vlmkit

Deterministic verification toolkit for frontend work: markup gates (broken-page scan, copy fidelity, responsive boundaries, keyboard operability, scripted flows), visual regression over time, design audits, and repair tools. Built for humans and coding agents alike — every failing gate prints a machine-parsable fix list. Everything is key-free unless marked [key].

Requires Node 24+.

Quickstart — visual analysis with zero context

npm install -D @mizchi/vlmkit
npx playwright install chromium          # once

# 1. find concrete visual defects on the page you're working on
#    (no reference, no config, no API key — 3 viewports at once)
npx vlmkit check integrity http://localhost:3000/
#    -> verdict: DEFECTS … [page-overflow-x] @768: … main > p (right edge 924px)
#                          [text-collision] @1280: "Total: €1,240" overlaps "Refunds: €80"
#    fix what it names, re-run until: verdict: CLEAN

#    long-polling page: choose an earlier navigation milestone
npx vlmkit check integrity http://localhost:3000/ --wait-until domcontentloaded

# 2. track what your edits change visually (1st run = baseline, then diffs)
npx vlmkit snapshot http://localhost:3000/ --output .vlmkit/snapshots
#    -> desktop 13.11% … mobile 6.57% + diff heatmaps next to the report
#    intended? npx vlmkit snapshot approve --output .vlmkit/snapshots

From there: check copy --manifest (exact copy), check breakpoints --sweep (responsive boundaries), check interactions (keyboard operability), verify markup --target design.png (match a design) — the full task-routing table, done-condition recipes, and agent integration (MCP server + markup-assist skill) live in docs/markup-assist.md.

Setup

npm install -D @mizchi/vlmkit     # or -g
npx playwright install chromium   # once

vlmkit declares playwright as a peer and @playwright/test as an optional peer, reusing the versions already selected by the project instead of installing a second browser build.

Coding agents (MCP) — .mcp.json: { "mcpServers": { "vlmkit": { "command": "npx", "args": ["-y", "@mizchi/vlmkit", "mcp"] } } }
Agent skill — install the automatic vlmkit router once with APM or the open skills CLI (commands below), then ask for the result in natural language.
API keys — only for [key] features (heal markup, check copy --vlm, fix-loop): OPENROUTER_API_KEY / GEMINI_API_KEY / ANTHROPIC_API_KEY.
Snapshot / CI config — vlmkit.config.json (routes, thresholds) via vlmkit workflow init.

Full setup detail: docs/configuration.md.

Install agent skills

Recommended: install the vlmkit skill package once. You do not choose a specialized skill; the agent classifies each frontend request, loads the matching bundled workflow, runs its deterministic gates, fixes failures, and reruns to green.

# Install or update APM (macOS / Linux)
curl -sSL https://aka.ms/apm-unix | sh

# Install vlmkit with APM
apm install mizchi/vlmkit

# Or install with the skills CLI (APM is not required)
npx skills add mizchi/vlmkit

The APM bootstrap above is the official recommended installer and resolves the latest binary for the current platform. It avoids depending on a stale package-manager formula.

Then ask naturally: “implement this mock,” “check this page's responsive and keyboard behavior,” or “turn this story into stable Playwright tests.” There is no skill-selection step in the normal workflow. On first use, the agent detects the repository's package manager, reuses or adds @mizchi/vlmkit locally, and installs Chromium only if a selected gate reports it missing.

Both installers expose one visible vlmkit skill. The 11 specialized workflows are internal resources bundled under that entry, so the agent selects them without adding 11 separate skills or copying the vlmkit source repository.

See the agent skill catalog for all 11 specialized skills, grouped by general verification, UI creation, test generation, comparison and monitoring, and evaluation and hardening.

When to use what

vlmkit --help prints this same map. Everything is key-free unless marked [key].

You want to…	Reach for
Check the page you just wrote/edited, no reference	`check integrity` (broken-page scan, 3 viewports) · `check copy --manifest` (copy present, visibly, verbatim) · `check layout --contract` · `scan scroll` / `scan handlers`
Verify behavior, not pixels	`check breakpoints --sweep` · `check interactions` · `check scroll` / `check animation` · `verify flow --flow`
Match a target design	`verify markup --target` (done verdict + fix list) · `build page` / `build component` · `scan mock` (normalize @2x exports)
Track changes over time (VRT)	`snapshot` (baseline → per-viewport diff → `snapshot approve`) · `watch` · `diff-pr` · `baseline`
Compare two versions	`diff html\|png\|elements` · `migration compare` · `check equivalence --region`
Audit design quality	`check tokens\|theme\|palette` · `check design` (is the page consistent with itself — one button style or six) · `check a11y contrast\|touch\|focus` · `check perf` · `check drift` · `stress i18n\|media`
Vet an image asset before it enters a slot	`check asset --slot --expect-transparent --against-bg --page-palette`
Repair	`heal selector` (dead selector) · `heal markup` `[key]` (LLM auto-fix from a kickback)
Run gates over a whole site	`batch --gate "check integrity" "routes/*/.html"` (parallel, `--shard i/n`, per-job timing) · `gates run` (same, from one reviewed config)
Audit what has been silenced	`gates suppressions` — every suppression with reason, owner, expiry; expired ones stop applying
Wire into agents / pipelines	`mcp` (gate tools over stdio) · `contract` · `workflow` · `markup-loop` · `api` · `bench` · `skill`

Task-routing recipes and done-condition sets: docs/markup-assist.md.

Documentation

Doc	Contents
`docs/introduce.md`	What is vlmkit? — narrative introduction assuming zero context
`docs/markup-assist.md`	Task-routing guide: which gate for which job, done-condition recipes, anti-gaming rules
`docs/cli-reference.md`	Complete command reference: all groups, examples, workflow/API/HTTP, architecture, project structure
`docs/configuration.md`	Install, MCP/skill setup, environment variables, snapshot/CI config, agent skills catalog
`packages/vlmkit-mcp/README.md`	MCP tool table
`docs/knowledge.md` · `docs/reports/`	Accumulated evaluation findings and dated experiment reports
`CHANGELOG.md`	Release notes, including the 0.4.x → current command mapping

License

MIT