ADR-0008 — Rust owns the document; JS is a view

Status: accepted

Context

If CodeMirror’s EditorState were the source of truth, replacing CodeMirror would mean rewriting document handling, undo, LSP sync and link extraction.

Decision

The document (ropey::Rope, version, undo) lives in Rust. Backends receive text + decorations and emit edits. Same for the markdown block tree and the terminal grid.

Consequences

• Backend swap touches one module.
• Two copies of the text (Rust + JS) — memory cost acceptable; JS applies edits optimistically and Rust reconciles.
• Enables headless operations (agents editing files with no editor open) trivially.