macOS · Apple Silicon · v1.0

Diff and version your LLM prompt templates the way git versions code.

A local-first macOS app for AI engineers. Auto-snapshots every save. Visual line + token diff. Side-by-side “test the diff” against Claude and GPT — using your own API keys. Prompts never leave your Mac.

Download for macOS · 24 MB Watch 60-second demo

14-day free trial · no card· $59 pay-once · lifetime V1 updates· macOS 14+

first-touch-reply.prompt.md · diff #21 ↔ #23

  # Reply rules  1. Acknowledge the issue in one sentence.  2. State next steps concretely.- 3. Stay polite at all times.+ 3. Name team owner and ETA in business days if not resolved.  4. Sign off with first name only. + # Forbidden+ - “I understand your frustration”+ - “We apologize for any inconvenience”+ - Any sentence longer than ~25 words   # Output- Plain text. No markdown.+ Plain text. No markdown. ≤ 140 words.

Six features · zero bloat

Everything you need. Nothing you’ll never use.

SchemaGhost ships exactly six things, all polished. No team sync, no cloud, no eval harness — yet. We picked the smallest knife that cuts the wire.

Project browser

Sidebar of projects (folders) → templates. Search across everything. Right-click rename, duplicate, reveal in Finder, export.

Markdown editor

Frontmatter as a key/value form (or raw YAML). Body in JetBrains Mono with variable highlighting and live token counts.

Auto version history

Every save snapshots in the background. Inspector lists snapshots with diff badges, restore in one click.

Visual diff

Two-up side-by-side. Line-level + token-level highlight. Compare any two snapshots, body-only or with frontmatter.

Test the diff

Run both versions against your test input via Anthropic + OpenAI. Streaming outputs side-by-side. Latency, tokens, $ estimate.

Export bundle

One click → JSON + YAML zip with frontmatter, body, snapshots, README. Engineering-handoff ready.

Pricing

Pay once. Yours forever.

No subscription. No usage cap. No “seats.” Lifetime updates on V1. We’ll charge again if and when V2 ships — your V1 license keeps working.

SchemaGhost

$59· pay once

All 6 features
14-day free trial
Lifetime V1 updates
Local-only · no telemetry

Get SchemaGhost

Best value · bundle

SchemaGhost + Manifesto

$88· save $10

SchemaGhost · prompt diff & version
Manifesto · operator’s writing companion
Both lifetime updates
One purchase, two apps

Get the bundle

Bring SchemaGhost + Manifesto into your workflow.

Two Lumen Labs apps for indie engineers who ship. Both local-first, both pay-once. Save $10 with the bundle.

Save $10 →

Questions

The honest answers.

Do my prompts leave my machine?

No. Prompts and snapshots live on disk in your chosen folder. The only outbound traffic is to Anthropic / OpenAI when you press “Run test” — and that uses your own API keys.

Where are my API keys stored?

macOS Keychain. Service id works.lumenlabs.schemaghost.apikeys. Never written to disk or UserDefaults.

Does it work with my existing git repo?

Yes. Point the root folder at a git-tracked directory. Auto-snapshots go to .schemaghost/snapshots/ — gitignore that and you keep both histories.

Why no team sync?

Because the V1 commitment is small and shippable. Use git: commit the folder, push, teammate pulls. Native sync is on the roadmap, not in V1.

Will it support Windows / Linux?

Not in V1. macOS-native gets us the fastest, most polished editor experience. We’ll revisit if demand warrants.

What’s the refund policy?

14-day free trial covers it. If you bought and changed your mind in the first 14 days after purchase, email us — we’ll refund.