diff --git a/README.md b/README.md
index f8604a2051..4f07a38369 100644
--- a/README.md
+++ b/README.md
@@ -131,7 +131,7 @@ using Azure.Identity;
 using Microsoft.Agents.AI;
 
 var endpoint = Environment.GetEnvironmentVariable("AZURE_AI_PROJECT_ENDPOINT") ?? throw new InvalidOperationException("AZURE_AI_PROJECT_ENDPOINT is not set.");
-var deploymentName = Environment.GetEnvironmentVariable("AZURE_AI_MODEL_DEPLOYMENT_NAME") ?? "gpt-5.3-mini";
+var deploymentName = Environment.GetEnvironmentVariable("AZURE_AI_MODEL_DEPLOYMENT_NAME") ?? "gpt-5.4-mini";
 
 var agent = new AIProjectClient(new Uri(endpoint), new DefaultAzureCredential())
     .AsAIAgent(model: deploymentName, name: "HaikuBot", instructions: "You are an upbeat assistant that writes beautifully.");