> Meticulous records real user sessions from a web app and replays them against each commit to catch visual regressions.
>
> Full AI-readable docs index (project setup guide + every page as markdown): https://app.meticulous.ai/llms.txt

# Troubleshoot Comparisons Against an Older Commit

## I see "Compared against an older commit" on my PR test run

Meticulous compares your pull request against a test run on its base commit. If that commit has no test run when your
pull request's tests are ready, Meticulous compares against the nearest earlier commit that has one, rather than
waiting.

For example, `main` has four commits, oldest first:

1. `a1f3`: has a test run.
2. `b7c2`: has a test run.
3. `c4e9`: its run was cancelled, so no test run.
4. `d2a8`: your pull request's base commit, still building, so no test run yet.

Meticulous compares your pull request against `b7c2`, the nearest earlier commit with a test run, so changes made in `c4e9` and `d2a8` can show up as differences.

Before approving a difference, check that your pull request could have caused it.

Stacked pull requests can show "Compared against a merge parent" instead: the base is a temporary merge commit GitHub
created, so Meticulous used the tip of the branch the pull request is stacked on.

Seeing this now and then is expected, for example when your pull request branched from a commit whose main-branch build
was still running. If you see it on most pull requests, check the following.

### 1. Meticulous runs on every main-branch commit that can change your app

Meticulous needs to [run on your main branch as well as on pull requests](/docs/faq-and-troubleshooting#branches-must-run-on). If you test
preview deployments, every main-branch commit needs a deployment. Skipping commits that only touch files outside your
app is fine. To skip a commit that touches your app's files but can't change it, label it with
[`ci label-commit --labels not-relevant`](/docs/reference/cli-commands#ci-label-commit).

### 2. Main-branch runs finish

A failed or cancelled main-branch run leaves that commit without a test run. On GitHub Actions, a `concurrency` group
shared by main-branch runs cancels queued runs even without `cancel-in-progress`, so give each non-pull-request run its
own group:

```yaml
concurrency:
  group: meticulous-${{ github.event_name == 'pull_request' && github.ref || github.run_id }}
  cancel-in-progress: true
```

On GitLab, don't mark the main-branch job `interruptible`, so newer pipelines don't cancel it.

### 3. Your workflow matches the latest example

Compare your workflow with the
[example workflow](/docs/github-actions-v2#3-add-a-github-actions-workflow-to-run-your-tests): update the
Meticulous actions to the
[latest release](https://github.com/alwaysmeticulous/report-diffs-action/releases/latest), and include the
`ensure-base` step, which builds a missing base commit alongside your pull request. With other CI providers, use
[`ci prepare`](/docs/how-to/prepare-for-tests).

Once the base commit has a test run, push a new commit or [re-run your tests](/docs/how-to/retry-test-run) to compare against
it.

## Issues / questions?

If you still see this on most pull requests, or would rather your pull requests wait for the base commit's tests, email
[support@meticulous.ai](mailto:support@meticulous.ai) or [book a call with us](https://calendly.com/gabriel-h/meticulous-demo-booking),
and we'll look at your project's setup.