Font Lab

Pick the fonts. Fix the words. Your agent does the work.

Font Lab — flipping font directions live on a real running site

Watch the full demo →

Font Lab is a real-time typography and text editor for AI-built sites. Your agent installs it, composes curated font directions Google fonts and distinctive open-foundry faces, and renders them live on your real site. You can toggle between the fonts and pick the one you like. The agent then finishes it up— next/font + Tailwind on Next.js, self-hosted @font-face everywhere else — reversibly.

Most AI-built sites ends up with generic fonts, like Inter or Geist, because the agent just uses defaults. Font Lab brings the human choose from options the agents curates based on some intake questions. It also allows you to edit text to make it sound like you wrote it.

copy-able prompt here: https://www.jack-mcgovern.com/fontlab

Install

Inside your project — use this prompt:

Install font-lab (npx font-lab install) and set it up for me — start whatever needs to run; I shouldn't have to touch the terminal. Ask me a couple of questions, compose font directions for this project, and show them on my real pages: the live panel if you're on my machine, screenshots if you're not. Before you tell me to look, make sure it actually worked — the panel really loaded, or the screenshots really came out. I make the call. Don't pick for me. Then write the code for the one I choose, and stick around — I'll have text fixes as I go.

Works with: Claude Code · Cursor · VS Code · Codex · Windsurf · Gemini CLI For: any framework with a CSS seam — Next.js gets the full live-panel experience; everything else ships through the same engine (see the matrix below).

Install auto-detects which agents you have and wires them all — skill, MCP server, config, each in the right format. On a stack with no seam at all, Font Lab refuses to half-apply and hands you the generated code with a clear reason instead.

Newly registered MCP tools load on the next session reload — but the agent never has to wait: every tool also runs as a one-shot CLI, npx font-lab run <tool> '<json-args>' (same tool table, same JSON out), so the loop starts the moment install finishes. That's also the fallback whenever an MCP server drops mid-session.

Frameworks — what ships where

The taste engine, shippability gate, portable preview, and screenshots work on every stack. What varies is the preview surface and how the pick lands in your code — font-lab analyze prints the exact verdict for your project:

Every auto-ship path is fenced, idempotent, and reversible (font-lab undo). Agents: read capabilities + shipNote from font_lab_analyze — a non-Next stack is a different route through the same loop, never a reason to stop.

Upgrading

Always use upgrade, not bare npm install.

npx font-lab upgrade

Font Lab lives in two places: the npm package and the panel code stamped into your project (app/_fontlab/). A bare npm install font-lab@latest updates the package but leaves the panel on the old version — which shows a "stale version" warning. upgrade moves everything together in one command: package, panel re-stamp, MCP re-pin, and stale-endpoint shutdown.

How it works

1. Ask. Font Lab asks what you're going for — what feeling, how bold a departure, a brand to evoke or avoid — so the directions are tailored to you, not a generic default.
2. Compose. Your agent composes a small set of font directions (display + body + mono, each with a rationale), reaching past the overexposed AI defaults. A built-in anti-generic rubric rejects menus that are all Inter/Geist/Space Grotesk.
3. Pick. You compare them on your own site — screenshots in chat (works on web or phone) or a live flip/mix/compare panel locally. You always make the pick.
4. Ship. The agent writes the real code for your stack — next/font + Tailwind on Next.js; self-hosted @font-face wired through Tailwind's theme, v3 utilities, or your own CSS font variables elsewhere. Every change is reversible.
5. Finish clean. Click done ✓ (or say so) and the agent runs font_lab_finish: the dev-panel scaffolding comes out, and you get a git-verified commit plan — your copy edits and font change with ready-to-run commands, nothing of Font Lab's mixed in. The scaffolding and state are self-ignoring in git the whole session, so git status was never noisy to begin with.

The panel

The Font Lab panel sits on top of your running site — your real pages, your real content — and lets you change fonts and words in real time.

• Flip through directions with arrow keys — see each pairing on your actual content across multiple routes
• Mix roles — heading from one direction, body from another — and save the mix as its own direction
• Before/after — hold B to peek at your current fonts; tap space to snap between your two finalists
• Inspect — hover any text to see its role, typeface, size, and how many elements share it
• Edit words — double-click any text, retype it, and it saves straight to your source files
• Change receipts — see exactly what changed across the page after every edit
• Undo everything — every modification ships with a reversal command
• Done ✓ — one click ends the session cleanly: your agent strips the dev tooling and hands you the exact commit plan

The panel runs headless too: the agent screenshots your site in each direction and shows you the images in chat — a chat-sized hero shot per direction, with the full-page capture behind it. Works on a phone, on the web, anywhere your agent runs.

The live panel is Next-only — but the real-site preview isn't. On every other framework, Font Lab paints your actual running pages in each direction (the same render-first census machinery the panel flips with, injected headlessly — no scaffolding, no source writes; preview fonts cache in self-ignored state, so your git status stays clean until you actually ship). If no dev server is running, the screenshot tool starts your project's own dev command itself — bound to 127.0.0.1, health-checked, stopped after the capture — which is what makes the loop work unattended in cloud/container agents (Claude Code on the web, and friends) where the human can't reach the agent's localhost. With no dev server possible at all, the fallback is the portable preview: a self-contained HTML specimen sheet (fonts embedded, opens offline) on your own palette and copy — clearly labeled as specimen cards, never passed off as your pages.

Honesty

Font Lab's core promise is preview == ship: what you see in the panel is what the codegen writes.

• Guaranteed fidelity for every font the gate admits — or an honest "may render slightly differently" badge when it can't be byte-for-byte.
• Auto-ships only where the stack has a real seam; anywhere else it hands you the generated code with a clear reason rather than guessing. Never a half-applied change — that's the contract.
• Text sourced externally triggers an explicit notice, never a silent edit.
• The human's pick overrides everything.

Contributing & testing

Testers are the point — especially "it did the wrong thing on my repo" reports. The analyzer output is the most useful thing you can include.

• Issue forms — bugs and "support my stack" requests
• CONTRIBUTING.md — code contributions and how to run the tests
• SECURITY.md — security issues

Going deeper

• cli/README.md — the full user guide: install flags, the agent loop, every keyboard shortcut, the CLI reference
• docs/CONCEPT.md — the vision and the core belief
• docs/ARCHITECTURE.md — how the choosing moment works and the selection.json contract
• docs/SHIP-SPEC.md — how a pick becomes real, reversible code
• docs/PRODUCT.md · docs/PANEL-VISION.md — product and brand context

Open source · MIT · Published with npm provenance — every release is traceable to this repo and commit. Built and dogfooded on jack-mcgovern.com.