diff --git a/Jenkinsfile.dev b/Jenkinsfile.dev
index 1d8594e..46b063a 100644
--- a/Jenkinsfile.dev
+++ b/Jenkinsfile.dev
@@ -63,8 +63,34 @@ pipeline {
                 bat """
                     C:\\Windows\\System32\\inetsrv\\appcmd stop apppool /apppool.name:%APP_POOL%
                     xcopy /E /Y /I "%PUBLISH_DIR%\\*" "%DEPLOY_DIR%\\"
-                    C:\\Windows\\System32\\inetsrv\\appcmd start apppool /apppool.name:%APP_POOL%
                 """
+                // Patch web.config to set Development environment — must survive every deploy
+                powershell '''
+                    $path = "C:\\inetpub\\wwwroot\\web.config"
+                    $xml = [xml](Get-Content $path)
+                    $aspNetCore = $xml.configuration.location.'system.webServer'.aspNetCore
+
+                    # Ensure environmentVariables element exists
+                    if (-not $aspNetCore.environmentVariables) {
+                        $envVarsNode = $xml.CreateElement("environmentVariables")
+                        $aspNetCore.AppendChild($envVarsNode) | Out-Null
+                    }
+
+                    # Remove existing ASPNETCORE_ENVIRONMENT entry if present
+                    $existing = $aspNetCore.environmentVariables.environmentVariable |
+                        Where-Object { $_.name -eq "ASPNETCORE_ENVIRONMENT" }
+                    if ($existing) { $aspNetCore.environmentVariables.RemoveChild($existing) | Out-Null }
+
+                    # Add fresh entry
+                    $envVar = $xml.CreateElement("environmentVariable")
+                    $envVar.SetAttribute("name", "ASPNETCORE_ENVIRONMENT")
+                    $envVar.SetAttribute("value", "Development")
+                    $aspNetCore.environmentVariables.AppendChild($envVar) | Out-Null
+
+                    $xml.Save($path)
+                    Write-Host "web.config patched: ASPNETCORE_ENVIRONMENT=Development"
+                '''
+                bat 'C:\\Windows\\System32\\inetsrv\\appcmd start apppool /apppool.name:%APP_POOL%'
             }
             post {
                 failure {