# Stop letting your coding agent claim "pixel-perfect". Make it prove 97.49%. > Source: > Published: 2026-07-25 09:31:44+00:00 Your coding agent edits a component, runs the build, and reports the UI is now "pixel-perfect." It never opened a browser. It's guessing. I got tired of that, so I built [hwatu](https://github.com/hongnoul/hwatu), a browser designed specifically for the agent verification loop. ``` hwatu --headless http://localhost:3000 # open, no focus steal hwatu wait-load # block until loaded hwatu eval 'document.title' # DOM-level checks hwatu shot /tmp/check.png # screenshot hwatu diff --id 1 --baseline before.png # pixel diff: 97.49% match + heatmap hwatu close 1 ``` The whole loop, screenshot included, runs in about 87 ms on my laptop. Cheap enough that the agent can verify after every edit instead of claiming success blind. `webkitgtk-6.0` . No 170 MB download per project.`hwatu mcp` ), plain CLI, and a 1-line JSON socket. Works with Claude Code, Cursor, Jcode, or any harness.Every benchmark in the repo was measured on real runs with scripts you can rerun: window spawn medians of 13-16 ms, ~87 ms full verification loop, memory measured via PSS across all WebKit child processes. Methodology in [docs/benchmarks.md](https://github.com/hongnoul/hwatu/blob/main/docs/benchmarks.md). ``` curl -fsSL https://raw.githubusercontent.com/hongnoul/hwatu/main/scripts/install.sh | bash hwatu setup # detects Claude Code, Cursor, Jcode, or generic MCP ``` MIT licensed. Linux (WebKitGTK). Feedback and issues welcome: [https://github.com/hongnoul/hwatu](https://github.com/hongnoul/hwatu)