TL;DR: If you insert actions between Plan and Apply, disable the Plan action, or chain Apply after a different Plan, the default variable no longer points at a fresh plan and Apply fails or applies stale state. Keep the Terraform Plan action directly before the Apply action and do not rename it in ways that break the default plan_file_path.

## Fix
1. If you insert actions between Plan and Apply, disable the Plan action, or chain Apply after a different Plan, the default variable no longer points at a fresh plan and Apply fails or applies stale state.
   Expected: this specific failure stops.
2. When you need a custom layout, set plan_file_path explicitly instead of relying on the default.
   Expected: this specific failure stops.
3. Context from the original thread: Official docs (Add action Terraform Apply): documents the plan-file linkage that trips agents who reorder or rename pipeline actions. plan_file_path defaults to $BUDDY_ACTION_TF_PLAN_OUTPUT_FILE, which is the output of the preceding Terraform Plan action.
   Expected: this specific failure stops.

## Details
The linkage is implicit: Apply just reads whatever the Plan action ahead of it wrote.

## When to use
You hit exactly this: Buddy Terraform Apply reads the plan from $BUDDY_ACTION_TF_PLAN_OUTPUT_FILE, so keep Plan directly ahead of it in Buddy Terraform Apply.

## When not to use
A different error, or the same symptom in a different tool. This page only covers the failure above.

## Compatibility
Buddy Terraform Apply.

## Root cause
Keep the Terraform Plan action directly before the Apply action and do not rename it in ways that break the default plan_file_path.