How to fix Error: Unsupported argument - An argument named X is not expected here in Terraform

Use terraform validate to get a detailed error message that includes the line number and argument name:

terraform validate

This will show you exactly which argument is unsupported and at what location in your configuration.

Carefully review the argument name in your HCL file. Common mistakes include:
- Snake_case vs camelCase confusion
- Missing underscores
- Extra characters

Compare your argument against the official Terraform provider documentation for that resource.

Check the Terraform provider documentation to confirm the argument exists for the specific resource type you're using. For example:

# Visit the provider registry
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/instance

Search the page for your argument name to confirm it's supported by this resource.

Some configurations require nested block syntax instead of simple arguments:

# Wrong - using argument syntax
resource "aws_instance" "example" {
  tags = { Name = "test" }
}

# Correct - using block syntax
resource "aws_instance" "example" {
  tags {
    Name = "test"
  }
}

Refer to the documentation to determine if your argument needs block syntax.

Update the provider version in your terraform block and reinitialize:

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

Then run:

terraform init -upgrade
terraform validate

If you recently upgraded your provider, the argument may have been removed or renamed. Check the changelog:

# Visit the provider releases page
https://registry.terraform.io/providers/hashicorp/aws/latest

Look for deprecation notices or breaking changes that mention your argument. Use the suggested replacement if provided.