harness-observability-and-browser

Verify code changes using browser automation and observability signals instead of static inference.

Updated Jun 18, 2026
One-click install
npx skills add https://github.com/zhengguangli/harness-engineering-kit --skill harness-observability-and-browser-zhengguangli
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: harness-observability-and-browser
Source: https://github.com/zhengguangli/harness-engineering-kit/tree/main/skills/harness-observability-and-browser
Command: npx skills add https://github.com/zhengguangli/harness-engineering-kit --skill harness-observability-and-browser-zhengguangli

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve? Agents often claim a fix works by reading code and guessing runtime behavior, producing unverified conclusions. This Skill replaces inference with first-hand evidence: real browser rendering, structured logs, metrics, and traces, so every verification result is backed by machine-checkable proof. ## Core Features & Use Cases - Browser-Driven Verification: Reproduce UI bugs, validate user journeys, and capture before/after screenshots and DOM snapshots using Playwright or Puppeteer, including mobile emulation and network throttling. - Observability Verification: Translate performance and reliability constraints (e.g., P99 latency < 800ms, error rate < 0.1%) into queryable assertions against structured logs, Prometheus metrics, and distributed traces. - Evidence-Backed Acceptance: Enforce machine-checkable acceptance criteria, attach timestamped screenshots and query results to PRs or execution plans, and report capability gaps when tooling is missing. - Use Case: A user reports the login page shows a white screen. The agent drives the page in a headless browser, captures a screenshot with timestamp and URL, finds a console JS error, and reports the evidence to the implementation agent. ## Quick Start Ask the agent to verify that the checkout flow fix actually works by driving the full user journey in a browser and attaching before-and-after screenshots plus API latency metrics as evidence.

Frequently Asked Questions about harness-observability-and-browser

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I verify a UI bug fix with Playwright?▼

Drive the affected page in a headless browser, capture a before snapshot, execute the trigger path, then re-run the same path after the fix and compare screenshots or DOM snapshots. Every screenshot must include a timestamp and page URL to count as valid evidence.

Playwright vs Puppeteer for browser verification?▼

Playwright is recommended because it covers Chrome, Firefox, and Safari engines with auto-wait and built-in device emulation. Puppeteer is lighter but limited to Chrome, making it suitable only for Chrome-specific testing.

How to check P99 latency against a performance budget?▼

Write the constraint as a queryable assertion, such as histogram_quantile(0.99, rate(http_request_duration_seconds_bucket[5m])) in PromQL, then compare the measured value against the threshold. Record the query result as paired expected-versus-actual evidence.

What happens when no browser automation tool is installed?▼

The agent reports the environment capability gap instead of falling back to reading code and guessing UI behavior. It produces a capability gap report with priority, impact scope, and a suggested fix such as running npx playwright install.

Why are free-text logs rejected for verification?▼

Free-text logs cannot be queried or aggregated by field, so error rates and request traces cannot be verified reliably. Verification requires structured JSON logs with timestamp, level, service, and requestId fields.

When should browser verification be skipped?▼

Skip it for pure documentation or configuration changes, changes fully verifiable through static analysis like type checking and unit tests, or backend-only changes with no user-visible UI impact. Observability verification may still apply to backend changes.