Meticulous Simulate And Diff

Runs a Meticulous session replay against a live URL and tells you what broke visually. You give it a session ID and optionally a base replay to diff against. With a base, it compares screenshots pixel by pixel and diffs the HTML snapshots so you can see both what changed visually and which DOM elements are responsible. Without a base it just captures screenshots for manual inspection. The HTML diff analysis is smart: it pulls the full page DOM from metadata files and highlights class changes and structural shifts, which usually map directly to the components you changed. Good for catching regressions before you push, especially if you're tweaking styles or layout and want to know exactly which routes got affected.

skills.sh installs: 8.9K
GitHub stars: 10
last updated: Aug 21, 2026

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Install

$ npx -y skills add alwaysmeticulous/skills --skill meticulous-simulate-and-diff --agent claude-code

Installs into .claude/skills of the current project.

Files

Simulate a session and analyze diffs

This skill covers running a single simulation and interpreting the results. For the simulate command's full option reference see the meticulous-cli skill's simulate reference.

Before starting, run the meticulous-cli-update skill to ensure the Meticulous CLI and skills are up to date — unless it has already run earlier in this conversation, in which case skip it.

Prerequisites

A sessionId to replay
An appUrl (local dev server, or leave blank to use the original recorded URL)
Optionally: a baseReplayId — the ID of a prior replay to diff screenshots against. Without this, screenshots are stored but not compared.

If you don't have a baseReplayId, you can find one from a downloaded test run:

meticulous download test-run --testRunId=latest
# Then inspect ~/.meticulous/test-runs/<testRunId>/coverage.json
# or check the testCases[].replayId fields

Step 1 — Run the simulation

With a base replay (diff mode)

meticulous simulate \
  --sessionId=<sessionId> \
  --appUrl=<url> \
  --baseReplayId=<baseReplayId> \
  --headless

SKILL.md on GitHub

Details

Repository: github.com/alwaysmeticulous/skills
Categories: Frontend Development, Git & Pull Requests, Design & UI/UX
First seen: Jul 14, 2026

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