Terraform "Conflicting configuration arguments" in CI

The provider marks certain arguments as mutually exclusive (ConflictsWith). Setting both on one resource -- for example inline rules and a standalone rule resource -- violates that constraint.

What this error means

validate/plan fails with "Conflicting configuration arguments", naming the two arguments. It commonly appears when mixing inline and standalone forms, or two ways of specifying the same thing.

terraform

Error: Conflicting configuration arguments

  on main.tf line 14, in resource "aws_instance" "app":
  14:   subnet_id = aws_subnet.app.id

"subnet_id": conflicts with network_interface

Common causes

Two mutually exclusive arguments set

The schema allows only one of the pair (e.g. subnet_id vs a network_interface block), so setting both conflicts.

Inline and standalone forms mixed

Defining inline rules on a resource while also using a standalone rule resource for the same thing triggers the conflict.

How to fix it

Keep one form, remove the other

Choose either the inline argument or the standalone/alternative form and delete the conflicting one.

main.tf

resource "aws_instance" "app" {
  # use subnet_id OR a network_interface block, not both
  subnet_id = aws_subnet.app.id
}

How to prevent it

Do not mix inline and standalone forms for the same configuration.
Check provider docs for ConflictsWith argument pairs.
Run terraform validate in CI to catch conflicts before apply.