ADR-0002 — Rust first, TypeScript behind traits

Status: accepted

Context

Mature text-editing (CodeMirror), WYSIWYG (Milkdown/ProseMirror) and terminal (xterm.js) components exist in TypeScript and have no Rust equivalents of comparable quality today. The brief permits them if they are modular and replaceable.

Decision

Allow exactly these TS packages, each in its own folder under packages/js/, built to one bundle, driven through a Rust trait (CodeEditorBackend, RichTextBackend, TerminalBackend) with a documented message protocol. JS holds no application state and no language knowledge (ADR-0008 Rust owns the document, JS is a view). Everything else — grid, graph view, flow editor, Typst — is Rust.

Consequences

• Replacement is a feature flag flip plus deleting a folder; the PROTOCOL.md is the acceptance test.
• A JSON hop per keystroke; acceptable (VS Code’s extension host and Zed’s remote mode pay the same).
• Bundles stay small because languages/LSP come from Rust.
• Keeps the desktop app in a webview until all three are replaced.