Detect frontend performance regressions

Compare page-load and interaction timing by release, browser, and route so frontend regressions are visible beside errors.

Updated · published

markdown for agents →

difficulty intermediate · time to value 5 minutes · execution on demand

Start from this

Compare frontend performance for the current release versus the previous release. Show routes with worse p75 load time or interaction latency.

Why this matters

Some deploys do not throw errors. They just make checkout feel slower or the docs app sluggish. This workflow catches those regressions as product-impacting incidents.

What you get

  • Routes whose p75 or p95 performance regressed
  • Browser and release segments
  • A short list of likely product surfaces affected
  • Follow-up queries for specific pages

Walk through it

You

Did the latest frontend release slow anything down?

Agent

I’ll compare web_vital timing by route and release.

Endpoint: POST /v1/projects/:project_id/analytics/query
Exact shape: /v1/openapi.json?path=%2Fv1%2Fprojects%2F%7Bproject_id%7D%2Fanalytics%2Fquery&method=post
Custom HogQL goes in the OpenAPI-defined `query` field.
Concept fields:
  query: "SELECT properties.route AS route, properties.metric AS metric, properties.release AS release, properties.browser AS browser, quantile(0.75)(toFloat(properties.value_ms)) AS p75_ms, quantile(0.95)(toFloat(properties.value_ms)) AS p95_ms, count() AS samples FROM events WHERE event = 'web_vital' AND timestamp > now() - INTERVAL 7 DAY GROUP BY route, metric, release, browser ORDER BY p95_ms DESC LIMIT 50"

The output

The agent returns the routes and browser segments that worsened, with enough sample size to be credible. It should call out low-sample rows instead of overclaiming.

Setting it up

Post web-vital or page timing events from the browser with AGENTRY_PUBLIC_API_KEY auth. Include release and route template.

Variations

  • “Only check checkout routes.”
  • “Compare Chrome mobile against desktop.”
  • “Publish this as a release readiness dashboard.”

Adapt this workflow in your own agent.

Ask your agent to map the starter prompt to your saved signal map, live events, and the current HTTP API before answering.

Agentry gives coding agents production context from errors, product analytics, and deploys through one HTTP API. Fetch and read https://agentry.sh/install.md completely, then install Agentry's full first-time telemetry baseline in this repository. I authorize device-code login, saving the owner key only to ~/.agentry/credentials.json, creating one Agentry project for this repository, and read-only inspection of shipped source plus hidden CI/provider configuration. Deeply analyze the product's business logic and complete value flow before choosing telemetry. Save the complete source-backed plan and show me its exact contents and hash. Until I explicitly approve that plan or request a replacement, do not edit app/CI source, place runtime/CI credentials, commit, exercise product traffic, start proof, push, or deploy. After approval, I authorize only the reviewed targets: place the required scoped browser/server/CI credentials through the established environment or secret mechanism, preserve existing telemetry, implement and test the baseline, commit it, push that reviewed commit when the shipped CI/provider path requires it, exercise safe proof paths with test/non-customer data, and perform one deployment through the reviewed shipped CI/provider path. Ask first if proof would charge money, contact a third party, change real customer data, or require new external access. After the plan is saved, immediately before every onboarding state-changing POST, GET current onboarding state, perform only its single returned next_action, then read state again; do not batch or infer later stages. Continue until status is verified, installation_complete is true, and next_action is null. Keep all secrets, source snapshots, proof markers, and scratch files outside the repository.

+ Full access
5.5 Extra High
  1. 1. Open your repo in Codex, Claude Code, Cursor etc.
  2. 2. Paste the install prompt.
  3. 3. Your agent reads the install doc and shows you an implementation plan for approval.