Previews

What’s a preview?

An isolated OpenTofu workspace that exists while a PR is open.

PR opened   → Preview created, tofu apply
PR updated  → Preview updated, tofu apply
PR merged   → Production apply, preview destroyed
PR closed   → Preview destroyed

Isolation

Each preview gets:

• Unique state — previews/pr-42/terraform.tfstate
• Namespaced resources — via {{ environment }} variable

resource "aws_s3_bucket" "data" {
  bucket = "myapp-${var.environment}"
}

PR #42 creates myapp-pr-42. No collision with PR #99 or production.

Lifecycle

PR Event	Yaffle Action
Opened	plan → apply to preview
Pushed	plan → apply to preview
Merged	apply to production → destroy preview
Closed	destroy preview

Outputs

After apply, outputs are available:

In the GitHub check:

Outputs:
  api_url = "https://pr-42.api.example.com"

Via API:

curl https://yaffle.dev/api/previews/pr-42/outputs

In GitHub Actions:

- uses: yaffledev/outputs-action@v1
  with:
    preview: pr-${{ github.event.pull_request.number }}

Preview status

Status	Meaning
pending	Waiting for runner
planning	Running terraform plan
applying	Running terraform apply
ready	Infrastructure is up
failed	Run failed
destroying	Running terraform destroy
destroyed	Cleaned up