Pure orchestrator in core, thin React wrapper in editor:
- `core/services/drag-session.ts` — `createDragSession(action, scene,
options)` returns an imperative session with `start / move / commit
/ cancel / dispose / isActive / getDraft`. Pauses history on start,
resumes on terminate. Per-move runs preview → snap → apply, then
cascades dirty marks via the relations resolver (deduped across
ticks). Re-entry guard, idempotent dispose, fires onCommit/onCancel
callbacks. All tested in bun:test — no React needed.
- `editor/src/hooks/use-drag-action.ts` — wraps the session with the
editor's grid-event emitter and an Esc-to-cancel keyboard listener.
Builds a `SceneApi` once via `createSceneApi(useScene)` at module
init. The hook itself is small enough to read top-to-bottom; all
behavior lives in the session.
Tests (13 cases) cover the hard parts: history pause/resume bracket,
explicit cancel restoring all touched nodes, dispose mid-drag, commit
returning false short-circuiting to cancel, snap callback wired in,
re-entry rejected, deduped dirty-mark across multiple move ticks,
hosts cascade from the registry firing in apply.
No callers yet — Phase 2 column and shelf tools are the first
consumers.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
