# m6p3 — Full Sort Mode Coverage + Live Content + Engagement Filters (✅ COMPLETE 2026-02-23)

Phase spec and acceptance criteria: [ROADMAP · Milestone 6 · Phase 3](../ROADMAP.md).
Milestone index: [README.md](README.md). Backfilled record.

## What shipped

1. **The sort surface completed** (`tidal/src/ranking/profile.rs`, `Sort` enum).
   M6 added `AlphabeticalAsc`, `AlphabeticalDesc`, `Shortest`, `Longest`,
   `MostCommented { window }`, `MostShared { window }`, `LiveViewerCount`, and
   `DateSaved` alongside the pre-existing `Hot`, `Trending`, `Rising`,
   `Controversial`, `HiddenGems`, `Shuffle`, `New`, `TopWindow`, `MostViewed`,
   `MostLiked`, `MostFollowed`, `CreatorEngagementRate`, and `Ann`. Window
   parameterization is what lets ~20 variants cover the 27 sort modes in
   [USE_CASES.md](../../../USE_CASES.md) Appendix B.
2. **Metadata-driven ordering.** Alphabetical sorts read the `title` metadata
   field case-insensitively with missing titles last; `Shortest`/`Longest` read
   `duration` in seconds with missing durations last. `DateSaved` reads the
   querying user's save timestamp and therefore requires `for_user`.
3. **Live content.** A `viewer_count` signal (short half-life, no windows, no
   velocity — it represents a current concurrent count, not an accumulation) plus
   a `live` built-in profile sorting on `LiveViewerCount`
   (`tidal/src/ranking/builtins.rs`).
4. **Engagement and geographic filters.** `FilterExpr::MinSignal` /
   `MaxSignal` evaluate an AllTime windowed count against a threshold;
   `FilterExpr::NearLocation { lat, lng, radius_km }` is a Haversine post-filter
   over item `latitude`/`longitude` metadata — deliberately not index-backed.

## Evidence

- `tidal/tests/m6p3_sorts.rs` (9), `m6p3_filters.rs` (3),
  `m6p3_edge_cases.rs` (3) — integration coverage.
- `tidal/src/ranking/executor/tests/sort_tests.rs` — per-variant ordering unit
  tests, the "at least one test per Sort variant" criterion.
- `tidal/benches/sort.rs` — sort benchmarks added by the same commit.

## Note on the "< 50 ms at 500 items" criterion

Marked `[x]`; `tidal/benches/sort.rs` exists and targets it, but no run is
recorded in `docs/`. Measurable on demand (`cargo bench -p tidaldb --bench
sort`); not currently evidenced.