Caelus

Astrological ephemeris monorepo. MIT, no Swiss Ephemeris code, no AGPL, no
ephemeris files. Live at ephemengine.com.

Packages

Path	npm	Description
packages/caelus	caelus	TypeScript engine (~97 KB gzipped, zero deps)
packages/caelus-mcp	caelus-mcp	MCP server: charts, transits, synastry, events, eclipses
packages/caelus-delineations-pd	—	Public-domain interpretation corpus + default validation set for interpret()
packages/birth	caelus-birth	Birth time + place → UT (timezone and DST resolution)
packages/wheel	caelus-wheel	React SVG chart wheel, zero runtime deps
apps/web	—	Next.js site: playground, validation, edge /api/chart
caelus-starter	—	Next.js starter app (separate repo)

The Python reference engine and data-fitting pipeline live in python/;
they mint the coefficient data and golden fixtures and are not a runtime
dependency.

Docs

• ARCHITECTURE.md — layout, durability decisions, product strategy
• MCP_SPEC.md — MCP tool contract
• docs/gap-analysis.md — Swiss Ephemeris comparison (closed at 0.5.0)
• docs/agents.md — pitfalls for coding agents building on Caelus
• docs/releasing.md — release process

Quick start

npm install
npm run build
npm test
npm run dev -w web

http://localhost:3000 — live chart in the browser.
Edge API: GET /api/chart?date=…&lat=…&lon=….

Branches

• main — stable releases
• dev — active development