided agent record.
     /// </summary>
     /// <param name="agentsClient">The client used to interact with Azure AI Agents. Cannot be <see langword="null"/>.</param>
-    /// <param name="model">The model to be used by the agent. Cannot be <see langword="null"/>.</param>
     /// <param name="agentVersion">The agent version to be converted. Cannot be <see langword="null"/>.</param>
     /// <param name="chatOptions">The default <see cref="ChatOptions"/> to use when interacting with the agent.</param>
     /// <param name="clientFactory">Provides a way to customize the creation of the underlying <see cref="IChatClient"/> used by the agent.</param>
     /// <param name="openAIClientOptions">An optional <see cref="OpenAIClientOptions"/> for configuring the underlying OpenAI client.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations based on the specified version of the Azure AI Agent.</returns>
-    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/>, <paramref name="model"/>, or <paramref name="agentVersion"/> is <see langword="null"/>.</exception>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/> or <paramref name="agentVersion"/> is <see langword="null"/>.</exception>
     public static ChatClientAgent GetAIAgent(
         this AgentsClient agentsClient,
-        string model,
         AgentVersion agentVersion,
         ChatOptions? chatOptions = null,
         Func<IChatClient, IChatClient>? clientFactory = null,
@@ -70,29 +65,26 @@ public static class AgentsClientExtensions
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(agentsClient);
-        Throw.IfNullOrWhitespace(model);
         Throw.IfNull(agentVersion);
 
-        return GetAIAgent(agentsClient, model, agentVersion, new ChatClientAgentOptions() { ChatOptions = chatOptions }, clientFactory, openAIClientOptions, cancellationToken);
+        return GetAIAgent(agentsClient, agentVersion, new ChatClientAgentOptions() { ChatOptions = chatOptions }, clientFactory, openAIClientOptions, cancellationToken);
     }
 
     /// <summary>
     /// Retrieves an existing server side agent, wrapped as a <see cref="ChatClientAgent"/> using the provided <see cref="AgentsClient"/>.
     /// </summary>
     /// <param name="agentsClient">The <see cref="AgentsClient"/> to create the <see cref="ChatClientAgent"/> with. Cannot be <see langword="null"/>.</param>
-    /// <param name="model">The model to be used by the agent. Cannot be <see langword="null"/> or whitespace.</param>
     /// <param name="name">The name of the server side agent to create a <see cref="ChatClientAgent"/> for. Cannot be <see langword="null"/> or whitespace.</param>
     /// <param name="chatOptions">The default <see cref="ChatOptions"/> to use when interacting with the agent.</param>
     /// <param name="clientFactory">Provides a way to customize the creation of the underlying <see cref="IChatClient"/> used by the agent.</param>
     /// <param name="openAIClientOptions">An optional <see cref="OpenAIClientOptions"/> for configuring the underlying OpenAI client.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations based on the latest version of the named Azure AI Agent.</returns>
-    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/>, <paramref name="model"/>, or <paramref name="name"/> is <see langword="null"/>.</exception>
-    /// <exception cref="ArgumentException">Thrown when <paramref name="model"/> or <paramref name="name"/> is empty or whitespace, or when the agent with the specified name was not found.</exception>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/> or <paramref name="name"/> is <see langword="null"/>.</exception>
+    /// <exception cref="ArgumentException">Thrown when <paramref name="name"/> is empty or whitespace, or when the agent with the specified name was not found.</exception>
     /// <exception cref="InvalidOperationException">The agent with the specified name was not found.</exception>
     public static ChatClientAgent GetAIAgent(
         this AgentsClient agentsClient,
-        string model,
         string name,
         ChatOptions? chatOptions = null,
         Func<IChatClient, IChatClient>? clientFactory = null,
@@ -100,32 +92,29 @@ public static class AgentsClientExtensions
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(agentsClient);
-        Throw.IfNullOrWhitespace(model);
         Throw.IfNullOrWhitespace(name);
 
         var agentRecord = agentsClient.GetAgent(name, cancellationToken).Value
             ?? throw new InvalidOperationException($"Agent with name '{name}' not found.");
 
-        return GetAIAgent(agentsClient, model, agentRecord, chatOptions, clientFactory, openAIClientOptions, cancellationToken);
+        return GetAIAgent(agentsClient, agentRecord, chatOptions, clientFactory, openAIClientOptions, cancellationToken);
     }
 
     /// <summary>
     /// Asynchronously retrieves an existing server side agent, wrapped as a <see cref="ChatClientAgent"/> using the provided <see cref="AgentsClient"/>.
     /// </summary>
     /// <param name="agentsClient">The <see cref="AgentsClient"/> to create the <see cref="ChatClientAgent"/> with. Cannot be <see langword="null"/>.</param>
-    /// <param name="model">The model to be used by the agent. Cannot be <see langword="null"/> or whitespace.</param>
     /// <param name="name">The name of the server side agent to create a <see cref="ChatClientAgent"/> for. Cannot be <see langword="null"/> or whitespace.</param>
     /// <param name="chatOptions">The default <see cref="ChatOptions"/> to use when interacting with the agent.</param>
     /// <param name="clientFactory">Provides a way to customize the creation of the underlying <see cref="IChatClient"/> used by the agent.</param>
     /// <param name="openAIClientOptions">An optional <see cref="OpenAIClientOptions"/> for configuring the underlying OpenAI client.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations based on the latest version of the named Azure AI Agent.</returns>
-    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/>, <paramref name="model"/>, or <paramref name="name"/> is <see langword="null"/>.</exception>
-    /// <exception cref="ArgumentException">Thrown when <paramref name="model"/> or <paramref name="name"/> is empty or whitespace, or when the agent with the specified name was not found.</exception>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/> or <paramref name="name"/> is <see langword="null"/>.</exception>
+    /// <exception cref="ArgumentException">Thrown when <paramref name="name"/> is empty or whitespace, or when the agent with the specified name was not found.</exception>
     /// <exception cref="InvalidOperationException">The agent with the specified name was not found.</exception>
     public static async Task<ChatClientAgent> GetAIAgentAsync(
         this AgentsClient agentsClient,
-        string model,
         string name,
         ChatOptions? chatOptions = null,
         Func<IChatClient, IChatClient>? clientFactory = null,
@@ -133,30 +122,27 @@ public static class AgentsClientExtensions
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(agentsClient);
-        Throw.IfNullOrWhitespace(model);
         Throw.IfNullOrWhitespace(name);
 
         var agentRecord = (await agentsClient.GetAgentAsync(name, cancellationToken).ConfigureAwait(false)).Value
             ?? throw new InvalidOperationException($"Agent with name '{name}' not found.");
 
-        return GetAIAgent(agentsClient, model, agentRecord, chatOptions, clientFactory, openAIClientOptions, cancellationToken);
+        return GetAIAgent(agentsClient, agentRecord, chatOptions, clientFactory, openAIClientOptions, cancellationToken);
     }
 
     /// <summary>
     /// Gets a runnable agent instance from a <see cref="AgentVersion"/> containing metadata about an Azure AI Agent.
     /// </summary>
     /// <param name="agentsClient">The client used to interact with Azure AI Agents. Cannot be <see langword="null"/>.</param>
-    /// <param name="model">The model to be used by the agent.</param>
     /// <param name="agentRecord">The agent record to be converted. The latest version will be used. Cannot be <see langword="null"/>.</param>
     /// <param name="options">Full set of options to configure the agent.</param>
     /// <param name="clientFactory">Provides a way to customize the creation of the underlying <see cref="IChatClient"/> used by the agent.</param>
     /// <param name="openAIClientOptions">An optional <see cref="OpenAIClientOptions"/> for configuring the underlying OpenAI client.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations based on the latest version of the Azure AI Agent record.</returns>
-    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/>, <paramref name="model"/>, <paramref name="agentRecord"/> or <paramref name="options"/> is <see langword="null"/>.</exception>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/>, <paramref name="agentRecord"/> or <paramref name="options"/> is <see langword="null"/>.</exception>
     public static ChatClientAgent GetAIAgent(
         this AgentsClient agentsClient,
-        string model,
         AgentRecord agentRecord,
         ChatClientAgentOptions? options = null,
         Func<IChatClient, IChatClient>? clientFactory = null,
@@ -164,12 +150,10 @@ public static class AgentsClientExtensions
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(agentsClient);
-        Throw.IfNullOrWhitespace(model);
         Throw.IfNull(agentRecord);
 
         return GetAIAgent(
             agentsClient,
-            model,
             agentRecord.Versions.Latest,
             options,
             clientFactory,
@@ -181,17 +165,15 @@ public static class AgentsClientExtensions
     /// Gets a runnable agent instance from a <see cref="AgentVersion"/> containing metadata about an Azure AI Agent.
     /// </summary>
     /// <param name="agentsClient">The client used to interact with Azure AI Agents. Cannot be <see langword="null"/>.</param>
-    /// <param name="model">The model to be used by the agent.</param>
     /// <param name="agentVersion">The agent version to be converted. Cannot be <see langword="null"/>.</param>
     /// <param name="options">Full set of options to configure the agent.</param>
     /// <param name="clientFactory">Provides a way to customize the creation of the underlying <see cref="IChatClient"/> used by the agent.</param>
     /// <param name="openAIClientOptions">An optional <see cref="OpenAIClientOptions"/> for configuring the underlying OpenAI client.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations based on the provided version of the Azure AI Agent.</returns>
-    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/>, <paramref name="model"/>, <paramref name="agentVersion"/> or <paramref name="options"/> is <see langword="null"/>.</exception>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/> or <paramref name="agentVersion"/> is <see langword="null"/>.</exception>
     public static ChatClientAgent GetAIAgent(
         this AgentsClient agentsClient,
-        string model,
         AgentVersion agentVersion,
         ChatClientAgentOptions? options = null,
         Func<IChatClient, IChatClient>? clientFactory = null,
@@ -199,8 +181,9 @@ public static class AgentsClientExtensions
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(agentsClient);
-        Throw.IfNullOrWhitespace(model);
         Throw.IfNull(agentVersion);
+
+        string model = (agentVersion.Definition as PromptAgentDefinition)?.Model ?? NoOpModel;
         IChatClient chatClient = new AzureAIAgentChatClient(agentsClient, agentVersion, model, openAIClientOptions);
 
         if (clientFactory is not null)
@@ -216,7 +199,7 @@ public static class AgentsClientExtensions
         if (options is null)
         {
             agentOptions = new();
-            agentOptions.Id = GetAgentId(agentVersion);
+            agentOptions.Id = agentVersion.Id;
             agentOptions.Name = agentVersion.Name;
 
             agentOptions.Description = version.Description;
@@ -238,7 +221,7 @@ public static class AgentsClientExtensions
             // When agent options it is used when available otherwise fallback to the agent definition used for the agent record.
             agentOptions = new ChatClientAgentOptions()
             {
-                Id = options.Id ?? GetAgentId(agentVersion),
+                Id = options.Id ?? agentVersion.Id,
                 Name = options.Name ?? agentVersion.Name,
                 Description = options.Description ?? version.Description,
                 Instructions = options.Instructions ?? options.ChatOptions?.Instructions ?? (version.Definition as PromptAgentDefinition)?.Instructions,
@@ -268,7 +251,6 @@ public static class AgentsClientExtensions
     /// Retrieves an existing server side agent, wrapped as a <see cref="ChatClientAgent"/> using the provided <see cref="AgentsClient"/>.
     /// </summary>
     /// <param name="agentsClient">The <see cref="AgentsClient"/> to create the <see cref="ChatClientAgent"/> with.</param>
-    /// <param name="model">The model to be used by the agent.</param>
     /// <param name="name">The ID of the server side agent to create a <see cref="ChatClientAgent"/> for.</param>
     /// <param name="options">Full set of options to configure the agent.</param>
     /// <param name="clientFactory">Provides a way to customize the creation of the underlying <see cref="IChatClient"/> used by the agent.</param>
@@ -279,7 +261,6 @@ public static class AgentsClientExtensions
     /// <exception cref="ArgumentException">Thrown when <paramref name="name"/> is empty or whitespace.</exception>
     public static async Task<ChatClientAgent> GetAIAgentAsync(
         this AgentsClient agentsClient,
-        string model,
         string name,
         ChatClientAgentOptions options,
         Func<IChatClient, IChatClient>? clientFactory = null,
@@ -293,15 +274,15 @@ public static class AgentsClientExtensions
         var agentRecord = await agentsClient.GetAgentAsync(name, cancellationToken).ConfigureAwait(false)
             ?? throw new InvalidOperationException($"Agent with name '{name}' not found.");
 
-        return GetAIAgent(agentsClient, model, agentRecord, options, clientFactory, openAIClientOptions, cancellationToken);
+        return GetAIAgent(agentsClient, agentRecord, options, clientFactory, openAIClientOptions, cancellationToken);
     }
 
     /// <summary>
     /// Creates a new server side agent using the provided <see cref="AgentsClient"/>.
     /// </summary>
     /// <param name="agentsClient">The <see cref="AgentsClient"/> to create the agent with.</param>
-    /// <param name="model">The model to be used by the agent.</param>
     /// <param name="name">The name of the agent.</param>
+    /// <param name="model">The model to be used by the agent.</param>
     /// <param name="instructions">The instructions for the agent.</param>
     /// <param name="description">The description for the agent.</param>
     /// <param name="tools">The tools to be used by the agent.</param>
@@ -318,8 +299,8 @@ public static class AgentsClientExtensions
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations on the newly created agent.</returns>
     public static ChatClientAgent CreateAIAgent(
         this AgentsClient agentsClient,
-        string model,
         string name,
+        string model,
         string? instructions = null,
         string? description = null,
         IList<ResponseTool>? tools = null,
@@ -335,8 +316,8 @@ public static class AgentsClientExtensions
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(agentsClient);
-        Throw.IfNullOrWhitespace(model);
         Throw.IfNullOrWhitespace(name);
+        Throw.IfNullOrWhitespace(model);
 
         var (promptAgentDefinition, versionCreationOptions, chatClientAgentOptions) = CreatePromptAgentDefinitionAndOptions(
             name,
@@ -369,19 +350,16 @@ public static class AgentsClientExtensions
     /// <param name="agentsClient">The client used to manage and interact with AI agents. Cannot be <see langword="null"/>.</param>
     /// <param name="name">The name for the agent.</param>
     /// <param name="agentDefinition">The definition that specifies the configuration and behavior of the agent to create. Cannot be <see langword="null"/>.</param>
-    /// <param name="model">The name of the model to use for the agent. Model must be provided either directly or as part of a <see cref="PromptAgentDefinition.Model"/> specialization property.</param>
     /// <param name="creationOptions">Settings that control the creation of the agent.</param>
     /// <param name="clientFactory">A factory function to customize the creation of the chat client used by the agent.</param>
     /// <param name="openAIClientOptions">An optional <see cref="OpenAIClientOptions"/> for configuring the underlying OpenAI client.</param>
     /// <param name="cancellationToken">A token to monitor for cancellation requests.</param>
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations on the newly created agent.</returns>
     /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/> or <paramref name="agentDefinition"/> is <see langword="null"/>.</exception>
-    /// <exception cref="ArgumentException">Thrown if neither the 'model' parameter nor a model in the agent definition is provided.</exception>
     public static ChatClientAgent CreateAIAgent(
         this AgentsClient agentsClient,
         string name,
         AgentDefinition agentDefinition,
-        string? model = null,
         AgentCreationOptions? creationOptions = null,
         Func<IChatClient, IChatClient>? clientFactory = null,
         OpenAIClientOptions? openAIClientOptions = null,
@@ -391,11 +369,7 @@ public static class AgentsClientExtensions
         Throw.IfNullOrWhitespace(name);
         Throw.IfNull(agentDefinition);
 
-        model ??= (agentDefinition as PromptAgentDefinition)?.Model;
-        if (string.IsNullOrWhiteSpace(model))
-        {
-            throw new ArgumentException("Model must be provided either directly or as part of a PromptAgentDefinition specialization.", nameof(model));
-        }
+        string model = (agentDefinition as PromptAgentDefinition)?.Model ?? NoOpModel;
 
         AgentRecord agentRecord = agentsClient.CreateAgent(name, agentDefinition, creationOptions, cancellationToken);
         IChatClient chatClient = new AzureAIAgentChatClient(agentsClient, agentRecord, model, openAIClientOptions);
@@ -412,25 +386,25 @@ public static class AgentsClientExtensions
     /// Creates a new Prompt AI Agent using the provided <see cref="AgentsClient"/> and options.
     /// </summary>
     /// <param name="agentsClient">The client used to manage and interact with AI agents. Cannot be <see langword="null"/>.</param>
-    /// <param name="model">The name of the model to use for the agent. Cannot be <see langword="null"/> or whitespace.</param>
     /// <param name="options">The options for creating the agent. Cannot be <see langword="null"/>.</param>
+    /// <param name="model">The name of the model to use for the agent. Cannot be <see langword="null"/> or whitespace.</param>
     /// <param name="clientFactory">A factory function to customize the creation of the chat client used by the agent.</param>
     /// <param name="openAIClientOptions">An optional <see cref="OpenAIClientOptions"/> for configuring the underlying OpenAI client.</param>
     /// <param name="cancellationToken">A <see cref="CancellationToken"/> to cancel the operation if needed.</param>
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations on the newly created agent.</returns>
-    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/>, <paramref name="model"/>, or <paramref name="options"/> is <see langword="null"/>.</exception>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/> or <paramref name="options"/> is <see langword="null"/>.</exception>
     /// <exception cref="ArgumentException">Thrown when <paramref name="model"/> is empty or whitespace, or when the agent name is not provided in the options.</exception>
     public static ChatClientAgent CreateAIAgent(
         this AgentsClient agentsClient,
-        string model,
         ChatClientAgentOptions options,
+        string model,
         Func<IChatClient, IChatClient>? clientFactory = null,
         OpenAIClientOptions? openAIClientOptions = null,
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(agentsClient);
-        Throw.IfNullOrWhitespace(model);
         Throw.IfNull(options);
+        Throw.IfNullOrWhitespace(model);
 
         if (string.IsNullOrWhiteSpace(options.Name))
         {
@@ -459,7 +433,7 @@ public static class AgentsClientExtensions
             chatClient = clientFactory(chatClient);
         }
 
-        chatClientAgentOptions.Id = GetAgentId(agentVersion);
+        chatClientAgentOptions.Id = agentVersion.Id;
 
         return new ChatClientAgent(chatClient, chatClientAgentOptions);
     }
@@ -470,7 +444,6 @@ public static class AgentsClientExtensions
     /// </summary>
     /// <param name="agentsClient">The client used to manage and interact with AI agents. Cannot be <see langword="null"/>.</param>
     /// <param name="agentDefinition">The definition that specifies the configuration and behavior of the agent to create. Cannot be <see langword="null"/>.</param>
-    /// <param name="model">The name of the model to use for the agent. If not specified, the model must be provided as part of the agent definition.</param>
     /// <param name="name">The name for the agent.</param>
     /// <param name="agentVersionCreationOptions">Settings that control the creation of the agent.</param>
     /// <param name="clientFactory">A factory function to customize the creation of the chat client used by the agent.</param>
@@ -478,11 +451,9 @@ public static class AgentsClientExtensions
     /// <param name="cancellationToken">A token to monitor for cancellation requests.</param>
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations on the newly created agent.</returns>
     /// <exception cref="ArgumentNullException">Thrown when <paramref name="agentsClient"/> or <paramref name="agentDefinition"/> is <see langword="null"/>.</exception>
-    /// <exception cref="ArgumentException">Thrown if neither the 'model' parameter nor a model in the agent definition is provided.</exception>
     public static async Task<ChatClientAgent> CreateAIAgentAsync(
         this AgentsClient agentsClient,
         AgentDefinition agentDefinition,
-        string? model = null,
         string? name = null,
         AgentVersionCreationOptions? agentVersionCreationOptions = null,
         Func<IChatClient, IChatClient>? clientFactory = null,
@@ -492,11 +463,7 @@ public static class AgentsClientExtensions
         Throw.IfNull(agentsClient);
         Throw.IfNull(agentDefinition);
 
-        model ??= (agentDefinition as PromptAgentDefinition)?.Model;
-        if (string.IsNullOrWhiteSpace(model))
-        {
-            throw new ArgumentException("Model must be provided either directly or as part of a PromptAgentDefinition specialization.", nameof(model));
-        }
+        string model = (agentDefinition as PromptAgentDefinition)?.Model ?? NoOpModel;
 
         AgentVersion agentVersion = await agentsClient.CreateAgentVersionAsync(name, agentDefinition, agentVersionCreationOptions, cancellationToken).ConfigureAwait(false);
         IChatClient chatClient = new AzureAIAgentChatClient(agentsClient, agentVersion, model, openAIClientOptions);
@@ -514,7 +481,7 @@ public static class AgentsClientExtensions
 
         return new ChatClientAgent(chatClient, new ChatClientAgentOptions()
         {
-            Id = GetAgentId(agentVersion),
+            Id = agentVersion.Id,
             Name = name,
             Description = agentVersionCreationOptions?.Description,
             Instructions = (agentDefinition as PromptAgentDefinition)?.Instructions,
@@ -529,8 +496,8 @@ public static class AgentsClientExtensions
     /// Creates a new server side prompt agent using the provided <see cref="AgentsClient"/>.
     /// </summary>
     /// <param name="agentsClient">The <see cref="AgentsClient"/> to create the agent with.</param>
-    /// <param name="model">The model to be used by the agent.</param>
     /// <param name="name">The name of the agent.</param>
+    /// <param name="model">The model to be used by the agent.</param>
     /// <param name="instructions">The instructions for the agent.</param>
     /// <param name="description">The description for the agent.</param>
     /// <param name="tools">The tools to be used by the agent.</param>
@@ -547,8 +514,8 @@ public static class AgentsClientExtensions
     /// <returns>A <see cref="ChatClientAgent"/> instance that can be used to perform operations on the newly created agent.</returns>
     public static async Task<ChatClientAgent> CreateAIAgentAsync(
         this AgentsClient agentsClient,
-        string model,
         string name,
+        string model,
         string? instructions = null,
         string? description = null,
         IList<ResponseTool>? tools = null,
@@ -564,6 +531,7 @@ public static class AgentsClientExtensions
         CancellationToken cancellationToken = default)
     {
         Throw.IfNull(agentsClient);
+        Throw.IfNullOrWhitespace(name);
         Throw.IfNullOrWhitespace(model);
 
         var (promptAgentDefinition, versionCreationOptions, chatClientAgentOptions) = CreatePromptAgentDefinitionAndOptions(name, model, instructions, description, temperature, topP, raiConfig, reasoningOptions, textOptions, tools, structuredInputs, metadata);
@@ -576,13 +544,19 @@ public static class AgentsClientExtensions
             chatClient = clientFactory(chatClient);
         }
 
-        chatClientAgentOptions.Id = GetAgentId(agentVersion);
+        chatClientAgentOptions.Id = agentVersion.Id;
 
         return new ChatClientAgent(chatClient, chatClientAgentOptions);
     }
 
     #region Private
 
+    /// <summary>
+    /// The usage of a no-op model is a necessary change to avoid OpenAIClients to throw exceptions when
+    /// used with Azure AI Agents as the model used is now defined at the agent creation time.
+    /// </summary>
+    private const string NoOpModel = "no-op";
+
     private static (PromptAgentDefinition, AgentVersionCreationOptions?, ChatClientAgentOptions) CreatePromptAgentDefinitionAndOptions(
         string name,
         string model,
@@ -660,9 +634,6 @@ public static class AgentsClientExtensions
         return (promptAgentDefinition, versionCreationOptions, chatClientAgentOptions);
     }
 
-    private static string GetAgentId(AgentVersion agentVersion)
-        => $"{agentVersion.Name}:{agentVersion.Id}";
-
     #endregion
 
     #region Polyfill from MEAI.OpenAI for AITool -> ResponseTool conversion
diff --git a/dotnet/tests/Microsoft.Agents.AI.AzureAIAgents.UnitTests/AgentsClientExtensionsTests.cs b/dotnet/tests/Microsoft.Agents.AI.AzureAIAgents.UnitTests/AgentsClientExtensionsTests.cs
index 793f75dc2d..83869d53c1 100644
--- a/dotnet/tests/Microsoft.Agents.AI.AzureAIAgents.UnitTests/AgentsClientExtensionsTests.cs
+++ b/dotnet/tests/Microsoft.Agents.AI.AzureAIAgents.UnitTests/AgentsClientExtensionsTests.cs
@@ -33,62 +33,11 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            client!.GetAIAgent("model", agentRecord, chatOptions: null));
+            client!.GetAIAgent(agentRecord, chatOptions: null));
 
         Assert.Equal("agentsClient", exception.ParamName);
     }
 
-    /// <summary>
-    /// Verify that GetAIAgent throws ArgumentNullException when model is null.
-    /// </summary>
-    [Fact]
-    public void GetAIAgent_WithAgentRecord_WithNullModel_ThrowsArgumentNullException()
-    {
-        // Arrange
-        var mockClient = new Mock<AgentsClient>();
-        AgentRecord agentRecord = this.CreateTestAgentRecord();
-
-        // Act & Assert
-        var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.GetAIAgent(null!, agentRecord, chatOptions: null));
-
-        Assert.Equal("model", exception.ParamName);
-    }
-
-    /// <summary>
-    /// Verify that GetAIAgent throws ArgumentException when model is empty.
-    /// </summary>
-    [Fact]
-    public void GetAIAgent_WithAgentRecord_WithEmptyModel_ThrowsArgumentException()
-    {
-        // Arrange
-        var mockClient = new Mock<AgentsClient>();
-        AgentRecord agentRecord = this.CreateTestAgentRecord();
-
-        // Act & Assert
-        var exception = Assert.Throws<ArgumentException>(() =>
-            mockClient.Object.GetAIAgent(string.Empty, agentRecord, chatOptions: null));
-
-        Assert.Equal("model", exception.ParamName);
-    }
-
-    /// <summary>
-    /// Verify that GetAIAgent throws ArgumentException when model is whitespace.
-    /// </summary>
-    [Fact]
-    public void GetAIAgent_WithAgentRecord_WithWhitespaceModel_ThrowsArgumentException()
-    {
-        // Arrange
-        var mockClient = new Mock<AgentsClient>();
-        AgentRecord agentRecord = this.CreateTestAgentRecord();
-
-        // Act & Assert
-        var exception = Assert.Throws<ArgumentException>(() =>
-            mockClient.Object.GetAIAgent("   ", agentRecord, chatOptions: null));
-
-        Assert.Equal("model", exception.ParamName);
-    }
-
     /// <summary>
     /// Verify that GetAIAgent throws ArgumentNullException when agentRecord is null.
     /// </summary>
@@ -100,7 +49,7 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.GetAIAgent("model", (AgentRecord)null!, chatOptions: null));
+            mockClient.Object.GetAIAgent((AgentRecord)null!, chatOptions: null));
 
         Assert.Equal("agentRecord", exception.ParamName);
     }
@@ -116,7 +65,7 @@ public sealed class AgentsClientExtensionsTests
         AgentRecord agentRecord = this.CreateTestAgentRecord();
 
         // Act
-        var agent = client.GetAIAgent("test-model", agentRecord, chatOptions: null);
+        var agent = client.GetAIAgent(agentRecord, chatOptions: null);
 
         // Assert
         Assert.NotNull(agent);
@@ -136,7 +85,6 @@ public sealed class AgentsClientExtensionsTests
 
         // Act
         var agent = client.GetAIAgent(
-            "test-model",
             agentRecord,
             chatOptions: null,
             clientFactory: (innerClient) => testChatClient = new TestChatClient(innerClient));
@@ -164,28 +112,11 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            client!.GetAIAgent("model", agentVersion, chatOptions: null));
+            client!.GetAIAgent(agentVersion, chatOptions: null));
 
         Assert.Equal("agentsClient", exception.ParamName);
     }
 
-    /// <summary>
-    /// Verify that GetAIAgent throws ArgumentNullException when model is null.
-    /// </summary>
-    [Fact]
-    public void GetAIAgent_WithAgentVersion_WithNullModel_ThrowsArgumentNullException()
-    {
-        // Arrange
-        var mockClient = new Mock<AgentsClient>();
-        AgentVersion agentVersion = this.CreateTestAgentVersion();
-
-        // Act & Assert
-        var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.GetAIAgent(null!, agentVersion, chatOptions: null));
-
-        Assert.Equal("model", exception.ParamName);
-    }
-
     /// <summary>
     /// Verify that GetAIAgent throws ArgumentNullException when agentVersion is null.
     /// </summary>
@@ -197,7 +128,7 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.GetAIAgent("model", (AgentVersion)null!, chatOptions: null));
+            mockClient.Object.GetAIAgent((AgentVersion)null!, chatOptions: null));
 
         Assert.Equal("agentVersion", exception.ParamName);
     }
@@ -213,7 +144,7 @@ public sealed class AgentsClientExtensionsTests
         AgentVersion agentVersion = this.CreateTestAgentVersion();
 
         // Act
-        var agent = client.GetAIAgent("test-model", agentVersion, chatOptions: null);
+        var agent = client.GetAIAgent(agentVersion, chatOptions: null);
 
         // Assert
         Assert.NotNull(agent);
@@ -233,7 +164,6 @@ public sealed class AgentsClientExtensionsTests
 
         // Act
         var agent = client.GetAIAgent(
-            "test-model",
             agentVersion,
             chatOptions: null,
             clientFactory: (innerClient) => testChatClient = new TestChatClient(innerClient));
@@ -247,7 +177,7 @@ public sealed class AgentsClientExtensionsTests
 
     #endregion
 
-    #region GetAIAgent(AgentsClient, string, string) Tests
+    #region GetAIAgent(AgentsClient, string) Tests
 
     /// <summary>
     /// Verify that GetAIAgent throws ArgumentNullException when agentsClient is null.
@@ -260,27 +190,11 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            client!.GetAIAgent("model", "test-agent", chatOptions: null));
+            client!.GetAIAgent("test-agent", chatOptions: null));
 
         Assert.Equal("agentsClient", exception.ParamName);
     }
 
-    /// <summary>
-    /// Verify that GetAIAgent throws ArgumentNullException when model is null.
-    /// </summary>
-    [Fact]
-    public void GetAIAgent_ByName_WithNullModel_ThrowsArgumentNullException()
-    {
-        // Arrange
-        var mockClient = new Mock<AgentsClient>();
-
-        // Act & Assert
-        var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.GetAIAgent(null!, "test-agent", chatOptions: null));
-
-        Assert.Equal("model", exception.ParamName);
-    }
-
     /// <summary>
     /// Verify that GetAIAgent throws ArgumentNullException when name is null.
     /// </summary>
@@ -292,7 +206,7 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.GetAIAgent("model", (string)null!, chatOptions: null));
+            mockClient.Object.GetAIAgent((string)null!, chatOptions: null));
 
         Assert.Equal("name", exception.ParamName);
     }
@@ -308,7 +222,7 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentException>(() =>
-            mockClient.Object.GetAIAgent("model", string.Empty, chatOptions: null));
+            mockClient.Object.GetAIAgent(string.Empty, chatOptions: null));
 
         Assert.Equal("name", exception.ParamName);
     }
@@ -326,14 +240,14 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<InvalidOperationException>(() =>
-            mockClient.Object.GetAIAgent("model", "non-existent-agent", chatOptions: null));
+            mockClient.Object.GetAIAgent("non-existent-agent", chatOptions: null));
 
         Assert.Contains("not found", exception.Message);
     }
 
     #endregion
 
-    #region GetAIAgentAsync(AgentsClient, string, string) Tests
+    #region GetAIAgentAsync(AgentsClient, string) Tests
 
     /// <summary>
     /// Verify that GetAIAgentAsync throws ArgumentNullException when agentsClient is null.
@@ -346,27 +260,11 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = await Assert.ThrowsAsync<ArgumentNullException>(() =>
-            client!.GetAIAgentAsync("model", "test-agent"));
+            client!.GetAIAgentAsync("test-agent"));
 
         Assert.Equal("agentsClient", exception.ParamName);
     }
 
-    /// <summary>
-    /// Verify that GetAIAgentAsync throws ArgumentNullException when model is null.
-    /// </summary>
-    [Fact]
-    public async Task GetAIAgentAsync_ByName_WithNullModel_ThrowsArgumentNullExceptionAsync()
-    {
-        // Arrange
-        var mockClient = new Mock<AgentsClient>();
-
-        // Act & Assert
-        var exception = await Assert.ThrowsAsync<ArgumentNullException>(() =>
-            mockClient.Object.GetAIAgentAsync(null!, "test-agent"));
-
-        Assert.Equal("model", exception.ParamName);
-    }
-
     /// <summary>
     /// Verify that GetAIAgentAsync throws ArgumentNullException when name is null.
     /// </summary>
@@ -378,7 +276,7 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = await Assert.ThrowsAsync<ArgumentNullException>(() =>
-            mockClient.Object.GetAIAgentAsync("model", null!));
+            mockClient.Object.GetAIAgentAsync(null!));
 
         Assert.Equal("name", exception.ParamName);
     }
@@ -396,14 +294,14 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = await Assert.ThrowsAsync<InvalidOperationException>(() =>
-            mockClient.Object.GetAIAgentAsync("model", "non-existent-agent"));
+            mockClient.Object.GetAIAgentAsync("non-existent-agent"));
 
         Assert.Contains("not found", exception.Message);
     }
 
     #endregion
 
-    #region GetAIAgent(AgentsClient, string, AgentRecord, ChatClientAgentOptions) Tests
+    #region GetAIAgent(AgentsClient, AgentRecord, ChatClientAgentOptions) Tests
 
     /// <summary>
     /// Verify that GetAIAgent with options uses provided options correctly.
@@ -422,7 +320,7 @@ public sealed class AgentsClientExtensionsTests
         };
 
         // Act
-        var agent = client.GetAIAgent("test-model", agentRecord, options);
+        var agent = client.GetAIAgent(agentRecord, options);
 
         // Assert
         Assert.NotNull(agent);
@@ -442,7 +340,7 @@ public sealed class AgentsClientExtensionsTests
         AgentRecord agentRecord = this.CreateTestAgentRecord();
 
         // Act
-        var agent = client.GetAIAgent("test-model", agentRecord, options: null);
+        var agent = client.GetAIAgent(agentRecord, options: null);
 
         // Assert
         Assert.NotNull(agent);
@@ -451,7 +349,7 @@ public sealed class AgentsClientExtensionsTests
 
     #endregion
 
-    #region GetAIAgentAsync(AgentsClient, string, string, ChatClientAgentOptions) Tests
+    #region GetAIAgentAsync(AgentsClient, string, ChatClientAgentOptions) Tests
 
     /// <summary>
     /// Verify that GetAIAgentAsync throws ArgumentNullException when options is null.
@@ -464,7 +362,7 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = await Assert.ThrowsAsync<ArgumentNullException>(() =>
-            mockClient.Object.GetAIAgentAsync("model", "test-agent", (ChatClientAgentOptions)null!));
+            mockClient.Object.GetAIAgentAsync("test-agent", (ChatClientAgentOptions)null!));
 
         Assert.Equal("options", exception.ParamName);
     }
@@ -484,27 +382,11 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            client!.CreateAIAgent("model", "test-agent"));
+            client!.CreateAIAgent("test-agent", "model"));
 
         Assert.Equal("agentsClient", exception.ParamName);
     }
 
-    /// <summary>
-    /// Verify that CreateAIAgent throws ArgumentNullException when model is null.
-    /// </summary>
-    [Fact]
-    public void CreateAIAgent_WithBasicParams_WithNullModel_ThrowsArgumentNullException()
-    {
-        // Arrange
-        var mockClient = new Mock<AgentsClient>();
-
-        // Act & Assert
-        var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.CreateAIAgent(null!, "test-agent"));
-
-        Assert.Equal("model", exception.ParamName);
-    }
-
     /// <summary>
     /// Verify that CreateAIAgent throws ArgumentNullException when name is null.
     /// </summary>
@@ -516,7 +398,7 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.CreateAIAgent("model", (string)null!));
+            mockClient.Object.CreateAIAgent((string)null!, "model"));
 
         Assert.Equal("name", exception.ParamName);
     }
@@ -575,26 +457,9 @@ public sealed class AgentsClientExtensionsTests
         Assert.Equal("agentDefinition", exception.ParamName);
     }
 
-    /// <summary>
-    /// Verify that CreateAIAgent throws ArgumentException when model is not provided.
-    /// </summary>
-    [Fact]
-    public void CreateAIAgent_WithAgentDefinition_WithoutModel_ThrowsArgumentNullException()
-    {
-        // Arrange
-        AgentsClient client = this.CreateTestAgentsClient();
-        var definition = new PromptAgentDefinition("");
-
-        // Act & Assert
-        var exception = Assert.Throws<ArgumentException>(() =>
-            client.CreateAIAgent("test-agent", definition, model: null));
-
-        Assert.Contains("Model must be provided", exception.Message);
-    }
-
     #endregion
 
-    #region CreateAIAgent(AgentsClient, string, ChatClientAgentOptions) Tests
+    #region CreateAIAgent(AgentsClient, ChatClientAgentOptions, string) Tests
 
     /// <summary>
     /// Verify that CreateAIAgent throws ArgumentNullException when agentsClient is null.
@@ -608,11 +473,27 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            client!.CreateAIAgent("model", options));
+            client!.CreateAIAgent(options, "model"));
 
         Assert.Equal("agentsClient", exception.ParamName);
     }
 
+    /// <summary>
+    /// Verify that CreateAIAgent throws ArgumentNullException when options is null.
+    /// </summary>
+    [Fact]
+    public void CreateAIAgent_WithOptions_WithNullOptions_ThrowsArgumentNullException()
+    {
+        // Arrange
+        var mockClient = new Mock<AgentsClient>();
+
+        // Act & Assert
+        var exception = Assert.Throws<ArgumentNullException>(() =>
+            mockClient.Object.CreateAIAgent((ChatClientAgentOptions)null!, "model"));
+
+        Assert.Equal("options", exception.ParamName);
+    }
+
     /// <summary>
     /// Verify that CreateAIAgent throws ArgumentNullException when model is null.
     /// </summary>
@@ -625,27 +506,11 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.CreateAIAgent(null!, options));
+            mockClient.Object.CreateAIAgent(options, null!));
 
         Assert.Equal("model", exception.ParamName);
     }
 
-    /// <summary>
-    /// Verify that CreateAIAgent throws ArgumentNullException when options is null.
-    /// </summary>
-    [Fact]
-    public void CreateAIAgent_WithOptions_WithNullOptions_ThrowsArgumentNullException()
-    {
-        // Arrange
-        var mockClient = new Mock<AgentsClient>();
-
-        // Act & Assert
-        var exception = Assert.Throws<ArgumentNullException>(() =>
-            mockClient.Object.CreateAIAgent("model", (ChatClientAgentOptions)null!));
-
-        Assert.Equal("options", exception.ParamName);
-    }
-
     /// <summary>
     /// Verify that CreateAIAgent throws ArgumentNullException when options.Name is null.
     /// </summary>
@@ -658,7 +523,7 @@ public sealed class AgentsClientExtensionsTests
 
         // Act & Assert
         var exception = Assert.Throws<ArgumentException>(() =>
-            client.CreateAIAgent("test-model", options));
+            client.CreateAIAgent(options, "test-model"));
 
         Assert.Contains("Agent name must be provided", exception.Message);
     }
@@ -700,23 +565,6 @@ public sealed class AgentsClientExtensionsTests
         Assert.Equal("agentDefinition", exception.ParamName);
     }
 
-    /// <summary>
-    /// Verify that CreateAIAgentAsync throws ArgumentException when model is not provided.
-    /// </summary>
-    [Fact]
-    public async Task CreateAIAgentAsync_WithAgentDefinition_WithoutModel_ThrowsExceptionAsync()
-    {
-        // Arrange
-        AgentsClient client = this.CreateTestAgentsClient();
-        var definition = new PromptAgentDefinition("");
-
-        // Act & Assert
-        var exception = await Assert.ThrowsAsync<ArgumentException>(() =>
-            client.CreateAIAgentAsync(definition, model: null));
-
-        Assert.Contains("Model must be provided", exception.Message);
-    }
-
     #endregion
 
     #region Helper Methods