Architecture

Rust/WASM kernel ─── geometry, constraints, ECS world, event store, commands
       │
       │  JSON commands and events across the wasm-bindgen bridge
       │
TypeScript/Svelte ── Three.js renderer, UI, snapping, command line, file I/O
       │
MCP server ───────── typed tools that map onto the same kernel commands

The seven rules

Every change is reviewed against these. They are what make the rest possible.

1. Every operation is a command. Drawing a line is a command object, whether it comes from a toolbar click, a shortcut, the command line, an API call or an agent. No logic hides in UI event handlers.
2. Event-sourced state. Every change appends an immutable event; current state is the replay of the log. Undo, redo, audit trail and replay all fall out of this.
3. ECS data model. An entity is an ID, components are plain data, systems query components. No class hierarchies, so new kinds of entity add components instead of rewriting the core.
4. Additive expansion. New capabilities arrive as new components, commands, renderers and parsers plugged into the existing world, event store and command system. The core is extended, not restructured.
5. Rust/WASM for computation, TypeScript for interaction. Geometry, spatial queries and constraint solving live in Rust; UI and rendering orchestration live in TypeScript and Svelte. The boundary is the wasm-bindgen bridge.
6. AI agents are first-class users. An operation’s tool schema is defined together with the operation: a name, typed parameters, a typed result, callable without any GUI.
7. Research before building. Check for a proven open-source library first; build custom only where there is a real gap.

Packages

Package	Language	Role
packages/kernel	Rust → WASM	ECS world (hecs), geometry, constraints, hash-chained event store, 100+ commands
packages/renderer	TypeScript	Three.js 2D rendering with instancing
packages/file-io	TypeScript	DXF import/export, OPFS persistence
packages/core	TypeScript	Shared types across the boundary
packages/mcp	TypeScript	MCP server and tool-definitions.ts
packages/logger	TypeScript	Structured logging
packages/app	Svelte 5 / SvelteKit	The application shell, command line, panels

Where the detail lives

The full set of architecture notes, from geometric robustness to the WASM boundary, is in docs/architecture/ in the repository. Product decisions are logged in DECISIONS.md.