DEVOPS

Gate Vercel production promote on Lighthouse budget regression

When a Vercel deployment finishes building, runs synthetic Lighthouse checks against the preview URL and blocks the promote-to-production if performance, LCP, or bundle size…

CategoryDevOps
Enginesim
Difficultyintermediate
Triggerwebhook
Steps6
Setup~15 min

How it runs

The automated pipeline, trigger to output.

  • TriggerVercel deployment.succeeded webhookVercelVercel
  • LogicFilter to preview builds in READY state
  • ActionRun synthetic Lighthouse audit on preview URLVercelVercel
  • LogicCompare score, LCP, transfer size to baseline budgets
  • ActionPromote to production or cancel the promoteVercelVercel
  • OutputPost pass/fail metric diff to SlackSlack

What it does

Intercepts every successful Vercel preview build, runs a synthetic Lighthouse audit against the generated preview URL, and compares the scores to the production baseline budgets you set (performance score, LCP, total transfer size). If any metric regresses past its threshold, the workflow cancels the production promotion and posts the failing diff to Slack so nothing ships blind.

When to use it

Use it on customer-facing apps where a slow deploy is a real incident. It catches the regression at the preview stage, before a Chairman or engineer clicks promote, instead of after users feel it.

How it works

  1. 1A Vercel `deployment.succeeded` webhook fires for a new preview build.
  2. 2A filter confirms the target is `preview` (not already production) and the build state is READY.
  3. 3A synthetic check hits the preview URL and pulls Lighthouse performance score, LCP, and transfer size.
  4. 4A branch compares each metric to the stored baseline budget.
  5. 5If within budget, the deployment is promoted to production via the Vercel API; if not, the promote is cancelled.
  6. 6The pass or fail verdict, with the metric diff, is posted to the team Slack channel.

Set it up

What you configure once, before turning it on.

  1. 1
    Connect VercelDeploys, runtime logs, analytics.
  2. 2
    Connect SlackChannels, DMs, threads, mentions.
  3. 3
    Set each agent's modelWe leave models unset so you pick the tier — fast + cheap, or top-quality.
  4. 4
    Tune it to your dataEdit the prompts, filters, and field mappings so it matches how your team works.
  5. 5
    Test, then turn it onRun once against a sample, confirm the output, then enable the trigger.

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