Using Kiro CLI Headless Mode to Review Terraform Dependabot PRs at Scale

Reviewing Terraform Dependabot PRs is one of those tasks that's individually easy but collectively exhausting. For a single PR, the routine is simple: read the changelog for the version bump, check for breaking changes, run terraform validate, and maybe run terraform plan against the environment to be sure nothing unexpected happens on apply.

The problem shows up at scale. If you're managing hundreds of Terraform module repositories, each accumulating Dependabot PRs over time, that "simple" routine multiplies into tens or hundreds of near-identical reviews. It's repetitive, it's easy to rush, and it's exactly the kind of work that eats a day without producing much.

Enter Headless Mode

I recently came across Brian Beach's post introducing headless mode in Kiro CLI, and it turned out to be a good fit for this exact problem. If you want the full picture, the official headless mode docs are worth a read too.

The short version: headless mode lets you hand Kiro CLI a single prompt, run it non-interactively, and let it work through the task on its own — no interactive terminal session required. That distinction matters for how I think about scripting in general. Bash or PowerShell are still the right tools for deterministic, repeatable steps — checkout a repo, install a CLI, grep a file. But version-bump review isn't really deterministic. It requires reading a changelog, judging whether a change is breaking, and deciding what "safe to merge" actually means for this specific bump. That's reasoning work, and it's where headless mode complements scripting rather than replacing it.

Getting set up is straightforward:

1. Generate an API key from the Kiro web portal under Settings → API Keys
2. Set it as the KIRO_API_KEY environment variable
3. Run something like:

   kiro-cli chat --no-interactive "Review this PR"

That's it — no browser login, no interactive session, just a prompt in and a response out.

Wiring It Into GitHub Actions

Once headless mode is available, the natural next step is a GitHub Actions workflow that triggers whenever a Terraform Dependabot PR opens. Kiro CLI reviews the changelog, runs terraform init and terraform validate, and reports back whether the bump looks safe to merge as-is or carries risk — a breaking change, a failed validate, whatever it finds.

If you want to optimize further, you can scope Kiro down to just the changelog and diff review, and leave init/validate to a separate, more deterministic step — worth considering if you want tighter control over exactly what Kiro's tool access can touch.

Here's my sample workflow file:
👉 kiro-terraform-dependency-review.yml

What the workflow does, step by step

1. Checkout — pulls full repo history (fetch-depth: 0), needed so the diff step can compare against the base branch
2. Setup Terraform — installs Terraform via hashicorp/setup-terraform, with a slot ready for a private registry token when needed
3. Install Kiro CLI — downloads and installs kiro-cli on the runner
4. Get PR diff — captures a git diff of just the .tf files between the base branch and the PR
5. Run Kiro dependency review — pipes that diff into kiro-cli chat --no-interactive --trust-all-tools, with a prompt instructing Kiro to:
   • Fetch the changelog or release notes for the bumped provider/module and flag anything breaking
   • Run terraform init and report pass/fail
   • Run terraform validate and report pass/fail
   • Return all three in a fixed markdown structure — ## Changelog Summary, ## terraform init, ## terraform validate — with explicit Status: pass/fail lines, so the output is consistent enough to parse later
6. Clean the output — strips ANSI escape codes and trims everything before the first ## Changelog Summary heading, so tool-invocation logs don't leak into the PR comment
7. Check review status — greps the cleaned report for Status: fail and sets a flag
8. Post the review as a PR comment — with a header showing ⚠️ Issues Found or ✅ Checks Passed
9. Request changes if checks failed — automatically submits a GitHub "Request Changes" review when something's wrong
10. Fail the job if checks failed — exits non-zero, so this can be wired up as a required status check and actually gate merges

Seeing It in Action

The result: Dependabot opens a PR, Kiro reads the diff, pulls the real changelog, runs the actual Terraform commands, and reports back — automatically, on every single PR, without me touching it.

It's already caught a real compatibility conflict in testing — a module bump that required a newer AWS provider than the repo was pinned to, which terraform init correctly failed on before anything got merged.

Now I've got Kiro reviewing Dependabot PRs across my Terraform repos and telling me, up front, whether they're safe to merge — which is exactly the kind of repetitive-but-judgment-requiring work I wanted to get off my plate.

Cheers!