# ADR-0006 — Selector ownership split (types in engine, algorithms in anchor)

- Status: proposed
- Date: 2026-05-24
- Workplan: CE-WP-0001-T07 (stub); echoes `wiki/SharedContracts.md` §8

## Context

The original sister-repo INTENT files had overlapping ownership claims for
`Selector`: `citation-engine` listed it as an owned domain type, while
`evidence-anchor`'s scope claimed "selector type definitions related to
anchoring". This was resolved on 2026-05-24 in `wiki/SharedContracts.md` §8:
type *interfaces* live in engine (`src/shared/selector.ts`), creation and
resolution *algorithms* live in anchor.

This ADR makes the split formal so that future code reviews have a written
answer when somebody proposes moving the types into anchor or moving the
algorithms into shared.

## Options

- **A. Status quo: types in `shared/`, algorithms in `anchor/`** *(default)*
  - Pros: anchor depends on shared (allowed by DependencyMap §4); type
    consumers (binder, work) never have to import anchor.
  - Cons: tiny risk of types drifting out of sync with what anchor can
    actually produce.

- **B. Co-locate types and algorithms in `anchor/`**
  - Pros: one home for everything selector-related.
  - Cons: any partition that mentions a `Selector` type (which is most of
    them) would have to import from `anchor/`. Breaks the
    "shared has no internal imports" invariant of DependencyMap §4.

- **C. Split selector kinds: text-quote in shared, PDF-rect in anchor**
  - Pros: only adapter-specific selectors leave shared.
  - Cons: forces a discriminated union spanning two packages — type
    narrowing becomes painful for consumers.

## Decision

(blank — option A is the working assumption codified in SharedContracts.md;
fill this in if a future use case challenges it.)

## Consequences

(blank)